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
  19 static const u8 type_to_signal[] = {
  20         [EXC_DE]  = GDB_SIGFPE,
  21         [EXC_DB]  = GDB_SIGTRAP,
  22         [EXC_NMI] = GDB_SIGKILL,
  23         [EXC_BP]  = GDB_SIGTRAP,
  24         [EXC_OF]  = GDB_SIGFPE,
  25         [EXC_BR]  = GDB_SIGSEGV,
  26         [EXC_UD]  = GDB_SIGILL,
  27         [EXC_NM]  = GDB_SIGEMT,
  28         [EXC_DF]  = GDB_SIGKILL,
  29         [EXC_TS]  = GDB_SIGSEGV,
  30         [EXC_NP]  = GDB_SIGSEGV,
  31         [EXC_SS]  = GDB_SIGBUS,
  32         [EXC_GP]  = GDB_SIGSEGV,
  33         [EXC_PF]  = GDB_SIGSEGV,
  34         [EXC_MF]  = GDB_SIGEMT,
  35         [EXC_AC]  = GDB_SIGBUS,
  36         [EXC_MC]  = GDB_SIGKILL,
  37         [EXC_XF]  = GDB_SIGFPE,
  38         [EXC_SX]  = GDB_SIGFPE,
  39 };
  40
  41 static int gdb_exception_hook(u32 type)
  42 {
  43         if (type >= ARRAY_SIZE(type_to_signal) || !type_to_signal[type])
  44                 return 0;
  45         gdb_command_loop(type_to_signal[type]);
  46         return 1;
  47 }
  48
  49 void gdb_arch_init(void)
  50 {
  51         exception_install_hook(&gdb_exception_hook);
  52 }
  53
  54 void gdb_arch_enter(void)
  55 {
  56         u32 *esp;
  57
  58         asm volatile ("mov %%esp, %0" : "=r"(esp) );
  59
  60         /* Avoid reentrant exceptions, just call the hook if in one already. */
  61         if (esp >= exception_stack && esp <= exception_stack_end)
  62                 gdb_exception_hook(EXC_BP);
  63         else
  64                 asm volatile ("int3");
  65 }
  66
  67 int gdb_arch_set_single_step(int on)
  68 {
  69         const u32 tf_bit = 1 << 8;
  70
  71         if (on)
  72                 exception_state->regs.eflags |= tf_bit;
  73         else
  74                 exception_state->regs.eflags &= ~tf_bit;
  75
  76         return 0;
  77 }
  78
  79 void gdb_arch_encode_regs(struct gdb_message *message)
  80 {
  81         gdb_message_encode_bytes(message, &exception_state->regs,
  82                                  sizeof(exception_state->regs));
  83 }
  84
  85 void gdb_arch_decode_regs(int offset, struct gdb_message *message)
  86 {
  87         gdb_message_decode_bytes(message, offset, &exception_state->regs,
  88                                  sizeof(exception_state->regs));
  89 }