Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next

[sfrench/cifs-2.6.git] / kernel / bpf / verifier.c

// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
 * Copyright (c) 2016 Facebook
 * Copyright (c) 2018 Covalent IO, Inc. http://covalent.io
 */
#include <uapi/linux/btf.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/bpf.h>
#include <linux/btf.h>
#include <linux/bpf_verifier.h>
#include <linux/filter.h>
#include <net/netlink.h>
#include <linux/file.h>
#include <linux/vmalloc.h>
#include <linux/stringify.h>
#include <linux/bsearch.h>
#include <linux/sort.h>
#include <linux/perf_event.h>
#include <linux/ctype.h>
#include <linux/error-injection.h>
#include <linux/bpf_lsm.h>
#include <linux/btf_ids.h>

#include "disasm.h"

static const struct bpf_verifier_ops * const bpf_verifier_ops[] = {
#define BPF_PROG_TYPE(_id, _name, prog_ctx_type, kern_ctx_type) \
        [_id] = & _name ## _verifier_ops,
#define BPF_MAP_TYPE(_id, _ops)
#define BPF_LINK_TYPE(_id, _name)
#include <linux/bpf_types.h>
#undef BPF_PROG_TYPE
#undef BPF_MAP_TYPE
#undef BPF_LINK_TYPE
};

/* bpf_check() is a static code analyzer that walks eBPF program
 * instruction by instruction and updates register/stack state.
 * All paths of conditional branches are analyzed until 'bpf_exit' insn.
 *
 * The first pass is depth-first-search to check that the program is a DAG.
 * It rejects the following programs:
 * - larger than BPF_MAXINSNS insns
 * - if loop is present (detected via back-edge)
 * - unreachable insns exist (shouldn't be a forest. program = one function)
 * - out of bounds or malformed jumps
 * The second pass is all possible path descent from the 1st insn.
 * Since it's analyzing all pathes through the program, the length of the
 * analysis is limited to 64k insn, which may be hit even if total number of
 * insn is less then 4K, but there are too many branches that change stack/regs.
 * Number of 'branches to be analyzed' is limited to 1k
 *
 * On entry to each instruction, each register has a type, and the instruction
 * changes the types of the registers depending on instruction semantics.
 * If instruction is BPF_MOV64_REG(BPF_REG_1, BPF_REG_5), then type of R5 is
 * copied to R1.
 *
 * All registers are 64-bit.
 * R0 - return register
 * R1-R5 argument passing registers
 * R6-R9 callee saved registers
 * R10 - frame pointer read-only
 *
 * At the start of BPF program the register R1 contains a pointer to bpf_context
 * and has type PTR_TO_CTX.
 *
 * Verifier tracks arithmetic operations on pointers in case:
 *    BPF_MOV64_REG(BPF_REG_1, BPF_REG_10),
 *    BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -20),
 * 1st insn copies R10 (which has FRAME_PTR) type into R1
 * and 2nd arithmetic instruction is pattern matched to recognize
 * that it wants to construct a pointer to some element within stack.
 * So after 2nd insn, the register R1 has type PTR_TO_STACK
 * (and -20 constant is saved for further stack bounds checking).
 * Meaning that this reg is a pointer to stack plus known immediate constant.
 *
 * Most of the time the registers have SCALAR_VALUE type, which
 * means the register has some value, but it's not a valid pointer.
 * (like pointer plus pointer becomes SCALAR_VALUE type)
 *
 * When verifier sees load or store instructions the type of base register
 * can be: PTR_TO_MAP_VALUE, PTR_TO_CTX, PTR_TO_STACK, PTR_TO_SOCKET. These are
 * four pointer types recognized by check_mem_access() function.
 *
 * PTR_TO_MAP_VALUE means that this register is pointing to 'map element value'
 * and the range of [ptr, ptr + map's value_size) is accessible.
 *
 * registers used to pass values to function calls are checked against
 * function argument constraints.
 *
 * ARG_PTR_TO_MAP_KEY is one of such argument constraints.
 * It means that the register type passed to this function must be
 * PTR_TO_STACK and it will be used inside the function as
 * 'pointer to map element key'
 *
 * For example the argument constraints for bpf_map_lookup_elem():
 *   .ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
 *   .arg1_type = ARG_CONST_MAP_PTR,
 *   .arg2_type = ARG_PTR_TO_MAP_KEY,
 *
 * ret_type says that this function returns 'pointer to map elem value or null'
 * function expects 1st argument to be a const pointer to 'struct bpf_map' and
 * 2nd argument should be a pointer to stack, which will be used inside
 * the helper function as a pointer to map element key.
 *
 * On the kernel side the helper function looks like:
 * u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 * {
 *    struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
 *    void *key = (void *) (unsigned long) r2;
 *    void *value;
 *
 *    here kernel can access 'key' and 'map' pointers safely, knowing that
 *    [key, key + map->key_size) bytes are valid and were initialized on
 *    the stack of eBPF program.
 * }
 *
 * Corresponding eBPF program may look like:
 *    BPF_MOV64_REG(BPF_REG_2, BPF_REG_10),  // after this insn R2 type is FRAME_PTR
 *    BPF_ALU64_IMM(BPF_ADD, BPF_REG_2, -4), // after this insn R2 type is PTR_TO_STACK
 *    BPF_LD_MAP_FD(BPF_REG_1, map_fd),      // after this insn R1 type is CONST_PTR_TO_MAP
 *    BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_map_lookup_elem),
 * here verifier looks at prototype of map_lookup_elem() and sees:
 * .arg1_type == ARG_CONST_MAP_PTR and R1->type == CONST_PTR_TO_MAP, which is ok,
 * Now verifier knows that this map has key of R1->map_ptr->key_size bytes
 *
 * Then .arg2_type == ARG_PTR_TO_MAP_KEY and R2->type == PTR_TO_STACK, ok so far,
 * Now verifier checks that [R2, R2 + map's key_size) are within stack limits
 * and were initialized prior to this call.
 * If it's ok, then verifier allows this BPF_CALL insn and looks at
 * .ret_type which is RET_PTR_TO_MAP_VALUE_OR_NULL, so it sets
 * R0->type = PTR_TO_MAP_VALUE_OR_NULL which means bpf_map_lookup_elem() function
 * returns ether pointer to map value or NULL.
 *
 * When type PTR_TO_MAP_VALUE_OR_NULL passes through 'if (reg != 0) goto +off'
 * insn, the register holding that pointer in the true branch changes state to
 * PTR_TO_MAP_VALUE and the same register changes state to CONST_IMM in the false
 * branch. See check_cond_jmp_op().
 *
 * After the call R0 is set to return type of the function and registers R1-R5
 * are set to NOT_INIT to indicate that they are no longer readable.
 *
 * The following reference types represent a potential reference to a kernel
 * resource which, after first being allocated, must be checked and freed by
 * the BPF program:
 * - PTR_TO_SOCKET_OR_NULL, PTR_TO_SOCKET
 *
 * When the verifier sees a helper call return a reference type, it allocates a
 * pointer id for the reference and stores it in the current function state.
 * Similar to the way that PTR_TO_MAP_VALUE_OR_NULL is converted into
 * PTR_TO_MAP_VALUE, PTR_TO_SOCKET_OR_NULL becomes PTR_TO_SOCKET when the type
 * passes through a NULL-check conditional. For the branch wherein the state is
 * changed to CONST_IMM, the verifier releases the reference.
 *
 * For each helper function that allocates a reference, such as
 * bpf_sk_lookup_tcp(), there is a corresponding release function, such as
 * bpf_sk_release(). When a reference type passes into the release function,
 * the verifier also releases the reference. If any unchecked or unreleased
 * reference remains at the end of the program, the verifier rejects it.
 */

/* verifier_state + insn_idx are pushed to stack when branch is encountered */
struct bpf_verifier_stack_elem {
        /* verifer state is 'st'
         * before processing instruction 'insn_idx'
         * and after processing instruction 'prev_insn_idx'
         */
        struct bpf_verifier_state st;
        int insn_idx;
        int prev_insn_idx;
        struct bpf_verifier_stack_elem *next;
        /* length of verifier log at the time this state was pushed on stack */
        u32 log_pos;
};

#define BPF_COMPLEXITY_LIMIT_JMP_SEQ    8192
#define BPF_COMPLEXITY_LIMIT_STATES     64

#define BPF_MAP_KEY_POISON      (1ULL << 63)
#define BPF_MAP_KEY_SEEN        (1ULL << 62)

#define BPF_MAP_PTR_UNPRIV      1UL
#define BPF_MAP_PTR_POISON      ((void *)((0xeB9FUL << 1) +     \
                                          POISON_POINTER_DELTA))
#define BPF_MAP_PTR(X)          ((struct bpf_map *)((X) & ~BPF_MAP_PTR_UNPRIV))

static bool bpf_map_ptr_poisoned(const struct bpf_insn_aux_data *aux)
{
        return BPF_MAP_PTR(aux->map_ptr_state) == BPF_MAP_PTR_POISON;
}

static bool bpf_map_ptr_unpriv(const struct bpf_insn_aux_data *aux)
{
        return aux->map_ptr_state & BPF_MAP_PTR_UNPRIV;
}

static void bpf_map_ptr_store(struct bpf_insn_aux_data *aux,
                              const struct bpf_map *map, bool unpriv)
{
        BUILD_BUG_ON((unsigned long)BPF_MAP_PTR_POISON & BPF_MAP_PTR_UNPRIV);
        unpriv |= bpf_map_ptr_unpriv(aux);
        aux->map_ptr_state = (unsigned long)map |
                             (unpriv ? BPF_MAP_PTR_UNPRIV : 0UL);
}

static bool bpf_map_key_poisoned(const struct bpf_insn_aux_data *aux)
{
        return aux->map_key_state & BPF_MAP_KEY_POISON;
}

static bool bpf_map_key_unseen(const struct bpf_insn_aux_data *aux)
{
        return !(aux->map_key_state & BPF_MAP_KEY_SEEN);
}

static u64 bpf_map_key_immediate(const struct bpf_insn_aux_data *aux)
{
        return aux->map_key_state & ~(BPF_MAP_KEY_SEEN | BPF_MAP_KEY_POISON);
}

static void bpf_map_key_store(struct bpf_insn_aux_data *aux, u64 state)
{
        bool poisoned = bpf_map_key_poisoned(aux);

        aux->map_key_state = state | BPF_MAP_KEY_SEEN |
                             (poisoned ? BPF_MAP_KEY_POISON : 0ULL);
}

static bool bpf_pseudo_call(const struct bpf_insn *insn)
{
        return insn->code == (BPF_JMP | BPF_CALL) &&
               insn->src_reg == BPF_PSEUDO_CALL;
}

static bool bpf_pseudo_func(const struct bpf_insn *insn)
{
        return insn->code == (BPF_LD | BPF_IMM | BPF_DW) &&
               insn->src_reg == BPF_PSEUDO_FUNC;
}

struct bpf_call_arg_meta {
        struct bpf_map *map_ptr;
        bool raw_mode;
        bool pkt_access;
        int regno;
        int access_size;
        int mem_size;
        u64 msize_max_value;
        int ref_obj_id;
        int func_id;
        struct btf *btf;
        u32 btf_id;
        struct btf *ret_btf;
        u32 ret_btf_id;
        u32 subprogno;
};

struct btf *btf_vmlinux;

static DEFINE_MUTEX(bpf_verifier_lock);

static const struct bpf_line_info *
find_linfo(const struct bpf_verifier_env *env, u32 insn_off)
{
        const struct bpf_line_info *linfo;
        const struct bpf_prog *prog;
        u32 i, nr_linfo;

        prog = env->prog;
        nr_linfo = prog->aux->nr_linfo;

        if (!nr_linfo || insn_off >= prog->len)
                return NULL;

        linfo = prog->aux->linfo;
        for (i = 1; i < nr_linfo; i++)
                if (insn_off < linfo[i].insn_off)
                        break;

        return &linfo[i - 1];
}

void bpf_verifier_vlog(struct bpf_verifier_log *log, const char *fmt,
                       va_list args)
{
        unsigned int n;

        n = vscnprintf(log->kbuf, BPF_VERIFIER_TMP_LOG_SIZE, fmt, args);

        WARN_ONCE(n >= BPF_VERIFIER_TMP_LOG_SIZE - 1,
                  "verifier log line truncated - local buffer too short\n");

        n = min(log->len_total - log->len_used - 1, n);
        log->kbuf[n] = '\0';

        if (log->level == BPF_LOG_KERNEL) {
                pr_err("BPF:%s\n", log->kbuf);
                return;
        }
        if (!copy_to_user(log->ubuf + log->len_used, log->kbuf, n + 1))
                log->len_used += n;
        else
                log->ubuf = NULL;
}

static void bpf_vlog_reset(struct bpf_verifier_log *log, u32 new_pos)
{
        char zero = 0;

        if (!bpf_verifier_log_needed(log))
                return;

        log->len_used = new_pos;
        if (put_user(zero, log->ubuf + new_pos))
                log->ubuf = NULL;
}

/* log_level controls verbosity level of eBPF verifier.
 * bpf_verifier_log_write() is used to dump the verification trace to the log,
 * so the user can figure out what's wrong with the program
 */
__printf(2, 3) void bpf_verifier_log_write(struct bpf_verifier_env *env,
                                           const char *fmt, ...)
{
        va_list args;

        if (!bpf_verifier_log_needed(&env->log))
                return;

        va_start(args, fmt);
        bpf_verifier_vlog(&env->log, fmt, args);
        va_end(args);
}
EXPORT_SYMBOL_GPL(bpf_verifier_log_write);

__printf(2, 3) static void verbose(void *private_data, const char *fmt, ...)
{
        struct bpf_verifier_env *env = private_data;
        va_list args;

        if (!bpf_verifier_log_needed(&env->log))
                return;

        va_start(args, fmt);
        bpf_verifier_vlog(&env->log, fmt, args);
        va_end(args);
}

__printf(2, 3) void bpf_log(struct bpf_verifier_log *log,
                            const char *fmt, ...)
{
        va_list args;

        if (!bpf_verifier_log_needed(log))
                return;

        va_start(args, fmt);
        bpf_verifier_vlog(log, fmt, args);
        va_end(args);
}

static const char *ltrim(const char *s)
{
        while (isspace(*s))
                s++;

        return s;
}

__printf(3, 4) static void verbose_linfo(struct bpf_verifier_env *env,
                                         u32 insn_off,
                                         const char *prefix_fmt, ...)
{
        const struct bpf_line_info *linfo;

        if (!bpf_verifier_log_needed(&env->log))
                return;

        linfo = find_linfo(env, insn_off);
        if (!linfo || linfo == env->prev_linfo)
                return;

        if (prefix_fmt) {
                va_list args;

                va_start(args, prefix_fmt);
                bpf_verifier_vlog(&env->log, prefix_fmt, args);
                va_end(args);
        }

        verbose(env, "%s\n",
                ltrim(btf_name_by_offset(env->prog->aux->btf,
                                         linfo->line_off)));

        env->prev_linfo = linfo;
}

static void verbose_invalid_scalar(struct bpf_verifier_env *env,
                                   struct bpf_reg_state *reg,
                                   struct tnum *range, const char *ctx,
                                   const char *reg_name)
{
        char tn_buf[48];

        verbose(env, "At %s the register %s ", ctx, reg_name);
        if (!tnum_is_unknown(reg->var_off)) {
                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "has value %s", tn_buf);
        } else {
                verbose(env, "has unknown scalar value");
        }
        tnum_strn(tn_buf, sizeof(tn_buf), *range);
        verbose(env, " should have been in %s\n", tn_buf);
}

static bool type_is_pkt_pointer(enum bpf_reg_type type)
{
        return type == PTR_TO_PACKET ||
               type == PTR_TO_PACKET_META;
}

static bool type_is_sk_pointer(enum bpf_reg_type type)
{
        return type == PTR_TO_SOCKET ||
                type == PTR_TO_SOCK_COMMON ||
                type == PTR_TO_TCP_SOCK ||
                type == PTR_TO_XDP_SOCK;
}

static bool reg_type_not_null(enum bpf_reg_type type)
{
        return type == PTR_TO_SOCKET ||
                type == PTR_TO_TCP_SOCK ||
                type == PTR_TO_MAP_VALUE ||
                type == PTR_TO_MAP_KEY ||
                type == PTR_TO_SOCK_COMMON;
}

static bool reg_type_may_be_null(enum bpf_reg_type type)
{
        return type == PTR_TO_MAP_VALUE_OR_NULL ||
               type == PTR_TO_SOCKET_OR_NULL ||
               type == PTR_TO_SOCK_COMMON_OR_NULL ||
               type == PTR_TO_TCP_SOCK_OR_NULL ||
               type == PTR_TO_BTF_ID_OR_NULL ||
               type == PTR_TO_MEM_OR_NULL ||
               type == PTR_TO_RDONLY_BUF_OR_NULL ||
               type == PTR_TO_RDWR_BUF_OR_NULL;
}

static bool reg_may_point_to_spin_lock(const struct bpf_reg_state *reg)
{
        return reg->type == PTR_TO_MAP_VALUE &&
                map_value_has_spin_lock(reg->map_ptr);
}

static bool reg_type_may_be_refcounted_or_null(enum bpf_reg_type type)
{
        return type == PTR_TO_SOCKET ||
                type == PTR_TO_SOCKET_OR_NULL ||
                type == PTR_TO_TCP_SOCK ||
                type == PTR_TO_TCP_SOCK_OR_NULL ||
                type == PTR_TO_MEM ||
                type == PTR_TO_MEM_OR_NULL;
}

static bool arg_type_may_be_refcounted(enum bpf_arg_type type)
{
        return type == ARG_PTR_TO_SOCK_COMMON;
}

static bool arg_type_may_be_null(enum bpf_arg_type type)
{
        return type == ARG_PTR_TO_MAP_VALUE_OR_NULL ||
               type == ARG_PTR_TO_MEM_OR_NULL ||
               type == ARG_PTR_TO_CTX_OR_NULL ||
               type == ARG_PTR_TO_SOCKET_OR_NULL ||
               type == ARG_PTR_TO_ALLOC_MEM_OR_NULL ||
               type == ARG_PTR_TO_STACK_OR_NULL;
}

/* Determine whether the function releases some resources allocated by another
 * function call. The first reference type argument will be assumed to be
 * released by release_reference().
 */
static bool is_release_function(enum bpf_func_id func_id)
{
        return func_id == BPF_FUNC_sk_release ||
               func_id == BPF_FUNC_ringbuf_submit ||
               func_id == BPF_FUNC_ringbuf_discard;
}

static bool may_be_acquire_function(enum bpf_func_id func_id)
{
        return func_id == BPF_FUNC_sk_lookup_tcp ||
                func_id == BPF_FUNC_sk_lookup_udp ||
                func_id == BPF_FUNC_skc_lookup_tcp ||
                func_id == BPF_FUNC_map_lookup_elem ||
                func_id == BPF_FUNC_ringbuf_reserve;
}

static bool is_acquire_function(enum bpf_func_id func_id,
                                const struct bpf_map *map)
{
        enum bpf_map_type map_type = map ? map->map_type : BPF_MAP_TYPE_UNSPEC;

        if (func_id == BPF_FUNC_sk_lookup_tcp ||
            func_id == BPF_FUNC_sk_lookup_udp ||
            func_id == BPF_FUNC_skc_lookup_tcp ||
            func_id == BPF_FUNC_ringbuf_reserve)
                return true;

        if (func_id == BPF_FUNC_map_lookup_elem &&
            (map_type == BPF_MAP_TYPE_SOCKMAP ||
             map_type == BPF_MAP_TYPE_SOCKHASH))
                return true;

        return false;
}

static bool is_ptr_cast_function(enum bpf_func_id func_id)
{
        return func_id == BPF_FUNC_tcp_sock ||
                func_id == BPF_FUNC_sk_fullsock ||
                func_id == BPF_FUNC_skc_to_tcp_sock ||
                func_id == BPF_FUNC_skc_to_tcp6_sock ||
                func_id == BPF_FUNC_skc_to_udp6_sock ||
                func_id == BPF_FUNC_skc_to_tcp_timewait_sock ||
                func_id == BPF_FUNC_skc_to_tcp_request_sock;
}

static bool is_cmpxchg_insn(const struct bpf_insn *insn)
{
        return BPF_CLASS(insn->code) == BPF_STX &&
               BPF_MODE(insn->code) == BPF_ATOMIC &&
               insn->imm == BPF_CMPXCHG;
}

/* string representation of 'enum bpf_reg_type' */
static const char * const reg_type_str[] = {
        [NOT_INIT]              = "?",
        [SCALAR_VALUE]          = "inv",
        [PTR_TO_CTX]            = "ctx",
        [CONST_PTR_TO_MAP]      = "map_ptr",
        [PTR_TO_MAP_VALUE]      = "map_value",
        [PTR_TO_MAP_VALUE_OR_NULL] = "map_value_or_null",
        [PTR_TO_STACK]          = "fp",
        [PTR_TO_PACKET]         = "pkt",
        [PTR_TO_PACKET_META]    = "pkt_meta",
        [PTR_TO_PACKET_END]     = "pkt_end",
        [PTR_TO_FLOW_KEYS]      = "flow_keys",
        [PTR_TO_SOCKET]         = "sock",
        [PTR_TO_SOCKET_OR_NULL] = "sock_or_null",
        [PTR_TO_SOCK_COMMON]    = "sock_common",
        [PTR_TO_SOCK_COMMON_OR_NULL] = "sock_common_or_null",
        [PTR_TO_TCP_SOCK]       = "tcp_sock",
        [PTR_TO_TCP_SOCK_OR_NULL] = "tcp_sock_or_null",
        [PTR_TO_TP_BUFFER]      = "tp_buffer",
        [PTR_TO_XDP_SOCK]       = "xdp_sock",
        [PTR_TO_BTF_ID]         = "ptr_",
        [PTR_TO_BTF_ID_OR_NULL] = "ptr_or_null_",
        [PTR_TO_PERCPU_BTF_ID]  = "percpu_ptr_",
        [PTR_TO_MEM]            = "mem",
        [PTR_TO_MEM_OR_NULL]    = "mem_or_null",
        [PTR_TO_RDONLY_BUF]     = "rdonly_buf",
        [PTR_TO_RDONLY_BUF_OR_NULL] = "rdonly_buf_or_null",
        [PTR_TO_RDWR_BUF]       = "rdwr_buf",
        [PTR_TO_RDWR_BUF_OR_NULL] = "rdwr_buf_or_null",
        [PTR_TO_FUNC]           = "func",
        [PTR_TO_MAP_KEY]        = "map_key",
};

static char slot_type_char[] = {
        [STACK_INVALID] = '?',
        [STACK_SPILL]   = 'r',
        [STACK_MISC]    = 'm',
        [STACK_ZERO]    = '0',
};

static void print_liveness(struct bpf_verifier_env *env,
                           enum bpf_reg_liveness live)
{
        if (live & (REG_LIVE_READ | REG_LIVE_WRITTEN | REG_LIVE_DONE))
            verbose(env, "_");
        if (live & REG_LIVE_READ)
                verbose(env, "r");
        if (live & REG_LIVE_WRITTEN)
                verbose(env, "w");
        if (live & REG_LIVE_DONE)
                verbose(env, "D");
}

static struct bpf_func_state *func(struct bpf_verifier_env *env,
                                   const struct bpf_reg_state *reg)
{
        struct bpf_verifier_state *cur = env->cur_state;

        return cur->frame[reg->frameno];
}

static const char *kernel_type_name(const struct btf* btf, u32 id)
{
        return btf_name_by_offset(btf, btf_type_by_id(btf, id)->name_off);
}

static void print_verifier_state(struct bpf_verifier_env *env,
                                 const struct bpf_func_state *state)
{
        const struct bpf_reg_state *reg;
        enum bpf_reg_type t;
        int i;

        if (state->frameno)
                verbose(env, " frame%d:", state->frameno);
        for (i = 0; i < MAX_BPF_REG; i++) {
                reg = &state->regs[i];
                t = reg->type;
                if (t == NOT_INIT)
                        continue;
                verbose(env, " R%d", i);
                print_liveness(env, reg->live);
                verbose(env, "=%s", reg_type_str[t]);
                if (t == SCALAR_VALUE && reg->precise)
                        verbose(env, "P");
                if ((t == SCALAR_VALUE || t == PTR_TO_STACK) &&
                    tnum_is_const(reg->var_off)) {
                        /* reg->off should be 0 for SCALAR_VALUE */
                        verbose(env, "%lld", reg->var_off.value + reg->off);
                } else {
                        if (t == PTR_TO_BTF_ID ||
                            t == PTR_TO_BTF_ID_OR_NULL ||
                            t == PTR_TO_PERCPU_BTF_ID)
                                verbose(env, "%s", kernel_type_name(reg->btf, reg->btf_id));
                        verbose(env, "(id=%d", reg->id);
                        if (reg_type_may_be_refcounted_or_null(t))
                                verbose(env, ",ref_obj_id=%d", reg->ref_obj_id);
                        if (t != SCALAR_VALUE)
                                verbose(env, ",off=%d", reg->off);
                        if (type_is_pkt_pointer(t))
                                verbose(env, ",r=%d", reg->range);
                        else if (t == CONST_PTR_TO_MAP ||
                                 t == PTR_TO_MAP_KEY ||
                                 t == PTR_TO_MAP_VALUE ||
                                 t == PTR_TO_MAP_VALUE_OR_NULL)
                                verbose(env, ",ks=%d,vs=%d",
                                        reg->map_ptr->key_size,
                                        reg->map_ptr->value_size);
                        if (tnum_is_const(reg->var_off)) {
                                /* Typically an immediate SCALAR_VALUE, but
                                 * could be a pointer whose offset is too big
                                 * for reg->off
                                 */
                                verbose(env, ",imm=%llx", reg->var_off.value);
                        } else {
                                if (reg->smin_value != reg->umin_value &&
                                    reg->smin_value != S64_MIN)
                                        verbose(env, ",smin_value=%lld",
                                                (long long)reg->smin_value);
                                if (reg->smax_value != reg->umax_value &&
                                    reg->smax_value != S64_MAX)
                                        verbose(env, ",smax_value=%lld",
                                                (long long)reg->smax_value);
                                if (reg->umin_value != 0)
                                        verbose(env, ",umin_value=%llu",
                                                (unsigned long long)reg->umin_value);
                                if (reg->umax_value != U64_MAX)
                                        verbose(env, ",umax_value=%llu",
                                                (unsigned long long)reg->umax_value);
                                if (!tnum_is_unknown(reg->var_off)) {
                                        char tn_buf[48];

                                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                                        verbose(env, ",var_off=%s", tn_buf);
                                }
                                if (reg->s32_min_value != reg->smin_value &&
                                    reg->s32_min_value != S32_MIN)
                                        verbose(env, ",s32_min_value=%d",
                                                (int)(reg->s32_min_value));
                                if (reg->s32_max_value != reg->smax_value &&
                                    reg->s32_max_value != S32_MAX)
                                        verbose(env, ",s32_max_value=%d",
                                                (int)(reg->s32_max_value));
                                if (reg->u32_min_value != reg->umin_value &&
                                    reg->u32_min_value != U32_MIN)
                                        verbose(env, ",u32_min_value=%d",
                                                (int)(reg->u32_min_value));
                                if (reg->u32_max_value != reg->umax_value &&
                                    reg->u32_max_value != U32_MAX)
                                        verbose(env, ",u32_max_value=%d",
                                                (int)(reg->u32_max_value));
                        }
                        verbose(env, ")");
                }
        }
        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                char types_buf[BPF_REG_SIZE + 1];
                bool valid = false;
                int j;

                for (j = 0; j < BPF_REG_SIZE; j++) {
                        if (state->stack[i].slot_type[j] != STACK_INVALID)
                                valid = true;
                        types_buf[j] = slot_type_char[
                                        state->stack[i].slot_type[j]];
                }
                types_buf[BPF_REG_SIZE] = 0;
                if (!valid)
                        continue;
                verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
                print_liveness(env, state->stack[i].spilled_ptr.live);
                if (state->stack[i].slot_type[0] == STACK_SPILL) {
                        reg = &state->stack[i].spilled_ptr;
                        t = reg->type;
                        verbose(env, "=%s", reg_type_str[t]);
                        if (t == SCALAR_VALUE && reg->precise)
                                verbose(env, "P");
                        if (t == SCALAR_VALUE && tnum_is_const(reg->var_off))
                                verbose(env, "%lld", reg->var_off.value + reg->off);
                } else {
                        verbose(env, "=%s", types_buf);
                }
        }
        if (state->acquired_refs && state->refs[0].id) {
                verbose(env, " refs=%d", state->refs[0].id);
                for (i = 1; i < state->acquired_refs; i++)
                        if (state->refs[i].id)
                                verbose(env, ",%d", state->refs[i].id);
        }
        verbose(env, "\n");
}

#define COPY_STATE_FN(NAME, COUNT, FIELD, SIZE)                         \
static int copy_##NAME##_state(struct bpf_func_state *dst,              \
                               const struct bpf_func_state *src)        \
{                                                                       \
        if (!src->FIELD)                                                \
                return 0;                                               \
        if (WARN_ON_ONCE(dst->COUNT < src->COUNT)) {                    \
                /* internal bug, make state invalid to reject the program */ \
                memset(dst, 0, sizeof(*dst));                           \
                return -EFAULT;                                         \
        }                                                               \
        memcpy(dst->FIELD, src->FIELD,                                  \
               sizeof(*src->FIELD) * (src->COUNT / SIZE));              \
        return 0;                                                       \
}
/* copy_reference_state() */
COPY_STATE_FN(reference, acquired_refs, refs, 1)
/* copy_stack_state() */
COPY_STATE_FN(stack, allocated_stack, stack, BPF_REG_SIZE)
#undef COPY_STATE_FN

#define REALLOC_STATE_FN(NAME, COUNT, FIELD, SIZE)                      \
static int realloc_##NAME##_state(struct bpf_func_state *state, int size, \
                                  bool copy_old)                        \
{                                                                       \
        u32 old_size = state->COUNT;                                    \
        struct bpf_##NAME##_state *new_##FIELD;                         \
        int slot = size / SIZE;                                         \
                                                                        \
        if (size <= old_size || !size) {                                \
                if (copy_old)                                           \
                        return 0;                                       \
                state->COUNT = slot * SIZE;                             \
                if (!size && old_size) {                                \
                        kfree(state->FIELD);                            \
                        state->FIELD = NULL;                            \
                }                                                       \
                return 0;                                               \
        }                                                               \
        new_##FIELD = kmalloc_array(slot, sizeof(struct bpf_##NAME##_state), \
                                    GFP_KERNEL);                        \
        if (!new_##FIELD)                                               \
                return -ENOMEM;                                         \
        if (copy_old) {                                                 \
                if (state->FIELD)                                       \
                        memcpy(new_##FIELD, state->FIELD,               \
                               sizeof(*new_##FIELD) * (old_size / SIZE)); \
                memset(new_##FIELD + old_size / SIZE, 0,                \
                       sizeof(*new_##FIELD) * (size - old_size) / SIZE); \
        }                                                               \
        state->COUNT = slot * SIZE;                                     \
        kfree(state->FIELD);                                            \
        state->FIELD = new_##FIELD;                                     \
        return 0;                                                       \
}
/* realloc_reference_state() */
REALLOC_STATE_FN(reference, acquired_refs, refs, 1)
/* realloc_stack_state() */
REALLOC_STATE_FN(stack, allocated_stack, stack, BPF_REG_SIZE)
#undef REALLOC_STATE_FN

/* do_check() starts with zero-sized stack in struct bpf_verifier_state to
 * make it consume minimal amount of memory. check_stack_write() access from
 * the program calls into realloc_func_state() to grow the stack size.
 * Note there is a non-zero 'parent' pointer inside bpf_verifier_state
 * which realloc_stack_state() copies over. It points to previous
 * bpf_verifier_state which is never reallocated.
 */
static int realloc_func_state(struct bpf_func_state *state, int stack_size,
                              int refs_size, bool copy_old)
{
        int err = realloc_reference_state(state, refs_size, copy_old);
        if (err)
                return err;
        return realloc_stack_state(state, stack_size, copy_old);
}

/* Acquire a pointer id from the env and update the state->refs to include
 * this new pointer reference.
 * On success, returns a valid pointer id to associate with the register
 * On failure, returns a negative errno.
 */
static int acquire_reference_state(struct bpf_verifier_env *env, int insn_idx)
{
        struct bpf_func_state *state = cur_func(env);
        int new_ofs = state->acquired_refs;
        int id, err;

        err = realloc_reference_state(state, state->acquired_refs + 1, true);
        if (err)
                return err;
        id = ++env->id_gen;
        state->refs[new_ofs].id = id;
        state->refs[new_ofs].insn_idx = insn_idx;

        return id;
}

/* release function corresponding to acquire_reference_state(). Idempotent. */
static int release_reference_state(struct bpf_func_state *state, int ptr_id)
{
        int i, last_idx;

        last_idx = state->acquired_refs - 1;
        for (i = 0; i < state->acquired_refs; i++) {
                if (state->refs[i].id == ptr_id) {
                        if (last_idx && i != last_idx)
                                memcpy(&state->refs[i], &state->refs[last_idx],
                                       sizeof(*state->refs));
                        memset(&state->refs[last_idx], 0, sizeof(*state->refs));
                        state->acquired_refs--;
                        return 0;
                }
        }
        return -EINVAL;
}

static int transfer_reference_state(struct bpf_func_state *dst,
                                    struct bpf_func_state *src)
{
        int err = realloc_reference_state(dst, src->acquired_refs, false);
        if (err)
                return err;
        err = copy_reference_state(dst, src);
        if (err)
                return err;
        return 0;
}

static void free_func_state(struct bpf_func_state *state)
{
        if (!state)
                return;
        kfree(state->refs);
        kfree(state->stack);
        kfree(state);
}

static void clear_jmp_history(struct bpf_verifier_state *state)
{
        kfree(state->jmp_history);
        state->jmp_history = NULL;
        state->jmp_history_cnt = 0;
}

static void free_verifier_state(struct bpf_verifier_state *state,
                                bool free_self)
{
        int i;

        for (i = 0; i <= state->curframe; i++) {
                free_func_state(state->frame[i]);
                state->frame[i] = NULL;
        }
        clear_jmp_history(state);
        if (free_self)
                kfree(state);
}

/* copy verifier state from src to dst growing dst stack space
 * when necessary to accommodate larger src stack
 */
static int copy_func_state(struct bpf_func_state *dst,
                           const struct bpf_func_state *src)
{
        int err;

        err = realloc_func_state(dst, src->allocated_stack, src->acquired_refs,
                                 false);
        if (err)
                return err;
        memcpy(dst, src, offsetof(struct bpf_func_state, acquired_refs));
        err = copy_reference_state(dst, src);
        if (err)
                return err;
        return copy_stack_state(dst, src);
}

static int copy_verifier_state(struct bpf_verifier_state *dst_state,
                               const struct bpf_verifier_state *src)
{
        struct bpf_func_state *dst;
        u32 jmp_sz = sizeof(struct bpf_idx_pair) * src->jmp_history_cnt;
        int i, err;

        if (dst_state->jmp_history_cnt < src->jmp_history_cnt) {
                kfree(dst_state->jmp_history);
                dst_state->jmp_history = kmalloc(jmp_sz, GFP_USER);
                if (!dst_state->jmp_history)
                        return -ENOMEM;
        }
        memcpy(dst_state->jmp_history, src->jmp_history, jmp_sz);
        dst_state->jmp_history_cnt = src->jmp_history_cnt;

        /* if dst has more stack frames then src frame, free them */
        for (i = src->curframe + 1; i <= dst_state->curframe; i++) {
                free_func_state(dst_state->frame[i]);
                dst_state->frame[i] = NULL;
        }
        dst_state->speculative = src->speculative;
        dst_state->curframe = src->curframe;
        dst_state->active_spin_lock = src->active_spin_lock;
        dst_state->branches = src->branches;
        dst_state->parent = src->parent;
        dst_state->first_insn_idx = src->first_insn_idx;
        dst_state->last_insn_idx = src->last_insn_idx;
        for (i = 0; i <= src->curframe; i++) {
                dst = dst_state->frame[i];
                if (!dst) {
                        dst = kzalloc(sizeof(*dst), GFP_KERNEL);
                        if (!dst)
                                return -ENOMEM;
                        dst_state->frame[i] = dst;
                }
                err = copy_func_state(dst, src->frame[i]);
                if (err)
                        return err;
        }
        return 0;
}

static void update_branch_counts(struct bpf_verifier_env *env, struct bpf_verifier_state *st)
{
        while (st) {
                u32 br = --st->branches;

                /* WARN_ON(br > 1) technically makes sense here,
                 * but see comment in push_stack(), hence:
                 */
                WARN_ONCE((int)br < 0,
                          "BUG update_branch_counts:branches_to_explore=%d\n",
                          br);
                if (br)
                        break;
                st = st->parent;
        }
}

static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx,
                     int *insn_idx, bool pop_log)
{
        struct bpf_verifier_state *cur = env->cur_state;
        struct bpf_verifier_stack_elem *elem, *head = env->head;
        int err;

        if (env->head == NULL)
                return -ENOENT;

        if (cur) {
                err = copy_verifier_state(cur, &head->st);
                if (err)
                        return err;
        }
        if (pop_log)
                bpf_vlog_reset(&env->log, head->log_pos);
        if (insn_idx)
                *insn_idx = head->insn_idx;
        if (prev_insn_idx)
                *prev_insn_idx = head->prev_insn_idx;
        elem = head->next;
        free_verifier_state(&head->st, false);
        kfree(head);
        env->head = elem;
        env->stack_size--;
        return 0;
}

static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
                                             int insn_idx, int prev_insn_idx,
                                             bool speculative)
{
        struct bpf_verifier_state *cur = env->cur_state;
        struct bpf_verifier_stack_elem *elem;
        int err;

        elem = kzalloc(sizeof(struct bpf_verifier_stack_elem), GFP_KERNEL);
        if (!elem)
                goto err;

        elem->insn_idx = insn_idx;
        elem->prev_insn_idx = prev_insn_idx;
        elem->next = env->head;
        elem->log_pos = env->log.len_used;
        env->head = elem;
        env->stack_size++;
        err = copy_verifier_state(&elem->st, cur);
        if (err)
                goto err;
        elem->st.speculative |= speculative;
        if (env->stack_size > BPF_COMPLEXITY_LIMIT_JMP_SEQ) {
                verbose(env, "The sequence of %d jumps is too complex.\n",
                        env->stack_size);
                goto err;
        }
        if (elem->st.parent) {
                ++elem->st.parent->branches;
                /* WARN_ON(branches > 2) technically makes sense here,
                 * but
                 * 1. speculative states will bump 'branches' for non-branch
                 * instructions
                 * 2. is_state_visited() heuristics may decide not to create
                 * a new state for a sequence of branches and all such current
                 * and cloned states will be pointing to a single parent state
                 * which might have large 'branches' count.
                 */
        }
        return &elem->st;
err:
        free_verifier_state(env->cur_state, true);
        env->cur_state = NULL;
        /* pop all elements and return */
        while (!pop_stack(env, NULL, NULL, false));
        return NULL;
}

#define CALLER_SAVED_REGS 6
static const int caller_saved[CALLER_SAVED_REGS] = {
        BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
};

static void __mark_reg_not_init(const struct bpf_verifier_env *env,
                                struct bpf_reg_state *reg);

/* This helper doesn't clear reg->id */
static void ___mark_reg_known(struct bpf_reg_state *reg, u64 imm)
{
        reg->var_off = tnum_const(imm);
        reg->smin_value = (s64)imm;
        reg->smax_value = (s64)imm;
        reg->umin_value = imm;
        reg->umax_value = imm;

        reg->s32_min_value = (s32)imm;
        reg->s32_max_value = (s32)imm;
        reg->u32_min_value = (u32)imm;
        reg->u32_max_value = (u32)imm;
}

/* Mark the unknown part of a register (variable offset or scalar value) as
 * known to have the value @imm.
 */
static void __mark_reg_known(struct bpf_reg_state *reg, u64 imm)
{
        /* Clear id, off, and union(map_ptr, range) */
        memset(((u8 *)reg) + sizeof(reg->type), 0,
               offsetof(struct bpf_reg_state, var_off) - sizeof(reg->type));
        ___mark_reg_known(reg, imm);
}

static void __mark_reg32_known(struct bpf_reg_state *reg, u64 imm)
{
        reg->var_off = tnum_const_subreg(reg->var_off, imm);
        reg->s32_min_value = (s32)imm;
        reg->s32_max_value = (s32)imm;
        reg->u32_min_value = (u32)imm;
        reg->u32_max_value = (u32)imm;
}

/* Mark the 'variable offset' part of a register as zero.  This should be
 * used only on registers holding a pointer type.
 */
static void __mark_reg_known_zero(struct bpf_reg_state *reg)
{
        __mark_reg_known(reg, 0);
}

static void __mark_reg_const_zero(struct bpf_reg_state *reg)
{
        __mark_reg_known(reg, 0);
        reg->type = SCALAR_VALUE;
}

static void mark_reg_known_zero(struct bpf_verifier_env *env,
                                struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_known_zero(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs */
                for (regno = 0; regno < MAX_BPF_REG; regno++)
                        __mark_reg_not_init(env, regs + regno);
                return;
        }
        __mark_reg_known_zero(regs + regno);
}

static void mark_ptr_not_null_reg(struct bpf_reg_state *reg)
{
        switch (reg->type) {
        case PTR_TO_MAP_VALUE_OR_NULL: {
                const struct bpf_map *map = reg->map_ptr;

                if (map->inner_map_meta) {
                        reg->type = CONST_PTR_TO_MAP;
                        reg->map_ptr = map->inner_map_meta;
                } else if (map->map_type == BPF_MAP_TYPE_XSKMAP) {
                        reg->type = PTR_TO_XDP_SOCK;
                } else if (map->map_type == BPF_MAP_TYPE_SOCKMAP ||
                           map->map_type == BPF_MAP_TYPE_SOCKHASH) {
                        reg->type = PTR_TO_SOCKET;
                } else {
                        reg->type = PTR_TO_MAP_VALUE;
                }
                break;
        }
        case PTR_TO_SOCKET_OR_NULL:
                reg->type = PTR_TO_SOCKET;
                break;
        case PTR_TO_SOCK_COMMON_OR_NULL:
                reg->type = PTR_TO_SOCK_COMMON;
                break;
        case PTR_TO_TCP_SOCK_OR_NULL:
                reg->type = PTR_TO_TCP_SOCK;
                break;
        case PTR_TO_BTF_ID_OR_NULL:
                reg->type = PTR_TO_BTF_ID;
                break;
        case PTR_TO_MEM_OR_NULL:
                reg->type = PTR_TO_MEM;
                break;
        case PTR_TO_RDONLY_BUF_OR_NULL:
                reg->type = PTR_TO_RDONLY_BUF;
                break;
        case PTR_TO_RDWR_BUF_OR_NULL:
                reg->type = PTR_TO_RDWR_BUF;
                break;
        default:
                WARN_ONCE(1, "unknown nullable register type");
        }
}

static bool reg_is_pkt_pointer(const struct bpf_reg_state *reg)
{
        return type_is_pkt_pointer(reg->type);
}

static bool reg_is_pkt_pointer_any(const struct bpf_reg_state *reg)
{
        return reg_is_pkt_pointer(reg) ||
               reg->type == PTR_TO_PACKET_END;
}

/* Unmodified PTR_TO_PACKET[_META,_END] register from ctx access. */
static bool reg_is_init_pkt_pointer(const struct bpf_reg_state *reg,
                                    enum bpf_reg_type which)
{
        /* The register can already have a range from prior markings.
         * This is fine as long as it hasn't been advanced from its
         * origin.
         */
        return reg->type == which &&
               reg->id == 0 &&
               reg->off == 0 &&
               tnum_equals_const(reg->var_off, 0);
}

/* Reset the min/max bounds of a register */
static void __mark_reg_unbounded(struct bpf_reg_state *reg)
{
        reg->smin_value = S64_MIN;
        reg->smax_value = S64_MAX;
        reg->umin_value = 0;
        reg->umax_value = U64_MAX;

        reg->s32_min_value = S32_MIN;
        reg->s32_max_value = S32_MAX;
        reg->u32_min_value = 0;
        reg->u32_max_value = U32_MAX;
}

static void __mark_reg64_unbounded(struct bpf_reg_state *reg)
{
        reg->smin_value = S64_MIN;
        reg->smax_value = S64_MAX;
        reg->umin_value = 0;
        reg->umax_value = U64_MAX;
}

static void __mark_reg32_unbounded(struct bpf_reg_state *reg)
{
        reg->s32_min_value = S32_MIN;
        reg->s32_max_value = S32_MAX;
        reg->u32_min_value = 0;
        reg->u32_max_value = U32_MAX;
}

static void __update_reg32_bounds(struct bpf_reg_state *reg)
{
        struct tnum var32_off = tnum_subreg(reg->var_off);

        /* min signed is max(sign bit) | min(other bits) */
        reg->s32_min_value = max_t(s32, reg->s32_min_value,
                        var32_off.value | (var32_off.mask & S32_MIN));
        /* max signed is min(sign bit) | max(other bits) */
        reg->s32_max_value = min_t(s32, reg->s32_max_value,
                        var32_off.value | (var32_off.mask & S32_MAX));
        reg->u32_min_value = max_t(u32, reg->u32_min_value, (u32)var32_off.value);
        reg->u32_max_value = min(reg->u32_max_value,
                                 (u32)(var32_off.value | var32_off.mask));
}

static void __update_reg64_bounds(struct bpf_reg_state *reg)
{
        /* min signed is max(sign bit) | min(other bits) */
        reg->smin_value = max_t(s64, reg->smin_value,
                                reg->var_off.value | (reg->var_off.mask & S64_MIN));
        /* max signed is min(sign bit) | max(other bits) */
        reg->smax_value = min_t(s64, reg->smax_value,
                                reg->var_off.value | (reg->var_off.mask & S64_MAX));
        reg->umin_value = max(reg->umin_value, reg->var_off.value);
        reg->umax_value = min(reg->umax_value,
                              reg->var_off.value | reg->var_off.mask);
}

static void __update_reg_bounds(struct bpf_reg_state *reg)
{
        __update_reg32_bounds(reg);
        __update_reg64_bounds(reg);
}

/* Uses signed min/max values to inform unsigned, and vice-versa */
static void __reg32_deduce_bounds(struct bpf_reg_state *reg)
{
        /* Learn sign from signed bounds.
         * If we cannot cross the sign boundary, then signed and unsigned bounds
         * are the same, so combine.  This works even in the negative case, e.g.
         * -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff.
         */
        if (reg->s32_min_value >= 0 || reg->s32_max_value < 0) {
                reg->s32_min_value = reg->u32_min_value =
                        max_t(u32, reg->s32_min_value, reg->u32_min_value);
                reg->s32_max_value = reg->u32_max_value =
                        min_t(u32, reg->s32_max_value, reg->u32_max_value);
                return;
        }
        /* Learn sign from unsigned bounds.  Signed bounds cross the sign
         * boundary, so we must be careful.
         */
        if ((s32)reg->u32_max_value >= 0) {
                /* Positive.  We can't learn anything from the smin, but smax
                 * is positive, hence safe.
                 */
                reg->s32_min_value = reg->u32_min_value;
                reg->s32_max_value = reg->u32_max_value =
                        min_t(u32, reg->s32_max_value, reg->u32_max_value);
        } else if ((s32)reg->u32_min_value < 0) {
                /* Negative.  We can't learn anything from the smax, but smin
                 * is negative, hence safe.
                 */
                reg->s32_min_value = reg->u32_min_value =
                        max_t(u32, reg->s32_min_value, reg->u32_min_value);
                reg->s32_max_value = reg->u32_max_value;
        }
}

static void __reg64_deduce_bounds(struct bpf_reg_state *reg)
{
        /* Learn sign from signed bounds.
         * If we cannot cross the sign boundary, then signed and unsigned bounds
         * are the same, so combine.  This works even in the negative case, e.g.
         * -3 s<= x s<= -1 implies 0xf...fd u<= x u<= 0xf...ff.
         */
        if (reg->smin_value >= 0 || reg->smax_value < 0) {
                reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
                                                          reg->umin_value);
                reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
                                                          reg->umax_value);
                return;
        }
        /* Learn sign from unsigned bounds.  Signed bounds cross the sign
         * boundary, so we must be careful.
         */
        if ((s64)reg->umax_value >= 0) {
                /* Positive.  We can't learn anything from the smin, but smax
                 * is positive, hence safe.
                 */
                reg->smin_value = reg->umin_value;
                reg->smax_value = reg->umax_value = min_t(u64, reg->smax_value,
                                                          reg->umax_value);
        } else if ((s64)reg->umin_value < 0) {
                /* Negative.  We can't learn anything from the smax, but smin
                 * is negative, hence safe.
                 */
                reg->smin_value = reg->umin_value = max_t(u64, reg->smin_value,
                                                          reg->umin_value);
                reg->smax_value = reg->umax_value;
        }
}

static void __reg_deduce_bounds(struct bpf_reg_state *reg)
{
        __reg32_deduce_bounds(reg);
        __reg64_deduce_bounds(reg);
}

/* Attempts to improve var_off based on unsigned min/max information */
static void __reg_bound_offset(struct bpf_reg_state *reg)
{
        struct tnum var64_off = tnum_intersect(reg->var_off,
                                               tnum_range(reg->umin_value,
                                                          reg->umax_value));
        struct tnum var32_off = tnum_intersect(tnum_subreg(reg->var_off),
                                                tnum_range(reg->u32_min_value,
                                                           reg->u32_max_value));

        reg->var_off = tnum_or(tnum_clear_subreg(var64_off), var32_off);
}

static void __reg_assign_32_into_64(struct bpf_reg_state *reg)
{
        reg->umin_value = reg->u32_min_value;
        reg->umax_value = reg->u32_max_value;
        /* Attempt to pull 32-bit signed bounds into 64-bit bounds
         * but must be positive otherwise set to worse case bounds
         * and refine later from tnum.
         */
        if (reg->s32_min_value >= 0 && reg->s32_max_value >= 0)
                reg->smax_value = reg->s32_max_value;
        else
                reg->smax_value = U32_MAX;
        if (reg->s32_min_value >= 0)
                reg->smin_value = reg->s32_min_value;
        else
                reg->smin_value = 0;
}

static void __reg_combine_32_into_64(struct bpf_reg_state *reg)
{
        /* special case when 64-bit register has upper 32-bit register
         * zeroed. Typically happens after zext or <<32, >>32 sequence
         * allowing us to use 32-bit bounds directly,
         */
        if (tnum_equals_const(tnum_clear_subreg(reg->var_off), 0)) {
                __reg_assign_32_into_64(reg);
        } else {
                /* Otherwise the best we can do is push lower 32bit known and
                 * unknown bits into register (var_off set from jmp logic)
                 * then learn as much as possible from the 64-bit tnum
                 * known and unknown bits. The previous smin/smax bounds are
                 * invalid here because of jmp32 compare so mark them unknown
                 * so they do not impact tnum bounds calculation.
                 */
                __mark_reg64_unbounded(reg);
                __update_reg_bounds(reg);
        }

        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __reg_deduce_bounds(reg);
        __reg_bound_offset(reg);
        __update_reg_bounds(reg);
}

static bool __reg64_bound_s32(s64 a)
{
        return a > S32_MIN && a < S32_MAX;
}

static bool __reg64_bound_u32(u64 a)
{
        if (a > U32_MIN && a < U32_MAX)
                return true;
        return false;
}

static void __reg_combine_64_into_32(struct bpf_reg_state *reg)
{
        __mark_reg32_unbounded(reg);

        if (__reg64_bound_s32(reg->smin_value) && __reg64_bound_s32(reg->smax_value)) {
                reg->s32_min_value = (s32)reg->smin_value;
                reg->s32_max_value = (s32)reg->smax_value;
        }
        if (__reg64_bound_u32(reg->umin_value))
                reg->u32_min_value = (u32)reg->umin_value;
        if (__reg64_bound_u32(reg->umax_value))
                reg->u32_max_value = (u32)reg->umax_value;

        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __reg_deduce_bounds(reg);
        __reg_bound_offset(reg);
        __update_reg_bounds(reg);
}

/* Mark a register as having a completely unknown (scalar) value. */
static void __mark_reg_unknown(const struct bpf_verifier_env *env,
                               struct bpf_reg_state *reg)
{
        /*
         * Clear type, id, off, and union(map_ptr, range) and
         * padding between 'type' and union
         */
        memset(reg, 0, offsetof(struct bpf_reg_state, var_off));
        reg->type = SCALAR_VALUE;
        reg->var_off = tnum_unknown;
        reg->frameno = 0;
        reg->precise = env->subprog_cnt > 1 || !env->bpf_capable;
        __mark_reg_unbounded(reg);
}

static void mark_reg_unknown(struct bpf_verifier_env *env,
                             struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_unknown(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs except FP */
                for (regno = 0; regno < BPF_REG_FP; regno++)
                        __mark_reg_not_init(env, regs + regno);
                return;
        }
        __mark_reg_unknown(env, regs + regno);
}

static void __mark_reg_not_init(const struct bpf_verifier_env *env,
                                struct bpf_reg_state *reg)
{
        __mark_reg_unknown(env, reg);
        reg->type = NOT_INIT;
}

static void mark_reg_not_init(struct bpf_verifier_env *env,
                              struct bpf_reg_state *regs, u32 regno)
{
        if (WARN_ON(regno >= MAX_BPF_REG)) {
                verbose(env, "mark_reg_not_init(regs, %u)\n", regno);
                /* Something bad happened, let's kill all regs except FP */
                for (regno = 0; regno < BPF_REG_FP; regno++)
                        __mark_reg_not_init(env, regs + regno);
                return;
        }
        __mark_reg_not_init(env, regs + regno);
}

static void mark_btf_ld_reg(struct bpf_verifier_env *env,
                            struct bpf_reg_state *regs, u32 regno,
                            enum bpf_reg_type reg_type,
                            struct btf *btf, u32 btf_id)
{
        if (reg_type == SCALAR_VALUE) {
                mark_reg_unknown(env, regs, regno);
                return;
        }
        mark_reg_known_zero(env, regs, regno);
        regs[regno].type = PTR_TO_BTF_ID;
        regs[regno].btf = btf;
        regs[regno].btf_id = btf_id;
}

#define DEF_NOT_SUBREG  (0)
static void init_reg_state(struct bpf_verifier_env *env,
                           struct bpf_func_state *state)
{
        struct bpf_reg_state *regs = state->regs;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++) {
                mark_reg_not_init(env, regs, i);
                regs[i].live = REG_LIVE_NONE;
                regs[i].parent = NULL;
                regs[i].subreg_def = DEF_NOT_SUBREG;
        }

        /* frame pointer */
        regs[BPF_REG_FP].type = PTR_TO_STACK;
        mark_reg_known_zero(env, regs, BPF_REG_FP);
        regs[BPF_REG_FP].frameno = state->frameno;
}

#define BPF_MAIN_FUNC (-1)
static void init_func_state(struct bpf_verifier_env *env,
                            struct bpf_func_state *state,
                            int callsite, int frameno, int subprogno)
{
        state->callsite = callsite;
        state->frameno = frameno;
        state->subprogno = subprogno;
        init_reg_state(env, state);
}

enum reg_arg_type {
        SRC_OP,         /* register is used as source operand */
        DST_OP,         /* register is used as destination operand */
        DST_OP_NO_MARK  /* same as above, check only, don't mark */
};

static int cmp_subprogs(const void *a, const void *b)
{
        return ((struct bpf_subprog_info *)a)->start -
               ((struct bpf_subprog_info *)b)->start;
}

static int find_subprog(struct bpf_verifier_env *env, int off)
{
        struct bpf_subprog_info *p;

        p = bsearch(&off, env->subprog_info, env->subprog_cnt,
                    sizeof(env->subprog_info[0]), cmp_subprogs);
        if (!p)
                return -ENOENT;
        return p - env->subprog_info;

}

static int add_subprog(struct bpf_verifier_env *env, int off)
{
        int insn_cnt = env->prog->len;
        int ret;

        if (off >= insn_cnt || off < 0) {
                verbose(env, "call to invalid destination\n");
                return -EINVAL;
        }
        ret = find_subprog(env, off);
        if (ret >= 0)
                return ret;
        if (env->subprog_cnt >= BPF_MAX_SUBPROGS) {
                verbose(env, "too many subprograms\n");
                return -E2BIG;
        }
        env->subprog_info[env->subprog_cnt++].start = off;
        sort(env->subprog_info, env->subprog_cnt,
             sizeof(env->subprog_info[0]), cmp_subprogs, NULL);
        return env->subprog_cnt - 1;
}

static int check_subprogs(struct bpf_verifier_env *env)
{
        int i, ret, subprog_start, subprog_end, off, cur_subprog = 0;
        struct bpf_subprog_info *subprog = env->subprog_info;
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;

        /* Add entry function. */
        ret = add_subprog(env, 0);
        if (ret < 0)
                return ret;

        /* determine subprog starts. The end is one before the next starts */
        for (i = 0; i < insn_cnt; i++) {
                if (bpf_pseudo_func(insn + i)) {
                        if (!env->bpf_capable) {
                                verbose(env,
                                        "function pointers are allowed for CAP_BPF and CAP_SYS_ADMIN\n");
                                return -EPERM;
                        }
                        ret = add_subprog(env, i + insn[i].imm + 1);
                        if (ret < 0)
                                return ret;
                        /* remember subprog */
                        insn[i + 1].imm = ret;
                        continue;
                }
                if (!bpf_pseudo_call(insn + i))
                        continue;
                if (!env->bpf_capable) {
                        verbose(env,
                                "function calls to other bpf functions are allowed for CAP_BPF and CAP_SYS_ADMIN\n");
                        return -EPERM;
                }
                ret = add_subprog(env, i + insn[i].imm + 1);
                if (ret < 0)
                        return ret;
        }

        /* Add a fake 'exit' subprog which could simplify subprog iteration
         * logic. 'subprog_cnt' should not be increased.
         */
        subprog[env->subprog_cnt].start = insn_cnt;

        if (env->log.level & BPF_LOG_LEVEL2)
                for (i = 0; i < env->subprog_cnt; i++)
                        verbose(env, "func#%d @%d\n", i, subprog[i].start);

        /* now check that all jumps are within the same subprog */
        subprog_start = subprog[cur_subprog].start;
        subprog_end = subprog[cur_subprog + 1].start;
        for (i = 0; i < insn_cnt; i++) {
                u8 code = insn[i].code;

                if (code == (BPF_JMP | BPF_CALL) &&
                    insn[i].imm == BPF_FUNC_tail_call &&
                    insn[i].src_reg != BPF_PSEUDO_CALL)
                        subprog[cur_subprog].has_tail_call = true;
                if (BPF_CLASS(code) == BPF_LD &&
                    (BPF_MODE(code) == BPF_ABS || BPF_MODE(code) == BPF_IND))
                        subprog[cur_subprog].has_ld_abs = true;
                if (BPF_CLASS(code) != BPF_JMP && BPF_CLASS(code) != BPF_JMP32)
                        goto next;
                if (BPF_OP(code) == BPF_EXIT || BPF_OP(code) == BPF_CALL)
                        goto next;
                off = i + insn[i].off + 1;
                if (off < subprog_start || off >= subprog_end) {
                        verbose(env, "jump out of range from insn %d to %d\n", i, off);
                        return -EINVAL;
                }
next:
                if (i == subprog_end - 1) {
                        /* to avoid fall-through from one subprog into another
                         * the last insn of the subprog should be either exit
                         * or unconditional jump back
                         */
                        if (code != (BPF_JMP | BPF_EXIT) &&
                            code != (BPF_JMP | BPF_JA)) {
                                verbose(env, "last insn is not an exit or jmp\n");
                                return -EINVAL;
                        }
                        subprog_start = subprog_end;
                        cur_subprog++;
                        if (cur_subprog < env->subprog_cnt)
                                subprog_end = subprog[cur_subprog + 1].start;
                }
        }
        return 0;
}

/* Parentage chain of this register (or stack slot) should take care of all
 * issues like callee-saved registers, stack slot allocation time, etc.
 */
static int mark_reg_read(struct bpf_verifier_env *env,
                         const struct bpf_reg_state *state,
                         struct bpf_reg_state *parent, u8 flag)
{
        bool writes = parent == state->parent; /* Observe write marks */
        int cnt = 0;

        while (parent) {
                /* if read wasn't screened by an earlier write ... */
                if (writes && state->live & REG_LIVE_WRITTEN)
                        break;
                if (parent->live & REG_LIVE_DONE) {
                        verbose(env, "verifier BUG type %s var_off %lld off %d\n",
                                reg_type_str[parent->type],
                                parent->var_off.value, parent->off);
                        return -EFAULT;
                }
                /* The first condition is more likely to be true than the
                 * second, checked it first.
                 */
                if ((parent->live & REG_LIVE_READ) == flag ||
                    parent->live & REG_LIVE_READ64)
                        /* The parentage chain never changes and
                         * this parent was already marked as LIVE_READ.
                         * There is no need to keep walking the chain again and
                         * keep re-marking all parents as LIVE_READ.
                         * This case happens when the same register is read
                         * multiple times without writes into it in-between.
                         * Also, if parent has the stronger REG_LIVE_READ64 set,
                         * then no need to set the weak REG_LIVE_READ32.
                         */
                        break;
                /* ... then we depend on parent's value */
                parent->live |= flag;
                /* REG_LIVE_READ64 overrides REG_LIVE_READ32. */
                if (flag == REG_LIVE_READ64)
                        parent->live &= ~REG_LIVE_READ32;
                state = parent;
                parent = state->parent;
                writes = true;
                cnt++;
        }

        if (env->longest_mark_read_walk < cnt)
                env->longest_mark_read_walk = cnt;
        return 0;
}

/* This function is supposed to be used by the following 32-bit optimization
 * code only. It returns TRUE if the source or destination register operates
 * on 64-bit, otherwise return FALSE.
 */
static bool is_reg64(struct bpf_verifier_env *env, struct bpf_insn *insn,
                     u32 regno, struct bpf_reg_state *reg, enum reg_arg_type t)
{
        u8 code, class, op;

        code = insn->code;
        class = BPF_CLASS(code);
        op = BPF_OP(code);
        if (class == BPF_JMP) {
                /* BPF_EXIT for "main" will reach here. Return TRUE
                 * conservatively.
                 */
                if (op == BPF_EXIT)
                        return true;
                if (op == BPF_CALL) {
                        /* BPF to BPF call will reach here because of marking
                         * caller saved clobber with DST_OP_NO_MARK for which we
                         * don't care the register def because they are anyway
                         * marked as NOT_INIT already.
                         */
                        if (insn->src_reg == BPF_PSEUDO_CALL)
                                return false;
                        /* Helper call will reach here because of arg type
                         * check, conservatively return TRUE.
                         */
                        if (t == SRC_OP)
                                return true;

                        return false;
                }
        }

        if (class == BPF_ALU64 || class == BPF_JMP ||
            /* BPF_END always use BPF_ALU class. */
            (class == BPF_ALU && op == BPF_END && insn->imm == 64))
                return true;

        if (class == BPF_ALU || class == BPF_JMP32)
                return false;

        if (class == BPF_LDX) {
                if (t != SRC_OP)
                        return BPF_SIZE(code) == BPF_DW;
                /* LDX source must be ptr. */
                return true;
        }

        if (class == BPF_STX) {
                /* BPF_STX (including atomic variants) has multiple source
                 * operands, one of which is a ptr. Check whether the caller is
                 * asking about it.
                 */
                if (t == SRC_OP && reg->type != SCALAR_VALUE)
                        return true;
                return BPF_SIZE(code) == BPF_DW;
        }

        if (class == BPF_LD) {
                u8 mode = BPF_MODE(code);

                /* LD_IMM64 */
                if (mode == BPF_IMM)
                        return true;

                /* Both LD_IND and LD_ABS return 32-bit data. */
                if (t != SRC_OP)
                        return  false;

                /* Implicit ctx ptr. */
                if (regno == BPF_REG_6)
                        return true;

                /* Explicit source could be any width. */
                return true;
        }

        if (class == BPF_ST)
                /* The only source register for BPF_ST is a ptr. */
                return true;

        /* Conservatively return true at default. */
        return true;
}

/* Return the regno defined by the insn, or -1. */
static int insn_def_regno(const struct bpf_insn *insn)
{
        switch (BPF_CLASS(insn->code)) {
        case BPF_JMP:
        case BPF_JMP32:
        case BPF_ST:
                return -1;
        case BPF_STX:
                if (BPF_MODE(insn->code) == BPF_ATOMIC &&
                    (insn->imm & BPF_FETCH)) {
                        if (insn->imm == BPF_CMPXCHG)
                                return BPF_REG_0;
                        else
                                return insn->src_reg;
                } else {
                        return -1;
                }
        default:
                return insn->dst_reg;
        }
}

/* Return TRUE if INSN has defined any 32-bit value explicitly. */
static bool insn_has_def32(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        int dst_reg = insn_def_regno(insn);

        if (dst_reg == -1)
                return false;

        return !is_reg64(env, insn, dst_reg, NULL, DST_OP);
}

static void mark_insn_zext(struct bpf_verifier_env *env,
                           struct bpf_reg_state *reg)
{
        s32 def_idx = reg->subreg_def;

        if (def_idx == DEF_NOT_SUBREG)
                return;

        env->insn_aux_data[def_idx - 1].zext_dst = true;
        /* The dst will be zero extended, so won't be sub-register anymore. */
        reg->subreg_def = DEF_NOT_SUBREG;
}

static int check_reg_arg(struct bpf_verifier_env *env, u32 regno,
                         enum reg_arg_type t)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_insn *insn = env->prog->insnsi + env->insn_idx;
        struct bpf_reg_state *reg, *regs = state->regs;
        bool rw64;

        if (regno >= MAX_BPF_REG) {
                verbose(env, "R%d is invalid\n", regno);
                return -EINVAL;
        }

        reg = &regs[regno];
        rw64 = is_reg64(env, insn, regno, reg, t);
        if (t == SRC_OP) {
                /* check whether register used as source operand can be read */
                if (reg->type == NOT_INIT) {
                        verbose(env, "R%d !read_ok\n", regno);
                        return -EACCES;
                }
                /* We don't need to worry about FP liveness because it's read-only */
                if (regno == BPF_REG_FP)
                        return 0;

                if (rw64)
                        mark_insn_zext(env, reg);

                return mark_reg_read(env, reg, reg->parent,
                                     rw64 ? REG_LIVE_READ64 : REG_LIVE_READ32);
        } else {
                /* check whether register used as dest operand can be written to */
                if (regno == BPF_REG_FP) {
                        verbose(env, "frame pointer is read only\n");
                        return -EACCES;
                }
                reg->live |= REG_LIVE_WRITTEN;
                reg->subreg_def = rw64 ? DEF_NOT_SUBREG : env->insn_idx + 1;
                if (t == DST_OP)
                        mark_reg_unknown(env, regs, regno);
        }
        return 0;
}

/* for any branch, call, exit record the history of jmps in the given state */
static int push_jmp_history(struct bpf_verifier_env *env,
                            struct bpf_verifier_state *cur)
{
        u32 cnt = cur->jmp_history_cnt;
        struct bpf_idx_pair *p;

        cnt++;
        p = krealloc(cur->jmp_history, cnt * sizeof(*p), GFP_USER);
        if (!p)
                return -ENOMEM;
        p[cnt - 1].idx = env->insn_idx;
        p[cnt - 1].prev_idx = env->prev_insn_idx;
        cur->jmp_history = p;
        cur->jmp_history_cnt = cnt;
        return 0;
}

/* Backtrack one insn at a time. If idx is not at the top of recorded
 * history then previous instruction came from straight line execution.
 */
static int get_prev_insn_idx(struct bpf_verifier_state *st, int i,
                             u32 *history)
{
        u32 cnt = *history;

        if (cnt && st->jmp_history[cnt - 1].idx == i) {
                i = st->jmp_history[cnt - 1].prev_idx;
                (*history)--;
        } else {
                i--;
        }
        return i;
}

/* For given verifier state backtrack_insn() is called from the last insn to
 * the first insn. Its purpose is to compute a bitmask of registers and
 * stack slots that needs precision in the parent verifier state.
 */
static int backtrack_insn(struct bpf_verifier_env *env, int idx,
                          u32 *reg_mask, u64 *stack_mask)
{
        const struct bpf_insn_cbs cbs = {
                .cb_print       = verbose,
                .private_data   = env,
        };
        struct bpf_insn *insn = env->prog->insnsi + idx;
        u8 class = BPF_CLASS(insn->code);
        u8 opcode = BPF_OP(insn->code);
        u8 mode = BPF_MODE(insn->code);
        u32 dreg = 1u << insn->dst_reg;
        u32 sreg = 1u << insn->src_reg;
        u32 spi;

        if (insn->code == 0)
                return 0;
        if (env->log.level & BPF_LOG_LEVEL) {
                verbose(env, "regs=%x stack=%llx before ", *reg_mask, *stack_mask);
                verbose(env, "%d: ", idx);
                print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
        }

        if (class == BPF_ALU || class == BPF_ALU64) {
                if (!(*reg_mask & dreg))
                        return 0;
                if (opcode == BPF_MOV) {
                        if (BPF_SRC(insn->code) == BPF_X) {
                                /* dreg = sreg
                                 * dreg needs precision after this insn
                                 * sreg needs precision before this insn
                                 */
                                *reg_mask &= ~dreg;
                                *reg_mask |= sreg;
                        } else {
                                /* dreg = K
                                 * dreg needs precision after this insn.
                                 * Corresponding register is already marked
                                 * as precise=true in this verifier state.
                                 * No further markings in parent are necessary
                                 */
                                *reg_mask &= ~dreg;
                        }
                } else {
                        if (BPF_SRC(insn->code) == BPF_X) {
                                /* dreg += sreg
                                 * both dreg and sreg need precision
                                 * before this insn
                                 */
                                *reg_mask |= sreg;
                        } /* else dreg += K
                           * dreg still needs precision before this insn
                           */
                }
        } else if (class == BPF_LDX) {
                if (!(*reg_mask & dreg))
                        return 0;
                *reg_mask &= ~dreg;

                /* scalars can only be spilled into stack w/o losing precision.
                 * Load from any other memory can be zero extended.
                 * The desire to keep that precision is already indicated
                 * by 'precise' mark in corresponding register of this state.
                 * No further tracking necessary.
                 */
                if (insn->src_reg != BPF_REG_FP)
                        return 0;
                if (BPF_SIZE(insn->code) != BPF_DW)
                        return 0;

                /* dreg = *(u64 *)[fp - off] was a fill from the stack.
                 * that [fp - off] slot contains scalar that needs to be
                 * tracked with precision
                 */
                spi = (-insn->off - 1) / BPF_REG_SIZE;
                if (spi >= 64) {
                        verbose(env, "BUG spi %d\n", spi);
                        WARN_ONCE(1, "verifier backtracking bug");
                        return -EFAULT;
                }
                *stack_mask |= 1ull << spi;
        } else if (class == BPF_STX || class == BPF_ST) {
                if (*reg_mask & dreg)
                        /* stx & st shouldn't be using _scalar_ dst_reg
                         * to access memory. It means backtracking
                         * encountered a case of pointer subtraction.
                         */
                        return -ENOTSUPP;
                /* scalars can only be spilled into stack */
                if (insn->dst_reg != BPF_REG_FP)
                        return 0;
                if (BPF_SIZE(insn->code) != BPF_DW)
                        return 0;
                spi = (-insn->off - 1) / BPF_REG_SIZE;
                if (spi >= 64) {
                        verbose(env, "BUG spi %d\n", spi);
                        WARN_ONCE(1, "verifier backtracking bug");
                        return -EFAULT;
                }
                if (!(*stack_mask & (1ull << spi)))
                        return 0;
                *stack_mask &= ~(1ull << spi);
                if (class == BPF_STX)
                        *reg_mask |= sreg;
        } else if (class == BPF_JMP || class == BPF_JMP32) {
                if (opcode == BPF_CALL) {
                        if (insn->src_reg == BPF_PSEUDO_CALL)
                                return -ENOTSUPP;
                        /* regular helper call sets R0 */
                        *reg_mask &= ~1;
                        if (*reg_mask & 0x3f) {
                                /* if backtracing was looking for registers R1-R5
                                 * they should have been found already.
                                 */
                                verbose(env, "BUG regs %x\n", *reg_mask);
                                WARN_ONCE(1, "verifier backtracking bug");
                                return -EFAULT;
                        }
                } else if (opcode == BPF_EXIT) {
                        return -ENOTSUPP;
                }
        } else if (class == BPF_LD) {
                if (!(*reg_mask & dreg))
                        return 0;
                *reg_mask &= ~dreg;
                /* It's ld_imm64 or ld_abs or ld_ind.
                 * For ld_imm64 no further tracking of precision
                 * into parent is necessary
                 */
                if (mode == BPF_IND || mode == BPF_ABS)
                        /* to be analyzed */
                        return -ENOTSUPP;
        }
        return 0;
}

/* the scalar precision tracking algorithm:
 * . at the start all registers have precise=false.
 * . scalar ranges are tracked as normal through alu and jmp insns.
 * . once precise value of the scalar register is used in:
 *   .  ptr + scalar alu
 *   . if (scalar cond K|scalar)
 *   .  helper_call(.., scalar, ...) where ARG_CONST is expected
 *   backtrack through the verifier states and mark all registers and
 *   stack slots with spilled constants that these scalar regisers
 *   should be precise.
 * . during state pruning two registers (or spilled stack slots)
 *   are equivalent if both are not precise.
 *
 * Note the verifier cannot simply walk register parentage chain,
 * since many different registers and stack slots could have been
 * used to compute single precise scalar.
 *
 * The approach of starting with precise=true for all registers and then
 * backtrack to mark a register as not precise when the verifier detects
 * that program doesn't care about specific value (e.g., when helper
 * takes register as ARG_ANYTHING parameter) is not safe.
 *
 * It's ok to walk single parentage chain of the verifier states.
 * It's possible that this backtracking will go all the way till 1st insn.
 * All other branches will be explored for needing precision later.
 *
 * The backtracking needs to deal with cases like:
 *   R8=map_value(id=0,off=0,ks=4,vs=1952,imm=0) R9_w=map_value(id=0,off=40,ks=4,vs=1952,imm=0)
 * r9 -= r8
 * r5 = r9
 * if r5 > 0x79f goto pc+7
 *    R5_w=inv(id=0,umax_value=1951,var_off=(0x0; 0x7ff))
 * r5 += 1
 * ...
 * call bpf_perf_event_output#25
 *   where .arg5_type = ARG_CONST_SIZE_OR_ZERO
 *
 * and this case:
 * r6 = 1
 * call foo // uses callee's r6 inside to compute r0
 * r0 += r6
 * if r0 == 0 goto
 *
 * to track above reg_mask/stack_mask needs to be independent for each frame.
 *
 * Also if parent's curframe > frame where backtracking started,
 * the verifier need to mark registers in both frames, otherwise callees
 * may incorrectly prune callers. This is similar to
 * commit 7640ead93924 ("bpf: verifier: make sure callees don't prune with caller differences")
 *
 * For now backtracking falls back into conservative marking.
 */
static void mark_all_scalars_precise(struct bpf_verifier_env *env,
                                     struct bpf_verifier_state *st)
{
        struct bpf_func_state *func;
        struct bpf_reg_state *reg;
        int i, j;

        /* big hammer: mark all scalars precise in this path.
         * pop_stack may still get !precise scalars.
         */
        for (; st; st = st->parent)
                for (i = 0; i <= st->curframe; i++) {
                        func = st->frame[i];
                        for (j = 0; j < BPF_REG_FP; j++) {
                                reg = &func->regs[j];
                                if (reg->type != SCALAR_VALUE)
                                        continue;
                                reg->precise = true;
                        }
                        for (j = 0; j < func->allocated_stack / BPF_REG_SIZE; j++) {
                                if (func->stack[j].slot_type[0] != STACK_SPILL)
                                        continue;
                                reg = &func->stack[j].spilled_ptr;
                                if (reg->type != SCALAR_VALUE)
                                        continue;
                                reg->precise = true;
                        }
                }
}

static int __mark_chain_precision(struct bpf_verifier_env *env, int regno,
                                  int spi)
{
        struct bpf_verifier_state *st = env->cur_state;
        int first_idx = st->first_insn_idx;
        int last_idx = env->insn_idx;
        struct bpf_func_state *func;
        struct bpf_reg_state *reg;
        u32 reg_mask = regno >= 0 ? 1u << regno : 0;
        u64 stack_mask = spi >= 0 ? 1ull << spi : 0;
        bool skip_first = true;
        bool new_marks = false;
        int i, err;

        if (!env->bpf_capable)
                return 0;

        func = st->frame[st->curframe];
        if (regno >= 0) {
                reg = &func->regs[regno];
                if (reg->type != SCALAR_VALUE) {
                        WARN_ONCE(1, "backtracing misuse");
                        return -EFAULT;
                }
                if (!reg->precise)
                        new_marks = true;
                else
                        reg_mask = 0;
                reg->precise = true;
        }

        while (spi >= 0) {
                if (func->stack[spi].slot_type[0] != STACK_SPILL) {
                        stack_mask = 0;
                        break;
                }
                reg = &func->stack[spi].spilled_ptr;
                if (reg->type != SCALAR_VALUE) {
                        stack_mask = 0;
                        break;
                }
                if (!reg->precise)
                        new_marks = true;
                else
                        stack_mask = 0;
                reg->precise = true;
                break;
        }

        if (!new_marks)
                return 0;
        if (!reg_mask && !stack_mask)
                return 0;
        for (;;) {
                DECLARE_BITMAP(mask, 64);
                u32 history = st->jmp_history_cnt;

                if (env->log.level & BPF_LOG_LEVEL)
                        verbose(env, "last_idx %d first_idx %d\n", last_idx, first_idx);
                for (i = last_idx;;) {
                        if (skip_first) {
                                err = 0;
                                skip_first = false;
                        } else {
                                err = backtrack_insn(env, i, &reg_mask, &stack_mask);
                        }
                        if (err == -ENOTSUPP) {
                                mark_all_scalars_precise(env, st);
                                return 0;
                        } else if (err) {
                                return err;
                        }
                        if (!reg_mask && !stack_mask)
                                /* Found assignment(s) into tracked register in this state.
                                 * Since this state is already marked, just return.
                                 * Nothing to be tracked further in the parent state.
                                 */
                                return 0;
                        if (i == first_idx)
                                break;
                        i = get_prev_insn_idx(st, i, &history);
                        if (i >= env->prog->len) {
                                /* This can happen if backtracking reached insn 0
                                 * and there are still reg_mask or stack_mask
                                 * to backtrack.
                                 * It means the backtracking missed the spot where
                                 * particular register was initialized with a constant.
                                 */
                                verbose(env, "BUG backtracking idx %d\n", i);
                                WARN_ONCE(1, "verifier backtracking bug");
                                return -EFAULT;
                        }
                }
                st = st->parent;
                if (!st)
                        break;

                new_marks = false;
                func = st->frame[st->curframe];
                bitmap_from_u64(mask, reg_mask);
                for_each_set_bit(i, mask, 32) {
                        reg = &func->regs[i];
                        if (reg->type != SCALAR_VALUE) {
                                reg_mask &= ~(1u << i);
                                continue;
                        }
                        if (!reg->precise)
                                new_marks = true;
                        reg->precise = true;
                }

                bitmap_from_u64(mask, stack_mask);
                for_each_set_bit(i, mask, 64) {
                        if (i >= func->allocated_stack / BPF_REG_SIZE) {
                                /* the sequence of instructions:
                                 * 2: (bf) r3 = r10
                                 * 3: (7b) *(u64 *)(r3 -8) = r0
                                 * 4: (79) r4 = *(u64 *)(r10 -8)
                                 * doesn't contain jmps. It's backtracked
                                 * as a single block.
                                 * During backtracking insn 3 is not recognized as
                                 * stack access, so at the end of backtracking
                                 * stack slot fp-8 is still marked in stack_mask.
                                 * However the parent state may not have accessed
                                 * fp-8 and it's "unallocated" stack space.
                                 * In such case fallback to conservative.
                                 */
                                mark_all_scalars_precise(env, st);
                                return 0;
                        }

                        if (func->stack[i].slot_type[0] != STACK_SPILL) {
                                stack_mask &= ~(1ull << i);
                                continue;
                        }
                        reg = &func->stack[i].spilled_ptr;
                        if (reg->type != SCALAR_VALUE) {
                                stack_mask &= ~(1ull << i);
                                continue;
                        }
                        if (!reg->precise)
                                new_marks = true;
                        reg->precise = true;
                }
                if (env->log.level & BPF_LOG_LEVEL) {
                        print_verifier_state(env, func);
                        verbose(env, "parent %s regs=%x stack=%llx marks\n",
                                new_marks ? "didn't have" : "already had",
                                reg_mask, stack_mask);
                }

                if (!reg_mask && !stack_mask)
                        break;
                if (!new_marks)
                        break;

                last_idx = st->last_insn_idx;
                first_idx = st->first_insn_idx;
        }
        return 0;
}

static int mark_chain_precision(struct bpf_verifier_env *env, int regno)
{
        return __mark_chain_precision(env, regno, -1);
}

static int mark_chain_precision_stack(struct bpf_verifier_env *env, int spi)
{
        return __mark_chain_precision(env, -1, spi);
}

static bool is_spillable_regtype(enum bpf_reg_type type)
{
        switch (type) {
        case PTR_TO_MAP_VALUE:
        case PTR_TO_MAP_VALUE_OR_NULL:
        case PTR_TO_STACK:
        case PTR_TO_CTX:
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET_END:
        case PTR_TO_FLOW_KEYS:
        case CONST_PTR_TO_MAP:
        case PTR_TO_SOCKET:
        case PTR_TO_SOCKET_OR_NULL:
        case PTR_TO_SOCK_COMMON:
        case PTR_TO_SOCK_COMMON_OR_NULL:
        case PTR_TO_TCP_SOCK:
        case PTR_TO_TCP_SOCK_OR_NULL:
        case PTR_TO_XDP_SOCK:
        case PTR_TO_BTF_ID:
        case PTR_TO_BTF_ID_OR_NULL:
        case PTR_TO_RDONLY_BUF:
        case PTR_TO_RDONLY_BUF_OR_NULL:
        case PTR_TO_RDWR_BUF:
        case PTR_TO_RDWR_BUF_OR_NULL:
        case PTR_TO_PERCPU_BTF_ID:
        case PTR_TO_MEM:
        case PTR_TO_MEM_OR_NULL:
        case PTR_TO_FUNC:
        case PTR_TO_MAP_KEY:
                return true;
        default:
                return false;
        }
}

/* Does this register contain a constant zero? */
static bool register_is_null(struct bpf_reg_state *reg)
{
        return reg->type == SCALAR_VALUE && tnum_equals_const(reg->var_off, 0);
}

static bool register_is_const(struct bpf_reg_state *reg)
{
        return reg->type == SCALAR_VALUE && tnum_is_const(reg->var_off);
}

static bool __is_scalar_unbounded(struct bpf_reg_state *reg)
{
        return tnum_is_unknown(reg->var_off) &&
               reg->smin_value == S64_MIN && reg->smax_value == S64_MAX &&
               reg->umin_value == 0 && reg->umax_value == U64_MAX &&
               reg->s32_min_value == S32_MIN && reg->s32_max_value == S32_MAX &&
               reg->u32_min_value == 0 && reg->u32_max_value == U32_MAX;
}

static bool register_is_bounded(struct bpf_reg_state *reg)
{
        return reg->type == SCALAR_VALUE && !__is_scalar_unbounded(reg);
}

static bool __is_pointer_value(bool allow_ptr_leaks,
                               const struct bpf_reg_state *reg)
{
        if (allow_ptr_leaks)
                return false;

        return reg->type != SCALAR_VALUE;
}

static void save_register_state(struct bpf_func_state *state,
                                int spi, struct bpf_reg_state *reg)
{
        int i;

        state->stack[spi].spilled_ptr = *reg;
        state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN;

        for (i = 0; i < BPF_REG_SIZE; i++)
                state->stack[spi].slot_type[i] = STACK_SPILL;
}

/* check_stack_{read,write}_fixed_off functions track spill/fill of registers,
 * stack boundary and alignment are checked in check_mem_access()
 */
static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
                                       /* stack frame we're writing to */
                                       struct bpf_func_state *state,
                                       int off, int size, int value_regno,
                                       int insn_idx)
{
        struct bpf_func_state *cur; /* state of the current function */
        int i, slot = -off - 1, spi = slot / BPF_REG_SIZE, err;
        u32 dst_reg = env->prog->insnsi[insn_idx].dst_reg;
        struct bpf_reg_state *reg = NULL;

        err = realloc_func_state(state, round_up(slot + 1, BPF_REG_SIZE),
                                 state->acquired_refs, true);
        if (err)
                return err;
        /* caller checked that off % size == 0 and -MAX_BPF_STACK <= off < 0,
         * so it's aligned access and [off, off + size) are within stack limits
         */
        if (!env->allow_ptr_leaks &&
            state->stack[spi].slot_type[0] == STACK_SPILL &&
            size != BPF_REG_SIZE) {
                verbose(env, "attempt to corrupt spilled pointer on stack\n");
                return -EACCES;
        }

        cur = env->cur_state->frame[env->cur_state->curframe];
        if (value_regno >= 0)
                reg = &cur->regs[value_regno];

        if (reg && size == BPF_REG_SIZE && register_is_bounded(reg) &&
            !register_is_null(reg) && env->bpf_capable) {
                if (dst_reg != BPF_REG_FP) {
                        /* The backtracking logic can only recognize explicit
                         * stack slot address like [fp - 8]. Other spill of
                         * scalar via different register has to be conervative.
                         * Backtrack from here and mark all registers as precise
                         * that contributed into 'reg' being a constant.
                         */
                        err = mark_chain_precision(env, value_regno);
                        if (err)
                                return err;
                }
                save_register_state(state, spi, reg);
        } else if (reg && is_spillable_regtype(reg->type)) {
                /* register containing pointer is being spilled into stack */
                if (size != BPF_REG_SIZE) {
                        verbose_linfo(env, insn_idx, "; ");
                        verbose(env, "invalid size of register spill\n");
                        return -EACCES;
                }

                if (state != cur && reg->type == PTR_TO_STACK) {
                        verbose(env, "cannot spill pointers to stack into stack frame of the caller\n");
                        return -EINVAL;
                }

                if (!env->bypass_spec_v4) {
                        bool sanitize = false;

                        if (state->stack[spi].slot_type[0] == STACK_SPILL &&
                            register_is_const(&state->stack[spi].spilled_ptr))
                                sanitize = true;
                        for (i = 0; i < BPF_REG_SIZE; i++)
                                if (state->stack[spi].slot_type[i] == STACK_MISC) {
                                        sanitize = true;
                                        break;
                                }
                        if (sanitize) {
                                int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off;
                                int soff = (-spi - 1) * BPF_REG_SIZE;

                                /* detected reuse of integer stack slot with a pointer
                                 * which means either llvm is reusing stack slot or
                                 * an attacker is trying to exploit CVE-2018-3639
                                 * (speculative store bypass)
                                 * Have to sanitize that slot with preemptive
                                 * store of zero.
                                 */
                                if (*poff && *poff != soff) {
                                        /* disallow programs where single insn stores
                                         * into two different stack slots, since verifier
                                         * cannot sanitize them
                                         */
                                        verbose(env,
                                                "insn %d cannot access two stack slots fp%d and fp%d",
                                                insn_idx, *poff, soff);
                                        return -EINVAL;
                                }
                                *poff = soff;
                        }
                }
                save_register_state(state, spi, reg);
        } else {
                u8 type = STACK_MISC;

                /* regular write of data into stack destroys any spilled ptr */
                state->stack[spi].spilled_ptr.type = NOT_INIT;
                /* Mark slots as STACK_MISC if they belonged to spilled ptr. */
                if (state->stack[spi].slot_type[0] == STACK_SPILL)
                        for (i = 0; i < BPF_REG_SIZE; i++)
                                state->stack[spi].slot_type[i] = STACK_MISC;

                /* only mark the slot as written if all 8 bytes were written
                 * otherwise read propagation may incorrectly stop too soon
                 * when stack slots are partially written.
                 * This heuristic means that read propagation will be
                 * conservative, since it will add reg_live_read marks
                 * to stack slots all the way to first state when programs
                 * writes+reads less than 8 bytes
                 */
                if (size == BPF_REG_SIZE)
                        state->stack[spi].spilled_ptr.live |= REG_LIVE_WRITTEN;

                /* when we zero initialize stack slots mark them as such */
                if (reg && register_is_null(reg)) {
                        /* backtracking doesn't work for STACK_ZERO yet. */
                        err = mark_chain_precision(env, value_regno);
                        if (err)
                                return err;
                        type = STACK_ZERO;
                }

                /* Mark slots affected by this stack write. */
                for (i = 0; i < size; i++)
                        state->stack[spi].slot_type[(slot - i) % BPF_REG_SIZE] =
                                type;
        }
        return 0;
}

/* Write the stack: 'stack[ptr_regno + off] = value_regno'. 'ptr_regno' is
 * known to contain a variable offset.
 * This function checks whether the write is permitted and conservatively
 * tracks the effects of the write, considering that each stack slot in the
 * dynamic range is potentially written to.
 *
 * 'off' includes 'regno->off'.
 * 'value_regno' can be -1, meaning that an unknown value is being written to
 * the stack.
 *
 * Spilled pointers in range are not marked as written because we don't know
 * what's going to be actually written. This means that read propagation for
 * future reads cannot be terminated by this write.
 *
 * For privileged programs, uninitialized stack slots are considered
 * initialized by this write (even though we don't know exactly what offsets
 * are going to be written to). The idea is that we don't want the verifier to
 * reject future reads that access slots written to through variable offsets.
 */
static int check_stack_write_var_off(struct bpf_verifier_env *env,
                                     /* func where register points to */
                                     struct bpf_func_state *state,
                                     int ptr_regno, int off, int size,
                                     int value_regno, int insn_idx)
{
        struct bpf_func_state *cur; /* state of the current function */
        int min_off, max_off;
        int i, err;
        struct bpf_reg_state *ptr_reg = NULL, *value_reg = NULL;
        bool writing_zero = false;
        /* set if the fact that we're writing a zero is used to let any
         * stack slots remain STACK_ZERO
         */
        bool zero_used = false;

        cur = env->cur_state->frame[env->cur_state->curframe];
        ptr_reg = &cur->regs[ptr_regno];
        min_off = ptr_reg->smin_value + off;
        max_off = ptr_reg->smax_value + off + size;
        if (value_regno >= 0)
                value_reg = &cur->regs[value_regno];
        if (value_reg && register_is_null(value_reg))
                writing_zero = true;

        err = realloc_func_state(state, round_up(-min_off, BPF_REG_SIZE),
                                 state->acquired_refs, true);
        if (err)
                return err;


        /* Variable offset writes destroy any spilled pointers in range. */
        for (i = min_off; i < max_off; i++) {
                u8 new_type, *stype;
                int slot, spi;

                slot = -i - 1;
                spi = slot / BPF_REG_SIZE;
                stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];

                if (!env->allow_ptr_leaks
                                && *stype != NOT_INIT
                                && *stype != SCALAR_VALUE) {
                        /* Reject the write if there's are spilled pointers in
                         * range. If we didn't reject here, the ptr status
                         * would be erased below (even though not all slots are
                         * actually overwritten), possibly opening the door to
                         * leaks.
                         */
                        verbose(env, "spilled ptr in range of var-offset stack write; insn %d, ptr off: %d",
                                insn_idx, i);
                        return -EINVAL;
                }

                /* Erase all spilled pointers. */
                state->stack[spi].spilled_ptr.type = NOT_INIT;

                /* Update the slot type. */
                new_type = STACK_MISC;
                if (writing_zero && *stype == STACK_ZERO) {
                        new_type = STACK_ZERO;
                        zero_used = true;
                }
                /* If the slot is STACK_INVALID, we check whether it's OK to
                 * pretend that it will be initialized by this write. The slot
                 * might not actually be written to, and so if we mark it as
                 * initialized future reads might leak uninitialized memory.
                 * For privileged programs, we will accept such reads to slots
                 * that may or may not be written because, if we're reject
                 * them, the error would be too confusing.
                 */
                if (*stype == STACK_INVALID && !env->allow_uninit_stack) {
                        verbose(env, "uninit stack in range of var-offset write prohibited for !root; insn %d, off: %d",
                                        insn_idx, i);
                        return -EINVAL;
                }
                *stype = new_type;
        }
        if (zero_used) {
                /* backtracking doesn't work for STACK_ZERO yet. */
                err = mark_chain_precision(env, value_regno);
                if (err)
                        return err;
        }
        return 0;
}

/* When register 'dst_regno' is assigned some values from stack[min_off,
 * max_off), we set the register's type according to the types of the
 * respective stack slots. If all the stack values are known to be zeros, then
 * so is the destination reg. Otherwise, the register is considered to be
 * SCALAR. This function does not deal with register filling; the caller must
 * ensure that all spilled registers in the stack range have been marked as
 * read.
 */
static void mark_reg_stack_read(struct bpf_verifier_env *env,
                                /* func where src register points to */
                                struct bpf_func_state *ptr_state,
                                int min_off, int max_off, int dst_regno)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        int i, slot, spi;
        u8 *stype;
        int zeros = 0;

        for (i = min_off; i < max_off; i++) {
                slot = -i - 1;
                spi = slot / BPF_REG_SIZE;
                stype = ptr_state->stack[spi].slot_type;
                if (stype[slot % BPF_REG_SIZE] != STACK_ZERO)
                        break;
                zeros++;
        }
        if (zeros == max_off - min_off) {
                /* any access_size read into register is zero extended,
                 * so the whole register == const_zero
                 */
                __mark_reg_const_zero(&state->regs[dst_regno]);
                /* backtracking doesn't support STACK_ZERO yet,
                 * so mark it precise here, so that later
                 * backtracking can stop here.
                 * Backtracking may not need this if this register
                 * doesn't participate in pointer adjustment.
                 * Forward propagation of precise flag is not
                 * necessary either. This mark is only to stop
                 * backtracking. Any register that contributed
                 * to const 0 was marked precise before spill.
                 */
                state->regs[dst_regno].precise = true;
        } else {
                /* have read misc data from the stack */
                mark_reg_unknown(env, state->regs, dst_regno);
        }
        state->regs[dst_regno].live |= REG_LIVE_WRITTEN;
}

/* Read the stack at 'off' and put the results into the register indicated by
 * 'dst_regno'. It handles reg filling if the addressed stack slot is a
 * spilled reg.
 *
 * 'dst_regno' can be -1, meaning that the read value is not going to a
 * register.
 *
 * The access is assumed to be within the current stack bounds.
 */
static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
                                      /* func where src register points to */
                                      struct bpf_func_state *reg_state,
                                      int off, int size, int dst_regno)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        int i, slot = -off - 1, spi = slot / BPF_REG_SIZE;
        struct bpf_reg_state *reg;
        u8 *stype;

        stype = reg_state->stack[spi].slot_type;
        reg = &reg_state->stack[spi].spilled_ptr;

        if (stype[0] == STACK_SPILL) {
                if (size != BPF_REG_SIZE) {
                        if (reg->type != SCALAR_VALUE) {
                                verbose_linfo(env, env->insn_idx, "; ");
                                verbose(env, "invalid size of register fill\n");
                                return -EACCES;
                        }
                        if (dst_regno >= 0) {
                                mark_reg_unknown(env, state->regs, dst_regno);
                                state->regs[dst_regno].live |= REG_LIVE_WRITTEN;
                        }
                        mark_reg_read(env, reg, reg->parent, REG_LIVE_READ64);
                        return 0;
                }
                for (i = 1; i < BPF_REG_SIZE; i++) {
                        if (stype[(slot - i) % BPF_REG_SIZE] != STACK_SPILL) {
                                verbose(env, "corrupted spill memory\n");
                                return -EACCES;
                        }
                }

                if (dst_regno >= 0) {
                        /* restore register state from stack */
                        state->regs[dst_regno] = *reg;
                        /* mark reg as written since spilled pointer state likely
                         * has its liveness marks cleared by is_state_visited()
                         * which resets stack/reg liveness for state transitions
                         */
                        state->regs[dst_regno].live |= REG_LIVE_WRITTEN;
                } else if (__is_pointer_value(env->allow_ptr_leaks, reg)) {
                        /* If dst_regno==-1, the caller is asking us whether
                         * it is acceptable to use this value as a SCALAR_VALUE
                         * (e.g. for XADD).
                         * We must not allow unprivileged callers to do that
                         * with spilled pointers.
                         */
                        verbose(env, "leaking pointer from stack off %d\n",
                                off);
                        return -EACCES;
                }
                mark_reg_read(env, reg, reg->parent, REG_LIVE_READ64);
        } else {
                u8 type;

                for (i = 0; i < size; i++) {
                        type = stype[(slot - i) % BPF_REG_SIZE];
                        if (type == STACK_MISC)
                                continue;
                        if (type == STACK_ZERO)
                                continue;
                        verbose(env, "invalid read from stack off %d+%d size %d\n",
                                off, i, size);
                        return -EACCES;
                }
                mark_reg_read(env, reg, reg->parent, REG_LIVE_READ64);
                if (dst_regno >= 0)
                        mark_reg_stack_read(env, reg_state, off, off + size, dst_regno);
        }
        return 0;
}

enum stack_access_src {
        ACCESS_DIRECT = 1,  /* the access is performed by an instruction */
        ACCESS_HELPER = 2,  /* the access is performed by a helper */
};

static int check_stack_range_initialized(struct bpf_verifier_env *env,
                                         int regno, int off, int access_size,
                                         bool zero_size_allowed,
                                         enum stack_access_src type,
                                         struct bpf_call_arg_meta *meta);

static struct bpf_reg_state *reg_state(struct bpf_verifier_env *env, int regno)
{
        return cur_regs(env) + regno;
}

/* Read the stack at 'ptr_regno + off' and put the result into the register
 * 'dst_regno'.
 * 'off' includes the pointer register's fixed offset(i.e. 'ptr_regno.off'),
 * but not its variable offset.
 * 'size' is assumed to be <= reg size and the access is assumed to be aligned.
 *
 * As opposed to check_stack_read_fixed_off, this function doesn't deal with
 * filling registers (i.e. reads of spilled register cannot be detected when
 * the offset is not fixed). We conservatively mark 'dst_regno' as containing
 * SCALAR_VALUE. That's why we assert that the 'ptr_regno' has a variable
 * offset; for a fixed offset check_stack_read_fixed_off should be used
 * instead.
 */
static int check_stack_read_var_off(struct bpf_verifier_env *env,
                                    int ptr_regno, int off, int size, int dst_regno)
{
        /* The state of the source register. */
        struct bpf_reg_state *reg = reg_state(env, ptr_regno);
        struct bpf_func_state *ptr_state = func(env, reg);
        int err;
        int min_off, max_off;

        /* Note that we pass a NULL meta, so raw access will not be permitted.
         */
        err = check_stack_range_initialized(env, ptr_regno, off, size,
                                            false, ACCESS_DIRECT, NULL);
        if (err)
                return err;

        min_off = reg->smin_value + off;
        max_off = reg->smax_value + off;
        mark_reg_stack_read(env, ptr_state, min_off, max_off + size, dst_regno);
        return 0;
}

/* check_stack_read dispatches to check_stack_read_fixed_off or
 * check_stack_read_var_off.
 *
 * The caller must ensure that the offset falls within the allocated stack
 * bounds.
 *
 * 'dst_regno' is a register which will receive the value from the stack. It
 * can be -1, meaning that the read value is not going to a register.
 */
static int check_stack_read(struct bpf_verifier_env *env,
                            int ptr_regno, int off, int size,
                            int dst_regno)
{
        struct bpf_reg_state *reg = reg_state(env, ptr_regno);
        struct bpf_func_state *state = func(env, reg);
        int err;
        /* Some accesses are only permitted with a static offset. */
        bool var_off = !tnum_is_const(reg->var_off);

        /* The offset is required to be static when reads don't go to a
         * register, in order to not leak pointers (see
         * check_stack_read_fixed_off).
         */
        if (dst_regno < 0 && var_off) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "variable offset stack pointer cannot be passed into helper function; var_off=%s off=%d size=%d\n",
                        tn_buf, off, size);
                return -EACCES;
        }
        /* Variable offset is prohibited for unprivileged mode for simplicity
         * since it requires corresponding support in Spectre masking for stack
         * ALU. See also retrieve_ptr_limit().
         */
        if (!env->bypass_spec_v1 && var_off) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "R%d variable offset stack access prohibited for !root, var_off=%s\n",
                                ptr_regno, tn_buf);
                return -EACCES;
        }

        if (!var_off) {
                off += reg->var_off.value;
                err = check_stack_read_fixed_off(env, state, off, size,
                                                 dst_regno);
        } else {
                /* Variable offset stack reads need more conservative handling
                 * than fixed offset ones. Note that dst_regno >= 0 on this
                 * branch.
                 */
                err = check_stack_read_var_off(env, ptr_regno, off, size,
                                               dst_regno);
        }
        return err;
}


/* check_stack_write dispatches to check_stack_write_fixed_off or
 * check_stack_write_var_off.
 *
 * 'ptr_regno' is the register used as a pointer into the stack.
 * 'off' includes 'ptr_regno->off', but not its variable offset (if any).
 * 'value_regno' is the register whose value we're writing to the stack. It can
 * be -1, meaning that we're not writing from a register.
 *
 * The caller must ensure that the offset falls within the maximum stack size.
 */
static int check_stack_write(struct bpf_verifier_env *env,
                             int ptr_regno, int off, int size,
                             int value_regno, int insn_idx)
{
        struct bpf_reg_state *reg = reg_state(env, ptr_regno);
        struct bpf_func_state *state = func(env, reg);
        int err;

        if (tnum_is_const(reg->var_off)) {
                off += reg->var_off.value;
                err = check_stack_write_fixed_off(env, state, off, size,
                                                  value_regno, insn_idx);
        } else {
                /* Variable offset stack reads need more conservative handling
                 * than fixed offset ones.
                 */
                err = check_stack_write_var_off(env, state,
                                                ptr_regno, off, size,
                                                value_regno, insn_idx);
        }
        return err;
}

static int check_map_access_type(struct bpf_verifier_env *env, u32 regno,
                                 int off, int size, enum bpf_access_type type)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_map *map = regs[regno].map_ptr;
        u32 cap = bpf_map_flags_to_cap(map);

        if (type == BPF_WRITE && !(cap & BPF_MAP_CAN_WRITE)) {
                verbose(env, "write into map forbidden, value_size=%d off=%d size=%d\n",
                        map->value_size, off, size);
                return -EACCES;
        }

        if (type == BPF_READ && !(cap & BPF_MAP_CAN_READ)) {
                verbose(env, "read from map forbidden, value_size=%d off=%d size=%d\n",
                        map->value_size, off, size);
                return -EACCES;
        }

        return 0;
}

/* check read/write into memory region (e.g., map value, ringbuf sample, etc) */
static int __check_mem_access(struct bpf_verifier_env *env, int regno,
                              int off, int size, u32 mem_size,
                              bool zero_size_allowed)
{
        bool size_ok = size > 0 || (size == 0 && zero_size_allowed);
        struct bpf_reg_state *reg;

        if (off >= 0 && size_ok && (u64)off + size <= mem_size)
                return 0;

        reg = &cur_regs(env)[regno];
        switch (reg->type) {
        case PTR_TO_MAP_KEY:
                verbose(env, "invalid access to map key, key_size=%d off=%d size=%d\n",
                        mem_size, off, size);
                break;
        case PTR_TO_MAP_VALUE:
                verbose(env, "invalid access to map value, value_size=%d off=%d size=%d\n",
                        mem_size, off, size);
                break;
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET_END:
                verbose(env, "invalid access to packet, off=%d size=%d, R%d(id=%d,off=%d,r=%d)\n",
                        off, size, regno, reg->id, off, mem_size);
                break;
        case PTR_TO_MEM:
        default:
                verbose(env, "invalid access to memory, mem_size=%u off=%d size=%d\n",
                        mem_size, off, size);
        }

        return -EACCES;
}

/* check read/write into a memory region with possible variable offset */
static int check_mem_region_access(struct bpf_verifier_env *env, u32 regno,
                                   int off, int size, u32 mem_size,
                                   bool zero_size_allowed)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *reg = &state->regs[regno];
        int err;

        /* We may have adjusted the register pointing to memory region, so we
         * need to try adding each of min_value and max_value to off
         * to make sure our theoretical access will be safe.
         */
        if (env->log.level & BPF_LOG_LEVEL)
                print_verifier_state(env, state);

        /* The minimum value is only important with signed
         * comparisons where we can't assume the floor of a
         * value is 0.  If we are using signed variables for our
         * index'es we need to make sure that whatever we use
         * will have a set floor within our range.
         */
        if (reg->smin_value < 0 &&
            (reg->smin_value == S64_MIN ||
             (off + reg->smin_value != (s64)(s32)(off + reg->smin_value)) ||
              reg->smin_value + off < 0)) {
                verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
                        regno);
                return -EACCES;
        }
        err = __check_mem_access(env, regno, reg->smin_value + off, size,
                                 mem_size, zero_size_allowed);
        if (err) {
                verbose(env, "R%d min value is outside of the allowed memory range\n",
                        regno);
                return err;
        }

        /* If we haven't set a max value then we need to bail since we can't be
         * sure we won't do bad things.
         * If reg->umax_value + off could overflow, treat that as unbounded too.
         */
        if (reg->umax_value >= BPF_MAX_VAR_OFF) {
                verbose(env, "R%d unbounded memory access, make sure to bounds check any such access\n",
                        regno);
                return -EACCES;
        }
        err = __check_mem_access(env, regno, reg->umax_value + off, size,
                                 mem_size, zero_size_allowed);
        if (err) {
                verbose(env, "R%d max value is outside of the allowed memory range\n",
                        regno);
                return err;
        }

        return 0;
}

/* check read/write into a map element with possible variable offset */
static int check_map_access(struct bpf_verifier_env *env, u32 regno,
                            int off, int size, bool zero_size_allowed)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *reg = &state->regs[regno];
        struct bpf_map *map = reg->map_ptr;
        int err;

        err = check_mem_region_access(env, regno, off, size, map->value_size,
                                      zero_size_allowed);
        if (err)
                return err;

        if (map_value_has_spin_lock(map)) {
                u32 lock = map->spin_lock_off;

                /* if any part of struct bpf_spin_lock can be touched by
                 * load/store reject this program.
                 * To check that [x1, x2) overlaps with [y1, y2)
                 * it is sufficient to check x1 < y2 && y1 < x2.
                 */
                if (reg->smin_value + off < lock + sizeof(struct bpf_spin_lock) &&
                     lock < reg->umax_value + off + size) {
                        verbose(env, "bpf_spin_lock cannot be accessed directly by load/store\n");
                        return -EACCES;
                }
        }
        return err;
}

#define MAX_PACKET_OFF 0xffff

static enum bpf_prog_type resolve_prog_type(struct bpf_prog *prog)
{
        return prog->aux->dst_prog ? prog->aux->dst_prog->type : prog->type;
}

static bool may_access_direct_pkt_data(struct bpf_verifier_env *env,
                                       const struct bpf_call_arg_meta *meta,
                                       enum bpf_access_type t)
{
        enum bpf_prog_type prog_type = resolve_prog_type(env->prog);

        switch (prog_type) {
        /* Program types only with direct read access go here! */
        case BPF_PROG_TYPE_LWT_IN:
        case BPF_PROG_TYPE_LWT_OUT:
        case BPF_PROG_TYPE_LWT_SEG6LOCAL:
        case BPF_PROG_TYPE_SK_REUSEPORT:
        case BPF_PROG_TYPE_FLOW_DISSECTOR:
        case BPF_PROG_TYPE_CGROUP_SKB:
                if (t == BPF_WRITE)
                        return false;
                fallthrough;

        /* Program types with direct read + write access go here! */
        case BPF_PROG_TYPE_SCHED_CLS:
        case BPF_PROG_TYPE_SCHED_ACT:
        case BPF_PROG_TYPE_XDP:
        case BPF_PROG_TYPE_LWT_XMIT:
        case BPF_PROG_TYPE_SK_SKB:
        case BPF_PROG_TYPE_SK_MSG:
                if (meta)
                        return meta->pkt_access;

                env->seen_direct_write = true;
                return true;

        case BPF_PROG_TYPE_CGROUP_SOCKOPT:
                if (t == BPF_WRITE)
                        env->seen_direct_write = true;

                return true;

        default:
                return false;
        }
}

static int check_packet_access(struct bpf_verifier_env *env, u32 regno, int off,
                               int size, bool zero_size_allowed)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = &regs[regno];
        int err;

        /* We may have added a variable offset to the packet pointer; but any
         * reg->range we have comes after that.  We are only checking the fixed
         * offset.
         */

        /* We don't allow negative numbers, because we aren't tracking enough
         * detail to prove they're safe.
         */
        if (reg->smin_value < 0) {
                verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
                        regno);
                return -EACCES;
        }

        err = reg->range < 0 ? -EINVAL :
              __check_mem_access(env, regno, off, size, reg->range,
                                 zero_size_allowed);
        if (err) {
                verbose(env, "R%d offset is outside of the packet\n", regno);
                return err;
        }

        /* __check_mem_access has made sure "off + size - 1" is within u16.
         * reg->umax_value can't be bigger than MAX_PACKET_OFF which is 0xffff,
         * otherwise find_good_pkt_pointers would have refused to set range info
         * that __check_mem_access would have rejected this pkt access.
         * Therefore, "off + reg->umax_value + size - 1" won't overflow u32.
         */
        env->prog->aux->max_pkt_offset =
                max_t(u32, env->prog->aux->max_pkt_offset,
                      off + reg->umax_value + size - 1);

        return err;
}

/* check access to 'struct bpf_context' fields.  Supports fixed offsets only */
static int check_ctx_access(struct bpf_verifier_env *env, int insn_idx, int off, int size,
                            enum bpf_access_type t, enum bpf_reg_type *reg_type,
                            struct btf **btf, u32 *btf_id)
{
        struct bpf_insn_access_aux info = {
                .reg_type = *reg_type,
                .log = &env->log,
        };

        if (env->ops->is_valid_access &&
            env->ops->is_valid_access(off, size, t, env->prog, &info)) {
                /* A non zero info.ctx_field_size indicates that this field is a
                 * candidate for later verifier transformation to load the whole
                 * field and then apply a mask when accessed with a narrower
                 * access than actual ctx access size. A zero info.ctx_field_size
                 * will only allow for whole field access and rejects any other
                 * type of narrower access.
                 */
                *reg_type = info.reg_type;

                if (*reg_type == PTR_TO_BTF_ID || *reg_type == PTR_TO_BTF_ID_OR_NULL) {
                        *btf = info.btf;
                        *btf_id = info.btf_id;
                } else {
                        env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size;
                }
                /* remember the offset of last byte accessed in ctx */
                if (env->prog->aux->max_ctx_offset < off + size)
                        env->prog->aux->max_ctx_offset = off + size;
                return 0;
        }

        verbose(env, "invalid bpf_context access off=%d size=%d\n", off, size);
        return -EACCES;
}

static int check_flow_keys_access(struct bpf_verifier_env *env, int off,
                                  int size)
{
        if (size < 0 || off < 0 ||
            (u64)off + size > sizeof(struct bpf_flow_keys)) {
                verbose(env, "invalid access to flow keys off=%d size=%d\n",
                        off, size);
                return -EACCES;
        }
        return 0;
}

static int check_sock_access(struct bpf_verifier_env *env, int insn_idx,
                             u32 regno, int off, int size,
                             enum bpf_access_type t)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = &regs[regno];
        struct bpf_insn_access_aux info = {};
        bool valid;

        if (reg->smin_value < 0) {
                verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n",
                        regno);
                return -EACCES;
        }

        switch (reg->type) {
        case PTR_TO_SOCK_COMMON:
                valid = bpf_sock_common_is_valid_access(off, size, t, &info);
                break;
        case PTR_TO_SOCKET:
                valid = bpf_sock_is_valid_access(off, size, t, &info);
                break;
        case PTR_TO_TCP_SOCK:
                valid = bpf_tcp_sock_is_valid_access(off, size, t, &info);
                break;
        case PTR_TO_XDP_SOCK:
                valid = bpf_xdp_sock_is_valid_access(off, size, t, &info);
                break;
        default:
                valid = false;
        }


        if (valid) {
                env->insn_aux_data[insn_idx].ctx_field_size =
                        info.ctx_field_size;
                return 0;
        }

        verbose(env, "R%d invalid %s access off=%d size=%d\n",
                regno, reg_type_str[reg->type], off, size);

        return -EACCES;
}

static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
{
        return __is_pointer_value(env->allow_ptr_leaks, reg_state(env, regno));
}

static bool is_ctx_reg(struct bpf_verifier_env *env, int regno)
{
        const struct bpf_reg_state *reg = reg_state(env, regno);

        return reg->type == PTR_TO_CTX;
}

static bool is_sk_reg(struct bpf_verifier_env *env, int regno)
{
        const struct bpf_reg_state *reg = reg_state(env, regno);

        return type_is_sk_pointer(reg->type);
}

static bool is_pkt_reg(struct bpf_verifier_env *env, int regno)
{
        const struct bpf_reg_state *reg = reg_state(env, regno);

        return type_is_pkt_pointer(reg->type);
}

static bool is_flow_key_reg(struct bpf_verifier_env *env, int regno)
{
        const struct bpf_reg_state *reg = reg_state(env, regno);

        /* Separate to is_ctx_reg() since we still want to allow BPF_ST here. */
        return reg->type == PTR_TO_FLOW_KEYS;
}

static int check_pkt_ptr_alignment(struct bpf_verifier_env *env,
                                   const struct bpf_reg_state *reg,
                                   int off, int size, bool strict)
{
        struct tnum reg_off;
        int ip_align;

        /* Byte size accesses are always allowed. */
        if (!strict || size == 1)
                return 0;

        /* For platforms that do not have a Kconfig enabling
         * CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS the value of
         * NET_IP_ALIGN is universally set to '2'.  And on platforms
         * that do set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, we get
         * to this code only in strict mode where we want to emulate
         * the NET_IP_ALIGN==2 checking.  Therefore use an
         * unconditional IP align value of '2'.
         */
        ip_align = 2;

        reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env,
                        "misaligned packet access off %d+%s+%d+%d size %d\n",
                        ip_align, tn_buf, reg->off, off, size);
                return -EACCES;
        }

        return 0;
}

static int check_generic_ptr_alignment(struct bpf_verifier_env *env,
                                       const struct bpf_reg_state *reg,
                                       const char *pointer_desc,
                                       int off, int size, bool strict)
{
        struct tnum reg_off;

        /* Byte size accesses are always allowed. */
        if (!strict || size == 1)
                return 0;

        reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));
        if (!tnum_is_aligned(reg_off, size)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "misaligned %saccess off %s+%d+%d size %d\n",
                        pointer_desc, tn_buf, reg->off, off, size);
                return -EACCES;
        }

        return 0;
}

static int check_ptr_alignment(struct bpf_verifier_env *env,
                               const struct bpf_reg_state *reg, int off,
                               int size, bool strict_alignment_once)
{
        bool strict = env->strict_alignment || strict_alignment_once;
        const char *pointer_desc = "";

        switch (reg->type) {
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
                /* Special case, because of NET_IP_ALIGN. Given metadata sits
                 * right in front, treat it the very same way.
                 */
                return check_pkt_ptr_alignment(env, reg, off, size, strict);
        case PTR_TO_FLOW_KEYS:
                pointer_desc = "flow keys ";
                break;
        case PTR_TO_MAP_KEY:
                pointer_desc = "key ";
                break;
        case PTR_TO_MAP_VALUE:
                pointer_desc = "value ";
                break;
        case PTR_TO_CTX:
                pointer_desc = "context ";
                break;
        case PTR_TO_STACK:
                pointer_desc = "stack ";
                /* The stack spill tracking logic in check_stack_write_fixed_off()
                 * and check_stack_read_fixed_off() relies on stack accesses being
                 * aligned.
                 */
                strict = true;
                break;
        case PTR_TO_SOCKET:
                pointer_desc = "sock ";
                break;
        case PTR_TO_SOCK_COMMON:
                pointer_desc = "sock_common ";
                break;
        case PTR_TO_TCP_SOCK:
                pointer_desc = "tcp_sock ";
                break;
        case PTR_TO_XDP_SOCK:
                pointer_desc = "xdp_sock ";
                break;
        default:
                break;
        }
        return check_generic_ptr_alignment(env, reg, pointer_desc, off, size,
                                           strict);
}

static int update_stack_depth(struct bpf_verifier_env *env,
                              const struct bpf_func_state *func,
                              int off)
{
        u16 stack = env->subprog_info[func->subprogno].stack_depth;

        if (stack >= -off)
                return 0;

        /* update known max for given subprogram */
        env->subprog_info[func->subprogno].stack_depth = -off;
        return 0;
}

/* starting from main bpf function walk all instructions of the function
 * and recursively walk all callees that given function can call.
 * Ignore jump and exit insns.
 * Since recursion is prevented by check_cfg() this algorithm
 * only needs a local stack of MAX_CALL_FRAMES to remember callsites
 */
static int check_max_stack_depth(struct bpf_verifier_env *env)
{
        int depth = 0, frame = 0, idx = 0, i = 0, subprog_end;
        struct bpf_subprog_info *subprog = env->subprog_info;
        struct bpf_insn *insn = env->prog->insnsi;
        bool tail_call_reachable = false;
        int ret_insn[MAX_CALL_FRAMES];
        int ret_prog[MAX_CALL_FRAMES];
        int j;

process_func:
        /* protect against potential stack overflow that might happen when
         * bpf2bpf calls get combined with tailcalls. Limit the caller's stack
         * depth for such case down to 256 so that the worst case scenario
         * would result in 8k stack size (32 which is tailcall limit * 256 =
         * 8k).
         *
         * To get the idea what might happen, see an example:
         * func1 -> sub rsp, 128
         *  subfunc1 -> sub rsp, 256
         *  tailcall1 -> add rsp, 256
         *   func2 -> sub rsp, 192 (total stack size = 128 + 192 = 320)
         *   subfunc2 -> sub rsp, 64
         *   subfunc22 -> sub rsp, 128
         *   tailcall2 -> add rsp, 128
         *    func3 -> sub rsp, 32 (total stack size 128 + 192 + 64 + 32 = 416)
         *
         * tailcall will unwind the current stack frame but it will not get rid
         * of caller's stack as shown on the example above.
         */
        if (idx && subprog[idx].has_tail_call && depth >= 256) {
                verbose(env,
                        "tail_calls are not allowed when call stack of previous frames is %d bytes. Too large\n",
                        depth);
                return -EACCES;
        }
        /* round up to 32-bytes, since this is granularity
         * of interpreter stack size
         */
        depth += round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
        if (depth > MAX_BPF_STACK) {
                verbose(env, "combined stack size of %d calls is %d. Too large\n",
                        frame + 1, depth);
                return -EACCES;
        }
continue_func:
        subprog_end = subprog[idx + 1].start;
        for (; i < subprog_end; i++) {
                if (!bpf_pseudo_call(insn + i) && !bpf_pseudo_func(insn + i))
                        continue;
                /* remember insn and function to return to */
                ret_insn[frame] = i + 1;
                ret_prog[frame] = idx;

                /* find the callee */
                i = i + insn[i].imm + 1;
                idx = find_subprog(env, i);
                if (idx < 0) {
                        WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
                                  i);
                        return -EFAULT;
                }

                if (subprog[idx].has_tail_call)
                        tail_call_reachable = true;

                frame++;
                if (frame >= MAX_CALL_FRAMES) {
                        verbose(env, "the call stack of %d frames is too deep !\n",
                                frame);
                        return -E2BIG;
                }
                goto process_func;
        }
        /* if tail call got detected across bpf2bpf calls then mark each of the
         * currently present subprog frames as tail call reachable subprogs;
         * this info will be utilized by JIT so that we will be preserving the
         * tail call counter throughout bpf2bpf calls combined with tailcalls
         */
        if (tail_call_reachable)
                for (j = 0; j < frame; j++)
                        subprog[ret_prog[j]].tail_call_reachable = true;

        /* end of for() loop means the last insn of the 'subprog'
         * was reached. Doesn't matter whether it was JA or EXIT
         */
        if (frame == 0)
                return 0;
        depth -= round_up(max_t(u32, subprog[idx].stack_depth, 1), 32);
        frame--;
        i = ret_insn[frame];
        idx = ret_prog[frame];
        goto continue_func;
}

#ifndef CONFIG_BPF_JIT_ALWAYS_ON
static int get_callee_stack_depth(struct bpf_verifier_env *env,
                                  const struct bpf_insn *insn, int idx)
{
        int start = idx + insn->imm + 1, subprog;

        subprog = find_subprog(env, start);
        if (subprog < 0) {
                WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
                          start);
                return -EFAULT;
        }
        return env->subprog_info[subprog].stack_depth;
}
#endif

int check_ctx_reg(struct bpf_verifier_env *env,
                  const struct bpf_reg_state *reg, int regno)
{
        /* Access to ctx or passing it to a helper is only allowed in
         * its original, unmodified form.
         */

        if (reg->off) {
                verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
                        regno, reg->off);
                return -EACCES;
        }

        if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
                return -EACCES;
        }

        return 0;
}

static int __check_buffer_access(struct bpf_verifier_env *env,
                                 const char *buf_info,
                                 const struct bpf_reg_state *reg,
                                 int regno, int off, int size)
{
        if (off < 0) {
                verbose(env,
                        "R%d invalid %s buffer access: off=%d, size=%d\n",
                        regno, buf_info, off, size);
                return -EACCES;
        }
        if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env,
                        "R%d invalid variable buffer offset: off=%d, var_off=%s\n",
                        regno, off, tn_buf);
                return -EACCES;
        }

        return 0;
}

static int check_tp_buffer_access(struct bpf_verifier_env *env,
                                  const struct bpf_reg_state *reg,
                                  int regno, int off, int size)
{
        int err;

        err = __check_buffer_access(env, "tracepoint", reg, regno, off, size);
        if (err)
                return err;

        if (off + size > env->prog->aux->max_tp_access)
                env->prog->aux->max_tp_access = off + size;

        return 0;
}

static int check_buffer_access(struct bpf_verifier_env *env,
                               const struct bpf_reg_state *reg,
                               int regno, int off, int size,
                               bool zero_size_allowed,
                               const char *buf_info,
                               u32 *max_access)
{
        int err;

        err = __check_buffer_access(env, buf_info, reg, regno, off, size);
        if (err)
                return err;

        if (off + size > *max_access)
                *max_access = off + size;

        return 0;
}

/* BPF architecture zero extends alu32 ops into 64-bit registesr */
static void zext_32_to_64(struct bpf_reg_state *reg)
{
        reg->var_off = tnum_subreg(reg->var_off);
        __reg_assign_32_into_64(reg);
}

/* truncate register to smaller size (in bytes)
 * must be called with size < BPF_REG_SIZE
 */
static void coerce_reg_to_size(struct bpf_reg_state *reg, int size)
{
        u64 mask;

        /* clear high bits in bit representation */
        reg->var_off = tnum_cast(reg->var_off, size);

        /* fix arithmetic bounds */
        mask = ((u64)1 << (size * 8)) - 1;
        if ((reg->umin_value & ~mask) == (reg->umax_value & ~mask)) {
                reg->umin_value &= mask;
                reg->umax_value &= mask;
        } else {
                reg->umin_value = 0;
                reg->umax_value = mask;
        }
        reg->smin_value = reg->umin_value;
        reg->smax_value = reg->umax_value;

        /* If size is smaller than 32bit register the 32bit register
         * values are also truncated so we push 64-bit bounds into
         * 32-bit bounds. Above were truncated < 32-bits already.
         */
        if (size >= 4)
                return;
        __reg_combine_64_into_32(reg);
}

static bool bpf_map_is_rdonly(const struct bpf_map *map)
{
        return (map->map_flags & BPF_F_RDONLY_PROG) && map->frozen;
}

static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val)
{
        void *ptr;
        u64 addr;
        int err;

        err = map->ops->map_direct_value_addr(map, &addr, off);
        if (err)
                return err;
        ptr = (void *)(long)addr + off;

        switch (size) {
        case sizeof(u8):
                *val = (u64)*(u8 *)ptr;
                break;
        case sizeof(u16):
                *val = (u64)*(u16 *)ptr;
                break;
        case sizeof(u32):
                *val = (u64)*(u32 *)ptr;
                break;
        case sizeof(u64):
                *val = *(u64 *)ptr;
                break;
        default:
                return -EINVAL;
        }
        return 0;
}

static int check_ptr_to_btf_access(struct bpf_verifier_env *env,
                                   struct bpf_reg_state *regs,
                                   int regno, int off, int size,
                                   enum bpf_access_type atype,
                                   int value_regno)
{
        struct bpf_reg_state *reg = regs + regno;
        const struct btf_type *t = btf_type_by_id(reg->btf, reg->btf_id);
        const char *tname = btf_name_by_offset(reg->btf, t->name_off);
        u32 btf_id;
        int ret;

        if (off < 0) {
                verbose(env,
                        "R%d is ptr_%s invalid negative access: off=%d\n",
                        regno, tname, off);
                return -EACCES;
        }
        if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env,
                        "R%d is ptr_%s invalid variable offset: off=%d, var_off=%s\n",
                        regno, tname, off, tn_buf);
                return -EACCES;
        }

        if (env->ops->btf_struct_access) {
                ret = env->ops->btf_struct_access(&env->log, reg->btf, t,
                                                  off, size, atype, &btf_id);
        } else {
                if (atype != BPF_READ) {
                        verbose(env, "only read is supported\n");
                        return -EACCES;
                }

                ret = btf_struct_access(&env->log, reg->btf, t, off, size,
                                        atype, &btf_id);
        }

        if (ret < 0)
                return ret;

        if (atype == BPF_READ && value_regno >= 0)
                mark_btf_ld_reg(env, regs, value_regno, ret, reg->btf, btf_id);

        return 0;
}

static int check_ptr_to_map_access(struct bpf_verifier_env *env,
                                   struct bpf_reg_state *regs,
                                   int regno, int off, int size,
                                   enum bpf_access_type atype,
                                   int value_regno)
{
        struct bpf_reg_state *reg = regs + regno;
        struct bpf_map *map = reg->map_ptr;
        const struct btf_type *t;
        const char *tname;
        u32 btf_id;
        int ret;

        if (!btf_vmlinux) {
                verbose(env, "map_ptr access not supported without CONFIG_DEBUG_INFO_BTF\n");
                return -ENOTSUPP;
        }

        if (!map->ops->map_btf_id || !*map->ops->map_btf_id) {
                verbose(env, "map_ptr access not supported for map type %d\n",
                        map->map_type);
                return -ENOTSUPP;
        }

        t = btf_type_by_id(btf_vmlinux, *map->ops->map_btf_id);
        tname = btf_name_by_offset(btf_vmlinux, t->name_off);

        if (!env->allow_ptr_to_map_access) {
                verbose(env,
                        "%s access is allowed only to CAP_PERFMON and CAP_SYS_ADMIN\n",
                        tname);
                return -EPERM;
        }

        if (off < 0) {
                verbose(env, "R%d is %s invalid negative access: off=%d\n",
                        regno, tname, off);
                return -EACCES;
        }

        if (atype != BPF_READ) {
                verbose(env, "only read from %s is supported\n", tname);
                return -EACCES;
        }

        ret = btf_struct_access(&env->log, btf_vmlinux, t, off, size, atype, &btf_id);
        if (ret < 0)
                return ret;

        if (value_regno >= 0)
                mark_btf_ld_reg(env, regs, value_regno, ret, btf_vmlinux, btf_id);

        return 0;
}

/* Check that the stack access at the given offset is within bounds. The
 * maximum valid offset is -1.
 *
 * The minimum valid offset is -MAX_BPF_STACK for writes, and
 * -state->allocated_stack for reads.
 */
static int check_stack_slot_within_bounds(int off,
                                          struct bpf_func_state *state,
                                          enum bpf_access_type t)
{
        int min_valid_off;

        if (t == BPF_WRITE)
                min_valid_off = -MAX_BPF_STACK;
        else
                min_valid_off = -state->allocated_stack;

        if (off < min_valid_off || off > -1)
                return -EACCES;
        return 0;
}

/* Check that the stack access at 'regno + off' falls within the maximum stack
 * bounds.
 *
 * 'off' includes `regno->offset`, but not its dynamic part (if any).
 */
static int check_stack_access_within_bounds(
                struct bpf_verifier_env *env,
                int regno, int off, int access_size,
                enum stack_access_src src, enum bpf_access_type type)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = regs + regno;
        struct bpf_func_state *state = func(env, reg);
        int min_off, max_off;
        int err;
        char *err_extra;

        if (src == ACCESS_HELPER)
                /* We don't know if helpers are reading or writing (or both). */
                err_extra = " indirect access to";
        else if (type == BPF_READ)
                err_extra = " read from";
        else
                err_extra = " write to";

        if (tnum_is_const(reg->var_off)) {
                min_off = reg->var_off.value + off;
                if (access_size > 0)
                        max_off = min_off + access_size - 1;
                else
                        max_off = min_off;
        } else {
                if (reg->smax_value >= BPF_MAX_VAR_OFF ||
                    reg->smin_value <= -BPF_MAX_VAR_OFF) {
                        verbose(env, "invalid unbounded variable-offset%s stack R%d\n",
                                err_extra, regno);
                        return -EACCES;
                }
                min_off = reg->smin_value + off;
                if (access_size > 0)
                        max_off = reg->smax_value + off + access_size - 1;
                else
                        max_off = min_off;
        }

        err = check_stack_slot_within_bounds(min_off, state, type);
        if (!err)
                err = check_stack_slot_within_bounds(max_off, state, type);

        if (err) {
                if (tnum_is_const(reg->var_off)) {
                        verbose(env, "invalid%s stack R%d off=%d size=%d\n",
                                err_extra, regno, off, access_size);
                } else {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env, "invalid variable-offset%s stack R%d var_off=%s size=%d\n",
                                err_extra, regno, tn_buf, access_size);
                }
        }
        return err;
}

/* check whether memory at (regno + off) is accessible for t = (read | write)
 * if t==write, value_regno is a register which value is stored into memory
 * if t==read, value_regno is a register which will receive the value from memory
 * if t==write && value_regno==-1, some unknown value is stored into memory
 * if t==read && value_regno==-1, don't care what we read from memory
 */
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno,
                            int off, int bpf_size, enum bpf_access_type t,
                            int value_regno, bool strict_alignment_once)
{
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *reg = regs + regno;
        struct bpf_func_state *state;
        int size, err = 0;

        size = bpf_size_to_bytes(bpf_size);
        if (size < 0)
                return size;

        /* alignment checks will add in reg->off themselves */
        err = check_ptr_alignment(env, reg, off, size, strict_alignment_once);
        if (err)
                return err;

        /* for access checks, reg->off is just part of off */
        off += reg->off;

        if (reg->type == PTR_TO_MAP_KEY) {
                if (t == BPF_WRITE) {
                        verbose(env, "write to change key R%d not allowed\n", regno);
                        return -EACCES;
                }

                err = check_mem_region_access(env, regno, off, size,
                                              reg->map_ptr->key_size, false);
                if (err)
                        return err;
                if (value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_MAP_VALUE) {
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into map\n", value_regno);
                        return -EACCES;
                }
                err = check_map_access_type(env, regno, off, size, t);
                if (err)
                        return err;
                err = check_map_access(env, regno, off, size, false);
                if (!err && t == BPF_READ && value_regno >= 0) {
                        struct bpf_map *map = reg->map_ptr;

                        /* if map is read-only, track its contents as scalars */
                        if (tnum_is_const(reg->var_off) &&
                            bpf_map_is_rdonly(map) &&
                            map->ops->map_direct_value_addr) {
                                int map_off = off + reg->var_off.value;
                                u64 val = 0;

                                err = bpf_map_direct_read(map, map_off, size,
                                                          &val);
                                if (err)
                                        return err;

                                regs[value_regno].type = SCALAR_VALUE;
                                __mark_reg_known(&regs[value_regno], val);
                        } else {
                                mark_reg_unknown(env, regs, value_regno);
                        }
                }
        } else if (reg->type == PTR_TO_MEM) {
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into mem\n", value_regno);
                        return -EACCES;
                }
                err = check_mem_region_access(env, regno, off, size,
                                              reg->mem_size, false);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_CTX) {
                enum bpf_reg_type reg_type = SCALAR_VALUE;
                struct btf *btf = NULL;
                u32 btf_id = 0;

                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into ctx\n", value_regno);
                        return -EACCES;
                }

                err = check_ctx_reg(env, reg, regno);
                if (err < 0)
                        return err;

                err = check_ctx_access(env, insn_idx, off, size, t, &reg_type, &btf, &btf_id);
                if (err)
                        verbose_linfo(env, insn_idx, "; ");
                if (!err && t == BPF_READ && value_regno >= 0) {
                        /* ctx access returns either a scalar, or a
                         * PTR_TO_PACKET[_META,_END]. In the latter
                         * case, we know the offset is zero.
                         */
                        if (reg_type == SCALAR_VALUE) {
                                mark_reg_unknown(env, regs, value_regno);
                        } else {
                                mark_reg_known_zero(env, regs,
                                                    value_regno);
                                if (reg_type_may_be_null(reg_type))
                                        regs[value_regno].id = ++env->id_gen;
                                /* A load of ctx field could have different
                                 * actual load size with the one encoded in the
                                 * insn. When the dst is PTR, it is for sure not
                                 * a sub-register.
                                 */
                                regs[value_regno].subreg_def = DEF_NOT_SUBREG;
                                if (reg_type == PTR_TO_BTF_ID ||
                                    reg_type == PTR_TO_BTF_ID_OR_NULL) {
                                        regs[value_regno].btf = btf;
                                        regs[value_regno].btf_id = btf_id;
                                }
                        }
                        regs[value_regno].type = reg_type;
                }

        } else if (reg->type == PTR_TO_STACK) {
                /* Basic bounds checks. */
                err = check_stack_access_within_bounds(env, regno, off, size, ACCESS_DIRECT, t);
                if (err)
                        return err;

                state = func(env, reg);
                err = update_stack_depth(env, state, off);
                if (err)
                        return err;

                if (t == BPF_READ)
                        err = check_stack_read(env, regno, off, size,
                                               value_regno);
                else
                        err = check_stack_write(env, regno, off, size,
                                                value_regno, insn_idx);
        } else if (reg_is_pkt_pointer(reg)) {
                if (t == BPF_WRITE && !may_access_direct_pkt_data(env, NULL, t)) {
                        verbose(env, "cannot write into packet\n");
                        return -EACCES;
                }
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into packet\n",
                                value_regno);
                        return -EACCES;
                }
                err = check_packet_access(env, regno, off, size, false);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_FLOW_KEYS) {
                if (t == BPF_WRITE && value_regno >= 0 &&
                    is_pointer_value(env, value_regno)) {
                        verbose(env, "R%d leaks addr into flow keys\n",
                                value_regno);
                        return -EACCES;
                }

                err = check_flow_keys_access(env, off, size);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (type_is_sk_pointer(reg->type)) {
                if (t == BPF_WRITE) {
                        verbose(env, "R%d cannot write into %s\n",
                                regno, reg_type_str[reg->type]);
                        return -EACCES;
                }
                err = check_sock_access(env, insn_idx, regno, off, size, t);
                if (!err && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_TP_BUFFER) {
                err = check_tp_buffer_access(env, reg, regno, off, size);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_BTF_ID) {
                err = check_ptr_to_btf_access(env, regs, regno, off, size, t,
                                              value_regno);
        } else if (reg->type == CONST_PTR_TO_MAP) {
                err = check_ptr_to_map_access(env, regs, regno, off, size, t,
                                              value_regno);
        } else if (reg->type == PTR_TO_RDONLY_BUF) {
                if (t == BPF_WRITE) {
                        verbose(env, "R%d cannot write into %s\n",
                                regno, reg_type_str[reg->type]);
                        return -EACCES;
                }
                err = check_buffer_access(env, reg, regno, off, size, false,
                                          "rdonly",
                                          &env->prog->aux->max_rdonly_access);
                if (!err && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else if (reg->type == PTR_TO_RDWR_BUF) {
                err = check_buffer_access(env, reg, regno, off, size, false,
                                          "rdwr",
                                          &env->prog->aux->max_rdwr_access);
                if (!err && t == BPF_READ && value_regno >= 0)
                        mark_reg_unknown(env, regs, value_regno);
        } else {
                verbose(env, "R%d invalid mem access '%s'\n", regno,
                        reg_type_str[reg->type]);
                return -EACCES;
        }

        if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ &&
            regs[value_regno].type == SCALAR_VALUE) {
                /* b/h/w load zero-extends, mark upper bits as known 0 */
                coerce_reg_to_size(&regs[value_regno], size);
        }
        return err;
}

static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_insn *insn)
{
        int load_reg;
        int err;

        switch (insn->imm) {
        case BPF_ADD:
        case BPF_ADD | BPF_FETCH:
        case BPF_AND:
        case BPF_AND | BPF_FETCH:
        case BPF_OR:
        case BPF_OR | BPF_FETCH:
        case BPF_XOR:
        case BPF_XOR | BPF_FETCH:
        case BPF_XCHG:
        case BPF_CMPXCHG:
                break;
        default:
                verbose(env, "BPF_ATOMIC uses invalid atomic opcode %02x\n", insn->imm);
                return -EINVAL;
        }

        if (BPF_SIZE(insn->code) != BPF_W && BPF_SIZE(insn->code) != BPF_DW) {
                verbose(env, "invalid atomic operand size\n");
                return -EINVAL;
        }

        /* check src1 operand */
        err = check_reg_arg(env, insn->src_reg, SRC_OP);
        if (err)
                return err;

        /* check src2 operand */
        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
        if (err)
                return err;

        if (insn->imm == BPF_CMPXCHG) {
                /* Check comparison of R0 with memory location */
                err = check_reg_arg(env, BPF_REG_0, SRC_OP);
                if (err)
                        return err;
        }

        if (is_pointer_value(env, insn->src_reg)) {
                verbose(env, "R%d leaks addr into mem\n", insn->src_reg);
                return -EACCES;
        }

        if (is_ctx_reg(env, insn->dst_reg) ||
            is_pkt_reg(env, insn->dst_reg) ||
            is_flow_key_reg(env, insn->dst_reg) ||
            is_sk_reg(env, insn->dst_reg)) {
                verbose(env, "BPF_ATOMIC stores into R%d %s is not allowed\n",
                        insn->dst_reg,
                        reg_type_str[reg_state(env, insn->dst_reg)->type]);
                return -EACCES;
        }

        if (insn->imm & BPF_FETCH) {
                if (insn->imm == BPF_CMPXCHG)
                        load_reg = BPF_REG_0;
                else
                        load_reg = insn->src_reg;

                /* check and record load of old value */
                err = check_reg_arg(env, load_reg, DST_OP);
                if (err)
                        return err;
        } else {
                /* This instruction accesses a memory location but doesn't
                 * actually load it into a register.
                 */
                load_reg = -1;
        }

        /* check whether we can read the memory */
        err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                               BPF_SIZE(insn->code), BPF_READ, load_reg, true);
        if (err)
                return err;

        /* check whether we can write into the same memory */
        err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
                               BPF_SIZE(insn->code), BPF_WRITE, -1, true);
        if (err)
                return err;

        return 0;
}

/* When register 'regno' is used to read the stack (either directly or through
 * a helper function) make sure that it's within stack boundary and, depending
 * on the access type, that all elements of the stack are initialized.
 *
 * 'off' includes 'regno->off', but not its dynamic part (if any).
 *
 * All registers that have been spilled on the stack in the slots within the
 * read offsets are marked as read.
 */
static int check_stack_range_initialized(
                struct bpf_verifier_env *env, int regno, int off,
                int access_size, bool zero_size_allowed,
                enum stack_access_src type, struct bpf_call_arg_meta *meta)
{
        struct bpf_reg_state *reg = reg_state(env, regno);
        struct bpf_func_state *state = func(env, reg);
        int err, min_off, max_off, i, j, slot, spi;
        char *err_extra = type == ACCESS_HELPER ? " indirect" : "";
        enum bpf_access_type bounds_check_type;
        /* Some accesses can write anything into the stack, others are
         * read-only.
         */
        bool clobber = false;

        if (access_size == 0 && !zero_size_allowed) {
                verbose(env, "invalid zero-sized read\n");
                return -EACCES;
        }

        if (type == ACCESS_HELPER) {
                /* The bounds checks for writes are more permissive than for
                 * reads. However, if raw_mode is not set, we'll do extra
                 * checks below.
                 */
                bounds_check_type = BPF_WRITE;
                clobber = true;
        } else {
                bounds_check_type = BPF_READ;
        }
        err = check_stack_access_within_bounds(env, regno, off, access_size,
                                               type, bounds_check_type);
        if (err)
                return err;


        if (tnum_is_const(reg->var_off)) {
                min_off = max_off = reg->var_off.value + off;
        } else {
                /* Variable offset is prohibited for unprivileged mode for
                 * simplicity since it requires corresponding support in
                 * Spectre masking for stack ALU.
                 * See also retrieve_ptr_limit().
                 */
                if (!env->bypass_spec_v1) {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env, "R%d%s variable offset stack access prohibited for !root, var_off=%s\n",
                                regno, err_extra, tn_buf);
                        return -EACCES;
                }
                /* Only initialized buffer on stack is allowed to be accessed
                 * with variable offset. With uninitialized buffer it's hard to
                 * guarantee that whole memory is marked as initialized on
                 * helper return since specific bounds are unknown what may
                 * cause uninitialized stack leaking.
                 */
                if (meta && meta->raw_mode)
                        meta = NULL;

                min_off = reg->smin_value + off;
                max_off = reg->smax_value + off;
        }

        if (meta && meta->raw_mode) {
                meta->access_size = access_size;
                meta->regno = regno;
                return 0;
        }

        for (i = min_off; i < max_off + access_size; i++) {
                u8 *stype;

                slot = -i - 1;
                spi = slot / BPF_REG_SIZE;
                if (state->allocated_stack <= slot)
                        goto err;
                stype = &state->stack[spi].slot_type[slot % BPF_REG_SIZE];
                if (*stype == STACK_MISC)
                        goto mark;
                if (*stype == STACK_ZERO) {
                        if (clobber) {
                                /* helper can write anything into the stack */
                                *stype = STACK_MISC;
                        }
                        goto mark;
                }

                if (state->stack[spi].slot_type[0] == STACK_SPILL &&
                    state->stack[spi].spilled_ptr.type == PTR_TO_BTF_ID)
                        goto mark;

                if (state->stack[spi].slot_type[0] == STACK_SPILL &&
                    (state->stack[spi].spilled_ptr.type == SCALAR_VALUE ||
                     env->allow_ptr_leaks)) {
                        if (clobber) {
                                __mark_reg_unknown(env, &state->stack[spi].spilled_ptr);
                                for (j = 0; j < BPF_REG_SIZE; j++)
                                        state->stack[spi].slot_type[j] = STACK_MISC;
                        }
                        goto mark;
                }

err:
                if (tnum_is_const(reg->var_off)) {
                        verbose(env, "invalid%s read from stack R%d off %d+%d size %d\n",
                                err_extra, regno, min_off, i - min_off, access_size);
                } else {
                        char tn_buf[48];

                        tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                        verbose(env, "invalid%s read from stack R%d var_off %s+%d size %d\n",
                                err_extra, regno, tn_buf, i - min_off, access_size);
                }
                return -EACCES;
mark:
                /* reading any byte out of 8-byte 'spill_slot' will cause
                 * the whole slot to be marked as 'read'
                 */
                mark_reg_read(env, &state->stack[spi].spilled_ptr,
                              state->stack[spi].spilled_ptr.parent,
                              REG_LIVE_READ64);
        }
        return update_stack_depth(env, state, min_off);
}

static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
                                   int access_size, bool zero_size_allowed,
                                   struct bpf_call_arg_meta *meta)
{
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];

        switch (reg->type) {
        case PTR_TO_PACKET:
        case PTR_TO_PACKET_META:
                return check_packet_access(env, regno, reg->off, access_size,
                                           zero_size_allowed);
        case PTR_TO_MAP_KEY:
                return check_mem_region_access(env, regno, reg->off, access_size,
                                               reg->map_ptr->key_size, false);
        case PTR_TO_MAP_VALUE:
                if (check_map_access_type(env, regno, reg->off, access_size,
                                          meta && meta->raw_mode ? BPF_WRITE :
                                          BPF_READ))
                        return -EACCES;
                return check_map_access(env, regno, reg->off, access_size,
                                        zero_size_allowed);
        case PTR_TO_MEM:
                return check_mem_region_access(env, regno, reg->off,
                                               access_size, reg->mem_size,
                                               zero_size_allowed);
        case PTR_TO_RDONLY_BUF:
                if (meta && meta->raw_mode)
                        return -EACCES;
                return check_buffer_access(env, reg, regno, reg->off,
                                           access_size, zero_size_allowed,
                                           "rdonly",
                                           &env->prog->aux->max_rdonly_access);
        case PTR_TO_RDWR_BUF:
                return check_buffer_access(env, reg, regno, reg->off,
                                           access_size, zero_size_allowed,
                                           "rdwr",
                                           &env->prog->aux->max_rdwr_access);
        case PTR_TO_STACK:
                return check_stack_range_initialized(
                                env,
                                regno, reg->off, access_size,
                                zero_size_allowed, ACCESS_HELPER, meta);
        default: /* scalar_value or invalid ptr */
                /* Allow zero-byte read from NULL, regardless of pointer type */
                if (zero_size_allowed && access_size == 0 &&
                    register_is_null(reg))
                        return 0;

                verbose(env, "R%d type=%s expected=%s\n", regno,
                        reg_type_str[reg->type],
                        reg_type_str[PTR_TO_STACK]);
                return -EACCES;
        }
}

int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
                   u32 regno, u32 mem_size)
{
        if (register_is_null(reg))
                return 0;

        if (reg_type_may_be_null(reg->type)) {
                /* Assuming that the register contains a value check if the memory
                 * access is safe. Temporarily save and restore the register's state as
                 * the conversion shouldn't be visible to a caller.
                 */
                const struct bpf_reg_state saved_reg = *reg;
                int rv;

                mark_ptr_not_null_reg(reg);
                rv = check_helper_mem_access(env, regno, mem_size, true, NULL);
                *reg = saved_reg;
                return rv;
        }

        return check_helper_mem_access(env, regno, mem_size, true, NULL);
}

/* Implementation details:
 * bpf_map_lookup returns PTR_TO_MAP_VALUE_OR_NULL
 * Two bpf_map_lookups (even with the same key) will have different reg->id.
 * For traditional PTR_TO_MAP_VALUE the verifier clears reg->id after
 * value_or_null->value transition, since the verifier only cares about
 * the range of access to valid map value pointer and doesn't care about actual
 * address of the map element.
 * For maps with 'struct bpf_spin_lock' inside map value the verifier keeps
 * reg->id > 0 after value_or_null->value transition. By doing so
 * two bpf_map_lookups will be considered two different pointers that
 * point to different bpf_spin_locks.
 * The verifier allows taking only one bpf_spin_lock at a time to avoid
 * dead-locks.
 * Since only one bpf_spin_lock is allowed the checks are simpler than
 * reg_is_refcounted() logic. The verifier needs to remember only
 * one spin_lock instead of array of acquired_refs.
 * cur_state->active_spin_lock remembers which map value element got locked
 * and clears it after bpf_spin_unlock.
 */
static int process_spin_lock(struct bpf_verifier_env *env, int regno,
                             bool is_lock)
{
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
        struct bpf_verifier_state *cur = env->cur_state;
        bool is_const = tnum_is_const(reg->var_off);
        struct bpf_map *map = reg->map_ptr;
        u64 val = reg->var_off.value;

        if (!is_const) {
                verbose(env,
                        "R%d doesn't have constant offset. bpf_spin_lock has to be at the constant offset\n",
                        regno);
                return -EINVAL;
        }
        if (!map->btf) {
                verbose(env,
                        "map '%s' has to have BTF in order to use bpf_spin_lock\n",
                        map->name);
                return -EINVAL;
        }
        if (!map_value_has_spin_lock(map)) {
                if (map->spin_lock_off == -E2BIG)
                        verbose(env,
                                "map '%s' has more than one 'struct bpf_spin_lock'\n",
                                map->name);
                else if (map->spin_lock_off == -ENOENT)
                        verbose(env,
                                "map '%s' doesn't have 'struct bpf_spin_lock'\n",
                                map->name);
                else
                        verbose(env,
                                "map '%s' is not a struct type or bpf_spin_lock is mangled\n",
                                map->name);
                return -EINVAL;
        }
        if (map->spin_lock_off != val + reg->off) {
                verbose(env, "off %lld doesn't point to 'struct bpf_spin_lock'\n",
                        val + reg->off);
                return -EINVAL;
        }
        if (is_lock) {
                if (cur->active_spin_lock) {
                        verbose(env,
                                "Locking two bpf_spin_locks are not allowed\n");
                        return -EINVAL;
                }
                cur->active_spin_lock = reg->id;
        } else {
                if (!cur->active_spin_lock) {
                        verbose(env, "bpf_spin_unlock without taking a lock\n");
                        return -EINVAL;
                }
                if (cur->active_spin_lock != reg->id) {
                        verbose(env, "bpf_spin_unlock of different lock\n");
                        return -EINVAL;
                }
                cur->active_spin_lock = 0;
        }
        return 0;
}

static bool arg_type_is_mem_ptr(enum bpf_arg_type type)
{
        return type == ARG_PTR_TO_MEM ||
               type == ARG_PTR_TO_MEM_OR_NULL ||
               type == ARG_PTR_TO_UNINIT_MEM;
}

static bool arg_type_is_mem_size(enum bpf_arg_type type)
{
        return type == ARG_CONST_SIZE ||
               type == ARG_CONST_SIZE_OR_ZERO;
}

static bool arg_type_is_alloc_size(enum bpf_arg_type type)
{
        return type == ARG_CONST_ALLOC_SIZE_OR_ZERO;
}

static bool arg_type_is_int_ptr(enum bpf_arg_type type)
{
        return type == ARG_PTR_TO_INT ||
               type == ARG_PTR_TO_LONG;
}

static int int_ptr_type_to_size(enum bpf_arg_type type)
{
        if (type == ARG_PTR_TO_INT)
                return sizeof(u32);
        else if (type == ARG_PTR_TO_LONG)
                return sizeof(u64);

        return -EINVAL;
}

static int resolve_map_arg_type(struct bpf_verifier_env *env,
                                 const struct bpf_call_arg_meta *meta,
                                 enum bpf_arg_type *arg_type)
{
        if (!meta->map_ptr) {
                /* kernel subsystem misconfigured verifier */
                verbose(env, "invalid map_ptr to access map->type\n");
                return -EACCES;
        }

        switch (meta->map_ptr->map_type) {
        case BPF_MAP_TYPE_SOCKMAP:
        case BPF_MAP_TYPE_SOCKHASH:
                if (*arg_type == ARG_PTR_TO_MAP_VALUE) {
                        *arg_type = ARG_PTR_TO_BTF_ID_SOCK_COMMON;
                } else {
                        verbose(env, "invalid arg_type for sockmap/sockhash\n");
                        return -EINVAL;
                }
                break;

        default:
                break;
        }
        return 0;
}

struct bpf_reg_types {
        const enum bpf_reg_type types[10];
        u32 *btf_id;
};

static const struct bpf_reg_types map_key_value_types = {
        .types = {
                PTR_TO_STACK,
                PTR_TO_PACKET,
                PTR_TO_PACKET_META,
                PTR_TO_MAP_KEY,
                PTR_TO_MAP_VALUE,
        },
};

static const struct bpf_reg_types sock_types = {
        .types = {
                PTR_TO_SOCK_COMMON,
                PTR_TO_SOCKET,
                PTR_TO_TCP_SOCK,
                PTR_TO_XDP_SOCK,
        },
};

#ifdef CONFIG_NET
static const struct bpf_reg_types btf_id_sock_common_types = {
        .types = {
                PTR_TO_SOCK_COMMON,
                PTR_TO_SOCKET,
                PTR_TO_TCP_SOCK,
                PTR_TO_XDP_SOCK,
                PTR_TO_BTF_ID,
        },
        .btf_id = &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON],
};
#endif

static const struct bpf_reg_types mem_types = {
        .types = {
                PTR_TO_STACK,
                PTR_TO_PACKET,
                PTR_TO_PACKET_META,
                PTR_TO_MAP_KEY,
                PTR_TO_MAP_VALUE,
                PTR_TO_MEM,
                PTR_TO_RDONLY_BUF,
                PTR_TO_RDWR_BUF,
        },
};

static const struct bpf_reg_types int_ptr_types = {
        .types = {
                PTR_TO_STACK,
                PTR_TO_PACKET,
                PTR_TO_PACKET_META,
                PTR_TO_MAP_KEY,
                PTR_TO_MAP_VALUE,
        },
};

static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
static const struct bpf_reg_types percpu_btf_ptr_types = { .types = { PTR_TO_PERCPU_BTF_ID } };
static const struct bpf_reg_types func_ptr_types = { .types = { PTR_TO_FUNC } };
static const struct bpf_reg_types stack_ptr_types = { .types = { PTR_TO_STACK } };

static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
        [ARG_PTR_TO_MAP_KEY]            = &map_key_value_types,
        [ARG_PTR_TO_MAP_VALUE]          = &map_key_value_types,
        [ARG_PTR_TO_UNINIT_MAP_VALUE]   = &map_key_value_types,
        [ARG_PTR_TO_MAP_VALUE_OR_NULL]  = &map_key_value_types,
        [ARG_CONST_SIZE]                = &scalar_types,
        [ARG_CONST_SIZE_OR_ZERO]        = &scalar_types,
        [ARG_CONST_ALLOC_SIZE_OR_ZERO]  = &scalar_types,
        [ARG_CONST_MAP_PTR]             = &const_map_ptr_types,
        [ARG_PTR_TO_CTX]                = &context_types,
        [ARG_PTR_TO_CTX_OR_NULL]        = &context_types,
        [ARG_PTR_TO_SOCK_COMMON]        = &sock_types,
#ifdef CONFIG_NET
        [ARG_PTR_TO_BTF_ID_SOCK_COMMON] = &btf_id_sock_common_types,
#endif
        [ARG_PTR_TO_SOCKET]             = &fullsock_types,
        [ARG_PTR_TO_SOCKET_OR_NULL]     = &fullsock_types,
        [ARG_PTR_TO_BTF_ID]             = &btf_ptr_types,
        [ARG_PTR_TO_SPIN_LOCK]          = &spin_lock_types,
        [ARG_PTR_TO_MEM]                = &mem_types,
        [ARG_PTR_TO_MEM_OR_NULL]        = &mem_types,
        [ARG_PTR_TO_UNINIT_MEM]         = &mem_types,
        [ARG_PTR_TO_ALLOC_MEM]          = &alloc_mem_types,
        [ARG_PTR_TO_ALLOC_MEM_OR_NULL]  = &alloc_mem_types,
        [ARG_PTR_TO_INT]                = &int_ptr_types,
        [ARG_PTR_TO_LONG]               = &int_ptr_types,
        [ARG_PTR_TO_PERCPU_BTF_ID]      = &percpu_btf_ptr_types,
        [ARG_PTR_TO_FUNC]               = &func_ptr_types,
        [ARG_PTR_TO_STACK_OR_NULL]      = &stack_ptr_types,
};

static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
                          enum bpf_arg_type arg_type,
                          const u32 *arg_btf_id)
{
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
        enum bpf_reg_type expected, type = reg->type;
        const struct bpf_reg_types *compatible;
        int i, j;

        compatible = compatible_reg_types[arg_type];
        if (!compatible) {
                verbose(env, "verifier internal error: unsupported arg type %d\n", arg_type);
                return -EFAULT;
        }

        for (i = 0; i < ARRAY_SIZE(compatible->types); i++) {
                expected = compatible->types[i];
                if (expected == NOT_INIT)
                        break;

                if (type == expected)
                        goto found;
        }

        verbose(env, "R%d type=%s expected=", regno, reg_type_str[type]);
        for (j = 0; j + 1 < i; j++)
                verbose(env, "%s, ", reg_type_str[compatible->types[j]]);
        verbose(env, "%s\n", reg_type_str[compatible->types[j]]);
        return -EACCES;

found:
        if (type == PTR_TO_BTF_ID) {
                if (!arg_btf_id) {
                        if (!compatible->btf_id) {
                                verbose(env, "verifier internal error: missing arg compatible BTF ID\n");
                                return -EFAULT;
                        }
                        arg_btf_id = compatible->btf_id;
                }

                if (!btf_struct_ids_match(&env->log, reg->btf, reg->btf_id, reg->off,
                                          btf_vmlinux, *arg_btf_id)) {
                        verbose(env, "R%d is of type %s but %s is expected\n",
                                regno, kernel_type_name(reg->btf, reg->btf_id),
                                kernel_type_name(btf_vmlinux, *arg_btf_id));
                        return -EACCES;
                }

                if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
                        verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
                                regno);
                        return -EACCES;
                }
        }

        return 0;
}

static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
                          struct bpf_call_arg_meta *meta,
                          const struct bpf_func_proto *fn)
{
        u32 regno = BPF_REG_1 + arg;
        struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
        enum bpf_arg_type arg_type = fn->arg_type[arg];
        enum bpf_reg_type type = reg->type;
        int err = 0;

        if (arg_type == ARG_DONTCARE)
                return 0;

        err = check_reg_arg(env, regno, SRC_OP);
        if (err)
                return err;

        if (arg_type == ARG_ANYTHING) {
                if (is_pointer_value(env, regno)) {
                        verbose(env, "R%d leaks addr into helper function\n",
                                regno);
                        return -EACCES;
                }
                return 0;
        }

        if (type_is_pkt_pointer(type) &&
            !may_access_direct_pkt_data(env, meta, BPF_READ)) {
                verbose(env, "helper access to the packet is not allowed\n");
                return -EACCES;
        }

        if (arg_type == ARG_PTR_TO_MAP_VALUE ||
            arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE ||
            arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL) {
                err = resolve_map_arg_type(env, meta, &arg_type);
                if (err)
                        return err;
        }

        if (register_is_null(reg) && arg_type_may_be_null(arg_type))
                /* A NULL register has a SCALAR_VALUE type, so skip
                 * type checking.
                 */
                goto skip_type_check;

        err = check_reg_type(env, regno, arg_type, fn->arg_btf_id[arg]);
        if (err)
                return err;

        if (type == PTR_TO_CTX) {
                err = check_ctx_reg(env, reg, regno);
                if (err < 0)
                        return err;
        }

skip_type_check:
        if (reg->ref_obj_id) {
                if (meta->ref_obj_id) {
                        verbose(env, "verifier internal error: more than one arg with ref_obj_id R%d %u %u\n",
                                regno, reg->ref_obj_id,
                                meta->ref_obj_id);
                        return -EFAULT;
                }
                meta->ref_obj_id = reg->ref_obj_id;
        }

        if (arg_type == ARG_CONST_MAP_PTR) {
                /* bpf_map_xxx(map_ptr) call: remember that map_ptr */
                meta->map_ptr = reg->map_ptr;
        } else if (arg_type == ARG_PTR_TO_MAP_KEY) {
                /* bpf_map_xxx(..., map_ptr, ..., key) call:
                 * check that [key, key + map->key_size) are within
                 * stack limits and initialized
                 */
                if (!meta->map_ptr) {
                        /* in function declaration map_ptr must come before
                         * map_key, so that it's verified and known before
                         * we have to check map_key here. Otherwise it means
                         * that kernel subsystem misconfigured verifier
                         */
                        verbose(env, "invalid map_ptr to access map->key\n");
                        return -EACCES;
                }
                err = check_helper_mem_access(env, regno,
                                              meta->map_ptr->key_size, false,
                                              NULL);
        } else if (arg_type == ARG_PTR_TO_MAP_VALUE ||
                   (arg_type == ARG_PTR_TO_MAP_VALUE_OR_NULL &&
                    !register_is_null(reg)) ||
                   arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE) {
                /* bpf_map_xxx(..., map_ptr, ..., value) call:
                 * check [value, value + map->value_size) validity
                 */
                if (!meta->map_ptr) {
                        /* kernel subsystem misconfigured verifier */
                        verbose(env, "invalid map_ptr to access map->value\n");
                        return -EACCES;
                }
                meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MAP_VALUE);
                err = check_helper_mem_access(env, regno,
                                              meta->map_ptr->value_size, false,
                                              meta);
        } else if (arg_type == ARG_PTR_TO_PERCPU_BTF_ID) {
                if (!reg->btf_id) {
                        verbose(env, "Helper has invalid btf_id in R%d\n", regno);
                        return -EACCES;
                }
                meta->ret_btf = reg->btf;
                meta->ret_btf_id = reg->btf_id;
        } else if (arg_type == ARG_PTR_TO_SPIN_LOCK) {
                if (meta->func_id == BPF_FUNC_spin_lock) {
                        if (process_spin_lock(env, regno, true))
                                return -EACCES;
                } else if (meta->func_id == BPF_FUNC_spin_unlock) {
                        if (process_spin_lock(env, regno, false))
                                return -EACCES;
                } else {
                        verbose(env, "verifier internal error\n");
                        return -EFAULT;
                }
        } else if (arg_type == ARG_PTR_TO_FUNC) {
                meta->subprogno = reg->subprogno;
        } else if (arg_type_is_mem_ptr(arg_type)) {
                /* The access to this pointer is only checked when we hit the
                 * next is_mem_size argument below.
                 */
                meta->raw_mode = (arg_type == ARG_PTR_TO_UNINIT_MEM);
        } else if (arg_type_is_mem_size(arg_type)) {
                bool zero_size_allowed = (arg_type == ARG_CONST_SIZE_OR_ZERO);

                /* This is used to refine r0 return value bounds for helpers
                 * that enforce this value as an upper bound on return values.
                 * See do_refine_retval_range() for helpers that can refine
                 * the return value. C type of helper is u32 so we pull register
                 * bound from umax_value however, if negative verifier errors
                 * out. Only upper bounds can be learned because retval is an
                 * int type and negative retvals are allowed.
                 */
                meta->msize_max_value = reg->umax_value;

                /* The register is SCALAR_VALUE; the access check
                 * happens using its boundaries.
                 */
                if (!tnum_is_const(reg->var_off))
                        /* For unprivileged variable accesses, disable raw
                         * mode so that the program is required to
                         * initialize all the memory that the helper could
                         * just partially fill up.
                         */
                        meta = NULL;

                if (reg->smin_value < 0) {
                        verbose(env, "R%d min value is negative, either use unsigned or 'var &= const'\n",
                                regno);
                        return -EACCES;
                }

                if (reg->umin_value == 0) {
                        err = check_helper_mem_access(env, regno - 1, 0,
                                                      zero_size_allowed,
                                                      meta);
                        if (err)
                                return err;
                }

                if (reg->umax_value >= BPF_MAX_VAR_SIZ) {
                        verbose(env, "R%d unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
                                regno);
                        return -EACCES;
                }
                err = check_helper_mem_access(env, regno - 1,
                                              reg->umax_value,
                                              zero_size_allowed, meta);
                if (!err)
                        err = mark_chain_precision(env, regno);
        } else if (arg_type_is_alloc_size(arg_type)) {
                if (!tnum_is_const(reg->var_off)) {
                        verbose(env, "R%d is not a known constant'\n",
                                regno);
                        return -EACCES;
                }
                meta->mem_size = reg->var_off.value;
        } else if (arg_type_is_int_ptr(arg_type)) {
                int size = int_ptr_type_to_size(arg_type);

                err = check_helper_mem_access(env, regno, size, false, meta);
                if (err)
                        return err;
                err = check_ptr_alignment(env, reg, 0, size, true);
        }

        return err;
}

static bool may_update_sockmap(struct bpf_verifier_env *env, int func_id)
{
        enum bpf_attach_type eatype = env->prog->expected_attach_type;
        enum bpf_prog_type type = resolve_prog_type(env->prog);

        if (func_id != BPF_FUNC_map_update_elem)
                return false;

        /* It's not possible to get access to a locked struct sock in these
         * contexts, so updating is safe.
         */
        switch (type) {
        case BPF_PROG_TYPE_TRACING:
                if (eatype == BPF_TRACE_ITER)
                        return true;
                break;
        case BPF_PROG_TYPE_SOCKET_FILTER:
        case BPF_PROG_TYPE_SCHED_CLS:
        case BPF_PROG_TYPE_SCHED_ACT:
        case BPF_PROG_TYPE_XDP:
        case BPF_PROG_TYPE_SK_REUSEPORT:
        case BPF_PROG_TYPE_FLOW_DISSECTOR:
        case BPF_PROG_TYPE_SK_LOOKUP:
                return true;
        default:
                break;
        }

        verbose(env, "cannot update sockmap in this context\n");
        return false;
}

static bool allow_tail_call_in_subprogs(struct bpf_verifier_env *env)
{
        return env->prog->jit_requested && IS_ENABLED(CONFIG_X86_64);
}

static int check_map_func_compatibility(struct bpf_verifier_env *env,
                                        struct bpf_map *map, int func_id)
{
        if (!map)
                return 0;

        /* We need a two way check, first is from map perspective ... */
        switch (map->map_type) {
        case BPF_MAP_TYPE_PROG_ARRAY:
                if (func_id != BPF_FUNC_tail_call)
                        goto error;
                break;
        case BPF_MAP_TYPE_PERF_EVENT_ARRAY:
                if (func_id != BPF_FUNC_perf_event_read &&
                    func_id != BPF_FUNC_perf_event_output &&
                    func_id != BPF_FUNC_skb_output &&
                    func_id != BPF_FUNC_perf_event_read_value &&
                    func_id != BPF_FUNC_xdp_output)
                        goto error;
                break;
        case BPF_MAP_TYPE_RINGBUF:
                if (func_id != BPF_FUNC_ringbuf_output &&
                    func_id != BPF_FUNC_ringbuf_reserve &&
                    func_id != BPF_FUNC_ringbuf_submit &&
                    func_id != BPF_FUNC_ringbuf_discard &&
                    func_id != BPF_FUNC_ringbuf_query)
                        goto error;
                break;
        case BPF_MAP_TYPE_STACK_TRACE:
                if (func_id != BPF_FUNC_get_stackid)
                        goto error;
                break;
        case BPF_MAP_TYPE_CGROUP_ARRAY:
                if (func_id != BPF_FUNC_skb_under_cgroup &&
                    func_id != BPF_FUNC_current_task_under_cgroup)
                        goto error;
                break;
        case BPF_MAP_TYPE_CGROUP_STORAGE:
        case BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE:
                if (func_id != BPF_FUNC_get_local_storage)
                        goto error;
                break;
        case BPF_MAP_TYPE_DEVMAP:
        case BPF_MAP_TYPE_DEVMAP_HASH:
                if (func_id != BPF_FUNC_redirect_map &&
                    func_id != BPF_FUNC_map_lookup_elem)
                        goto error;
                break;
        /* Restrict bpf side of cpumap and xskmap, open when use-cases
         * appear.
         */
        case BPF_MAP_TYPE_CPUMAP:
                if (func_id != BPF_FUNC_redirect_map)
                        goto error;
                break;
        case BPF_MAP_TYPE_XSKMAP:
                if (func_id != BPF_FUNC_redirect_map &&
                    func_id != BPF_FUNC_map_lookup_elem)
                        goto error;
                break;
        case BPF_MAP_TYPE_ARRAY_OF_MAPS:
        case BPF_MAP_TYPE_HASH_OF_MAPS:
                if (func_id != BPF_FUNC_map_lookup_elem)
                        goto error;
                break;
        case BPF_MAP_TYPE_SOCKMAP:
                if (func_id != BPF_FUNC_sk_redirect_map &&
                    func_id != BPF_FUNC_sock_map_update &&
                    func_id != BPF_FUNC_map_delete_elem &&
                    func_id != BPF_FUNC_msg_redirect_map &&
                    func_id != BPF_FUNC_sk_select_reuseport &&
                    func_id != BPF_FUNC_map_lookup_elem &&
                    !may_update_sockmap(env, func_id))
                        goto error;
                break;
        case BPF_MAP_TYPE_SOCKHASH:
                if (func_id != BPF_FUNC_sk_redirect_hash &&
                    func_id != BPF_FUNC_sock_hash_update &&
                    func_id != BPF_FUNC_map_delete_elem &&
                    func_id != BPF_FUNC_msg_redirect_hash &&
                    func_id != BPF_FUNC_sk_select_reuseport &&
                    func_id != BPF_FUNC_map_lookup_elem &&
                    !may_update_sockmap(env, func_id))
                        goto error;
                break;
        case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
                if (func_id != BPF_FUNC_sk_select_reuseport)
                        goto error;
                break;
        case BPF_MAP_TYPE_QUEUE:
        case BPF_MAP_TYPE_STACK:
                if (func_id != BPF_FUNC_map_peek_elem &&
                    func_id != BPF_FUNC_map_pop_elem &&
                    func_id != BPF_FUNC_map_push_elem)
                        goto error;
                break;
        case BPF_MAP_TYPE_SK_STORAGE:
                if (func_id != BPF_FUNC_sk_storage_get &&
                    func_id != BPF_FUNC_sk_storage_delete)
                        goto error;
                break;
        case BPF_MAP_TYPE_INODE_STORAGE:
                if (func_id != BPF_FUNC_inode_storage_get &&
                    func_id != BPF_FUNC_inode_storage_delete)
                        goto error;
                break;
        case BPF_MAP_TYPE_TASK_STORAGE:
                if (func_id != BPF_FUNC_task_storage_get &&
                    func_id != BPF_FUNC_task_storage_delete)
                        goto error;
                break;
        default:
                break;
        }

        /* ... and second from the function itself. */
        switch (func_id) {
        case BPF_FUNC_tail_call:
                if (map->map_type != BPF_MAP_TYPE_PROG_ARRAY)
                        goto error;
                if (env->subprog_cnt > 1 && !allow_tail_call_in_subprogs(env)) {
                        verbose(env, "tail_calls are not allowed in non-JITed programs with bpf-to-bpf calls\n");
                        return -EINVAL;
                }
                break;
        case BPF_FUNC_perf_event_read:
        case BPF_FUNC_perf_event_output:
        case BPF_FUNC_perf_event_read_value:
        case BPF_FUNC_skb_output:
        case BPF_FUNC_xdp_output:
                if (map->map_type != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
                        goto error;
                break;
        case BPF_FUNC_get_stackid:
                if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
                        goto error;
                break;
        case BPF_FUNC_current_task_under_cgroup:
        case BPF_FUNC_skb_under_cgroup:
                if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
                        goto error;
                break;
        case BPF_FUNC_redirect_map:
                if (map->map_type != BPF_MAP_TYPE_DEVMAP &&
                    map->map_type != BPF_MAP_TYPE_DEVMAP_HASH &&
                    map->map_type != BPF_MAP_TYPE_CPUMAP &&
                    map->map_type != BPF_MAP_TYPE_XSKMAP)
                        goto error;
                break;
        case BPF_FUNC_sk_redirect_map:
        case BPF_FUNC_msg_redirect_map:
        case BPF_FUNC_sock_map_update:
                if (map->map_type != BPF_MAP_TYPE_SOCKMAP)
                        goto error;
                break;
        case BPF_FUNC_sk_redirect_hash:
        case BPF_FUNC_msg_redirect_hash:
        case BPF_FUNC_sock_hash_update:
                if (map->map_type != BPF_MAP_TYPE_SOCKHASH)
                        goto error;
                break;
        case BPF_FUNC_get_local_storage:
                if (map->map_type != BPF_MAP_TYPE_CGROUP_STORAGE &&
                    map->map_type != BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE)
                        goto error;
                break;
        case BPF_FUNC_sk_select_reuseport:
                if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY &&
                    map->map_type != BPF_MAP_TYPE_SOCKMAP &&
                    map->map_type != BPF_MAP_TYPE_SOCKHASH)
                        goto error;
                break;
        case BPF_FUNC_map_peek_elem:
        case BPF_FUNC_map_pop_elem:
        case BPF_FUNC_map_push_elem:
                if (map->map_type != BPF_MAP_TYPE_QUEUE &&
                    map->map_type != BPF_MAP_TYPE_STACK)
                        goto error;
                break;
        case BPF_FUNC_sk_storage_get:
        case BPF_FUNC_sk_storage_delete:
                if (map->map_type != BPF_MAP_TYPE_SK_STORAGE)
                        goto error;
                break;
        case BPF_FUNC_inode_storage_get:
        case BPF_FUNC_inode_storage_delete:
                if (map->map_type != BPF_MAP_TYPE_INODE_STORAGE)
                        goto error;
                break;
        case BPF_FUNC_task_storage_get:
        case BPF_FUNC_task_storage_delete:
                if (map->map_type != BPF_MAP_TYPE_TASK_STORAGE)
                        goto error;
                break;
        default:
                break;
        }

        return 0;
error:
        verbose(env, "cannot pass map_type %d into func %s#%d\n",
                map->map_type, func_id_name(func_id), func_id);
        return -EINVAL;
}

static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
{
        int count = 0;

        if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
                count++;
        if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
                count++;

        /* We only support one arg being in raw mode at the moment,
         * which is sufficient for the helper functions we have
         * right now.
         */
        return count <= 1;
}

static bool check_args_pair_invalid(enum bpf_arg_type arg_curr,
                                    enum bpf_arg_type arg_next)
{
        return (arg_type_is_mem_ptr(arg_curr) &&
                !arg_type_is_mem_size(arg_next)) ||
               (!arg_type_is_mem_ptr(arg_curr) &&
                arg_type_is_mem_size(arg_next));
}

static bool check_arg_pair_ok(const struct bpf_func_proto *fn)
{
        /* bpf_xxx(..., buf, len) call will access 'len'
         * bytes from memory 'buf'. Both arg types need
         * to be paired, so make sure there's no buggy
         * helper function specification.
         */
        if (arg_type_is_mem_size(fn->arg1_type) ||
            arg_type_is_mem_ptr(fn->arg5_type)  ||
            check_args_pair_invalid(fn->arg1_type, fn->arg2_type) ||
            check_args_pair_invalid(fn->arg2_type, fn->arg3_type) ||
            check_args_pair_invalid(fn->arg3_type, fn->arg4_type) ||
            check_args_pair_invalid(fn->arg4_type, fn->arg5_type))
                return false;

        return true;
}

static bool check_refcount_ok(const struct bpf_func_proto *fn, int func_id)
{
        int count = 0;

        if (arg_type_may_be_refcounted(fn->arg1_type))
                count++;
        if (arg_type_may_be_refcounted(fn->arg2_type))
                count++;
        if (arg_type_may_be_refcounted(fn->arg3_type))
                count++;
        if (arg_type_may_be_refcounted(fn->arg4_type))
                count++;
        if (arg_type_may_be_refcounted(fn->arg5_type))
                count++;

        /* A reference acquiring function cannot acquire
         * another refcounted ptr.
         */
        if (may_be_acquire_function(func_id) && count)
                return false;

        /* We only support one arg being unreferenced at the moment,
         * which is sufficient for the helper functions we have right now.
         */
        return count <= 1;
}

static bool check_btf_id_ok(const struct bpf_func_proto *fn)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(fn->arg_type); i++) {
                if (fn->arg_type[i] == ARG_PTR_TO_BTF_ID && !fn->arg_btf_id[i])
                        return false;

                if (fn->arg_type[i] != ARG_PTR_TO_BTF_ID && fn->arg_btf_id[i])
                        return false;
        }

        return true;
}

static int check_func_proto(const struct bpf_func_proto *fn, int func_id)
{
        return check_raw_mode_ok(fn) &&
               check_arg_pair_ok(fn) &&
               check_btf_id_ok(fn) &&
               check_refcount_ok(fn, func_id) ? 0 : -EINVAL;
}

/* Packet data might have moved, any old PTR_TO_PACKET[_META,_END]
 * are now invalid, so turn them into unknown SCALAR_VALUE.
 */
static void __clear_all_pkt_pointers(struct bpf_verifier_env *env,
                                     struct bpf_func_state *state)
{
        struct bpf_reg_state *regs = state->regs, *reg;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++)
                if (reg_is_pkt_pointer_any(&regs[i]))
                        mark_reg_unknown(env, regs, i);

        bpf_for_each_spilled_reg(i, state, reg) {
                if (!reg)
                        continue;
                if (reg_is_pkt_pointer_any(reg))
                        __mark_reg_unknown(env, reg);
        }
}

static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        int i;

        for (i = 0; i <= vstate->curframe; i++)
                __clear_all_pkt_pointers(env, vstate->frame[i]);
}

enum {
        AT_PKT_END = -1,
        BEYOND_PKT_END = -2,
};

static void mark_pkt_end(struct bpf_verifier_state *vstate, int regn, bool range_open)
{
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *reg = &state->regs[regn];

        if (reg->type != PTR_TO_PACKET)
                /* PTR_TO_PACKET_META is not supported yet */
                return;

        /* The 'reg' is pkt > pkt_end or pkt >= pkt_end.
         * How far beyond pkt_end it goes is unknown.
         * if (!range_open) it's the case of pkt >= pkt_end
         * if (range_open) it's the case of pkt > pkt_end
         * hence this pointer is at least 1 byte bigger than pkt_end
         */
        if (range_open)
                reg->range = BEYOND_PKT_END;
        else
                reg->range = AT_PKT_END;
}

static void release_reg_references(struct bpf_verifier_env *env,
                                   struct bpf_func_state *state,
                                   int ref_obj_id)
{
        struct bpf_reg_state *regs = state->regs, *reg;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++)
                if (regs[i].ref_obj_id == ref_obj_id)
                        mark_reg_unknown(env, regs, i);

        bpf_for_each_spilled_reg(i, state, reg) {
                if (!reg)
                        continue;
                if (reg->ref_obj_id == ref_obj_id)
                        __mark_reg_unknown(env, reg);
        }
}

/* The pointer with the specified id has released its reference to kernel
 * resources. Identify all copies of the same pointer and clear the reference.
 */
static int release_reference(struct bpf_verifier_env *env,
                             int ref_obj_id)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        int err;
        int i;

        err = release_reference_state(cur_func(env), ref_obj_id);
        if (err)
                return err;

        for (i = 0; i <= vstate->curframe; i++)
                release_reg_references(env, vstate->frame[i], ref_obj_id);

        return 0;
}

static void clear_caller_saved_regs(struct bpf_verifier_env *env,
                                    struct bpf_reg_state *regs)
{
        int i;

        /* after the call registers r0 - r5 were scratched */
        for (i = 0; i < CALLER_SAVED_REGS; i++) {
                mark_reg_not_init(env, regs, caller_saved[i]);
                check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
        }
}

typedef int (*set_callee_state_fn)(struct bpf_verifier_env *env,
                                   struct bpf_func_state *caller,
                                   struct bpf_func_state *callee,
                                   int insn_idx);

static int __check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
                             int *insn_idx, int subprog,
                             set_callee_state_fn set_callee_state_cb)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_func_info_aux *func_info_aux;
        struct bpf_func_state *caller, *callee;
        int err;
        bool is_global = false;

        if (state->curframe + 1 >= MAX_CALL_FRAMES) {
                verbose(env, "the call stack of %d frames is too deep\n",
                        state->curframe + 2);
                return -E2BIG;
        }

        caller = state->frame[state->curframe];
        if (state->frame[state->curframe + 1]) {
                verbose(env, "verifier bug. Frame %d already allocated\n",
                        state->curframe + 1);
                return -EFAULT;
        }

        func_info_aux = env->prog->aux->func_info_aux;
        if (func_info_aux)
                is_global = func_info_aux[subprog].linkage == BTF_FUNC_GLOBAL;
        err = btf_check_func_arg_match(env, subprog, caller->regs);
        if (err == -EFAULT)
                return err;
        if (is_global) {
                if (err) {
                        verbose(env, "Caller passes invalid args into func#%d\n",
                                subprog);
                        return err;
                } else {
                        if (env->log.level & BPF_LOG_LEVEL)
                                verbose(env,
                                        "Func#%d is global and valid. Skipping.\n",
                                        subprog);
                        clear_caller_saved_regs(env, caller->regs);

                        /* All global functions return a 64-bit SCALAR_VALUE */
                        mark_reg_unknown(env, caller->regs, BPF_REG_0);
                        caller->regs[BPF_REG_0].subreg_def = DEF_NOT_SUBREG;

                        /* continue with next insn after call */
                        return 0;
                }
        }

        callee = kzalloc(sizeof(*callee), GFP_KERNEL);
        if (!callee)
                return -ENOMEM;
        state->frame[state->curframe + 1] = callee;

        /* callee cannot access r0, r6 - r9 for reading and has to write
         * into its own stack before reading from it.
         * callee can read/write into caller's stack
         */
        init_func_state(env, callee,
                        /* remember the callsite, it will be used by bpf_exit */
                        *insn_idx /* callsite */,
                        state->curframe + 1 /* frameno within this callchain */,
                        subprog /* subprog number within this prog */);

        /* Transfer references to the callee */
        err = transfer_reference_state(callee, caller);
        if (err)
                return err;

        err = set_callee_state_cb(env, caller, callee, *insn_idx);
        if (err)
                return err;

        clear_caller_saved_regs(env, caller->regs);

        /* only increment it after check_reg_arg() finished */
        state->curframe++;

        /* and go analyze first insn of the callee */
        *insn_idx = env->subprog_info[subprog].start - 1;

        if (env->log.level & BPF_LOG_LEVEL) {
                verbose(env, "caller:\n");
                print_verifier_state(env, caller);
                verbose(env, "callee:\n");
                print_verifier_state(env, callee);
        }
        return 0;
}

int map_set_for_each_callback_args(struct bpf_verifier_env *env,
                                   struct bpf_func_state *caller,
                                   struct bpf_func_state *callee)
{
        /* bpf_for_each_map_elem(struct bpf_map *map, void *callback_fn,
         *      void *callback_ctx, u64 flags);
         * callback_fn(struct bpf_map *map, void *key, void *value,
         *      void *callback_ctx);
         */
        callee->regs[BPF_REG_1] = caller->regs[BPF_REG_1];

        callee->regs[BPF_REG_2].type = PTR_TO_MAP_KEY;
        __mark_reg_known_zero(&callee->regs[BPF_REG_2]);
        callee->regs[BPF_REG_2].map_ptr = caller->regs[BPF_REG_1].map_ptr;

        callee->regs[BPF_REG_3].type = PTR_TO_MAP_VALUE;
        __mark_reg_known_zero(&callee->regs[BPF_REG_3]);
        callee->regs[BPF_REG_3].map_ptr = caller->regs[BPF_REG_1].map_ptr;

        /* pointer to stack or null */
        callee->regs[BPF_REG_4] = caller->regs[BPF_REG_3];

        /* unused */
        __mark_reg_not_init(env, &callee->regs[BPF_REG_5]);
        return 0;
}

static int set_callee_state(struct bpf_verifier_env *env,
                            struct bpf_func_state *caller,
                            struct bpf_func_state *callee, int insn_idx)
{
        int i;

        /* copy r1 - r5 args that callee can access.  The copy includes parent
         * pointers, which connects us up to the liveness chain
         */
        for (i = BPF_REG_1; i <= BPF_REG_5; i++)
                callee->regs[i] = caller->regs[i];
        return 0;
}

static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
                           int *insn_idx)
{
        int subprog, target_insn;

        target_insn = *insn_idx + insn->imm + 1;
        subprog = find_subprog(env, target_insn);
        if (subprog < 0) {
                verbose(env, "verifier bug. No program starts at insn %d\n",
                        target_insn);
                return -EFAULT;
        }

        return __check_func_call(env, insn, insn_idx, subprog, set_callee_state);
}

static int set_map_elem_callback_state(struct bpf_verifier_env *env,
                                       struct bpf_func_state *caller,
                                       struct bpf_func_state *callee,
                                       int insn_idx)
{
        struct bpf_insn_aux_data *insn_aux = &env->insn_aux_data[insn_idx];
        struct bpf_map *map;
        int err;

        if (bpf_map_ptr_poisoned(insn_aux)) {
                verbose(env, "tail_call abusing map_ptr\n");
                return -EINVAL;
        }

        map = BPF_MAP_PTR(insn_aux->map_ptr_state);
        if (!map->ops->map_set_for_each_callback_args ||
            !map->ops->map_for_each_callback) {
                verbose(env, "callback function not allowed for map\n");
                return -ENOTSUPP;
        }

        err = map->ops->map_set_for_each_callback_args(env, caller, callee);
        if (err)
                return err;

        callee->in_callback_fn = true;
        return 0;
}

static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
{
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_func_state *caller, *callee;
        struct bpf_reg_state *r0;
        int err;

        callee = state->frame[state->curframe];
        r0 = &callee->regs[BPF_REG_0];
        if (r0->type == PTR_TO_STACK) {
                /* technically it's ok to return caller's stack pointer
                 * (or caller's caller's pointer) back to the caller,
                 * since these pointers are valid. Only current stack
                 * pointer will be invalid as soon as function exits,
                 * but let's be conservative
                 */
                verbose(env, "cannot return stack pointer to the caller\n");
                return -EINVAL;
        }

        state->curframe--;
        caller = state->frame[state->curframe];
        if (callee->in_callback_fn) {
                /* enforce R0 return value range [0, 1]. */
                struct tnum range = tnum_range(0, 1);

                if (r0->type != SCALAR_VALUE) {
                        verbose(env, "R0 not a scalar value\n");
                        return -EACCES;
                }
                if (!tnum_in(range, r0->var_off)) {
                        verbose_invalid_scalar(env, r0, &range, "callback return", "R0");
                        return -EINVAL;
                }
        } else {
                /* return to the caller whatever r0 had in the callee */
                caller->regs[BPF_REG_0] = *r0;
        }

        /* Transfer references to the caller */
        err = transfer_reference_state(caller, callee);
        if (err)
                return err;

        *insn_idx = callee->callsite + 1;
        if (env->log.level & BPF_LOG_LEVEL) {
                verbose(env, "returning from callee:\n");
                print_verifier_state(env, callee);
                verbose(env, "to caller at %d:\n", *insn_idx);
                print_verifier_state(env, caller);
        }
        /* clear everything in the callee */
        free_func_state(callee);
        state->frame[state->curframe + 1] = NULL;
        return 0;
}

static void do_refine_retval_range(struct bpf_reg_state *regs, int ret_type,
                                   int func_id,
                                   struct bpf_call_arg_meta *meta)
{
        struct bpf_reg_state *ret_reg = &regs[BPF_REG_0];

        if (ret_type != RET_INTEGER ||
            (func_id != BPF_FUNC_get_stack &&
             func_id != BPF_FUNC_probe_read_str &&
             func_id != BPF_FUNC_probe_read_kernel_str &&
             func_id != BPF_FUNC_probe_read_user_str))
                return;

        ret_reg->smax_value = meta->msize_max_value;
        ret_reg->s32_max_value = meta->msize_max_value;
        ret_reg->smin_value = -MAX_ERRNO;
        ret_reg->s32_min_value = -MAX_ERRNO;
        __reg_deduce_bounds(ret_reg);
        __reg_bound_offset(ret_reg);
        __update_reg_bounds(ret_reg);
}

static int
record_func_map(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
                int func_id, int insn_idx)
{
        struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
        struct bpf_map *map = meta->map_ptr;

        if (func_id != BPF_FUNC_tail_call &&
            func_id != BPF_FUNC_map_lookup_elem &&
            func_id != BPF_FUNC_map_update_elem &&
            func_id != BPF_FUNC_map_delete_elem &&
            func_id != BPF_FUNC_map_push_elem &&
            func_id != BPF_FUNC_map_pop_elem &&
            func_id != BPF_FUNC_map_peek_elem &&
            func_id != BPF_FUNC_for_each_map_elem &&
            func_id != BPF_FUNC_redirect_map)
                return 0;

        if (map == NULL) {
                verbose(env, "kernel subsystem misconfigured verifier\n");
                return -EINVAL;
        }

        /* In case of read-only, some additional restrictions
         * need to be applied in order to prevent altering the
         * state of the map from program side.
         */
        if ((map->map_flags & BPF_F_RDONLY_PROG) &&
            (func_id == BPF_FUNC_map_delete_elem ||
             func_id == BPF_FUNC_map_update_elem ||
             func_id == BPF_FUNC_map_push_elem ||
             func_id == BPF_FUNC_map_pop_elem)) {
                verbose(env, "write into map forbidden\n");
                return -EACCES;
        }

        if (!BPF_MAP_PTR(aux->map_ptr_state))
                bpf_map_ptr_store(aux, meta->map_ptr,
                                  !meta->map_ptr->bypass_spec_v1);
        else if (BPF_MAP_PTR(aux->map_ptr_state) != meta->map_ptr)
                bpf_map_ptr_store(aux, BPF_MAP_PTR_POISON,
                                  !meta->map_ptr->bypass_spec_v1);
        return 0;
}

static int
record_func_key(struct bpf_verifier_env *env, struct bpf_call_arg_meta *meta,
                int func_id, int insn_idx)
{
        struct bpf_insn_aux_data *aux = &env->insn_aux_data[insn_idx];
        struct bpf_reg_state *regs = cur_regs(env), *reg;
        struct bpf_map *map = meta->map_ptr;
        struct tnum range;
        u64 val;
        int err;

        if (func_id != BPF_FUNC_tail_call)
                return 0;
        if (!map || map->map_type != BPF_MAP_TYPE_PROG_ARRAY) {
                verbose(env, "kernel subsystem misconfigured verifier\n");
                return -EINVAL;
        }

        range = tnum_range(0, map->max_entries - 1);
        reg = &regs[BPF_REG_3];

        if (!register_is_const(reg) || !tnum_in(range, reg->var_off)) {
                bpf_map_key_store(aux, BPF_MAP_KEY_POISON);
                return 0;
        }

        err = mark_chain_precision(env, BPF_REG_3);
        if (err)
                return err;

        val = reg->var_off.value;
        if (bpf_map_key_unseen(aux))
                bpf_map_key_store(aux, val);
        else if (!bpf_map_key_poisoned(aux) &&
                  bpf_map_key_immediate(aux) != val)
                bpf_map_key_store(aux, BPF_MAP_KEY_POISON);
        return 0;
}

static int check_reference_leak(struct bpf_verifier_env *env)
{
        struct bpf_func_state *state = cur_func(env);
        int i;

        for (i = 0; i < state->acquired_refs; i++) {
                verbose(env, "Unreleased reference id=%d alloc_insn=%d\n",
                        state->refs[i].id, state->refs[i].insn_idx);
        }
        return state->acquired_refs ? -EINVAL : 0;
}

static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
                             int *insn_idx_p)
{
        const struct bpf_func_proto *fn = NULL;
        struct bpf_reg_state *regs;
        struct bpf_call_arg_meta meta;
        int insn_idx = *insn_idx_p;
        bool changes_data;
        int i, err, func_id;

        /* find function prototype */
        func_id = insn->imm;
        if (func_id < 0 || func_id >= __BPF_FUNC_MAX_ID) {
                verbose(env, "invalid func %s#%d\n", func_id_name(func_id),
                        func_id);
                return -EINVAL;
        }

        if (env->ops->get_func_proto)
                fn = env->ops->get_func_proto(func_id, env->prog);
        if (!fn) {
                verbose(env, "unknown func %s#%d\n", func_id_name(func_id),
                        func_id);
                return -EINVAL;
        }

        /* eBPF programs must be GPL compatible to use GPL-ed functions */
        if (!env->prog->gpl_compatible && fn->gpl_only) {
                verbose(env, "cannot call GPL-restricted function from non-GPL compatible program\n");
                return -EINVAL;
        }

        if (fn->allowed && !fn->allowed(env->prog)) {
                verbose(env, "helper call is not allowed in probe\n");
                return -EINVAL;
        }

        /* With LD_ABS/IND some JITs save/restore skb from r1. */
        changes_data = bpf_helper_changes_pkt_data(fn->func);
        if (changes_data && fn->arg1_type != ARG_PTR_TO_CTX) {
                verbose(env, "kernel subsystem misconfigured func %s#%d: r1 != ctx\n",
                        func_id_name(func_id), func_id);
                return -EINVAL;
        }

        memset(&meta, 0, sizeof(meta));
        meta.pkt_access = fn->pkt_access;

        err = check_func_proto(fn, func_id);
        if (err) {
                verbose(env, "kernel subsystem misconfigured func %s#%d\n",
                        func_id_name(func_id), func_id);
                return err;
        }

        meta.func_id = func_id;
        /* check args */
        for (i = 0; i < MAX_BPF_FUNC_REG_ARGS; i++) {
                err = check_func_arg(env, i, &meta, fn);
                if (err)
                        return err;
        }

        err = record_func_map(env, &meta, func_id, insn_idx);
        if (err)
                return err;

        err = record_func_key(env, &meta, func_id, insn_idx);
        if (err)
                return err;

        /* Mark slots with STACK_MISC in case of raw mode, stack offset
         * is inferred from register state.
         */
        for (i = 0; i < meta.access_size; i++) {
                err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B,
                                       BPF_WRITE, -1, false);
                if (err)
                        return err;
        }

        if (func_id == BPF_FUNC_tail_call) {
                err = check_reference_leak(env);
                if (err) {
                        verbose(env, "tail_call would lead to reference leak\n");
                        return err;
                }
        } else if (is_release_function(func_id)) {
                err = release_reference(env, meta.ref_obj_id);
                if (err) {
                        verbose(env, "func %s#%d reference has not been acquired before\n",
                                func_id_name(func_id), func_id);
                        return err;
                }
        }

        regs = cur_regs(env);

        /* check that flags argument in get_local_storage(map, flags) is 0,
         * this is required because get_local_storage() can't return an error.
         */
        if (func_id == BPF_FUNC_get_local_storage &&
            !register_is_null(&regs[BPF_REG_2])) {
                verbose(env, "get_local_storage() doesn't support non-zero flags\n");
                return -EINVAL;
        }

        if (func_id == BPF_FUNC_for_each_map_elem) {
                err = __check_func_call(env, insn, insn_idx_p, meta.subprogno,
                                        set_map_elem_callback_state);
                if (err < 0)
                        return -EINVAL;
        }

        /* reset caller saved regs */
        for (i = 0; i < CALLER_SAVED_REGS; i++) {
                mark_reg_not_init(env, regs, caller_saved[i]);
                check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
        }

        /* helper call returns 64-bit value. */
        regs[BPF_REG_0].subreg_def = DEF_NOT_SUBREG;

        /* update return register (already marked as written above) */
        if (fn->ret_type == RET_INTEGER) {
                /* sets type to SCALAR_VALUE */
                mark_reg_unknown(env, regs, BPF_REG_0);
        } else if (fn->ret_type == RET_VOID) {
                regs[BPF_REG_0].type = NOT_INIT;
        } else if (fn->ret_type == RET_PTR_TO_MAP_VALUE_OR_NULL ||
                   fn->ret_type == RET_PTR_TO_MAP_VALUE) {
                /* There is no offset yet applied, variable or fixed */
                mark_reg_known_zero(env, regs, BPF_REG_0);
                /* remember map_ptr, so that check_map_access()
                 * can check 'value_size' boundary of memory access
                 * to map element returned from bpf_map_lookup_elem()
                 */
                if (meta.map_ptr == NULL) {
                        verbose(env,
                                "kernel subsystem misconfigured verifier\n");
                        return -EINVAL;
                }
                regs[BPF_REG_0].map_ptr = meta.map_ptr;
                if (fn->ret_type == RET_PTR_TO_MAP_VALUE) {
                        regs[BPF_REG_0].type = PTR_TO_MAP_VALUE;
                        if (map_value_has_spin_lock(meta.map_ptr))
                                regs[BPF_REG_0].id = ++env->id_gen;
                } else {
                        regs[BPF_REG_0].type = PTR_TO_MAP_VALUE_OR_NULL;
                }
        } else if (fn->ret_type == RET_PTR_TO_SOCKET_OR_NULL) {
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_SOCKET_OR_NULL;
        } else if (fn->ret_type == RET_PTR_TO_SOCK_COMMON_OR_NULL) {
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_SOCK_COMMON_OR_NULL;
        } else if (fn->ret_type == RET_PTR_TO_TCP_SOCK_OR_NULL) {
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_TCP_SOCK_OR_NULL;
        } else if (fn->ret_type == RET_PTR_TO_ALLOC_MEM_OR_NULL) {
                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = PTR_TO_MEM_OR_NULL;
                regs[BPF_REG_0].mem_size = meta.mem_size;
        } else if (fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL ||
                   fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID) {
                const struct btf_type *t;

                mark_reg_known_zero(env, regs, BPF_REG_0);
                t = btf_type_skip_modifiers(meta.ret_btf, meta.ret_btf_id, NULL);
                if (!btf_type_is_struct(t)) {
                        u32 tsize;
                        const struct btf_type *ret;
                        const char *tname;

                        /* resolve the type size of ksym. */
                        ret = btf_resolve_size(meta.ret_btf, t, &tsize);
                        if (IS_ERR(ret)) {
                                tname = btf_name_by_offset(meta.ret_btf, t->name_off);
                                verbose(env, "unable to resolve the size of type '%s': %ld\n",
                                        tname, PTR_ERR(ret));
                                return -EINVAL;
                        }
                        regs[BPF_REG_0].type =
                                fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
                                PTR_TO_MEM : PTR_TO_MEM_OR_NULL;
                        regs[BPF_REG_0].mem_size = tsize;
                } else {
                        regs[BPF_REG_0].type =
                                fn->ret_type == RET_PTR_TO_MEM_OR_BTF_ID ?
                                PTR_TO_BTF_ID : PTR_TO_BTF_ID_OR_NULL;
                        regs[BPF_REG_0].btf = meta.ret_btf;
                        regs[BPF_REG_0].btf_id = meta.ret_btf_id;
                }
        } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL ||
                   fn->ret_type == RET_PTR_TO_BTF_ID) {
                int ret_btf_id;

                mark_reg_known_zero(env, regs, BPF_REG_0);
                regs[BPF_REG_0].type = fn->ret_type == RET_PTR_TO_BTF_ID ?
                                                     PTR_TO_BTF_ID :
                                                     PTR_TO_BTF_ID_OR_NULL;
                ret_btf_id = *fn->ret_btf_id;
                if (ret_btf_id == 0) {
                        verbose(env, "invalid return type %d of func %s#%d\n",
                                fn->ret_type, func_id_name(func_id), func_id);
                        return -EINVAL;
                }
                /* current BPF helper definitions are only coming from
                 * built-in code with type IDs from  vmlinux BTF
                 */
                regs[BPF_REG_0].btf = btf_vmlinux;
                regs[BPF_REG_0].btf_id = ret_btf_id;
        } else {
                verbose(env, "unknown return type %d of func %s#%d\n",
                        fn->ret_type, func_id_name(func_id), func_id);
                return -EINVAL;
        }

        if (reg_type_may_be_null(regs[BPF_REG_0].type))
                regs[BPF_REG_0].id = ++env->id_gen;

        if (is_ptr_cast_function(func_id)) {
                /* For release_reference() */
                regs[BPF_REG_0].ref_obj_id = meta.ref_obj_id;
        } else if (is_acquire_function(func_id, meta.map_ptr)) {
                int id = acquire_reference_state(env, insn_idx);

                if (id < 0)
                        return id;
                /* For mark_ptr_or_null_reg() */
                regs[BPF_REG_0].id = id;
                /* For release_reference() */
                regs[BPF_REG_0].ref_obj_id = id;
        }

        do_refine_retval_range(regs, fn->ret_type, func_id, &meta);

        err = check_map_func_compatibility(env, meta.map_ptr, func_id);
        if (err)
                return err;

        if ((func_id == BPF_FUNC_get_stack ||
             func_id == BPF_FUNC_get_task_stack) &&
            !env->prog->has_callchain_buf) {
                const char *err_str;

#ifdef CONFIG_PERF_EVENTS
                err = get_callchain_buffers(sysctl_perf_event_max_stack);
                err_str = "cannot get callchain buffer for func %s#%d\n";
#else
                err = -ENOTSUPP;
                err_str = "func %s#%d not supported without CONFIG_PERF_EVENTS\n";
#endif
                if (err) {
                        verbose(env, err_str, func_id_name(func_id), func_id);
                        return err;
                }

                env->prog->has_callchain_buf = true;
        }

        if (func_id == BPF_FUNC_get_stackid || func_id == BPF_FUNC_get_stack)
                env->prog->call_get_stack = true;

        if (changes_data)
                clear_all_pkt_pointers(env);
        return 0;
}

static bool signed_add_overflows(s64 a, s64 b)
{
        /* Do the add in u64, where overflow is well-defined */
        s64 res = (s64)((u64)a + (u64)b);

        if (b < 0)
                return res > a;
        return res < a;
}

static bool signed_add32_overflows(s32 a, s32 b)
{
        /* Do the add in u32, where overflow is well-defined */
        s32 res = (s32)((u32)a + (u32)b);

        if (b < 0)
                return res > a;
        return res < a;
}

static bool signed_sub_overflows(s64 a, s64 b)
{
        /* Do the sub in u64, where overflow is well-defined */
        s64 res = (s64)((u64)a - (u64)b);

        if (b < 0)
                return res < a;
        return res > a;
}

static bool signed_sub32_overflows(s32 a, s32 b)
{
        /* Do the sub in u32, where overflow is well-defined */
        s32 res = (s32)((u32)a - (u32)b);

        if (b < 0)
                return res < a;
        return res > a;
}

static bool check_reg_sane_offset(struct bpf_verifier_env *env,
                                  const struct bpf_reg_state *reg,
                                  enum bpf_reg_type type)
{
        bool known = tnum_is_const(reg->var_off);
        s64 val = reg->var_off.value;
        s64 smin = reg->smin_value;

        if (known && (val >= BPF_MAX_VAR_OFF || val <= -BPF_MAX_VAR_OFF)) {
                verbose(env, "math between %s pointer and %lld is not allowed\n",
                        reg_type_str[type], val);
                return false;
        }

        if (reg->off >= BPF_MAX_VAR_OFF || reg->off <= -BPF_MAX_VAR_OFF) {
                verbose(env, "%s pointer offset %d is not allowed\n",
                        reg_type_str[type], reg->off);
                return false;
        }

        if (smin == S64_MIN) {
                verbose(env, "math between %s pointer and register with unbounded min value is not allowed\n",
                        reg_type_str[type]);
                return false;
        }

        if (smin >= BPF_MAX_VAR_OFF || smin <= -BPF_MAX_VAR_OFF) {
                verbose(env, "value %lld makes %s pointer be out of bounds\n",
                        smin, reg_type_str[type]);
                return false;
        }

        return true;
}

static struct bpf_insn_aux_data *cur_aux(struct bpf_verifier_env *env)
{
        return &env->insn_aux_data[env->insn_idx];
}

static int retrieve_ptr_limit(const struct bpf_reg_state *ptr_reg,
                              u32 *ptr_limit, u8 opcode, bool off_is_neg)
{
        bool mask_to_left = (opcode == BPF_ADD &&  off_is_neg) ||
                            (opcode == BPF_SUB && !off_is_neg);
        u32 off;

        switch (ptr_reg->type) {
        case PTR_TO_STACK:
                /* Indirect variable offset stack access is prohibited in
                 * unprivileged mode so it's not handled here.
                 */
                off = ptr_reg->off + ptr_reg->var_off.value;
                if (mask_to_left)
                        *ptr_limit = MAX_BPF_STACK + off;
                else
                        *ptr_limit = -off;
                return 0;
        case PTR_TO_MAP_KEY:
                /* Currently, this code is not exercised as the only use
                 * is bpf_for_each_map_elem() helper which requires
                 * bpf_capble. The code has been tested manually for
                 * future use.
                 */
                if (mask_to_left) {
                        *ptr_limit = ptr_reg->umax_value + ptr_reg->off;
                } else {
                        off = ptr_reg->smin_value + ptr_reg->off;
                        *ptr_limit = ptr_reg->map_ptr->key_size - off;
                }
                return 0;
        case PTR_TO_MAP_VALUE:
                if (mask_to_left) {
                        *ptr_limit = ptr_reg->umax_value + ptr_reg->off;
                } else {
                        off = ptr_reg->smin_value + ptr_reg->off;
                        *ptr_limit = ptr_reg->map_ptr->value_size - off;
                }
                return 0;
        default:
                return -EINVAL;
        }
}

static bool can_skip_alu_sanitation(const struct bpf_verifier_env *env,
                                    const struct bpf_insn *insn)
{
        return env->bypass_spec_v1 || BPF_SRC(insn->code) == BPF_K;
}

static int update_alu_sanitation_state(struct bpf_insn_aux_data *aux,
                                       u32 alu_state, u32 alu_limit)
{
        /* If we arrived here from different branches with different
         * state or limits to sanitize, then this won't work.
         */
        if (aux->alu_state &&
            (aux->alu_state != alu_state ||
             aux->alu_limit != alu_limit))
                return -EACCES;

        /* Corresponding fixup done in do_misc_fixups(). */
        aux->alu_state = alu_state;
        aux->alu_limit = alu_limit;
        return 0;
}

static int sanitize_val_alu(struct bpf_verifier_env *env,
                            struct bpf_insn *insn)
{
        struct bpf_insn_aux_data *aux = cur_aux(env);

        if (can_skip_alu_sanitation(env, insn))
                return 0;

        return update_alu_sanitation_state(aux, BPF_ALU_NON_POINTER, 0);
}

static int sanitize_ptr_alu(struct bpf_verifier_env *env,
                            struct bpf_insn *insn,
                            const struct bpf_reg_state *ptr_reg,
                            struct bpf_reg_state *dst_reg,
                            bool off_is_neg)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_insn_aux_data *aux = cur_aux(env);
        bool ptr_is_dst_reg = ptr_reg == dst_reg;
        u8 opcode = BPF_OP(insn->code);
        u32 alu_state, alu_limit;
        struct bpf_reg_state tmp;
        bool ret;

        if (can_skip_alu_sanitation(env, insn))
                return 0;

        /* We already marked aux for masking from non-speculative
         * paths, thus we got here in the first place. We only care
         * to explore bad access from here.
         */
        if (vstate->speculative)
                goto do_sim;

        alu_state  = off_is_neg ? BPF_ALU_NEG_VALUE : 0;
        alu_state |= ptr_is_dst_reg ?
                     BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST;

        if (retrieve_ptr_limit(ptr_reg, &alu_limit, opcode, off_is_neg))
                return 0;
        if (update_alu_sanitation_state(aux, alu_state, alu_limit))
                return -EACCES;
do_sim:
        /* Simulate and find potential out-of-bounds access under
         * speculative execution from truncation as a result of
         * masking when off was not within expected range. If off
         * sits in dst, then we temporarily need to move ptr there
         * to simulate dst (== 0) +/-= ptr. Needed, for example,
         * for cases where we use K-based arithmetic in one direction
         * and truncated reg-based in the other in order to explore
         * bad access.
         */
        if (!ptr_is_dst_reg) {
                tmp = *dst_reg;
                *dst_reg = *ptr_reg;
        }
        ret = push_stack(env, env->insn_idx + 1, env->insn_idx, true);
        if (!ptr_is_dst_reg && ret)
                *dst_reg = tmp;
        return !ret ? -EFAULT : 0;
}

/* check that stack access falls within stack limits and that 'reg' doesn't
 * have a variable offset.
 *
 * Variable offset is prohibited for unprivileged mode for simplicity since it
 * requires corresponding support in Spectre masking for stack ALU.  See also
 * retrieve_ptr_limit().
 *
 *
 * 'off' includes 'reg->off'.
 */
static int check_stack_access_for_ptr_arithmetic(
                                struct bpf_verifier_env *env,
                                int regno,
                                const struct bpf_reg_state *reg,
                                int off)
{
        if (!tnum_is_const(reg->var_off)) {
                char tn_buf[48];

                tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
                verbose(env, "R%d variable stack access prohibited for !root, var_off=%s off=%d\n",
                        regno, tn_buf, off);
                return -EACCES;
        }

        if (off >= 0 || off < -MAX_BPF_STACK) {
                verbose(env, "R%d stack pointer arithmetic goes out of range, "
                        "prohibited for !root; off=%d\n", regno, off);
                return -EACCES;
        }

        return 0;
}


/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
 * Caller should also handle BPF_MOV case separately.
 * If we return -EACCES, caller may want to try again treating pointer as a
 * scalar.  So we only emit a diagnostic if !env->allow_ptr_leaks.
 */
static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
                                   struct bpf_insn *insn,
                                   const struct bpf_reg_state *ptr_reg,
                                   const struct bpf_reg_state *off_reg)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *regs = state->regs, *dst_reg;
        bool known = tnum_is_const(off_reg->var_off);
        s64 smin_val = off_reg->smin_value, smax_val = off_reg->smax_value,
            smin_ptr = ptr_reg->smin_value, smax_ptr = ptr_reg->smax_value;
        u64 umin_val = off_reg->umin_value, umax_val = off_reg->umax_value,
            umin_ptr = ptr_reg->umin_value, umax_ptr = ptr_reg->umax_value;
        u32 dst = insn->dst_reg, src = insn->src_reg;
        u8 opcode = BPF_OP(insn->code);
        int ret;

        dst_reg = &regs[dst];

        if ((known && (smin_val != smax_val || umin_val != umax_val)) ||
            smin_val > smax_val || umin_val > umax_val) {
                /* Taint dst register if offset had invalid bounds derived from
                 * e.g. dead branches.
                 */
                __mark_reg_unknown(env, dst_reg);
                return 0;
        }

        if (BPF_CLASS(insn->code) != BPF_ALU64) {
                /* 32-bit ALU ops on pointers produce (meaningless) scalars */
                if (opcode == BPF_SUB && env->allow_ptr_leaks) {
                        __mark_reg_unknown(env, dst_reg);
                        return 0;
                }

                verbose(env,
                        "R%d 32-bit pointer arithmetic prohibited\n",
                        dst);
                return -EACCES;
        }

        switch (ptr_reg->type) {
        case PTR_TO_MAP_VALUE_OR_NULL:
                verbose(env, "R%d pointer arithmetic on %s prohibited, null-check it first\n",
                        dst, reg_type_str[ptr_reg->type]);
                return -EACCES;
        case CONST_PTR_TO_MAP:
                /* smin_val represents the known value */
                if (known && smin_val == 0 && opcode == BPF_ADD)
                        break;
                fallthrough;
        case PTR_TO_PACKET_END:
        case PTR_TO_SOCKET:
        case PTR_TO_SOCKET_OR_NULL:
        case PTR_TO_SOCK_COMMON:
        case PTR_TO_SOCK_COMMON_OR_NULL:
        case PTR_TO_TCP_SOCK:
        case PTR_TO_TCP_SOCK_OR_NULL:
        case PTR_TO_XDP_SOCK:
                verbose(env, "R%d pointer arithmetic on %s prohibited\n",
                        dst, reg_type_str[ptr_reg->type]);
                return -EACCES;
        case PTR_TO_MAP_KEY:
        case PTR_TO_MAP_VALUE:
                if (!env->allow_ptr_leaks && !known && (smin_val < 0) != (smax_val < 0)) {
                        verbose(env, "R%d has unknown scalar with mixed signed bounds, pointer arithmetic with it prohibited for !root\n",
                                off_reg == dst_reg ? dst : src);
                        return -EACCES;
                }
                fallthrough;
        default:
                break;
        }

        /* In case of 'scalar += pointer', dst_reg inherits pointer type and id.
         * The id may be overwritten later if we create a new variable offset.
         */
        dst_reg->type = ptr_reg->type;
        dst_reg->id = ptr_reg->id;

        if (!check_reg_sane_offset(env, off_reg, ptr_reg->type) ||
            !check_reg_sane_offset(env, ptr_reg, ptr_reg->type))
                return -EINVAL;

        /* pointer types do not carry 32-bit bounds at the moment. */
        __mark_reg32_unbounded(dst_reg);

        switch (opcode) {
        case BPF_ADD:
                ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
                if (ret < 0) {
                        verbose(env, "R%d tried to add from different maps or paths\n", dst);
                        return ret;
                }
                /* We can take a fixed offset as long as it doesn't overflow
                 * the s32 'off' field
                 */
                if (known && (ptr_reg->off + smin_val ==
                              (s64)(s32)(ptr_reg->off + smin_val))) {
                        /* pointer += K.  Accumulate it into fixed offset */
                        dst_reg->smin_value = smin_ptr;
                        dst_reg->smax_value = smax_ptr;
                        dst_reg->umin_value = umin_ptr;
                        dst_reg->umax_value = umax_ptr;
                        dst_reg->var_off = ptr_reg->var_off;
                        dst_reg->off = ptr_reg->off + smin_val;
                        dst_reg->raw = ptr_reg->raw;
                        break;
                }
                /* A new variable offset is created.  Note that off_reg->off
                 * == 0, since it's a scalar.
                 * dst_reg gets the pointer type and since some positive
                 * integer value was added to the pointer, give it a new 'id'
                 * if it's a PTR_TO_PACKET.
                 * this creates a new 'base' pointer, off_reg (variable) gets
                 * added into the variable offset, and we copy the fixed offset
                 * from ptr_reg.
                 */
                if (signed_add_overflows(smin_ptr, smin_val) ||
                    signed_add_overflows(smax_ptr, smax_val)) {
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value = smin_ptr + smin_val;
                        dst_reg->smax_value = smax_ptr + smax_val;
                }
                if (umin_ptr + umin_val < umin_ptr ||
                    umax_ptr + umax_val < umax_ptr) {
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        dst_reg->umin_value = umin_ptr + umin_val;
                        dst_reg->umax_value = umax_ptr + umax_val;
                }
                dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
                dst_reg->off = ptr_reg->off;
                dst_reg->raw = ptr_reg->raw;
                if (reg_is_pkt_pointer(ptr_reg)) {
                        dst_reg->id = ++env->id_gen;
                        /* something was added to pkt_ptr, set range to zero */
                        memset(&dst_reg->raw, 0, sizeof(dst_reg->raw));
                }
                break;
        case BPF_SUB:
                ret = sanitize_ptr_alu(env, insn, ptr_reg, dst_reg, smin_val < 0);
                if (ret < 0) {
                        verbose(env, "R%d tried to sub from different maps or paths\n", dst);
                        return ret;
                }
                if (dst_reg == off_reg) {
                        /* scalar -= pointer.  Creates an unknown scalar */
                        verbose(env, "R%d tried to subtract pointer from scalar\n",
                                dst);
                        return -EACCES;
                }
                /* We don't allow subtraction from FP, because (according to
                 * test_verifier.c test "invalid fp arithmetic", JITs might not
                 * be able to deal with it.
                 */
                if (ptr_reg->type == PTR_TO_STACK) {
                        verbose(env, "R%d subtraction from stack pointer prohibited\n",
                                dst);
                        return -EACCES;
                }
                if (known && (ptr_reg->off - smin_val ==
                              (s64)(s32)(ptr_reg->off - smin_val))) {
                        /* pointer -= K.  Subtract it from fixed offset */
                        dst_reg->smin_value = smin_ptr;
                        dst_reg->smax_value = smax_ptr;
                        dst_reg->umin_value = umin_ptr;
                        dst_reg->umax_value = umax_ptr;
                        dst_reg->var_off = ptr_reg->var_off;
                        dst_reg->id = ptr_reg->id;
                        dst_reg->off = ptr_reg->off - smin_val;
                        dst_reg->raw = ptr_reg->raw;
                        break;
                }
                /* A new variable offset is created.  If the subtrahend is known
                 * nonnegative, then any reg->range we had before is still good.
                 */
                if (signed_sub_overflows(smin_ptr, smax_val) ||
                    signed_sub_overflows(smax_ptr, smin_val)) {
                        /* Overflow possible, we know nothing */
                        dst_reg->smin_value = S64_MIN;
                        dst_reg->smax_value = S64_MAX;
                } else {
                        dst_reg->smin_value = smin_ptr - smax_val;
                        dst_reg->smax_value = smax_ptr - smin_val;
                }
                if (umin_ptr < umax_val) {
                        /* Overflow possible, we know nothing */
                        dst_reg->umin_value = 0;
                        dst_reg->umax_value = U64_MAX;
                } else {
                        /* Cannot overflow (as long as bounds are consistent) */
                        dst_reg->umin_value = umin_ptr - umax_val;
                        dst_reg->umax_value = umax_ptr - umin_val;
                }
                dst_reg->var_off = tnum_sub(ptr_reg->var_off, off_reg->var_off);
                dst_reg->off = ptr_reg->off;
                dst_reg->raw = ptr_reg->raw;
                if (reg_is_pkt_pointer(ptr_reg)) {
                        dst_reg->id = ++env->id_gen;
                        /* something was added to pkt_ptr, set range to zero */
                        if (smin_val < 0)
                                memset(&dst_reg->raw, 0, sizeof(dst_reg->raw));
                }
                break;
        case BPF_AND:
        case BPF_OR:
        case BPF_XOR:
                /* bitwise ops on pointers are troublesome, prohibit. */
                verbose(env, "R%d bitwise operator %s on pointer prohibited\n",
                        dst, bpf_alu_string[opcode >> 4]);
                return -EACCES;
        default:
                /* other operators (e.g. MUL,LSH) produce non-pointer results */
                verbose(env, "R%d pointer arithmetic with %s operator prohibited\n",
                        dst, bpf_alu_string[opcode >> 4]);
                return -EACCES;
        }

        if (!check_reg_sane_offset(env, dst_reg, ptr_reg->type))
                return -EINVAL;

        __update_reg_bounds(dst_reg);
        __reg_deduce_bounds(dst_reg);
        __reg_bound_offset(dst_reg);

        /* For unprivileged we require that resulting offset must be in bounds
         * in order to be able to sanitize access later on.
         */
        if (!env->bypass_spec_v1) {
                if (dst_reg->type == PTR_TO_MAP_VALUE &&
                    check_map_access(env, dst, dst_reg->off, 1, false)) {
                        verbose(env, "R%d pointer arithmetic of map value goes out of range, "
                                "prohibited for !root\n", dst);
                        return -EACCES;
                } else if (dst_reg->type == PTR_TO_STACK &&
                           check_stack_access_for_ptr_arithmetic(
                                   env, dst, dst_reg, dst_reg->off +
                                   dst_reg->var_off.value)) {
                        return -EACCES;
                }
        }

        return 0;
}

static void scalar32_min_max_add(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        s32 smin_val = src_reg->s32_min_value;
        s32 smax_val = src_reg->s32_max_value;
        u32 umin_val = src_reg->u32_min_value;
        u32 umax_val = src_reg->u32_max_value;

        if (signed_add32_overflows(dst_reg->s32_min_value, smin_val) ||
            signed_add32_overflows(dst_reg->s32_max_value, smax_val)) {
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        } else {
                dst_reg->s32_min_value += smin_val;
                dst_reg->s32_max_value += smax_val;
        }
        if (dst_reg->u32_min_value + umin_val < umin_val ||
            dst_reg->u32_max_value + umax_val < umax_val) {
                dst_reg->u32_min_value = 0;
                dst_reg->u32_max_value = U32_MAX;
        } else {
                dst_reg->u32_min_value += umin_val;
                dst_reg->u32_max_value += umax_val;
        }
}

static void scalar_min_max_add(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        s64 smin_val = src_reg->smin_value;
        s64 smax_val = src_reg->smax_value;
        u64 umin_val = src_reg->umin_value;
        u64 umax_val = src_reg->umax_value;

        if (signed_add_overflows(dst_reg->smin_value, smin_val) ||
            signed_add_overflows(dst_reg->smax_value, smax_val)) {
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        } else {
                dst_reg->smin_value += smin_val;
                dst_reg->smax_value += smax_val;
        }
        if (dst_reg->umin_value + umin_val < umin_val ||
            dst_reg->umax_value + umax_val < umax_val) {
                dst_reg->umin_value = 0;
                dst_reg->umax_value = U64_MAX;
        } else {
                dst_reg->umin_value += umin_val;
                dst_reg->umax_value += umax_val;
        }
}

static void scalar32_min_max_sub(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        s32 smin_val = src_reg->s32_min_value;
        s32 smax_val = src_reg->s32_max_value;
        u32 umin_val = src_reg->u32_min_value;
        u32 umax_val = src_reg->u32_max_value;

        if (signed_sub32_overflows(dst_reg->s32_min_value, smax_val) ||
            signed_sub32_overflows(dst_reg->s32_max_value, smin_val)) {
                /* Overflow possible, we know nothing */
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        } else {
                dst_reg->s32_min_value -= smax_val;
                dst_reg->s32_max_value -= smin_val;
        }
        if (dst_reg->u32_min_value < umax_val) {
                /* Overflow possible, we know nothing */
                dst_reg->u32_min_value = 0;
                dst_reg->u32_max_value = U32_MAX;
        } else {
                /* Cannot overflow (as long as bounds are consistent) */
                dst_reg->u32_min_value -= umax_val;
                dst_reg->u32_max_value -= umin_val;
        }
}

static void scalar_min_max_sub(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        s64 smin_val = src_reg->smin_value;
        s64 smax_val = src_reg->smax_value;
        u64 umin_val = src_reg->umin_value;
        u64 umax_val = src_reg->umax_value;

        if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
            signed_sub_overflows(dst_reg->smax_value, smin_val)) {
                /* Overflow possible, we know nothing */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        } else {
                dst_reg->smin_value -= smax_val;
                dst_reg->smax_value -= smin_val;
        }
        if (dst_reg->umin_value < umax_val) {
                /* Overflow possible, we know nothing */
                dst_reg->umin_value = 0;
                dst_reg->umax_value = U64_MAX;
        } else {
                /* Cannot overflow (as long as bounds are consistent) */
                dst_reg->umin_value -= umax_val;
                dst_reg->umax_value -= umin_val;
        }
}

static void scalar32_min_max_mul(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        s32 smin_val = src_reg->s32_min_value;
        u32 umin_val = src_reg->u32_min_value;
        u32 umax_val = src_reg->u32_max_value;

        if (smin_val < 0 || dst_reg->s32_min_value < 0) {
                /* Ain't nobody got time to multiply that sign */
                __mark_reg32_unbounded(dst_reg);
                return;
        }
        /* Both values are positive, so we can work with unsigned and
         * copy the result to signed (unless it exceeds S32_MAX).
         */
        if (umax_val > U16_MAX || dst_reg->u32_max_value > U16_MAX) {
                /* Potential overflow, we know nothing */
                __mark_reg32_unbounded(dst_reg);
                return;
        }
        dst_reg->u32_min_value *= umin_val;
        dst_reg->u32_max_value *= umax_val;
        if (dst_reg->u32_max_value > S32_MAX) {
                /* Overflow possible, we know nothing */
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        } else {
                dst_reg->s32_min_value = dst_reg->u32_min_value;
                dst_reg->s32_max_value = dst_reg->u32_max_value;
        }
}

static void scalar_min_max_mul(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        s64 smin_val = src_reg->smin_value;
        u64 umin_val = src_reg->umin_value;
        u64 umax_val = src_reg->umax_value;

        if (smin_val < 0 || dst_reg->smin_value < 0) {
                /* Ain't nobody got time to multiply that sign */
                __mark_reg64_unbounded(dst_reg);
                return;
        }
        /* Both values are positive, so we can work with unsigned and
         * copy the result to signed (unless it exceeds S64_MAX).
         */
        if (umax_val > U32_MAX || dst_reg->umax_value > U32_MAX) {
                /* Potential overflow, we know nothing */
                __mark_reg64_unbounded(dst_reg);
                return;
        }
        dst_reg->umin_value *= umin_val;
        dst_reg->umax_value *= umax_val;
        if (dst_reg->umax_value > S64_MAX) {
                /* Overflow possible, we know nothing */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        } else {
                dst_reg->smin_value = dst_reg->umin_value;
                dst_reg->smax_value = dst_reg->umax_value;
        }
}

static void scalar32_min_max_and(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_subreg_is_const(src_reg->var_off);
        bool dst_known = tnum_subreg_is_const(dst_reg->var_off);
        struct tnum var32_off = tnum_subreg(dst_reg->var_off);
        s32 smin_val = src_reg->s32_min_value;
        u32 umax_val = src_reg->u32_max_value;

        /* Assuming scalar64_min_max_and will be called so its safe
         * to skip updating register for known 32-bit case.
         */
        if (src_known && dst_known)
                return;

        /* We get our minimum from the var_off, since that's inherently
         * bitwise.  Our maximum is the minimum of the operands' maxima.
         */
        dst_reg->u32_min_value = var32_off.value;
        dst_reg->u32_max_value = min(dst_reg->u32_max_value, umax_val);
        if (dst_reg->s32_min_value < 0 || smin_val < 0) {
                /* Lose signed bounds when ANDing negative numbers,
                 * ain't nobody got time for that.
                 */
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        } else {
                /* ANDing two positives gives a positive, so safe to
                 * cast result into s64.
                 */
                dst_reg->s32_min_value = dst_reg->u32_min_value;
                dst_reg->s32_max_value = dst_reg->u32_max_value;
        }

}

static void scalar_min_max_and(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_is_const(src_reg->var_off);
        bool dst_known = tnum_is_const(dst_reg->var_off);
        s64 smin_val = src_reg->smin_value;
        u64 umax_val = src_reg->umax_value;

        if (src_known && dst_known) {
                __mark_reg_known(dst_reg, dst_reg->var_off.value);
                return;
        }

        /* We get our minimum from the var_off, since that's inherently
         * bitwise.  Our maximum is the minimum of the operands' maxima.
         */
        dst_reg->umin_value = dst_reg->var_off.value;
        dst_reg->umax_value = min(dst_reg->umax_value, umax_val);
        if (dst_reg->smin_value < 0 || smin_val < 0) {
                /* Lose signed bounds when ANDing negative numbers,
                 * ain't nobody got time for that.
                 */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        } else {
                /* ANDing two positives gives a positive, so safe to
                 * cast result into s64.
                 */
                dst_reg->smin_value = dst_reg->umin_value;
                dst_reg->smax_value = dst_reg->umax_value;
        }
        /* We may learn something more from the var_off */
        __update_reg_bounds(dst_reg);
}

static void scalar32_min_max_or(struct bpf_reg_state *dst_reg,
                                struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_subreg_is_const(src_reg->var_off);
        bool dst_known = tnum_subreg_is_const(dst_reg->var_off);
        struct tnum var32_off = tnum_subreg(dst_reg->var_off);
        s32 smin_val = src_reg->s32_min_value;
        u32 umin_val = src_reg->u32_min_value;

        /* Assuming scalar64_min_max_or will be called so it is safe
         * to skip updating register for known case.
         */
        if (src_known && dst_known)
                return;

        /* We get our maximum from the var_off, and our minimum is the
         * maximum of the operands' minima
         */
        dst_reg->u32_min_value = max(dst_reg->u32_min_value, umin_val);
        dst_reg->u32_max_value = var32_off.value | var32_off.mask;
        if (dst_reg->s32_min_value < 0 || smin_val < 0) {
                /* Lose signed bounds when ORing negative numbers,
                 * ain't nobody got time for that.
                 */
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        } else {
                /* ORing two positives gives a positive, so safe to
                 * cast result into s64.
                 */
                dst_reg->s32_min_value = dst_reg->u32_min_value;
                dst_reg->s32_max_value = dst_reg->u32_max_value;
        }
}

static void scalar_min_max_or(struct bpf_reg_state *dst_reg,
                              struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_is_const(src_reg->var_off);
        bool dst_known = tnum_is_const(dst_reg->var_off);
        s64 smin_val = src_reg->smin_value;
        u64 umin_val = src_reg->umin_value;

        if (src_known && dst_known) {
                __mark_reg_known(dst_reg, dst_reg->var_off.value);
                return;
        }

        /* We get our maximum from the var_off, and our minimum is the
         * maximum of the operands' minima
         */
        dst_reg->umin_value = max(dst_reg->umin_value, umin_val);
        dst_reg->umax_value = dst_reg->var_off.value | dst_reg->var_off.mask;
        if (dst_reg->smin_value < 0 || smin_val < 0) {
                /* Lose signed bounds when ORing negative numbers,
                 * ain't nobody got time for that.
                 */
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        } else {
                /* ORing two positives gives a positive, so safe to
                 * cast result into s64.
                 */
                dst_reg->smin_value = dst_reg->umin_value;
                dst_reg->smax_value = dst_reg->umax_value;
        }
        /* We may learn something more from the var_off */
        __update_reg_bounds(dst_reg);
}

static void scalar32_min_max_xor(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_subreg_is_const(src_reg->var_off);
        bool dst_known = tnum_subreg_is_const(dst_reg->var_off);
        struct tnum var32_off = tnum_subreg(dst_reg->var_off);
        s32 smin_val = src_reg->s32_min_value;

        /* Assuming scalar64_min_max_xor will be called so it is safe
         * to skip updating register for known case.
         */
        if (src_known && dst_known)
                return;

        /* We get both minimum and maximum from the var32_off. */
        dst_reg->u32_min_value = var32_off.value;
        dst_reg->u32_max_value = var32_off.value | var32_off.mask;

        if (dst_reg->s32_min_value >= 0 && smin_val >= 0) {
                /* XORing two positive sign numbers gives a positive,
                 * so safe to cast u32 result into s32.
                 */
                dst_reg->s32_min_value = dst_reg->u32_min_value;
                dst_reg->s32_max_value = dst_reg->u32_max_value;
        } else {
                dst_reg->s32_min_value = S32_MIN;
                dst_reg->s32_max_value = S32_MAX;
        }
}

static void scalar_min_max_xor(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        bool src_known = tnum_is_const(src_reg->var_off);
        bool dst_known = tnum_is_const(dst_reg->var_off);
        s64 smin_val = src_reg->smin_value;

        if (src_known && dst_known) {
                /* dst_reg->var_off.value has been updated earlier */
                __mark_reg_known(dst_reg, dst_reg->var_off.value);
                return;
        }

        /* We get both minimum and maximum from the var_off. */
        dst_reg->umin_value = dst_reg->var_off.value;
        dst_reg->umax_value = dst_reg->var_off.value | dst_reg->var_off.mask;

        if (dst_reg->smin_value >= 0 && smin_val >= 0) {
                /* XORing two positive sign numbers gives a positive,
                 * so safe to cast u64 result into s64.
                 */
                dst_reg->smin_value = dst_reg->umin_value;
                dst_reg->smax_value = dst_reg->umax_value;
        } else {
                dst_reg->smin_value = S64_MIN;
                dst_reg->smax_value = S64_MAX;
        }

        __update_reg_bounds(dst_reg);
}

static void __scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,
                                   u64 umin_val, u64 umax_val)
{
        /* We lose all sign bit information (except what we can pick
         * up from var_off)
         */
        dst_reg->s32_min_value = S32_MIN;
        dst_reg->s32_max_value = S32_MAX;
        /* If we might shift our top bit out, then we know nothing */
        if (umax_val > 31 || dst_reg->u32_max_value > 1ULL << (31 - umax_val)) {
                dst_reg->u32_min_value = 0;
                dst_reg->u32_max_value = U32_MAX;
        } else {
                dst_reg->u32_min_value <<= umin_val;
                dst_reg->u32_max_value <<= umax_val;
        }
}

static void scalar32_min_max_lsh(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        u32 umax_val = src_reg->u32_max_value;
        u32 umin_val = src_reg->u32_min_value;
        /* u32 alu operation will zext upper bits */
        struct tnum subreg = tnum_subreg(dst_reg->var_off);

        __scalar32_min_max_lsh(dst_reg, umin_val, umax_val);
        dst_reg->var_off = tnum_subreg(tnum_lshift(subreg, umin_val));
        /* Not required but being careful mark reg64 bounds as unknown so
         * that we are forced to pick them up from tnum and zext later and
         * if some path skips this step we are still safe.
         */
        __mark_reg64_unbounded(dst_reg);
        __update_reg32_bounds(dst_reg);
}

static void __scalar64_min_max_lsh(struct bpf_reg_state *dst_reg,
                                   u64 umin_val, u64 umax_val)
{
        /* Special case <<32 because it is a common compiler pattern to sign
         * extend subreg by doing <<32 s>>32. In this case if 32bit bounds are
         * positive we know this shift will also be positive so we can track
         * bounds correctly. Otherwise we lose all sign bit information except
         * what we can pick up from var_off. Perhaps we can generalize this
         * later to shifts of any length.
         */
        if (umin_val == 32 && umax_val == 32 && dst_reg->s32_max_value >= 0)
                dst_reg->smax_value = (s64)dst_reg->s32_max_value << 32;
        else
                dst_reg->smax_value = S64_MAX;

        if (umin_val == 32 && umax_val == 32 && dst_reg->s32_min_value >= 0)
                dst_reg->smin_value = (s64)dst_reg->s32_min_value << 32;
        else
                dst_reg->smin_value = S64_MIN;

        /* If we might shift our top bit out, then we know nothing */
        if (dst_reg->umax_value > 1ULL << (63 - umax_val)) {
                dst_reg->umin_value = 0;
                dst_reg->umax_value = U64_MAX;
        } else {
                dst_reg->umin_value <<= umin_val;
                dst_reg->umax_value <<= umax_val;
        }
}

static void scalar_min_max_lsh(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        u64 umax_val = src_reg->umax_value;
        u64 umin_val = src_reg->umin_value;

        /* scalar64 calc uses 32bit unshifted bounds so must be called first */
        __scalar64_min_max_lsh(dst_reg, umin_val, umax_val);
        __scalar32_min_max_lsh(dst_reg, umin_val, umax_val);

        dst_reg->var_off = tnum_lshift(dst_reg->var_off, umin_val);
        /* We may learn something more from the var_off */
        __update_reg_bounds(dst_reg);
}

static void scalar32_min_max_rsh(struct bpf_reg_state *dst_reg,
                                 struct bpf_reg_state *src_reg)
{
        struct tnum subreg = tnum_subreg(dst_reg->var_off);
        u32 umax_val = src_reg->u32_max_value;
        u32 umin_val = src_reg->u32_min_value;

        /* BPF_RSH is an unsigned shift.  If the value in dst_reg might
         * be negative, then either:
         * 1) src_reg might be zero, so the sign bit of the result is
         *    unknown, so we lose our signed bounds
         * 2) it's known negative, thus the unsigned bounds capture the
         *    signed bounds
         * 3) the signed bounds cross zero, so they tell us nothing
         *    about the result
         * If the value in dst_reg is known nonnegative, then again the
         * unsigned bounds capture the signed bounds.
         * Thus, in all cases it suffices to blow away our signed bounds
         * and rely on inferring new ones from the unsigned bounds and
         * var_off of the result.
         */
        dst_reg->s32_min_value = S32_MIN;
        dst_reg->s32_max_value = S32_MAX;

        dst_reg->var_off = tnum_rshift(subreg, umin_val);
        dst_reg->u32_min_value >>= umax_val;
        dst_reg->u32_max_value >>= umin_val;

        __mark_reg64_unbounded(dst_reg);
        __update_reg32_bounds(dst_reg);
}

static void scalar_min_max_rsh(struct bpf_reg_state *dst_reg,
                               struct bpf_reg_state *src_reg)
{
        u64 umax_val = src_reg->umax_value;
        u64 umin_val = src_reg->umin_value;

        /* BPF_RSH is an unsigned shift.  If the value in dst_reg might
         * be negative, then either:
         * 1) src_reg might be zero, so the sign bit of the result is
         *    unknown, so we lose our signed bounds
         * 2) it's known negative, thus the unsigned bounds capture the
         *    signed bounds
         * 3) the signed bounds cross zero, so they tell us nothing
         *    about the result
         * If the value in dst_reg is known nonnegative, then again the
         * unsigned bounds capture the signed bounds.
         * Thus, in all cases it suffices to blow away our signed bounds
         * and rely on inferring new ones from the unsigned bounds and
         * var_off of the result.
         */
        dst_reg->smin_value = S64_MIN;
        dst_reg->smax_value = S64_MAX;
        dst_reg->var_off = tnum_rshift(dst_reg->var_off, umin_val);
        dst_reg->umin_value >>= umax_val;
        dst_reg->umax_value >>= umin_val;

        /* Its not easy to operate on alu32 bounds here because it depends
         * on bits being shifted in. Take easy way out and mark unbounded
         * so we can recalculate later from tnum.
         */
        __mark_reg32_unbounded(dst_reg);
        __update_reg_bounds(dst_reg);
}

static void scalar32_min_max_arsh(struct bpf_reg_state *dst_reg,
                                  struct bpf_reg_state *src_reg)
{
        u64 umin_val = src_reg->u32_min_value;

        /* Upon reaching here, src_known is true and
         * umax_val is equal to umin_val.
         */
        dst_reg->s32_min_value = (u32)(((s32)dst_reg->s32_min_value) >> umin_val);
        dst_reg->s32_max_value = (u32)(((s32)dst_reg->s32_max_value) >> umin_val);

        dst_reg->var_off = tnum_arshift(tnum_subreg(dst_reg->var_off), umin_val, 32);

        /* blow away the dst_reg umin_value/umax_value and rely on
         * dst_reg var_off to refine the result.
         */
        dst_reg->u32_min_value = 0;
        dst_reg->u32_max_value = U32_MAX;

        __mark_reg64_unbounded(dst_reg);
        __update_reg32_bounds(dst_reg);
}

static void scalar_min_max_arsh(struct bpf_reg_state *dst_reg,
                                struct bpf_reg_state *src_reg)
{
        u64 umin_val = src_reg->umin_value;

        /* Upon reaching here, src_known is true and umax_val is equal
         * to umin_val.
         */
        dst_reg->smin_value >>= umin_val;
        dst_reg->smax_value >>= umin_val;

        dst_reg->var_off = tnum_arshift(dst_reg->var_off, umin_val, 64);

        /* blow away the dst_reg umin_value/umax_value and rely on
         * dst_reg var_off to refine the result.
         */
        dst_reg->umin_value = 0;
        dst_reg->umax_value = U64_MAX;

        /* Its not easy to operate on alu32 bounds here because it depends
         * on bits being shifted in from upper 32-bits. Take easy way out
         * and mark unbounded so we can recalculate later from tnum.
         */
        __mark_reg32_unbounded(dst_reg);
        __update_reg_bounds(dst_reg);
}

/* WARNING: This function does calculations on 64-bit values, but the actual
 * execution may occur on 32-bit values. Therefore, things like bitshifts
 * need extra checks in the 32-bit case.
 */
static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
                                      struct bpf_insn *insn,
                                      struct bpf_reg_state *dst_reg,
                                      struct bpf_reg_state src_reg)
{
        struct bpf_reg_state *regs = cur_regs(env);
        u8 opcode = BPF_OP(insn->code);
        bool src_known;
        s64 smin_val, smax_val;
        u64 umin_val, umax_val;
        s32 s32_min_val, s32_max_val;
        u32 u32_min_val, u32_max_val;
        u64 insn_bitness = (BPF_CLASS(insn->code) == BPF_ALU64) ? 64 : 32;
        u32 dst = insn->dst_reg;
        int ret;
        bool alu32 = (BPF_CLASS(insn->code) != BPF_ALU64);

        smin_val = src_reg.smin_value;
        smax_val = src_reg.smax_value;
        umin_val = src_reg.umin_value;
        umax_val = src_reg.umax_value;

        s32_min_val = src_reg.s32_min_value;
        s32_max_val = src_reg.s32_max_value;
        u32_min_val = src_reg.u32_min_value;
        u32_max_val = src_reg.u32_max_value;

        if (alu32) {
                src_known = tnum_subreg_is_const(src_reg.var_off);
                if ((src_known &&
                     (s32_min_val != s32_max_val || u32_min_val != u32_max_val)) ||
                    s32_min_val > s32_max_val || u32_min_val > u32_max_val) {
                        /* Taint dst register if offset had invalid bounds
                         * derived from e.g. dead branches.
                         */
                        __mark_reg_unknown(env, dst_reg);
                        return 0;
                }
        } else {
                src_known = tnum_is_const(src_reg.var_off);
                if ((src_known &&
                     (smin_val != smax_val || umin_val != umax_val)) ||
                    smin_val > smax_val || umin_val > umax_val) {
                        /* Taint dst register if offset had invalid bounds
                         * derived from e.g. dead branches.
                         */
                        __mark_reg_unknown(env, dst_reg);
                        return 0;
                }
        }

        if (!src_known &&
            opcode != BPF_ADD && opcode != BPF_SUB && opcode != BPF_AND) {
                __mark_reg_unknown(env, dst_reg);
                return 0;
        }

        /* Calculate sign/unsigned bounds and tnum for alu32 and alu64 bit ops.
         * There are two classes of instructions: The first class we track both
         * alu32 and alu64 sign/unsigned bounds independently this provides the
         * greatest amount of precision when alu operations are mixed with jmp32
         * operations. These operations are BPF_ADD, BPF_SUB, BPF_MUL, BPF_ADD,
         * and BPF_OR. This is possible because these ops have fairly easy to
         * understand and calculate behavior in both 32-bit and 64-bit alu ops.
         * See alu32 verifier tests for examples. The second class of
         * operations, BPF_LSH, BPF_RSH, and BPF_ARSH, however are not so easy
         * with regards to tracking sign/unsigned bounds because the bits may
         * cross subreg boundaries in the alu64 case. When this happens we mark
         * the reg unbounded in the subreg bound space and use the resulting
         * tnum to calculate an approximation of the sign/unsigned bounds.
         */
        switch (opcode) {
        case BPF_ADD:
                ret = sanitize_val_alu(env, insn);
                if (ret < 0) {
                        verbose(env, "R%d tried to add from different pointers or scalars\n", dst);
                        return ret;
                }
                scalar32_min_max_add(dst_reg, &src_reg);
                scalar_min_max_add(dst_reg, &src_reg);
                dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
                break;
        case BPF_SUB:
                ret = sanitize_val_alu(env, insn);
                if (ret < 0) {
                        verbose(env, "R%d tried to sub from different pointers or scalars\n", dst);
                        return ret;
                }
                scalar32_min_max_sub(dst_reg, &src_reg);
                scalar_min_max_sub(dst_reg, &src_reg);
                dst_reg->var_off = tnum_sub(dst_reg->var_off, src_reg.var_off);
                break;
        case BPF_MUL:
                dst_reg->var_off = tnum_mul(dst_reg->var_off, src_reg.var_off);
                scalar32_min_max_mul(dst_reg, &src_reg);
                scalar_min_max_mul(dst_reg, &src_reg);
                break;
        case BPF_AND:
                dst_reg->var_off = tnum_and(dst_reg->var_off, src_reg.var_off);
                scalar32_min_max_and(dst_reg, &src_reg);
                scalar_min_max_and(dst_reg, &src_reg);
                break;
        case BPF_OR:
                dst_reg->var_off = tnum_or(dst_reg->var_off, src_reg.var_off);
                scalar32_min_max_or(dst_reg, &src_reg);
                scalar_min_max_or(dst_reg, &src_reg);
                break;
        case BPF_XOR:
                dst_reg->var_off = tnum_xor(dst_reg->var_off, src_reg.var_off);
                scalar32_min_max_xor(dst_reg, &src_reg);
                scalar_min_max_xor(dst_reg, &src_reg);
                break;
        case BPF_LSH:
                if (umax_val >= insn_bitness) {
                        /* Shifts greater than 31 or 63 are undefined.
                         * This includes shifts by a negative number.
                         */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        break;
                }
                if (alu32)
                        scalar32_min_max_lsh(dst_reg, &src_reg);
                else
                        scalar_min_max_lsh(dst_reg, &src_reg);
                break;
        case BPF_RSH:
                if (umax_val >= insn_bitness) {
                        /* Shifts greater than 31 or 63 are undefined.
                         * This includes shifts by a negative number.
                         */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        break;
                }
                if (alu32)
                        scalar32_min_max_rsh(dst_reg, &src_reg);
                else
                        scalar_min_max_rsh(dst_reg, &src_reg);
                break;
        case BPF_ARSH:
                if (umax_val >= insn_bitness) {
                        /* Shifts greater than 31 or 63 are undefined.
                         * This includes shifts by a negative number.
                         */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        break;
                }
                if (alu32)
                        scalar32_min_max_arsh(dst_reg, &src_reg);
                else
                        scalar_min_max_arsh(dst_reg, &src_reg);
                break;
        default:
                mark_reg_unknown(env, regs, insn->dst_reg);
                break;
        }

        /* ALU32 ops are zero extended into 64bit register */
        if (alu32)
                zext_32_to_64(dst_reg);

        __update_reg_bounds(dst_reg);
        __reg_deduce_bounds(dst_reg);
        __reg_bound_offset(dst_reg);
        return 0;
}

/* Handles ALU ops other than BPF_END, BPF_NEG and BPF_MOV: computes new min/max
 * and var_off.
 */
static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
                                   struct bpf_insn *insn)
{
        struct bpf_verifier_state *vstate = env->cur_state;
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *regs = state->regs, *dst_reg, *src_reg;
        struct bpf_reg_state *ptr_reg = NULL, off_reg = {0};
        u8 opcode = BPF_OP(insn->code);
        int err;

        dst_reg = &regs[insn->dst_reg];
        src_reg = NULL;
        if (dst_reg->type != SCALAR_VALUE)
                ptr_reg = dst_reg;
        else
                /* Make sure ID is cleared otherwise dst_reg min/max could be
                 * incorrectly propagated into other registers by find_equal_scalars()
                 */
                dst_reg->id = 0;
        if (BPF_SRC(insn->code) == BPF_X) {
                src_reg = &regs[insn->src_reg];
                if (src_reg->type != SCALAR_VALUE) {
                        if (dst_reg->type != SCALAR_VALUE) {
                                /* Combining two pointers by any ALU op yields
                                 * an arbitrary scalar. Disallow all math except
                                 * pointer subtraction
                                 */
                                if (opcode == BPF_SUB && env->allow_ptr_leaks) {
                                        mark_reg_unknown(env, regs, insn->dst_reg);
                                        return 0;
                                }
                                verbose(env, "R%d pointer %s pointer prohibited\n",
                                        insn->dst_reg,
                                        bpf_alu_string[opcode >> 4]);
                                return -EACCES;
                        } else {
                                /* scalar += pointer
                                 * This is legal, but we have to reverse our
                                 * src/dest handling in computing the range
                                 */
                                err = mark_chain_precision(env, insn->dst_reg);
                                if (err)
                                        return err;
                                return adjust_ptr_min_max_vals(env, insn,
                                                               src_reg, dst_reg);
                        }
                } else if (ptr_reg) {
                        /* pointer += scalar */
                        err = mark_chain_precision(env, insn->src_reg);
                        if (err)
                                return err;
                        return adjust_ptr_min_max_vals(env, insn,
                                                       dst_reg, src_reg);
                }
        } else {
                /* Pretend the src is a reg with a known value, since we only
                 * need to be able to read from this state.
                 */
                off_reg.type = SCALAR_VALUE;
                __mark_reg_known(&off_reg, insn->imm);
                src_reg = &off_reg;
                if (ptr_reg) /* pointer += K */
                        return adjust_ptr_min_max_vals(env, insn,
                                                       ptr_reg, src_reg);
        }

        /* Got here implies adding two SCALAR_VALUEs */
        if (WARN_ON_ONCE(ptr_reg)) {
                print_verifier_state(env, state);
                verbose(env, "verifier internal error: unexpected ptr_reg\n");
                return -EINVAL;
        }
        if (WARN_ON(!src_reg)) {
                print_verifier_state(env, state);
                verbose(env, "verifier internal error: no src_reg\n");
                return -EINVAL;
        }
        return adjust_scalar_min_max_vals(env, insn, dst_reg, *src_reg);
}

/* check validity of 32-bit and 64-bit arithmetic operations */
static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env);
        u8 opcode = BPF_OP(insn->code);
        int err;

        if (opcode == BPF_END || opcode == BPF_NEG) {
                if (opcode == BPF_NEG) {
                        if (BPF_SRC(insn->code) != 0 ||
                            insn->src_reg != BPF_REG_0 ||
                            insn->off != 0 || insn->imm != 0) {
                                verbose(env, "BPF_NEG uses reserved fields\n");
                                return -EINVAL;
                        }
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0 ||
                            (insn->imm != 16 && insn->imm != 32 && insn->imm != 64) ||
                            BPF_CLASS(insn->code) == BPF_ALU64) {
                                verbose(env, "BPF_END uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check src operand */
                err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                if (err)
                        return err;

                if (is_pointer_value(env, insn->dst_reg)) {
                        verbose(env, "R%d pointer arithmetic prohibited\n",
                                insn->dst_reg);
                        return -EACCES;
                }

                /* check dest operand */
                err = check_reg_arg(env, insn->dst_reg, DST_OP);
                if (err)
                        return err;

        } else if (opcode == BPF_MOV) {

                if (BPF_SRC(insn->code) == BPF_X) {
                        if (insn->imm != 0 || insn->off != 0) {
                                verbose(env, "BPF_MOV uses reserved fields\n");
                                return -EINVAL;
                        }

                        /* check src operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
                                verbose(env, "BPF_MOV uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check dest operand, mark as required later */
                err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
                if (err)
                        return err;

                if (BPF_SRC(insn->code) == BPF_X) {
                        struct bpf_reg_state *src_reg = regs + insn->src_reg;
                        struct bpf_reg_state *dst_reg = regs + insn->dst_reg;

                        if (BPF_CLASS(insn->code) == BPF_ALU64) {
                                /* case: R1 = R2
                                 * copy register state to dest reg
                                 */
                                if (src_reg->type == SCALAR_VALUE && !src_reg->id)
                                        /* Assign src and dst registers the same ID
                                         * that will be used by find_equal_scalars()
                                         * to propagate min/max range.
                                         */
                                        src_reg->id = ++env->id_gen;
                                *dst_reg = *src_reg;
                                dst_reg->live |= REG_LIVE_WRITTEN;
                                dst_reg->subreg_def = DEF_NOT_SUBREG;
                        } else {
                                /* R1 = (u32) R2 */
                                if (is_pointer_value(env, insn->src_reg)) {
                                        verbose(env,
                                                "R%d partial copy of pointer\n",
                                                insn->src_reg);
                                        return -EACCES;
                                } else if (src_reg->type == SCALAR_VALUE) {
                                        *dst_reg = *src_reg;
                                        /* Make sure ID is cleared otherwise
                                         * dst_reg min/max could be incorrectly
                                         * propagated into src_reg by find_equal_scalars()
                                         */
                                        dst_reg->id = 0;
                                        dst_reg->live |= REG_LIVE_WRITTEN;
                                        dst_reg->subreg_def = env->insn_idx + 1;
                                } else {
                                        mark_reg_unknown(env, regs,
                                                         insn->dst_reg);
                                }
                                zext_32_to_64(dst_reg);
                        }
                } else {
                        /* case: R = imm
                         * remember the value we stored into this reg
                         */
                        /* clear any state __mark_reg_known doesn't set */
                        mark_reg_unknown(env, regs, insn->dst_reg);
                        regs[insn->dst_reg].type = SCALAR_VALUE;
                        if (BPF_CLASS(insn->code) == BPF_ALU64) {
                                __mark_reg_known(regs + insn->dst_reg,
                                                 insn->imm);
                        } else {
                                __mark_reg_known(regs + insn->dst_reg,
                                                 (u32)insn->imm);
                        }
                }

        } else if (opcode > BPF_END) {
                verbose(env, "invalid BPF_ALU opcode %x\n", opcode);
                return -EINVAL;

        } else {        /* all other ALU ops: and, sub, xor, add, ... */

                if (BPF_SRC(insn->code) == BPF_X) {
                        if (insn->imm != 0 || insn->off != 0) {
                                verbose(env, "BPF_ALU uses reserved fields\n");
                                return -EINVAL;
                        }
                        /* check src1 operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                } else {
                        if (insn->src_reg != BPF_REG_0 || insn->off != 0) {
                                verbose(env, "BPF_ALU uses reserved fields\n");
                                return -EINVAL;
                        }
                }

                /* check src2 operand */
                err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                if (err)
                        return err;

                if ((opcode == BPF_MOD || opcode == BPF_DIV) &&
                    BPF_SRC(insn->code) == BPF_K && insn->imm == 0) {
                        verbose(env, "div by zero\n");
                        return -EINVAL;
                }

                if ((opcode == BPF_LSH || opcode == BPF_RSH ||
                     opcode == BPF_ARSH) && BPF_SRC(insn->code) == BPF_K) {
                        int size = BPF_CLASS(insn->code) == BPF_ALU64 ? 64 : 32;

                        if (insn->imm < 0 || insn->imm >= size) {
                                verbose(env, "invalid shift %d\n", insn->imm);
                                return -EINVAL;
                        }
                }

                /* check dest operand */
                err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
                if (err)
                        return err;

                return adjust_reg_min_max_vals(env, insn);
        }

        return 0;
}

static void __find_good_pkt_pointers(struct bpf_func_state *state,
                                     struct bpf_reg_state *dst_reg,
                                     enum bpf_reg_type type, int new_range)
{
        struct bpf_reg_state *reg;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++) {
                reg = &state->regs[i];
                if (reg->type == type && reg->id == dst_reg->id)
                        /* keep the maximum range already checked */
                        reg->range = max(reg->range, new_range);
        }

        bpf_for_each_spilled_reg(i, state, reg) {
                if (!reg)
                        continue;
                if (reg->type == type && reg->id == dst_reg->id)
                        reg->range = max(reg->range, new_range);
        }
}

static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
                                   struct bpf_reg_state *dst_reg,
                                   enum bpf_reg_type type,
                                   bool range_right_open)
{
        int new_range, i;

        if (dst_reg->off < 0 ||
            (dst_reg->off == 0 && range_right_open))
                /* This doesn't give us any range */
                return;

        if (dst_reg->umax_value > MAX_PACKET_OFF ||
            dst_reg->umax_value + dst_reg->off > MAX_PACKET_OFF)
                /* Risk of overflow.  For instance, ptr + (1<<63) may be less
                 * than pkt_end, but that's because it's also less than pkt.
                 */
                return;

        new_range = dst_reg->off;
        if (range_right_open)
                new_range--;

        /* Examples for register markings:
         *
         * pkt_data in dst register:
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (r2 > pkt_end) goto <handle exception>
         *   <access okay>
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (r2 < pkt_end) goto <access okay>
         *   <handle exception>
         *
         *   Where:
         *     r2 == dst_reg, pkt_end == src_reg
         *     r2=pkt(id=n,off=8,r=0)
         *     r3=pkt(id=n,off=0,r=0)
         *
         * pkt_data in src register:
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (pkt_end >= r2) goto <access okay>
         *   <handle exception>
         *
         *   r2 = r3;
         *   r2 += 8;
         *   if (pkt_end <= r2) goto <handle exception>
         *   <access okay>
         *
         *   Where:
         *     pkt_end == dst_reg, r2 == src_reg
         *     r2=pkt(id=n,off=8,r=0)
         *     r3=pkt(id=n,off=0,r=0)
         *
         * Find register r3 and mark its range as r3=pkt(id=n,off=0,r=8)
         * or r3=pkt(id=n,off=0,r=8-1), so that range of bytes [r3, r3 + 8)
         * and [r3, r3 + 8-1) respectively is safe to access depending on
         * the check.
         */

        /* If our ids match, then we must have the same max_value.  And we
         * don't care about the other reg's fixed offset, since if it's too big
         * the range won't allow anything.
         * dst_reg->off is known < MAX_PACKET_OFF, therefore it fits in a u16.
         */
        for (i = 0; i <= vstate->curframe; i++)
                __find_good_pkt_pointers(vstate->frame[i], dst_reg, type,
                                         new_range);
}

static int is_branch32_taken(struct bpf_reg_state *reg, u32 val, u8 opcode)
{
        struct tnum subreg = tnum_subreg(reg->var_off);
        s32 sval = (s32)val;

        switch (opcode) {
        case BPF_JEQ:
                if (tnum_is_const(subreg))
                        return !!tnum_equals_const(subreg, val);
                break;
        case BPF_JNE:
                if (tnum_is_const(subreg))
                        return !tnum_equals_const(subreg, val);
                break;
        case BPF_JSET:
                if ((~subreg.mask & subreg.value) & val)
                        return 1;
                if (!((subreg.mask | subreg.value) & val))
                        return 0;
                break;
        case BPF_JGT:
                if (reg->u32_min_value > val)
                        return 1;
                else if (reg->u32_max_value <= val)
                        return 0;
                break;
        case BPF_JSGT:
                if (reg->s32_min_value > sval)
                        return 1;
                else if (reg->s32_max_value <= sval)
                        return 0;
                break;
        case BPF_JLT:
                if (reg->u32_max_value < val)
                        return 1;
                else if (reg->u32_min_value >= val)
                        return 0;
                break;
        case BPF_JSLT:
                if (reg->s32_max_value < sval)
                        return 1;
                else if (reg->s32_min_value >= sval)
                        return 0;
                break;
        case BPF_JGE:
                if (reg->u32_min_value >= val)
                        return 1;
                else if (reg->u32_max_value < val)
                        return 0;
                break;
        case BPF_JSGE:
                if (reg->s32_min_value >= sval)
                        return 1;
                else if (reg->s32_max_value < sval)
                        return 0;
                break;
        case BPF_JLE:
                if (reg->u32_max_value <= val)
                        return 1;
                else if (reg->u32_min_value > val)
                        return 0;
                break;
        case BPF_JSLE:
                if (reg->s32_max_value <= sval)
                        return 1;
                else if (reg->s32_min_value > sval)
                        return 0;
                break;
        }

        return -1;
}


static int is_branch64_taken(struct bpf_reg_state *reg, u64 val, u8 opcode)
{
        s64 sval = (s64)val;

        switch (opcode) {
        case BPF_JEQ:
                if (tnum_is_const(reg->var_off))
                        return !!tnum_equals_const(reg->var_off, val);
                break;
        case BPF_JNE:
                if (tnum_is_const(reg->var_off))
                        return !tnum_equals_const(reg->var_off, val);
                break;
        case BPF_JSET:
                if ((~reg->var_off.mask & reg->var_off.value) & val)
                        return 1;
                if (!((reg->var_off.mask | reg->var_off.value) & val))
                        return 0;
                break;
        case BPF_JGT:
                if (reg->umin_value > val)
                        return 1;
                else if (reg->umax_value <= val)
                        return 0;
                break;
        case BPF_JSGT:
                if (reg->smin_value > sval)
                        return 1;
                else if (reg->smax_value <= sval)
                        return 0;
                break;
        case BPF_JLT:
                if (reg->umax_value < val)
                        return 1;
                else if (reg->umin_value >= val)
                        return 0;
                break;
        case BPF_JSLT:
                if (reg->smax_value < sval)
                        return 1;
                else if (reg->smin_value >= sval)
                        return 0;
                break;
        case BPF_JGE:
                if (reg->umin_value >= val)
                        return 1;
                else if (reg->umax_value < val)
                        return 0;
                break;
        case BPF_JSGE:
                if (reg->smin_value >= sval)
                        return 1;
                else if (reg->smax_value < sval)
                        return 0;
                break;
        case BPF_JLE:
                if (reg->umax_value <= val)
                        return 1;
                else if (reg->umin_value > val)
                        return 0;
                break;
        case BPF_JSLE:
                if (reg->smax_value <= sval)
                        return 1;
                else if (reg->smin_value > sval)
                        return 0;
                break;
        }

        return -1;
}

/* compute branch direction of the expression "if (reg opcode val) goto target;"
 * and return:
 *  1 - branch will be taken and "goto target" will be executed
 *  0 - branch will not be taken and fall-through to next insn
 * -1 - unknown. Example: "if (reg < 5)" is unknown when register value
 *      range [0,10]
 */
static int is_branch_taken(struct bpf_reg_state *reg, u64 val, u8 opcode,
                           bool is_jmp32)
{
        if (__is_pointer_value(false, reg)) {
                if (!reg_type_not_null(reg->type))
                        return -1;

                /* If pointer is valid tests against zero will fail so we can
                 * use this to direct branch taken.
                 */
                if (val != 0)
                        return -1;

                switch (opcode) {
                case BPF_JEQ:
                        return 0;
                case BPF_JNE:
                        return 1;
                default:
                        return -1;
                }
        }

        if (is_jmp32)
                return is_branch32_taken(reg, val, opcode);
        return is_branch64_taken(reg, val, opcode);
}

static int flip_opcode(u32 opcode)
{
        /* How can we transform "a <op> b" into "b <op> a"? */
        static const u8 opcode_flip[16] = {
                /* these stay the same */
                [BPF_JEQ  >> 4] = BPF_JEQ,
                [BPF_JNE  >> 4] = BPF_JNE,
                [BPF_JSET >> 4] = BPF_JSET,
                /* these swap "lesser" and "greater" (L and G in the opcodes) */
                [BPF_JGE  >> 4] = BPF_JLE,
                [BPF_JGT  >> 4] = BPF_JLT,
                [BPF_JLE  >> 4] = BPF_JGE,
                [BPF_JLT  >> 4] = BPF_JGT,
                [BPF_JSGE >> 4] = BPF_JSLE,
                [BPF_JSGT >> 4] = BPF_JSLT,
                [BPF_JSLE >> 4] = BPF_JSGE,
                [BPF_JSLT >> 4] = BPF_JSGT
        };
        return opcode_flip[opcode >> 4];
}

static int is_pkt_ptr_branch_taken(struct bpf_reg_state *dst_reg,
                                   struct bpf_reg_state *src_reg,
                                   u8 opcode)
{
        struct bpf_reg_state *pkt;

        if (src_reg->type == PTR_TO_PACKET_END) {
                pkt = dst_reg;
        } else if (dst_reg->type == PTR_TO_PACKET_END) {
                pkt = src_reg;
                opcode = flip_opcode(opcode);
        } else {
                return -1;
        }

        if (pkt->range >= 0)
                return -1;

        switch (opcode) {
        case BPF_JLE:
                /* pkt <= pkt_end */
                fallthrough;
        case BPF_JGT:
                /* pkt > pkt_end */
                if (pkt->range == BEYOND_PKT_END)
                        /* pkt has at last one extra byte beyond pkt_end */
                        return opcode == BPF_JGT;
                break;
        case BPF_JLT:
                /* pkt < pkt_end */
                fallthrough;
        case BPF_JGE:
                /* pkt >= pkt_end */
                if (pkt->range == BEYOND_PKT_END || pkt->range == AT_PKT_END)
                        return opcode == BPF_JGE;
                break;
        }
        return -1;
}

/* Adjusts the register min/max values in the case that the dst_reg is the
 * variable register that we are working on, and src_reg is a constant or we're
 * simply doing a BPF_K check.
 * In JEQ/JNE cases we also adjust the var_off values.
 */
static void reg_set_min_max(struct bpf_reg_state *true_reg,
                            struct bpf_reg_state *false_reg,
                            u64 val, u32 val32,
                            u8 opcode, bool is_jmp32)
{
        struct tnum false_32off = tnum_subreg(false_reg->var_off);
        struct tnum false_64off = false_reg->var_off;
        struct tnum true_32off = tnum_subreg(true_reg->var_off);
        struct tnum true_64off = true_reg->var_off;
        s64 sval = (s64)val;
        s32 sval32 = (s32)val32;

        /* If the dst_reg is a pointer, we can't learn anything about its
         * variable offset from the compare (unless src_reg were a pointer into
         * the same object, but we don't bother with that.
         * Since false_reg and true_reg have the same type by construction, we
         * only need to check one of them for pointerness.
         */
        if (__is_pointer_value(false, false_reg))
                return;

        switch (opcode) {
        case BPF_JEQ:
        case BPF_JNE:
        {
                struct bpf_reg_state *reg =
                        opcode == BPF_JEQ ? true_reg : false_reg;

                /* JEQ/JNE comparison doesn't change the register equivalence.
                 * r1 = r2;
                 * if (r1 == 42) goto label;
                 * ...
                 * label: // here both r1 and r2 are known to be 42.
                 *
                 * Hence when marking register as known preserve it's ID.
                 */
                if (is_jmp32)
                        __mark_reg32_known(reg, val32);
                else
                        ___mark_reg_known(reg, val);
                break;
        }
        case BPF_JSET:
                if (is_jmp32) {
                        false_32off = tnum_and(false_32off, tnum_const(~val32));
                        if (is_power_of_2(val32))
                                true_32off = tnum_or(true_32off,
                                                     tnum_const(val32));
                } else {
                        false_64off = tnum_and(false_64off, tnum_const(~val));
                        if (is_power_of_2(val))
                                true_64off = tnum_or(true_64off,
                                                     tnum_const(val));
                }
                break;
        case BPF_JGE:
        case BPF_JGT:
        {
                if (is_jmp32) {
                        u32 false_umax = opcode == BPF_JGT ? val32  : val32 - 1;
                        u32 true_umin = opcode == BPF_JGT ? val32 + 1 : val32;

                        false_reg->u32_max_value = min(false_reg->u32_max_value,
                                                       false_umax);
                        true_reg->u32_min_value = max(true_reg->u32_min_value,
                                                      true_umin);
                } else {
                        u64 false_umax = opcode == BPF_JGT ? val    : val - 1;
                        u64 true_umin = opcode == BPF_JGT ? val + 1 : val;

                        false_reg->umax_value = min(false_reg->umax_value, false_umax);
                        true_reg->umin_value = max(true_reg->umin_value, true_umin);
                }
                break;
        }
        case BPF_JSGE:
        case BPF_JSGT:
        {
                if (is_jmp32) {
                        s32 false_smax = opcode == BPF_JSGT ? sval32    : sval32 - 1;
                        s32 true_smin = opcode == BPF_JSGT ? sval32 + 1 : sval32;

                        false_reg->s32_max_value = min(false_reg->s32_max_value, false_smax);
                        true_reg->s32_min_value = max(true_reg->s32_min_value, true_smin);
                } else {
                        s64 false_smax = opcode == BPF_JSGT ? sval    : sval - 1;
                        s64 true_smin = opcode == BPF_JSGT ? sval + 1 : sval;

                        false_reg->smax_value = min(false_reg->smax_value, false_smax);
                        true_reg->smin_value = max(true_reg->smin_value, true_smin);
                }
                break;
        }
        case BPF_JLE:
        case BPF_JLT:
        {
                if (is_jmp32) {
                        u32 false_umin = opcode == BPF_JLT ? val32  : val32 + 1;
                        u32 true_umax = opcode == BPF_JLT ? val32 - 1 : val32;

                        false_reg->u32_min_value = max(false_reg->u32_min_value,
                                                       false_umin);
                        true_reg->u32_max_value = min(true_reg->u32_max_value,
                                                      true_umax);
                } else {
                        u64 false_umin = opcode == BPF_JLT ? val    : val + 1;
                        u64 true_umax = opcode == BPF_JLT ? val - 1 : val;

                        false_reg->umin_value = max(false_reg->umin_value, false_umin);
                        true_reg->umax_value = min(true_reg->umax_value, true_umax);
                }
                break;
        }
        case BPF_JSLE:
        case BPF_JSLT:
        {
                if (is_jmp32) {
                        s32 false_smin = opcode == BPF_JSLT ? sval32    : sval32 + 1;
                        s32 true_smax = opcode == BPF_JSLT ? sval32 - 1 : sval32;

                        false_reg->s32_min_value = max(false_reg->s32_min_value, false_smin);
                        true_reg->s32_max_value = min(true_reg->s32_max_value, true_smax);
                } else {
                        s64 false_smin = opcode == BPF_JSLT ? sval    : sval + 1;
                        s64 true_smax = opcode == BPF_JSLT ? sval - 1 : sval;

                        false_reg->smin_value = max(false_reg->smin_value, false_smin);
                        true_reg->smax_value = min(true_reg->smax_value, true_smax);
                }
                break;
        }
        default:
                return;
        }

        if (is_jmp32) {
                false_reg->var_off = tnum_or(tnum_clear_subreg(false_64off),
                                             tnum_subreg(false_32off));
                true_reg->var_off = tnum_or(tnum_clear_subreg(true_64off),
                                            tnum_subreg(true_32off));
                __reg_combine_32_into_64(false_reg);
                __reg_combine_32_into_64(true_reg);
        } else {
                false_reg->var_off = false_64off;
                true_reg->var_off = true_64off;
                __reg_combine_64_into_32(false_reg);
                __reg_combine_64_into_32(true_reg);
        }
}

/* Same as above, but for the case that dst_reg holds a constant and src_reg is
 * the variable reg.
 */
static void reg_set_min_max_inv(struct bpf_reg_state *true_reg,
                                struct bpf_reg_state *false_reg,
                                u64 val, u32 val32,
                                u8 opcode, bool is_jmp32)
{
        opcode = flip_opcode(opcode);
        /* This uses zero as "not present in table"; luckily the zero opcode,
         * BPF_JA, can't get here.
         */
        if (opcode)
                reg_set_min_max(true_reg, false_reg, val, val32, opcode, is_jmp32);
}

/* Regs are known to be equal, so intersect their min/max/var_off */
static void __reg_combine_min_max(struct bpf_reg_state *src_reg,
                                  struct bpf_reg_state *dst_reg)
{
        src_reg->umin_value = dst_reg->umin_value = max(src_reg->umin_value,
                                                        dst_reg->umin_value);
        src_reg->umax_value = dst_reg->umax_value = min(src_reg->umax_value,
                                                        dst_reg->umax_value);
        src_reg->smin_value = dst_reg->smin_value = max(src_reg->smin_value,
                                                        dst_reg->smin_value);
        src_reg->smax_value = dst_reg->smax_value = min(src_reg->smax_value,
                                                        dst_reg->smax_value);
        src_reg->var_off = dst_reg->var_off = tnum_intersect(src_reg->var_off,
                                                             dst_reg->var_off);
        /* We might have learned new bounds from the var_off. */
        __update_reg_bounds(src_reg);
        __update_reg_bounds(dst_reg);
        /* We might have learned something about the sign bit. */
        __reg_deduce_bounds(src_reg);
        __reg_deduce_bounds(dst_reg);
        /* We might have learned some bits from the bounds. */
        __reg_bound_offset(src_reg);
        __reg_bound_offset(dst_reg);
        /* Intersecting with the old var_off might have improved our bounds
         * slightly.  e.g. if umax was 0x7f...f and var_off was (0; 0xf...fc),
         * then new var_off is (0; 0x7f...fc) which improves our umax.
         */
        __update_reg_bounds(src_reg);
        __update_reg_bounds(dst_reg);
}

static void reg_combine_min_max(struct bpf_reg_state *true_src,
                                struct bpf_reg_state *true_dst,
                                struct bpf_reg_state *false_src,
                                struct bpf_reg_state *false_dst,
                                u8 opcode)
{
        switch (opcode) {
        case BPF_JEQ:
                __reg_combine_min_max(true_src, true_dst);
                break;
        case BPF_JNE:
                __reg_combine_min_max(false_src, false_dst);
                break;
        }
}

static void mark_ptr_or_null_reg(struct bpf_func_state *state,
                                 struct bpf_reg_state *reg, u32 id,
                                 bool is_null)
{
        if (reg_type_may_be_null(reg->type) && reg->id == id &&
            !WARN_ON_ONCE(!reg->id)) {
                /* Old offset (both fixed and variable parts) should
                 * have been known-zero, because we don't allow pointer
                 * arithmetic on pointers that might be NULL.
                 */
                if (WARN_ON_ONCE(reg->smin_value || reg->smax_value ||
                                 !tnum_equals_const(reg->var_off, 0) ||
                                 reg->off)) {
                        __mark_reg_known_zero(reg);
                        reg->off = 0;
                }
                if (is_null) {
                        reg->type = SCALAR_VALUE;
                        /* We don't need id and ref_obj_id from this point
                         * onwards anymore, thus we should better reset it,
                         * so that state pruning has chances to take effect.
                         */
                        reg->id = 0;
                        reg->ref_obj_id = 0;

                        return;
                }

                mark_ptr_not_null_reg(reg);

                if (!reg_may_point_to_spin_lock(reg)) {
                        /* For not-NULL ptr, reg->ref_obj_id will be reset
                         * in release_reg_references().
                         *
                         * reg->id is still used by spin_lock ptr. Other
                         * than spin_lock ptr type, reg->id can be reset.
                         */
                        reg->id = 0;
                }
        }
}

static void __mark_ptr_or_null_regs(struct bpf_func_state *state, u32 id,
                                    bool is_null)
{
        struct bpf_reg_state *reg;
        int i;

        for (i = 0; i < MAX_BPF_REG; i++)
                mark_ptr_or_null_reg(state, &state->regs[i], id, is_null);

        bpf_for_each_spilled_reg(i, state, reg) {
                if (!reg)
                        continue;
                mark_ptr_or_null_reg(state, reg, id, is_null);
        }
}

/* The logic is similar to find_good_pkt_pointers(), both could eventually
 * be folded together at some point.
 */
static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
                                  bool is_null)
{
        struct bpf_func_state *state = vstate->frame[vstate->curframe];
        struct bpf_reg_state *regs = state->regs;
        u32 ref_obj_id = regs[regno].ref_obj_id;
        u32 id = regs[regno].id;
        int i;

        if (ref_obj_id && ref_obj_id == id && is_null)
                /* regs[regno] is in the " == NULL" branch.
                 * No one could have freed the reference state before
                 * doing the NULL check.
                 */
                WARN_ON_ONCE(release_reference_state(state, id));

        for (i = 0; i <= vstate->curframe; i++)
                __mark_ptr_or_null_regs(vstate->frame[i], id, is_null);
}

static bool try_match_pkt_pointers(const struct bpf_insn *insn,
                                   struct bpf_reg_state *dst_reg,
                                   struct bpf_reg_state *src_reg,
                                   struct bpf_verifier_state *this_branch,
                                   struct bpf_verifier_state *other_branch)
{
        if (BPF_SRC(insn->code) != BPF_X)
                return false;

        /* Pointers are always 64-bit. */
        if (BPF_CLASS(insn->code) == BPF_JMP32)
                return false;

        switch (BPF_OP(insn->code)) {
        case BPF_JGT:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' > pkt_end, pkt_meta' > pkt_data */
                        find_good_pkt_pointers(this_branch, dst_reg,
                                               dst_reg->type, false);
                        mark_pkt_end(other_branch, insn->dst_reg, true);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end > pkt_data', pkt_data > pkt_meta' */
                        find_good_pkt_pointers(other_branch, src_reg,
                                               src_reg->type, true);
                        mark_pkt_end(this_branch, insn->src_reg, false);
                } else {
                        return false;
                }
                break;
        case BPF_JLT:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' < pkt_end, pkt_meta' < pkt_data */
                        find_good_pkt_pointers(other_branch, dst_reg,
                                               dst_reg->type, true);
                        mark_pkt_end(this_branch, insn->dst_reg, false);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end < pkt_data', pkt_data > pkt_meta' */
                        find_good_pkt_pointers(this_branch, src_reg,
                                               src_reg->type, false);
                        mark_pkt_end(other_branch, insn->src_reg, true);
                } else {
                        return false;
                }
                break;
        case BPF_JGE:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' >= pkt_end, pkt_meta' >= pkt_data */
                        find_good_pkt_pointers(this_branch, dst_reg,
                                               dst_reg->type, true);
                        mark_pkt_end(other_branch, insn->dst_reg, false);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end >= pkt_data', pkt_data >= pkt_meta' */
                        find_good_pkt_pointers(other_branch, src_reg,
                                               src_reg->type, false);
                        mark_pkt_end(this_branch, insn->src_reg, true);
                } else {
                        return false;
                }
                break;
        case BPF_JLE:
                if ((dst_reg->type == PTR_TO_PACKET &&
                     src_reg->type == PTR_TO_PACKET_END) ||
                    (dst_reg->type == PTR_TO_PACKET_META &&
                     reg_is_init_pkt_pointer(src_reg, PTR_TO_PACKET))) {
                        /* pkt_data' <= pkt_end, pkt_meta' <= pkt_data */
                        find_good_pkt_pointers(other_branch, dst_reg,
                                               dst_reg->type, false);
                        mark_pkt_end(this_branch, insn->dst_reg, true);
                } else if ((dst_reg->type == PTR_TO_PACKET_END &&
                            src_reg->type == PTR_TO_PACKET) ||
                           (reg_is_init_pkt_pointer(dst_reg, PTR_TO_PACKET) &&
                            src_reg->type == PTR_TO_PACKET_META)) {
                        /* pkt_end <= pkt_data', pkt_data <= pkt_meta' */
                        find_good_pkt_pointers(this_branch, src_reg,
                                               src_reg->type, true);
                        mark_pkt_end(other_branch, insn->src_reg, false);
                } else {
                        return false;
                }
                break;
        default:
                return false;
        }

        return true;
}

static void find_equal_scalars(struct bpf_verifier_state *vstate,
                               struct bpf_reg_state *known_reg)
{
        struct bpf_func_state *state;
        struct bpf_reg_state *reg;
        int i, j;

        for (i = 0; i <= vstate->curframe; i++) {
                state = vstate->frame[i];
                for (j = 0; j < MAX_BPF_REG; j++) {
                        reg = &state->regs[j];
                        if (reg->type == SCALAR_VALUE && reg->id == known_reg->id)
                                *reg = *known_reg;
                }

                bpf_for_each_spilled_reg(j, state, reg) {
                        if (!reg)
                                continue;
                        if (reg->type == SCALAR_VALUE && reg->id == known_reg->id)
                                *reg = *known_reg;
                }
        }
}

static int check_cond_jmp_op(struct bpf_verifier_env *env,
                             struct bpf_insn *insn, int *insn_idx)
{
        struct bpf_verifier_state *this_branch = env->cur_state;
        struct bpf_verifier_state *other_branch;
        struct bpf_reg_state *regs = this_branch->frame[this_branch->curframe]->regs;
        struct bpf_reg_state *dst_reg, *other_branch_regs, *src_reg = NULL;
        u8 opcode = BPF_OP(insn->code);
        bool is_jmp32;
        int pred = -1;
        int err;

        /* Only conditional jumps are expected to reach here. */
        if (opcode == BPF_JA || opcode > BPF_JSLE) {
                verbose(env, "invalid BPF_JMP/JMP32 opcode %x\n", opcode);
                return -EINVAL;
        }

        if (BPF_SRC(insn->code) == BPF_X) {
                if (insn->imm != 0) {
                        verbose(env, "BPF_JMP/JMP32 uses reserved fields\n");
                        return -EINVAL;
                }

                /* check src1 operand */
                err = check_reg_arg(env, insn->src_reg, SRC_OP);
                if (err)
                        return err;

                if (is_pointer_value(env, insn->src_reg)) {
                        verbose(env, "R%d pointer comparison prohibited\n",
                                insn->src_reg);
                        return -EACCES;
                }
                src_reg = &regs[insn->src_reg];
        } else {
                if (insn->src_reg != BPF_REG_0) {
                        verbose(env, "BPF_JMP/JMP32 uses reserved fields\n");
                        return -EINVAL;
                }
        }

        /* check src2 operand */
        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
        if (err)
                return err;

        dst_reg = &regs[insn->dst_reg];
        is_jmp32 = BPF_CLASS(insn->code) == BPF_JMP32;

        if (BPF_SRC(insn->code) == BPF_K) {
                pred = is_branch_taken(dst_reg, insn->imm, opcode, is_jmp32);
        } else if (src_reg->type == SCALAR_VALUE &&
                   is_jmp32 && tnum_is_const(tnum_subreg(src_reg->var_off))) {
                pred = is_branch_taken(dst_reg,
                                       tnum_subreg(src_reg->var_off).value,
                                       opcode,
                                       is_jmp32);
        } else if (src_reg->type == SCALAR_VALUE &&
                   !is_jmp32 && tnum_is_const(src_reg->var_off)) {
                pred = is_branch_taken(dst_reg,
                                       src_reg->var_off.value,
                                       opcode,
                                       is_jmp32);
        } else if (reg_is_pkt_pointer_any(dst_reg) &&
                   reg_is_pkt_pointer_any(src_reg) &&
                   !is_jmp32) {
                pred = is_pkt_ptr_branch_taken(dst_reg, src_reg, opcode);
        }

        if (pred >= 0) {
                /* If we get here with a dst_reg pointer type it is because
                 * above is_branch_taken() special cased the 0 comparison.
                 */
                if (!__is_pointer_value(false, dst_reg))
                        err = mark_chain_precision(env, insn->dst_reg);
                if (BPF_SRC(insn->code) == BPF_X && !err &&
                    !__is_pointer_value(false, src_reg))
                        err = mark_chain_precision(env, insn->src_reg);
                if (err)
                        return err;
        }
        if (pred == 1) {
                /* only follow the goto, ignore fall-through */
                *insn_idx += insn->off;
                return 0;
        } else if (pred == 0) {
                /* only follow fall-through branch, since
                 * that's where the program will go
                 */
                return 0;
        }

        other_branch = push_stack(env, *insn_idx + insn->off + 1, *insn_idx,
                                  false);
        if (!other_branch)
                return -EFAULT;
        other_branch_regs = other_branch->frame[other_branch->curframe]->regs;

        /* detect if we are comparing against a constant value so we can adjust
         * our min/max values for our dst register.
         * this is only legit if both are scalars (or pointers to the same
         * object, I suppose, but we don't support that right now), because
         * otherwise the different base pointers mean the offsets aren't
         * comparable.
         */
        if (BPF_SRC(insn->code) == BPF_X) {
                struct bpf_reg_state *src_reg = &regs[insn->src_reg];

                if (dst_reg->type == SCALAR_VALUE &&
                    src_reg->type == SCALAR_VALUE) {
                        if (tnum_is_const(src_reg->var_off) ||
                            (is_jmp32 &&
                             tnum_is_const(tnum_subreg(src_reg->var_off))))
                                reg_set_min_max(&other_branch_regs[insn->dst_reg],
                                                dst_reg,
                                                src_reg->var_off.value,
                                                tnum_subreg(src_reg->var_off).value,
                                                opcode, is_jmp32);
                        else if (tnum_is_const(dst_reg->var_off) ||
                                 (is_jmp32 &&
                                  tnum_is_const(tnum_subreg(dst_reg->var_off))))
                                reg_set_min_max_inv(&other_branch_regs[insn->src_reg],
                                                    src_reg,
                                                    dst_reg->var_off.value,
                                                    tnum_subreg(dst_reg->var_off).value,
                                                    opcode, is_jmp32);
                        else if (!is_jmp32 &&
                                 (opcode == BPF_JEQ || opcode == BPF_JNE))
                                /* Comparing for equality, we can combine knowledge */
                                reg_combine_min_max(&other_branch_regs[insn->src_reg],
                                                    &other_branch_regs[insn->dst_reg],
                                                    src_reg, dst_reg, opcode);
                        if (src_reg->id &&
                            !WARN_ON_ONCE(src_reg->id != other_branch_regs[insn->src_reg].id)) {
                                find_equal_scalars(this_branch, src_reg);
                                find_equal_scalars(other_branch, &other_branch_regs[insn->src_reg]);
                        }

                }
        } else if (dst_reg->type == SCALAR_VALUE) {
                reg_set_min_max(&other_branch_regs[insn->dst_reg],
                                        dst_reg, insn->imm, (u32)insn->imm,
                                        opcode, is_jmp32);
        }

        if (dst_reg->type == SCALAR_VALUE && dst_reg->id &&
            !WARN_ON_ONCE(dst_reg->id != other_branch_regs[insn->dst_reg].id)) {
                find_equal_scalars(this_branch, dst_reg);
                find_equal_scalars(other_branch, &other_branch_regs[insn->dst_reg]);
        }

        /* detect if R == 0 where R is returned from bpf_map_lookup_elem().
         * NOTE: these optimizations below are related with pointer comparison
         *       which will never be JMP32.
         */
        if (!is_jmp32 && BPF_SRC(insn->code) == BPF_K &&
            insn->imm == 0 && (opcode == BPF_JEQ || opcode == BPF_JNE) &&
            reg_type_may_be_null(dst_reg->type)) {
                /* Mark all identical registers in each branch as either
                 * safe or unknown depending R == 0 or R != 0 conditional.
                 */
                mark_ptr_or_null_regs(this_branch, insn->dst_reg,
                                      opcode == BPF_JNE);
                mark_ptr_or_null_regs(other_branch, insn->dst_reg,
                                      opcode == BPF_JEQ);
        } else if (!try_match_pkt_pointers(insn, dst_reg, &regs[insn->src_reg],
                                           this_branch, other_branch) &&
                   is_pointer_value(env, insn->dst_reg)) {
                verbose(env, "R%d pointer comparison prohibited\n",
                        insn->dst_reg);
                return -EACCES;
        }
        if (env->log.level & BPF_LOG_LEVEL)
                print_verifier_state(env, this_branch->frame[this_branch->curframe]);
        return 0;
}

/* verify BPF_LD_IMM64 instruction */
static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_insn_aux_data *aux = cur_aux(env);
        struct bpf_reg_state *regs = cur_regs(env);
        struct bpf_reg_state *dst_reg;
        struct bpf_map *map;
        int err;

        if (BPF_SIZE(insn->code) != BPF_DW) {
                verbose(env, "invalid BPF_LD_IMM insn\n");
                return -EINVAL;
        }
        if (insn->off != 0) {
                verbose(env, "BPF_LD_IMM64 uses reserved fields\n");
                return -EINVAL;
        }

        err = check_reg_arg(env, insn->dst_reg, DST_OP);
        if (err)
                return err;

        dst_reg = &regs[insn->dst_reg];
        if (insn->src_reg == 0) {
                u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;

                dst_reg->type = SCALAR_VALUE;
                __mark_reg_known(&regs[insn->dst_reg], imm);
                return 0;
        }

        if (insn->src_reg == BPF_PSEUDO_BTF_ID) {
                mark_reg_known_zero(env, regs, insn->dst_reg);

                dst_reg->type = aux->btf_var.reg_type;
                switch (dst_reg->type) {
                case PTR_TO_MEM:
                        dst_reg->mem_size = aux->btf_var.mem_size;
                        break;
                case PTR_TO_BTF_ID:
                case PTR_TO_PERCPU_BTF_ID:
                        dst_reg->btf = aux->btf_var.btf;
                        dst_reg->btf_id = aux->btf_var.btf_id;
                        break;
                default:
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EFAULT;
                }
                return 0;
        }

        if (insn->src_reg == BPF_PSEUDO_FUNC) {
                struct bpf_prog_aux *aux = env->prog->aux;
                u32 subprogno = insn[1].imm;

                if (!aux->func_info) {
                        verbose(env, "missing btf func_info\n");
                        return -EINVAL;
                }
                if (aux->func_info_aux[subprogno].linkage != BTF_FUNC_STATIC) {
                        verbose(env, "callback function not static\n");
                        return -EINVAL;
                }

                dst_reg->type = PTR_TO_FUNC;
                dst_reg->subprogno = subprogno;
                return 0;
        }

        map = env->used_maps[aux->map_index];
        mark_reg_known_zero(env, regs, insn->dst_reg);
        dst_reg->map_ptr = map;

        if (insn->src_reg == BPF_PSEUDO_MAP_VALUE) {
                dst_reg->type = PTR_TO_MAP_VALUE;
                dst_reg->off = aux->map_off;
                if (map_value_has_spin_lock(map))
                        dst_reg->id = ++env->id_gen;
        } else if (insn->src_reg == BPF_PSEUDO_MAP_FD) {
                dst_reg->type = CONST_PTR_TO_MAP;
        } else {
                verbose(env, "bpf verifier is misconfigured\n");
                return -EINVAL;
        }

        return 0;
}

static bool may_access_skb(enum bpf_prog_type type)
{
        switch (type) {
        case BPF_PROG_TYPE_SOCKET_FILTER:
        case BPF_PROG_TYPE_SCHED_CLS:
        case BPF_PROG_TYPE_SCHED_ACT:
                return true;
        default:
                return false;
        }
}

/* verify safety of LD_ABS|LD_IND instructions:
 * - they can only appear in the programs where ctx == skb
 * - since they are wrappers of function calls, they scratch R1-R5 registers,
 *   preserve R6-R9, and store return value into R0
 *
 * Implicit input:
 *   ctx == skb == R6 == CTX
 *
 * Explicit input:
 *   SRC == any register
 *   IMM == 32-bit immediate
 *
 * Output:
 *   R0 - 8/16/32-bit skb data converted to cpu endianness
 */
static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
{
        struct bpf_reg_state *regs = cur_regs(env);
        static const int ctx_reg = BPF_REG_6;
        u8 mode = BPF_MODE(insn->code);
        int i, err;

        if (!may_access_skb(resolve_prog_type(env->prog))) {
                verbose(env, "BPF_LD_[ABS|IND] instructions not allowed for this program type\n");
                return -EINVAL;
        }

        if (!env->ops->gen_ld_abs) {
                verbose(env, "bpf verifier is misconfigured\n");
                return -EINVAL;
        }

        if (insn->dst_reg != BPF_REG_0 || insn->off != 0 ||
            BPF_SIZE(insn->code) == BPF_DW ||
            (mode == BPF_ABS && insn->src_reg != BPF_REG_0)) {
                verbose(env, "BPF_LD_[ABS|IND] uses reserved fields\n");
                return -EINVAL;
        }

        /* check whether implicit source operand (register R6) is readable */
        err = check_reg_arg(env, ctx_reg, SRC_OP);
        if (err)
                return err;

        /* Disallow usage of BPF_LD_[ABS|IND] with reference tracking, as
         * gen_ld_abs() may terminate the program at runtime, leading to
         * reference leak.
         */
        err = check_reference_leak(env);
        if (err) {
                verbose(env, "BPF_LD_[ABS|IND] cannot be mixed with socket references\n");
                return err;
        }

        if (env->cur_state->active_spin_lock) {
                verbose(env, "BPF_LD_[ABS|IND] cannot be used inside bpf_spin_lock-ed region\n");
                return -EINVAL;
        }

        if (regs[ctx_reg].type != PTR_TO_CTX) {
                verbose(env,
                        "at the time of BPF_LD_ABS|IND R6 != pointer to skb\n");
                return -EINVAL;
        }

        if (mode == BPF_IND) {
                /* check explicit source operand */
                err = check_reg_arg(env, insn->src_reg, SRC_OP);
                if (err)
                        return err;
        }

        err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
        if (err < 0)
                return err;

        /* reset caller saved regs to unreadable */
        for (i = 0; i < CALLER_SAVED_REGS; i++) {
                mark_reg_not_init(env, regs, caller_saved[i]);
                check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
        }

        /* mark destination R0 register as readable, since it contains
         * the value fetched from the packet.
         * Already marked as written above.
         */
        mark_reg_unknown(env, regs, BPF_REG_0);
        /* ld_abs load up to 32-bit skb data. */
        regs[BPF_REG_0].subreg_def = env->insn_idx + 1;
        return 0;
}

static int check_return_code(struct bpf_verifier_env *env)
{
        struct tnum enforce_attach_type_range = tnum_unknown;
        const struct bpf_prog *prog = env->prog;
        struct bpf_reg_state *reg;
        struct tnum range = tnum_range(0, 1);
        enum bpf_prog_type prog_type = resolve_prog_type(env->prog);
        int err;
        const bool is_subprog = env->cur_state->frame[0]->subprogno;

        /* LSM and struct_ops func-ptr's return type could be "void" */
        if (!is_subprog &&
            (prog_type == BPF_PROG_TYPE_STRUCT_OPS ||
             prog_type == BPF_PROG_TYPE_LSM) &&
            !prog->aux->attach_func_proto->type)
                return 0;

        /* eBPF calling convetion is such that R0 is used
         * to return the value from eBPF program.
         * Make sure that it's readable at this time
         * of bpf_exit, which means that program wrote
         * something into it earlier
         */
        err = check_reg_arg(env, BPF_REG_0, SRC_OP);
        if (err)
                return err;

        if (is_pointer_value(env, BPF_REG_0)) {
                verbose(env, "R0 leaks addr as return value\n");
                return -EACCES;
        }

        reg = cur_regs(env) + BPF_REG_0;
        if (is_subprog) {
                if (reg->type != SCALAR_VALUE) {
                        verbose(env, "At subprogram exit the register R0 is not a scalar value (%s)\n",
                                reg_type_str[reg->type]);
                        return -EINVAL;
                }
                return 0;
        }

        switch (prog_type) {
        case BPF_PROG_TYPE_CGROUP_SOCK_ADDR:
                if (env->prog->expected_attach_type == BPF_CGROUP_UDP4_RECVMSG ||
                    env->prog->expected_attach_type == BPF_CGROUP_UDP6_RECVMSG ||
                    env->prog->expected_attach_type == BPF_CGROUP_INET4_GETPEERNAME ||
                    env->prog->expected_attach_type == BPF_CGROUP_INET6_GETPEERNAME ||
                    env->prog->expected_attach_type == BPF_CGROUP_INET4_GETSOCKNAME ||
                    env->prog->expected_attach_type == BPF_CGROUP_INET6_GETSOCKNAME)
                        range = tnum_range(1, 1);
                if (env->prog->expected_attach_type == BPF_CGROUP_INET4_BIND ||
                    env->prog->expected_attach_type == BPF_CGROUP_INET6_BIND)
                        range = tnum_range(0, 3);
                break;
        case BPF_PROG_TYPE_CGROUP_SKB:
                if (env->prog->expected_attach_type == BPF_CGROUP_INET_EGRESS) {
                        range = tnum_range(0, 3);
                        enforce_attach_type_range = tnum_range(2, 3);
                }
                break;
        case BPF_PROG_TYPE_CGROUP_SOCK:
        case BPF_PROG_TYPE_SOCK_OPS:
        case BPF_PROG_TYPE_CGROUP_DEVICE:
        case BPF_PROG_TYPE_CGROUP_SYSCTL:
        case BPF_PROG_TYPE_CGROUP_SOCKOPT:
                break;
        case BPF_PROG_TYPE_RAW_TRACEPOINT:
                if (!env->prog->aux->attach_btf_id)
                        return 0;
                range = tnum_const(0);
                break;
        case BPF_PROG_TYPE_TRACING:
                switch (env->prog->expected_attach_type) {
                case BPF_TRACE_FENTRY:
                case BPF_TRACE_FEXIT:
                        range = tnum_const(0);
                        break;
                case BPF_TRACE_RAW_TP:
                case BPF_MODIFY_RETURN:
                        return 0;
                case BPF_TRACE_ITER:
                        break;
                default:
                        return -ENOTSUPP;
                }
                break;
        case BPF_PROG_TYPE_SK_LOOKUP:
                range = tnum_range(SK_DROP, SK_PASS);
                break;
        case BPF_PROG_TYPE_EXT:
                /* freplace program can return anything as its return value
                 * depends on the to-be-replaced kernel func or bpf program.
                 */
        default:
                return 0;
        }

        if (reg->type != SCALAR_VALUE) {
                verbose(env, "At program exit the register R0 is not a known value (%s)\n",
                        reg_type_str[reg->type]);
                return -EINVAL;
        }

        if (!tnum_in(range, reg->var_off)) {
                verbose_invalid_scalar(env, reg, &range, "program exit", "R0");
                return -EINVAL;
        }

        if (!tnum_is_unknown(enforce_attach_type_range) &&
            tnum_in(enforce_attach_type_range, reg->var_off))
                env->prog->enforce_expected_attach_type = 1;
        return 0;
}

/* non-recursive DFS pseudo code
 * 1  procedure DFS-iterative(G,v):
 * 2      label v as discovered
 * 3      let S be a stack
 * 4      S.push(v)
 * 5      while S is not empty
 * 6            t <- S.pop()
 * 7            if t is what we're looking for:
 * 8                return t
 * 9            for all edges e in G.adjacentEdges(t) do
 * 10               if edge e is already labelled
 * 11                   continue with the next edge
 * 12               w <- G.adjacentVertex(t,e)
 * 13               if vertex w is not discovered and not explored
 * 14                   label e as tree-edge
 * 15                   label w as discovered
 * 16                   S.push(w)
 * 17                   continue at 5
 * 18               else if vertex w is discovered
 * 19                   label e as back-edge
 * 20               else
 * 21                   // vertex w is explored
 * 22                   label e as forward- or cross-edge
 * 23           label t as explored
 * 24           S.pop()
 *
 * convention:
 * 0x10 - discovered
 * 0x11 - discovered and fall-through edge labelled
 * 0x12 - discovered and fall-through and branch edges labelled
 * 0x20 - explored
 */

enum {
        DISCOVERED = 0x10,
        EXPLORED = 0x20,
        FALLTHROUGH = 1,
        BRANCH = 2,
};

static u32 state_htab_size(struct bpf_verifier_env *env)
{
        return env->prog->len;
}

static struct bpf_verifier_state_list **explored_state(
                                        struct bpf_verifier_env *env,
                                        int idx)
{
        struct bpf_verifier_state *cur = env->cur_state;
        struct bpf_func_state *state = cur->frame[cur->curframe];

        return &env->explored_states[(idx ^ state->callsite) % state_htab_size(env)];
}

static void init_explored_state(struct bpf_verifier_env *env, int idx)
{
        env->insn_aux_data[idx].prune_point = true;
}

enum {
        DONE_EXPLORING = 0,
        KEEP_EXPLORING = 1,
};

/* t, w, e - match pseudo-code above:
 * t - index of current instruction
 * w - next instruction
 * e - edge
 */
static int push_insn(int t, int w, int e, struct bpf_verifier_env *env,
                     bool loop_ok)
{
        int *insn_stack = env->cfg.insn_stack;
        int *insn_state = env->cfg.insn_state;

        if (e == FALLTHROUGH && insn_state[t] >= (DISCOVERED | FALLTHROUGH))
                return DONE_EXPLORING;

        if (e == BRANCH && insn_state[t] >= (DISCOVERED | BRANCH))
                return DONE_EXPLORING;

        if (w < 0 || w >= env->prog->len) {
                verbose_linfo(env, t, "%d: ", t);
                verbose(env, "jump out of range from insn %d to %d\n", t, w);
                return -EINVAL;
        }

        if (e == BRANCH)
                /* mark branch target for state pruning */
                init_explored_state(env, w);

        if (insn_state[w] == 0) {
                /* tree-edge */
                insn_state[t] = DISCOVERED | e;
                insn_state[w] = DISCOVERED;
                if (env->cfg.cur_stack >= env->prog->len)
                        return -E2BIG;
                insn_stack[env->cfg.cur_stack++] = w;
                return KEEP_EXPLORING;
        } else if ((insn_state[w] & 0xF0) == DISCOVERED) {
                if (loop_ok && env->bpf_capable)
                        return DONE_EXPLORING;
                verbose_linfo(env, t, "%d: ", t);
                verbose_linfo(env, w, "%d: ", w);
                verbose(env, "back-edge from insn %d to %d\n", t, w);
                return -EINVAL;
        } else if (insn_state[w] == EXPLORED) {
                /* forward- or cross-edge */
                insn_state[t] = DISCOVERED | e;
        } else {
                verbose(env, "insn state internal bug\n");
                return -EFAULT;
        }
        return DONE_EXPLORING;
}

static int visit_func_call_insn(int t, int insn_cnt,
                                struct bpf_insn *insns,
                                struct bpf_verifier_env *env,
                                bool visit_callee)
{
        int ret;

        ret = push_insn(t, t + 1, FALLTHROUGH, env, false);
        if (ret)
                return ret;

        if (t + 1 < insn_cnt)
                init_explored_state(env, t + 1);
        if (visit_callee) {
                init_explored_state(env, t);
                ret = push_insn(t, t + insns[t].imm + 1, BRANCH,
                                env, false);
        }
        return ret;
}

/* Visits the instruction at index t and returns one of the following:
 *  < 0 - an error occurred
 *  DONE_EXPLORING - the instruction was fully explored
 *  KEEP_EXPLORING - there is still work to be done before it is fully explored
 */
static int visit_insn(int t, int insn_cnt, struct bpf_verifier_env *env)
{
        struct bpf_insn *insns = env->prog->insnsi;
        int ret;

        if (bpf_pseudo_func(insns + t))
                return visit_func_call_insn(t, insn_cnt, insns, env, true);

        /* All non-branch instructions have a single fall-through edge. */
        if (BPF_CLASS(insns[t].code) != BPF_JMP &&
            BPF_CLASS(insns[t].code) != BPF_JMP32)
                return push_insn(t, t + 1, FALLTHROUGH, env, false);

        switch (BPF_OP(insns[t].code)) {
        case BPF_EXIT:
                return DONE_EXPLORING;

        case BPF_CALL:
                return visit_func_call_insn(t, insn_cnt, insns, env,
                                            insns[t].src_reg == BPF_PSEUDO_CALL);

        case BPF_JA:
                if (BPF_SRC(insns[t].code) != BPF_K)
                        return -EINVAL;

                /* unconditional jump with single edge */
                ret = push_insn(t, t + insns[t].off + 1, FALLTHROUGH, env,
                                true);
                if (ret)
                        return ret;

                /* unconditional jmp is not a good pruning point,
                 * but it's marked, since backtracking needs
                 * to record jmp history in is_state_visited().
                 */
                init_explored_state(env, t + insns[t].off + 1);
                /* tell verifier to check for equivalent states
                 * after every call and jump
                 */
                if (t + 1 < insn_cnt)
                        init_explored_state(env, t + 1);

                return ret;

        default:
                /* conditional jump with two edges */
                init_explored_state(env, t);
                ret = push_insn(t, t + 1, FALLTHROUGH, env, true);
                if (ret)
                        return ret;

                return push_insn(t, t + insns[t].off + 1, BRANCH, env, true);
        }
}

/* non-recursive depth-first-search to detect loops in BPF program
 * loop == back-edge in directed graph
 */
static int check_cfg(struct bpf_verifier_env *env)
{
        int insn_cnt = env->prog->len;
        int *insn_stack, *insn_state;
        int ret = 0;
        int i;

        insn_state = env->cfg.insn_state = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
        if (!insn_state)
                return -ENOMEM;

        insn_stack = env->cfg.insn_stack = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL);
        if (!insn_stack) {
                kvfree(insn_state);
                return -ENOMEM;
        }

        insn_state[0] = DISCOVERED; /* mark 1st insn as discovered */
        insn_stack[0] = 0; /* 0 is the first instruction */
        env->cfg.cur_stack = 1;

        while (env->cfg.cur_stack > 0) {
                int t = insn_stack[env->cfg.cur_stack - 1];

                ret = visit_insn(t, insn_cnt, env);
                switch (ret) {
                case DONE_EXPLORING:
                        insn_state[t] = EXPLORED;
                        env->cfg.cur_stack--;
                        break;
                case KEEP_EXPLORING:
                        break;
                default:
                        if (ret > 0) {
                                verbose(env, "visit_insn internal bug\n");
                                ret = -EFAULT;
                        }
                        goto err_free;
                }
        }

        if (env->cfg.cur_stack < 0) {
                verbose(env, "pop stack internal bug\n");
                ret = -EFAULT;
                goto err_free;
        }

        for (i = 0; i < insn_cnt; i++) {
                if (insn_state[i] != EXPLORED) {
                        verbose(env, "unreachable insn %d\n", i);
                        ret = -EINVAL;
                        goto err_free;
                }
        }
        ret = 0; /* cfg looks good */

err_free:
        kvfree(insn_state);
        kvfree(insn_stack);
        env->cfg.insn_state = env->cfg.insn_stack = NULL;
        return ret;
}

static int check_abnormal_return(struct bpf_verifier_env *env)
{
        int i;

        for (i = 1; i < env->subprog_cnt; i++) {
                if (env->subprog_info[i].has_ld_abs) {
                        verbose(env, "LD_ABS is not allowed in subprogs without BTF\n");
                        return -EINVAL;
                }
                if (env->subprog_info[i].has_tail_call) {
                        verbose(env, "tail_call is not allowed in subprogs without BTF\n");
                        return -EINVAL;
                }
        }
        return 0;
}

/* The minimum supported BTF func info size */
#define MIN_BPF_FUNCINFO_SIZE   8
#define MAX_FUNCINFO_REC_SIZE   252

static int check_btf_func(struct bpf_verifier_env *env,
                          const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
{
        const struct btf_type *type, *func_proto, *ret_type;
        u32 i, nfuncs, urec_size, min_size;
        u32 krec_size = sizeof(struct bpf_func_info);
        struct bpf_func_info *krecord;
        struct bpf_func_info_aux *info_aux = NULL;
        struct bpf_prog *prog;
        const struct btf *btf;
        void __user *urecord;
        u32 prev_offset = 0;
        bool scalar_return;
        int ret = -ENOMEM;

        nfuncs = attr->func_info_cnt;
        if (!nfuncs) {
                if (check_abnormal_return(env))
                        return -EINVAL;
                return 0;
        }

        if (nfuncs != env->subprog_cnt) {
                verbose(env, "number of funcs in func_info doesn't match number of subprogs\n");
                return -EINVAL;
        }

        urec_size = attr->func_info_rec_size;
        if (urec_size < MIN_BPF_FUNCINFO_SIZE ||
            urec_size > MAX_FUNCINFO_REC_SIZE ||
            urec_size % sizeof(u32)) {
                verbose(env, "invalid func info rec size %u\n", urec_size);
                return -EINVAL;
        }

        prog = env->prog;
        btf = prog->aux->btf;

        urecord = u64_to_user_ptr(attr->func_info);
        min_size = min_t(u32, krec_size, urec_size);

        krecord = kvcalloc(nfuncs, krec_size, GFP_KERNEL | __GFP_NOWARN);
        if (!krecord)
                return -ENOMEM;
        info_aux = kcalloc(nfuncs, sizeof(*info_aux), GFP_KERNEL | __GFP_NOWARN);
        if (!info_aux)
                goto err_free;

        for (i = 0; i < nfuncs; i++) {
                ret = bpf_check_uarg_tail_zero(urecord, krec_size, urec_size);
                if (ret) {
                        if (ret == -E2BIG) {
                                verbose(env, "nonzero tailing record in func info");
                                /* set the size kernel expects so loader can zero
                                 * out the rest of the record.
                                 */
                                if (put_user(min_size, &uattr->func_info_rec_size))
                                        ret = -EFAULT;
                        }
                        goto err_free;
                }

                if (copy_from_user(&krecord[i], urecord, min_size)) {
                        ret = -EFAULT;
                        goto err_free;
                }

                /* check insn_off */
                ret = -EINVAL;
                if (i == 0) {
                        if (krecord[i].insn_off) {
                                verbose(env,
                                        "nonzero insn_off %u for the first func info record",
                                        krecord[i].insn_off);
                                goto err_free;
                        }
                } else if (krecord[i].insn_off <= prev_offset) {
                        verbose(env,
                                "same or smaller insn offset (%u) than previous func info record (%u)",
                                krecord[i].insn_off, prev_offset);
                        goto err_free;
                }

                if (env->subprog_info[i].start != krecord[i].insn_off) {
                        verbose(env, "func_info BTF section doesn't match subprog layout in BPF program\n");
                        goto err_free;
                }

                /* check type_id */
                type = btf_type_by_id(btf, krecord[i].type_id);
                if (!type || !btf_type_is_func(type)) {
                        verbose(env, "invalid type id %d in func info",
                                krecord[i].type_id);
                        goto err_free;
                }
                info_aux[i].linkage = BTF_INFO_VLEN(type->info);

                func_proto = btf_type_by_id(btf, type->type);
                if (unlikely(!func_proto || !btf_type_is_func_proto(func_proto)))
                        /* btf_func_check() already verified it during BTF load */
                        goto err_free;
                ret_type = btf_type_skip_modifiers(btf, func_proto->type, NULL);
                scalar_return =
                        btf_type_is_small_int(ret_type) || btf_type_is_enum(ret_type);
                if (i && !scalar_return && env->subprog_info[i].has_ld_abs) {
                        verbose(env, "LD_ABS is only allowed in functions that return 'int'.\n");
                        goto err_free;
                }
                if (i && !scalar_return && env->subprog_info[i].has_tail_call) {
                        verbose(env, "tail_call is only allowed in functions that return 'int'.\n");
                        goto err_free;
                }

                prev_offset = krecord[i].insn_off;
                urecord += urec_size;
        }

        prog->aux->func_info = krecord;
        prog->aux->func_info_cnt = nfuncs;
        prog->aux->func_info_aux = info_aux;
        return 0;

err_free:
        kvfree(krecord);
        kfree(info_aux);
        return ret;
}

static void adjust_btf_func(struct bpf_verifier_env *env)
{
        struct bpf_prog_aux *aux = env->prog->aux;
        int i;

        if (!aux->func_info)
                return;

        for (i = 0; i < env->subprog_cnt; i++)
                aux->func_info[i].insn_off = env->subprog_info[i].start;
}

#define MIN_BPF_LINEINFO_SIZE   (offsetof(struct bpf_line_info, line_col) + \
                sizeof(((struct bpf_line_info *)(0))->line_col))
#define MAX_LINEINFO_REC_SIZE   MAX_FUNCINFO_REC_SIZE

static int check_btf_line(struct bpf_verifier_env *env,
                          const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
{
        u32 i, s, nr_linfo, ncopy, expected_size, rec_size, prev_offset = 0;
        struct bpf_subprog_info *sub;
        struct bpf_line_info *linfo;
        struct bpf_prog *prog;
        const struct btf *btf;
        void __user *ulinfo;
        int err;

        nr_linfo = attr->line_info_cnt;
        if (!nr_linfo)
                return 0;

        rec_size = attr->line_info_rec_size;
        if (rec_size < MIN_BPF_LINEINFO_SIZE ||
            rec_size > MAX_LINEINFO_REC_SIZE ||
            rec_size & (sizeof(u32) - 1))
                return -EINVAL;

        /* Need to zero it in case the userspace may
         * pass in a smaller bpf_line_info object.
         */
        linfo = kvcalloc(nr_linfo, sizeof(struct bpf_line_info),
                         GFP_KERNEL | __GFP_NOWARN);
        if (!linfo)
                return -ENOMEM;

        prog = env->prog;
        btf = prog->aux->btf;

        s = 0;
        sub = env->subprog_info;
        ulinfo = u64_to_user_ptr(attr->line_info);
        expected_size = sizeof(struct bpf_line_info);
        ncopy = min_t(u32, expected_size, rec_size);
        for (i = 0; i < nr_linfo; i++) {
                err = bpf_check_uarg_tail_zero(ulinfo, expected_size, rec_size);
                if (err) {
                        if (err == -E2BIG) {
                                verbose(env, "nonzero tailing record in line_info");
                                if (put_user(expected_size,
                                             &uattr->line_info_rec_size))
                                        err = -EFAULT;
                        }
                        goto err_free;
                }

                if (copy_from_user(&linfo[i], ulinfo, ncopy)) {
                        err = -EFAULT;
                        goto err_free;
                }

                /*
                 * Check insn_off to ensure
                 * 1) strictly increasing AND
                 * 2) bounded by prog->len
                 *
                 * The linfo[0].insn_off == 0 check logically falls into
                 * the later "missing bpf_line_info for func..." case
                 * because the first linfo[0].insn_off must be the
                 * first sub also and the first sub must have
                 * subprog_info[0].start == 0.
                 */
                if ((i && linfo[i].insn_off <= prev_offset) ||
                    linfo[i].insn_off >= prog->len) {
                        verbose(env, "Invalid line_info[%u].insn_off:%u (prev_offset:%u prog->len:%u)\n",
                                i, linfo[i].insn_off, prev_offset,
                                prog->len);
                        err = -EINVAL;
                        goto err_free;
                }

                if (!prog->insnsi[linfo[i].insn_off].code) {
                        verbose(env,
                                "Invalid insn code at line_info[%u].insn_off\n",
                                i);
                        err = -EINVAL;
                        goto err_free;
                }

                if (!btf_name_by_offset(btf, linfo[i].line_off) ||
                    !btf_name_by_offset(btf, linfo[i].file_name_off)) {
                        verbose(env, "Invalid line_info[%u].line_off or .file_name_off\n", i);
                        err = -EINVAL;
                        goto err_free;
                }

                if (s != env->subprog_cnt) {
                        if (linfo[i].insn_off == sub[s].start) {
                                sub[s].linfo_idx = i;
                                s++;
                        } else if (sub[s].start < linfo[i].insn_off) {
                                verbose(env, "missing bpf_line_info for func#%u\n", s);
                                err = -EINVAL;
                                goto err_free;
                        }
                }

                prev_offset = linfo[i].insn_off;
                ulinfo += rec_size;
        }

        if (s != env->subprog_cnt) {
                verbose(env, "missing bpf_line_info for %u funcs starting from func#%u\n",
                        env->subprog_cnt - s, s);
                err = -EINVAL;
                goto err_free;
        }

        prog->aux->linfo = linfo;
        prog->aux->nr_linfo = nr_linfo;

        return 0;

err_free:
        kvfree(linfo);
        return err;
}

static int check_btf_info(struct bpf_verifier_env *env,
                          const union bpf_attr *attr,
                          union bpf_attr __user *uattr)
{
        struct btf *btf;
        int err;

        if (!attr->func_info_cnt && !attr->line_info_cnt) {
                if (check_abnormal_return(env))
                        return -EINVAL;
                return 0;
        }

        btf = btf_get_by_fd(attr->prog_btf_fd);
        if (IS_ERR(btf))
                return PTR_ERR(btf);
        env->prog->aux->btf = btf;

        err = check_btf_func(env, attr, uattr);
        if (err)
                return err;

        err = check_btf_line(env, attr, uattr);
        if (err)
                return err;

        return 0;
}

/* check %cur's range satisfies %old's */
static bool range_within(struct bpf_reg_state *old,
                         struct bpf_reg_state *cur)
{
        return old->umin_value <= cur->umin_value &&
               old->umax_value >= cur->umax_value &&
               old->smin_value <= cur->smin_value &&
               old->smax_value >= cur->smax_value &&
               old->u32_min_value <= cur->u32_min_value &&
               old->u32_max_value >= cur->u32_max_value &&
               old->s32_min_value <= cur->s32_min_value &&
               old->s32_max_value >= cur->s32_max_value;
}

/* Maximum number of register states that can exist at once */
#define ID_MAP_SIZE     (MAX_BPF_REG + MAX_BPF_STACK / BPF_REG_SIZE)
struct idpair {
        u32 old;
        u32 cur;
};

/* If in the old state two registers had the same id, then they need to have
 * the same id in the new state as well.  But that id could be different from
 * the old state, so we need to track the mapping from old to new ids.
 * Once we have seen that, say, a reg with old id 5 had new id 9, any subsequent
 * regs with old id 5 must also have new id 9 for the new state to be safe.  But
 * regs with a different old id could still have new id 9, we don't care about
 * that.
 * So we look through our idmap to see if this old id has been seen before.  If
 * so, we require the new id to match; otherwise, we add the id pair to the map.
 */
static bool check_ids(u32 old_id, u32 cur_id, struct idpair *idmap)
{
        unsigned int i;

        for (i = 0; i < ID_MAP_SIZE; i++) {
                if (!idmap[i].old) {
                        /* Reached an empty slot; haven't seen this id before */
                        idmap[i].old = old_id;
                        idmap[i].cur = cur_id;
                        return true;
                }
                if (idmap[i].old == old_id)
                        return idmap[i].cur == cur_id;
        }
        /* We ran out of idmap slots, which should be impossible */
        WARN_ON_ONCE(1);
        return false;
}

static void clean_func_state(struct bpf_verifier_env *env,
                             struct bpf_func_state *st)
{
        enum bpf_reg_liveness live;
        int i, j;

        for (i = 0; i < BPF_REG_FP; i++) {
                live = st->regs[i].live;
                /* liveness must not touch this register anymore */
                st->regs[i].live |= REG_LIVE_DONE;
                if (!(live & REG_LIVE_READ))
                        /* since the register is unused, clear its state
                         * to make further comparison simpler
                         */
                        __mark_reg_not_init(env, &st->regs[i]);
        }

        for (i = 0; i < st->allocated_stack / BPF_REG_SIZE; i++) {
                live = st->stack[i].spilled_ptr.live;
                /* liveness must not touch this stack slot anymore */
                st->stack[i].spilled_ptr.live |= REG_LIVE_DONE;
                if (!(live & REG_LIVE_READ)) {
                        __mark_reg_not_init(env, &st->stack[i].spilled_ptr);
                        for (j = 0; j < BPF_REG_SIZE; j++)
                                st->stack[i].slot_type[j] = STACK_INVALID;
                }
        }
}

static void clean_verifier_state(struct bpf_verifier_env *env,
                                 struct bpf_verifier_state *st)
{
        int i;

        if (st->frame[0]->regs[0].live & REG_LIVE_DONE)
                /* all regs in this state in all frames were already marked */
                return;

        for (i = 0; i <= st->curframe; i++)
                clean_func_state(env, st->frame[i]);
}

/* the parentage chains form a tree.
 * the verifier states are added to state lists at given insn and
 * pushed into state stack for future exploration.
 * when the verifier reaches bpf_exit insn some of the verifer states
 * stored in the state lists have their final liveness state already,
 * but a lot of states will get revised from liveness point of view when
 * the verifier explores other branches.
 * Example:
 * 1: r0 = 1
 * 2: if r1 == 100 goto pc+1
 * 3: r0 = 2
 * 4: exit
 * when the verifier reaches exit insn the register r0 in the state list of
 * insn 2 will be seen as !REG_LIVE_READ. Then the verifier pops the other_branch
 * of insn 2 and goes exploring further. At the insn 4 it will walk the
 * parentage chain from insn 4 into insn 2 and will mark r0 as REG_LIVE_READ.
 *
 * Since the verifier pushes the branch states as it sees them while exploring
 * the program the condition of walking the branch instruction for the second
 * time means that all states below this branch were already explored and
 * their final liveness markes are already propagated.
 * Hence when the verifier completes the search of state list in is_state_visited()
 * we can call this clean_live_states() function to mark all liveness states
 * as REG_LIVE_DONE to indicate that 'parent' pointers of 'struct bpf_reg_state'
 * will not be used.
 * This function also clears the registers and stack for states that !READ
 * to simplify state merging.
 *
 * Important note here that walking the same branch instruction in the callee
 * doesn't meant that the states are DONE. The verifier has to compare
 * the callsites
 */
static void clean_live_states(struct bpf_verifier_env *env, int insn,
                              struct bpf_verifier_state *cur)
{
        struct bpf_verifier_state_list *sl;
        int i;

        sl = *explored_state(env, insn);
        while (sl) {
                if (sl->state.branches)
                        goto next;
                if (sl->state.insn_idx != insn ||
                    sl->state.curframe != cur->curframe)
                        goto next;
                for (i = 0; i <= cur->curframe; i++)
                        if (sl->state.frame[i]->callsite != cur->frame[i]->callsite)
                                goto next;
                clean_verifier_state(env, &sl->state);
next:
                sl = sl->next;
        }
}

/* Returns true if (rold safe implies rcur safe) */
static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur,
                    struct idpair *idmap)
{
        bool equal;

        if (!(rold->live & REG_LIVE_READ))
                /* explored state didn't use this */
                return true;

        equal = memcmp(rold, rcur, offsetof(struct bpf_reg_state, parent)) == 0;

        if (rold->type == PTR_TO_STACK)
                /* two stack pointers are equal only if they're pointing to
                 * the same stack frame, since fp-8 in foo != fp-8 in bar
                 */
                return equal && rold->frameno == rcur->frameno;

        if (equal)
                return true;

        if (rold->type == NOT_INIT)
                /* explored state can't have used this */
                return true;
        if (rcur->type == NOT_INIT)
                return false;
        switch (rold->type) {
        case SCALAR_VALUE:
                if (rcur->type == SCALAR_VALUE) {
                        if (!rold->precise && !rcur->precise)
                                return true;
                        /* new val must satisfy old val knowledge */
                        return range_within(rold, rcur) &&
                               tnum_in(rold->var_off, rcur->var_off);
                } else {
                        /* We're trying to use a pointer in place of a scalar.
                         * Even if the scalar was unbounded, this could lead to
                         * pointer leaks because scalars are allowed to leak
                         * while pointers are not. We could make this safe in
                         * special cases if root is calling us, but it's
                         * probably not worth the hassle.
                         */
                        return false;
                }
        case PTR_TO_MAP_KEY:
        case PTR_TO_MAP_VALUE:
                /* If the new min/max/var_off satisfy the old ones and
                 * everything else matches, we are OK.
                 * 'id' is not compared, since it's only used for maps with
                 * bpf_spin_lock inside map element and in such cases if
                 * the rest of the prog is valid for one map element then
                 * it's valid for all map elements regardless of the key
                 * used in bpf_map_lookup()
                 */
                return memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)) == 0 &&
                       range_within(rold, rcur) &&
                       tnum_in(rold->var_off, rcur->var_off);
        case PTR_TO_MAP_VALUE_OR_NULL:
                /* a PTR_TO_MAP_VALUE could be safe to use as a
                 * PTR_TO_MAP_VALUE_OR_NULL into the same map.
                 * However, if the old PTR_TO_MAP_VALUE_OR_NULL then got NULL-
                 * checked, doing so could have affected others with the same
                 * id, and we can't check for that because we lost the id when
                 * we converted to a PTR_TO_MAP_VALUE.
                 */
                if (rcur->type != PTR_TO_MAP_VALUE_OR_NULL)
                        return false;
                if (memcmp(rold, rcur, offsetof(struct bpf_reg_state, id)))
                        return false;
                /* Check our ids match any regs they're supposed to */
                return check_ids(rold->id, rcur->id, idmap);
        case PTR_TO_PACKET_META:
        case PTR_TO_PACKET:
                if (rcur->type != rold->type)
                        return false;
                /* We must have at least as much range as the old ptr
                 * did, so that any accesses which were safe before are
                 * still safe.  This is true even if old range < old off,
                 * since someone could have accessed through (ptr - k), or
                 * even done ptr -= k in a register, to get a safe access.
                 */
                if (rold->range > rcur->range)
                        return false;
                /* If the offsets don't match, we can't trust our alignment;
                 * nor can we be sure that we won't fall out of range.
                 */
                if (rold->off != rcur->off)
                        return false;
                /* id relations must be preserved */
                if (rold->id && !check_ids(rold->id, rcur->id, idmap))
                        return false;
                /* new val must satisfy old val knowledge */
                return range_within(rold, rcur) &&
                       tnum_in(rold->var_off, rcur->var_off);
        case PTR_TO_CTX:
        case CONST_PTR_TO_MAP:
        case PTR_TO_PACKET_END:
        case PTR_TO_FLOW_KEYS:
        case PTR_TO_SOCKET:
        case PTR_TO_SOCKET_OR_NULL:
        case PTR_TO_SOCK_COMMON:
        case PTR_TO_SOCK_COMMON_OR_NULL:
        case PTR_TO_TCP_SOCK:
        case PTR_TO_TCP_SOCK_OR_NULL:
        case PTR_TO_XDP_SOCK:
                /* Only valid matches are exact, which memcmp() above
                 * would have accepted
                 */
        default:
                /* Don't know what's going on, just say it's not safe */
                return false;
        }

        /* Shouldn't get here; if we do, say it's not safe */
        WARN_ON_ONCE(1);
        return false;
}

static bool stacksafe(struct bpf_func_state *old,
                      struct bpf_func_state *cur,
                      struct idpair *idmap)
{
        int i, spi;

        /* walk slots of the explored stack and ignore any additional
         * slots in the current stack, since explored(safe) state
         * didn't use them
         */
        for (i = 0; i < old->allocated_stack; i++) {
                spi = i / BPF_REG_SIZE;

                if (!(old->stack[spi].spilled_ptr.live & REG_LIVE_READ)) {
                        i += BPF_REG_SIZE - 1;
                        /* explored state didn't use this */
                        continue;
                }

                if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_INVALID)
                        continue;

                /* explored stack has more populated slots than current stack
                 * and these slots were used
                 */
                if (i >= cur->allocated_stack)
                        return false;

                /* if old state was safe with misc data in the stack
                 * it will be safe with zero-initialized stack.
                 * The opposite is not true
                 */
                if (old->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_MISC &&
                    cur->stack[spi].slot_type[i % BPF_REG_SIZE] == STACK_ZERO)
                        continue;
                if (old->stack[spi].slot_type[i % BPF_REG_SIZE] !=
                    cur->stack[spi].slot_type[i % BPF_REG_SIZE])
                        /* Ex: old explored (safe) state has STACK_SPILL in
                         * this stack slot, but current has STACK_MISC ->
                         * this verifier states are not equivalent,
                         * return false to continue verification of this path
                         */
                        return false;
                if (i % BPF_REG_SIZE)
                        continue;
                if (old->stack[spi].slot_type[0] != STACK_SPILL)
                        continue;
                if (!regsafe(&old->stack[spi].spilled_ptr,
                             &cur->stack[spi].spilled_ptr,
                             idmap))
                        /* when explored and current stack slot are both storing
                         * spilled registers, check that stored pointers types
                         * are the same as well.
                         * Ex: explored safe path could have stored
                         * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -8}
                         * but current path has stored:
                         * (bpf_reg_state) {.type = PTR_TO_STACK, .off = -16}
                         * such verifier states are not equivalent.
                         * return false to continue verification of this path
                         */
                        return false;
        }
        return true;
}

static bool refsafe(struct bpf_func_state *old, struct bpf_func_state *cur)
{
        if (old->acquired_refs != cur->acquired_refs)
                return false;
        return !memcmp(old->refs, cur->refs,
                       sizeof(*old->refs) * old->acquired_refs);
}

/* compare two verifier states
 *
 * all states stored in state_list are known to be valid, since
 * verifier reached 'bpf_exit' instruction through them
 *
 * this function is called when verifier exploring different branches of
 * execution popped from the state stack. If it sees an old state that has
 * more strict register state and more strict stack state then this execution
 * branch doesn't need to be explored further, since verifier already
 * concluded that more strict state leads to valid finish.
 *
 * Therefore two states are equivalent if register state is more conservative
 * and explored stack state is more conservative than the current one.
 * Example:
 *       explored                   current
 * (slot1=INV slot2=MISC) == (slot1=MISC slot2=MISC)
 * (slot1=MISC slot2=MISC) != (slot1=INV slot2=MISC)
 *
 * In other words if current stack state (one being explored) has more
 * valid slots than old one that already passed validation, it means
 * the verifier can stop exploring and conclude that current state is valid too
 *
 * Similarly with registers. If explored state has register type as invalid
 * whereas register type in current state is meaningful, it means that
 * the current state will reach 'bpf_exit' instruction safely
 */
static bool func_states_equal(struct bpf_func_state *old,
                              struct bpf_func_state *cur)
{
        struct idpair *idmap;
        bool ret = false;
        int i;

        idmap = kcalloc(ID_MAP_SIZE, sizeof(struct idpair), GFP_KERNEL);
        /* If we failed to allocate the idmap, just say it's not safe */
        if (!idmap)
                return false;

        for (i = 0; i < MAX_BPF_REG; i++) {
                if (!regsafe(&old->regs[i], &cur->regs[i], idmap))
                        goto out_free;
        }

        if (!stacksafe(old, cur, idmap))
                goto out_free;

        if (!refsafe(old, cur))
                goto out_free;
        ret = true;
out_free:
        kfree(idmap);
        return ret;
}

static bool states_equal(struct bpf_verifier_env *env,
                         struct bpf_verifier_state *old,
                         struct bpf_verifier_state *cur)
{
        int i;

        if (old->curframe != cur->curframe)
                return false;

        /* Verification state from speculative execution simulation
         * must never prune a non-speculative execution one.
         */
        if (old->speculative && !cur->speculative)
                return false;

        if (old->active_spin_lock != cur->active_spin_lock)
                return false;

        /* for states to be equal callsites have to be the same
         * and all frame states need to be equivalent
         */
        for (i = 0; i <= old->curframe; i++) {
                if (old->frame[i]->callsite != cur->frame[i]->callsite)
                        return false;
                if (!func_states_equal(old->frame[i], cur->frame[i]))
                        return false;
        }
        return true;
}

/* Return 0 if no propagation happened. Return negative error code if error
 * happened. Otherwise, return the propagated bit.
 */
static int propagate_liveness_reg(struct bpf_verifier_env *env,
                                  struct bpf_reg_state *reg,
                                  struct bpf_reg_state *parent_reg)
{
        u8 parent_flag = parent_reg->live & REG_LIVE_READ;
        u8 flag = reg->live & REG_LIVE_READ;
        int err;

        /* When comes here, read flags of PARENT_REG or REG could be any of
         * REG_LIVE_READ64, REG_LIVE_READ32, REG_LIVE_NONE. There is no need
         * of propagation if PARENT_REG has strongest REG_LIVE_READ64.
         */
        if (parent_flag == REG_LIVE_READ64 ||
            /* Or if there is no read flag from REG. */
            !flag ||
            /* Or if the read flag from REG is the same as PARENT_REG. */
            parent_flag == flag)
                return 0;

        err = mark_reg_read(env, reg, parent_reg, flag);
        if (err)
                return err;

        return flag;
}

/* A write screens off any subsequent reads; but write marks come from the
 * straight-line code between a state and its parent.  When we arrive at an
 * equivalent state (jump target or such) we didn't arrive by the straight-line
 * code, so read marks in the state must propagate to the parent regardless
 * of the state's write marks. That's what 'parent == state->parent' comparison
 * in mark_reg_read() is for.
 */
static int propagate_liveness(struct bpf_verifier_env *env,
                              const struct bpf_verifier_state *vstate,
                              struct bpf_verifier_state *vparent)
{
        struct bpf_reg_state *state_reg, *parent_reg;
        struct bpf_func_state *state, *parent;
        int i, frame, err = 0;

        if (vparent->curframe != vstate->curframe) {
                WARN(1, "propagate_live: parent frame %d current frame %d\n",
                     vparent->curframe, vstate->curframe);
                return -EFAULT;
        }
        /* Propagate read liveness of registers... */
        BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);
        for (frame = 0; frame <= vstate->curframe; frame++) {
                parent = vparent->frame[frame];
                state = vstate->frame[frame];
                parent_reg = parent->regs;
                state_reg = state->regs;
                /* We don't need to worry about FP liveness, it's read-only */
                for (i = frame < vstate->curframe ? BPF_REG_6 : 0; i < BPF_REG_FP; i++) {
                        err = propagate_liveness_reg(env, &state_reg[i],
                                                     &parent_reg[i]);
                        if (err < 0)
                                return err;
                        if (err == REG_LIVE_READ64)
                                mark_insn_zext(env, &parent_reg[i]);
                }

                /* Propagate stack slots. */
                for (i = 0; i < state->allocated_stack / BPF_REG_SIZE &&
                            i < parent->allocated_stack / BPF_REG_SIZE; i++) {
                        parent_reg = &parent->stack[i].spilled_ptr;
                        state_reg = &state->stack[i].spilled_ptr;
                        err = propagate_liveness_reg(env, state_reg,
                                                     parent_reg);
                        if (err < 0)
                                return err;
                }
        }
        return 0;
}

/* find precise scalars in the previous equivalent state and
 * propagate them into the current state
 */
static int propagate_precision(struct bpf_verifier_env *env,
                               const struct bpf_verifier_state *old)
{
        struct bpf_reg_state *state_reg;
        struct bpf_func_state *state;
        int i, err = 0;

        state = old->frame[old->curframe];
        state_reg = state->regs;
        for (i = 0; i < BPF_REG_FP; i++, state_reg++) {
                if (state_reg->type != SCALAR_VALUE ||
                    !state_reg->precise)
                        continue;
                if (env->log.level & BPF_LOG_LEVEL2)
                        verbose(env, "propagating r%d\n", i);
                err = mark_chain_precision(env, i);
                if (err < 0)
                        return err;
        }

        for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
                if (state->stack[i].slot_type[0] != STACK_SPILL)
                        continue;
                state_reg = &state->stack[i].spilled_ptr;
                if (state_reg->type != SCALAR_VALUE ||
                    !state_reg->precise)
                        continue;
                if (env->log.level & BPF_LOG_LEVEL2)
                        verbose(env, "propagating fp%d\n",
                                (-i - 1) * BPF_REG_SIZE);
                err = mark_chain_precision_stack(env, i);
                if (err < 0)
                        return err;
        }
        return 0;
}

static bool states_maybe_looping(struct bpf_verifier_state *old,
                                 struct bpf_verifier_state *cur)
{
        struct bpf_func_state *fold, *fcur;
        int i, fr = cur->curframe;

        if (old->curframe != fr)
                return false;

        fold = old->frame[fr];
        fcur = cur->frame[fr];
        for (i = 0; i < MAX_BPF_REG; i++)
                if (memcmp(&fold->regs[i], &fcur->regs[i],
                           offsetof(struct bpf_reg_state, parent)))
                        return false;
        return true;
}


static int is_state_visited(struct bpf_verifier_env *env, int insn_idx)
{
        struct bpf_verifier_state_list *new_sl;
        struct bpf_verifier_state_list *sl, **pprev;
        struct bpf_verifier_state *cur = env->cur_state, *new;
        int i, j, err, states_cnt = 0;
        bool add_new_state = env->test_state_freq ? true : false;

        cur->last_insn_idx = env->prev_insn_idx;
        if (!env->insn_aux_data[insn_idx].prune_point)
                /* this 'insn_idx' instruction wasn't marked, so we will not
                 * be doing state search here
                 */
                return 0;

        /* bpf progs typically have pruning point every 4 instructions
         * http://vger.kernel.org/bpfconf2019.html#session-1
         * Do not add new state for future pruning if the verifier hasn't seen
         * at least 2 jumps and at least 8 instructions.
         * This heuristics helps decrease 'total_states' and 'peak_states' metric.
         * In tests that amounts to up to 50% reduction into total verifier
         * memory consumption and 20% verifier time speedup.
         */
        if (env->jmps_processed - env->prev_jmps_processed >= 2 &&
            env->insn_processed - env->prev_insn_processed >= 8)
                add_new_state = true;

        pprev = explored_state(env, insn_idx);
        sl = *pprev;

        clean_live_states(env, insn_idx, cur);

        while (sl) {
                states_cnt++;
                if (sl->state.insn_idx != insn_idx)
                        goto next;
                if (sl->state.branches) {
                        if (states_maybe_looping(&sl->state, cur) &&
                            states_equal(env, &sl->state, cur)) {
                                verbose_linfo(env, insn_idx, "; ");
                                verbose(env, "infinite loop detected at insn %d\n", insn_idx);
                                return -EINVAL;
                        }
                        /* if the verifier is processing a loop, avoid adding new state
                         * too often, since different loop iterations have distinct
                         * states and may not help future pruning.
                         * This threshold shouldn't be too low to make sure that
                         * a loop with large bound will be rejected quickly.
                         * The most abusive loop will be:
                         * r1 += 1
                         * if r1 < 1000000 goto pc-2
                         * 1M insn_procssed limit / 100 == 10k peak states.
                         * This threshold shouldn't be too high either, since states
                         * at the end of the loop are likely to be useful in pruning.
                         */
                        if (env->jmps_processed - env->prev_jmps_processed < 20 &&
                            env->insn_processed - env->prev_insn_processed < 100)
                                add_new_state = false;
                        goto miss;
                }
                if (states_equal(env, &sl->state, cur)) {
                        sl->hit_cnt++;
                        /* reached equivalent register/stack state,
                         * prune the search.
                         * Registers read by the continuation are read by us.
                         * If we have any write marks in env->cur_state, they
                         * will prevent corresponding reads in the continuation
                         * from reaching our parent (an explored_state).  Our
                         * own state will get the read marks recorded, but
                         * they'll be immediately forgotten as we're pruning
                         * this state and will pop a new one.
                         */
                        err = propagate_liveness(env, &sl->state, cur);

                        /* if previous state reached the exit with precision and
                         * current state is equivalent to it (except precsion marks)
                         * the precision needs to be propagated back in
                         * the current state.
                         */
                        err = err ? : push_jmp_history(env, cur);
                        err = err ? : propagate_precision(env, &sl->state);
                        if (err)
                                return err;
                        return 1;
                }
miss:
                /* when new state is not going to be added do not increase miss count.
                 * Otherwise several loop iterations will remove the state
                 * recorded earlier. The goal of these heuristics is to have
                 * states from some iterations of the loop (some in the beginning
                 * and some at the end) to help pruning.
                 */
                if (add_new_state)
                        sl->miss_cnt++;
                /* heuristic to determine whether this state is beneficial
                 * to keep checking from state equivalence point of view.
                 * Higher numbers increase max_states_per_insn and verification time,
                 * but do not meaningfully decrease insn_processed.
                 */
                if (sl->miss_cnt > sl->hit_cnt * 3 + 3) {
                        /* the state is unlikely to be useful. Remove it to
                         * speed up verification
                         */
                        *pprev = sl->next;
                        if (sl->state.frame[0]->regs[0].live & REG_LIVE_DONE) {
                                u32 br = sl->state.branches;

                                WARN_ONCE(br,
                                          "BUG live_done but branches_to_explore %d\n",
                                          br);
                                free_verifier_state(&sl->state, false);
                                kfree(sl);
                                env->peak_states--;
                        } else {
                                /* cannot free this state, since parentage chain may
                                 * walk it later. Add it for free_list instead to
                                 * be freed at the end of verification
                                 */
                                sl->next = env->free_list;
                                env->free_list = sl;
                        }
                        sl = *pprev;
                        continue;
                }
next:
                pprev = &sl->next;
                sl = *pprev;
        }

        if (env->max_states_per_insn < states_cnt)
                env->max_states_per_insn = states_cnt;

        if (!env->bpf_capable && states_cnt > BPF_COMPLEXITY_LIMIT_STATES)
                return push_jmp_history(env, cur);

        if (!add_new_state)
                return push_jmp_history(env, cur);

        /* There were no equivalent states, remember the current one.
         * Technically the current state is not proven to be safe yet,
         * but it will either reach outer most bpf_exit (which means it's safe)
         * or it will be rejected. When there are no loops the verifier won't be
         * seeing this tuple (frame[0].callsite, frame[1].callsite, .. insn_idx)
         * again on the way to bpf_exit.
         * When looping the sl->state.branches will be > 0 and this state
         * will not be considered for equivalence until branches == 0.
         */
        new_sl = kzalloc(sizeof(struct bpf_verifier_state_list), GFP_KERNEL);
        if (!new_sl)
                return -ENOMEM;
        env->total_states++;
        env->peak_states++;
        env->prev_jmps_processed = env->jmps_processed;
        env->prev_insn_processed = env->insn_processed;

        /* add new state to the head of linked list */
        new = &new_sl->state;
        err = copy_verifier_state(new, cur);
        if (err) {
                free_verifier_state(new, false);
                kfree(new_sl);
                return err;
        }
        new->insn_idx = insn_idx;
        WARN_ONCE(new->branches != 1,
                  "BUG is_state_visited:branches_to_explore=%d insn %d\n", new->branches, insn_idx);

        cur->parent = new;
        cur->first_insn_idx = insn_idx;
        clear_jmp_history(cur);
        new_sl->next = *explored_state(env, insn_idx);
        *explored_state(env, insn_idx) = new_sl;
        /* connect new state to parentage chain. Current frame needs all
         * registers connected. Only r6 - r9 of the callers are alive (pushed
         * to the stack implicitly by JITs) so in callers' frames connect just
         * r6 - r9 as an optimization. Callers will have r1 - r5 connected to
         * the state of the call instruction (with WRITTEN set), and r0 comes
         * from callee with its full parentage chain, anyway.
         */
        /* clear write marks in current state: the writes we did are not writes
         * our child did, so they don't screen off its reads from us.
         * (There are no read marks in current state, because reads always mark
         * their parent and current state never has children yet.  Only
         * explored_states can get read marks.)
         */
        for (j = 0; j <= cur->curframe; j++) {
                for (i = j < cur->curframe ? BPF_REG_6 : 0; i < BPF_REG_FP; i++)
                        cur->frame[j]->regs[i].parent = &new->frame[j]->regs[i];
                for (i = 0; i < BPF_REG_FP; i++)
                        cur->frame[j]->regs[i].live = REG_LIVE_NONE;
        }

        /* all stack frames are accessible from callee, clear them all */
        for (j = 0; j <= cur->curframe; j++) {
                struct bpf_func_state *frame = cur->frame[j];
                struct bpf_func_state *newframe = new->frame[j];

                for (i = 0; i < frame->allocated_stack / BPF_REG_SIZE; i++) {
                        frame->stack[i].spilled_ptr.live = REG_LIVE_NONE;
                        frame->stack[i].spilled_ptr.parent =
                                                &newframe->stack[i].spilled_ptr;
                }
        }
        return 0;
}

/* Return true if it's OK to have the same insn return a different type. */
static bool reg_type_mismatch_ok(enum bpf_reg_type type)
{
        switch (type) {
        case PTR_TO_CTX:
        case PTR_TO_SOCKET:
        case PTR_TO_SOCKET_OR_NULL:
        case PTR_TO_SOCK_COMMON:
        case PTR_TO_SOCK_COMMON_OR_NULL:
        case PTR_TO_TCP_SOCK:
        case PTR_TO_TCP_SOCK_OR_NULL:
        case PTR_TO_XDP_SOCK:
        case PTR_TO_BTF_ID:
        case PTR_TO_BTF_ID_OR_NULL:
                return false;
        default:
                return true;
        }
}

/* If an instruction was previously used with particular pointer types, then we
 * need to be careful to avoid cases such as the below, where it may be ok
 * for one branch accessing the pointer, but not ok for the other branch:
 *
 * R1 = sock_ptr
 * goto X;
 * ...
 * R1 = some_other_valid_ptr;
 * goto X;
 * ...
 * R2 = *(u32 *)(R1 + 0);
 */
static bool reg_type_mismatch(enum bpf_reg_type src, enum bpf_reg_type prev)
{
        return src != prev && (!reg_type_mismatch_ok(src) ||
                               !reg_type_mismatch_ok(prev));
}

static int do_check(struct bpf_verifier_env *env)
{
        bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
        struct bpf_verifier_state *state = env->cur_state;
        struct bpf_insn *insns = env->prog->insnsi;
        struct bpf_reg_state *regs;
        int insn_cnt = env->prog->len;
        bool do_print_state = false;
        int prev_insn_idx = -1;

        for (;;) {
                struct bpf_insn *insn;
                u8 class;
                int err;

                env->prev_insn_idx = prev_insn_idx;
                if (env->insn_idx >= insn_cnt) {
                        verbose(env, "invalid insn idx %d insn_cnt %d\n",
                                env->insn_idx, insn_cnt);
                        return -EFAULT;
                }

                insn = &insns[env->insn_idx];
                class = BPF_CLASS(insn->code);

                if (++env->insn_processed > BPF_COMPLEXITY_LIMIT_INSNS) {
                        verbose(env,
                                "BPF program is too large. Processed %d insn\n",
                                env->insn_processed);
                        return -E2BIG;
                }

                err = is_state_visited(env, env->insn_idx);
                if (err < 0)
                        return err;
                if (err == 1) {
                        /* found equivalent state, can prune the search */
                        if (env->log.level & BPF_LOG_LEVEL) {
                                if (do_print_state)
                                        verbose(env, "\nfrom %d to %d%s: safe\n",
                                                env->prev_insn_idx, env->insn_idx,
                                                env->cur_state->speculative ?
                                                " (speculative execution)" : "");
                                else
                                        verbose(env, "%d: safe\n", env->insn_idx);
                        }
                        goto process_bpf_exit;
                }

                if (signal_pending(current))
                        return -EAGAIN;

                if (need_resched())
                        cond_resched();

                if (env->log.level & BPF_LOG_LEVEL2 ||
                    (env->log.level & BPF_LOG_LEVEL && do_print_state)) {
                        if (env->log.level & BPF_LOG_LEVEL2)
                                verbose(env, "%d:", env->insn_idx);
                        else
                                verbose(env, "\nfrom %d to %d%s:",
                                        env->prev_insn_idx, env->insn_idx,
                                        env->cur_state->speculative ?
                                        " (speculative execution)" : "");
                        print_verifier_state(env, state->frame[state->curframe]);
                        do_print_state = false;
                }

                if (env->log.level & BPF_LOG_LEVEL) {
                        const struct bpf_insn_cbs cbs = {
                                .cb_print       = verbose,
                                .private_data   = env,
                        };

                        verbose_linfo(env, env->insn_idx, "; ");
                        verbose(env, "%d: ", env->insn_idx);
                        print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
                }

                if (bpf_prog_is_dev_bound(env->prog->aux)) {
                        err = bpf_prog_offload_verify_insn(env, env->insn_idx,
                                                           env->prev_insn_idx);
                        if (err)
                                return err;
                }

                regs = cur_regs(env);
                env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
                prev_insn_idx = env->insn_idx;

                if (class == BPF_ALU || class == BPF_ALU64) {
                        err = check_alu_op(env, insn);
                        if (err)
                                return err;

                } else if (class == BPF_LDX) {
                        enum bpf_reg_type *prev_src_type, src_reg_type;

                        /* check for reserved fields is already done */

                        /* check src operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;

                        err = check_reg_arg(env, insn->dst_reg, DST_OP_NO_MARK);
                        if (err)
                                return err;

                        src_reg_type = regs[insn->src_reg].type;

                        /* check that memory (src_reg + off) is readable,
                         * the state of dst_reg will be updated by this func
                         */
                        err = check_mem_access(env, env->insn_idx, insn->src_reg,
                                               insn->off, BPF_SIZE(insn->code),
                                               BPF_READ, insn->dst_reg, false);
                        if (err)
                                return err;

                        prev_src_type = &env->insn_aux_data[env->insn_idx].ptr_type;

                        if (*prev_src_type == NOT_INIT) {
                                /* saw a valid insn
                                 * dst_reg = *(u32 *)(src_reg + off)
                                 * save type to validate intersecting paths
                                 */
                                *prev_src_type = src_reg_type;

                        } else if (reg_type_mismatch(src_reg_type, *prev_src_type)) {
                                /* ABuser program is trying to use the same insn
                                 * dst_reg = *(u32*) (src_reg + off)
                                 * with different pointer types:
                                 * src_reg == ctx in one branch and
                                 * src_reg == stack|map in some other branch.
                                 * Reject it.
                                 */
                                verbose(env, "same insn cannot be used with different pointers\n");
                                return -EINVAL;
                        }

                } else if (class == BPF_STX) {
                        enum bpf_reg_type *prev_dst_type, dst_reg_type;

                        if (BPF_MODE(insn->code) == BPF_ATOMIC) {
                                err = check_atomic(env, env->insn_idx, insn);
                                if (err)
                                        return err;
                                env->insn_idx++;
                                continue;
                        }

                        if (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0) {
                                verbose(env, "BPF_STX uses reserved fields\n");
                                return -EINVAL;
                        }

                        /* check src1 operand */
                        err = check_reg_arg(env, insn->src_reg, SRC_OP);
                        if (err)
                                return err;
                        /* check src2 operand */
                        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                        if (err)
                                return err;

                        dst_reg_type = regs[insn->dst_reg].type;

                        /* check that memory (dst_reg + off) is writeable */
                        err = check_mem_access(env, env->insn_idx, insn->dst_reg,
                                               insn->off, BPF_SIZE(insn->code),
                                               BPF_WRITE, insn->src_reg, false);
                        if (err)
                                return err;

                        prev_dst_type = &env->insn_aux_data[env->insn_idx].ptr_type;

                        if (*prev_dst_type == NOT_INIT) {
                                *prev_dst_type = dst_reg_type;
                        } else if (reg_type_mismatch(dst_reg_type, *prev_dst_type)) {
                                verbose(env, "same insn cannot be used with different pointers\n");
                                return -EINVAL;
                        }

                } else if (class == BPF_ST) {
                        if (BPF_MODE(insn->code) != BPF_MEM ||
                            insn->src_reg != BPF_REG_0) {
                                verbose(env, "BPF_ST uses reserved fields\n");
                                return -EINVAL;
                        }
                        /* check src operand */
                        err = check_reg_arg(env, insn->dst_reg, SRC_OP);
                        if (err)
                                return err;

                        if (is_ctx_reg(env, insn->dst_reg)) {
                                verbose(env, "BPF_ST stores into R%d %s is not allowed\n",
                                        insn->dst_reg,
                                        reg_type_str[reg_state(env, insn->dst_reg)->type]);
                                return -EACCES;
                        }

                        /* check that memory (dst_reg + off) is writeable */
                        err = check_mem_access(env, env->insn_idx, insn->dst_reg,
                                               insn->off, BPF_SIZE(insn->code),
                                               BPF_WRITE, -1, false);
                        if (err)
                                return err;

                } else if (class == BPF_JMP || class == BPF_JMP32) {
                        u8 opcode = BPF_OP(insn->code);

                        env->jmps_processed++;
                        if (opcode == BPF_CALL) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->off != 0 ||
                                    (insn->src_reg != BPF_REG_0 &&
                                     insn->src_reg != BPF_PSEUDO_CALL) ||
                                    insn->dst_reg != BPF_REG_0 ||
                                    class == BPF_JMP32) {
                                        verbose(env, "BPF_CALL uses reserved fields\n");
                                        return -EINVAL;
                                }

                                if (env->cur_state->active_spin_lock &&
                                    (insn->src_reg == BPF_PSEUDO_CALL ||
                                     insn->imm != BPF_FUNC_spin_unlock)) {
                                        verbose(env, "function calls are not allowed while holding a lock\n");
                                        return -EINVAL;
                                }
                                if (insn->src_reg == BPF_PSEUDO_CALL)
                                        err = check_func_call(env, insn, &env->insn_idx);
                                else
                                        err = check_helper_call(env, insn, &env->insn_idx);
                                if (err)
                                        return err;
                        } else if (opcode == BPF_JA) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->imm != 0 ||
                                    insn->src_reg != BPF_REG_0 ||
                                    insn->dst_reg != BPF_REG_0 ||
                                    class == BPF_JMP32) {
                                        verbose(env, "BPF_JA uses reserved fields\n");
                                        return -EINVAL;
                                }

                                env->insn_idx += insn->off + 1;
                                continue;

                        } else if (opcode == BPF_EXIT) {
                                if (BPF_SRC(insn->code) != BPF_K ||
                                    insn->imm != 0 ||
                                    insn->src_reg != BPF_REG_0 ||
                                    insn->dst_reg != BPF_REG_0 ||
                                    class == BPF_JMP32) {
                                        verbose(env, "BPF_EXIT uses reserved fields\n");
                                        return -EINVAL;
                                }

                                if (env->cur_state->active_spin_lock) {
                                        verbose(env, "bpf_spin_unlock is missing\n");
                                        return -EINVAL;
                                }

                                if (state->curframe) {
                                        /* exit from nested function */
                                        err = prepare_func_exit(env, &env->insn_idx);
                                        if (err)
                                                return err;
                                        do_print_state = true;
                                        continue;
                                }

                                err = check_reference_leak(env);
                                if (err)
                                        return err;

                                err = check_return_code(env);
                                if (err)
                                        return err;
process_bpf_exit:
                                update_branch_counts(env, env->cur_state);
                                err = pop_stack(env, &prev_insn_idx,
                                                &env->insn_idx, pop_log);
                                if (err < 0) {
                                        if (err != -ENOENT)
                                                return err;
                                        break;
                                } else {
                                        do_print_state = true;
                                        continue;
                                }
                        } else {
                                err = check_cond_jmp_op(env, insn, &env->insn_idx);
                                if (err)
                                        return err;
                        }
                } else if (class == BPF_LD) {
                        u8 mode = BPF_MODE(insn->code);

                        if (mode == BPF_ABS || mode == BPF_IND) {
                                err = check_ld_abs(env, insn);
                                if (err)
                                        return err;

                        } else if (mode == BPF_IMM) {
                                err = check_ld_imm(env, insn);
                                if (err)
                                        return err;

                                env->insn_idx++;
                                env->insn_aux_data[env->insn_idx].seen = env->pass_cnt;
                        } else {
                                verbose(env, "invalid BPF_LD mode\n");
                                return -EINVAL;
                        }
                } else {
                        verbose(env, "unknown insn class %d\n", class);
                        return -EINVAL;
                }

                env->insn_idx++;
        }

        return 0;
}

static int find_btf_percpu_datasec(struct btf *btf)
{
        const struct btf_type *t;
        const char *tname;
        int i, n;

        /*
         * Both vmlinux and module each have their own ".data..percpu"
         * DATASECs in BTF. So for module's case, we need to skip vmlinux BTF
         * types to look at only module's own BTF types.
         */
        n = btf_nr_types(btf);
        if (btf_is_module(btf))
                i = btf_nr_types(btf_vmlinux);
        else
                i = 1;

        for(; i < n; i++) {
                t = btf_type_by_id(btf, i);
                if (BTF_INFO_KIND(t->info) != BTF_KIND_DATASEC)
                        continue;

                tname = btf_name_by_offset(btf, t->name_off);
                if (!strcmp(tname, ".data..percpu"))
                        return i;
        }

        return -ENOENT;
}

/* replace pseudo btf_id with kernel symbol address */
static int check_pseudo_btf_id(struct bpf_verifier_env *env,
                               struct bpf_insn *insn,
                               struct bpf_insn_aux_data *aux)
{
        const struct btf_var_secinfo *vsi;
        const struct btf_type *datasec;
        struct btf_mod_pair *btf_mod;
        const struct btf_type *t;
        const char *sym_name;
        bool percpu = false;
        u32 type, id = insn->imm;
        struct btf *btf;
        s32 datasec_id;
        u64 addr;
        int i, btf_fd, err;

        btf_fd = insn[1].imm;
        if (btf_fd) {
                btf = btf_get_by_fd(btf_fd);
                if (IS_ERR(btf)) {
                        verbose(env, "invalid module BTF object FD specified.\n");
                        return -EINVAL;
                }
        } else {
                if (!btf_vmlinux) {
                        verbose(env, "kernel is missing BTF, make sure CONFIG_DEBUG_INFO_BTF=y is specified in Kconfig.\n");
                        return -EINVAL;
                }
                btf = btf_vmlinux;
                btf_get(btf);
        }

        t = btf_type_by_id(btf, id);
        if (!t) {
                verbose(env, "ldimm64 insn specifies invalid btf_id %d.\n", id);
                err = -ENOENT;
                goto err_put;
        }

        if (!btf_type_is_var(t)) {
                verbose(env, "pseudo btf_id %d in ldimm64 isn't KIND_VAR.\n", id);
                err = -EINVAL;
                goto err_put;
        }

        sym_name = btf_name_by_offset(btf, t->name_off);
        addr = kallsyms_lookup_name(sym_name);
        if (!addr) {
                verbose(env, "ldimm64 failed to find the address for kernel symbol '%s'.\n",
                        sym_name);
                err = -ENOENT;
                goto err_put;
        }

        datasec_id = find_btf_percpu_datasec(btf);
        if (datasec_id > 0) {
                datasec = btf_type_by_id(btf, datasec_id);
                for_each_vsi(i, datasec, vsi) {
                        if (vsi->type == id) {
                                percpu = true;
                                break;
                        }
                }
        }

        insn[0].imm = (u32)addr;
        insn[1].imm = addr >> 32;

        type = t->type;
        t = btf_type_skip_modifiers(btf, type, NULL);
        if (percpu) {
                aux->btf_var.reg_type = PTR_TO_PERCPU_BTF_ID;
                aux->btf_var.btf = btf;
                aux->btf_var.btf_id = type;
        } else if (!btf_type_is_struct(t)) {
                const struct btf_type *ret;
                const char *tname;
                u32 tsize;

                /* resolve the type size of ksym. */
                ret = btf_resolve_size(btf, t, &tsize);
                if (IS_ERR(ret)) {
                        tname = btf_name_by_offset(btf, t->name_off);
                        verbose(env, "ldimm64 unable to resolve the size of type '%s': %ld\n",
                                tname, PTR_ERR(ret));
                        err = -EINVAL;
                        goto err_put;
                }
                aux->btf_var.reg_type = PTR_TO_MEM;
                aux->btf_var.mem_size = tsize;
        } else {
                aux->btf_var.reg_type = PTR_TO_BTF_ID;
                aux->btf_var.btf = btf;
                aux->btf_var.btf_id = type;
        }

        /* check whether we recorded this BTF (and maybe module) already */
        for (i = 0; i < env->used_btf_cnt; i++) {
                if (env->used_btfs[i].btf == btf) {
                        btf_put(btf);
                        return 0;
                }
        }

        if (env->used_btf_cnt >= MAX_USED_BTFS) {
                err = -E2BIG;
                goto err_put;
        }

        btf_mod = &env->used_btfs[env->used_btf_cnt];
        btf_mod->btf = btf;
        btf_mod->module = NULL;

        /* if we reference variables from kernel module, bump its refcount */
        if (btf_is_module(btf)) {
                btf_mod->module = btf_try_get_module(btf);
                if (!btf_mod->module) {
                        err = -ENXIO;
                        goto err_put;
                }
        }

        env->used_btf_cnt++;

        return 0;
err_put:
        btf_put(btf);
        return err;
}

static int check_map_prealloc(struct bpf_map *map)
{
        return (map->map_type != BPF_MAP_TYPE_HASH &&
                map->map_type != BPF_MAP_TYPE_PERCPU_HASH &&
                map->map_type != BPF_MAP_TYPE_HASH_OF_MAPS) ||
                !(map->map_flags & BPF_F_NO_PREALLOC);
}

static bool is_tracing_prog_type(enum bpf_prog_type type)
{
        switch (type) {
        case BPF_PROG_TYPE_KPROBE:
        case BPF_PROG_TYPE_TRACEPOINT:
        case BPF_PROG_TYPE_PERF_EVENT:
        case BPF_PROG_TYPE_RAW_TRACEPOINT:
                return true;
        default:
                return false;
        }
}

static bool is_preallocated_map(struct bpf_map *map)
{
        if (!check_map_prealloc(map))
                return false;
        if (map->inner_map_meta && !check_map_prealloc(map->inner_map_meta))
                return false;
        return true;
}

static int check_map_prog_compatibility(struct bpf_verifier_env *env,
                                        struct bpf_map *map,
                                        struct bpf_prog *prog)

{
        enum bpf_prog_type prog_type = resolve_prog_type(prog);
        /*
         * Validate that trace type programs use preallocated hash maps.
         *
         * For programs attached to PERF events this is mandatory as the
         * perf NMI can hit any arbitrary code sequence.
         *
         * All other trace types using preallocated hash maps are unsafe as
         * well because tracepoint or kprobes can be inside locked regions
         * of the memory allocator or at a place where a recursion into the
         * memory allocator would see inconsistent state.
         *
         * On RT enabled kernels run-time allocation of all trace type
         * programs is strictly prohibited due to lock type constraints. On
         * !RT kernels it is allowed for backwards compatibility reasons for
         * now, but warnings are emitted so developers are made aware of
         * the unsafety and can fix their programs before this is enforced.
         */
        if (is_tracing_prog_type(prog_type) && !is_preallocated_map(map)) {
                if (prog_type == BPF_PROG_TYPE_PERF_EVENT) {
                        verbose(env, "perf_event programs can only use preallocated hash map\n");
                        return -EINVAL;
                }
                if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
                        verbose(env, "trace type programs can only use preallocated hash map\n");
                        return -EINVAL;
                }
                WARN_ONCE(1, "trace type BPF program uses run-time allocation\n");
                verbose(env, "trace type programs with run-time allocated hash maps are unsafe. Switch to preallocated hash maps.\n");
        }

        if (map_value_has_spin_lock(map)) {
                if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
                        verbose(env, "socket filter progs cannot use bpf_spin_lock yet\n");
                        return -EINVAL;
                }

                if (is_tracing_prog_type(prog_type)) {
                        verbose(env, "tracing progs cannot use bpf_spin_lock yet\n");
                        return -EINVAL;
                }

                if (prog->aux->sleepable) {
                        verbose(env, "sleepable progs cannot use bpf_spin_lock yet\n");
                        return -EINVAL;
                }
        }

        if ((bpf_prog_is_dev_bound(prog->aux) || bpf_map_is_dev_bound(map)) &&
            !bpf_offload_prog_map_match(prog, map)) {
                verbose(env, "offload device mismatch between prog and map\n");
                return -EINVAL;
        }

        if (map->map_type == BPF_MAP_TYPE_STRUCT_OPS) {
                verbose(env, "bpf_struct_ops map cannot be used in prog\n");
                return -EINVAL;
        }

        if (prog->aux->sleepable)
                switch (map->map_type) {
                case BPF_MAP_TYPE_HASH:
                case BPF_MAP_TYPE_LRU_HASH:
                case BPF_MAP_TYPE_ARRAY:
                case BPF_MAP_TYPE_PERCPU_HASH:
                case BPF_MAP_TYPE_PERCPU_ARRAY:
                case BPF_MAP_TYPE_LRU_PERCPU_HASH:
                case BPF_MAP_TYPE_ARRAY_OF_MAPS:
                case BPF_MAP_TYPE_HASH_OF_MAPS:
                        if (!is_preallocated_map(map)) {
                                verbose(env,
                                        "Sleepable programs can only use preallocated maps\n");
                                return -EINVAL;
                        }
                        break;
                case BPF_MAP_TYPE_RINGBUF:
                        break;
                default:
                        verbose(env,
                                "Sleepable programs can only use array, hash, and ringbuf maps\n");
                        return -EINVAL;
                }

        return 0;
}

static bool bpf_map_is_cgroup_storage(struct bpf_map *map)
{
        return (map->map_type == BPF_MAP_TYPE_CGROUP_STORAGE ||
                map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE);
}

/* find and rewrite pseudo imm in ld_imm64 instructions:
 *
 * 1. if it accesses map FD, replace it with actual map pointer.
 * 2. if it accesses btf_id of a VAR, replace it with pointer to the var.
 *
 * NOTE: btf_vmlinux is required for converting pseudo btf_id.
 */
static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
{
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int i, j, err;

        err = bpf_prog_calc_tag(env->prog);
        if (err)
                return err;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (BPF_CLASS(insn->code) == BPF_LDX &&
                    (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
                        verbose(env, "BPF_LDX uses reserved fields\n");
                        return -EINVAL;
                }

                if (insn[0].code == (BPF_LD | BPF_IMM | BPF_DW)) {
                        struct bpf_insn_aux_data *aux;
                        struct bpf_map *map;
                        struct fd f;
                        u64 addr;

                        if (i == insn_cnt - 1 || insn[1].code != 0 ||
                            insn[1].dst_reg != 0 || insn[1].src_reg != 0 ||
                            insn[1].off != 0) {
                                verbose(env, "invalid bpf_ld_imm64 insn\n");
                                return -EINVAL;
                        }

                        if (insn[0].src_reg == 0)
                                /* valid generic load 64-bit imm */
                                goto next_insn;

                        if (insn[0].src_reg == BPF_PSEUDO_BTF_ID) {
                                aux = &env->insn_aux_data[i];
                                err = check_pseudo_btf_id(env, insn, aux);
                                if (err)
                                        return err;
                                goto next_insn;
                        }

                        if (insn[0].src_reg == BPF_PSEUDO_FUNC) {
                                aux = &env->insn_aux_data[i];
                                aux->ptr_type = PTR_TO_FUNC;
                                goto next_insn;
                        }

                        /* In final convert_pseudo_ld_imm64() step, this is
                         * converted into regular 64-bit imm load insn.
                         */
                        if ((insn[0].src_reg != BPF_PSEUDO_MAP_FD &&
                             insn[0].src_reg != BPF_PSEUDO_MAP_VALUE) ||
                            (insn[0].src_reg == BPF_PSEUDO_MAP_FD &&
                             insn[1].imm != 0)) {
                                verbose(env,
                                        "unrecognized bpf_ld_imm64 insn\n");
                                return -EINVAL;
                        }

                        f = fdget(insn[0].imm);
                        map = __bpf_map_get(f);
                        if (IS_ERR(map)) {
                                verbose(env, "fd %d is not pointing to valid bpf_map\n",
                                        insn[0].imm);
                                return PTR_ERR(map);
                        }

                        err = check_map_prog_compatibility(env, map, env->prog);
                        if (err) {
                                fdput(f);
                                return err;
                        }

                        aux = &env->insn_aux_data[i];
                        if (insn->src_reg == BPF_PSEUDO_MAP_FD) {
                                addr = (unsigned long)map;
                        } else {
                                u32 off = insn[1].imm;

                                if (off >= BPF_MAX_VAR_OFF) {
                                        verbose(env, "direct value offset of %u is not allowed\n", off);
                                        fdput(f);
                                        return -EINVAL;
                                }

                                if (!map->ops->map_direct_value_addr) {
                                        verbose(env, "no direct value access support for this map type\n");
                                        fdput(f);
                                        return -EINVAL;
                                }

                                err = map->ops->map_direct_value_addr(map, &addr, off);
                                if (err) {
                                        verbose(env, "invalid access to map value pointer, value_size=%u off=%u\n",
                                                map->value_size, off);
                                        fdput(f);
                                        return err;
                                }

                                aux->map_off = off;
                                addr += off;
                        }

                        insn[0].imm = (u32)addr;
                        insn[1].imm = addr >> 32;

                        /* check whether we recorded this map already */
                        for (j = 0; j < env->used_map_cnt; j++) {
                                if (env->used_maps[j] == map) {
                                        aux->map_index = j;
                                        fdput(f);
                                        goto next_insn;
                                }
                        }

                        if (env->used_map_cnt >= MAX_USED_MAPS) {
                                fdput(f);
                                return -E2BIG;
                        }

                        /* hold the map. If the program is rejected by verifier,
                         * the map will be released by release_maps() or it
                         * will be used by the valid program until it's unloaded
                         * and all maps are released in free_used_maps()
                         */
                        bpf_map_inc(map);

                        aux->map_index = env->used_map_cnt;
                        env->used_maps[env->used_map_cnt++] = map;

                        if (bpf_map_is_cgroup_storage(map) &&
                            bpf_cgroup_storage_assign(env->prog->aux, map)) {
                                verbose(env, "only one cgroup storage of each type is allowed\n");
                                fdput(f);
                                return -EBUSY;
                        }

                        fdput(f);
next_insn:
                        insn++;
                        i++;
                        continue;
                }

                /* Basic sanity check before we invest more work here. */
                if (!bpf_opcode_in_insntable(insn->code)) {
                        verbose(env, "unknown opcode %02x\n", insn->code);
                        return -EINVAL;
                }
        }

        /* now all pseudo BPF_LD_IMM64 instructions load valid
         * 'struct bpf_map *' into a register instead of user map_fd.
         * These pointers will be used later by verifier to validate map access.
         */
        return 0;
}

/* drop refcnt of maps used by the rejected program */
static void release_maps(struct bpf_verifier_env *env)
{
        __bpf_free_used_maps(env->prog->aux, env->used_maps,
                             env->used_map_cnt);
}

/* drop refcnt of maps used by the rejected program */
static void release_btfs(struct bpf_verifier_env *env)
{
        __bpf_free_used_btfs(env->prog->aux, env->used_btfs,
                             env->used_btf_cnt);
}

/* convert pseudo BPF_LD_IMM64 into generic BPF_LD_IMM64 */
static void convert_pseudo_ld_imm64(struct bpf_verifier_env *env)
{
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int i;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (insn->code != (BPF_LD | BPF_IMM | BPF_DW))
                        continue;
                if (insn->src_reg == BPF_PSEUDO_FUNC)
                        continue;
                insn->src_reg = 0;
        }
}

/* single env->prog->insni[off] instruction was replaced with the range
 * insni[off, off + cnt).  Adjust corresponding insn_aux_data by copying
 * [0, off) and [off, end) to new locations, so the patched range stays zero
 */
static int adjust_insn_aux_data(struct bpf_verifier_env *env,
                                struct bpf_prog *new_prog, u32 off, u32 cnt)
{
        struct bpf_insn_aux_data *new_data, *old_data = env->insn_aux_data;
        struct bpf_insn *insn = new_prog->insnsi;
        u32 prog_len;
        int i;

        /* aux info at OFF always needs adjustment, no matter fast path
         * (cnt == 1) is taken or not. There is no guarantee INSN at OFF is the
         * original insn at old prog.
         */
        old_data[off].zext_dst = insn_has_def32(env, insn + off + cnt - 1);

        if (cnt == 1)
                return 0;
        prog_len = new_prog->len;
        new_data = vzalloc(array_size(prog_len,
                                      sizeof(struct bpf_insn_aux_data)));
        if (!new_data)
                return -ENOMEM;
        memcpy(new_data, old_data, sizeof(struct bpf_insn_aux_data) * off);
        memcpy(new_data + off + cnt - 1, old_data + off,
               sizeof(struct bpf_insn_aux_data) * (prog_len - off - cnt + 1));
        for (i = off; i < off + cnt - 1; i++) {
                new_data[i].seen = env->pass_cnt;
                new_data[i].zext_dst = insn_has_def32(env, insn + i);
        }
        env->insn_aux_data = new_data;
        vfree(old_data);
        return 0;
}

static void adjust_subprog_starts(struct bpf_verifier_env *env, u32 off, u32 len)
{
        int i;

        if (len == 1)
                return;
        /* NOTE: fake 'exit' subprog should be updated as well. */
        for (i = 0; i <= env->subprog_cnt; i++) {
                if (env->subprog_info[i].start <= off)
                        continue;
                env->subprog_info[i].start += len - 1;
        }
}

static void adjust_poke_descs(struct bpf_prog *prog, u32 len)
{
        struct bpf_jit_poke_descriptor *tab = prog->aux->poke_tab;
        int i, sz = prog->aux->size_poke_tab;
        struct bpf_jit_poke_descriptor *desc;

        for (i = 0; i < sz; i++) {
                desc = &tab[i];
                desc->insn_idx += len - 1;
        }
}

static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 off,
                                            const struct bpf_insn *patch, u32 len)
{
        struct bpf_prog *new_prog;

        new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
        if (IS_ERR(new_prog)) {
                if (PTR_ERR(new_prog) == -ERANGE)
                        verbose(env,
                                "insn %d cannot be patched due to 16-bit range\n",
                                env->insn_aux_data[off].orig_idx);
                return NULL;
        }
        if (adjust_insn_aux_data(env, new_prog, off, len))
                return NULL;
        adjust_subprog_starts(env, off, len);
        adjust_poke_descs(new_prog, len);
        return new_prog;
}

static int adjust_subprog_starts_after_remove(struct bpf_verifier_env *env,
                                              u32 off, u32 cnt)
{
        int i, j;

        /* find first prog starting at or after off (first to remove) */
        for (i = 0; i < env->subprog_cnt; i++)
                if (env->subprog_info[i].start >= off)
                        break;
        /* find first prog starting at or after off + cnt (first to stay) */
        for (j = i; j < env->subprog_cnt; j++)
                if (env->subprog_info[j].start >= off + cnt)
                        break;
        /* if j doesn't start exactly at off + cnt, we are just removing
         * the front of previous prog
         */
        if (env->subprog_info[j].start != off + cnt)
                j--;

        if (j > i) {
                struct bpf_prog_aux *aux = env->prog->aux;
                int move;

                /* move fake 'exit' subprog as well */
                move = env->subprog_cnt + 1 - j;

                memmove(env->subprog_info + i,
                        env->subprog_info + j,
                        sizeof(*env->subprog_info) * move);
                env->subprog_cnt -= j - i;

                /* remove func_info */
                if (aux->func_info) {
                        move = aux->func_info_cnt - j;

                        memmove(aux->func_info + i,
                                aux->func_info + j,
                                sizeof(*aux->func_info) * move);
                        aux->func_info_cnt -= j - i;
                        /* func_info->insn_off is set after all code rewrites,
                         * in adjust_btf_func() - no need to adjust
                         */
                }
        } else {
                /* convert i from "first prog to remove" to "first to adjust" */
                if (env->subprog_info[i].start == off)
                        i++;
        }

        /* update fake 'exit' subprog as well */
        for (; i <= env->subprog_cnt; i++)
                env->subprog_info[i].start -= cnt;

        return 0;
}

static int bpf_adj_linfo_after_remove(struct bpf_verifier_env *env, u32 off,
                                      u32 cnt)
{
        struct bpf_prog *prog = env->prog;
        u32 i, l_off, l_cnt, nr_linfo;
        struct bpf_line_info *linfo;

        nr_linfo = prog->aux->nr_linfo;
        if (!nr_linfo)
                return 0;

        linfo = prog->aux->linfo;

        /* find first line info to remove, count lines to be removed */
        for (i = 0; i < nr_linfo; i++)
                if (linfo[i].insn_off >= off)
                        break;

        l_off = i;
        l_cnt = 0;
        for (; i < nr_linfo; i++)
                if (linfo[i].insn_off < off + cnt)
                        l_cnt++;
                else
                        break;

        /* First live insn doesn't match first live linfo, it needs to "inherit"
         * last removed linfo.  prog is already modified, so prog->len == off
         * means no live instructions after (tail of the program was removed).
         */
        if (prog->len != off && l_cnt &&
            (i == nr_linfo || linfo[i].insn_off != off + cnt)) {
                l_cnt--;
                linfo[--i].insn_off = off + cnt;
        }

        /* remove the line info which refer to the removed instructions */
        if (l_cnt) {
                memmove(linfo + l_off, linfo + i,
                        sizeof(*linfo) * (nr_linfo - i));

                prog->aux->nr_linfo -= l_cnt;
                nr_linfo = prog->aux->nr_linfo;
        }

        /* pull all linfo[i].insn_off >= off + cnt in by cnt */
        for (i = l_off; i < nr_linfo; i++)
                linfo[i].insn_off -= cnt;

        /* fix up all subprogs (incl. 'exit') which start >= off */
        for (i = 0; i <= env->subprog_cnt; i++)
                if (env->subprog_info[i].linfo_idx > l_off) {
                        /* program may have started in the removed region but
                         * may not be fully removed
                         */
                        if (env->subprog_info[i].linfo_idx >= l_off + l_cnt)
                                env->subprog_info[i].linfo_idx -= l_cnt;
                        else
                                env->subprog_info[i].linfo_idx = l_off;
                }

        return 0;
}

static int verifier_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt)
{
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        unsigned int orig_prog_len = env->prog->len;
        int err;

        if (bpf_prog_is_dev_bound(env->prog->aux))
                bpf_prog_offload_remove_insns(env, off, cnt);

        err = bpf_remove_insns(env->prog, off, cnt);
        if (err)
                return err;

        err = adjust_subprog_starts_after_remove(env, off, cnt);
        if (err)
                return err;

        err = bpf_adj_linfo_after_remove(env, off, cnt);
        if (err)
                return err;

        memmove(aux_data + off, aux_data + off + cnt,
                sizeof(*aux_data) * (orig_prog_len - off - cnt));

        return 0;
}

/* The verifier does more data flow analysis than llvm and will not
 * explore branches that are dead at run time. Malicious programs can
 * have dead code too. Therefore replace all dead at-run-time code
 * with 'ja -1'.
 *
 * Just nops are not optimal, e.g. if they would sit at the end of the
 * program and through another bug we would manage to jump there, then
 * we'd execute beyond program memory otherwise. Returning exception
 * code also wouldn't work since we can have subprogs where the dead
 * code could be located.
 */
static void sanitize_dead_code(struct bpf_verifier_env *env)
{
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        struct bpf_insn trap = BPF_JMP_IMM(BPF_JA, 0, 0, -1);
        struct bpf_insn *insn = env->prog->insnsi;
        const int insn_cnt = env->prog->len;
        int i;

        for (i = 0; i < insn_cnt; i++) {
                if (aux_data[i].seen)
                        continue;
                memcpy(insn + i, &trap, sizeof(trap));
        }
}

static bool insn_is_cond_jump(u8 code)
{
        u8 op;

        if (BPF_CLASS(code) == BPF_JMP32)
                return true;

        if (BPF_CLASS(code) != BPF_JMP)
                return false;

        op = BPF_OP(code);
        return op != BPF_JA && op != BPF_EXIT && op != BPF_CALL;
}

static void opt_hard_wire_dead_code_branches(struct bpf_verifier_env *env)
{
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
        struct bpf_insn *insn = env->prog->insnsi;
        const int insn_cnt = env->prog->len;
        int i;

        for (i = 0; i < insn_cnt; i++, insn++) {
                if (!insn_is_cond_jump(insn->code))
                        continue;

                if (!aux_data[i + 1].seen)
                        ja.off = insn->off;
                else if (!aux_data[i + 1 + insn->off].seen)
                        ja.off = 0;
                else
                        continue;

                if (bpf_prog_is_dev_bound(env->prog->aux))
                        bpf_prog_offload_replace_insn(env, i, &ja);

                memcpy(insn, &ja, sizeof(ja));
        }
}

static int opt_remove_dead_code(struct bpf_verifier_env *env)
{
        struct bpf_insn_aux_data *aux_data = env->insn_aux_data;
        int insn_cnt = env->prog->len;
        int i, err;

        for (i = 0; i < insn_cnt; i++) {
                int j;

                j = 0;
                while (i + j < insn_cnt && !aux_data[i + j].seen)
                        j++;
                if (!j)
                        continue;

                err = verifier_remove_insns(env, i, j);
                if (err)
                        return err;
                insn_cnt = env->prog->len;
        }

        return 0;
}

static int opt_remove_nops(struct bpf_verifier_env *env)
{
        const struct bpf_insn ja = BPF_JMP_IMM(BPF_JA, 0, 0, 0);
        struct bpf_insn *insn = env->prog->insnsi;
        int insn_cnt = env->prog->len;
        int i, err;

        for (i = 0; i < insn_cnt; i++) {
                if (memcmp(&insn[i], &ja, sizeof(ja)))
                        continue;

                err = verifier_remove_insns(env, i, 1);
                if (err)
                        return err;
                insn_cnt--;
                i--;
        }

        return 0;
}

static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
                                         const union bpf_attr *attr)
{
        struct bpf_insn *patch, zext_patch[2], rnd_hi32_patch[4];
        struct bpf_insn_aux_data *aux = env->insn_aux_data;
        int i, patch_len, delta = 0, len = env->prog->len;
        struct bpf_insn *insns = env->prog->insnsi;
        struct bpf_prog *new_prog;
        bool rnd_hi32;

        rnd_hi32 = attr->prog_flags & BPF_F_TEST_RND_HI32;
        zext_patch[1] = BPF_ZEXT_REG(0);
        rnd_hi32_patch[1] = BPF_ALU64_IMM(BPF_MOV, BPF_REG_AX, 0);
        rnd_hi32_patch[2] = BPF_ALU64_IMM(BPF_LSH, BPF_REG_AX, 32);
        rnd_hi32_patch[3] = BPF_ALU64_REG(BPF_OR, 0, BPF_REG_AX);
        for (i = 0; i < len; i++) {
                int adj_idx = i + delta;
                struct bpf_insn insn;
                int load_reg;

                insn = insns[adj_idx];
                load_reg = insn_def_regno(&insn);
                if (!aux[adj_idx].zext_dst) {
                        u8 code, class;
                        u32 imm_rnd;

                        if (!rnd_hi32)
                                continue;

                        code = insn.code;
                        class = BPF_CLASS(code);
                        if (load_reg == -1)
                                continue;

                        /* NOTE: arg "reg" (the fourth one) is only used for
                         *       BPF_STX + SRC_OP, so it is safe to pass NULL
                         *       here.
                         */
                        if (is_reg64(env, &insn, load_reg, NULL, DST_OP)) {
                                if (class == BPF_LD &&
                                    BPF_MODE(code) == BPF_IMM)
                                        i++;
                                continue;
                        }

                        /* ctx load could be transformed into wider load. */
                        if (class == BPF_LDX &&
                            aux[adj_idx].ptr_type == PTR_TO_CTX)
                                continue;

                        imm_rnd = get_random_int();
                        rnd_hi32_patch[0] = insn;
                        rnd_hi32_patch[1].imm = imm_rnd;
                        rnd_hi32_patch[3].dst_reg = load_reg;
                        patch = rnd_hi32_patch;
                        patch_len = 4;
                        goto apply_patch_buffer;
                }

                /* Add in an zero-extend instruction if a) the JIT has requested
                 * it or b) it's a CMPXCHG.
                 *
                 * The latter is because: BPF_CMPXCHG always loads a value into
                 * R0, therefore always zero-extends. However some archs'
                 * equivalent instruction only does this load when the
                 * comparison is successful. This detail of CMPXCHG is
                 * orthogonal to the general zero-extension behaviour of the
                 * CPU, so it's treated independently of bpf_jit_needs_zext.
                 */
                if (!bpf_jit_needs_zext() && !is_cmpxchg_insn(&insn))
                        continue;

                if (WARN_ON(load_reg == -1)) {
                        verbose(env, "verifier bug. zext_dst is set, but no reg is defined\n");
                        return -EFAULT;
                }

                zext_patch[0] = insn;
                zext_patch[1].dst_reg = load_reg;
                zext_patch[1].src_reg = load_reg;
                patch = zext_patch;
                patch_len = 2;
apply_patch_buffer:
                new_prog = bpf_patch_insn_data(env, adj_idx, patch, patch_len);
                if (!new_prog)
                        return -ENOMEM;
                env->prog = new_prog;
                insns = new_prog->insnsi;
                aux = env->insn_aux_data;
                delta += patch_len - 1;
        }

        return 0;
}

/* convert load instructions that access fields of a context type into a
 * sequence of instructions that access fields of the underlying structure:
 *     struct __sk_buff    -> struct sk_buff
 *     struct bpf_sock_ops -> struct sock
 */
static int convert_ctx_accesses(struct bpf_verifier_env *env)
{
        const struct bpf_verifier_ops *ops = env->ops;
        int i, cnt, size, ctx_field_size, delta = 0;
        const int insn_cnt = env->prog->len;
        struct bpf_insn insn_buf[16], *insn;
        u32 target_size, size_default, off;
        struct bpf_prog *new_prog;
        enum bpf_access_type type;
        bool is_narrower_load;

        if (ops->gen_prologue || env->seen_direct_write) {
                if (!ops->gen_prologue) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                }
                cnt = ops->gen_prologue(insn_buf, env->seen_direct_write,
                                        env->prog);
                if (cnt >= ARRAY_SIZE(insn_buf)) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                } else if (cnt) {
                        new_prog = bpf_patch_insn_data(env, 0, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        env->prog = new_prog;
                        delta += cnt - 1;
                }
        }

        if (bpf_prog_is_dev_bound(env->prog->aux))
                return 0;

        insn = env->prog->insnsi + delta;

        for (i = 0; i < insn_cnt; i++, insn++) {
                bpf_convert_ctx_access_t convert_ctx_access;

                if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
                    insn->code == (BPF_LDX | BPF_MEM | BPF_DW))
                        type = BPF_READ;
                else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_W) ||
                         insn->code == (BPF_STX | BPF_MEM | BPF_DW))
                        type = BPF_WRITE;
                else
                        continue;

                if (type == BPF_WRITE &&
                    env->insn_aux_data[i + delta].sanitize_stack_off) {
                        struct bpf_insn patch[] = {
                                /* Sanitize suspicious stack slot with zero.
                                 * There are no memory dependencies for this store,
                                 * since it's only using frame pointer and immediate
                                 * constant of zero
                                 */
                                BPF_ST_MEM(BPF_DW, BPF_REG_FP,
                                           env->insn_aux_data[i + delta].sanitize_stack_off,
                                           0),
                                /* the original STX instruction will immediately
                                 * overwrite the same stack slot with appropriate value
                                 */
                                *insn,
                        };

                        cnt = ARRAY_SIZE(patch);
                        new_prog = bpf_patch_insn_data(env, i + delta, patch, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                switch (env->insn_aux_data[i + delta].ptr_type) {
                case PTR_TO_CTX:
                        if (!ops->convert_ctx_access)
                                continue;
                        convert_ctx_access = ops->convert_ctx_access;
                        break;
                case PTR_TO_SOCKET:
                case PTR_TO_SOCK_COMMON:
                        convert_ctx_access = bpf_sock_convert_ctx_access;
                        break;
                case PTR_TO_TCP_SOCK:
                        convert_ctx_access = bpf_tcp_sock_convert_ctx_access;
                        break;
                case PTR_TO_XDP_SOCK:
                        convert_ctx_access = bpf_xdp_sock_convert_ctx_access;
                        break;
                case PTR_TO_BTF_ID:
                        if (type == BPF_READ) {
                                insn->code = BPF_LDX | BPF_PROBE_MEM |
                                        BPF_SIZE((insn)->code);
                                env->prog->aux->num_exentries++;
                        } else if (resolve_prog_type(env->prog) != BPF_PROG_TYPE_STRUCT_OPS) {
                                verbose(env, "Writes through BTF pointers are not allowed\n");
                                return -EINVAL;
                        }
                        continue;
                default:
                        continue;
                }

                ctx_field_size = env->insn_aux_data[i + delta].ctx_field_size;
                size = BPF_LDST_BYTES(insn);

                /* If the read access is a narrower load of the field,
                 * convert to a 4/8-byte load, to minimum program type specific
                 * convert_ctx_access changes. If conversion is successful,
                 * we will apply proper mask to the result.
                 */
                is_narrower_load = size < ctx_field_size;
                size_default = bpf_ctx_off_adjust_machine(ctx_field_size);
                off = insn->off;
                if (is_narrower_load) {
                        u8 size_code;

                        if (type == BPF_WRITE) {
                                verbose(env, "bpf verifier narrow ctx access misconfigured\n");
                                return -EINVAL;
                        }

                        size_code = BPF_H;
                        if (ctx_field_size == 4)
                                size_code = BPF_W;
                        else if (ctx_field_size == 8)
                                size_code = BPF_DW;

                        insn->off = off & ~(size_default - 1);
                        insn->code = BPF_LDX | BPF_MEM | size_code;
                }

                target_size = 0;
                cnt = convert_ctx_access(type, insn, insn_buf, env->prog,
                                         &target_size);
                if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf) ||
                    (ctx_field_size && !target_size)) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                }

                if (is_narrower_load && size < target_size) {
                        u8 shift = bpf_ctx_narrow_access_offset(
                                off, size, size_default) * 8;
                        if (ctx_field_size <= 4) {
                                if (shift)
                                        insn_buf[cnt++] = BPF_ALU32_IMM(BPF_RSH,
                                                                        insn->dst_reg,
                                                                        shift);
                                insn_buf[cnt++] = BPF_ALU32_IMM(BPF_AND, insn->dst_reg,
                                                                (1 << size * 8) - 1);
                        } else {
                                if (shift)
                                        insn_buf[cnt++] = BPF_ALU64_IMM(BPF_RSH,
                                                                        insn->dst_reg,
                                                                        shift);
                                insn_buf[cnt++] = BPF_ALU64_IMM(BPF_AND, insn->dst_reg,
                                                                (1ULL << size * 8) - 1);
                        }
                }

                new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                if (!new_prog)
                        return -ENOMEM;

                delta += cnt - 1;

                /* keep walking new program and skip insns we just inserted */
                env->prog = new_prog;
                insn      = new_prog->insnsi + i + delta;
        }

        return 0;
}

static int jit_subprogs(struct bpf_verifier_env *env)
{
        struct bpf_prog *prog = env->prog, **func, *tmp;
        int i, j, subprog_start, subprog_end = 0, len, subprog;
        struct bpf_map *map_ptr;
        struct bpf_insn *insn;
        void *old_bpf_func;
        int err, num_exentries;

        if (env->subprog_cnt <= 1)
                return 0;

        for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
                if (bpf_pseudo_func(insn)) {
                        env->insn_aux_data[i].call_imm = insn->imm;
                        /* subprog is encoded in insn[1].imm */
                        continue;
                }

                if (!bpf_pseudo_call(insn))
                        continue;
                /* Upon error here we cannot fall back to interpreter but
                 * need a hard reject of the program. Thus -EFAULT is
                 * propagated in any case.
                 */
                subprog = find_subprog(env, i + insn->imm + 1);
                if (subprog < 0) {
                        WARN_ONCE(1, "verifier bug. No program starts at insn %d\n",
                                  i + insn->imm + 1);
                        return -EFAULT;
                }
                /* temporarily remember subprog id inside insn instead of
                 * aux_data, since next loop will split up all insns into funcs
                 */
                insn->off = subprog;
                /* remember original imm in case JIT fails and fallback
                 * to interpreter will be needed
                 */
                env->insn_aux_data[i].call_imm = insn->imm;
                /* point imm to __bpf_call_base+1 from JITs point of view */
                insn->imm = 1;
        }

        err = bpf_prog_alloc_jited_linfo(prog);
        if (err)
                goto out_undo_insn;

        err = -ENOMEM;
        func = kcalloc(env->subprog_cnt, sizeof(prog), GFP_KERNEL);
        if (!func)
                goto out_undo_insn;

        for (i = 0; i < env->subprog_cnt; i++) {
                subprog_start = subprog_end;
                subprog_end = env->subprog_info[i + 1].start;

                len = subprog_end - subprog_start;
                /* BPF_PROG_RUN doesn't call subprogs directly,
                 * hence main prog stats include the runtime of subprogs.
                 * subprogs don't have IDs and not reachable via prog_get_next_id
                 * func[i]->stats will never be accessed and stays NULL
                 */
                func[i] = bpf_prog_alloc_no_stats(bpf_prog_size(len), GFP_USER);
                if (!func[i])
                        goto out_free;
                memcpy(func[i]->insnsi, &prog->insnsi[subprog_start],
                       len * sizeof(struct bpf_insn));
                func[i]->type = prog->type;
                func[i]->len = len;
                if (bpf_prog_calc_tag(func[i]))
                        goto out_free;
                func[i]->is_func = 1;
                func[i]->aux->func_idx = i;
                /* the btf and func_info will be freed only at prog->aux */
                func[i]->aux->btf = prog->aux->btf;
                func[i]->aux->func_info = prog->aux->func_info;

                for (j = 0; j < prog->aux->size_poke_tab; j++) {
                        u32 insn_idx = prog->aux->poke_tab[j].insn_idx;
                        int ret;

                        if (!(insn_idx >= subprog_start &&
                              insn_idx <= subprog_end))
                                continue;

                        ret = bpf_jit_add_poke_descriptor(func[i],
                                                          &prog->aux->poke_tab[j]);
                        if (ret < 0) {
                                verbose(env, "adding tail call poke descriptor failed\n");
                                goto out_free;
                        }

                        func[i]->insnsi[insn_idx - subprog_start].imm = ret + 1;

                        map_ptr = func[i]->aux->poke_tab[ret].tail_call.map;
                        ret = map_ptr->ops->map_poke_track(map_ptr, func[i]->aux);
                        if (ret < 0) {
                                verbose(env, "tracking tail call prog failed\n");
                                goto out_free;
                        }
                }

                /* Use bpf_prog_F_tag to indicate functions in stack traces.
                 * Long term would need debug info to populate names
                 */
                func[i]->aux->name[0] = 'F';
                func[i]->aux->stack_depth = env->subprog_info[i].stack_depth;
                func[i]->jit_requested = 1;
                func[i]->aux->linfo = prog->aux->linfo;
                func[i]->aux->nr_linfo = prog->aux->nr_linfo;
                func[i]->aux->jited_linfo = prog->aux->jited_linfo;
                func[i]->aux->linfo_idx = env->subprog_info[i].linfo_idx;
                num_exentries = 0;
                insn = func[i]->insnsi;
                for (j = 0; j < func[i]->len; j++, insn++) {
                        if (BPF_CLASS(insn->code) == BPF_LDX &&
                            BPF_MODE(insn->code) == BPF_PROBE_MEM)
                                num_exentries++;
                }
                func[i]->aux->num_exentries = num_exentries;
                func[i]->aux->tail_call_reachable = env->subprog_info[i].tail_call_reachable;
                func[i] = bpf_int_jit_compile(func[i]);
                if (!func[i]->jited) {
                        err = -ENOTSUPP;
                        goto out_free;
                }
                cond_resched();
        }

        /* Untrack main program's aux structs so that during map_poke_run()
         * we will not stumble upon the unfilled poke descriptors; each
         * of the main program's poke descs got distributed across subprogs
         * and got tracked onto map, so we are sure that none of them will
         * be missed after the operation below
         */
        for (i = 0; i < prog->aux->size_poke_tab; i++) {
                map_ptr = prog->aux->poke_tab[i].tail_call.map;

                map_ptr->ops->map_poke_untrack(map_ptr, prog->aux);
        }

        /* at this point all bpf functions were successfully JITed
         * now populate all bpf_calls with correct addresses and
         * run last pass of JIT
         */
        for (i = 0; i < env->subprog_cnt; i++) {
                insn = func[i]->insnsi;
                for (j = 0; j < func[i]->len; j++, insn++) {
                        if (bpf_pseudo_func(insn)) {
                                subprog = insn[1].imm;
                                insn[0].imm = (u32)(long)func[subprog]->bpf_func;
                                insn[1].imm = ((u64)(long)func[subprog]->bpf_func) >> 32;
                                continue;
                        }
                        if (!bpf_pseudo_call(insn))
                                continue;
                        subprog = insn->off;
                        insn->imm = BPF_CAST_CALL(func[subprog]->bpf_func) -
                                    __bpf_call_base;
                }

                /* we use the aux data to keep a list of the start addresses
                 * of the JITed images for each function in the program
                 *
                 * for some architectures, such as powerpc64, the imm field
                 * might not be large enough to hold the offset of the start
                 * address of the callee's JITed image from __bpf_call_base
                 *
                 * in such cases, we can lookup the start address of a callee
                 * by using its subprog id, available from the off field of
                 * the call instruction, as an index for this list
                 */
                func[i]->aux->func = func;
                func[i]->aux->func_cnt = env->subprog_cnt;
        }
        for (i = 0; i < env->subprog_cnt; i++) {
                old_bpf_func = func[i]->bpf_func;
                tmp = bpf_int_jit_compile(func[i]);
                if (tmp != func[i] || func[i]->bpf_func != old_bpf_func) {
                        verbose(env, "JIT doesn't support bpf-to-bpf calls\n");
                        err = -ENOTSUPP;
                        goto out_free;
                }
                cond_resched();
        }

        /* finally lock prog and jit images for all functions and
         * populate kallsysm
         */
        for (i = 0; i < env->subprog_cnt; i++) {
                bpf_prog_lock_ro(func[i]);
                bpf_prog_kallsyms_add(func[i]);
        }

        /* Last step: make now unused interpreter insns from main
         * prog consistent for later dump requests, so they can
         * later look the same as if they were interpreted only.
         */
        for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
                if (bpf_pseudo_func(insn)) {
                        insn[0].imm = env->insn_aux_data[i].call_imm;
                        insn[1].imm = find_subprog(env, i + insn[0].imm + 1);
                        continue;
                }
                if (!bpf_pseudo_call(insn))
                        continue;
                insn->off = env->insn_aux_data[i].call_imm;
                subprog = find_subprog(env, i + insn->off + 1);
                insn->imm = subprog;
        }

        prog->jited = 1;
        prog->bpf_func = func[0]->bpf_func;
        prog->aux->func = func;
        prog->aux->func_cnt = env->subprog_cnt;
        bpf_prog_free_unused_jited_linfo(prog);
        return 0;
out_free:
        for (i = 0; i < env->subprog_cnt; i++) {
                if (!func[i])
                        continue;

                for (j = 0; j < func[i]->aux->size_poke_tab; j++) {
                        map_ptr = func[i]->aux->poke_tab[j].tail_call.map;
                        map_ptr->ops->map_poke_untrack(map_ptr, func[i]->aux);
                }
                bpf_jit_free(func[i]);
        }
        kfree(func);
out_undo_insn:
        /* cleanup main prog to be interpreted */
        prog->jit_requested = 0;
        for (i = 0, insn = prog->insnsi; i < prog->len; i++, insn++) {
                if (!bpf_pseudo_call(insn))
                        continue;
                insn->off = 0;
                insn->imm = env->insn_aux_data[i].call_imm;
        }
        bpf_prog_free_jited_linfo(prog);
        return err;
}

static int fixup_call_args(struct bpf_verifier_env *env)
{
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
        struct bpf_prog *prog = env->prog;
        struct bpf_insn *insn = prog->insnsi;
        int i, depth;
#endif
        int err = 0;

        if (env->prog->jit_requested &&
            !bpf_prog_is_dev_bound(env->prog->aux)) {
                err = jit_subprogs(env);
                if (err == 0)
                        return 0;
                if (err == -EFAULT)
                        return err;
        }
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
        if (env->subprog_cnt > 1 && env->prog->aux->tail_call_reachable) {
                /* When JIT fails the progs with bpf2bpf calls and tail_calls
                 * have to be rejected, since interpreter doesn't support them yet.
                 */
                verbose(env, "tail_calls are not allowed in non-JITed programs with bpf-to-bpf calls\n");
                return -EINVAL;
        }
        for (i = 0; i < prog->len; i++, insn++) {
                if (bpf_pseudo_func(insn)) {
                        /* When JIT fails the progs with callback calls
                         * have to be rejected, since interpreter doesn't support them yet.
                         */
                        verbose(env, "callbacks are not allowed in non-JITed programs\n");
                        return -EINVAL;
                }

                if (!bpf_pseudo_call(insn))
                        continue;
                depth = get_callee_stack_depth(env, insn, i);
                if (depth < 0)
                        return depth;
                bpf_patch_call_args(insn, depth);
        }
        err = 0;
#endif
        return err;
}

/* Do various post-verification rewrites in a single program pass.
 * These rewrites simplify JIT and interpreter implementations.
 */
static int do_misc_fixups(struct bpf_verifier_env *env)
{
        struct bpf_prog *prog = env->prog;
        bool expect_blinding = bpf_jit_blinding_enabled(prog);
        struct bpf_insn *insn = prog->insnsi;
        const struct bpf_func_proto *fn;
        const int insn_cnt = prog->len;
        const struct bpf_map_ops *ops;
        struct bpf_insn_aux_data *aux;
        struct bpf_insn insn_buf[16];
        struct bpf_prog *new_prog;
        struct bpf_map *map_ptr;
        int i, ret, cnt, delta = 0;

        for (i = 0; i < insn_cnt; i++, insn++) {
                /* Make divide-by-zero exceptions impossible. */
                if (insn->code == (BPF_ALU64 | BPF_MOD | BPF_X) ||
                    insn->code == (BPF_ALU64 | BPF_DIV | BPF_X) ||
                    insn->code == (BPF_ALU | BPF_MOD | BPF_X) ||
                    insn->code == (BPF_ALU | BPF_DIV | BPF_X)) {
                        bool is64 = BPF_CLASS(insn->code) == BPF_ALU64;
                        bool isdiv = BPF_OP(insn->code) == BPF_DIV;
                        struct bpf_insn *patchlet;
                        struct bpf_insn chk_and_div[] = {
                                /* [R,W]x div 0 -> 0 */
                                BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
                                             BPF_JNE | BPF_K, insn->src_reg,
                                             0, 2, 0),
                                BPF_ALU32_REG(BPF_XOR, insn->dst_reg, insn->dst_reg),
                                BPF_JMP_IMM(BPF_JA, 0, 0, 1),
                                *insn,
                        };
                        struct bpf_insn chk_and_mod[] = {
                                /* [R,W]x mod 0 -> [R,W]x */
                                BPF_RAW_INSN((is64 ? BPF_JMP : BPF_JMP32) |
                                             BPF_JEQ | BPF_K, insn->src_reg,
                                             0, 1 + (is64 ? 0 : 1), 0),
                                *insn,
                                BPF_JMP_IMM(BPF_JA, 0, 0, 1),
                                BPF_MOV32_REG(insn->dst_reg, insn->dst_reg),
                        };

                        patchlet = isdiv ? chk_and_div : chk_and_mod;
                        cnt = isdiv ? ARRAY_SIZE(chk_and_div) :
                                      ARRAY_SIZE(chk_and_mod) - (is64 ? 2 : 0);

                        new_prog = bpf_patch_insn_data(env, i + delta, patchlet, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                /* Implement LD_ABS and LD_IND with a rewrite, if supported by the program type. */
                if (BPF_CLASS(insn->code) == BPF_LD &&
                    (BPF_MODE(insn->code) == BPF_ABS ||
                     BPF_MODE(insn->code) == BPF_IND)) {
                        cnt = env->ops->gen_ld_abs(insn, insn_buf);
                        if (cnt == 0 || cnt >= ARRAY_SIZE(insn_buf)) {
                                verbose(env, "bpf verifier is misconfigured\n");
                                return -EINVAL;
                        }

                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                /* Rewrite pointer arithmetic to mitigate speculation attacks. */
                if (insn->code == (BPF_ALU64 | BPF_ADD | BPF_X) ||
                    insn->code == (BPF_ALU64 | BPF_SUB | BPF_X)) {
                        const u8 code_add = BPF_ALU64 | BPF_ADD | BPF_X;
                        const u8 code_sub = BPF_ALU64 | BPF_SUB | BPF_X;
                        struct bpf_insn insn_buf[16];
                        struct bpf_insn *patch = &insn_buf[0];
                        bool issrc, isneg;
                        u32 off_reg;

                        aux = &env->insn_aux_data[i + delta];
                        if (!aux->alu_state ||
                            aux->alu_state == BPF_ALU_NON_POINTER)
                                continue;

                        isneg = aux->alu_state & BPF_ALU_NEG_VALUE;
                        issrc = (aux->alu_state & BPF_ALU_SANITIZE) ==
                                BPF_ALU_SANITIZE_SRC;

                        off_reg = issrc ? insn->src_reg : insn->dst_reg;
                        if (isneg)
                                *patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
                        *patch++ = BPF_MOV32_IMM(BPF_REG_AX, aux->alu_limit - 1);
                        *patch++ = BPF_ALU64_REG(BPF_SUB, BPF_REG_AX, off_reg);
                        *patch++ = BPF_ALU64_REG(BPF_OR, BPF_REG_AX, off_reg);
                        *patch++ = BPF_ALU64_IMM(BPF_NEG, BPF_REG_AX, 0);
                        *patch++ = BPF_ALU64_IMM(BPF_ARSH, BPF_REG_AX, 63);
                        if (issrc) {
                                *patch++ = BPF_ALU64_REG(BPF_AND, BPF_REG_AX,
                                                         off_reg);
                                insn->src_reg = BPF_REG_AX;
                        } else {
                                *patch++ = BPF_ALU64_REG(BPF_AND, off_reg,
                                                         BPF_REG_AX);
                        }
                        if (isneg)
                                insn->code = insn->code == code_add ?
                                             code_sub : code_add;
                        *patch++ = *insn;
                        if (issrc && isneg)
                                *patch++ = BPF_ALU64_IMM(BPF_MUL, off_reg, -1);
                        cnt = patch - insn_buf;

                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                if (insn->code != (BPF_JMP | BPF_CALL))
                        continue;
                if (insn->src_reg == BPF_PSEUDO_CALL)
                        continue;

                if (insn->imm == BPF_FUNC_get_route_realm)
                        prog->dst_needed = 1;
                if (insn->imm == BPF_FUNC_get_prandom_u32)
                        bpf_user_rnd_init_once();
                if (insn->imm == BPF_FUNC_override_return)
                        prog->kprobe_override = 1;
                if (insn->imm == BPF_FUNC_tail_call) {
                        /* If we tail call into other programs, we
                         * cannot make any assumptions since they can
                         * be replaced dynamically during runtime in
                         * the program array.
                         */
                        prog->cb_access = 1;
                        if (!allow_tail_call_in_subprogs(env))
                                prog->aux->stack_depth = MAX_BPF_STACK;
                        prog->aux->max_pkt_offset = MAX_PACKET_OFF;

                        /* mark bpf_tail_call as different opcode to avoid
                         * conditional branch in the interpeter for every normal
                         * call and to prevent accidental JITing by JIT compiler
                         * that doesn't support bpf_tail_call yet
                         */
                        insn->imm = 0;
                        insn->code = BPF_JMP | BPF_TAIL_CALL;

                        aux = &env->insn_aux_data[i + delta];
                        if (env->bpf_capable && !expect_blinding &&
                            prog->jit_requested &&
                            !bpf_map_key_poisoned(aux) &&
                            !bpf_map_ptr_poisoned(aux) &&
                            !bpf_map_ptr_unpriv(aux)) {
                                struct bpf_jit_poke_descriptor desc = {
                                        .reason = BPF_POKE_REASON_TAIL_CALL,
                                        .tail_call.map = BPF_MAP_PTR(aux->map_ptr_state),
                                        .tail_call.key = bpf_map_key_immediate(aux),
                                        .insn_idx = i + delta,
                                };

                                ret = bpf_jit_add_poke_descriptor(prog, &desc);
                                if (ret < 0) {
                                        verbose(env, "adding tail call poke descriptor failed\n");
                                        return ret;
                                }

                                insn->imm = ret + 1;
                                continue;
                        }

                        if (!bpf_map_ptr_unpriv(aux))
                                continue;

                        /* instead of changing every JIT dealing with tail_call
                         * emit two extra insns:
                         * if (index >= max_entries) goto out;
                         * index &= array->index_mask;
                         * to avoid out-of-bounds cpu speculation
                         */
                        if (bpf_map_ptr_poisoned(aux)) {
                                verbose(env, "tail_call abusing map_ptr\n");
                                return -EINVAL;
                        }

                        map_ptr = BPF_MAP_PTR(aux->map_ptr_state);
                        insn_buf[0] = BPF_JMP_IMM(BPF_JGE, BPF_REG_3,
                                                  map_ptr->max_entries, 2);
                        insn_buf[1] = BPF_ALU32_IMM(BPF_AND, BPF_REG_3,
                                                    container_of(map_ptr,
                                                                 struct bpf_array,
                                                                 map)->index_mask);
                        insn_buf[2] = *insn;
                        cnt = 3;
                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

                /* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
                 * and other inlining handlers are currently limited to 64 bit
                 * only.
                 */
                if (prog->jit_requested && BITS_PER_LONG == 64 &&
                    (insn->imm == BPF_FUNC_map_lookup_elem ||
                     insn->imm == BPF_FUNC_map_update_elem ||
                     insn->imm == BPF_FUNC_map_delete_elem ||
                     insn->imm == BPF_FUNC_map_push_elem   ||
                     insn->imm == BPF_FUNC_map_pop_elem    ||
                     insn->imm == BPF_FUNC_map_peek_elem   ||
                     insn->imm == BPF_FUNC_redirect_map)) {
                        aux = &env->insn_aux_data[i + delta];
                        if (bpf_map_ptr_poisoned(aux))
                                goto patch_call_imm;

                        map_ptr = BPF_MAP_PTR(aux->map_ptr_state);
                        ops = map_ptr->ops;
                        if (insn->imm == BPF_FUNC_map_lookup_elem &&
                            ops->map_gen_lookup) {
                                cnt = ops->map_gen_lookup(map_ptr, insn_buf);
                                if (cnt == -EOPNOTSUPP)
                                        goto patch_map_ops_generic;
                                if (cnt <= 0 || cnt >= ARRAY_SIZE(insn_buf)) {
                                        verbose(env, "bpf verifier is misconfigured\n");
                                        return -EINVAL;
                                }

                                new_prog = bpf_patch_insn_data(env, i + delta,
                                                               insn_buf, cnt);
                                if (!new_prog)
                                        return -ENOMEM;

                                delta    += cnt - 1;
                                env->prog = prog = new_prog;
                                insn      = new_prog->insnsi + i + delta;
                                continue;
                        }

                        BUILD_BUG_ON(!__same_type(ops->map_lookup_elem,
                                     (void *(*)(struct bpf_map *map, void *key))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_delete_elem,
                                     (int (*)(struct bpf_map *map, void *key))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_update_elem,
                                     (int (*)(struct bpf_map *map, void *key, void *value,
                                              u64 flags))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_push_elem,
                                     (int (*)(struct bpf_map *map, void *value,
                                              u64 flags))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_pop_elem,
                                     (int (*)(struct bpf_map *map, void *value))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_peek_elem,
                                     (int (*)(struct bpf_map *map, void *value))NULL));
                        BUILD_BUG_ON(!__same_type(ops->map_redirect,
                                     (int (*)(struct bpf_map *map, u32 ifindex, u64 flags))NULL));

patch_map_ops_generic:
                        switch (insn->imm) {
                        case BPF_FUNC_map_lookup_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_lookup_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_map_update_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_update_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_map_delete_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_delete_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_map_push_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_push_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_map_pop_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_pop_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_map_peek_elem:
                                insn->imm = BPF_CAST_CALL(ops->map_peek_elem) -
                                            __bpf_call_base;
                                continue;
                        case BPF_FUNC_redirect_map:
                                insn->imm = BPF_CAST_CALL(ops->map_redirect) -
                                            __bpf_call_base;
                                continue;
                        }

                        goto patch_call_imm;
                }

                /* Implement bpf_jiffies64 inline. */
                if (prog->jit_requested && BITS_PER_LONG == 64 &&
                    insn->imm == BPF_FUNC_jiffies64) {
                        struct bpf_insn ld_jiffies_addr[2] = {
                                BPF_LD_IMM64(BPF_REG_0,
                                             (unsigned long)&jiffies),
                        };

                        insn_buf[0] = ld_jiffies_addr[0];
                        insn_buf[1] = ld_jiffies_addr[1];
                        insn_buf[2] = BPF_LDX_MEM(BPF_DW, BPF_REG_0,
                                                  BPF_REG_0, 0);
                        cnt = 3;

                        new_prog = bpf_patch_insn_data(env, i + delta, insn_buf,
                                                       cnt);
                        if (!new_prog)
                                return -ENOMEM;

                        delta    += cnt - 1;
                        env->prog = prog = new_prog;
                        insn      = new_prog->insnsi + i + delta;
                        continue;
                }

patch_call_imm:
                fn = env->ops->get_func_proto(insn->imm, env->prog);
                /* all functions that have prototype and verifier allowed
                 * programs to call them, must be real in-kernel functions
                 */
                if (!fn->func) {
                        verbose(env,
                                "kernel subsystem misconfigured func %s#%d\n",
                                func_id_name(insn->imm), insn->imm);
                        return -EFAULT;
                }
                insn->imm = fn->func - __bpf_call_base;
        }

        /* Since poke tab is now finalized, publish aux to tracker. */
        for (i = 0; i < prog->aux->size_poke_tab; i++) {
                map_ptr = prog->aux->poke_tab[i].tail_call.map;
                if (!map_ptr->ops->map_poke_track ||
                    !map_ptr->ops->map_poke_untrack ||
                    !map_ptr->ops->map_poke_run) {
                        verbose(env, "bpf verifier is misconfigured\n");
                        return -EINVAL;
                }

                ret = map_ptr->ops->map_poke_track(map_ptr, prog->aux);
                if (ret < 0) {
                        verbose(env, "tracking tail call prog failed\n");
                        return ret;
                }
        }

        return 0;
}

static void free_states(struct bpf_verifier_env *env)
{
        struct bpf_verifier_state_list *sl, *sln;
        int i;

        sl = env->free_list;
        while (sl) {
                sln = sl->next;
                free_verifier_state(&sl->state, false);
                kfree(sl);
                sl = sln;
        }
        env->free_list = NULL;

        if (!env->explored_states)
                return;

        for (i = 0; i < state_htab_size(env); i++) {
                sl = env->explored_states[i];

                while (sl) {
                        sln = sl->next;
                        free_verifier_state(&sl->state, false);
                        kfree(sl);
                        sl = sln;
                }
                env->explored_states[i] = NULL;
        }
}

/* The verifier is using insn_aux_data[] to store temporary data during
 * verification and to store information for passes that run after the
 * verification like dead code sanitization. do_check_common() for subprogram N
 * may analyze many other subprograms. sanitize_insn_aux_data() clears all
 * temporary data after do_check_common() finds that subprogram N cannot be
 * verified independently. pass_cnt counts the number of times
 * do_check_common() was run and insn->aux->seen tells the pass number
 * insn_aux_data was touched. These variables are compared to clear temporary
 * data from failed pass. For testing and experiments do_check_common() can be
 * run multiple times even when prior attempt to verify is unsuccessful.
 */
static void sanitize_insn_aux_data(struct bpf_verifier_env *env)
{
        struct bpf_insn *insn = env->prog->insnsi;
        struct bpf_insn_aux_data *aux;
        int i, class;

        for (i = 0; i < env->prog->len; i++) {
                class = BPF_CLASS(insn[i].code);
                if (class != BPF_LDX && class != BPF_STX)
                        continue;
                aux = &env->insn_aux_data[i];
                if (aux->seen != env->pass_cnt)
                        continue;
                memset(aux, 0, offsetof(typeof(*aux), orig_idx));
        }
}

static int do_check_common(struct bpf_verifier_env *env, int subprog)
{
        bool pop_log = !(env->log.level & BPF_LOG_LEVEL2);
        struct bpf_verifier_state *state;
        struct bpf_reg_state *regs;
        int ret, i;

        env->prev_linfo = NULL;
        env->pass_cnt++;

        state = kzalloc(sizeof(struct bpf_verifier_state), GFP_KERNEL);
        if (!state)
                return -ENOMEM;
        state->curframe = 0;
        state->speculative = false;
        state->branches = 1;
        state->frame[0] = kzalloc(sizeof(struct bpf_func_state), GFP_KERNEL);
        if (!state->frame[0]) {
                kfree(state);
                return -ENOMEM;
        }
        env->cur_state = state;
        init_func_state(env, state->frame[0],
                        BPF_MAIN_FUNC /* callsite */,
                        0 /* frameno */,
                        subprog);

        regs = state->frame[state->curframe]->regs;
        if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) {
                ret = btf_prepare_func_args(env, subprog, regs);
                if (ret)
                        goto out;
                for (i = BPF_REG_1; i <= BPF_REG_5; i++) {
                        if (regs[i].type == PTR_TO_CTX)
                                mark_reg_known_zero(env, regs, i);
                        else if (regs[i].type == SCALAR_VALUE)
                                mark_reg_unknown(env, regs, i);
                        else if (regs[i].type == PTR_TO_MEM_OR_NULL) {
                                const u32 mem_size = regs[i].mem_size;

                                mark_reg_known_zero(env, regs, i);
                                regs[i].mem_size = mem_size;
                                regs[i].id = ++env->id_gen;
                        }
                }
        } else {
                /* 1st arg to a function */
                regs[BPF_REG_1].type = PTR_TO_CTX;
                mark_reg_known_zero(env, regs, BPF_REG_1);
                ret = btf_check_func_arg_match(env, subprog, regs);
                if (ret == -EFAULT)
                        /* unlikely verifier bug. abort.
                         * ret == 0 and ret < 0 are sadly acceptable for
                         * main() function due to backward compatibility.
                         * Like socket filter program may be written as:
                         * int bpf_prog(struct pt_regs *ctx)
                         * and never dereference that ctx in the program.
                         * 'struct pt_regs' is a type mismatch for socket
                         * filter that should be using 'struct __sk_buff'.
                         */
                        goto out;
        }

        ret = do_check(env);
out:
        /* check for NULL is necessary, since cur_state can be freed inside
         * do_check() under memory pressure.
         */
        if (env->cur_state) {
                free_verifier_state(env->cur_state, true);
                env->cur_state = NULL;
        }
        while (!pop_stack(env, NULL, NULL, false));
        if (!ret && pop_log)
                bpf_vlog_reset(&env->log, 0);
        free_states(env);
        if (ret)
                /* clean aux data in case subprog was rejected */
                sanitize_insn_aux_data(env);
        return ret;
}

/* Verify all global functions in a BPF program one by one based on their BTF.
 * All global functions must pass verification. Otherwise the whole program is rejected.
 * Consider:
 * int bar(int);
 * int foo(int f)
 * {
 *    return bar(f);
 * }
 * int bar(int b)
 * {
 *    ...
 * }
 * foo() will be verified first for R1=any_scalar_value. During verification it
 * will be assumed that bar() already verified successfully and call to bar()
 * from foo() will be checked for type match only. Later bar() will be verified
 * independently to check that it's safe for R1=any_scalar_value.
 */
static int do_check_subprogs(struct bpf_verifier_env *env)
{
        struct bpf_prog_aux *aux = env->prog->aux;
        int i, ret;

        if (!aux->func_info)
                return 0;

        for (i = 1; i < env->subprog_cnt; i++) {
                if (aux->func_info_aux[i].linkage != BTF_FUNC_GLOBAL)
                        continue;
                env->insn_idx = env->subprog_info[i].start;
                WARN_ON_ONCE(env->insn_idx == 0);
                ret = do_check_common(env, i);
                if (ret) {
                        return ret;
                } else if (env->log.level & BPF_LOG_LEVEL) {
                        verbose(env,
                                "Func#%d is safe for any args that match its prototype\n",
                                i);
                }
        }
        return 0;
}

static int do_check_main(struct bpf_verifier_env *env)
{
        int ret;

        env->insn_idx = 0;
        ret = do_check_common(env, 0);
        if (!ret)
                env->prog->aux->stack_depth = env->subprog_info[0].stack_depth;
        return ret;
}


static void print_verification_stats(struct bpf_verifier_env *env)
{
        int i;

        if (env->log.level & BPF_LOG_STATS) {
                verbose(env, "verification time %lld usec\n",
                        div_u64(env->verification_time, 1000));
                verbose(env, "stack depth ");
                for (i = 0; i < env->subprog_cnt; i++) {
                        u32 depth = env->subprog_info[i].stack_depth;

                        verbose(env, "%d", depth);
                        if (i + 1 < env->subprog_cnt)
                                verbose(env, "+");
                }
                verbose(env, "\n");
        }
        verbose(env, "processed %d insns (limit %d) max_states_per_insn %d "
                "total_states %d peak_states %d mark_read %d\n",
                env->insn_processed, BPF_COMPLEXITY_LIMIT_INSNS,
                env->max_states_per_insn, env->total_states,
                env->peak_states, env->longest_mark_read_walk);
}

static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
{
        const struct btf_type *t, *func_proto;
        const struct bpf_struct_ops *st_ops;
        const struct btf_member *member;
        struct bpf_prog *prog = env->prog;
        u32 btf_id, member_idx;
        const char *mname;

        btf_id = prog->aux->attach_btf_id;
        st_ops = bpf_struct_ops_find(btf_id);
        if (!st_ops) {
                verbose(env, "attach_btf_id %u is not a supported struct\n",
                        btf_id);
                return -ENOTSUPP;
        }

        t = st_ops->type;
        member_idx = prog->expected_attach_type;
        if (member_idx >= btf_type_vlen(t)) {
                verbose(env, "attach to invalid member idx %u of struct %s\n",
                        member_idx, st_ops->name);
                return -EINVAL;
        }

        member = &btf_type_member(t)[member_idx];
        mname = btf_name_by_offset(btf_vmlinux, member->name_off);
        func_proto = btf_type_resolve_func_ptr(btf_vmlinux, member->type,
                                               NULL);
        if (!func_proto) {
                verbose(env, "attach to invalid member %s(@idx %u) of struct %s\n",
                        mname, member_idx, st_ops->name);
                return -EINVAL;
        }

        if (st_ops->check_member) {
                int err = st_ops->check_member(t, member);

                if (err) {
                        verbose(env, "attach to unsupported member %s of struct %s\n",
                                mname, st_ops->name);
                        return err;
                }
        }

        prog->aux->attach_func_proto = func_proto;
        prog->aux->attach_func_name = mname;
        env->ops = st_ops->verifier_ops;

        return 0;
}
#define SECURITY_PREFIX "security_"

static int check_attach_modify_return(unsigned long addr, const char *func_name)
{
        if (within_error_injection_list(addr) ||
            !strncmp(SECURITY_PREFIX, func_name, sizeof(SECURITY_PREFIX) - 1))
                return 0;

        return -EINVAL;
}

/* list of non-sleepable functions that are otherwise on
 * ALLOW_ERROR_INJECTION list
 */
BTF_SET_START(btf_non_sleepable_error_inject)
/* Three functions below can be called from sleepable and non-sleepable context.
 * Assume non-sleepable from bpf safety point of view.
 */
BTF_ID(func, __add_to_page_cache_locked)
BTF_ID(func, should_fail_alloc_page)
BTF_ID(func, should_failslab)
BTF_SET_END(btf_non_sleepable_error_inject)

static int check_non_sleepable_error_inject(u32 btf_id)
{
        return btf_id_set_contains(&btf_non_sleepable_error_inject, btf_id);
}

int bpf_check_attach_target(struct bpf_verifier_log *log,
                            const struct bpf_prog *prog,
                            const struct bpf_prog *tgt_prog,
                            u32 btf_id,
                            struct bpf_attach_target_info *tgt_info)
{
        bool prog_extension = prog->type == BPF_PROG_TYPE_EXT;
        const char prefix[] = "btf_trace_";
        int ret = 0, subprog = -1, i;
        const struct btf_type *t;
        bool conservative = true;
        const char *tname;
        struct btf *btf;
        long addr = 0;

        if (!btf_id) {
                bpf_log(log, "Tracing programs must provide btf_id\n");
                return -EINVAL;
        }
        btf = tgt_prog ? tgt_prog->aux->btf : prog->aux->attach_btf;
        if (!btf) {
                bpf_log(log,
                        "FENTRY/FEXIT program can only be attached to another program annotated with BTF\n");
                return -EINVAL;
        }
        t = btf_type_by_id(btf, btf_id);
        if (!t) {
                bpf_log(log, "attach_btf_id %u is invalid\n", btf_id);
                return -EINVAL;
        }
        tname = btf_name_by_offset(btf, t->name_off);
        if (!tname) {
                bpf_log(log, "attach_btf_id %u doesn't have a name\n", btf_id);
                return -EINVAL;
        }
        if (tgt_prog) {
                struct bpf_prog_aux *aux = tgt_prog->aux;

                for (i = 0; i < aux->func_info_cnt; i++)
                        if (aux->func_info[i].type_id == btf_id) {
                                subprog = i;
                                break;
                        }
                if (subprog == -1) {
                        bpf_log(log, "Subprog %s doesn't exist\n", tname);
                        return -EINVAL;
                }
                conservative = aux->func_info_aux[subprog].unreliable;
                if (prog_extension) {
                        if (conservative) {
                                bpf_log(log,
                                        "Cannot replace static functions\n");
                                return -EINVAL;
                        }
                        if (!prog->jit_requested) {
                                bpf_log(log,
                                        "Extension programs should be JITed\n");
                                return -EINVAL;
                        }
                }
                if (!tgt_prog->jited) {
                        bpf_log(log, "Can attach to only JITed progs\n");
                        return -EINVAL;
                }
                if (tgt_prog->type == prog->type) {
                        /* Cannot fentry/fexit another fentry/fexit program.
                         * Cannot attach program extension to another extension.
                         * It's ok to attach fentry/fexit to extension program.
                         */
                        bpf_log(log, "Cannot recursively attach\n");
                        return -EINVAL;
                }
                if (tgt_prog->type == BPF_PROG_TYPE_TRACING &&
                    prog_extension &&
                    (tgt_prog->expected_attach_type == BPF_TRACE_FENTRY ||
                     tgt_prog->expected_attach_type == BPF_TRACE_FEXIT)) {
                        /* Program extensions can extend all program types
                         * except fentry/fexit. The reason is the following.
                         * The fentry/fexit programs are used for performance
                         * analysis, stats and can be attached to any program
                         * type except themselves. When extension program is
                         * replacing XDP function it is necessary to allow
                         * performance analysis of all functions. Both original
                         * XDP program and its program extension. Hence
                         * attaching fentry/fexit to BPF_PROG_TYPE_EXT is
                         * allowed. If extending of fentry/fexit was allowed it
                         * would be possible to create long call chain
                         * fentry->extension->fentry->extension beyond
                         * reasonable stack size. Hence extending fentry is not
                         * allowed.
                         */
                        bpf_log(log, "Cannot extend fentry/fexit\n");
                        return -EINVAL;
                }
        } else {
                if (prog_extension) {
                        bpf_log(log, "Cannot replace kernel functions\n");
                        return -EINVAL;
                }
        }

        switch (prog->expected_attach_type) {
        case BPF_TRACE_RAW_TP:
                if (tgt_prog) {
                        bpf_log(log,
                                "Only FENTRY/FEXIT progs are attachable to another BPF prog\n");
                        return -EINVAL;
                }
                if (!btf_type_is_typedef(t)) {
                        bpf_log(log, "attach_btf_id %u is not a typedef\n",
                                btf_id);
                        return -EINVAL;
                }
                if (strncmp(prefix, tname, sizeof(prefix) - 1)) {
                        bpf_log(log, "attach_btf_id %u points to wrong type name %s\n",
                                btf_id, tname);
                        return -EINVAL;
                }
                tname += sizeof(prefix) - 1;
                t = btf_type_by_id(btf, t->type);
                if (!btf_type_is_ptr(t))
                        /* should never happen in valid vmlinux build */
                        return -EINVAL;
                t = btf_type_by_id(btf, t->type);
                if (!btf_type_is_func_proto(t))
                        /* should never happen in valid vmlinux build */
                        return -EINVAL;

                break;
        case BPF_TRACE_ITER:
                if (!btf_type_is_func(t)) {
                        bpf_log(log, "attach_btf_id %u is not a function\n",
                                btf_id);
                        return -EINVAL;
                }
                t = btf_type_by_id(btf, t->type);
                if (!btf_type_is_func_proto(t))
                        return -EINVAL;
                ret = btf_distill_func_proto(log, btf, t, tname, &tgt_info->fmodel);
                if (ret)
                        return ret;
                break;
        default:
                if (!prog_extension)
                        return -EINVAL;
                fallthrough;
        case BPF_MODIFY_RETURN:
        case BPF_LSM_MAC:
        case BPF_TRACE_FENTRY:
        case BPF_TRACE_FEXIT:
                if (!btf_type_is_func(t)) {
                        bpf_log(log, "attach_btf_id %u is not a function\n",
                                btf_id);
                        return -EINVAL;
                }
                if (prog_extension &&
                    btf_check_type_match(log, prog, btf, t))
                        return -EINVAL;
                t = btf_type_by_id(btf, t->type);
                if (!btf_type_is_func_proto(t))
                        return -EINVAL;

                if ((prog->aux->saved_dst_prog_type || prog->aux->saved_dst_attach_type) &&
                    (!tgt_prog || prog->aux->saved_dst_prog_type != tgt_prog->type ||
                     prog->aux->saved_dst_attach_type != tgt_prog->expected_attach_type))
                        return -EINVAL;

                if (tgt_prog && conservative)
                        t = NULL;

                ret = btf_distill_func_proto(log, btf, t, tname, &tgt_info->fmodel);
                if (ret < 0)
                        return ret;

                if (tgt_prog) {
                        if (subprog == 0)
                                addr = (long) tgt_prog->bpf_func;
                        else
                                addr = (long) tgt_prog->aux->func[subprog]->bpf_func;
                } else {
                        addr = kallsyms_lookup_name(tname);
                        if (!addr) {
                                bpf_log(log,
                                        "The address of function %s cannot be found\n",
                                        tname);
                                return -ENOENT;
                        }
                }

                if (prog->aux->sleepable) {
                        ret = -EINVAL;
                        switch (prog->type) {
                        case BPF_PROG_TYPE_TRACING:
                                /* fentry/fexit/fmod_ret progs can be sleepable only if they are
                                 * attached to ALLOW_ERROR_INJECTION and are not in denylist.
                                 */
                                if (!check_non_sleepable_error_inject(btf_id) &&
                                    within_error_injection_list(addr))
                                        ret = 0;
                                break;
                        case BPF_PROG_TYPE_LSM:
                                /* LSM progs check that they are attached to bpf_lsm_*() funcs.
                                 * Only some of them are sleepable.
                                 */
                                if (bpf_lsm_is_sleepable_hook(btf_id))
                                        ret = 0;
                                break;
                        default:
                                break;
                        }
                        if (ret) {
                                bpf_log(log, "%s is not sleepable\n", tname);
                                return ret;
                        }
                } else if (prog->expected_attach_type == BPF_MODIFY_RETURN) {
                        if (tgt_prog) {
                                bpf_log(log, "can't modify return codes of BPF programs\n");
                                return -EINVAL;
                        }
                        ret = check_attach_modify_return(addr, tname);
                        if (ret) {
                                bpf_log(log, "%s() is not modifiable\n", tname);
                                return ret;
                        }
                }

                break;
        }
        tgt_info->tgt_addr = addr;
        tgt_info->tgt_name = tname;
        tgt_info->tgt_type = t;
        return 0;
}

static int check_attach_btf_id(struct bpf_verifier_env *env)
{
        struct bpf_prog *prog = env->prog;
        struct bpf_prog *tgt_prog = prog->aux->dst_prog;
        struct bpf_attach_target_info tgt_info = {};
        u32 btf_id = prog->aux->attach_btf_id;
        struct bpf_trampoline *tr;
        int ret;
        u64 key;

        if (prog->aux->sleepable && prog->type != BPF_PROG_TYPE_TRACING &&
            prog->type != BPF_PROG_TYPE_LSM) {
                verbose(env, "Only fentry/fexit/fmod_ret and lsm programs can be sleepable\n");
                return -EINVAL;
        }

        if (prog->type == BPF_PROG_TYPE_STRUCT_OPS)
                return check_struct_ops_btf_id(env);

        if (prog->type != BPF_PROG_TYPE_TRACING &&
            prog->type != BPF_PROG_TYPE_LSM &&
            prog->type != BPF_PROG_TYPE_EXT)
                return 0;

        ret = bpf_check_attach_target(&env->log, prog, tgt_prog, btf_id, &tgt_info);
        if (ret)
                return ret;

        if (tgt_prog && prog->type == BPF_PROG_TYPE_EXT) {
                /* to make freplace equivalent to their targets, they need to
                 * inherit env->ops and expected_attach_type for the rest of the
                 * verification
                 */
                env->ops = bpf_verifier_ops[tgt_prog->type];
                prog->expected_attach_type = tgt_prog->expected_attach_type;
        }

        /* store info about the attachment target that will be used later */
        prog->aux->attach_func_proto = tgt_info.tgt_type;
        prog->aux->attach_func_name = tgt_info.tgt_name;

        if (tgt_prog) {
                prog->aux->saved_dst_prog_type = tgt_prog->type;
                prog->aux->saved_dst_attach_type = tgt_prog->expected_attach_type;
        }

        if (prog->expected_attach_type == BPF_TRACE_RAW_TP) {
                prog->aux->attach_btf_trace = true;
                return 0;
        } else if (prog->expected_attach_type == BPF_TRACE_ITER) {
                if (!bpf_iter_prog_supported(prog))
                        return -EINVAL;
                return 0;
        }

        if (prog->type == BPF_PROG_TYPE_LSM) {
                ret = bpf_lsm_verify_prog(&env->log, prog);
                if (ret < 0)
                        return ret;
        }

        key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id);
        tr = bpf_trampoline_get(key, &tgt_info);
        if (!tr)
                return -ENOMEM;

        prog->aux->dst_trampoline = tr;
        return 0;
}

struct btf *bpf_get_btf_vmlinux(void)
{
        if (!btf_vmlinux && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) {
                mutex_lock(&bpf_verifier_lock);
                if (!btf_vmlinux)
                        btf_vmlinux = btf_parse_vmlinux();
                mutex_unlock(&bpf_verifier_lock);
        }
        return btf_vmlinux;
}

int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
              union bpf_attr __user *uattr)
{
        u64 start_time = ktime_get_ns();
        struct bpf_verifier_env *env;
        struct bpf_verifier_log *log;
        int i, len, ret = -EINVAL;
        bool is_priv;

        /* no program is valid */
        if (ARRAY_SIZE(bpf_verifier_ops) == 0)
                return -EINVAL;

        /* 'struct bpf_verifier_env' can be global, but since it's not small,
         * allocate/free it every time bpf_check() is called
         */
        env = kzalloc(sizeof(struct bpf_verifier_env), GFP_KERNEL);
        if (!env)
                return -ENOMEM;
        log = &env->log;

        len = (*prog)->len;
        env->insn_aux_data =
                vzalloc(array_size(sizeof(struct bpf_insn_aux_data), len));
        ret = -ENOMEM;
        if (!env->insn_aux_data)
                goto err_free_env;
        for (i = 0; i < len; i++)
                env->insn_aux_data[i].orig_idx = i;
        env->prog = *prog;
        env->ops = bpf_verifier_ops[env->prog->type];
        is_priv = bpf_capable();

        bpf_get_btf_vmlinux();

        /* grab the mutex to protect few globals used by verifier */
        if (!is_priv)
                mutex_lock(&bpf_verifier_lock);

        if (attr->log_level || attr->log_buf || attr->log_size) {
                /* user requested verbose verifier output
                 * and supplied buffer to store the verification trace
                 */
                log->level = attr->log_level;
                log->ubuf = (char __user *) (unsigned long) attr->log_buf;
                log->len_total = attr->log_size;

                ret = -EINVAL;
                /* log attributes have to be sane */
                if (log->len_total < 128 || log->len_total > UINT_MAX >> 2 ||
                    !log->level || !log->ubuf || log->level & ~BPF_LOG_MASK)
                        goto err_unlock;
        }

        if (IS_ERR(btf_vmlinux)) {
                /* Either gcc or pahole or kernel are broken. */
                verbose(env, "in-kernel BTF is malformed\n");
                ret = PTR_ERR(btf_vmlinux);
                goto skip_full_check;
        }

        env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT);
        if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
                env->strict_alignment = true;
        if (attr->prog_flags & BPF_F_ANY_ALIGNMENT)
                env->strict_alignment = false;

        env->allow_ptr_leaks = bpf_allow_ptr_leaks();
        env->allow_uninit_stack = bpf_allow_uninit_stack();
        env->allow_ptr_to_map_access = bpf_allow_ptr_to_map_access();
        env->bypass_spec_v1 = bpf_bypass_spec_v1();
        env->bypass_spec_v4 = bpf_bypass_spec_v4();
        env->bpf_capable = bpf_capable();

        if (is_priv)
                env->test_state_freq = attr->prog_flags & BPF_F_TEST_STATE_FREQ;

        if (bpf_prog_is_dev_bound(env->prog->aux)) {
                ret = bpf_prog_offload_verifier_prep(env->prog);
                if (ret)
                        goto skip_full_check;
        }

        env->explored_states = kvcalloc(state_htab_size(env),
                                       sizeof(struct bpf_verifier_state_list *),
                                       GFP_USER);
        ret = -ENOMEM;
        if (!env->explored_states)
                goto skip_full_check;

        ret = check_subprogs(env);
        if (ret < 0)
                goto skip_full_check;

        ret = check_btf_info(env, attr, uattr);
        if (ret < 0)
                goto skip_full_check;

        ret = check_attach_btf_id(env);
        if (ret)
                goto skip_full_check;

        ret = resolve_pseudo_ldimm64(env);
        if (ret < 0)
                goto skip_full_check;

        ret = check_cfg(env);
        if (ret < 0)
                goto skip_full_check;

        ret = do_check_subprogs(env);
        ret = ret ?: do_check_main(env);

        if (ret == 0 && bpf_prog_is_dev_bound(env->prog->aux))
                ret = bpf_prog_offload_finalize(env);

skip_full_check:
        kvfree(env->explored_states);

        if (ret == 0)
                ret = check_max_stack_depth(env);

        /* instruction rewrites happen after this point */
        if (is_priv) {
                if (ret == 0)
                        opt_hard_wire_dead_code_branches(env);
                if (ret == 0)
                        ret = opt_remove_dead_code(env);
                if (ret == 0)
                        ret = opt_remove_nops(env);
        } else {
                if (ret == 0)
                        sanitize_dead_code(env);
        }

        if (ret == 0)
                /* program is valid, convert *(u32*)(ctx + off) accesses */
                ret = convert_ctx_accesses(env);

        if (ret == 0)
                ret = do_misc_fixups(env);

        /* do 32-bit optimization after insn patching has done so those patched
         * insns could be handled correctly.
         */
        if (ret == 0 && !bpf_prog_is_dev_bound(env->prog->aux)) {
                ret = opt_subreg_zext_lo32_rnd_hi32(env, attr);
                env->prog->aux->verifier_zext = bpf_jit_needs_zext() ? !ret
                                                                     : false;
        }

        if (ret == 0)
                ret = fixup_call_args(env);

        env->verification_time = ktime_get_ns() - start_time;
        print_verification_stats(env);

        if (log->level && bpf_verifier_log_full(log))
                ret = -ENOSPC;
        if (log->level && !log->ubuf) {
                ret = -EFAULT;
                goto err_release_maps;
        }

        if (ret)
                goto err_release_maps;

        if (env->used_map_cnt) {
                /* if program passed verifier, update used_maps in bpf_prog_info */
                env->prog->aux->used_maps = kmalloc_array(env->used_map_cnt,
                                                          sizeof(env->used_maps[0]),
                                                          GFP_KERNEL);

                if (!env->prog->aux->used_maps) {
                        ret = -ENOMEM;
                        goto err_release_maps;
                }

                memcpy(env->prog->aux->used_maps, env->used_maps,
                       sizeof(env->used_maps[0]) * env->used_map_cnt);
                env->prog->aux->used_map_cnt = env->used_map_cnt;
        }
        if (env->used_btf_cnt) {
                /* if program passed verifier, update used_btfs in bpf_prog_aux */
                env->prog->aux->used_btfs = kmalloc_array(env->used_btf_cnt,
                                                          sizeof(env->used_btfs[0]),
                                                          GFP_KERNEL);
                if (!env->prog->aux->used_btfs) {
                        ret = -ENOMEM;
                        goto err_release_maps;
                }

                memcpy(env->prog->aux->used_btfs, env->used_btfs,
                       sizeof(env->used_btfs[0]) * env->used_btf_cnt);
                env->prog->aux->used_btf_cnt = env->used_btf_cnt;
        }
        if (env->used_map_cnt || env->used_btf_cnt) {
                /* program is valid. Convert pseudo bpf_ld_imm64 into generic
                 * bpf_ld_imm64 instructions
                 */
                convert_pseudo_ld_imm64(env);
        }

        adjust_btf_func(env);

err_release_maps:
        if (!env->prog->aux->used_maps)
                /* if we didn't copy map pointers into bpf_prog_info, release
                 * them now. Otherwise free_used_maps() will release them.
                 */
                release_maps(env);
        if (!env->prog->aux->used_btfs)
                release_btfs(env);

        /* extension progs temporarily inherit the attach_type of their targets
           for verification purposes, so set it back to zero before returning
         */
        if (env->prog->type == BPF_PROG_TYPE_EXT)
                env->prog->expected_attach_type = 0;

        *prog = env->prog;
err_unlock:
        if (!is_priv)
                mutex_unlock(&bpf_verifier_lock);
        vfree(env->insn_aux_data);
err_free_env:
        kfree(env);
        return ret;
}