arch/arc/kernel/kgdb.c

   1 /*
   2  * kgdb support for ARC
   3  *
   4  * Copyright (C) 2012 Synopsys, Inc. (www.synopsys.com)
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/kgdb.h>
  12 #include <linux/sched.h>
  13 #include <linux/sched/task_stack.h>
  14 #include <asm/disasm.h>
  15 #include <asm/cacheflush.h>
  16
  17 static void to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
  18                         struct callee_regs *cregs)
  19 {
  20         int regno;
  21
  22         for (regno = 0; regno <= 26; regno++)
  23                 gdb_regs[_R0 + regno] = get_reg(regno, kernel_regs, cregs);
  24
  25         for (regno = 27; regno < GDB_MAX_REGS; regno++)
  26                 gdb_regs[regno] = 0;
  27
  28         gdb_regs[_FP]           = kernel_regs->fp;
  29         gdb_regs[__SP]          = kernel_regs->sp;
  30         gdb_regs[_BLINK]        = kernel_regs->blink;
  31         gdb_regs[_RET]          = kernel_regs->ret;
  32         gdb_regs[_STATUS32]     = kernel_regs->status32;
  33         gdb_regs[_LP_COUNT]     = kernel_regs->lp_count;
  34         gdb_regs[_LP_END]       = kernel_regs->lp_end;
  35         gdb_regs[_LP_START]     = kernel_regs->lp_start;
  36         gdb_regs[_BTA]          = kernel_regs->bta;
  37         gdb_regs[_STOP_PC]      = kernel_regs->ret;
  38 }
  39
  40 static void from_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs,
  41                         struct callee_regs *cregs)
  42 {
  43         int regno;
  44
  45         for (regno = 0; regno <= 26; regno++)
  46                 set_reg(regno, gdb_regs[regno + _R0], kernel_regs, cregs);
  47
  48         kernel_regs->fp         = gdb_regs[_FP];
  49         kernel_regs->sp         = gdb_regs[__SP];
  50         kernel_regs->blink      = gdb_regs[_BLINK];
  51         kernel_regs->ret        = gdb_regs[_RET];
  52         kernel_regs->status32   = gdb_regs[_STATUS32];
  53         kernel_regs->lp_count   = gdb_regs[_LP_COUNT];
  54         kernel_regs->lp_end     = gdb_regs[_LP_END];
  55         kernel_regs->lp_start   = gdb_regs[_LP_START];
  56         kernel_regs->bta        = gdb_regs[_BTA];
  57 }
  58
  59
  60 void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
  61 {
  62         to_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
  63                 current->thread.callee_reg);
  64 }
  65
  66 void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
  67 {
  68         from_gdb_regs(gdb_regs, kernel_regs, (struct callee_regs *)
  69                 current->thread.callee_reg);
  70 }
  71
  72 void sleeping_thread_to_gdb_regs(unsigned long *gdb_regs,
  73                                  struct task_struct *task)
  74 {
  75         if (task)
  76                 to_gdb_regs(gdb_regs, task_pt_regs(task),
  77                         (struct callee_regs *) task->thread.callee_reg);
  78 }
  79
  80 struct single_step_data_t {
  81         uint16_t opcode[2];
  82         unsigned long address[2];
  83         int is_branch;
  84         int armed;
  85 } single_step_data;
  86
  87 static void undo_single_step(struct pt_regs *regs)
  88 {
  89         if (single_step_data.armed) {
  90                 int i;
  91
  92                 for (i = 0; i < (single_step_data.is_branch ? 2 : 1); i++) {
  93                         memcpy((void *) single_step_data.address[i],
  94                                 &single_step_data.opcode[i],
  95                                 BREAK_INSTR_SIZE);
  96
  97                         flush_icache_range(single_step_data.address[i],
  98                                 single_step_data.address[i] +
  99                                 BREAK_INSTR_SIZE);
 100                 }
 101                 single_step_data.armed = 0;
 102         }
 103 }
 104
 105 static void place_trap(unsigned long address, void *save)
 106 {
 107         memcpy(save, (void *) address, BREAK_INSTR_SIZE);
 108         memcpy((void *) address, &arch_kgdb_ops.gdb_bpt_instr,
 109                 BREAK_INSTR_SIZE);
 110         flush_icache_range(address, address + BREAK_INSTR_SIZE);
 111 }
 112
 113 static void do_single_step(struct pt_regs *regs)
 114 {
 115         single_step_data.is_branch = disasm_next_pc((unsigned long)
 116                 regs->ret, regs, (struct callee_regs *)
 117                 current->thread.callee_reg,
 118                 &single_step_data.address[0],
 119                 &single_step_data.address[1]);
 120
 121         place_trap(single_step_data.address[0], &single_step_data.opcode[0]);
 122
 123         if (single_step_data.is_branch) {
 124                 place_trap(single_step_data.address[1],
 125                         &single_step_data.opcode[1]);
 126         }
 127
 128         single_step_data.armed++;
 129 }
 130
 131 int kgdb_arch_handle_exception(int e_vector, int signo, int err_code,
 132                                char *remcomInBuffer, char *remcomOutBuffer,
 133                                struct pt_regs *regs)
 134 {
 135         unsigned long addr;
 136         char *ptr;
 137
 138         undo_single_step(regs);
 139
 140         switch (remcomInBuffer[0]) {
 141         case 's':
 142         case 'c':
 143                 ptr = &remcomInBuffer[1];
 144                 if (kgdb_hex2long(&ptr, &addr))
 145                         regs->ret = addr;
 146
 147         case 'D':
 148         case 'k':
 149                 atomic_set(&kgdb_cpu_doing_single_step, -1);
 150
 151                 if (remcomInBuffer[0] == 's') {
 152                         do_single_step(regs);
 153                         atomic_set(&kgdb_cpu_doing_single_step,
 154                                    smp_processor_id());
 155                 }
 156
 157                 return 0;
 158         }
 159         return -1;
 160 }
 161
 162 int kgdb_arch_init(void)
 163 {
 164         single_step_data.armed = 0;
 165         return 0;
 166 }
 167
 168 void kgdb_trap(struct pt_regs *regs)
 169 {
 170         /* trap_s 3 is used for breakpoints that overwrite existing
 171          * instructions, while trap_s 4 is used for compiled breakpoints.
 172          *
 173          * with trap_s 3 breakpoints the original instruction needs to be
 174          * restored and continuation needs to start at the location of the
 175          * breakpoint.
 176          *
 177          * with trap_s 4 (compiled) breakpoints, continuation needs to
 178          * start after the breakpoint.
 179          */
 180         if (regs->ecr_param == 3)
 181                 instruction_pointer(regs) -= BREAK_INSTR_SIZE;
 182
 183         kgdb_handle_exception(1, SIGTRAP, 0, regs);
 184 }
 185
 186 void kgdb_arch_exit(void)
 187 {
 188 }
 189
 190 void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long ip)
 191 {
 192         instruction_pointer(regs) = ip;
 193 }
 194
 195 void kgdb_call_nmi_hook(void *ignored)
 196 {
 197         /* Default implementation passes get_irq_regs() but we don't */
 198         kgdb_nmicallback(raw_smp_processor_id(), NULL);
 199 }
 200
 201 const struct kgdb_arch arch_kgdb_ops = {
 202         /* breakpoint instruction: TRAP_S 0x3 */
 203 #ifdef CONFIG_CPU_BIG_ENDIAN
 204         .gdb_bpt_instr          = {0x78, 0x7e},
 205 #else
 206         .gdb_bpt_instr          = {0x7e, 0x78},
 207 #endif
 208 };