disasm.c

   1 /* disasm.c   where all the _work_ gets done in the Netwide Disassembler
   2  *
   3  * The Netwide Assembler is copyright (C) 1996 Simon Tatham and
   4  * Julian Hall. All rights reserved. The software is
   5  * redistributable under the licence given in the file "Licence"
   6  * distributed in the NASM archive.
   7  *
   8  * initial version 27/iii/95 by Simon Tatham
   9  */
  10
  11 #include "compiler.h"
  12
  13 #include <stdio.h>
  14 #include <string.h>
  15 #include <limits.h>
  16 #include <inttypes.h>
  17
  18 #include "nasm.h"
  19 #include "disasm.h"
  20 #include "sync.h"
  21 #include "insns.h"
  22
  23 #include "names.c"
  24
  25 /*
  26  * Flags that go into the `segment' field of `insn' structures
  27  * during disassembly.
  28  */
  29 #define SEG_RELATIVE      1
  30 #define SEG_32BIT         2
  31 #define SEG_RMREG         4
  32 #define SEG_DISP8         8
  33 #define SEG_DISP16       16
  34 #define SEG_DISP32       32
  35 #define SEG_NODISP       64
  36 #define SEG_SIGNED      128
  37 #define SEG_64BIT       256
  38
  39 #include "regdis.c"
  40
  41 /*
  42  * Prefix information
  43  */
  44 struct prefix_info {
  45     uint8_t osize;              /* Operand size */
  46     uint8_t asize;              /* Address size */
  47     uint8_t osp;                /* Operand size prefix present */
  48     uint8_t asp;                /* Address size prefix present */
  49     uint8_t rep;                /* Rep prefix present */
  50     uint8_t seg;                /* Segment override prefix present */
  51     uint8_t lock;               /* Lock prefix present */
  52     uint8_t rex;                /* Rex prefix present */
  53 };
  54
  55 #define getu8(x) (*(uint8_t *)(x))
  56 #if X86_MEMORY
  57 /* Littleendian CPU which can handle unaligned references */
  58 #define getu16(x) (*(uint16_t *)(x))
  59 #define getu32(x) (*(uint32_t *)(x))
  60 #define getu64(x) (*(uint64_t *)(x))
  61 #else
  62 static uint16_t getu16(uint8_t *data)
  63 {
  64     return (uint16_t)data[0] + ((uint16_t)data[1] << 8);
  65 }
  66 static uint32_t getu32(uint8_t *data)
  67 {
  68     return (uint32_t)getu16(data) + ((uint32_t)getu16(data+2) << 16);
  69 }
  70 static uint64_t getu64(uint8_t *data)
  71 {
  72     return (uint64_t)getu32(data) + ((uint64_t)getu32(data+4) << 32);
  73 }
  74 #endif
  75
  76 #define gets8(x) ((int8_t)getu8(x))
  77 #define gets16(x) ((int16_t)getu16(x))
  78 #define gets32(x) ((int32_t)getu32(x))
  79 #define gets64(x) ((int64_t)getu64(x))
  80
  81 /* Important: regval must already have been adjusted for rex extensions */
  82 static enum reg_enum whichreg(int32_t regflags, int regval, int rex)
  83 {
  84     if (!(regflags & (REGISTER|REGMEM)))
  85         return 0;               /* Registers not permissible?! */
  86
  87     regflags |= REGISTER;
  88
  89     if (!(REG_AL & ~regflags))
  90         return R_AL;
  91     if (!(REG_AX & ~regflags))
  92         return R_AX;
  93     if (!(REG_EAX & ~regflags))
  94         return R_EAX;
  95     if (!(REG_RAX & ~regflags))
  96         return R_RAX;
  97     if (!(REG_DL & ~regflags))
  98         return R_DL;
  99     if (!(REG_DX & ~regflags))
 100         return R_DX;
 101     if (!(REG_EDX & ~regflags))
 102         return R_EDX;
 103     if (!(REG_RDX & ~regflags))
 104         return R_RDX;
 105     if (!(REG_CL & ~regflags))
 106         return R_CL;
 107     if (!(REG_CX & ~regflags))
 108         return R_CX;
 109     if (!(REG_ECX & ~regflags))
 110         return R_ECX;
 111     if (!(REG_RCX & ~regflags))
 112         return R_RCX;
 113     if (!(FPU0 & ~regflags))
 114         return R_ST0;
 115     if (!(REG_CS & ~regflags))
 116         return (regval == 1) ? R_CS : 0;
 117     if (!(REG_DESS & ~regflags))
 118         return (regval == 0 || regval == 2
 119                 || regval == 3 ? rd_sreg[regval] : 0);
 120     if (!(REG_FSGS & ~regflags))
 121         return (regval == 4 || regval == 5 ? rd_sreg[regval] : 0);
 122     if (!(REG_SEG67 & ~regflags))
 123         return (regval == 6 || regval == 7 ? rd_sreg[regval] : 0);
 124
 125     /* All the entries below look up regval in an 16-entry array */
 126     if (regval < 0 || regval > 15)
 127         return 0;
 128
 129     if (!(REG8 & ~regflags)) {
 130         if (rex & REX_P)
 131             return rd_reg8_rex[regval];
 132         else
 133             return rd_reg8[regval];
 134     }
 135     if (!(REG16 & ~regflags))
 136         return rd_reg16[regval];
 137     if (!(REG32 & ~regflags))
 138         return rd_reg32[regval];
 139     if (!(REG64 & ~regflags))
 140         return rd_reg64[regval];
 141     if (!(REG_SREG & ~regflags))
 142         return rd_sreg[regval & 7]; /* Ignore REX */
 143     if (!(REG_CREG & ~regflags))
 144         return rd_creg[regval];
 145     if (!(REG_DREG & ~regflags))
 146         return rd_dreg[regval];
 147     if (!(REG_TREG & ~regflags)) {
 148         if (rex & REX_P)
 149             return 0;           /* TR registers are ill-defined with rex */
 150         return rd_treg[regval];
 151     }
 152     if (!(FPUREG & ~regflags))
 153         return rd_fpureg[regval & 7]; /* Ignore REX */
 154     if (!(MMXREG & ~regflags))
 155         return rd_mmxreg[regval & 7]; /* Ignore REX */
 156     if (!(XMMREG & ~regflags))
 157         return rd_xmmreg[regval];
 158
 159     return 0;
 160 }
 161
 162 static const char *whichcond(int condval)
 163 {
 164     static int conds[] = {
 165         C_O, C_NO, C_C, C_NC, C_Z, C_NZ, C_NA, C_A,
 166         C_S, C_NS, C_PE, C_PO, C_L, C_NL, C_NG, C_G
 167     };
 168     return conditions[conds[condval]];
 169 }
 170
 171 /*
 172  * Process a DREX suffix
 173  */
 174 static uint8_t *do_drex(uint8_t *data, insn *ins)
 175 {
 176     uint8_t drex = *data++;
 177     operand *dst = &ins->oprs[ins->drexdst];
 178
 179     if ((drex & 8) != ((ins->rex & REX_OC) ? 8 : 0))
 180         return NULL;    /* OC0 mismatch */
 181     ins->rex = (ins->rex & ~7) | (drex & 7);
 182
 183     dst->segment = SEG_RMREG;
 184     dst->basereg = drex >> 4;
 185     return data;
 186 }
 187
 188
 189 /*
 190  * Process an effective address (ModRM) specification.
 191  */
 192 static uint8_t *do_ea(uint8_t *data, int modrm, int asize,
 193                       int segsize, operand * op, insn *ins)
 194 {
 195     int mod, rm, scale, index, base;
 196     int rex;
 197     uint8_t sib = 0;
 198
 199     mod = (modrm >> 6) & 03;
 200     rm = modrm & 07;
 201
 202     if (mod != 3 && rm == 4 && asize != 16)
 203         sib = *data++;
 204
 205     if (ins->rex & REX_D) {
 206         data = do_drex(data, ins);
 207         if (!data)
 208             return NULL;
 209     }
 210     rex = ins->rex;
 211
 212     if (mod == 3) {             /* pure register version */
 213         op->basereg = rm+(rex & REX_B ? 8 : 0);
 214         op->segment |= SEG_RMREG;
 215         return data;
 216     }
 217
 218     op->disp_size = 0;
 219     op->eaflags = 0;
 220
 221     if (asize == 16) {
 222         /*
 223          * <mod> specifies the displacement size (none, byte or
 224          * word), and <rm> specifies the register combination.
 225          * Exception: mod=0,rm=6 does not specify [BP] as one might
 226          * expect, but instead specifies [disp16].
 227          */
 228         op->indexreg = op->basereg = -1;
 229         op->scale = 1;          /* always, in 16 bits */
 230         switch (rm) {
 231         case 0:
 232             op->basereg = R_BX;
 233             op->indexreg = R_SI;
 234             break;
 235         case 1:
 236             op->basereg = R_BX;
 237             op->indexreg = R_DI;
 238             break;
 239         case 2:
 240             op->basereg = R_BP;
 241             op->indexreg = R_SI;
 242             break;
 243         case 3:
 244             op->basereg = R_BP;
 245             op->indexreg = R_DI;
 246             break;
 247         case 4:
 248             op->basereg = R_SI;
 249             break;
 250         case 5:
 251             op->basereg = R_DI;
 252             break;
 253         case 6:
 254             op->basereg = R_BP;
 255             break;
 256         case 7:
 257             op->basereg = R_BX;
 258             break;
 259         }
 260         if (rm == 6 && mod == 0) {      /* special case */
 261             op->basereg = -1;
 262             if (segsize != 16)
 263                 op->disp_size = 16;
 264             mod = 2;            /* fake disp16 */
 265         }
 266         switch (mod) {
 267         case 0:
 268             op->segment |= SEG_NODISP;
 269             break;
 270         case 1:
 271             op->segment |= SEG_DISP8;
 272             op->offset = (int8_t)*data++;
 273             break;
 274         case 2:
 275             op->segment |= SEG_DISP16;
 276             op->offset = *data++;
 277             op->offset |= ((unsigned)*data++) << 8;
 278             break;
 279         }
 280         return data;
 281     } else {
 282         /*
 283          * Once again, <mod> specifies displacement size (this time
 284          * none, byte or *dword*), while <rm> specifies the base
 285          * register. Again, [EBP] is missing, replaced by a pure
 286          * disp32 (this time that's mod=0,rm=*5*) in 32-bit mode,
 287          * and RIP-relative addressing in 64-bit mode.
 288          *
 289          * However, rm=4
 290          * indicates not a single base register, but instead the
 291          * presence of a SIB byte...
 292          */
 293         int a64 = asize == 64;
 294
 295         op->indexreg = -1;
 296
 297         if (a64)
 298             op->basereg = rd_reg64[rm | ((rex & REX_B) ? 8 : 0)];
 299         else
 300             op->basereg = rd_reg32[rm | ((rex & REX_B) ? 8 : 0)];
 301
 302         if (rm == 5 && mod == 0) {
 303             if (segsize == 64) {
 304                 op->eaflags |= EAF_REL;
 305                 op->segment |= SEG_RELATIVE;
 306                 mod = 2;        /* fake disp32 */
 307             }
 308
 309             if (asize != 64)
 310                 op->disp_size = asize;
 311
 312             op->basereg = -1;
 313             mod = 2;            /* fake disp32 */
 314         }
 315
 316         if (rm == 4) {          /* process SIB */
 317             scale = (sib >> 6) & 03;
 318             index = (sib >> 3) & 07;
 319             base = sib & 07;
 320
 321             op->scale = 1 << scale;
 322
 323             if (index == 4)
 324                 op->indexreg = -1; /* ESP/RSP/R12 cannot be an index */
 325             else if (a64)
 326                 op->indexreg = rd_reg64[index | ((rex & REX_X) ? 8 : 0)];
 327             else
 328                 op->indexreg = rd_reg64[index | ((rex & REX_X) ? 8 : 0)];
 329
 330             if (base == 5 && mod == 0) {
 331                 op->basereg = -1;
 332                 mod = 2;        /* Fake disp32 */
 333             } else if (a64)
 334                 op->basereg = rd_reg64[base | ((rex & REX_B) ? 8 : 0)];
 335             else
 336                 op->basereg = rd_reg32[base | ((rex & REX_B) ? 8 : 0)];
 337
 338             if (segsize == 16)
 339                 op->disp_size = 32;
 340         }
 341
 342         switch (mod) {
 343         case 0:
 344             op->segment |= SEG_NODISP;
 345             break;
 346         case 1:
 347             op->segment |= SEG_DISP8;
 348             op->offset = gets8(data);
 349             data++;
 350             break;
 351         case 2:
 352             op->segment |= SEG_DISP32;
 353             op->offset = getu32(data);
 354             data += 4;
 355             break;
 356         }
 357         return data;
 358     }
 359 }
 360
 361 /*
 362  * Determine whether the instruction template in t corresponds to the data
 363  * stream in data. Return the number of bytes matched if so.
 364  */
 365 #define case4(x) case (x): case (x)+1: case (x)+2: case (x)+3
 366
 367 static int matches(const struct itemplate *t, uint8_t *data,
 368                    const struct prefix_info *prefix, int segsize, insn *ins)
 369 {
 370     uint8_t *r = (uint8_t *)(t->code);
 371     uint8_t *origdata = data;
 372     bool a_used = false, o_used = false;
 373     enum prefixes drep = 0;
 374     uint8_t lock = prefix->lock;
 375     int osize = prefix->osize;
 376     int asize = prefix->asize;
 377     int i, c;
 378     struct operand *opx;
 379
 380     for (i = 0; i < MAX_OPERANDS; i++) {
 381         ins->oprs[i].segment = ins->oprs[i].disp_size =
 382             (segsize == 64 ? SEG_64BIT : segsize == 32 ? SEG_32BIT : 0);
 383     }
 384     ins->condition = -1;
 385     ins->rex = prefix->rex;
 386     memset(ins->prefixes, 0, sizeof ins->prefixes);
 387
 388     if (t->flags & (segsize == 64 ? IF_NOLONG : IF_LONG))
 389         return false;
 390
 391     if (prefix->rep == 0xF2)
 392         drep = P_REPNE;
 393     else if (prefix->rep == 0xF3)
 394         drep = P_REP;
 395
 396     while ((c = *r++) != 0) {
 397         opx = &ins->oprs[c & 3];
 398
 399         switch (c) {
 400         case 01:
 401         case 02:
 402         case 03:
 403             while (c--)
 404                 if (*r++ != *data++)
 405                     return false;
 406             break;
 407
 408         case 04:
 409             switch (*data++) {
 410             case 0x07:
 411                 ins->oprs[0].basereg = 0;
 412                 break;
 413             case 0x17:
 414                 ins->oprs[0].basereg = 2;
 415                 break;
 416             case 0x1F:
 417                 ins->oprs[0].basereg = 3;
 418                 break;
 419             default:
 420                 return false;
 421             }
 422             break;
 423
 424         case 05:
 425             switch (*data++) {
 426             case 0xA1:
 427                 ins->oprs[0].basereg = 4;
 428                 break;
 429             case 0xA9:
 430                 ins->oprs[0].basereg = 5;
 431                 break;
 432             default:
 433                 return false;
 434             }
 435             break;
 436
 437         case 06:
 438             switch (*data++) {
 439             case 0x06:
 440                 ins->oprs[0].basereg = 0;
 441                 break;
 442             case 0x0E:
 443                 ins->oprs[0].basereg = 1;
 444                 break;
 445             case 0x16:
 446                 ins->oprs[0].basereg = 2;
 447                 break;
 448             case 0x1E:
 449                 ins->oprs[0].basereg = 3;
 450                 break;
 451             default:
 452                 return false;
 453             }
 454             break;
 455
 456         case 07:
 457             switch (*data++) {
 458             case 0xA0:
 459                 ins->oprs[0].basereg = 4;
 460                 break;
 461             case 0xA8:
 462                 ins->oprs[0].basereg = 5;
 463                 break;
 464             default:
 465                 return false;
 466             }
 467             break;
 468
 469         case4(010):
 470         {
 471             int t = *r++, d = *data++;
 472             if (d < t || d > t + 7)
 473                 return false;
 474             else {
 475                 opx->basereg = (d-t)+
 476                     (ins->rex & REX_B ? 8 : 0);
 477                 opx->segment |= SEG_RMREG;
 478             }
 479             break;
 480         }
 481
 482         case4(014):
 483             opx->offset = (int8_t)*data++;
 484             opx->segment |= SEG_SIGNED;
 485             break;
 486
 487         case4(020):
 488             opx->offset = *data++;
 489             break;
 490
 491         case4(024):
 492             opx->offset = *data++;
 493             break;
 494
 495         case4(030):
 496             opx->offset = getu16(data);
 497             data += 2;
 498             break;
 499
 500         case4(034):
 501             if (osize == 32) {
 502                 opx->offset = getu32(data);
 503                 data += 4;
 504             } else {
 505                 opx->offset = getu16(data);
 506                 data += 2;
 507             }
 508             if (segsize != asize)
 509                 opx->disp_size = asize;
 510             break;
 511
 512         case4(040):
 513             opx->offset = getu32(data);
 514             data += 4;
 515             break;
 516
 517         case4(044):
 518             switch (asize) {
 519             case 16:
 520                 opx->offset = getu16(data);
 521                 data += 2;
 522                 if (segsize != 16)
 523                     opx->disp_size = 16;
 524                 break;
 525             case 32:
 526                 opx->offset = getu32(data);
 527                 data += 4;
 528                 if (segsize == 16)
 529                     opx->disp_size = 32;
 530                 break;
 531             case 64:
 532                 opx->offset = getu64(data);
 533                 opx->disp_size = 64;
 534                 data += 8;
 535                 break;
 536             }
 537             break;
 538
 539         case4(050):
 540             opx->offset = gets8(data++);
 541             opx->segment |= SEG_RELATIVE;
 542             break;
 543
 544         case4(054):
 545             opx->offset = getu64(data);
 546             data += 8;
 547             break;
 548
 549         case4(060):
 550             opx->offset = gets16(data);
 551             data += 2;
 552             opx->segment |= SEG_RELATIVE;
 553             opx->segment &= ~SEG_32BIT;
 554             break;
 555
 556         case4(064):
 557             opx->segment |= SEG_RELATIVE;
 558             if (osize == 16) {
 559                 opx->offset = getu16(data);
 560                 data += 2;
 561                 opx->segment &= ~(SEG_32BIT|SEG_64BIT);
 562             } else if (osize == 32) {
 563                 opx->offset = getu32(data);
 564                 data += 4;
 565                 opx->segment &= ~SEG_64BIT;
 566                 opx->segment |= SEG_32BIT;
 567             }
 568             if (segsize != osize) {
 569                 opx->type =
 570                     (opx->type & ~SIZE_MASK)
 571                     | ((osize == 16) ? BITS16 : BITS32);
 572             }
 573             break;
 574
 575         case4(070):
 576             opx->offset = getu32(data);
 577             data += 4;
 578             opx->segment |= SEG_32BIT | SEG_RELATIVE;
 579             break;
 580
 581         case4(0100):
 582         case4(0110):
 583         case4(0120):
 584         case4(0130):
 585         {
 586             int modrm = *data++;
 587             opx->segment |= SEG_RMREG;
 588             data = do_ea(data, modrm, asize, segsize,
 589                          &ins->oprs[(c >> 3) & 3], ins);
 590             if (!data)
 591                 return false;
 592             opx->basereg = ((modrm >> 3)&7)+
 593                 (ins->rex & REX_R ? 8 : 0);
 594             break;
 595         }
 596
 597         case4(0140):
 598             opx->offset = getu16(data);
 599             data += 2;
 600             break;
 601
 602         case4(0150):
 603             opx->offset = getu32(data);
 604             data += 4;
 605             break;
 606
 607         case4(0160):
 608             ins->rex |= REX_D;
 609             ins->drexdst = c & 3;
 610             break;
 611
 612         case4(0164):
 613             ins->rex |= REX_D|REX_OC;
 614             ins->drexdst = c & 3;
 615             break;
 616
 617         case 0170:
 618             if (*data++)
 619                 return false;
 620             break;
 621
 622         case 0171:
 623             data = do_drex(data, ins);
 624             if (!data)
 625                 return false;
 626             break;
 627
 628         case4(0200):
 629         case4(0204):
 630         case4(0210):
 631         case4(0214):
 632         case4(0220):
 633         case4(0224):
 634         case4(0230):
 635         case4(0234):
 636         {
 637             int modrm = *data++;
 638             if (((modrm >> 3) & 07) != (c & 07))
 639                 return false;   /* spare field doesn't match up */
 640             data = do_ea(data, modrm, asize, segsize,
 641                          &ins->oprs[(c >> 3) & 07], ins);
 642             if (!data)
 643                 return false;
 644             break;
 645         }
 646
 647         case 0310:
 648             if (asize != 16)
 649                 return false;
 650             else
 651                 a_used = true;
 652             break;
 653
 654         case 0311:
 655             if (asize == 16)
 656                 return false;
 657             else
 658                 a_used = true;
 659             break;
 660
 661         case 0312:
 662             if (asize != segsize)
 663                 return false;
 664             else
 665                 a_used = true;
 666             break;
 667
 668         case 0313:
 669             if (asize != 64)
 670                 return false;
 671             else
 672                 a_used = true;
 673             break;
 674
 675         case 0314:
 676             if (prefix->rex & REX_B)
 677                 return false;
 678             break;
 679
 680         case 0315:
 681             if (prefix->rex & REX_X)
 682                 return false;
 683             break;
 684
 685         case 0316:
 686             if (prefix->rex & REX_R)
 687                 return false;
 688             break;
 689
 690         case 0317:
 691             if (prefix->rex & REX_W)
 692                 return false;
 693             break;
 694
 695         case 0320:
 696             if (osize != 16)
 697                 return false;
 698             else
 699                 o_used = true;
 700             break;
 701
 702         case 0321:
 703             if (osize != 32)
 704                 return false;
 705             else
 706                 o_used = true;
 707             break;
 708
 709         case 0322:
 710             if (osize != (segsize == 16) ? 16 : 32)
 711                 return false;
 712             else
 713                 o_used = true;
 714             break;
 715
 716         case 0323:
 717             ins->rex |= REX_W;  /* 64-bit only instruction */
 718             osize = 64;
 719             o_used = true;
 720             break;
 721
 722         case 0324:
 723             if (!(ins->rex & (REX_P|REX_W)) || osize != 64)
 724                 return false;
 725             o_used = true;
 726             break;
 727
 728         case 0330:
 729         {
 730             int t = *r++, d = *data++;
 731             if (d < t || d > t + 15)
 732                 return false;
 733             else
 734                 ins->condition = d - t;
 735             break;
 736         }
 737
 738         case 0331:
 739             if (prefix->rep)
 740                 return false;
 741             break;
 742
 743         case 0332:
 744             if (prefix->rep != 0xF2)
 745                 return false;
 746             break;
 747
 748         case 0333:
 749             if (prefix->rep != 0xF3)
 750                 return false;
 751             drep = 0;
 752             break;
 753
 754         case 0334:
 755             if (lock) {
 756                 ins->rex |= REX_R;
 757                 lock = 0;
 758             }
 759             break;
 760
 761         case 0335:
 762             if (drep == P_REP)
 763                 drep = P_REPE;
 764             break;
 765
 766         case 0340:
 767             return false;
 768
 769         case 0364:
 770             if (prefix->osp)
 771                 return false;
 772             break;
 773
 774         case 0365:
 775             if (prefix->asp)
 776                 return false;
 777             break;
 778
 779         case 0366:
 780             if (!prefix->osp)
 781                 return false;
 782             o_used = true;
 783             break;
 784
 785         case 0367:
 786             if (!prefix->asp)
 787                 return false;
 788             a_used = true;
 789             break;
 790
 791         default:
 792             return false;       /* Unknown code */
 793         }
 794     }
 795
 796     /* REX cannot be combined with DREX */
 797     if ((ins->rex & REX_D) && (prefix->rex))
 798         return false;
 799
 800     /*
 801      * Check for unused rep or a/o prefixes.
 802      */
 803     for (i = 0; i < t->operands; i++) {
 804         if (ins->oprs[i].segment != SEG_RMREG)
 805             a_used = true;
 806     }
 807
 808     if (lock) {
 809         if (ins->prefixes[PPS_LREP])
 810             return false;
 811         ins->prefixes[PPS_LREP] = P_LOCK;
 812     }
 813     if (drep) {
 814         if (ins->prefixes[PPS_LREP])
 815             return false;
 816         ins->prefixes[PPS_LREP] = drep;
 817     }
 818     if (!o_used) {
 819         if (osize != ((segsize == 16) ? 16 : 32)) {
 820             enum prefixes pfx = 0;
 821
 822             switch (osize) {
 823             case 16:
 824                 pfx = P_O16;
 825                 break;
 826             case 32:
 827                 pfx = P_O32;
 828                 break;
 829             case 64:
 830                 pfx = P_O64;
 831                 break;
 832             }
 833
 834             if (ins->prefixes[PPS_OSIZE])
 835                 return false;
 836             ins->prefixes[PPS_OSIZE] = pfx;
 837         }
 838     }
 839     if (!a_used && asize != segsize) {
 840         if (ins->prefixes[PPS_ASIZE])
 841             return false;
 842         ins->prefixes[PPS_ASIZE] = asize == 16 ? P_A16 : P_A32;
 843     }
 844
 845     /* Fix: check for redundant REX prefixes */
 846
 847     return data - origdata;
 848 }
 849
 850 int32_t disasm(uint8_t *data, char *output, int outbufsize, int segsize,
 851             int32_t offset, int autosync, uint32_t prefer)
 852 {
 853     const struct itemplate * const *p, * const *best_p;
 854     const struct disasm_index *ix;
 855     uint8_t *dp;
 856     int length, best_length = 0;
 857     char *segover;
 858     int i, slen, colon, n;
 859     uint8_t *origdata;
 860     int works;
 861     insn tmp_ins, ins;
 862     uint32_t goodness, best;
 863     int best_pref;
 864     struct prefix_info prefix;
 865     bool end_prefix;
 866
 867     memset(&ins, 0, sizeof ins);
 868
 869     /*
 870      * Scan for prefixes.
 871      */
 872     memset(&prefix, 0, sizeof prefix);
 873     prefix.asize = segsize;
 874     prefix.osize = (segsize == 64) ? 32 : segsize;
 875     segover = NULL;
 876     origdata = data;
 877
 878     for (end_prefix = false; !end_prefix; ) {
 879         switch (*data) {
 880         case 0xF2:
 881         case 0xF3:
 882             prefix.rep = *data++;
 883             break;
 884         case 0xF0:
 885             prefix.lock = *data++;
 886             break;
 887         case 0x2E:
 888             segover = "cs", prefix.seg = *data++;
 889             break;
 890         case 0x36:
 891             segover = "ss", prefix.seg = *data++;
 892             break;
 893         case 0x3E:
 894             segover = "ds", prefix.seg = *data++;
 895             break;
 896         case 0x26:
 897             segover = "es", prefix.seg = *data++;
 898             break;
 899         case 0x64:
 900             segover = "fs", prefix.seg = *data++;
 901             break;
 902         case 0x65:
 903             segover = "gs", prefix.seg = *data++;
 904             break;
 905         case 0x66:
 906             prefix.osize = (segsize == 16) ? 32 : 16;
 907             prefix.osp = *data++;
 908             break;
 909         case 0x67:
 910             prefix.asize = (segsize == 32) ? 16 : 32;
 911             prefix.asp = *data++;
 912             break;
 913         default:
 914             if (segsize == 64 && (*data & 0xf0) == REX_P) {
 915                 prefix.rex = *data++;
 916                 if (prefix.rex & REX_W)
 917                     prefix.osize = 64;
 918                 end_prefix = true;
 919             } else {
 920                 end_prefix = true;
 921             }
 922         }
 923     }
 924
 925     best = -1;                  /* Worst possible */
 926     best_p = NULL;
 927     best_pref = INT_MAX;
 928
 929     dp = data;
 930     ix = itable + *dp++;
 931     while (ix->n == -1) {
 932         ix = (const struct disasm_index *)ix->p + *dp++;
 933     }
 934
 935     p = (const struct itemplate * const *)ix->p;
 936     for (n = ix->n; n; n--, p++) {
 937         if ((length = matches(*p, data, &prefix, segsize, &tmp_ins))) {
 938             works = true;
 939             /*
 940              * Final check to make sure the types of r/m match up.
 941              * XXX: Need to make sure this is actually correct.
 942              */
 943             for (i = 0; i < (*p)->operands; i++) {
 944                 if (!((*p)->opd[i] & SAME_AS) &&
 945                     (
 946                         /* If it's a mem-only EA but we have a
 947                            register, die. */
 948                         ((tmp_ins.oprs[i].segment & SEG_RMREG) &&
 949                          !(MEMORY & ~(*p)->opd[i])) ||
 950                         /* If it's a reg-only EA but we have a memory
 951                            ref, die. */
 952                         (!(tmp_ins.oprs[i].segment & SEG_RMREG) &&
 953                          !(REG_EA & ~(*p)->opd[i]) &&
 954                          !((*p)->opd[i] & REG_SMASK)) ||
 955                         /* Register type mismatch (eg FS vs REG_DESS):
 956                            die. */
 957                         ((((*p)->opd[i] & (REGISTER | FPUREG)) ||
 958                           (tmp_ins.oprs[i].segment & SEG_RMREG)) &&
 959                          !whichreg((*p)->opd[i],
 960                                    tmp_ins.oprs[i].basereg, tmp_ins.rex))
 961                         )) {
 962                     works = false;
 963                     break;
 964                 }
 965             }
 966
 967             /*
 968              * Note: we always prefer instructions which incorporate
 969              * prefixes in the instructions themselves.  This is to allow
 970              * e.g. PAUSE to be preferred to REP NOP, and deal with
 971              * MMX/SSE instructions where prefixes are used to select
 972              * between MMX and SSE register sets or outright opcode
 973              * selection.
 974              */
 975             if (works) {
 976                 int i, nprefix;
 977                 goodness = ((*p)->flags & IF_PFMASK) ^ prefer;
 978                 nprefix = 0;
 979                 for (i = 0; i < MAXPREFIX; i++)
 980                     if (tmp_ins.prefixes[i])
 981                         nprefix++;
 982                 if (nprefix < best_pref ||
 983                     (nprefix == best_pref && goodness < best)) {
 984                     /* This is the best one found so far */
 985                     best = goodness;
 986                     best_p = p;
 987                     best_pref = nprefix;
 988                     best_length = length;
 989                     ins = tmp_ins;
 990                 }
 991             }
 992         }
 993     }
 994
 995     if (!best_p)
 996         return 0;               /* no instruction was matched */
 997
 998     /* Pick the best match */
 999     p = best_p;
1000     length = best_length;
1001
1002     slen = 0;
1003
1004     /* TODO: snprintf returns the value that the string would have if
1005      *      the buffer were long enough, and not the actual length of
1006      *      the returned string, so each instance of using the return
1007      *      value of snprintf should actually be checked to assure that
1008      *      the return value is "sane."  Maybe a macro wrapper could
1009      *      be used for that purpose.
1010      */
1011     for (i = 0; i < MAXPREFIX; i++)
1012         switch (ins.prefixes[i]) {
1013         case P_LOCK:
1014             slen += snprintf(output + slen, outbufsize - slen, "lock ");
1015             break;
1016         case P_REP:
1017             slen += snprintf(output + slen, outbufsize - slen, "rep ");
1018             break;
1019         case P_REPE:
1020             slen += snprintf(output + slen, outbufsize - slen, "repe ");
1021             break;
1022         case P_REPNE:
1023             slen += snprintf(output + slen, outbufsize - slen, "repne ");
1024             break;
1025         case P_A16:
1026             slen += snprintf(output + slen, outbufsize - slen, "a16 ");
1027             break;
1028         case P_A32:
1029             slen += snprintf(output + slen, outbufsize - slen, "a32 ");
1030             break;
1031         case P_A64:
1032             slen += snprintf(output + slen, outbufsize - slen, "a64 ");
1033             break;
1034         case P_O16:
1035             slen += snprintf(output + slen, outbufsize - slen, "o16 ");
1036             break;
1037         case P_O32:
1038             slen += snprintf(output + slen, outbufsize - slen, "o32 ");
1039             break;
1040         case P_O64:
1041             slen += snprintf(output + slen, outbufsize - slen, "o64 ");
1042             break;
1043         default:
1044             break;
1045         }
1046
1047     for (i = 0; i < (int)elements(ico); i++)
1048         if ((*p)->opcode == ico[i]) {
1049             slen +=
1050                 snprintf(output + slen, outbufsize - slen, "%s%s", icn[i],
1051                          whichcond(ins.condition));
1052             break;
1053         }
1054     if (i >= (int)elements(ico))
1055         slen +=
1056             snprintf(output + slen, outbufsize - slen, "%s",
1057                      insn_names[(*p)->opcode]);
1058     colon = false;
1059     length += data - origdata;  /* fix up for prefixes */
1060     for (i = 0; i < (*p)->operands; i++) {
1061         opflags_t t = (*p)->opd[i];
1062         const operand *o = &ins.oprs[i];
1063         int64_t offs;
1064
1065         if (t & SAME_AS) {
1066             o = &ins.oprs[t & ~SAME_AS];
1067             t = (*p)->opd[t & ~SAME_AS];
1068         }
1069
1070         output[slen++] = (colon ? ':' : i == 0 ? ' ' : ',');
1071
1072         offs = o->offset;
1073         if (o->segment & SEG_RELATIVE) {
1074             offs += offset + length;
1075             /*
1076              * sort out wraparound
1077              */
1078             if (!(o->segment & (SEG_32BIT|SEG_64BIT)))
1079                 offs &= 0xffff;
1080             /*
1081              * add sync marker, if autosync is on
1082              */
1083             if (autosync)
1084                 add_sync(offs, 0L);
1085         }
1086
1087         if (t & COLON)
1088             colon = true;
1089         else
1090             colon = false;
1091
1092         if ((t & (REGISTER | FPUREG)) ||
1093             (o->segment & SEG_RMREG)) {
1094             enum reg_enum reg;
1095             reg = whichreg(t, o->basereg, ins.rex);
1096             if (t & TO)
1097                 slen += snprintf(output + slen, outbufsize - slen, "to ");
1098             slen += snprintf(output + slen, outbufsize - slen, "%s",
1099                              reg_names[reg - EXPR_REG_START]);
1100         } else if (!(UNITY & ~t)) {
1101             output[slen++] = '1';
1102         } else if (t & IMMEDIATE) {
1103             if (t & BITS8) {
1104                 slen +=
1105                     snprintf(output + slen, outbufsize - slen, "byte ");
1106                 if (o->segment & SEG_SIGNED) {
1107                     if (offs < 0) {
1108                         offs *= -1;
1109                         output[slen++] = '-';
1110                     } else
1111                         output[slen++] = '+';
1112                 }
1113             } else if (t & BITS16) {
1114                 slen +=
1115                     snprintf(output + slen, outbufsize - slen, "word ");
1116             } else if (t & BITS32) {
1117                 slen +=
1118                     snprintf(output + slen, outbufsize - slen, "dword ");
1119             } else if (t & BITS64) {
1120                 slen +=
1121                     snprintf(output + slen, outbufsize - slen, "qword ");
1122             } else if (t & NEAR) {
1123                 slen +=
1124                     snprintf(output + slen, outbufsize - slen, "near ");
1125             } else if (t & SHORT) {
1126                 slen +=
1127                     snprintf(output + slen, outbufsize - slen, "short ");
1128             }
1129             slen +=
1130                 snprintf(output + slen, outbufsize - slen, "0x%"PRIx64"",
1131                          offs);
1132         } else if (!(MEM_OFFS & ~t)) {
1133             slen +=
1134                 snprintf(output + slen, outbufsize - slen,
1135                          "[%s%s%s0x%"PRIx64"]",
1136                          (segover ? segover : ""),
1137                          (segover ? ":" : ""),
1138                          (o->disp_size == 64 ? "qword " :
1139                           o->disp_size == 32 ? "dword " :
1140                           o->disp_size == 16 ? "word " : ""), offs);
1141             segover = NULL;
1142         } else if (!(REGMEM & ~t)) {
1143             int started = false;
1144             if (t & BITS8)
1145                 slen +=
1146                     snprintf(output + slen, outbufsize - slen, "byte ");
1147             if (t & BITS16)
1148                 slen +=
1149                     snprintf(output + slen, outbufsize - slen, "word ");
1150             if (t & BITS32)
1151                 slen +=
1152                     snprintf(output + slen, outbufsize - slen, "dword ");
1153             if (t & BITS64)
1154                 slen +=
1155                     snprintf(output + slen, outbufsize - slen, "qword ");
1156             if (t & BITS80)
1157                 slen +=
1158                     snprintf(output + slen, outbufsize - slen, "tword ");
1159             if (t & BITS128)
1160                 slen +=
1161                     snprintf(output + slen, outbufsize - slen, "oword ");
1162             if (t & FAR)
1163                 slen += snprintf(output + slen, outbufsize - slen, "far ");
1164             if (t & NEAR)
1165                 slen +=
1166                     snprintf(output + slen, outbufsize - slen, "near ");
1167             output[slen++] = '[';
1168             if (o->disp_size)
1169                 slen += snprintf(output + slen, outbufsize - slen, "%s",
1170                                  (o->disp_size == 64 ? "qword " :
1171                                   o->disp_size == 32 ? "dword " :
1172                                   o->disp_size == 16 ? "word " :
1173                                   ""));
1174             if (o->eaflags & EAF_REL)
1175                 slen += snprintf(output + slen, outbufsize - slen, "rel ");
1176             if (segover) {
1177                 slen +=
1178                     snprintf(output + slen, outbufsize - slen, "%s:",
1179                              segover);
1180                 segover = NULL;
1181             }
1182             if (o->basereg != -1) {
1183                 slen += snprintf(output + slen, outbufsize - slen, "%s",
1184                                  reg_names[(o->basereg -
1185                                             EXPR_REG_START)]);
1186                 started = true;
1187             }
1188             if (o->indexreg != -1) {
1189                 if (started)
1190                     output[slen++] = '+';
1191                 slen += snprintf(output + slen, outbufsize - slen, "%s",
1192                                  reg_names[(o->indexreg -
1193                                             EXPR_REG_START)]);
1194                 if (o->scale > 1)
1195                     slen +=
1196                         snprintf(output + slen, outbufsize - slen, "*%d",
1197                                  o->scale);
1198                 started = true;
1199             }
1200
1201
1202             if (o->segment & SEG_DISP8) {
1203                 const char *prefix;
1204                 uint8_t offset = offs;
1205                 if ((int8_t)offset < 0) {
1206                     prefix = "-";
1207                     offset = -offset;
1208                 } else {
1209                     prefix = "+";
1210                 }
1211                 slen +=
1212                     snprintf(output + slen, outbufsize - slen, "%s0x%"PRIx8"",
1213                              prefix, offset);
1214             } else if (o->segment & SEG_DISP16) {
1215                 const char *prefix;
1216                 uint16_t offset = offs;
1217                 if ((int16_t)offset < 0 && started) {
1218                     offset = -offset;
1219                     prefix = "-";
1220                 } else {
1221                     prefix = started ? "+" : "";
1222                 }
1223                 slen +=
1224                     snprintf(output + slen, outbufsize - slen,
1225                              "%s0x%"PRIx16"", prefix, offset);
1226             } else if (o->segment & SEG_DISP32) {
1227                 if (prefix.asize == 64) {
1228                     const char *prefix;
1229                     uint64_t offset = (int64_t)(int32_t)offs;
1230                     if ((int32_t)offs < 0 && started) {
1231                         offset = -offset;
1232                         prefix = "-";
1233                     } else {
1234                         prefix = started ? "+" : "";
1235                     }
1236                     slen +=
1237                         snprintf(output + slen, outbufsize - slen,
1238                                  "%s0x%"PRIx64"", prefix, offset);
1239                 } else {
1240                     const char *prefix;
1241                     uint32_t offset = offs;
1242                     if ((int32_t) offset < 0 && started) {
1243                         offset = -offset;
1244                         prefix = "-";
1245                     } else {
1246                         prefix = started ? "+" : "";
1247                     }
1248                     slen +=
1249                         snprintf(output + slen, outbufsize - slen,
1250                                  "%s0x%"PRIx32"", prefix, offset);
1251                 }
1252             }
1253             output[slen++] = ']';
1254         } else {
1255             slen +=
1256                 snprintf(output + slen, outbufsize - slen, "<operand%d>",
1257                          i);
1258         }
1259     }
1260     output[slen] = '\0';
1261     if (segover) {              /* unused segment override */
1262         char *p = output;
1263         int count = slen + 1;
1264         while (count--)
1265             p[count + 3] = p[count];
1266         strncpy(output, segover, 2);
1267         output[2] = ' ';
1268     }
1269     return length;
1270 }
1271
1272 int32_t eatbyte(uint8_t *data, char *output, int outbufsize)
1273 {
1274     snprintf(output, outbufsize, "db 0x%02X", *data);
1275     return 1;
1276 }