/src/capstonev5/arch/X86/X86DisassemblerDecoder.c

Source
/*===-- X86DisassemblerDecoder.c - Disassembler decoder ------------*- C -*-===*
 *
 *                     The LLVM Compiler Infrastructure
 *
 * This file is distributed under the University of Illinois Open Source
 * License. See LICENSE.TXT for details.
 *
 *===----------------------------------------------------------------------===*
 *
 * This file is part of the X86 Disassembler.
 * It contains the implementation of the instruction decoder.
 * Documentation for the disassembler can be found in X86Disassembler.h.
 *
 *===----------------------------------------------------------------------===*/

/* Capstone Disassembly Engine */
/* By Nguyen Anh Quynh <aquynh@gmail.com>, 2013-2019 */

#ifdef CAPSTONE_HAS_X86

#include <stdarg.h>   /* for va_*()       */
#if defined(CAPSTONE_HAS_OSXKERNEL)
#include <libkern/libkern.h>
#else
#include <stdlib.h>   /* for exit()       */
#endif

#include <string.h>

#include "../../cs_priv.h"
#include "../../utils.h"

#include "X86DisassemblerDecoder.h"
#include "X86Mapping.h"

/// Specifies whether a ModR/M byte is needed and (if so) which
/// instruction each possible value of the ModR/M byte corresponds to.  Once
/// this information is known, we have narrowed down to a single instruction.
struct ModRMDecision {
  uint8_t modrm_type;
  uint16_t instructionIDs;
};

/// Specifies which set of ModR/M->instruction tables to look at
/// given a particular opcode.
struct OpcodeDecision {
  struct ModRMDecision modRMDecisions[256];
};

/// Specifies which opcode->instruction tables to look at given
/// a particular context (set of attributes).  Since there are many possible
/// contexts, the decoder first uses CONTEXTS_SYM to determine which context
/// applies given a specific set of attributes.  Hence there are only IC_max
/// entries in this table, rather than 2^(ATTR_max).
struct ContextDecision {
  struct OpcodeDecision opcodeDecisions[IC_max];
};

#ifdef CAPSTONE_X86_REDUCE
#include "X86GenDisassemblerTables_reduce.inc"
#include "X86GenDisassemblerTables_reduce2.inc"
#include "X86Lookup16_reduce.inc"
#else
#include "X86GenDisassemblerTables.inc"
#include "X86GenDisassemblerTables2.inc"
#include "X86Lookup16.inc"
#endif

/*
 * contextForAttrs - Client for the instruction context table.  Takes a set of
 *   attributes and returns the appropriate decode context.
 *
 * @param attrMask  - Attributes, from the enumeration attributeBits.
 * @return          - The InstructionContext to use when looking up an
 *                    an instruction with these attributes.
 */
static InstructionContext contextForAttrs(uint16_t attrMask)
{
  return CONTEXTS_SYM[attrMask];
}

/*
 * modRMRequired - Reads the appropriate instruction table to determine whether
 *   the ModR/M byte is required to decode a particular instruction.
 *
 * @param type        - The opcode type (i.e., how many bytes it has).
 * @param insnContext - The context for the instruction, as returned by
 *                      contextForAttrs.
 * @param opcode      - The last byte of the instruction's opcode, not counting
 *                      ModR/M extensions and escapes.
 * @return            - true if the ModR/M byte is required, false otherwise.
 */
static int modRMRequired(OpcodeType type,
    InstructionContext insnContext,
    uint16_t opcode)
{
  const struct OpcodeDecision *decision = NULL;
  const uint8_t *indextable = NULL;
  unsigned int index;

  switch (type) {
    default:
      return false;
    case ONEBYTE:
      decision = ONEBYTE_SYM;
      indextable = index_x86DisassemblerOneByteOpcodes;
      break;
    case TWOBYTE:
      decision = TWOBYTE_SYM;
      indextable = index_x86DisassemblerTwoByteOpcodes;
      break;
    case THREEBYTE_38:
      decision = THREEBYTE38_SYM;
      indextable = index_x86DisassemblerThreeByte38Opcodes;
      break;
    case THREEBYTE_3A:
      decision = THREEBYTE3A_SYM;
      indextable = index_x86DisassemblerThreeByte3AOpcodes;
      break;
#ifndef CAPSTONE_X86_REDUCE
    case XOP8_MAP:
      decision = XOP8_MAP_SYM;
      indextable = index_x86DisassemblerXOP8Opcodes;
      break;
    case XOP9_MAP:
      decision = XOP9_MAP_SYM;
      indextable = index_x86DisassemblerXOP9Opcodes;
      break;
    case XOPA_MAP:
      decision = XOPA_MAP_SYM;
      indextable = index_x86DisassemblerXOPAOpcodes;
      break;
    case THREEDNOW_MAP:
      // 3DNow instructions always have ModRM byte
      return true;
#endif
  }

  // return decision->opcodeDecisions[insnContext].modRMDecisions[opcode].modrm_type != MODRM_ONEENTRY;
  index = indextable[insnContext];
  if (index)
    return decision[index - 1].modRMDecisions[opcode].modrm_type != MODRM_ONEENTRY;
  else
    return false;
}

/*
 * decode - Reads the appropriate instruction table to obtain the unique ID of
 *   an instruction.
 *
 * @param type        - See modRMRequired().
 * @param insnContext - See modRMRequired().
 * @param opcode      - See modRMRequired().
 * @param modRM       - The ModR/M byte if required, or any value if not.
 * @return            - The UID of the instruction, or 0 on failure.
 */
static InstrUID decode(OpcodeType type,
                       InstructionContext insnContext,
                       uint8_t opcode,
                       uint8_t modRM)
{
  const struct ModRMDecision *dec = NULL;
  unsigned int index;
  static const struct OpcodeDecision emptyDecision = { 0 };

  switch (type) {
    default:
      return 0;
    case ONEBYTE:
      // dec = &ONEBYTE_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerOneByteOpcodes[insnContext];
      if (index)
        dec = &ONEBYTE_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case TWOBYTE:
      //dec = &TWOBYTE_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerTwoByteOpcodes[insnContext];
      if (index)
        dec = &TWOBYTE_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case THREEBYTE_38:
      // dec = &THREEBYTE38_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerThreeByte38Opcodes[insnContext];
      if (index)
        dec = &THREEBYTE38_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case THREEBYTE_3A:
      //dec = &THREEBYTE3A_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerThreeByte3AOpcodes[insnContext];
      if (index)
        dec = &THREEBYTE3A_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
#ifndef CAPSTONE_X86_REDUCE
    case XOP8_MAP:
      // dec = &XOP8_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerXOP8Opcodes[insnContext];
      if (index)
        dec = &XOP8_MAP_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case XOP9_MAP:
      // dec = &XOP9_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerXOP9Opcodes[insnContext];
      if (index)
        dec = &XOP9_MAP_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case XOPA_MAP:
      // dec = &XOPA_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86DisassemblerXOPAOpcodes[insnContext];
      if (index)
        dec = &XOPA_MAP_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
    case THREEDNOW_MAP:
      // dec = &THREEDNOW_MAP_SYM.opcodeDecisions[insnContext].modRMDecisions[opcode];
      index = index_x86Disassembler3DNowOpcodes[insnContext];
      if (index)
        dec = &THREEDNOW_MAP_SYM[index - 1].modRMDecisions[opcode];
      else
        dec = &emptyDecision.modRMDecisions[opcode];
      break;
#endif
  }

  switch (dec->modrm_type) {
    default:
      // debug("Corrupt table!  Unknown modrm_type");
      return 0;
    case MODRM_ONEENTRY:
      return modRMTable[dec->instructionIDs];
    case MODRM_SPLITRM:
      if (modFromModRM(modRM) == 0x3)
        return modRMTable[dec->instructionIDs + 1];
      return modRMTable[dec->instructionIDs];
    case MODRM_SPLITREG:
      if (modFromModRM(modRM) == 0x3)
        return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3) + 8];
      return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)];
    case MODRM_SPLITMISC:
      if (modFromModRM(modRM) == 0x3)
        return modRMTable[dec->instructionIDs+(modRM & 0x3f) + 8];
      return modRMTable[dec->instructionIDs+((modRM & 0x38) >> 3)];
    case MODRM_FULL:
      return modRMTable[dec->instructionIDs+modRM];
  }
}

/*
 * specifierForUID - Given a UID, returns the name and operand specification for
 *   that instruction.
 *
 * @param uid - The unique ID for the instruction.  This should be returned by
 *              decode(); specifierForUID will not check bounds.
 * @return    - A pointer to the specification for that instruction.
 */
static const struct InstructionSpecifier *specifierForUID(InstrUID uid)
{
  return &INSTRUCTIONS_SYM[uid];
}

/*
 * consumeByte - Uses the reader function provided by the user to consume one
 *   byte from the instruction's memory and advance the cursor.
 *
 * @param insn  - The instruction with the reader function to use.  The cursor
 *                for this instruction is advanced.
 * @param byte  - A pointer to a pre-allocated memory buffer to be populated
 *                with the data read.
 * @return      - 0 if the read was successful; nonzero otherwise.
 */
static int consumeByte(struct InternalInstruction* insn, uint8_t* byte)
{
  int ret = insn->reader(insn->readerArg, byte, insn->readerCursor);

  if (!ret)
    ++(insn->readerCursor);

  return ret;
}

/*
 * lookAtByte - Like consumeByte, but does not advance the cursor.
 *
 * @param insn  - See consumeByte().
 * @param byte  - See consumeByte().
 * @return      - See consumeByte().
 */
static int lookAtByte(struct InternalInstruction* insn, uint8_t* byte)
{
  return insn->reader(insn->readerArg, byte, insn->readerCursor);
}

static void unconsumeByte(struct InternalInstruction* insn)
{
  insn->readerCursor--;
}

#define CONSUME_FUNC(name, type)                                  \
  static int name(struct InternalInstruction* insn, type* ptr) {  \
    type combined = 0;                                            \
    unsigned offset;                                              \
    for (offset = 0; offset < sizeof(type); ++offset) {           \
      uint8_t byte;                                               \
      int ret = insn->reader(insn->readerArg,                     \
                             &byte,                               \
                             insn->readerCursor + offset);        \
      if (ret)                                                    \
        return ret;                                               \
      combined = combined | ((uint64_t)byte << (offset * 8));     \
    }                                                             \
    *ptr = combined;                                              \
    insn->readerCursor += sizeof(type);                           \
    return 0;                                                     \
  }

/*
 * consume* - Use the reader function provided by the user to consume data
 *   values of various sizes from the instruction's memory and advance the
 *   cursor appropriately.  These readers perform endian conversion.
 *
 * @param insn    - See consumeByte().
 * @param ptr     - A pointer to a pre-allocated memory of appropriate size to
 *                  be populated with the data read.
 * @return        - See consumeByte().
 */
CONSUME_FUNC(consumeInt8, int8_t)
CONSUME_FUNC(consumeInt16, int16_t)
CONSUME_FUNC(consumeInt32, int32_t)
CONSUME_FUNC(consumeUInt16, uint16_t)
CONSUME_FUNC(consumeUInt32, uint32_t)
CONSUME_FUNC(consumeUInt64, uint64_t)

static bool isREX(struct InternalInstruction *insn, uint8_t prefix)
{
  if (insn->mode == MODE_64BIT)
    return prefix >= 0x40 && prefix <= 0x4f;

  return false;
}

/*
 * setPrefixPresent - Marks that a particular prefix is present as mandatory
 *
 * @param insn      - The instruction to be marked as having the prefix.
 * @param prefix    - The prefix that is present.
 */
static void setPrefixPresent(struct InternalInstruction *insn, uint8_t prefix)
{
  uint8_t nextByte;

  switch (prefix) {
    case 0xf0:  // LOCK
      insn->hasLockPrefix = true;
      insn->repeatPrefix = 0;
      break;

    case 0xf2:  // REPNE/REPNZ
    case 0xf3:  // REP or REPE/REPZ
      if (lookAtByte(insn, &nextByte))
        break;
      // TODO:
      //  1. There could be several 0x66
      //  2. if (nextByte == 0x66) and nextNextByte != 0x0f then
      //      it's not mandatory prefix
      //  3. if (nextByte >= 0x40 && nextByte <= 0x4f) it's REX and we need
      //     0x0f exactly after it to be mandatory prefix
      if (isREX(insn, nextByte) || nextByte == 0x0f || nextByte == 0x66)
        // The last of 0xf2 /0xf3 is mandatory prefix
        insn->mandatoryPrefix = prefix;

      insn->repeatPrefix = prefix;
      insn->hasLockPrefix = false;
      break;

    case 0x66:
      if (lookAtByte(insn, &nextByte))
        break;
      // 0x66 can't overwrite existing mandatory prefix and should be ignored
      if (!insn->mandatoryPrefix && (nextByte == 0x0f || isREX(insn, nextByte)))
        insn->mandatoryPrefix = prefix;
      break;
  }
}

/*
 * readPrefixes - Consumes all of an instruction's prefix bytes, and marks the
 *   instruction as having them.  Also sets the instruction's default operand,
 *   address, and other relevant data sizes to report operands correctly.
 *
 * @param insn  - The instruction whose prefixes are to be read.
 * @return      - 0 if the instruction could be read until the end of the prefix
 *                bytes, and no prefixes conflicted; nonzero otherwise.
 */
static int readPrefixes(struct InternalInstruction* insn)
{
  bool isPrefix = true;
  uint8_t byte = 0;
  uint8_t nextByte;

  while (isPrefix) {
    if (insn->mode == MODE_64BIT) {
      // eliminate consecutive redundant REX bytes in front
      if (consumeByte(insn, &byte))
        return -1;

      if ((byte & 0xf0) == 0x40) {
        while(true) {
          if (lookAtByte(insn, &byte))  // out of input code
            return -1;
          if ((byte & 0xf0) == 0x40) {
            // another REX prefix, but we only remember the last one
            if (consumeByte(insn, &byte))
              return -1;
          } else
            break;
        }

        // recover the last REX byte if next byte is not a legacy prefix
        switch (byte) {
          case 0xf2:  /* REPNE/REPNZ */
          case 0xf3:  /* REP or REPE/REPZ */
          case 0xf0:  /* LOCK */
          case 0x2e:  /* CS segment override -OR- Branch not taken */
          case 0x36:  /* SS segment override -OR- Branch taken */
          case 0x3e:  /* DS segment override */
          case 0x26:  /* ES segment override */
          case 0x64:  /* FS segment override */
          case 0x65:  /* GS segment override */
          case 0x66:  /* Operand-size override */
          case 0x67:  /* Address-size override */
            break;
          default:    /* Not a prefix byte */
            unconsumeByte(insn);
            break;
        }
      } else {
        unconsumeByte(insn);
      }
    }

    /* If we fail reading prefixes, just stop here and let the opcode reader deal with it */
    if (consumeByte(insn, &byte))
      return -1;

    if (insn->readerCursor - 1 == insn->startLocation
        && (byte == 0xf2 || byte == 0xf3)) {
      // prefix requires next byte
      if (lookAtByte(insn, &nextByte))
        return -1;

      /*
       * If the byte is 0xf2 or 0xf3, and any of the following conditions are
       * met:
       * - it is followed by a LOCK (0xf0) prefix
       * - it is followed by an xchg instruction
       * then it should be disassembled as a xacquire/xrelease not repne/rep.
       */
      if (((nextByte == 0xf0) ||
        ((nextByte & 0xfe) == 0x86 || (nextByte & 0xf8) == 0x90))) {
        insn->xAcquireRelease = byte;
      }

      /*
       * Also if the byte is 0xf3, and the following condition is met:
       * - it is followed by a "mov mem, reg" (opcode 0x88/0x89) or
       *                       "mov mem, imm" (opcode 0xc6/0xc7) instructions.
       * then it should be disassembled as an xrelease not rep.
       */
      if (byte == 0xf3 && (nextByte == 0x88 || nextByte == 0x89 ||
            nextByte == 0xc6 || nextByte == 0xc7)) {
        insn->xAcquireRelease = byte;
      }

      if (isREX(insn, nextByte)) {
        uint8_t nnextByte;

        // Go to REX prefix after the current one
        if (consumeByte(insn, &nnextByte))
          return -1;

        // We should be able to read next byte after REX prefix
        if (lookAtByte(insn, &nnextByte))
          return -1;

        unconsumeByte(insn);
      }
    }

    switch (byte) {
      case 0xf0:  /* LOCK */
      case 0xf2:  /* REPNE/REPNZ */
      case 0xf3:  /* REP or REPE/REPZ */
        // only accept the last prefix
        setPrefixPresent(insn, byte);
        insn->prefix0 = byte;
        break;

      case 0x2e:  /* CS segment override -OR- Branch not taken */
      case 0x36:  /* SS segment override -OR- Branch taken */
      case 0x3e:  /* DS segment override */
      case 0x26:  /* ES segment override */
      case 0x64:  /* FS segment override */
      case 0x65:  /* GS segment override */
        switch (byte) {
          case 0x2e:
            insn->segmentOverride = SEG_OVERRIDE_CS;
            insn->prefix1 = byte;
            break;
          case 0x36:
            insn->segmentOverride = SEG_OVERRIDE_SS;
            insn->prefix1 = byte;
            break;
          case 0x3e:
            insn->segmentOverride = SEG_OVERRIDE_DS;
            insn->prefix1 = byte;
            break;
          case 0x26:
            insn->segmentOverride = SEG_OVERRIDE_ES;
            insn->prefix1 = byte;
            break;
          case 0x64:
            insn->segmentOverride = SEG_OVERRIDE_FS;
            insn->prefix1 = byte;
            break;
          case 0x65:
            insn->segmentOverride = SEG_OVERRIDE_GS;
            insn->prefix1 = byte;
            break;
          default:
            // debug("Unhandled override");
            return -1;
        }
        setPrefixPresent(insn, byte);
        break;

      case 0x66:  /* Operand-size override */
        insn->hasOpSize = true;
        setPrefixPresent(insn, byte);
        insn->prefix2 = byte;
        break;

      case 0x67:  /* Address-size override */
        insn->hasAdSize = true;
        setPrefixPresent(insn, byte);
        insn->prefix3 = byte;
        break;
      default:    /* Not a prefix byte */
        isPrefix = false;
        break;
    }
  }

  insn->vectorExtensionType = TYPE_NO_VEX_XOP;

  if (byte == 0x62) {
    uint8_t byte1, byte2;

    if (consumeByte(insn, &byte1)) {
      // dbgprintf(insn, "Couldn't read second byte of EVEX prefix");
      return -1;
    }

    if (lookAtByte(insn, &byte2)) {
      // dbgprintf(insn, "Couldn't read third byte of EVEX prefix");
      unconsumeByte(insn); /* unconsume byte1 */
      unconsumeByte(insn); /* unconsume byte  */
    } else {
      if ((insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0) &&
          ((~byte1 & 0xc) == 0xc) && ((byte2 & 0x4) == 0x4)) {
        insn->vectorExtensionType = TYPE_EVEX;
      } else {
        unconsumeByte(insn); /* unconsume byte1 */
        unconsumeByte(insn); /* unconsume byte  */
      }
    }

    if (insn->vectorExtensionType == TYPE_EVEX) {
      insn->vectorExtensionPrefix[0] = byte;
      insn->vectorExtensionPrefix[1] = byte1;
      if (consumeByte(insn, &insn->vectorExtensionPrefix[2])) {
        // dbgprintf(insn, "Couldn't read third byte of EVEX prefix");
        return -1;
      }

      if (consumeByte(insn, &insn->vectorExtensionPrefix[3])) {
        // dbgprintf(insn, "Couldn't read fourth byte of EVEX prefix");
        return -1;
      }

      /* We simulate the REX prefix for simplicity's sake */
      if (insn->mode == MODE_64BIT) {
        insn->rexPrefix = 0x40
          | (wFromEVEX3of4(insn->vectorExtensionPrefix[2]) << 3)
          | (rFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 2)
          | (xFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 1)
          | (bFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 0);
      }

      // dbgprintf(insn, "Found EVEX prefix 0x%hhx 0x%hhx 0x%hhx 0x%hhx",
      //    insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1],
      //    insn->vectorExtensionPrefix[2], insn->vectorExtensionPrefix[3]);
    }
  } else if (byte == 0xc4) {
    uint8_t byte1;

    if (lookAtByte(insn, &byte1)) {
      // dbgprintf(insn, "Couldn't read second byte of VEX");
      return -1;
    }

    if (insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0)
      insn->vectorExtensionType = TYPE_VEX_3B;
    else
      unconsumeByte(insn);

    if (insn->vectorExtensionType == TYPE_VEX_3B) {
      insn->vectorExtensionPrefix[0] = byte;
      consumeByte(insn, &insn->vectorExtensionPrefix[1]);
      consumeByte(insn, &insn->vectorExtensionPrefix[2]);

      /* We simulate the REX prefix for simplicity's sake */
      if (insn->mode == MODE_64BIT)
        insn->rexPrefix = 0x40
          | (wFromVEX3of3(insn->vectorExtensionPrefix[2]) << 3)
          | (rFromVEX2of3(insn->vectorExtensionPrefix[1]) << 2)
          | (xFromVEX2of3(insn->vectorExtensionPrefix[1]) << 1)
          | (bFromVEX2of3(insn->vectorExtensionPrefix[1]) << 0);

      // dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx 0x%hhx",
      //    insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1],
      //    insn->vectorExtensionPrefix[2]);
    }
  } else if (byte == 0xc5) {
    uint8_t byte1;

    if (lookAtByte(insn, &byte1)) {
      // dbgprintf(insn, "Couldn't read second byte of VEX");
      return -1;
    }

    if (insn->mode == MODE_64BIT || (byte1 & 0xc0) == 0xc0)
      insn->vectorExtensionType = TYPE_VEX_2B;
    else
      unconsumeByte(insn);

    if (insn->vectorExtensionType == TYPE_VEX_2B) {
      insn->vectorExtensionPrefix[0] = byte;
      consumeByte(insn, &insn->vectorExtensionPrefix[1]);

      if (insn->mode == MODE_64BIT)
        insn->rexPrefix = 0x40
          | (rFromVEX2of2(insn->vectorExtensionPrefix[1]) << 2);

      switch (ppFromVEX2of2(insn->vectorExtensionPrefix[1])) {
        default:
          break;
        case VEX_PREFIX_66:
          insn->hasOpSize = true;
          break;
      }

      // dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx",
      //    insn->vectorExtensionPrefix[0],
      //    insn->vectorExtensionPrefix[1]);
    }
  } else if (byte == 0x8f) {
    uint8_t byte1;

    if (lookAtByte(insn, &byte1)) {
      // dbgprintf(insn, "Couldn't read second byte of XOP");
      return -1;
    }

    if ((byte1 & 0x38) != 0x0) /* 0 in these 3 bits is a POP instruction. */
      insn->vectorExtensionType = TYPE_XOP;
    else
      unconsumeByte(insn);

    if (insn->vectorExtensionType == TYPE_XOP) {
      insn->vectorExtensionPrefix[0] = byte;
      consumeByte(insn, &insn->vectorExtensionPrefix[1]);
      consumeByte(insn, &insn->vectorExtensionPrefix[2]);

      /* We simulate the REX prefix for simplicity's sake */
      if (insn->mode == MODE_64BIT)
        insn->rexPrefix = 0x40
          | (wFromXOP3of3(insn->vectorExtensionPrefix[2]) << 3)
          | (rFromXOP2of3(insn->vectorExtensionPrefix[1]) << 2)
          | (xFromXOP2of3(insn->vectorExtensionPrefix[1]) << 1)
          | (bFromXOP2of3(insn->vectorExtensionPrefix[1]) << 0);

      switch (ppFromXOP3of3(insn->vectorExtensionPrefix[2])) {
        default:
          break;
        case VEX_PREFIX_66:
          insn->hasOpSize = true;
          break;
      }

      // dbgprintf(insn, "Found XOP prefix 0x%hhx 0x%hhx 0x%hhx",
      //    insn->vectorExtensionPrefix[0], insn->vectorExtensionPrefix[1],
      //    insn->vectorExtensionPrefix[2]);
    }
  } else if (isREX(insn, byte)) {
    if (lookAtByte(insn, &nextByte))
      return -1;

    insn->rexPrefix = byte;
    // dbgprintf(insn, "Found REX prefix 0x%hhx", byte);
  } else
    unconsumeByte(insn);

  if (insn->mode == MODE_16BIT) {
    insn->registerSize = (insn->hasOpSize ? 4 : 2);
    insn->addressSize = (insn->hasAdSize ? 4 : 2);
    insn->displacementSize = (insn->hasAdSize ? 4 : 2);
    insn->immediateSize = (insn->hasOpSize ? 4 : 2);
    insn->immSize = (insn->hasOpSize ? 4 : 2);
  } else if (insn->mode == MODE_32BIT) {
    insn->registerSize = (insn->hasOpSize ? 2 : 4);
    insn->addressSize = (insn->hasAdSize ? 2 : 4);
    insn->displacementSize = (insn->hasAdSize ? 2 : 4);
    insn->immediateSize = (insn->hasOpSize ? 2 : 4);
    insn->immSize = (insn->hasOpSize ? 2 : 4);
  } else if (insn->mode == MODE_64BIT) {
    if (insn->rexPrefix && wFromREX(insn->rexPrefix)) {
      insn->registerSize       = 8;
      insn->addressSize = (insn->hasAdSize ? 4 : 8);
      insn->displacementSize   = 4;
      insn->immediateSize      = 4;
      insn->immSize      = 4;
    } else {
      insn->registerSize = (insn->hasOpSize ? 2 : 4);
      insn->addressSize = (insn->hasAdSize ? 4 : 8);
      insn->displacementSize = (insn->hasOpSize ? 2 : 4);
      insn->immediateSize = (insn->hasOpSize ? 2 : 4);
      insn->immSize      = (insn->hasOpSize ? 4 : 8);
    }
  }

  return 0;
}

static int readModRM(struct InternalInstruction* insn);

/*
 * readOpcode - Reads the opcode (excepting the ModR/M byte in the case of
 *   extended or escape opcodes).
 *
 * @param insn  - The instruction whose opcode is to be read.
 * @return      - 0 if the opcode could be read successfully; nonzero otherwise.
 */
static int readOpcode(struct InternalInstruction* insn)
{
  uint8_t current;

  // dbgprintf(insn, "readOpcode()");

  insn->opcodeType = ONEBYTE;

  if (insn->vectorExtensionType == TYPE_EVEX) {
    switch (mmFromEVEX2of4(insn->vectorExtensionPrefix[1])) {
      default:
        // dbgprintf(insn, "Unhandled mm field for instruction (0x%hhx)",
        //    mmFromEVEX2of4(insn->vectorExtensionPrefix[1]));
        return -1;
      case VEX_LOB_0F:
        insn->opcodeType = TWOBYTE;
        return consumeByte(insn, &insn->opcode);
      case VEX_LOB_0F38:
        insn->opcodeType = THREEBYTE_38;
        return consumeByte(insn, &insn->opcode);
      case VEX_LOB_0F3A:
        insn->opcodeType = THREEBYTE_3A;
        return consumeByte(insn, &insn->opcode);
    }
  } else if (insn->vectorExtensionType == TYPE_VEX_3B) {
    switch (mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1])) {
      default:
        // dbgprintf(insn, "Unhandled m-mmmm field for instruction (0x%hhx)",
        //    mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1]));
        return -1;
      case VEX_LOB_0F:
        //insn->twoByteEscape = 0x0f;
        insn->opcodeType = TWOBYTE;
        return consumeByte(insn, &insn->opcode);
      case VEX_LOB_0F38:
        //insn->twoByteEscape = 0x0f;
        insn->opcodeType = THREEBYTE_38;
        return consumeByte(insn, &insn->opcode);
      case VEX_LOB_0F3A:
        //insn->twoByteEscape = 0x0f;
        insn->opcodeType = THREEBYTE_3A;
        return consumeByte(insn, &insn->opcode);
    }
  } else if (insn->vectorExtensionType == TYPE_VEX_2B) {
    //insn->twoByteEscape = 0x0f;
    insn->opcodeType = TWOBYTE;
    return consumeByte(insn, &insn->opcode);
  } else if (insn->vectorExtensionType == TYPE_XOP) {
    switch (mmmmmFromXOP2of3(insn->vectorExtensionPrefix[1])) {
      default:
        // dbgprintf(insn, "Unhandled m-mmmm field for instruction (0x%hhx)",
        //    mmmmmFromVEX2of3(insn->vectorExtensionPrefix[1]));
        return -1;
      case XOP_MAP_SELECT_8:
        insn->opcodeType = XOP8_MAP;
        return consumeByte(insn, &insn->opcode);
      case XOP_MAP_SELECT_9:
        insn->opcodeType = XOP9_MAP;
        return consumeByte(insn, &insn->opcode);
      case XOP_MAP_SELECT_A:
        insn->opcodeType = XOPA_MAP;
        return consumeByte(insn, &insn->opcode);
    }
  }

  if (consumeByte(insn, &current))
    return -1;

    // save this first byte for MOVcr, MOVdr, MOVrc, MOVrd
    insn->firstByte = current;

  if (current == 0x0f) {
    // dbgprintf(insn, "Found a two-byte escape prefix (0x%hhx)", current);
    insn->twoByteEscape = current;

    if (consumeByte(insn, &current))
      return -1;

    if (current == 0x38) {
      // dbgprintf(insn, "Found a three-byte escape prefix (0x%hhx)", current);
      if (consumeByte(insn, &current))
        return -1;

      insn->opcodeType = THREEBYTE_38;
    } else if (current == 0x3a) {
      // dbgprintf(insn, "Found a three-byte escape prefix (0x%hhx)", current);
      if (consumeByte(insn, &current))
        return -1;

      insn->opcodeType = THREEBYTE_3A;
    } else if (current == 0x0f) {
      // dbgprintf(insn, "Found a 3dnow escape prefix (0x%hhx)", current);
      // Consume operands before the opcode to comply with the 3DNow encoding
      if (readModRM(insn))
        return -1;

      if (consumeByte(insn, &current))
        return -1;

      insn->opcodeType = THREEDNOW_MAP;
    } else {
      // dbgprintf(insn, "Didn't find a three-byte escape prefix");
      insn->opcodeType = TWOBYTE;
    }
  } else if (insn->mandatoryPrefix)
    // The opcode with mandatory prefix must start with opcode escape.
    // If not it's legacy repeat prefix
    insn->mandatoryPrefix = 0;

  /*
   * At this point we have consumed the full opcode.
   * Anything we consume from here on must be unconsumed.
   */

  insn->opcode = current;

  return 0;
}

// Hacky for FEMMS
#define GET_INSTRINFO_ENUM
#ifndef CAPSTONE_X86_REDUCE
#include "X86GenInstrInfo.inc"
#else
#include "X86GenInstrInfo_reduce.inc"
#endif

/*
 * getIDWithAttrMask - Determines the ID of an instruction, consuming
 *   the ModR/M byte as appropriate for extended and escape opcodes,
 *   and using a supplied attribute mask.
 *
 * @param instructionID - A pointer whose target is filled in with the ID of the
 *                        instruction.
 * @param insn          - The instruction whose ID is to be determined.
 * @param attrMask      - The attribute mask to search.
 * @return              - 0 if the ModR/M could be read when needed or was not
 *                        needed; nonzero otherwise.
 */
static int getIDWithAttrMask(uint16_t *instructionID,
                             struct InternalInstruction* insn,
                             uint16_t attrMask)
{
  bool hasModRMExtension;

  InstructionContext instructionClass = contextForAttrs(attrMask);

  hasModRMExtension = modRMRequired(insn->opcodeType,
      instructionClass,
      insn->opcode);

  if (hasModRMExtension) {
    if (readModRM(insn))
      return -1;

    *instructionID = decode(insn->opcodeType,
        instructionClass,
        insn->opcode,
        insn->modRM);
  } else {
    *instructionID = decode(insn->opcodeType,
        instructionClass,
        insn->opcode,
        0);
  }

  return 0;
}

/*
 * is16BitEquivalent - Determines whether two instruction names refer to
 * equivalent instructions but one is 16-bit whereas the other is not.
 *
 * @param orig  - The instruction ID that is not 16-bit
 * @param equiv - The instruction ID that is 16-bit
 */
static bool is16BitEquivalent(unsigned orig, unsigned equiv)
{
  size_t i;
  uint16_t idx;

  if ((idx = x86_16_bit_eq_lookup[orig]) != 0) {
    for (i = idx - 1; i < ARR_SIZE(x86_16_bit_eq_tbl) && x86_16_bit_eq_tbl[i].first == orig; i++) {
      if (x86_16_bit_eq_tbl[i].second == equiv)
        return true;
    }
  }

  return false;
}

/*
 * is64Bit - Determines whether this instruction is a 64-bit instruction.
 *
 * @param name - The instruction that is not 16-bit
 */
static bool is64Bit(uint16_t id)
{
  unsigned int i = find_insn(id);
  if (i != -1) {
    return insns[i].is64bit;
  }

  // not found??
  return false;
}

/*
 * getID - Determines the ID of an instruction, consuming the ModR/M byte as
 *   appropriate for extended and escape opcodes.  Determines the attributes and
 *   context for the instruction before doing so.
 *
 * @param insn  - The instruction whose ID is to be determined.
 * @return      - 0 if the ModR/M could be read when needed or was not needed;
 *                nonzero otherwise.
 */
static int getID(struct InternalInstruction *insn)
{
  uint16_t attrMask;
  uint16_t instructionID;

  attrMask = ATTR_NONE;

  if (insn->mode == MODE_64BIT)
    attrMask |= ATTR_64BIT;

  if (insn->vectorExtensionType != TYPE_NO_VEX_XOP) {
    attrMask |= (insn->vectorExtensionType == TYPE_EVEX) ? ATTR_EVEX : ATTR_VEX;

    if (insn->vectorExtensionType == TYPE_EVEX) {
      switch (ppFromEVEX3of4(insn->vectorExtensionPrefix[2])) {
        case VEX_PREFIX_66:
          attrMask |= ATTR_OPSIZE;
          break;
        case VEX_PREFIX_F3:
          attrMask |= ATTR_XS;
          break;
        case VEX_PREFIX_F2:
          attrMask |= ATTR_XD;
          break;
      }

      if (zFromEVEX4of4(insn->vectorExtensionPrefix[3]))
        attrMask |= ATTR_EVEXKZ;
      if (bFromEVEX4of4(insn->vectorExtensionPrefix[3]))
        attrMask |= ATTR_EVEXB;
      if (aaaFromEVEX4of4(insn->vectorExtensionPrefix[3]))
        attrMask |= ATTR_EVEXK;
      if (lFromEVEX4of4(insn->vectorExtensionPrefix[3]))
        attrMask |= ATTR_EVEXL;
      if (l2FromEVEX4of4(insn->vectorExtensionPrefix[3]))
        attrMask |= ATTR_EVEXL2;
    } else if (insn->vectorExtensionType == TYPE_VEX_3B) {
      switch (ppFromVEX3of3(insn->vectorExtensionPrefix[2])) {
        case VEX_PREFIX_66:
          attrMask |= ATTR_OPSIZE;
          break;
        case VEX_PREFIX_F3:
          attrMask |= ATTR_XS;
          break;
        case VEX_PREFIX_F2:
          attrMask |= ATTR_XD;
          break;
      }

      if (lFromVEX3of3(insn->vectorExtensionPrefix[2]))
        attrMask |= ATTR_VEXL;
    } else if (insn->vectorExtensionType == TYPE_VEX_2B) {
      switch (ppFromVEX2of2(insn->vectorExtensionPrefix[1])) {
        case VEX_PREFIX_66:
          attrMask |= ATTR_OPSIZE;
          break;
        case VEX_PREFIX_F3:
          attrMask |= ATTR_XS;
          break;
        case VEX_PREFIX_F2:
          attrMask |= ATTR_XD;
          break;
      }

      if (lFromVEX2of2(insn->vectorExtensionPrefix[1]))
        attrMask |= ATTR_VEXL;
    } else if (insn->vectorExtensionType == TYPE_XOP) {
      switch (ppFromXOP3of3(insn->vectorExtensionPrefix[2])) {
        case VEX_PREFIX_66:
          attrMask |= ATTR_OPSIZE;
          break;
        case VEX_PREFIX_F3:
          attrMask |= ATTR_XS;
          break;
        case VEX_PREFIX_F2:
          attrMask |= ATTR_XD;
          break;
      }

      if (lFromXOP3of3(insn->vectorExtensionPrefix[2]))
        attrMask |= ATTR_VEXL;
    } else {
      return -1;
    }
  } else if (!insn->mandatoryPrefix) {
    // If we don't have mandatory prefix we should use legacy prefixes here
    if (insn->hasOpSize && (insn->mode != MODE_16BIT))
      attrMask |= ATTR_OPSIZE;
    if (insn->hasAdSize)
      attrMask |= ATTR_ADSIZE;
    if (insn->opcodeType == ONEBYTE) {
      if (insn->repeatPrefix == 0xf3 && (insn->opcode == 0x90))
        // Special support for PAUSE
        attrMask |= ATTR_XS;
    } else {
      if (insn->repeatPrefix == 0xf2)
        attrMask |= ATTR_XD;
      else if (insn->repeatPrefix == 0xf3)
        attrMask |= ATTR_XS;
    }
  } else {
    switch (insn->mandatoryPrefix) {
      case 0xf2:
        attrMask |= ATTR_XD;
        break;
      case 0xf3:
        attrMask |= ATTR_XS;
        break;
      case 0x66:
        if (insn->mode != MODE_16BIT)
          attrMask |= ATTR_OPSIZE;
        break;
      case 0x67:
        attrMask |= ATTR_ADSIZE;
        break;
    }

  }

  if (insn->rexPrefix & 0x08) {
    attrMask |= ATTR_REXW;
    attrMask &= ~ATTR_ADSIZE;
  }

  /*
   * JCXZ/JECXZ need special handling for 16-bit mode because the meaning
   * of the AdSize prefix is inverted w.r.t. 32-bit mode.
   */
  if (insn->mode == MODE_16BIT && insn->opcodeType == ONEBYTE &&
      insn->opcode == 0xE3)
    attrMask ^= ATTR_ADSIZE;

  /*
   * In 64-bit mode all f64 superscripted opcodes ignore opcode size prefix
   * CALL/JMP/JCC instructions need to ignore 0x66 and consume 4 bytes
   */
  if ((insn->mode == MODE_64BIT) && insn->hasOpSize) {
    switch (insn->opcode) {
      case 0xE8:
      case 0xE9:
        // Take care of psubsb and other mmx instructions.
        if (insn->opcodeType == ONEBYTE) {
          attrMask ^= ATTR_OPSIZE;
          insn->immediateSize = 4;
          insn->displacementSize = 4;
        }
        break;
      case 0x82:
      case 0x83:
      case 0x84:
      case 0x85:
      case 0x86:
      case 0x87:
      case 0x88:
      case 0x89:
      case 0x8A:
      case 0x8B:
      case 0x8C:
      case 0x8D:
      case 0x8E:
      case 0x8F:
        // Take care of lea and three byte ops.
        if (insn->opcodeType == TWOBYTE) {
          attrMask ^= ATTR_OPSIZE;
          insn->immediateSize = 4;
          insn->displacementSize = 4;
        }
        break;
    }
  }

  /* The following clauses compensate for limitations of the tables. */
  if (insn->mode != MODE_64BIT &&
      insn->vectorExtensionType != TYPE_NO_VEX_XOP) {
    if (getIDWithAttrMask(&instructionID, insn, attrMask)) {
      return -1;
    }

    /*
     * The tables can't distinquish between cases where the W-bit is used to
     * select register size and cases where its a required part of the opcode.
     */
    if ((insn->vectorExtensionType == TYPE_EVEX &&
          wFromEVEX3of4(insn->vectorExtensionPrefix[2])) ||
        (insn->vectorExtensionType == TYPE_VEX_3B &&
         wFromVEX3of3(insn->vectorExtensionPrefix[2])) ||
        (insn->vectorExtensionType == TYPE_XOP &&
         wFromXOP3of3(insn->vectorExtensionPrefix[2]))) {
      uint16_t instructionIDWithREXW;

      if (getIDWithAttrMask(&instructionIDWithREXW,
            insn, attrMask | ATTR_REXW)) {
        insn->instructionID = instructionID;
        insn->spec = specifierForUID(instructionID);
        return 0;
      }

      // If not a 64-bit instruction. Switch the opcode.
      if (!is64Bit(instructionIDWithREXW)) {
        insn->instructionID = instructionIDWithREXW;
        insn->spec = specifierForUID(instructionIDWithREXW);

        return 0;
      }
    }
  }

  /*
   * Absolute moves, umonitor, and movdir64b need special handling.
   * -For 16-bit mode because the meaning of the AdSize and OpSize prefixes are
   *  inverted w.r.t.
   * -For 32-bit mode we need to ensure the ADSIZE prefix is observed in
   *  any position.
   */
  if ((insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0)) ||
      (insn->opcodeType == TWOBYTE && (insn->opcode == 0xAE)) ||
      (insn->opcodeType == THREEBYTE_38 && insn->opcode == 0xF8)) {
    /* Make sure we observed the prefixes in any position. */
    if (insn->hasAdSize)
      attrMask |= ATTR_ADSIZE;

    if (insn->hasOpSize)
      attrMask |= ATTR_OPSIZE;

    /* In 16-bit, invert the attributes. */
    if (insn->mode == MODE_16BIT) {
      attrMask ^= ATTR_ADSIZE;

      /* The OpSize attribute is only valid with the absolute moves. */
      if (insn->opcodeType == ONEBYTE && ((insn->opcode & 0xFC) == 0xA0))
        attrMask ^= ATTR_OPSIZE;
    }

    if (getIDWithAttrMask(&instructionID, insn, attrMask)) {
      return -1;
    }

    insn->instructionID = instructionID;
    insn->spec = specifierForUID(instructionID);

    return 0;
  }
  if (getIDWithAttrMask(&instructionID, insn, attrMask)) {
    return -1;
  }

  if ((insn->mode == MODE_16BIT || insn->hasOpSize) &&
      !(attrMask & ATTR_OPSIZE)) {
    /*
     * The instruction tables make no distinction between instructions that
     * allow OpSize anywhere (i.e., 16-bit operations) and that need it in a
     * particular spot (i.e., many MMX operations).  In general we're
     * conservative, but in the specific case where OpSize is present but not
     * in the right place we check if there's a 16-bit operation.
     */
    const struct InstructionSpecifier *spec;
    uint16_t instructionIDWithOpsize;

    spec = specifierForUID(instructionID);

    if (getIDWithAttrMask(&instructionIDWithOpsize,
          insn,
          attrMask | ATTR_OPSIZE)) {
      /*
       * ModRM required with OpSize but not present; give up and return version
       * without OpSize set
       */
      insn->instructionID = instructionID;
      insn->spec = spec;

      return 0;
    }

    if (is16BitEquivalent(instructionID, instructionIDWithOpsize) &&
        (insn->mode == MODE_16BIT) ^ insn->hasOpSize) {
      insn->instructionID = instructionIDWithOpsize;
      insn->spec = specifierForUID(instructionIDWithOpsize);
    } else {
      insn->instructionID = instructionID;
      insn->spec = spec;
    }

    return 0;
  }

  if (insn->opcodeType == ONEBYTE && insn->opcode == 0x90 &&
      insn->rexPrefix & 0x01) {
    /*
     * NOOP shouldn't decode as NOOP if REX.b is set. Instead
     * it should decode as XCHG %r8, %eax.
     */
    const struct InstructionSpecifier *spec;
    uint16_t instructionIDWithNewOpcode;
    const struct InstructionSpecifier *specWithNewOpcode;

    spec = specifierForUID(instructionID);

    /* Borrow opcode from one of the other XCHGar opcodes */
    insn->opcode = 0x91;

    if (getIDWithAttrMask(&instructionIDWithNewOpcode, insn, attrMask)) {
      insn->opcode = 0x90;

      insn->instructionID = instructionID;
      insn->spec = spec;

      return 0;
    }

    specWithNewOpcode = specifierForUID(instructionIDWithNewOpcode);

    /* Change back */
    insn->opcode = 0x90;

    insn->instructionID = instructionIDWithNewOpcode;
    insn->spec = specWithNewOpcode;

    return 0;
  }

  insn->instructionID = instructionID;
  insn->spec = specifierForUID(insn->instructionID);

  return 0;
}

/*
 * readSIB - Consumes the SIB byte to determine addressing information for an
 *   instruction.
 *
 * @param insn  - The instruction whose SIB byte is to be read.
 * @return      - 0 if the SIB byte was successfully read; nonzero otherwise.
 */
static int readSIB(struct InternalInstruction* insn)
{
  SIBBase sibBaseBase = SIB_BASE_NONE;
  uint8_t index, base;

  // dbgprintf(insn, "readSIB()");

  if (insn->consumedSIB)
    return 0;

  insn->consumedSIB = true;

  switch (insn->addressSize) {
    case 2:
      // dbgprintf(insn, "SIB-based addressing doesn't work in 16-bit mode");
      return -1;
    case 4:
      insn->sibIndexBase = SIB_INDEX_EAX;
      sibBaseBase = SIB_BASE_EAX;
      break;
    case 8:
      insn->sibIndexBase = SIB_INDEX_RAX;
      sibBaseBase = SIB_BASE_RAX;
      break;
  }

  if (consumeByte(insn, &insn->sib))
    return -1;

  index = indexFromSIB(insn->sib) | (xFromREX(insn->rexPrefix) << 3);

  if (index == 0x4) {
    insn->sibIndex = SIB_INDEX_NONE;
  } else {
    insn->sibIndex = (SIBIndex)(insn->sibIndexBase + index);
  }

  insn->sibScale = 1 << scaleFromSIB(insn->sib);

  base = baseFromSIB(insn->sib) | (bFromREX(insn->rexPrefix) << 3);

  switch (base) {
    case 0x5:
    case 0xd:
      switch (modFromModRM(insn->modRM)) {
        case 0x0:
          insn->eaDisplacement = EA_DISP_32;
          insn->sibBase = SIB_BASE_NONE;
          break;
        case 0x1:
          insn->eaDisplacement = EA_DISP_8;
          insn->sibBase = (SIBBase)(sibBaseBase + base);
          break;
        case 0x2:
          insn->eaDisplacement = EA_DISP_32;
          insn->sibBase = (SIBBase)(sibBaseBase + base);
          break;
        case 0x3:
          // debug("Cannot have Mod = 0b11 and a SIB byte");
          return -1;
      }
      break;
    default:
      insn->sibBase = (SIBBase)(sibBaseBase + base);
      break;
  }

  return 0;
}

/*
 * readDisplacement - Consumes the displacement of an instruction.
 *
 * @param insn  - The instruction whose displacement is to be read.
 * @return      - 0 if the displacement byte was successfully read; nonzero
 *                otherwise.
 */
static int readDisplacement(struct InternalInstruction* insn)
{
  int8_t d8;
  int16_t d16;
  int32_t d32;

  // dbgprintf(insn, "readDisplacement()");

  if (insn->consumedDisplacement)
    return 0;

  insn->consumedDisplacement = true;
  insn->displacementOffset = insn->readerCursor - insn->startLocation;

  switch (insn->eaDisplacement) {
    case EA_DISP_NONE:
      insn->consumedDisplacement = false;
      break;
    case EA_DISP_8:
      if (consumeInt8(insn, &d8))
        return -1;
      insn->displacement = d8;
      break;
    case EA_DISP_16:
      if (consumeInt16(insn, &d16))
        return -1;
      insn->displacement = d16;
      break;
    case EA_DISP_32:
      if (consumeInt32(insn, &d32))
        return -1;
      insn->displacement = d32;
      break;
  }


  return 0;
}

/*
 * readModRM - Consumes all addressing information (ModR/M byte, SIB byte, and
 *   displacement) for an instruction and interprets it.
 *
 * @param insn  - The instruction whose addressing information is to be read.
 * @return      - 0 if the information was successfully read; nonzero otherwise.
 */
static int readModRM(struct InternalInstruction* insn)
{
  uint8_t mod, rm, reg, evexrm;

  // dbgprintf(insn, "readModRM()");

  if (insn->consumedModRM)
    return 0;

  insn->modRMOffset = (uint8_t)(insn->readerCursor - insn->startLocation);

  if (consumeByte(insn, &insn->modRM))
    return -1;

  insn->consumedModRM = true;

  // save original ModRM for later reference
  insn->orgModRM = insn->modRM;

  // handle MOVcr, MOVdr, MOVrc, MOVrd by pretending they have MRM.mod = 3
  if ((insn->firstByte == 0x0f && insn->opcodeType == TWOBYTE) &&
      (insn->opcode >= 0x20 && insn->opcode <= 0x23 ))
    insn->modRM |= 0xC0;

  mod = modFromModRM(insn->modRM);
  rm  = rmFromModRM(insn->modRM);
  reg = regFromModRM(insn->modRM);

  /*
   * This goes by insn->registerSize to pick the correct register, which messes
   * up if we're using (say) XMM or 8-bit register operands.  That gets fixed in
   * fixupReg().
   */
  switch (insn->registerSize) {
    case 2:
      insn->regBase = MODRM_REG_AX;
      insn->eaRegBase = EA_REG_AX;
      break;
    case 4:
      insn->regBase = MODRM_REG_EAX;
      insn->eaRegBase = EA_REG_EAX;
      break;
    case 8:
      insn->regBase = MODRM_REG_RAX;
      insn->eaRegBase = EA_REG_RAX;
      break;
  }

  reg |= rFromREX(insn->rexPrefix) << 3;
  rm  |= bFromREX(insn->rexPrefix) << 3;

  evexrm = 0;
  if (insn->vectorExtensionType == TYPE_EVEX && insn->mode == MODE_64BIT) {
    reg |= r2FromEVEX2of4(insn->vectorExtensionPrefix[1]) << 4;
    evexrm = xFromEVEX2of4(insn->vectorExtensionPrefix[1]) << 4;
  }

  insn->reg = (Reg)(insn->regBase + reg);

  switch (insn->addressSize) {
    case 2: {
      EABase eaBaseBase = EA_BASE_BX_SI;

      switch (mod) {
        case 0x0:
          if (rm == 0x6) {
            insn->eaBase = EA_BASE_NONE;
            insn->eaDisplacement = EA_DISP_16;
            if (readDisplacement(insn))
              return -1;
          } else {
            insn->eaBase = (EABase)(eaBaseBase + rm);
            insn->eaDisplacement = EA_DISP_NONE;
          }
          break;
        case 0x1:
          insn->eaBase = (EABase)(eaBaseBase + rm);
          insn->eaDisplacement = EA_DISP_8;
          insn->displacementSize = 1;
          if (readDisplacement(insn))
            return -1;
          break;
        case 0x2:
          insn->eaBase = (EABase)(eaBaseBase + rm);
          insn->eaDisplacement = EA_DISP_16;
          if (readDisplacement(insn))
            return -1;
          break;
        case 0x3:
          insn->eaBase = (EABase)(insn->eaRegBase + rm);
          if (readDisplacement(insn))
            return -1;
          break;
      }
      break;
    }

    case 4:
    case 8: {
      EABase eaBaseBase = (insn->addressSize == 4 ? EA_BASE_EAX : EA_BASE_RAX);

      switch (mod) {
        default: break;
        case 0x0:
          insn->eaDisplacement = EA_DISP_NONE; /* readSIB may override this */
          // In determining whether RIP-relative mode is used (rm=5),
          // or whether a SIB byte is present (rm=4),
          // the extension bits (REX.b and EVEX.x) are ignored.
          switch (rm & 7) {
            case 0x4: // SIB byte is present
              insn->eaBase = (insn->addressSize == 4 ?
                  EA_BASE_sib : EA_BASE_sib64);
              if (readSIB(insn) || readDisplacement(insn))
                return -1;
              break;
            case 0x5: // RIP-relative
              insn->eaBase = EA_BASE_NONE;
              insn->eaDisplacement = EA_DISP_32;
              if (readDisplacement(insn))
                return -1;
              break;
            default:
              insn->eaBase = (EABase)(eaBaseBase + rm);
              break;
          }
          break;
        case 0x1:
          insn->displacementSize = 1;
          /* FALLTHROUGH */
        case 0x2:
          insn->eaDisplacement = (mod == 0x1 ? EA_DISP_8 : EA_DISP_32);
          switch (rm & 7) {
            case 0x4: // SIB byte is present
              insn->eaBase = EA_BASE_sib;
              if (readSIB(insn) || readDisplacement(insn))
                return -1;
              break;
            default:
              insn->eaBase = (EABase)(eaBaseBase + rm);
              if (readDisplacement(insn))
                return -1;
              break;
          }
          break;
        case 0x3:
          insn->eaDisplacement = EA_DISP_NONE;
          insn->eaBase = (EABase)(insn->eaRegBase + rm + evexrm);
          break;
      }

      break;
    }
  } /* switch (insn->addressSize) */

  return 0;
}

#define GENERIC_FIXUP_FUNC(name, base, prefix, mask)      \
  static uint16_t name(struct InternalInstruction *insn,  \
                       OperandType type,                  \
                       uint8_t index,                     \
                       uint8_t *valid) {                  \
    *valid = 1;                                           \
    switch (type) {                                       \
    default:                                              \
      *valid = 0;                                         \
      return 0;                                           \
    case TYPE_Rv:                                         \
      return base + index;                                \
    case TYPE_R8:                                         \
      index &= mask;                                      \
      if (index > 0xf)                                    \
        *valid = 0;                                       \
      if (insn->rexPrefix &&                              \
         index >= 4 && index <= 7) {                      \
        return prefix##_SPL + (index - 4);                \
      } else {                                            \
        return prefix##_AL + index;                       \
      }                                                   \
    case TYPE_R16:                                        \
      index &= mask;                                      \
      if (index > 0xf)                                    \
        *valid = 0;                                       \
      return prefix##_AX + index;                         \
    case TYPE_R32:                                        \
      index &= mask;                                      \
      if (index > 0xf)                                    \
        *valid = 0;                                       \
      return prefix##_EAX + index;                        \
    case TYPE_R64:                                        \
      index &= mask;                                      \
      if (index > 0xf)                                    \
        *valid = 0;                                       \
      return prefix##_RAX + index;                        \
    case TYPE_ZMM:                                        \
      return prefix##_ZMM0 + index;                       \
    case TYPE_YMM:                                        \
      return prefix##_YMM0 + index;                       \
    case TYPE_XMM:                                        \
      return prefix##_XMM0 + index;                       \
    case TYPE_VK:                                         \
      index &= 0xf;                                       \
      if (index > 7)                                      \
        *valid = 0;                                       \
      return prefix##_K0 + index;                         \
    case TYPE_MM64:                                       \
      return prefix##_MM0 + (index & 0x7);                \
    case TYPE_SEGMENTREG:                                 \
      if ((index & 7) > 5)                                \
        *valid = 0;                                       \
      return prefix##_ES + (index & 7);                   \
    case TYPE_DEBUGREG:                                   \
      return prefix##_DR0 + index;                        \
    case TYPE_CONTROLREG:                                 \
      return prefix##_CR0 + index;                        \
    case TYPE_BNDR:                                       \
      if (index > 3)                                      \
        *valid = 0;                                       \
      return prefix##_BND0 + index;                       \
    case TYPE_MVSIBX:                                     \
      return prefix##_XMM0 + index;                       \
    case TYPE_MVSIBY:                                     \
      return prefix##_YMM0 + index;                       \
    case TYPE_MVSIBZ:                                     \
      return prefix##_ZMM0 + index;                       \
    }                                                     \
  }

/*
 * fixup*Value - Consults an operand type to determine the meaning of the
 *   reg or R/M field.  If the operand is an XMM operand, for example, an
 *   operand would be XMM0 instead of AX, which readModRM() would otherwise
 *   misinterpret it as.
 *
 * @param insn  - The instruction containing the operand.
 * @param type  - The operand type.
 * @param index - The existing value of the field as reported by readModRM().
 * @param valid - The address of a uint8_t.  The target is set to 1 if the
 *                field is valid for the register class; 0 if not.
 * @return      - The proper value.
 */
GENERIC_FIXUP_FUNC(fixupRegValue, insn->regBase, MODRM_REG, 0x1f)
GENERIC_FIXUP_FUNC(fixupRMValue, insn->eaRegBase, EA_REG, 0xf)

/*
 * fixupReg - Consults an operand specifier to determine which of the
 *   fixup*Value functions to use in correcting readModRM()'ss interpretation.
 *
 * @param insn  - See fixup*Value().
 * @param op    - The operand specifier.
 * @return      - 0 if fixup was successful; -1 if the register returned was
 *                invalid for its class.
 */
static int fixupReg(struct InternalInstruction *insn,
                    const struct OperandSpecifier *op)
{
  uint8_t valid;

  switch ((OperandEncoding)op->encoding) {
    default:
      // debug("Expected a REG or R/M encoding in fixupReg");
      return -1;
    case ENCODING_VVVV:
      insn->vvvv = (Reg)fixupRegValue(insn,
          (OperandType)op->type,
          insn->vvvv,
          &valid);
      if (!valid)
        return -1;
      break;
    case ENCODING_REG:
      insn->reg = (Reg)fixupRegValue(insn,
          (OperandType)op->type,
          insn->reg - insn->regBase,
          &valid);
      if (!valid)
        return -1;
      break;
    CASE_ENCODING_RM:
      if (insn->eaBase >= insn->eaRegBase) {
        insn->eaBase = (EABase)fixupRMValue(insn,
            (OperandType)op->type,
            insn->eaBase - insn->eaRegBase,
            &valid);
        if (!valid)
          return -1;
      }
      break;
  }

  return 0;
}

/*
 * readOpcodeRegister - Reads an operand from the opcode field of an
 *   instruction and interprets it appropriately given the operand width.
 *   Handles AddRegFrm instructions.
 *
 * @param insn  - the instruction whose opcode field is to be read.
 * @param size  - The width (in bytes) of the register being specified.
 *                1 means AL and friends, 2 means AX, 4 means EAX, and 8 means
 *                RAX.
 * @return      - 0 on success; nonzero otherwise.
 */
static int readOpcodeRegister(struct InternalInstruction* insn, uint8_t size)
{
  if (size == 0)
    size = insn->registerSize;

  switch (size) {
    case 1:
      insn->opcodeRegister = (Reg)(MODRM_REG_AL + ((bFromREX(insn->rexPrefix) << 3)
            | (insn->opcode & 7)));
      if (insn->rexPrefix &&
          insn->opcodeRegister >= MODRM_REG_AL + 0x4 &&
          insn->opcodeRegister < MODRM_REG_AL + 0x8) {
        insn->opcodeRegister = (Reg)(MODRM_REG_SPL
            + (insn->opcodeRegister - MODRM_REG_AL - 4));
      }

      break;
    case 2:
      insn->opcodeRegister = (Reg)(MODRM_REG_AX
          + ((bFromREX(insn->rexPrefix) << 3)
            | (insn->opcode & 7)));
      break;
    case 4:
      insn->opcodeRegister = (Reg)(MODRM_REG_EAX
          + ((bFromREX(insn->rexPrefix) << 3)
            | (insn->opcode & 7)));
      break;
    case 8:
      insn->opcodeRegister = (Reg)(MODRM_REG_RAX
          + ((bFromREX(insn->rexPrefix) << 3)
            | (insn->opcode & 7)));
      break;
  }

  return 0;
}

/*
 * readImmediate - Consumes an immediate operand from an instruction, given the
 *   desired operand size.
 *
 * @param insn  - The instruction whose operand is to be read.
 * @param size  - The width (in bytes) of the operand.
 * @return      - 0 if the immediate was successfully consumed; nonzero
 *                otherwise.
 */
static int readImmediate(struct InternalInstruction* insn, uint8_t size)
{
  uint8_t imm8;
  uint16_t imm16;
  uint32_t imm32;
  uint64_t imm64;

  if (insn->numImmediatesConsumed == 2) {
    // debug("Already consumed two immediates");
    return -1;
  }

  if (size == 0)
    size = insn->immediateSize;
  else
    insn->immediateSize = size;

  insn->immediateOffset = insn->readerCursor - insn->startLocation;

  switch (size) {
    case 1:
      if (consumeByte(insn, &imm8))
        return -1;

      insn->immediates[insn->numImmediatesConsumed] = imm8;
      break;
    case 2:
      if (consumeUInt16(insn, &imm16))
        return -1;

      insn->immediates[insn->numImmediatesConsumed] = imm16;
      break;
    case 4:
      if (consumeUInt32(insn, &imm32))
        return -1;

      insn->immediates[insn->numImmediatesConsumed] = imm32;
      break;
    case 8:
      if (consumeUInt64(insn, &imm64))
        return -1;
      insn->immediates[insn->numImmediatesConsumed] = imm64;
      break;
  }

  insn->numImmediatesConsumed++;

  return 0;
}

/*
 * readVVVV - Consumes vvvv from an instruction if it has a VEX prefix.
 *
 * @param insn  - The instruction whose operand is to be read.
 * @return      - 0 if the vvvv was successfully consumed; nonzero
 *                otherwise.
 */
static int readVVVV(struct InternalInstruction* insn)
{
  int vvvv;

  if (insn->vectorExtensionType == TYPE_EVEX)
    vvvv = (v2FromEVEX4of4(insn->vectorExtensionPrefix[3]) << 4 |
        vvvvFromEVEX3of4(insn->vectorExtensionPrefix[2]));
  else if (insn->vectorExtensionType == TYPE_VEX_3B)
    vvvv = vvvvFromVEX3of3(insn->vectorExtensionPrefix[2]);
  else if (insn->vectorExtensionType == TYPE_VEX_2B)
    vvvv = vvvvFromVEX2of2(insn->vectorExtensionPrefix[1]);
  else if (insn->vectorExtensionType == TYPE_XOP)
    vvvv = vvvvFromXOP3of3(insn->vectorExtensionPrefix[2]);
  else
    return -1;

  if (insn->mode != MODE_64BIT)
    vvvv &= 0xf; // Can only clear bit 4. Bit 3 must be cleared later.

  insn->vvvv = (Reg)vvvv;

  return 0;
}

/*
 * readMaskRegister - Reads an mask register from the opcode field of an
 *   instruction.
 *
 * @param insn    - The instruction whose opcode field is to be read.
 * @return        - 0 on success; nonzero otherwise.
 */
static int readMaskRegister(struct InternalInstruction* insn)
{
  if (insn->vectorExtensionType != TYPE_EVEX)
    return -1;

  insn->writemask = (Reg)(aaaFromEVEX4of4(insn->vectorExtensionPrefix[3]));

  return 0;
}

/*
 * readOperands - Consults the specifier for an instruction and consumes all
 *   operands for that instruction, interpreting them as it goes.
 *
 * @param insn  - The instruction whose operands are to be read and interpreted.
 * @return      - 0 if all operands could be read; nonzero otherwise.
 */
static int readOperands(struct InternalInstruction* insn)
{
  int hasVVVV, needVVVV;
  int sawRegImm = 0;
  int i;

  /* If non-zero vvvv specified, need to make sure one of the operands
     uses it. */
  hasVVVV = !readVVVV(insn);
  needVVVV = hasVVVV && (insn->vvvv != 0);

  for (i = 0; i < X86_MAX_OPERANDS; ++i) {
    const OperandSpecifier *op = &x86OperandSets[insn->spec->operands][i];
    switch (op->encoding) {
      case ENCODING_NONE:
      case ENCODING_SI:
      case ENCODING_DI:
        break;

      CASE_ENCODING_VSIB:
        // VSIB can use the V2 bit so check only the other bits.
        if (needVVVV)
          needVVVV = hasVVVV & ((insn->vvvv & 0xf) != 0);

        if (readModRM(insn))
          return -1;

        // Reject if SIB wasn't used.
        if (insn->eaBase != EA_BASE_sib && insn->eaBase != EA_BASE_sib64)
          return -1;

        // If sibIndex was set to SIB_INDEX_NONE, index offset is 4.
        if (insn->sibIndex == SIB_INDEX_NONE)
          insn->sibIndex = (SIBIndex)(insn->sibIndexBase + 4);

        // If EVEX.v2 is set this is one of the 16-31 registers.
        if (insn->vectorExtensionType == TYPE_EVEX && insn->mode == MODE_64BIT &&
            v2FromEVEX4of4(insn->vectorExtensionPrefix[3]))
          insn->sibIndex = (SIBIndex)(insn->sibIndex + 16);

        // Adjust the index register to the correct size.
        switch (op->type) {
          default:
            // debug("Unhandled VSIB index type");
            return -1;
          case TYPE_MVSIBX:
            insn->sibIndex = (SIBIndex)(SIB_INDEX_XMM0 +
                (insn->sibIndex - insn->sibIndexBase));
            break;
          case TYPE_MVSIBY:
            insn->sibIndex = (SIBIndex)(SIB_INDEX_YMM0 +
                (insn->sibIndex - insn->sibIndexBase));
            break;
          case TYPE_MVSIBZ:
            insn->sibIndex = (SIBIndex)(SIB_INDEX_ZMM0 +
                (insn->sibIndex - insn->sibIndexBase));
            break;
        }

        // Apply the AVX512 compressed displacement scaling factor.
        if (op->encoding != ENCODING_REG && insn->eaDisplacement == EA_DISP_8)
          insn->displacement *= 1 << (op->encoding - ENCODING_VSIB);
        break;

      case ENCODING_REG:
      CASE_ENCODING_RM:
        if (readModRM(insn))
          return -1;

        if (fixupReg(insn, op))
          return -1;

        // Apply the AVX512 compressed displacement scaling factor.
        if (op->encoding != ENCODING_REG && insn->eaDisplacement == EA_DISP_8)
          insn->displacement *= 1 << (op->encoding - ENCODING_RM);
        break;

      case ENCODING_IB:
        if (sawRegImm) {
          /* Saw a register immediate so don't read again and instead split the
             previous immediate.  FIXME: This is a hack. */
          insn->immediates[insn->numImmediatesConsumed] =
            insn->immediates[insn->numImmediatesConsumed - 1] & 0xf;
          ++insn->numImmediatesConsumed;
          break;
        }
        if (readImmediate(insn, 1))
          return -1;
        if (op->type == TYPE_XMM || op->type == TYPE_YMM)
          sawRegImm = 1;
        break;

      case ENCODING_IW:
        if (readImmediate(insn, 2))
          return -1;
        break;

      case ENCODING_ID:
        if (readImmediate(insn, 4))
          return -1;
        break;

      case ENCODING_IO:
        if (readImmediate(insn, 8))
          return -1;
        break;

      case ENCODING_Iv:
        if (readImmediate(insn, insn->immediateSize))
          return -1;
        break;

      case ENCODING_Ia:
        if (readImmediate(insn, insn->addressSize))
          return -1;
        /* Direct memory-offset (moffset) immediate will get mapped
           to memory operand later. We want the encoding info to
           reflect that as well. */
        insn->displacementOffset = insn->immediateOffset;
        insn->consumedDisplacement = true;
        insn->displacementSize = insn->immediateSize;
        insn->displacement = insn->immediates[insn->numImmediatesConsumed - 1];
        insn->immediateOffset = 0;
        insn->immediateSize = 0;
        break;

      case ENCODING_IRC:
        insn->RC = (l2FromEVEX4of4(insn->vectorExtensionPrefix[3]) << 1) |
          lFromEVEX4of4(insn->vectorExtensionPrefix[3]);
        break;

      case ENCODING_RB:
        if (readOpcodeRegister(insn, 1))
          return -1;
        break;

      case ENCODING_RW:
        if (readOpcodeRegister(insn, 2))
          return -1;
        break;

      case ENCODING_RD:
        if (readOpcodeRegister(insn, 4))
          return -1;
        break;

      case ENCODING_RO:
        if (readOpcodeRegister(insn, 8))
          return -1;
        break;

      case ENCODING_Rv:
        if (readOpcodeRegister(insn, 0))
          return -1;
        break;

      case ENCODING_FP:
        break;

      case ENCODING_VVVV:
        if (!hasVVVV)
          return -1;

        needVVVV = 0; /* Mark that we have found a VVVV operand. */

        if (insn->mode != MODE_64BIT)
          insn->vvvv = (Reg)(insn->vvvv & 0x7);

        if (fixupReg(insn, op))
          return -1;
        break;

      case ENCODING_WRITEMASK:
        if (readMaskRegister(insn))
          return -1;
        break;

      case ENCODING_DUP:
        break;

      default:
        // dbgprintf(insn, "Encountered an operand with an unknown encoding.");
        return -1;
    }
  }

  /* If we didn't find ENCODING_VVVV operand, but non-zero vvvv present, fail */
  if (needVVVV)
    return -1;

  return 0;
}

// return True if instruction is illegal to use with prefixes
// This also check & fix the isPrefixNN when a prefix is irrelevant.
static bool checkPrefix(struct InternalInstruction *insn)
{
  // LOCK prefix
  if (insn->hasLockPrefix) {
    switch(insn->instructionID) {
      default:
        // invalid LOCK
        return true;

      // nop dword [rax]
      case X86_NOOPL:

      // DEC
      case X86_DEC16m:
      case X86_DEC32m:
      case X86_DEC64m:
      case X86_DEC8m:

      // ADC
      case X86_ADC16mi:
      case X86_ADC16mi8:
      case X86_ADC16mr:
      case X86_ADC32mi:
      case X86_ADC32mi8:
      case X86_ADC32mr:
      case X86_ADC64mi32:
      case X86_ADC64mi8:
      case X86_ADC64mr:
      case X86_ADC8mi:
      case X86_ADC8mi8:
      case X86_ADC8mr:
      case X86_ADC8rm:
      case X86_ADC16rm:
      case X86_ADC32rm:
      case X86_ADC64rm:

      // ADD
      case X86_ADD16mi:
      case X86_ADD16mi8:
      case X86_ADD16mr:
      case X86_ADD32mi:
      case X86_ADD32mi8:
      case X86_ADD32mr:
      case X86_ADD64mi32:
      case X86_ADD64mi8:
      case X86_ADD64mr:
      case X86_ADD8mi:
      case X86_ADD8mi8:
      case X86_ADD8mr:
      case X86_ADD8rm:
      case X86_ADD16rm:
      case X86_ADD32rm:
      case X86_ADD64rm:

      // AND
      case X86_AND16mi:
      case X86_AND16mi8:
      case X86_AND16mr:
      case X86_AND32mi:
      case X86_AND32mi8:
      case X86_AND32mr:
      case X86_AND64mi32:
      case X86_AND64mi8:
      case X86_AND64mr:
      case X86_AND8mi:
      case X86_AND8mi8:
      case X86_AND8mr:
      case X86_AND8rm:
      case X86_AND16rm:
      case X86_AND32rm:
      case X86_AND64rm:

      // BTC
      case X86_BTC16mi8:
      case X86_BTC16mr:
      case X86_BTC32mi8:
      case X86_BTC32mr:
      case X86_BTC64mi8:
      case X86_BTC64mr:

      // BTR
      case X86_BTR16mi8:
      case X86_BTR16mr:
      case X86_BTR32mi8:
      case X86_BTR32mr:
      case X86_BTR64mi8:
      case X86_BTR64mr:

      // BTS
      case X86_BTS16mi8:
      case X86_BTS16mr:
      case X86_BTS32mi8:
      case X86_BTS32mr:
      case X86_BTS64mi8:
      case X86_BTS64mr:

      // CMPXCHG
      case X86_CMPXCHG16B:
      case X86_CMPXCHG16rm:
      case X86_CMPXCHG32rm:
      case X86_CMPXCHG64rm:
      case X86_CMPXCHG8rm:
      case X86_CMPXCHG8B:

      // INC
      case X86_INC16m:
      case X86_INC32m:
      case X86_INC64m:
      case X86_INC8m:

      // NEG
      case X86_NEG16m:
      case X86_NEG32m:
      case X86_NEG64m:
      case X86_NEG8m:

      // NOT
      case X86_NOT16m:
      case X86_NOT32m:
      case X86_NOT64m:
      case X86_NOT8m:

      // OR
      case X86_OR16mi:
      case X86_OR16mi8:
      case X86_OR16mr:
      case X86_OR32mi:
      case X86_OR32mi8:
      case X86_OR32mr:
      case X86_OR64mi32:
      case X86_OR64mi8:
      case X86_OR64mr:
      case X86_OR8mi8:
      case X86_OR8mi:
      case X86_OR8mr:
      case X86_OR8rm:
      case X86_OR16rm:
      case X86_OR32rm:
      case X86_OR64rm:

      // SBB
      case X86_SBB16mi:
      case X86_SBB16mi8:
      case X86_SBB16mr:
      case X86_SBB32mi:
      case X86_SBB32mi8:
      case X86_SBB32mr:
      case X86_SBB64mi32:
      case X86_SBB64mi8:
      case X86_SBB64mr:
      case X86_SBB8mi:
      case X86_SBB8mi8:
      case X86_SBB8mr:

      // SUB
      case X86_SUB16mi:
      case X86_SUB16mi8:
      case X86_SUB16mr:
      case X86_SUB32mi:
      case X86_SUB32mi8:
      case X86_SUB32mr:
      case X86_SUB64mi32:
      case X86_SUB64mi8:
      case X86_SUB64mr:
      case X86_SUB8mi8:
      case X86_SUB8mi:
      case X86_SUB8mr:
      case X86_SUB8rm:
      case X86_SUB16rm:
      case X86_SUB32rm:
      case X86_SUB64rm:

      // XADD
      case X86_XADD16rm:
      case X86_XADD32rm:
      case X86_XADD64rm:
      case X86_XADD8rm:

      // XCHG
      case X86_XCHG16rm:
      case X86_XCHG32rm:
      case X86_XCHG64rm:
      case X86_XCHG8rm:

      // XOR
      case X86_XOR16mi:
      case X86_XOR16mi8:
      case X86_XOR16mr:
      case X86_XOR32mi:
      case X86_XOR32mi8:
      case X86_XOR32mr:
      case X86_XOR64mi32:
      case X86_XOR64mi8:
      case X86_XOR64mr:
      case X86_XOR8mi8:
      case X86_XOR8mi:
      case X86_XOR8mr:
      case X86_XOR8rm:
      case X86_XOR16rm:
      case X86_XOR32rm:
      case X86_XOR64rm:

        // this instruction can be used with LOCK prefix
        return false;
    }
  }

#if 0
  // REPNE prefix
  if (insn->repeatPrefix) {
    // 0xf2 can be a part of instruction encoding, but not really a prefix.
    // In such a case, clear it.
    if (insn->twoByteEscape == 0x0f) {
      insn->prefix0 = 0;
    }
  }
#endif

  // no invalid prefixes
  return false;
}

/*
 * decodeInstruction - Reads and interprets a full instruction provided by the
 *   user.
 *
 * @param insn      - A pointer to the instruction to be populated.  Must be
 *                    pre-allocated.
 * @param reader    - The function to be used to read the instruction's bytes.
 * @param readerArg - A generic argument to be passed to the reader to store
 *                    any internal state.
 * @param startLoc  - The address (in the reader's address space) of the first
 *                    byte in the instruction.
 * @param mode      - The mode (real mode, IA-32e, or IA-32e in 64-bit mode) to
 *                    decode the instruction in.
 * @return          - 0 if instruction is valid; nonzero if not.
 */
int decodeInstruction(struct InternalInstruction *insn,
    byteReader_t reader,
    const void *readerArg,
    uint64_t startLoc,
    DisassemblerMode mode)
{
  insn->reader = reader;
  insn->readerArg = readerArg;
  insn->startLocation = startLoc;
  insn->readerCursor = startLoc;
  insn->mode = mode;
  insn->numImmediatesConsumed = 0;

  if (readPrefixes(insn) ||
      readOpcode(insn) ||
      getID(insn) ||
      insn->instructionID == 0 ||
      checkPrefix(insn) ||
      readOperands(insn))
    return -1;

  insn->length = (size_t)(insn->readerCursor - insn->startLocation);

  // instruction length must be <= 15 to be valid
  if (insn->length > 15)
    return -1;

  if (insn->operandSize == 0)
    insn->operandSize = insn->registerSize;

  insn->operands = &x86OperandSets[insn->spec->operands][0];

  return 0;
}

#endif


Coverage Report

Created: 2026-09-28 06:34