1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com> 4 */ 5 6 #include <stdio.h> 7 #include <stdlib.h> 8 9 #define unlikely(cond) (cond) 10 #include <asm/insn.h> 11 #include "../../../arch/x86/lib/inat.c" 12 #include "../../../arch/x86/lib/insn.c" 13 14 #define CONFIG_64BIT 1 15 #include <asm/nops.h> 16 17 #include <asm/orc_types.h> 18 #include <objtool/check.h> 19 #include <objtool/elf.h> 20 #include <objtool/arch.h> 21 #include <objtool/warn.h> 22 #include <objtool/endianness.h> 23 #include <objtool/builtin.h> 24 #include <arch/elf.h> 25 26 int arch_ftrace_match(char *name) 27 { 28 return !strcmp(name, "__fentry__"); 29 } 30 31 static int is_x86_64(const struct elf *elf) 32 { 33 switch (elf->ehdr.e_machine) { 34 case EM_X86_64: 35 return 1; 36 case EM_386: 37 return 0; 38 default: 39 WARN("unexpected ELF machine type %d", elf->ehdr.e_machine); 40 return -1; 41 } 42 } 43 44 bool arch_callee_saved_reg(unsigned char reg) 45 { 46 switch (reg) { 47 case CFI_BP: 48 case CFI_BX: 49 case CFI_R12: 50 case CFI_R13: 51 case CFI_R14: 52 case CFI_R15: 53 return true; 54 55 case CFI_AX: 56 case CFI_CX: 57 case CFI_DX: 58 case CFI_SI: 59 case CFI_DI: 60 case CFI_SP: 61 case CFI_R8: 62 case CFI_R9: 63 case CFI_R10: 64 case CFI_R11: 65 case CFI_RA: 66 default: 67 return false; 68 } 69 } 70 71 unsigned long arch_dest_reloc_offset(int addend) 72 { 73 return addend + 4; 74 } 75 76 unsigned long arch_jump_destination(struct instruction *insn) 77 { 78 return insn->offset + insn->len + insn->immediate; 79 } 80 81 bool arch_pc_relative_reloc(struct reloc *reloc) 82 { 83 /* 84 * All relocation types where P (the address of the target) 85 * is included in the computation. 86 */ 87 switch (reloc->type) { 88 case R_X86_64_PC8: 89 case R_X86_64_PC16: 90 case R_X86_64_PC32: 91 case R_X86_64_PC64: 92 93 case R_X86_64_PLT32: 94 case R_X86_64_GOTPC32: 95 case R_X86_64_GOTPCREL: 96 return true; 97 98 default: 99 break; 100 } 101 102 return false; 103 } 104 105 #define ADD_OP(op) \ 106 if (!(op = calloc(1, sizeof(*op)))) \ 107 return -1; \ 108 else for (*ops_list = op, ops_list = &op->next; op; op = NULL) 109 110 /* 111 * Helpers to decode ModRM/SIB: 112 * 113 * r/m| AX CX DX BX | SP | BP | SI DI | 114 * | R8 R9 R10 R11 | R12 | R13 | R14 R15 | 115 * Mod+----------------+-----+-----+---------+ 116 * 00 | [r/m] |[SIB]|[IP+]| [r/m] | 117 * 01 | [r/m + d8] |[S+d]| [r/m + d8] | 118 * 10 | [r/m + d32] |[S+D]| [r/m + d32] | 119 * 11 | r/ m | 120 */ 121 122 #define mod_is_mem() (modrm_mod != 3) 123 #define mod_is_reg() (modrm_mod == 3) 124 125 #define is_RIP() ((modrm_rm & 7) == CFI_BP && modrm_mod == 0) 126 #define have_SIB() ((modrm_rm & 7) == CFI_SP && mod_is_mem()) 127 128 #define rm_is(reg) (have_SIB() ? \ 129 sib_base == (reg) && sib_index == CFI_SP : \ 130 modrm_rm == (reg)) 131 132 #define rm_is_mem(reg) (mod_is_mem() && !is_RIP() && rm_is(reg)) 133 #define rm_is_reg(reg) (mod_is_reg() && modrm_rm == (reg)) 134 135 static bool has_notrack_prefix(struct insn *insn) 136 { 137 int i; 138 139 for (i = 0; i < insn->prefixes.nbytes; i++) { 140 if (insn->prefixes.bytes[i] == 0x3e) 141 return true; 142 } 143 144 return false; 145 } 146 147 int arch_decode_instruction(struct objtool_file *file, const struct section *sec, 148 unsigned long offset, unsigned int maxlen, 149 struct instruction *insn) 150 { 151 struct stack_op **ops_list = &insn->stack_ops; 152 const struct elf *elf = file->elf; 153 struct insn ins; 154 int x86_64, ret; 155 unsigned char op1, op2, op3, prefix, 156 rex = 0, rex_b = 0, rex_r = 0, rex_w = 0, rex_x = 0, 157 modrm = 0, modrm_mod = 0, modrm_rm = 0, modrm_reg = 0, 158 sib = 0, /* sib_scale = 0, */ sib_index = 0, sib_base = 0; 159 struct stack_op *op = NULL; 160 struct symbol *sym; 161 u64 imm; 162 163 x86_64 = is_x86_64(elf); 164 if (x86_64 == -1) 165 return -1; 166 167 ret = insn_decode(&ins, sec->data->d_buf + offset, maxlen, 168 x86_64 ? INSN_MODE_64 : INSN_MODE_32); 169 if (ret < 0) { 170 WARN("can't decode instruction at %s:0x%lx", sec->name, offset); 171 return -1; 172 } 173 174 insn->len = ins.length; 175 insn->type = INSN_OTHER; 176 177 if (ins.vex_prefix.nbytes) 178 return 0; 179 180 prefix = ins.prefixes.bytes[0]; 181 182 op1 = ins.opcode.bytes[0]; 183 op2 = ins.opcode.bytes[1]; 184 op3 = ins.opcode.bytes[2]; 185 186 if (ins.rex_prefix.nbytes) { 187 rex = ins.rex_prefix.bytes[0]; 188 rex_w = X86_REX_W(rex) >> 3; 189 rex_r = X86_REX_R(rex) >> 2; 190 rex_x = X86_REX_X(rex) >> 1; 191 rex_b = X86_REX_B(rex); 192 } 193 194 if (ins.modrm.nbytes) { 195 modrm = ins.modrm.bytes[0]; 196 modrm_mod = X86_MODRM_MOD(modrm); 197 modrm_reg = X86_MODRM_REG(modrm) + 8*rex_r; 198 modrm_rm = X86_MODRM_RM(modrm) + 8*rex_b; 199 } 200 201 if (ins.sib.nbytes) { 202 sib = ins.sib.bytes[0]; 203 /* sib_scale = X86_SIB_SCALE(sib); */ 204 sib_index = X86_SIB_INDEX(sib) + 8*rex_x; 205 sib_base = X86_SIB_BASE(sib) + 8*rex_b; 206 } 207 208 switch (op1) { 209 210 case 0x1: 211 case 0x29: 212 if (rex_w && rm_is_reg(CFI_SP)) { 213 214 /* add/sub reg, %rsp */ 215 ADD_OP(op) { 216 op->src.type = OP_SRC_ADD; 217 op->src.reg = modrm_reg; 218 op->dest.type = OP_DEST_REG; 219 op->dest.reg = CFI_SP; 220 } 221 } 222 break; 223 224 case 0x50 ... 0x57: 225 226 /* push reg */ 227 ADD_OP(op) { 228 op->src.type = OP_SRC_REG; 229 op->src.reg = (op1 & 0x7) + 8*rex_b; 230 op->dest.type = OP_DEST_PUSH; 231 } 232 233 break; 234 235 case 0x58 ... 0x5f: 236 237 /* pop reg */ 238 ADD_OP(op) { 239 op->src.type = OP_SRC_POP; 240 op->dest.type = OP_DEST_REG; 241 op->dest.reg = (op1 & 0x7) + 8*rex_b; 242 } 243 244 break; 245 246 case 0x68: 247 case 0x6a: 248 /* push immediate */ 249 ADD_OP(op) { 250 op->src.type = OP_SRC_CONST; 251 op->dest.type = OP_DEST_PUSH; 252 } 253 break; 254 255 case 0x70 ... 0x7f: 256 insn->type = INSN_JUMP_CONDITIONAL; 257 break; 258 259 case 0x80 ... 0x83: 260 /* 261 * 1000 00sw : mod OP r/m : immediate 262 * 263 * s - sign extend immediate 264 * w - imm8 / imm32 265 * 266 * OP: 000 ADD 100 AND 267 * 001 OR 101 SUB 268 * 010 ADC 110 XOR 269 * 011 SBB 111 CMP 270 */ 271 272 /* 64bit only */ 273 if (!rex_w) 274 break; 275 276 /* %rsp target only */ 277 if (!rm_is_reg(CFI_SP)) 278 break; 279 280 imm = ins.immediate.value; 281 if (op1 & 2) { /* sign extend */ 282 if (op1 & 1) { /* imm32 */ 283 imm <<= 32; 284 imm = (s64)imm >> 32; 285 } else { /* imm8 */ 286 imm <<= 56; 287 imm = (s64)imm >> 56; 288 } 289 } 290 291 switch (modrm_reg & 7) { 292 case 5: 293 imm = -imm; 294 /* fallthrough */ 295 case 0: 296 /* add/sub imm, %rsp */ 297 ADD_OP(op) { 298 op->src.type = OP_SRC_ADD; 299 op->src.reg = CFI_SP; 300 op->src.offset = imm; 301 op->dest.type = OP_DEST_REG; 302 op->dest.reg = CFI_SP; 303 } 304 break; 305 306 case 4: 307 /* and imm, %rsp */ 308 ADD_OP(op) { 309 op->src.type = OP_SRC_AND; 310 op->src.reg = CFI_SP; 311 op->src.offset = ins.immediate.value; 312 op->dest.type = OP_DEST_REG; 313 op->dest.reg = CFI_SP; 314 } 315 break; 316 317 default: 318 /* WARN ? */ 319 break; 320 } 321 322 break; 323 324 case 0x89: 325 if (!rex_w) 326 break; 327 328 if (modrm_reg == CFI_SP) { 329 330 if (mod_is_reg()) { 331 /* mov %rsp, reg */ 332 ADD_OP(op) { 333 op->src.type = OP_SRC_REG; 334 op->src.reg = CFI_SP; 335 op->dest.type = OP_DEST_REG; 336 op->dest.reg = modrm_rm; 337 } 338 break; 339 340 } else { 341 /* skip RIP relative displacement */ 342 if (is_RIP()) 343 break; 344 345 /* skip nontrivial SIB */ 346 if (have_SIB()) { 347 modrm_rm = sib_base; 348 if (sib_index != CFI_SP) 349 break; 350 } 351 352 /* mov %rsp, disp(%reg) */ 353 ADD_OP(op) { 354 op->src.type = OP_SRC_REG; 355 op->src.reg = CFI_SP; 356 op->dest.type = OP_DEST_REG_INDIRECT; 357 op->dest.reg = modrm_rm; 358 op->dest.offset = ins.displacement.value; 359 } 360 break; 361 } 362 363 break; 364 } 365 366 if (rm_is_reg(CFI_SP)) { 367 368 /* mov reg, %rsp */ 369 ADD_OP(op) { 370 op->src.type = OP_SRC_REG; 371 op->src.reg = modrm_reg; 372 op->dest.type = OP_DEST_REG; 373 op->dest.reg = CFI_SP; 374 } 375 break; 376 } 377 378 /* fallthrough */ 379 case 0x88: 380 if (!rex_w) 381 break; 382 383 if (rm_is_mem(CFI_BP)) { 384 385 /* mov reg, disp(%rbp) */ 386 ADD_OP(op) { 387 op->src.type = OP_SRC_REG; 388 op->src.reg = modrm_reg; 389 op->dest.type = OP_DEST_REG_INDIRECT; 390 op->dest.reg = CFI_BP; 391 op->dest.offset = ins.displacement.value; 392 } 393 break; 394 } 395 396 if (rm_is_mem(CFI_SP)) { 397 398 /* mov reg, disp(%rsp) */ 399 ADD_OP(op) { 400 op->src.type = OP_SRC_REG; 401 op->src.reg = modrm_reg; 402 op->dest.type = OP_DEST_REG_INDIRECT; 403 op->dest.reg = CFI_SP; 404 op->dest.offset = ins.displacement.value; 405 } 406 break; 407 } 408 409 break; 410 411 case 0x8b: 412 if (!rex_w) 413 break; 414 415 if (rm_is_mem(CFI_BP)) { 416 417 /* mov disp(%rbp), reg */ 418 ADD_OP(op) { 419 op->src.type = OP_SRC_REG_INDIRECT; 420 op->src.reg = CFI_BP; 421 op->src.offset = ins.displacement.value; 422 op->dest.type = OP_DEST_REG; 423 op->dest.reg = modrm_reg; 424 } 425 break; 426 } 427 428 if (rm_is_mem(CFI_SP)) { 429 430 /* mov disp(%rsp), reg */ 431 ADD_OP(op) { 432 op->src.type = OP_SRC_REG_INDIRECT; 433 op->src.reg = CFI_SP; 434 op->src.offset = ins.displacement.value; 435 op->dest.type = OP_DEST_REG; 436 op->dest.reg = modrm_reg; 437 } 438 break; 439 } 440 441 break; 442 443 case 0x8d: 444 if (mod_is_reg()) { 445 WARN("invalid LEA encoding at %s:0x%lx", sec->name, offset); 446 break; 447 } 448 449 /* skip non 64bit ops */ 450 if (!rex_w) 451 break; 452 453 /* skip RIP relative displacement */ 454 if (is_RIP()) 455 break; 456 457 /* skip nontrivial SIB */ 458 if (have_SIB()) { 459 modrm_rm = sib_base; 460 if (sib_index != CFI_SP) 461 break; 462 } 463 464 /* lea disp(%src), %dst */ 465 ADD_OP(op) { 466 op->src.offset = ins.displacement.value; 467 if (!op->src.offset) { 468 /* lea (%src), %dst */ 469 op->src.type = OP_SRC_REG; 470 } else { 471 /* lea disp(%src), %dst */ 472 op->src.type = OP_SRC_ADD; 473 } 474 op->src.reg = modrm_rm; 475 op->dest.type = OP_DEST_REG; 476 op->dest.reg = modrm_reg; 477 } 478 break; 479 480 case 0x8f: 481 /* pop to mem */ 482 ADD_OP(op) { 483 op->src.type = OP_SRC_POP; 484 op->dest.type = OP_DEST_MEM; 485 } 486 break; 487 488 case 0x90: 489 insn->type = INSN_NOP; 490 break; 491 492 case 0x9c: 493 /* pushf */ 494 ADD_OP(op) { 495 op->src.type = OP_SRC_CONST; 496 op->dest.type = OP_DEST_PUSHF; 497 } 498 break; 499 500 case 0x9d: 501 /* popf */ 502 ADD_OP(op) { 503 op->src.type = OP_SRC_POPF; 504 op->dest.type = OP_DEST_MEM; 505 } 506 break; 507 508 case 0x0f: 509 510 if (op2 == 0x01) { 511 512 if (modrm == 0xca) 513 insn->type = INSN_CLAC; 514 else if (modrm == 0xcb) 515 insn->type = INSN_STAC; 516 517 } else if (op2 >= 0x80 && op2 <= 0x8f) { 518 519 insn->type = INSN_JUMP_CONDITIONAL; 520 521 } else if (op2 == 0x05 || op2 == 0x07 || op2 == 0x34 || 522 op2 == 0x35) { 523 524 /* sysenter, sysret */ 525 insn->type = INSN_CONTEXT_SWITCH; 526 527 } else if (op2 == 0x0b || op2 == 0xb9) { 528 529 /* ud2 */ 530 insn->type = INSN_BUG; 531 532 } else if (op2 == 0x0d || op2 == 0x1f) { 533 534 /* nopl/nopw */ 535 insn->type = INSN_NOP; 536 537 } else if (op2 == 0x1e) { 538 539 if (prefix == 0xf3 && (modrm == 0xfa || modrm == 0xfb)) 540 insn->type = INSN_ENDBR; 541 542 543 } else if (op2 == 0x38 && op3 == 0xf8) { 544 if (ins.prefixes.nbytes == 1 && 545 ins.prefixes.bytes[0] == 0xf2) { 546 /* ENQCMD cannot be used in the kernel. */ 547 WARN("ENQCMD instruction at %s:%lx", sec->name, 548 offset); 549 } 550 551 } else if (op2 == 0xa0 || op2 == 0xa8) { 552 553 /* push fs/gs */ 554 ADD_OP(op) { 555 op->src.type = OP_SRC_CONST; 556 op->dest.type = OP_DEST_PUSH; 557 } 558 559 } else if (op2 == 0xa1 || op2 == 0xa9) { 560 561 /* pop fs/gs */ 562 ADD_OP(op) { 563 op->src.type = OP_SRC_POP; 564 op->dest.type = OP_DEST_MEM; 565 } 566 } 567 568 break; 569 570 case 0xc9: 571 /* 572 * leave 573 * 574 * equivalent to: 575 * mov bp, sp 576 * pop bp 577 */ 578 ADD_OP(op) { 579 op->src.type = OP_SRC_REG; 580 op->src.reg = CFI_BP; 581 op->dest.type = OP_DEST_REG; 582 op->dest.reg = CFI_SP; 583 } 584 ADD_OP(op) { 585 op->src.type = OP_SRC_POP; 586 op->dest.type = OP_DEST_REG; 587 op->dest.reg = CFI_BP; 588 } 589 break; 590 591 case 0xcc: 592 /* int3 */ 593 insn->type = INSN_TRAP; 594 break; 595 596 case 0xe3: 597 /* jecxz/jrcxz */ 598 insn->type = INSN_JUMP_CONDITIONAL; 599 break; 600 601 case 0xe9: 602 case 0xeb: 603 insn->type = INSN_JUMP_UNCONDITIONAL; 604 break; 605 606 case 0xc2: 607 case 0xc3: 608 insn->type = INSN_RETURN; 609 break; 610 611 case 0xc7: /* mov imm, r/m */ 612 if (!opts.noinstr) 613 break; 614 615 if (ins.length == 3+4+4 && !strncmp(sec->name, ".init.text", 10)) { 616 struct reloc *immr, *disp; 617 struct symbol *func; 618 int idx; 619 620 immr = find_reloc_by_dest(elf, (void *)sec, offset+3); 621 disp = find_reloc_by_dest(elf, (void *)sec, offset+7); 622 623 if (!immr || strcmp(immr->sym->name, "pv_ops")) 624 break; 625 626 idx = (immr->addend + 8) / sizeof(void *); 627 628 func = disp->sym; 629 if (disp->sym->type == STT_SECTION) 630 func = find_symbol_by_offset(disp->sym->sec, disp->addend); 631 if (!func) { 632 WARN("no func for pv_ops[]"); 633 return -1; 634 } 635 636 objtool_pv_add(file, idx, func); 637 } 638 639 break; 640 641 case 0xcf: /* iret */ 642 /* 643 * Handle sync_core(), which has an IRET to self. 644 * All other IRET are in STT_NONE entry code. 645 */ 646 sym = find_symbol_containing(sec, offset); 647 if (sym && sym->type == STT_FUNC) { 648 ADD_OP(op) { 649 /* add $40, %rsp */ 650 op->src.type = OP_SRC_ADD; 651 op->src.reg = CFI_SP; 652 op->src.offset = 5*8; 653 op->dest.type = OP_DEST_REG; 654 op->dest.reg = CFI_SP; 655 } 656 break; 657 } 658 659 /* fallthrough */ 660 661 case 0xca: /* retf */ 662 case 0xcb: /* retf */ 663 insn->type = INSN_CONTEXT_SWITCH; 664 break; 665 666 case 0xe0: /* loopne */ 667 case 0xe1: /* loope */ 668 case 0xe2: /* loop */ 669 insn->type = INSN_JUMP_CONDITIONAL; 670 break; 671 672 case 0xe8: 673 insn->type = INSN_CALL; 674 /* 675 * For the impact on the stack, a CALL behaves like 676 * a PUSH of an immediate value (the return address). 677 */ 678 ADD_OP(op) { 679 op->src.type = OP_SRC_CONST; 680 op->dest.type = OP_DEST_PUSH; 681 } 682 break; 683 684 case 0xfc: 685 insn->type = INSN_CLD; 686 break; 687 688 case 0xfd: 689 insn->type = INSN_STD; 690 break; 691 692 case 0xff: 693 if (modrm_reg == 2 || modrm_reg == 3) { 694 695 insn->type = INSN_CALL_DYNAMIC; 696 if (has_notrack_prefix(&ins)) 697 WARN("notrack prefix found at %s:0x%lx", sec->name, offset); 698 699 } else if (modrm_reg == 4) { 700 701 insn->type = INSN_JUMP_DYNAMIC; 702 if (has_notrack_prefix(&ins)) 703 WARN("notrack prefix found at %s:0x%lx", sec->name, offset); 704 705 } else if (modrm_reg == 5) { 706 707 /* jmpf */ 708 insn->type = INSN_CONTEXT_SWITCH; 709 710 } else if (modrm_reg == 6) { 711 712 /* push from mem */ 713 ADD_OP(op) { 714 op->src.type = OP_SRC_CONST; 715 op->dest.type = OP_DEST_PUSH; 716 } 717 } 718 719 break; 720 721 default: 722 break; 723 } 724 725 insn->immediate = ins.immediate.nbytes ? ins.immediate.value : 0; 726 727 return 0; 728 } 729 730 void arch_initial_func_cfi_state(struct cfi_init_state *state) 731 { 732 int i; 733 734 for (i = 0; i < CFI_NUM_REGS; i++) { 735 state->regs[i].base = CFI_UNDEFINED; 736 state->regs[i].offset = 0; 737 } 738 739 /* initial CFA (call frame address) */ 740 state->cfa.base = CFI_SP; 741 state->cfa.offset = 8; 742 743 /* initial RA (return address) */ 744 state->regs[CFI_RA].base = CFI_CFA; 745 state->regs[CFI_RA].offset = -8; 746 } 747 748 const char *arch_nop_insn(int len) 749 { 750 static const char nops[5][5] = { 751 { BYTES_NOP1 }, 752 { BYTES_NOP2 }, 753 { BYTES_NOP3 }, 754 { BYTES_NOP4 }, 755 { BYTES_NOP5 }, 756 }; 757 758 if (len < 1 || len > 5) { 759 WARN("invalid NOP size: %d\n", len); 760 return NULL; 761 } 762 763 return nops[len-1]; 764 } 765 766 #define BYTE_RET 0xC3 767 768 const char *arch_ret_insn(int len) 769 { 770 static const char ret[5][5] = { 771 { BYTE_RET }, 772 { BYTE_RET, 0xcc }, 773 { BYTE_RET, 0xcc, BYTES_NOP1 }, 774 { BYTE_RET, 0xcc, BYTES_NOP2 }, 775 { BYTE_RET, 0xcc, BYTES_NOP3 }, 776 }; 777 778 if (len < 1 || len > 5) { 779 WARN("invalid RET size: %d\n", len); 780 return NULL; 781 } 782 783 return ret[len-1]; 784 } 785 786 int arch_decode_hint_reg(u8 sp_reg, int *base) 787 { 788 switch (sp_reg) { 789 case ORC_REG_UNDEFINED: 790 *base = CFI_UNDEFINED; 791 break; 792 case ORC_REG_SP: 793 *base = CFI_SP; 794 break; 795 case ORC_REG_BP: 796 *base = CFI_BP; 797 break; 798 case ORC_REG_SP_INDIRECT: 799 *base = CFI_SP_INDIRECT; 800 break; 801 case ORC_REG_R10: 802 *base = CFI_R10; 803 break; 804 case ORC_REG_R13: 805 *base = CFI_R13; 806 break; 807 case ORC_REG_DI: 808 *base = CFI_DI; 809 break; 810 case ORC_REG_DX: 811 *base = CFI_DX; 812 break; 813 default: 814 return -1; 815 } 816 817 return 0; 818 } 819 820 bool arch_is_retpoline(struct symbol *sym) 821 { 822 return !strncmp(sym->name, "__x86_indirect_", 15); 823 } 824 825 bool arch_is_rethunk(struct symbol *sym) 826 { 827 return !strcmp(sym->name, "__x86_return_thunk"); 828 } 829