tools/perf/util/unwind-libdw.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/compiler.h>
   3 #include <elfutils/libdw.h>
   4 #include <elfutils/libdwfl.h>
   5 #include <inttypes.h>
   6 #include <errno.h>
   7 #include "debug.h"
   8 #include "unwind.h"
   9 #include "unwind-libdw.h"
  10 #include "machine.h"
  11 #include "map.h"
  12 #include "symbol.h"
  13 #include "thread.h"
  14 #include <linux/types.h>
  15 #include <linux/zalloc.h>
  16 #include "event.h"
  17 #include "perf_regs.h"
  18 #include "callchain.h"
  19 #include "util.h"
  20
  21 static char *debuginfo_path;
  22
  23 static const Dwfl_Callbacks offline_callbacks = {
  24         .find_debuginfo         = dwfl_standard_find_debuginfo,
  25         .debuginfo_path         = &debuginfo_path,
  26         .section_address        = dwfl_offline_section_address,
  27 };
  28
  29 static int __report_module(struct addr_location *al, u64 ip,
  30                             struct unwind_info *ui)
  31 {
  32         Dwfl_Module *mod;
  33         struct dso *dso = NULL;
  34         /*
  35          * Some callers will use al->sym, so we can't just use the
  36          * cheaper thread__find_map() here.
  37          */
  38         thread__find_symbol(ui->thread, PERF_RECORD_MISC_USER, ip, al);
  39
  40         if (al->map)
  41                 dso = al->map->dso;
  42
  43         if (!dso)
  44                 return 0;
  45
  46         mod = dwfl_addrmodule(ui->dwfl, ip);
  47         if (mod) {
  48                 Dwarf_Addr s;
  49
  50                 dwfl_module_info(mod, NULL, &s, NULL, NULL, NULL, NULL, NULL);
  51                 if (s != al->map->start - al->map->pgoff)
  52                         mod = 0;
  53         }
  54
  55         if (!mod)
  56                 mod = dwfl_report_elf(ui->dwfl, dso->short_name,
  57                                       (dso->symsrc_filename ? dso->symsrc_filename : dso->long_name), -1, al->map->start - al->map->pgoff,
  58                                       false);
  59
  60         return mod && dwfl_addrmodule(ui->dwfl, ip) == mod ? 0 : -1;
  61 }
  62
  63 static int report_module(u64 ip, struct unwind_info *ui)
  64 {
  65         struct addr_location al;
  66
  67         return __report_module(&al, ip, ui);
  68 }
  69
  70 /*
  71  * Store all entries within entries array,
  72  * we will process it after we finish unwind.
  73  */
  74 static int entry(u64 ip, struct unwind_info *ui)
  75
  76 {
  77         struct unwind_entry *e = &ui->entries[ui->idx++];
  78         struct addr_location al;
  79
  80         if (__report_module(&al, ip, ui))
  81                 return -1;
  82
  83         e->ip  = ip;
  84         e->map = al.map;
  85         e->sym = al.sym;
  86
  87         pr_debug("unwind: %s:ip = 0x%" PRIx64 " (0x%" PRIx64 ")\n",
  88                  al.sym ? al.sym->name : "''",
  89                  ip,
  90                  al.map ? al.map->map_ip(al.map, ip) : (u64) 0);
  91         return 0;
  92 }
  93
  94 static pid_t next_thread(Dwfl *dwfl, void *arg, void **thread_argp)
  95 {
  96         /* We want only single thread to be processed. */
  97         if (*thread_argp != NULL)
  98                 return 0;
  99
 100         *thread_argp = arg;
 101         return dwfl_pid(dwfl);
 102 }
 103
 104 static int access_dso_mem(struct unwind_info *ui, Dwarf_Addr addr,
 105                           Dwarf_Word *data)
 106 {
 107         struct addr_location al;
 108         ssize_t size;
 109
 110         if (!thread__find_map(ui->thread, PERF_RECORD_MISC_USER, addr, &al)) {
 111                 pr_debug("unwind: no map for %lx\n", (unsigned long)addr);
 112                 return -1;
 113         }
 114
 115         if (!al.map->dso)
 116                 return -1;
 117
 118         size = dso__data_read_addr(al.map->dso, al.map, ui->machine,
 119                                    addr, (u8 *) data, sizeof(*data));
 120
 121         return !(size == sizeof(*data));
 122 }
 123
 124 static bool memory_read(Dwfl *dwfl __maybe_unused, Dwarf_Addr addr, Dwarf_Word *result,
 125                         void *arg)
 126 {
 127         struct unwind_info *ui = arg;
 128         struct stack_dump *stack = &ui->sample->user_stack;
 129         u64 start, end;
 130         int offset;
 131         int ret;
 132
 133         ret = perf_reg_value(&start, &ui->sample->user_regs, PERF_REG_SP);
 134         if (ret)
 135                 return false;
 136
 137         end = start + stack->size;
 138
 139         /* Check overflow. */
 140         if (addr + sizeof(Dwarf_Word) < addr)
 141                 return false;
 142
 143         if (addr < start || addr + sizeof(Dwarf_Word) > end) {
 144                 ret = access_dso_mem(ui, addr, result);
 145                 if (ret) {
 146                         pr_debug("unwind: access_mem 0x%" PRIx64 " not inside range"
 147                                  " 0x%" PRIx64 "-0x%" PRIx64 "\n",
 148                                 addr, start, end);
 149                         return false;
 150                 }
 151                 return true;
 152         }
 153
 154         offset  = addr - start;
 155         *result = *(Dwarf_Word *)&stack->data[offset];
 156         pr_debug("unwind: access_mem addr 0x%" PRIx64 ", val %lx, offset %d\n",
 157                  addr, (unsigned long)*result, offset);
 158         return true;
 159 }
 160
 161 static const Dwfl_Thread_Callbacks callbacks = {
 162         .next_thread            = next_thread,
 163         .memory_read            = memory_read,
 164         .set_initial_registers  = libdw__arch_set_initial_registers,
 165 };
 166
 167 static int
 168 frame_callback(Dwfl_Frame *state, void *arg)
 169 {
 170         struct unwind_info *ui = arg;
 171         Dwarf_Addr pc;
 172         bool isactivation;
 173
 174         if (!dwfl_frame_pc(state, &pc, NULL)) {
 175                 pr_err("%s", dwfl_errmsg(-1));
 176                 return DWARF_CB_ABORT;
 177         }
 178
 179         // report the module before we query for isactivation
 180         report_module(pc, ui);
 181
 182         if (!dwfl_frame_pc(state, &pc, &isactivation)) {
 183                 pr_err("%s", dwfl_errmsg(-1));
 184                 return DWARF_CB_ABORT;
 185         }
 186
 187         if (!isactivation)
 188                 --pc;
 189
 190         return entry(pc, ui) || !(--ui->max_stack) ?
 191                DWARF_CB_ABORT : DWARF_CB_OK;
 192 }
 193
 194 int unwind__get_entries(unwind_entry_cb_t cb, void *arg,
 195                         struct thread *thread,
 196                         struct perf_sample *data,
 197                         int max_stack)
 198 {
 199         struct unwind_info *ui, ui_buf = {
 200                 .sample         = data,
 201                 .thread         = thread,
 202                 .machine        = thread->mg->machine,
 203                 .cb             = cb,
 204                 .arg            = arg,
 205                 .max_stack      = max_stack,
 206         };
 207         Dwarf_Word ip;
 208         int err = -EINVAL, i;
 209
 210         if (!data->user_regs.regs)
 211                 return -EINVAL;
 212
 213         ui = zalloc(sizeof(ui_buf) + sizeof(ui_buf.entries[0]) * max_stack);
 214         if (!ui)
 215                 return -ENOMEM;
 216
 217         *ui = ui_buf;
 218
 219         ui->dwfl = dwfl_begin(&offline_callbacks);
 220         if (!ui->dwfl)
 221                 goto out;
 222
 223         err = perf_reg_value(&ip, &data->user_regs, PERF_REG_IP);
 224         if (err)
 225                 goto out;
 226
 227         err = report_module(ip, ui);
 228         if (err)
 229                 goto out;
 230
 231         err = !dwfl_attach_state(ui->dwfl, EM_NONE, thread->tid, &callbacks, ui);
 232         if (err)
 233                 goto out;
 234
 235         err = dwfl_getthread_frames(ui->dwfl, thread->tid, frame_callback, ui);
 236
 237         if (err && ui->max_stack != max_stack)
 238                 err = 0;
 239
 240         /*
 241          * Display what we got based on the order setup.
 242          */
 243         for (i = 0; i < ui->idx && !err; i++) {
 244                 int j = i;
 245
 246                 if (callchain_param.order == ORDER_CALLER)
 247                         j = ui->idx - i - 1;
 248
 249                 err = ui->entries[j].ip ? ui->cb(&ui->entries[j], ui->arg) : 0;
 250         }
 251
 252  out:
 253         if (err)
 254                 pr_debug("unwind: failed with '%s'\n", dwfl_errmsg(-1));
 255
 256         dwfl_end(ui->dwfl);
 257         free(ui);
 258         return 0;
 259 }