payloads/libpayload/arch/x86/gdb.c

   1 /*
   2  * Copyright 2014 Google Inc.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of
   7  * the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but without any warranty; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <exception.h>
  16 #include <gdb.h>
  17 #include <libpayload.h>
  18 #include <stddef.h>
  19
  20 static const u8 type_to_signal[] = {
  21         [EXC_DE]  = GDB_SIGFPE,
  22         [EXC_DB]  = GDB_SIGTRAP,
  23         [EXC_NMI] = GDB_SIGKILL,
  24         [EXC_BP]  = GDB_SIGTRAP,
  25         [EXC_OF]  = GDB_SIGFPE,
  26         [EXC_BR]  = GDB_SIGSEGV,
  27         [EXC_UD]  = GDB_SIGILL,
  28         [EXC_NM]  = GDB_SIGEMT,
  29         [EXC_DF]  = GDB_SIGKILL,
  30         [EXC_TS]  = GDB_SIGSEGV,
  31         [EXC_NP]  = GDB_SIGSEGV,
  32         [EXC_SS]  = GDB_SIGBUS,
  33         [EXC_GP]  = GDB_SIGSEGV,
  34         [EXC_PF]  = GDB_SIGSEGV,
  35         [EXC_MF]  = GDB_SIGEMT,
  36         [EXC_AC]  = GDB_SIGBUS,
  37         [EXC_MC]  = GDB_SIGKILL,
  38         [EXC_XF]  = GDB_SIGFPE,
  39         [EXC_SX]  = GDB_SIGFPE,
  40 };
  41
  42 static void gdb_exception_hook(u8 vector)
  43 {
  44         gdb_command_loop(type_to_signal[vector]);
  45 }
  46
  47 void gdb_arch_init(void)
  48 {
  49         for (int vector = 0; vector < ARRAY_SIZE(type_to_signal); ++vector) {
  50                 if (type_to_signal[vector])
  51                         set_interrupt_handler(vector, &gdb_exception_hook);
  52         }
  53 }
  54
  55 void gdb_arch_enter(void)
  56 {
  57         u8 *stack_pointer;
  58 #if CONFIG(LP_ARCH_X86_64)
  59         asm volatile ("movq %%rsp, %0" : "=r"(stack_pointer));
  60 #else
  61         asm volatile ("mov %%esp, %0" : "=r"(stack_pointer));
  62 #endif
  63
  64         /* Avoid reentrant exceptions, just call the hook if in one already. */
  65         if (stack_pointer >= exception_stack && stack_pointer <= exception_stack_end)
  66                 gdb_exception_hook(EXC_BP);
  67         else
  68                 asm volatile ("int3");
  69 }
  70
  71 int gdb_arch_set_single_step(int on)
  72 {
  73         const size_t tf_bit = 1 << 8;
  74
  75         if (on)
  76                 exception_state->regs.reg_flags |= tf_bit;
  77         else
  78                 exception_state->regs.reg_flags &= ~tf_bit;
  79
  80         return 0;
  81 }
  82
  83 void gdb_arch_encode_regs(struct gdb_message *message)
  84 {
  85         gdb_message_encode_bytes(message, &exception_state->regs,
  86                                  sizeof(exception_state->regs));
  87 }
  88
  89 void gdb_arch_decode_regs(int offset, struct gdb_message *message)
  90 {
  91         gdb_message_decode_bytes(message, offset, &exception_state->regs,
  92                                  sizeof(exception_state->regs));
  93 }