/*
* 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;
BOOL prefixGroups[4] = { FALSE };
uint64_t prefixLocation;
uint8_t byte = 0;
BOOL hasAdSize = FALSE;
BOOL hasOpSize = FALSE;
dbgprintf(insn, "readPrefixes()");
while (isPrefix) {
prefixLocation = insn->readerCursor;
if (consumeByte(insn, &byte))
return -1;
switch (byte) {
case 0xf0: /* LOCK */
case 0xf2: /* REPNE/REPNZ */
case 0xf3: /* REP or REPE/REPZ */
if (prefixGroups[0])
dbgprintf(insn, "Redundant Group 1 prefix");
prefixGroups[0] = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
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;
break;
case 0x36:
insn->segmentOverride = SEG_OVERRIDE_SS;
break;
case 0x3e:
insn->segmentOverride = SEG_OVERRIDE_DS;
break;
case 0x26:
insn->segmentOverride = SEG_OVERRIDE_ES;
break;
case 0x64:
insn->segmentOverride = SEG_OVERRIDE_FS;
break;
case 0x65:
insn->segmentOverride = SEG_OVERRIDE_GS;
break;
default:
debug("Unhandled override");
return -1;
}
if (prefixGroups[1])
dbgprintf(insn, "Redundant Group 2 prefix");
prefixGroups[1] = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
case 0x66: /* Operand-size override */
if (prefixGroups[2])
dbgprintf(insn, "Redundant Group 3 prefix");
prefixGroups[2] = TRUE;
hasOpSize = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
case 0x67: /* Address-size override */
if (prefixGroups[3])
dbgprintf(insn, "Redundant Group 4 prefix");
prefixGroups[3] = TRUE;
hasAdSize = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
default: /* Not a prefix byte */
isPrefix = FALSE;
break;
}
if (isPrefix)
dbgprintf(insn, "Found prefix 0x%hhx", byte);
}
insn->vexSize = 0;
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->vexSize = 3;
insn->necessaryPrefixLocation = insn->readerCursor - 1;
}
else {
unconsumeByte(insn);
insn->necessaryPrefixLocation = insn->readerCursor - 1;
}
if (insn->vexSize == 3) {
insn->vexPrefix[0] = byte;
consumeByte(insn, &insn->vexPrefix[1]);
consumeByte(insn, &insn->vexPrefix[2]);
/* We simulate the REX prefix for simplicity's sake */
if (insn->mode == MODE_64BIT) {
insn->rexPrefix = 0x40
| (wFromVEX3of3(insn->vexPrefix[2]) << 3)
| (rFromVEX2of3(insn->vexPrefix[1]) << 2)
| (xFromVEX2of3(insn->vexPrefix[1]) << 1)
| (bFromVEX2of3(insn->vexPrefix[1]) << 0);
}
switch (ppFromVEX3of3(insn->vexPrefix[2]))
{
default:
break;
case VEX_PREFIX_66:
hasOpSize = TRUE;
break;
}
dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx 0x%hhx", insn->vexPrefix[0], insn->vexPrefix[1], insn->vexPrefix[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->vexSize = 2;
}
else {
unconsumeByte(insn);
}
if (insn->vexSize == 2) {
insn->vexPrefix[0] = byte;
consumeByte(insn, &insn->vexPrefix[1]);
if (insn->mode == MODE_64BIT) {
insn->rexPrefix = 0x40
| (rFromVEX2of2(insn->vexPrefix[1]) << 2);
}
switch (ppFromVEX2of2(insn->vexPrefix[1]))
{
default:
break;
case VEX_PREFIX_66:
hasOpSize = TRUE;
break;
}
dbgprintf(insn, "Found VEX prefix 0x%hhx 0x%hhx", insn->vexPrefix[0], insn->vexPrefix[1]);
}
}
else {
if (insn->mode == MODE_64BIT) {
if ((byte & 0xf0) == 0x40) {
uint8_t opcodeByte;
if (lookAtByte(insn, &opcodeByte) || ((opcodeByte & 0xf0) == 0x40)) {
dbgprintf(insn, "Redundant REX prefix");
return -1;
}
insn->rexPrefix = byte;
insn->necessaryPrefixLocation = insn->readerCursor - 2;
dbgprintf(insn, "Found REX prefix 0x%hhx", byte);
} else {
unconsumeByte(insn);
insn->necessaryPrefixLocation = insn->readerCursor - 1;
}
} else {
unconsumeByte(insn);
insn->necessaryPrefixLocation = insn->readerCursor - 1;
}
}
if (insn->mode == MODE_16BIT) {
insn->registerSize = (hasOpSize ? 4 : 2);
insn->addressSize = (hasAdSize ? 4 : 2);
insn->displacementSize = (hasAdSize ? 4 : 2);
insn->immediateSize = (hasOpSize ? 4 : 2);
} else if (insn->mode == MODE_32BIT) {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 2 : 4);
insn->displacementSize = (hasAdSize ? 2 : 4);
insn->immediateSize = (hasOpSize ? 2 : 4);
} else if (insn->mode == MODE_64BIT) {
if (insn->rexPrefix && wFromREX(insn->rexPrefix)) {
insn->registerSize = 8;
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = 4;
insn->immediateSize = 4;
} else if (insn->rexPrefix) {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = (hasOpSize ? 2 : 4);
insn->immediateSize = (hasOpSize ? 2 : 4);
} else {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = (hasOpSize ? 2 : 4);
insn->immediateSize = (hasOpSize ? 2 : 4);
}
}
return 0;
}
/*
* 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;
BOOL prefixGroups[4] = { FALSE };
uint64_t prefixLocation;
uint8_t byte;
BOOL hasAdSize = FALSE;
BOOL hasOpSize = FALSE;
dbgprintf(insn, "readPrefixes()");
while (isPrefix) {
prefixLocation = insn->readerCursor;
if (consumeByte(insn, &byte))
return -1;
switch (byte) {
case 0xf0: /* LOCK */
case 0xf2: /* REPNE/REPNZ */
case 0xf3: /* REP or REPE/REPZ */
if (prefixGroups[0])
dbgprintf(insn, "Redundant Group 1 prefix");
prefixGroups[0] = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
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;
break;
case 0x36:
insn->segmentOverride = SEG_OVERRIDE_SS;
break;
case 0x3e:
insn->segmentOverride = SEG_OVERRIDE_DS;
break;
case 0x26:
insn->segmentOverride = SEG_OVERRIDE_ES;
break;
case 0x64:
insn->segmentOverride = SEG_OVERRIDE_FS;
break;
case 0x65:
insn->segmentOverride = SEG_OVERRIDE_GS;
break;
default:
unreachable("Unhandled override");
}
if (prefixGroups[1])
dbgprintf(insn, "Redundant Group 2 prefix");
prefixGroups[1] = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
case 0x66: /* Operand-size override */
if (prefixGroups[2])
dbgprintf(insn, "Redundant Group 3 prefix");
prefixGroups[2] = TRUE;
hasOpSize = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
case 0x67: /* Address-size override */
if (prefixGroups[3])
dbgprintf(insn, "Redundant Group 4 prefix");
prefixGroups[3] = TRUE;
hasAdSize = TRUE;
setPrefixPresent(insn, byte, prefixLocation);
break;
default: /* Not a prefix byte */
isPrefix = FALSE;
break;
}
if (isPrefix)
dbgprintf(insn, "Found prefix 0x%hhx", byte);
}
if (insn->mode == MODE_64BIT) {
if ((byte & 0xf0) == 0x40) {
uint8_t opcodeByte;
if(lookAtByte(insn, &opcodeByte) || ((opcodeByte & 0xf0) == 0x40)) {
dbgprintf(insn, "Redundant REX prefix");
return -1;
}
insn->rexPrefix = byte;
insn->necessaryPrefixLocation = insn->readerCursor - 2;
dbgprintf(insn, "Found REX prefix 0x%hhx", byte);
} else {
unconsumeByte(insn);
insn->necessaryPrefixLocation = insn->readerCursor - 1;
}
} else {
unconsumeByte(insn);
}
if (insn->mode == MODE_16BIT) {
insn->registerSize = (hasOpSize ? 4 : 2);
insn->addressSize = (hasAdSize ? 4 : 2);
insn->displacementSize = (hasAdSize ? 4 : 2);
insn->immediateSize = (hasOpSize ? 4 : 2);
} else if (insn->mode == MODE_32BIT) {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 2 : 4);
insn->displacementSize = (hasAdSize ? 2 : 4);
insn->immediateSize = (hasAdSize ? 2 : 4);
} else if (insn->mode == MODE_64BIT) {
if (insn->rexPrefix && wFromREX(insn->rexPrefix)) {
insn->registerSize = 8;
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = 4;
insn->immediateSize = 4;
} else if (insn->rexPrefix) {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = (hasOpSize ? 2 : 4);
insn->immediateSize = (hasOpSize ? 2 : 4);
} else {
insn->registerSize = (hasOpSize ? 2 : 4);
insn->addressSize = (hasAdSize ? 4 : 8);
insn->displacementSize = (hasOpSize ? 2 : 4);
insn->immediateSize = (hasOpSize ? 2 : 4);
}
}
return 0;
}
