tools/objtool/arch/x86/decode.c

   1 /*
   2  * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com>
   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
   6  * as published by the Free Software Foundation; either version 2
   7  * of 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  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20
  21 #define unlikely(cond) (cond)
  22 #include "insn/insn.h"
  23 #include "insn/inat.c"
  24 #include "insn/insn.c"
  25
  26 #include "../../elf.h"
  27 #include "../../arch.h"
  28 #include "../../warn.h"
  29
  30 static int is_x86_64(struct elf *elf)
  31 {
  32         switch (elf->ehdr.e_machine) {
  33         case EM_X86_64:
  34                 return 1;
  35         case EM_386:
  36                 return 0;
  37         default:
  38                 WARN("unexpected ELF machine type %d", elf->ehdr.e_machine);
  39                 return -1;
  40         }
  41 }
  42
  43 int arch_decode_instruction(struct elf *elf, struct section *sec,
  44                             unsigned long offset, unsigned int maxlen,
  45                             unsigned int *len, unsigned char *type,
  46                             unsigned long *immediate)
  47 {
  48         struct insn insn;
  49         int x86_64;
  50         unsigned char op1, op2, ext;
  51
  52         x86_64 = is_x86_64(elf);
  53         if (x86_64 == -1)
  54                 return -1;
  55
  56         insn_init(&insn, (void *)(sec->data + offset), maxlen, x86_64);
  57         insn_get_length(&insn);
  58         insn_get_opcode(&insn);
  59         insn_get_modrm(&insn);
  60         insn_get_immediate(&insn);
  61
  62         if (!insn_complete(&insn)) {
  63                 WARN_FUNC("can't decode instruction", sec, offset);
  64                 return -1;
  65         }
  66
  67         *len = insn.length;
  68         *type = INSN_OTHER;
  69
  70         if (insn.vex_prefix.nbytes)
  71                 return 0;
  72
  73         op1 = insn.opcode.bytes[0];
  74         op2 = insn.opcode.bytes[1];
  75
  76         switch (op1) {
  77         case 0x55:
  78                 if (!insn.rex_prefix.nbytes)
  79                         /* push rbp */
  80                         *type = INSN_FP_SAVE;
  81                 break;
  82
  83         case 0x5d:
  84                 if (!insn.rex_prefix.nbytes)
  85                         /* pop rbp */
  86                         *type = INSN_FP_RESTORE;
  87                 break;
  88
  89         case 0x70 ... 0x7f:
  90                 *type = INSN_JUMP_CONDITIONAL;
  91                 break;
  92
  93         case 0x89:
  94                 if (insn.rex_prefix.nbytes == 1 &&
  95                     insn.rex_prefix.bytes[0] == 0x48 &&
  96                     insn.modrm.nbytes && insn.modrm.bytes[0] == 0xe5)
  97                         /* mov rsp, rbp */
  98                         *type = INSN_FP_SETUP;
  99                 break;
 100
 101         case 0x90:
 102                 *type = INSN_NOP;
 103                 break;
 104
 105         case 0x0f:
 106                 if (op2 >= 0x80 && op2 <= 0x8f)
 107                         *type = INSN_JUMP_CONDITIONAL;
 108                 else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
 109                          op2 == 0x35)
 110                         /* sysenter, sysret */
 111                         *type = INSN_CONTEXT_SWITCH;
 112                 else if (op2 == 0x0b || op2 == 0xb9)
 113                         /* ud2 */
 114                         *type = INSN_BUG;
 115                 else if (op2 == 0x0d || op2 == 0x1f)
 116                         /* nopl/nopw */
 117                         *type = INSN_NOP;
 118                 else if (op2 == 0x01 && insn.modrm.nbytes &&
 119                          (insn.modrm.bytes[0] == 0xc2 ||
 120                           insn.modrm.bytes[0] == 0xd8))
 121                         /* vmlaunch, vmrun */
 122                         *type = INSN_CONTEXT_SWITCH;
 123
 124                 break;
 125
 126         case 0xc9: /* leave */
 127                 *type = INSN_FP_RESTORE;
 128                 break;
 129
 130         case 0xe3: /* jecxz/jrcxz */
 131                 *type = INSN_JUMP_CONDITIONAL;
 132                 break;
 133
 134         case 0xe9:
 135         case 0xeb:
 136                 *type = INSN_JUMP_UNCONDITIONAL;
 137                 break;
 138
 139         case 0xc2:
 140         case 0xc3:
 141                 *type = INSN_RETURN;
 142                 break;
 143
 144         case 0xc5: /* iret */
 145         case 0xca: /* retf */
 146         case 0xcb: /* retf */
 147                 *type = INSN_CONTEXT_SWITCH;
 148                 break;
 149
 150         case 0xe8:
 151                 *type = INSN_CALL;
 152                 break;
 153
 154         case 0xff:
 155                 ext = X86_MODRM_REG(insn.modrm.bytes[0]);
 156                 if (ext == 2 || ext == 3)
 157                         *type = INSN_CALL_DYNAMIC;
 158                 else if (ext == 4)
 159                         *type = INSN_JUMP_DYNAMIC;
 160                 else if (ext == 5) /*jmpf */
 161                         *type = INSN_CONTEXT_SWITCH;
 162
 163                 break;
 164
 165         default:
 166                 break;
 167         }
 168
 169         *immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
 170
 171         return 0;
 172 }