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 unsigned char op_to_cfi_reg[][2] = {
  31         {CFI_AX, CFI_R8},
  32         {CFI_CX, CFI_R9},
  33         {CFI_DX, CFI_R10},
  34         {CFI_BX, CFI_R11},
  35         {CFI_SP, CFI_R12},
  36         {CFI_BP, CFI_R13},
  37         {CFI_SI, CFI_R14},
  38         {CFI_DI, CFI_R15},
  39 };
  40
  41 static int is_x86_64(struct elf *elf)
  42 {
  43         switch (elf->ehdr.e_machine) {
  44         case EM_X86_64:
  45                 return 1;
  46         case EM_386:
  47                 return 0;
  48         default:
  49                 WARN("unexpected ELF machine type %d", elf->ehdr.e_machine);
  50                 return -1;
  51         }
  52 }
  53
  54 bool arch_callee_saved_reg(unsigned char reg)
  55 {
  56         switch (reg) {
  57         case CFI_BP:
  58         case CFI_BX:
  59         case CFI_R12:
  60         case CFI_R13:
  61         case CFI_R14:
  62         case CFI_R15:
  63                 return true;
  64
  65         case CFI_AX:
  66         case CFI_CX:
  67         case CFI_DX:
  68         case CFI_SI:
  69         case CFI_DI:
  70         case CFI_SP:
  71         case CFI_R8:
  72         case CFI_R9:
  73         case CFI_R10:
  74         case CFI_R11:
  75         case CFI_RA:
  76         default:
  77                 return false;
  78         }
  79 }
  80
  81 int arch_decode_instruction(struct elf *elf, struct section *sec,
  82                             unsigned long offset, unsigned int maxlen,
  83                             unsigned int *len, unsigned char *type,
  84                             unsigned long *immediate, struct stack_op *op)
  85 {
  86         struct insn insn;
  87         int x86_64, sign;
  88         unsigned char op1, op2, rex = 0, rex_b = 0, rex_r = 0, rex_w = 0,
  89                       rex_x = 0, modrm = 0, modrm_mod = 0, modrm_rm = 0,
  90                       modrm_reg = 0, sib = 0;
  91
  92         x86_64 = is_x86_64(elf);
  93         if (x86_64 == -1)
  94                 return -1;
  95
  96         insn_init(&insn, sec->data->d_buf + offset, maxlen, x86_64);
  97         insn_get_length(&insn);
  98
  99         if (!insn_complete(&insn)) {
 100                 WARN_FUNC("can't decode instruction", sec, offset);
 101                 return -1;
 102         }
 103
 104         *len = insn.length;
 105         *type = INSN_OTHER;
 106
 107         if (insn.vex_prefix.nbytes)
 108                 return 0;
 109
 110         op1 = insn.opcode.bytes[0];
 111         op2 = insn.opcode.bytes[1];
 112
 113         if (insn.rex_prefix.nbytes) {
 114                 rex = insn.rex_prefix.bytes[0];
 115                 rex_w = X86_REX_W(rex) >> 3;
 116                 rex_r = X86_REX_R(rex) >> 2;
 117                 rex_x = X86_REX_X(rex) >> 1;
 118                 rex_b = X86_REX_B(rex);
 119         }
 120
 121         if (insn.modrm.nbytes) {
 122                 modrm = insn.modrm.bytes[0];
 123                 modrm_mod = X86_MODRM_MOD(modrm);
 124                 modrm_reg = X86_MODRM_REG(modrm);
 125                 modrm_rm = X86_MODRM_RM(modrm);
 126         }
 127
 128         if (insn.sib.nbytes)
 129                 sib = insn.sib.bytes[0];
 130
 131         switch (op1) {
 132
 133         case 0x1:
 134         case 0x29:
 135                 if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
 136
 137                         /* add/sub reg, %rsp */
 138                         *type = INSN_STACK;
 139                         op->src.type = OP_SRC_ADD;
 140                         op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 141                         op->dest.type = OP_SRC_REG;
 142                         op->dest.reg = CFI_SP;
 143                 }
 144                 break;
 145
 146         case 0x50 ... 0x57:
 147
 148                 /* push reg */
 149                 *type = INSN_STACK;
 150                 op->src.type = OP_SRC_REG;
 151                 op->src.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
 152                 op->dest.type = OP_DEST_PUSH;
 153
 154                 break;
 155
 156         case 0x58 ... 0x5f:
 157
 158                 /* pop reg */
 159                 *type = INSN_STACK;
 160                 op->src.type = OP_SRC_POP;
 161                 op->dest.type = OP_DEST_REG;
 162                 op->dest.reg = op_to_cfi_reg[op1 & 0x7][rex_b];
 163
 164                 break;
 165
 166         case 0x68:
 167         case 0x6a:
 168                 /* push immediate */
 169                 *type = INSN_STACK;
 170                 op->src.type = OP_SRC_CONST;
 171                 op->dest.type = OP_DEST_PUSH;
 172                 break;
 173
 174         case 0x70 ... 0x7f:
 175                 *type = INSN_JUMP_CONDITIONAL;
 176                 break;
 177
 178         case 0x81:
 179         case 0x83:
 180                 if (rex != 0x48)
 181                         break;
 182
 183                 if (modrm == 0xe4) {
 184                         /* and imm, %rsp */
 185                         *type = INSN_STACK;
 186                         op->src.type = OP_SRC_AND;
 187                         op->src.reg = CFI_SP;
 188                         op->src.offset = insn.immediate.value;
 189                         op->dest.type = OP_DEST_REG;
 190                         op->dest.reg = CFI_SP;
 191                         break;
 192                 }
 193
 194                 if (modrm == 0xc4)
 195                         sign = 1;
 196                 else if (modrm == 0xec)
 197                         sign = -1;
 198                 else
 199                         break;
 200
 201                 /* add/sub imm, %rsp */
 202                 *type = INSN_STACK;
 203                 op->src.type = OP_SRC_ADD;
 204                 op->src.reg = CFI_SP;
 205                 op->src.offset = insn.immediate.value * sign;
 206                 op->dest.type = OP_DEST_REG;
 207                 op->dest.reg = CFI_SP;
 208                 break;
 209
 210         case 0x89:
 211                 if (rex == 0x48 && modrm == 0xe5) {
 212
 213                         /* mov %rsp, %rbp */
 214                         *type = INSN_STACK;
 215                         op->src.type = OP_SRC_REG;
 216                         op->src.reg = CFI_SP;
 217                         op->dest.type = OP_DEST_REG;
 218                         op->dest.reg = CFI_BP;
 219                         break;
 220                 }
 221
 222                 if (rex_w && !rex_b && modrm_mod == 3 && modrm_rm == 4) {
 223
 224                         /* mov reg, %rsp */
 225                         *type = INSN_STACK;
 226                         op->src.type = OP_SRC_REG;
 227                         op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 228                         op->dest.type = OP_DEST_REG;
 229                         op->dest.reg = CFI_SP;
 230                         break;
 231                 }
 232
 233                 /* fallthrough */
 234         case 0x88:
 235                 if (!rex_b &&
 236                     (modrm_mod == 1 || modrm_mod == 2) && modrm_rm == 5) {
 237
 238                         /* mov reg, disp(%rbp) */
 239                         *type = INSN_STACK;
 240                         op->src.type = OP_SRC_REG;
 241                         op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 242                         op->dest.type = OP_DEST_REG_INDIRECT;
 243                         op->dest.reg = CFI_BP;
 244                         op->dest.offset = insn.displacement.value;
 245
 246                 } else if (rex_w && !rex_b && modrm_rm == 4 && sib == 0x24) {
 247
 248                         /* mov reg, disp(%rsp) */
 249                         *type = INSN_STACK;
 250                         op->src.type = OP_SRC_REG;
 251                         op->src.reg = op_to_cfi_reg[modrm_reg][rex_r];
 252                         op->dest.type = OP_DEST_REG_INDIRECT;
 253                         op->dest.reg = CFI_SP;
 254                         op->dest.offset = insn.displacement.value;
 255                 }
 256
 257                 break;
 258
 259         case 0x8b:
 260                 if (rex_w && !rex_b && modrm_mod == 1 && modrm_rm == 5) {
 261
 262                         /* mov disp(%rbp), reg */
 263                         *type = INSN_STACK;
 264                         op->src.type = OP_SRC_REG_INDIRECT;
 265                         op->src.reg = CFI_BP;
 266                         op->src.offset = insn.displacement.value;
 267                         op->dest.type = OP_DEST_REG;
 268                         op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
 269
 270                 } else if (rex_w && !rex_b && sib == 0x24 &&
 271                            modrm_mod != 3 && modrm_rm == 4) {
 272
 273                         /* mov disp(%rsp), reg */
 274                         *type = INSN_STACK;
 275                         op->src.type = OP_SRC_REG_INDIRECT;
 276                         op->src.reg = CFI_SP;
 277                         op->src.offset = insn.displacement.value;
 278                         op->dest.type = OP_DEST_REG;
 279                         op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
 280                 }
 281
 282                 break;
 283
 284         case 0x8d:
 285                 if (sib == 0x24 && rex_w && !rex_b && !rex_x) {
 286
 287                         /* lea disp(%rsp), reg */
 288                         *type = INSN_STACK;
 289                         op->src.type = OP_SRC_ADD;
 290                         op->src.reg = CFI_SP;
 291                         op->src.offset = insn.displacement.value;
 292                         op->dest.type = OP_DEST_REG;
 293                         op->dest.reg = op_to_cfi_reg[modrm_reg][rex_r];
 294
 295                 } else if (rex == 0x48 && modrm == 0x65) {
 296
 297                         /* lea disp(%rbp), %rsp */
 298                         *type = INSN_STACK;
 299                         op->src.type = OP_SRC_ADD;
 300                         op->src.reg = CFI_BP;
 301                         op->src.offset = insn.displacement.value;
 302                         op->dest.type = OP_DEST_REG;
 303                         op->dest.reg = CFI_SP;
 304
 305                 } else if (rex == 0x49 && modrm == 0x62 &&
 306                            insn.displacement.value == -8) {
 307
 308                         /*
 309                          * lea -0x8(%r10), %rsp
 310                          *
 311                          * Restoring rsp back to its original value after a
 312                          * stack realignment.
 313                          */
 314                         *type = INSN_STACK;
 315                         op->src.type = OP_SRC_ADD;
 316                         op->src.reg = CFI_R10;
 317                         op->src.offset = -8;
 318                         op->dest.type = OP_DEST_REG;
 319                         op->dest.reg = CFI_SP;
 320
 321                 } else if (rex == 0x49 && modrm == 0x65 &&
 322                            insn.displacement.value == -16) {
 323
 324                         /*
 325                          * lea -0x10(%r13), %rsp
 326                          *
 327                          * Restoring rsp back to its original value after a
 328                          * stack realignment.
 329                          */
 330                         *type = INSN_STACK;
 331                         op->src.type = OP_SRC_ADD;
 332                         op->src.reg = CFI_R13;
 333                         op->src.offset = -16;
 334                         op->dest.type = OP_DEST_REG;
 335                         op->dest.reg = CFI_SP;
 336                 }
 337
 338                 break;
 339
 340         case 0x8f:
 341                 /* pop to mem */
 342                 *type = INSN_STACK;
 343                 op->src.type = OP_SRC_POP;
 344                 op->dest.type = OP_DEST_MEM;
 345                 break;
 346
 347         case 0x90:
 348                 *type = INSN_NOP;
 349                 break;
 350
 351         case 0x9c:
 352                 /* pushf */
 353                 *type = INSN_STACK;
 354                 op->src.type = OP_SRC_CONST;
 355                 op->dest.type = OP_DEST_PUSH;
 356                 break;
 357
 358         case 0x9d:
 359                 /* popf */
 360                 *type = INSN_STACK;
 361                 op->src.type = OP_SRC_POP;
 362                 op->dest.type = OP_DEST_MEM;
 363                 break;
 364
 365         case 0x0f:
 366
 367                 if (op2 >= 0x80 && op2 <= 0x8f) {
 368
 369                         *type = INSN_JUMP_CONDITIONAL;
 370
 371                 } else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 ||
 372                            op2 == 0x35) {
 373
 374                         /* sysenter, sysret */
 375                         *type = INSN_CONTEXT_SWITCH;
 376
 377                 } else if (op2 == 0x0b || op2 == 0xb9) {
 378
 379                         /* ud2 */
 380                         *type = INSN_BUG;
 381
 382                 } else if (op2 == 0x0d || op2 == 0x1f) {
 383
 384                         /* nopl/nopw */
 385                         *type = INSN_NOP;
 386
 387                 } else if (op2 == 0xa0 || op2 == 0xa8) {
 388
 389                         /* push fs/gs */
 390                         *type = INSN_STACK;
 391                         op->src.type = OP_SRC_CONST;
 392                         op->dest.type = OP_DEST_PUSH;
 393
 394                 } else if (op2 == 0xa1 || op2 == 0xa9) {
 395
 396                         /* pop fs/gs */
 397                         *type = INSN_STACK;
 398                         op->src.type = OP_SRC_POP;
 399                         op->dest.type = OP_DEST_MEM;
 400                 }
 401
 402                 break;
 403
 404         case 0xc9:
 405                 /*
 406                  * leave
 407                  *
 408                  * equivalent to:
 409                  * mov bp, sp
 410                  * pop bp
 411                  */
 412                 *type = INSN_STACK;
 413                 op->dest.type = OP_DEST_LEAVE;
 414
 415                 break;
 416
 417         case 0xe3:
 418                 /* jecxz/jrcxz */
 419                 *type = INSN_JUMP_CONDITIONAL;
 420                 break;
 421
 422         case 0xe9:
 423         case 0xeb:
 424                 *type = INSN_JUMP_UNCONDITIONAL;
 425                 break;
 426
 427         case 0xc2:
 428         case 0xc3:
 429                 *type = INSN_RETURN;
 430                 break;
 431
 432         case 0xca: /* retf */
 433         case 0xcb: /* retf */
 434         case 0xcf: /* iret */
 435                 *type = INSN_CONTEXT_SWITCH;
 436                 break;
 437
 438         case 0xe8:
 439                 *type = INSN_CALL;
 440                 break;
 441
 442         case 0xff:
 443                 if (modrm_reg == 2 || modrm_reg == 3)
 444
 445                         *type = INSN_CALL_DYNAMIC;
 446
 447                 else if (modrm_reg == 4)
 448
 449                         *type = INSN_JUMP_DYNAMIC;
 450
 451                 else if (modrm_reg == 5)
 452
 453                         /* jmpf */
 454                         *type = INSN_CONTEXT_SWITCH;
 455
 456                 else if (modrm_reg == 6) {
 457
 458                         /* push from mem */
 459                         *type = INSN_STACK;
 460                         op->src.type = OP_SRC_CONST;
 461                         op->dest.type = OP_DEST_PUSH;
 462                 }
 463
 464                 break;
 465
 466         default:
 467                 break;
 468         }
 469
 470         *immediate = insn.immediate.nbytes ? insn.immediate.value : 0;
 471
 472         return 0;
 473 }
 474
 475 void arch_initial_func_cfi_state(struct cfi_state *state)
 476 {
 477         int i;
 478
 479         for (i = 0; i < CFI_NUM_REGS; i++) {
 480                 state->regs[i].base = CFI_UNDEFINED;
 481                 state->regs[i].offset = 0;
 482         }
 483
 484         /* initial CFA (call frame address) */
 485         state->cfa.base = CFI_SP;
 486         state->cfa.offset = 8;
 487
 488         /* initial RA (return address) */
 489         state->regs[16].base = CFI_CFA;
 490         state->regs[16].offset = -8;
 491 }