arch/x86/lib/insn.c

   1 /*
   2  * x86 instruction analysis
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (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, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  *
  18  * Copyright (C) IBM Corporation, 2002, 2004, 2009
  19  */
  20
  21 #ifdef __KERNEL__
  22 #include <linux/string.h>
  23 #else
  24 #include <string.h>
  25 #endif
  26 #include <asm/inat.h>
  27 #include <asm/insn.h>
  28
  29 /* Verify next sizeof(t) bytes can be on the same instruction */
  30 #define validate_next(t, insn, n)       \
  31         ((insn)->next_byte + sizeof(t) + n <= (insn)->end_kaddr)
  32
  33 #define __get_next(t, insn)     \
  34         ({ t r = *(t*)insn->next_byte; insn->next_byte += sizeof(t); r; })
  35
  36 #define __peek_nbyte_next(t, insn, n)   \
  37         ({ t r = *(t*)((insn)->next_byte + n); r; })
  38
  39 #define get_next(t, insn)       \
  40         ({ if (unlikely(!validate_next(t, insn, 0))) goto err_out; __get_next(t, insn); })
  41
  42 #define peek_nbyte_next(t, insn, n)     \
  43         ({ if (unlikely(!validate_next(t, insn, n))) goto err_out; __peek_nbyte_next(t, insn, n); })
  44
  45 #define peek_next(t, insn)      peek_nbyte_next(t, insn, 0)
  46
  47 /**
  48  * insn_init() - initialize struct insn
  49  * @insn:       &struct insn to be initialized
  50  * @kaddr:      address (in kernel memory) of instruction (or copy thereof)
  51  * @x86_64:     !0 for 64-bit kernel or 64-bit app
  52  */
  53 void insn_init(struct insn *insn, const void *kaddr, int buf_len, int x86_64)
  54 {
  55         /*
  56          * Instructions longer than MAX_INSN_SIZE (15 bytes) are invalid
  57          * even if the input buffer is long enough to hold them.
  58          */
  59         if (buf_len > MAX_INSN_SIZE)
  60                 buf_len = MAX_INSN_SIZE;
  61
  62         memset(insn, 0, sizeof(*insn));
  63         insn->kaddr = kaddr;
  64         insn->end_kaddr = kaddr + buf_len;
  65         insn->next_byte = kaddr;
  66         insn->x86_64 = x86_64 ? 1 : 0;
  67         insn->opnd_bytes = 4;
  68         if (x86_64)
  69                 insn->addr_bytes = 8;
  70         else
  71                 insn->addr_bytes = 4;
  72 }
  73
  74 /**
  75  * insn_get_prefixes - scan x86 instruction prefix bytes
  76  * @insn:       &struct insn containing instruction
  77  *
  78  * Populates the @insn->prefixes bitmap, and updates @insn->next_byte
  79  * to point to the (first) opcode.  No effect if @insn->prefixes.got
  80  * is already set.
  81  */
  82 void insn_get_prefixes(struct insn *insn)
  83 {
  84         struct insn_field *prefixes = &insn->prefixes;
  85         insn_attr_t attr;
  86         insn_byte_t b, lb;
  87         int i, nb;
  88
  89         if (prefixes->got)
  90                 return;
  91
  92         nb = 0;
  93         lb = 0;
  94         b = peek_next(insn_byte_t, insn);
  95         attr = inat_get_opcode_attribute(b);
  96         while (inat_is_legacy_prefix(attr)) {
  97                 /* Skip if same prefix */
  98                 for (i = 0; i < nb; i++)
  99                         if (prefixes->bytes[i] == b)
 100                                 goto found;
 101                 if (nb == 4)
 102                         /* Invalid instruction */
 103                         break;
 104                 prefixes->bytes[nb++] = b;
 105                 if (inat_is_address_size_prefix(attr)) {
 106                         /* address size switches 2/4 or 4/8 */
 107                         if (insn->x86_64)
 108                                 insn->addr_bytes ^= 12;
 109                         else
 110                                 insn->addr_bytes ^= 6;
 111                 } else if (inat_is_operand_size_prefix(attr)) {
 112                         /* oprand size switches 2/4 */
 113                         insn->opnd_bytes ^= 6;
 114                 }
 115 found:
 116                 prefixes->nbytes++;
 117                 insn->next_byte++;
 118                 lb = b;
 119                 b = peek_next(insn_byte_t, insn);
 120                 attr = inat_get_opcode_attribute(b);
 121         }
 122         /* Set the last prefix */
 123         if (lb && lb != insn->prefixes.bytes[3]) {
 124                 if (unlikely(insn->prefixes.bytes[3])) {
 125                         /* Swap the last prefix */
 126                         b = insn->prefixes.bytes[3];
 127                         for (i = 0; i < nb; i++)
 128                                 if (prefixes->bytes[i] == lb)
 129                                         prefixes->bytes[i] = b;
 130                 }
 131                 insn->prefixes.bytes[3] = lb;
 132         }
 133
 134         /* Decode REX prefix */
 135         if (insn->x86_64) {
 136                 b = peek_next(insn_byte_t, insn);
 137                 attr = inat_get_opcode_attribute(b);
 138                 if (inat_is_rex_prefix(attr)) {
 139                         insn->rex_prefix.value = b;
 140                         insn->rex_prefix.nbytes = 1;
 141                         insn->next_byte++;
 142                         if (X86_REX_W(b))
 143                                 /* REX.W overrides opnd_size */
 144                                 insn->opnd_bytes = 8;
 145                 }
 146         }
 147         insn->rex_prefix.got = 1;
 148
 149         /* Decode VEX prefix */
 150         b = peek_next(insn_byte_t, insn);
 151         attr = inat_get_opcode_attribute(b);
 152         if (inat_is_vex_prefix(attr)) {
 153                 insn_byte_t b2 = peek_nbyte_next(insn_byte_t, insn, 1);
 154                 if (!insn->x86_64) {
 155                         /*
 156                          * In 32-bits mode, if the [7:6] bits (mod bits of
 157                          * ModRM) on the second byte are not 11b, it is
 158                          * LDS or LES or BOUND.
 159                          */
 160                         if (X86_MODRM_MOD(b2) != 3)
 161                                 goto vex_end;
 162                 }
 163                 insn->vex_prefix.bytes[0] = b;
 164                 insn->vex_prefix.bytes[1] = b2;
 165                 if (inat_is_evex_prefix(attr)) {
 166                         b2 = peek_nbyte_next(insn_byte_t, insn, 2);
 167                         insn->vex_prefix.bytes[2] = b2;
 168                         b2 = peek_nbyte_next(insn_byte_t, insn, 3);
 169                         insn->vex_prefix.bytes[3] = b2;
 170                         insn->vex_prefix.nbytes = 4;
 171                         insn->next_byte += 4;
 172                         if (insn->x86_64 && X86_VEX_W(b2))
 173                                 /* VEX.W overrides opnd_size */
 174                                 insn->opnd_bytes = 8;
 175                 } else if (inat_is_vex3_prefix(attr)) {
 176                         b2 = peek_nbyte_next(insn_byte_t, insn, 2);
 177                         insn->vex_prefix.bytes[2] = b2;
 178                         insn->vex_prefix.nbytes = 3;
 179                         insn->next_byte += 3;
 180                         if (insn->x86_64 && X86_VEX_W(b2))
 181                                 /* VEX.W overrides opnd_size */
 182                                 insn->opnd_bytes = 8;
 183                 } else {
 184                         /*
 185                          * For VEX2, fake VEX3-like byte#2.
 186                          * Makes it easier to decode vex.W, vex.vvvv,
 187                          * vex.L and vex.pp. Masking with 0x7f sets vex.W == 0.
 188                          */
 189                         insn->vex_prefix.bytes[2] = b2 & 0x7f;
 190                         insn->vex_prefix.nbytes = 2;
 191                         insn->next_byte += 2;
 192                 }
 193         }
 194 vex_end:
 195         insn->vex_prefix.got = 1;
 196
 197         prefixes->got = 1;
 198
 199 err_out:
 200         return;
 201 }
 202
 203 /**
 204  * insn_get_opcode - collect opcode(s)
 205  * @insn:       &struct insn containing instruction
 206  *
 207  * Populates @insn->opcode, updates @insn->next_byte to point past the
 208  * opcode byte(s), and set @insn->attr (except for groups).
 209  * If necessary, first collects any preceding (prefix) bytes.
 210  * Sets @insn->opcode.value = opcode1.  No effect if @insn->opcode.got
 211  * is already 1.
 212  */
 213 void insn_get_opcode(struct insn *insn)
 214 {
 215         struct insn_field *opcode = &insn->opcode;
 216         insn_byte_t op;
 217         int pfx_id;
 218         if (opcode->got)
 219                 return;
 220         if (!insn->prefixes.got)
 221                 insn_get_prefixes(insn);
 222
 223         /* Get first opcode */
 224         op = get_next(insn_byte_t, insn);
 225         opcode->bytes[0] = op;
 226         opcode->nbytes = 1;
 227
 228         /* Check if there is VEX prefix or not */
 229         if (insn_is_avx(insn)) {
 230                 insn_byte_t m, p;
 231                 m = insn_vex_m_bits(insn);
 232                 p = insn_vex_p_bits(insn);
 233                 insn->attr = inat_get_avx_attribute(op, m, p);
 234                 if ((inat_must_evex(insn->attr) && !insn_is_evex(insn)) ||
 235                     (!inat_accept_vex(insn->attr) &&
 236                      !inat_is_group(insn->attr)))
 237                         insn->attr = 0; /* This instruction is bad */
 238                 goto end;       /* VEX has only 1 byte for opcode */
 239         }
 240
 241         insn->attr = inat_get_opcode_attribute(op);
 242         while (inat_is_escape(insn->attr)) {
 243                 /* Get escaped opcode */
 244                 op = get_next(insn_byte_t, insn);
 245                 opcode->bytes[opcode->nbytes++] = op;
 246                 pfx_id = insn_last_prefix_id(insn);
 247                 insn->attr = inat_get_escape_attribute(op, pfx_id, insn->attr);
 248         }
 249         if (inat_must_vex(insn->attr))
 250                 insn->attr = 0; /* This instruction is bad */
 251 end:
 252         opcode->got = 1;
 253
 254 err_out:
 255         return;
 256 }
 257
 258 /**
 259  * insn_get_modrm - collect ModRM byte, if any
 260  * @insn:       &struct insn containing instruction
 261  *
 262  * Populates @insn->modrm and updates @insn->next_byte to point past the
 263  * ModRM byte, if any.  If necessary, first collects the preceding bytes
 264  * (prefixes and opcode(s)).  No effect if @insn->modrm.got is already 1.
 265  */
 266 void insn_get_modrm(struct insn *insn)
 267 {
 268         struct insn_field *modrm = &insn->modrm;
 269         insn_byte_t pfx_id, mod;
 270         if (modrm->got)
 271                 return;
 272         if (!insn->opcode.got)
 273                 insn_get_opcode(insn);
 274
 275         if (inat_has_modrm(insn->attr)) {
 276                 mod = get_next(insn_byte_t, insn);
 277                 modrm->value = mod;
 278                 modrm->nbytes = 1;
 279                 if (inat_is_group(insn->attr)) {
 280                         pfx_id = insn_last_prefix_id(insn);
 281                         insn->attr = inat_get_group_attribute(mod, pfx_id,
 282                                                               insn->attr);
 283                         if (insn_is_avx(insn) && !inat_accept_vex(insn->attr))
 284                                 insn->attr = 0; /* This is bad */
 285                 }
 286         }
 287
 288         if (insn->x86_64 && inat_is_force64(insn->attr))
 289                 insn->opnd_bytes = 8;
 290         modrm->got = 1;
 291
 292 err_out:
 293         return;
 294 }
 295
 296
 297 /**
 298  * insn_rip_relative() - Does instruction use RIP-relative addressing mode?
 299  * @insn:       &struct insn containing instruction
 300  *
 301  * If necessary, first collects the instruction up to and including the
 302  * ModRM byte.  No effect if @insn->x86_64 is 0.
 303  */
 304 int insn_rip_relative(struct insn *insn)
 305 {
 306         struct insn_field *modrm = &insn->modrm;
 307
 308         if (!insn->x86_64)
 309                 return 0;
 310         if (!modrm->got)
 311                 insn_get_modrm(insn);
 312         /*
 313          * For rip-relative instructions, the mod field (top 2 bits)
 314          * is zero and the r/m field (bottom 3 bits) is 0x5.
 315          */
 316         return (modrm->nbytes && (modrm->value & 0xc7) == 0x5);
 317 }
 318
 319 /**
 320  * insn_get_sib() - Get the SIB byte of instruction
 321  * @insn:       &struct insn containing instruction
 322  *
 323  * If necessary, first collects the instruction up to and including the
 324  * ModRM byte.
 325  */
 326 void insn_get_sib(struct insn *insn)
 327 {
 328         insn_byte_t modrm;
 329
 330         if (insn->sib.got)
 331                 return;
 332         if (!insn->modrm.got)
 333                 insn_get_modrm(insn);
 334         if (insn->modrm.nbytes) {
 335                 modrm = (insn_byte_t)insn->modrm.value;
 336                 if (insn->addr_bytes != 2 &&
 337                     X86_MODRM_MOD(modrm) != 3 && X86_MODRM_RM(modrm) == 4) {
 338                         insn->sib.value = get_next(insn_byte_t, insn);
 339                         insn->sib.nbytes = 1;
 340                 }
 341         }
 342         insn->sib.got = 1;
 343
 344 err_out:
 345         return;
 346 }
 347
 348
 349 /**
 350  * insn_get_displacement() - Get the displacement of instruction
 351  * @insn:       &struct insn containing instruction
 352  *
 353  * If necessary, first collects the instruction up to and including the
 354  * SIB byte.
 355  * Displacement value is sign-expanded.
 356  */
 357 void insn_get_displacement(struct insn *insn)
 358 {
 359         insn_byte_t mod, rm, base;
 360
 361         if (insn->displacement.got)
 362                 return;
 363         if (!insn->sib.got)
 364                 insn_get_sib(insn);
 365         if (insn->modrm.nbytes) {
 366                 /*
 367                  * Interpreting the modrm byte:
 368                  * mod = 00 - no displacement fields (exceptions below)
 369                  * mod = 01 - 1-byte displacement field
 370                  * mod = 10 - displacement field is 4 bytes, or 2 bytes if
 371                  *      address size = 2 (0x67 prefix in 32-bit mode)
 372                  * mod = 11 - no memory operand
 373                  *
 374                  * If address size = 2...
 375                  * mod = 00, r/m = 110 - displacement field is 2 bytes
 376                  *
 377                  * If address size != 2...
 378                  * mod != 11, r/m = 100 - SIB byte exists
 379                  * mod = 00, SIB base = 101 - displacement field is 4 bytes
 380                  * mod = 00, r/m = 101 - rip-relative addressing, displacement
 381                  *      field is 4 bytes
 382                  */
 383                 mod = X86_MODRM_MOD(insn->modrm.value);
 384                 rm = X86_MODRM_RM(insn->modrm.value);
 385                 base = X86_SIB_BASE(insn->sib.value);
 386                 if (mod == 3)
 387                         goto out;
 388                 if (mod == 1) {
 389                         insn->displacement.value = get_next(signed char, insn);
 390                         insn->displacement.nbytes = 1;
 391                 } else if (insn->addr_bytes == 2) {
 392                         if ((mod == 0 && rm == 6) || mod == 2) {
 393                                 insn->displacement.value =
 394                                          get_next(short, insn);
 395                                 insn->displacement.nbytes = 2;
 396                         }
 397                 } else {
 398                         if ((mod == 0 && rm == 5) || mod == 2 ||
 399                             (mod == 0 && base == 5)) {
 400                                 insn->displacement.value = get_next(int, insn);
 401                                 insn->displacement.nbytes = 4;
 402                         }
 403                 }
 404         }
 405 out:
 406         insn->displacement.got = 1;
 407
 408 err_out:
 409         return;
 410 }
 411
 412 /* Decode moffset16/32/64. Return 0 if failed */
 413 static int __get_moffset(struct insn *insn)
 414 {
 415         switch (insn->addr_bytes) {
 416         case 2:
 417                 insn->moffset1.value = get_next(short, insn);
 418                 insn->moffset1.nbytes = 2;
 419                 break;
 420         case 4:
 421                 insn->moffset1.value = get_next(int, insn);
 422                 insn->moffset1.nbytes = 4;
 423                 break;
 424         case 8:
 425                 insn->moffset1.value = get_next(int, insn);
 426                 insn->moffset1.nbytes = 4;
 427                 insn->moffset2.value = get_next(int, insn);
 428                 insn->moffset2.nbytes = 4;
 429                 break;
 430         default:        /* opnd_bytes must be modified manually */
 431                 goto err_out;
 432         }
 433         insn->moffset1.got = insn->moffset2.got = 1;
 434
 435         return 1;
 436
 437 err_out:
 438         return 0;
 439 }
 440
 441 /* Decode imm v32(Iz). Return 0 if failed */
 442 static int __get_immv32(struct insn *insn)
 443 {
 444         switch (insn->opnd_bytes) {
 445         case 2:
 446                 insn->immediate.value = get_next(short, insn);
 447                 insn->immediate.nbytes = 2;
 448                 break;
 449         case 4:
 450         case 8:
 451                 insn->immediate.value = get_next(int, insn);
 452                 insn->immediate.nbytes = 4;
 453                 break;
 454         default:        /* opnd_bytes must be modified manually */
 455                 goto err_out;
 456         }
 457
 458         return 1;
 459
 460 err_out:
 461         return 0;
 462 }
 463
 464 /* Decode imm v64(Iv/Ov), Return 0 if failed */
 465 static int __get_immv(struct insn *insn)
 466 {
 467         switch (insn->opnd_bytes) {
 468         case 2:
 469                 insn->immediate1.value = get_next(short, insn);
 470                 insn->immediate1.nbytes = 2;
 471                 break;
 472         case 4:
 473                 insn->immediate1.value = get_next(int, insn);
 474                 insn->immediate1.nbytes = 4;
 475                 break;
 476         case 8:
 477                 insn->immediate1.value = get_next(int, insn);
 478                 insn->immediate1.nbytes = 4;
 479                 insn->immediate2.value = get_next(int, insn);
 480                 insn->immediate2.nbytes = 4;
 481                 break;
 482         default:        /* opnd_bytes must be modified manually */
 483                 goto err_out;
 484         }
 485         insn->immediate1.got = insn->immediate2.got = 1;
 486
 487         return 1;
 488 err_out:
 489         return 0;
 490 }
 491
 492 /* Decode ptr16:16/32(Ap) */
 493 static int __get_immptr(struct insn *insn)
 494 {
 495         switch (insn->opnd_bytes) {
 496         case 2:
 497                 insn->immediate1.value = get_next(short, insn);
 498                 insn->immediate1.nbytes = 2;
 499                 break;
 500         case 4:
 501                 insn->immediate1.value = get_next(int, insn);
 502                 insn->immediate1.nbytes = 4;
 503                 break;
 504         case 8:
 505                 /* ptr16:64 is not exist (no segment) */
 506                 return 0;
 507         default:        /* opnd_bytes must be modified manually */
 508                 goto err_out;
 509         }
 510         insn->immediate2.value = get_next(unsigned short, insn);
 511         insn->immediate2.nbytes = 2;
 512         insn->immediate1.got = insn->immediate2.got = 1;
 513
 514         return 1;
 515 err_out:
 516         return 0;
 517 }
 518
 519 /**
 520  * insn_get_immediate() - Get the immediates of instruction
 521  * @insn:       &struct insn containing instruction
 522  *
 523  * If necessary, first collects the instruction up to and including the
 524  * displacement bytes.
 525  * Basically, most of immediates are sign-expanded. Unsigned-value can be
 526  * get by bit masking with ((1 << (nbytes * 8)) - 1)
 527  */
 528 void insn_get_immediate(struct insn *insn)
 529 {
 530         if (insn->immediate.got)
 531                 return;
 532         if (!insn->displacement.got)
 533                 insn_get_displacement(insn);
 534
 535         if (inat_has_moffset(insn->attr)) {
 536                 if (!__get_moffset(insn))
 537                         goto err_out;
 538                 goto done;
 539         }
 540
 541         if (!inat_has_immediate(insn->attr))
 542                 /* no immediates */
 543                 goto done;
 544
 545         switch (inat_immediate_size(insn->attr)) {
 546         case INAT_IMM_BYTE:
 547                 insn->immediate.value = get_next(signed char, insn);
 548                 insn->immediate.nbytes = 1;
 549                 break;
 550         case INAT_IMM_WORD:
 551                 insn->immediate.value = get_next(short, insn);
 552                 insn->immediate.nbytes = 2;
 553                 break;
 554         case INAT_IMM_DWORD:
 555                 insn->immediate.value = get_next(int, insn);
 556                 insn->immediate.nbytes = 4;
 557                 break;
 558         case INAT_IMM_QWORD:
 559                 insn->immediate1.value = get_next(int, insn);
 560                 insn->immediate1.nbytes = 4;
 561                 insn->immediate2.value = get_next(int, insn);
 562                 insn->immediate2.nbytes = 4;
 563                 break;
 564         case INAT_IMM_PTR:
 565                 if (!__get_immptr(insn))
 566                         goto err_out;
 567                 break;
 568         case INAT_IMM_VWORD32:
 569                 if (!__get_immv32(insn))
 570                         goto err_out;
 571                 break;
 572         case INAT_IMM_VWORD:
 573                 if (!__get_immv(insn))
 574                         goto err_out;
 575                 break;
 576         default:
 577                 /* Here, insn must have an immediate, but failed */
 578                 goto err_out;
 579         }
 580         if (inat_has_second_immediate(insn->attr)) {
 581                 insn->immediate2.value = get_next(signed char, insn);
 582                 insn->immediate2.nbytes = 1;
 583         }
 584 done:
 585         insn->immediate.got = 1;
 586
 587 err_out:
 588         return;
 589 }
 590
 591 /**
 592  * insn_get_length() - Get the length of instruction
 593  * @insn:       &struct insn containing instruction
 594  *
 595  * If necessary, first collects the instruction up to and including the
 596  * immediates bytes.
 597  */
 598 void insn_get_length(struct insn *insn)
 599 {
 600         if (insn->length)
 601                 return;
 602         if (!insn->immediate.got)
 603                 insn_get_immediate(insn);
 604         insn->length = (unsigned char)((unsigned long)insn->next_byte
 605                                      - (unsigned long)insn->kaddr);
 606 }