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/*
* Copyright (c) 2011 Google
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met: redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer;
* redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution;
* neither the name of the copyright holders nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "arch/x86/decoder.hh"
#include "arch/x86/regs/misc.hh"
#include "base/logging.hh"
#include "base/trace.hh"
#include "base/types.hh"
#include "debug/Decode.hh"
#include "debug/Decoder.hh"
namespace gem5
{
namespace X86ISA
{
X86ISAInst::MicrocodeRom Decoder::microcodeRom;
Decoder::State
Decoder::doResetState()
{
origPC = basePC + offset;
DPRINTF(Decoder, "Setting origPC to %#x\n", origPC);
instBytes = &decodePages->lookup(origPC);
chunkIdx = 0;
emi.rex = 0;
emi.legacy = 0;
emi.vex = 0;
emi.opcode.type = BadOpcode;
emi.opcode.op = 0;
immediateCollected = 0;
emi.immediate = 0;
emi.displacement = 0;
emi.dispSize = 0;
emi.modRM = 0;
emi.sib = 0;
if (instBytes->si) {
return FromCacheState;
} else {
instBytes->chunks.clear();
return PrefixState;
}
}
void
Decoder::process()
{
// This function drives the decoder state machine.
// Some sanity checks. You shouldn't try to process more bytes if
// there aren't any, and you shouldn't overwrite an already decoded
// ExtMachInst.
assert(!outOfBytes);
assert(!instDone);
if (state == ResetState)
state = doResetState();
if (state == FromCacheState) {
state = doFromCacheState();
} else {
instBytes->chunks.push_back(fetchChunk);
}
// While there's still something to do...
while (!instDone && !outOfBytes) {
uint8_t nextByte = getNextByte();
switch (state) {
case PrefixState:
state = doPrefixState(nextByte);
break;
case Vex2Of2State:
state = doVex2Of2State(nextByte);
break;
case Vex2Of3State:
state = doVex2Of3State(nextByte);
break;
case Vex3Of3State:
state = doVex3Of3State(nextByte);
break;
case VexOpcodeState:
state = doVexOpcodeState(nextByte);
break;
case OneByteOpcodeState:
state = doOneByteOpcodeState(nextByte);
break;
case TwoByteOpcodeState:
state = doTwoByteOpcodeState(nextByte);
break;
case ThreeByte0F38OpcodeState:
state = doThreeByte0F38OpcodeState(nextByte);
break;
case ThreeByte0F3AOpcodeState:
state = doThreeByte0F3AOpcodeState(nextByte);
break;
case ModRMState:
state = doModRMState(nextByte);
break;
case SIBState:
state = doSIBState(nextByte);
break;
case DisplacementState:
state = doDisplacementState();
break;
case ImmediateState:
state = doImmediateState();
break;
case ErrorState:
panic("Went to the error state in the decoder.\n");
default:
panic("Unrecognized state! %d\n", state);
}
}
}
Decoder::State
Decoder::doFromCacheState()
{
DPRINTF(Decoder, "Looking at cache state.\n");
if ((fetchChunk & instBytes->masks[chunkIdx]) !=
instBytes->chunks[chunkIdx]) {
DPRINTF(Decoder, "Decode cache miss.\n");
// The chached chunks didn't match what was fetched. Fall back to the
// predecoder.
instBytes->chunks[chunkIdx] = fetchChunk;
instBytes->chunks.resize(chunkIdx + 1);
instBytes->si = NULL;
chunkIdx = 0;
fetchChunk = instBytes->chunks[0];
offset = origPC % sizeof(MachInst);
basePC = origPC - offset;
return PrefixState;
} else if (chunkIdx == instBytes->chunks.size() - 1) {
// We matched the cache, so use its value.
instDone = true;
offset = instBytes->lastOffset;
if (offset == sizeof(MachInst))
outOfBytes = true;
return ResetState;
} else {
// We matched so far, but need to check more chunks.
chunkIdx++;
outOfBytes = true;
return FromCacheState;
}
}
// Either get a prefix and record it in the ExtMachInst, or send the
// state machine on to get the opcode(s).
Decoder::State
Decoder::doPrefixState(uint8_t nextByte)
{
// The REX and VEX prefixes only exist in 64 bit mode, so we use a
// different table for that.
const int table_idx = emi.mode.submode == SixtyFourBitMode ? 1 : 0;
const uint8_t prefix = Prefixes[table_idx][nextByte];
State nextState = PrefixState;
if (prefix)
consumeByte();
switch(prefix) {
// Operand size override prefixes
case OperandSizeOverride:
DPRINTF(Decoder, "Found operand size override prefix.\n");
emi.legacy.op = true;
break;
case AddressSizeOverride:
DPRINTF(Decoder, "Found address size override prefix.\n");
emi.legacy.addr = true;
break;
// Segment override prefixes
case CSOverride:
case DSOverride:
case ESOverride:
case FSOverride:
case GSOverride:
case SSOverride:
DPRINTF(Decoder, "Found segment override.\n");
emi.legacy.seg = prefix;
break;
case Lock:
DPRINTF(Decoder, "Found lock prefix.\n");
emi.legacy.lock = true;
break;
case Rep:
DPRINTF(Decoder, "Found rep prefix.\n");
emi.legacy.rep = true;
break;
case Repne:
DPRINTF(Decoder, "Found repne prefix.\n");
emi.legacy.repne = true;
break;
case RexPrefix:
DPRINTF(Decoder, "Found Rex prefix %#x.\n", nextByte);
emi.rex = nextByte;
break;
case Vex2Prefix:
DPRINTF(Decoder, "Found VEX two-byte prefix %#x.\n", nextByte);
emi.vex.present = 1;
nextState = Vex2Of2State;
break;
case Vex3Prefix:
DPRINTF(Decoder, "Found VEX three-byte prefix %#x.\n", nextByte);
emi.vex.present = 1;
nextState = Vex2Of3State;
break;
case 0:
nextState = OneByteOpcodeState;
break;
default:
panic("Unrecognized prefix %#x\n", nextByte);
}
return nextState;
}
Decoder::State
Decoder::doVex2Of2State(uint8_t nextByte)
{
consumeByte();
Vex2Of2 vex = nextByte;
emi.rex.r = !vex.r;
emi.vex.l = vex.l;
emi.vex.v = ~vex.v;
switch (vex.p) {
case 0:
break;
case 1:
emi.legacy.op = 1;
break;
case 2:
emi.legacy.rep = 1;
break;
case 3:
emi.legacy.repne = 1;
break;
}
emi.opcode.type = TwoByteOpcode;
return VexOpcodeState;
}
Decoder::State
Decoder::doVex2Of3State(uint8_t nextByte)
{
if (emi.mode.submode != SixtyFourBitMode && bits(nextByte, 7, 6) == 0x3) {
// This was actually an LDS instruction. Reroute to that path.
emi.vex.present = 0;
emi.opcode.type = OneByteOpcode;
emi.opcode.op = 0xC4;
return processOpcode(ImmediateTypeOneByte, UsesModRMOneByte,
nextByte >= 0xA0 && nextByte <= 0xA3);
}
consumeByte();
Vex2Of3 vex = nextByte;
emi.rex.r = !vex.r;
emi.rex.x = !vex.x;
emi.rex.b = !vex.b;
switch (vex.m) {
case 1:
emi.opcode.type = TwoByteOpcode;
break;
case 2:
emi.opcode.type = ThreeByte0F38Opcode;
break;
case 3:
emi.opcode.type = ThreeByte0F3AOpcode;
break;
default:
// These encodings are reserved. Pretend this was an undefined
// instruction so the main decoder will behave correctly, and stop
// trying to interpret bytes.
emi.opcode.type = TwoByteOpcode;
emi.opcode.op = 0x0B;
instDone = true;
return ResetState;
}
return Vex3Of3State;
}
Decoder::State
Decoder::doVex3Of3State(uint8_t nextByte)
{
if (emi.mode.submode != SixtyFourBitMode && bits(nextByte, 7, 6) == 0x3) {
// This was actually an LES instruction. Reroute to that path.
emi.vex.present = 0;
emi.opcode.type = OneByteOpcode;
emi.opcode.op = 0xC5;
return processOpcode(ImmediateTypeOneByte, UsesModRMOneByte,
nextByte >= 0xA0 && nextByte <= 0xA3);
}
consumeByte();
Vex3Of3 vex = nextByte;
emi.rex.w = vex.w;
emi.vex.l = vex.l;
emi.vex.v = ~vex.v;
switch (vex.p) {
case 0:
break;
case 1:
emi.legacy.op = 1;
break;
case 2:
emi.legacy.rep = 1;
break;
case 3:
emi.legacy.repne = 1;
break;
}
return VexOpcodeState;
}
Decoder::State
Decoder::doVexOpcodeState(uint8_t nextByte)
{
DPRINTF(Decoder, "Found VEX opcode %#x.\n", nextByte);
emi.opcode.op = nextByte;
consumeByte();
switch (emi.opcode.type) {
case TwoByteOpcode:
return processOpcode(ImmediateTypeTwoByte, UsesModRMTwoByte);
case ThreeByte0F38Opcode:
return processOpcode(ImmediateTypeThreeByte0F38,
UsesModRMThreeByte0F38);
case ThreeByte0F3AOpcode:
return processOpcode(ImmediateTypeThreeByte0F3A,
UsesModRMThreeByte0F3A);
default:
panic("Unrecognized opcode type %d.\n", emi.opcode.type);
}
}
// Load the first opcode byte. Determine if there are more opcode bytes, and
// if not, what immediate and/or ModRM is needed.
Decoder::State
Decoder::doOneByteOpcodeState(uint8_t nextByte)
{
State nextState = ErrorState;
consumeByte();
if (nextByte == 0x0f) {
DPRINTF(Decoder, "Found opcode escape byte %#x.\n", nextByte);
nextState = TwoByteOpcodeState;
} else {
DPRINTF(Decoder, "Found one byte opcode %#x.\n", nextByte);
emi.opcode.type = OneByteOpcode;
emi.opcode.op = nextByte;
nextState = processOpcode(ImmediateTypeOneByte, UsesModRMOneByte,
nextByte >= 0xA0 && nextByte <= 0xA3);
}
return nextState;
}
// Load the second opcode byte. Determine if there are more opcode bytes, and
// if not, what immediate and/or ModRM is needed.
Decoder::State
Decoder::doTwoByteOpcodeState(uint8_t nextByte)
{
State nextState = ErrorState;
consumeByte();
if (nextByte == 0x38) {
nextState = ThreeByte0F38OpcodeState;
DPRINTF(Decoder, "Found opcode escape byte %#x.\n", nextByte);
} else if (nextByte == 0x3a) {
nextState = ThreeByte0F3AOpcodeState;
DPRINTF(Decoder, "Found opcode escape byte %#x.\n", nextByte);
} else {
DPRINTF(Decoder, "Found two byte opcode %#x.\n", nextByte);
emi.opcode.type = TwoByteOpcode;
emi.opcode.op = nextByte;
nextState = processOpcode(ImmediateTypeTwoByte, UsesModRMTwoByte);
}
return nextState;
}
// Load the third opcode byte and determine what immediate and/or ModRM is
// needed.
Decoder::State
Decoder::doThreeByte0F38OpcodeState(uint8_t nextByte)
{
consumeByte();
DPRINTF(Decoder, "Found three byte 0F38 opcode %#x.\n", nextByte);
emi.opcode.type = ThreeByte0F38Opcode;
emi.opcode.op = nextByte;
return processOpcode(ImmediateTypeThreeByte0F38, UsesModRMThreeByte0F38);
}
// Load the third opcode byte and determine what immediate and/or ModRM is
// needed.
Decoder::State
Decoder::doThreeByte0F3AOpcodeState(uint8_t nextByte)
{
consumeByte();
DPRINTF(Decoder, "Found three byte 0F3A opcode %#x.\n", nextByte);
emi.opcode.type = ThreeByte0F3AOpcode;
emi.opcode.op = nextByte;
return processOpcode(ImmediateTypeThreeByte0F3A, UsesModRMThreeByte0F3A);
}
// Generic opcode processing which determines the immediate size, and whether
// or not there's a modrm byte.
Decoder::State
Decoder::processOpcode(ByteTable &immTable, ByteTable &modrmTable,
bool addrSizedImm)
{
State nextState = ErrorState;
const uint8_t opcode = emi.opcode.op;
// Figure out the effective operand size. This can be overriden to
// a fixed value at the decoder level.
int logOpSize;
if (emi.rex.w)
logOpSize = 3; // 64 bit operand size
else if (emi.legacy.op)
logOpSize = altOp;
else
logOpSize = defOp;
// Set the actual op size.
emi.opSize = 1 << logOpSize;
// Figure out the effective address size. This can be overriden to
// a fixed value at the decoder level.
int logAddrSize;
if (emi.legacy.addr)
logAddrSize = altAddr;
else
logAddrSize = defAddr;
// Set the actual address size.
emi.addrSize = 1 << logAddrSize;
// Figure out the effective stack width. This can be overriden to
// a fixed value at the decoder level.
emi.stackSize = 1 << stack;
// Figure out how big of an immediate we'll retreive based
// on the opcode.
int immType = immTable[opcode];
if (addrSizedImm)
immediateSize = SizeTypeToSize[logAddrSize - 1][immType];
else
immediateSize = SizeTypeToSize[logOpSize - 1][immType];
// Determine what to expect next.
if (modrmTable[opcode]) {
nextState = ModRMState;
} else {
if (immediateSize) {
nextState = ImmediateState;
} else {
instDone = true;
nextState = ResetState;
}
}
return nextState;
}
// Get the ModRM byte and determine what displacement, if any, there is.
// Also determine whether or not to get the SIB byte, displacement, or
// immediate next.
Decoder::State
Decoder::doModRMState(uint8_t nextByte)
{
State nextState = ErrorState;
ModRM modRM = nextByte;
DPRINTF(Decoder, "Found modrm byte %#x.\n", nextByte);
if (emi.addrSize == 2) {
// Figure out 16 bit displacement size.
if ((modRM.mod == 0 && modRM.rm == 6) || modRM.mod == 2)
displacementSize = 2;
else if (modRM.mod == 1)
displacementSize = 1;
else
displacementSize = 0;
} else {
// Figure out 32/64 bit displacement size.
if ((modRM.mod == 0 && modRM.rm == 5) || modRM.mod == 2)
displacementSize = 4;
else if (modRM.mod == 1)
displacementSize = 1;
else
displacementSize = 0;
}
// The "test" instruction in group 3 needs an immediate, even though
// the other instructions with the same actual opcode don't.
if (emi.opcode.type == OneByteOpcode && (modRM.reg & 0x6) == 0) {
if (emi.opcode.op == 0xF6)
immediateSize = 1;
else if (emi.opcode.op == 0xF7)
immediateSize = (emi.opSize == 8) ? 4 : emi.opSize;
}
// If there's an SIB, get that next.
// There is no SIB in 16 bit mode.
if (modRM.rm == 4 && modRM.mod != 3 && emi.addrSize != 2) {
nextState = SIBState;
} else if (displacementSize) {
nextState = DisplacementState;
} else if (immediateSize) {
nextState = ImmediateState;
} else {
instDone = true;
nextState = ResetState;
}
// The ModRM byte is consumed no matter what.
consumeByte();
emi.modRM = modRM;
return nextState;
}
// Get the SIB byte. We don't do anything with it at this point, other
// than storing it in the ExtMachInst. Determine if we need to get a
// displacement or immediate next.
Decoder::State
Decoder::doSIBState(uint8_t nextByte)
{
State nextState = ErrorState;
emi.sib = nextByte;
DPRINTF(Decoder, "Found SIB byte %#x.\n", nextByte);
consumeByte();
if (emi.modRM.mod == 0 && emi.sib.base == 5)
displacementSize = 4;
if (displacementSize) {
nextState = DisplacementState;
} else if (immediateSize) {
nextState = ImmediateState;
} else {
instDone = true;
nextState = ResetState;
}
return nextState;
}
// Gather up the displacement, or at least as much of it as we can get.
Decoder::State
Decoder::doDisplacementState()
{
State nextState = ErrorState;
getImmediate(immediateCollected,
emi.displacement,
displacementSize);
DPRINTF(Decoder, "Collecting %d byte displacement, got %d bytes.\n",
displacementSize, immediateCollected);
if (displacementSize == immediateCollected) {
// Reset this for other immediates.
immediateCollected = 0;
// Sign extend the displacement.
switch(displacementSize)
{
case 1:
emi.displacement = sext<8>(emi.displacement);
break;
case 2:
emi.displacement = sext<16>(emi.displacement);
break;
case 4:
emi.displacement = sext<32>(emi.displacement);
break;
default:
panic("Undefined displacement size!\n");
}
DPRINTF(Decoder, "Collected displacement %#x.\n",
emi.displacement);
if (immediateSize) {
nextState = ImmediateState;
} else {
instDone = true;
nextState = ResetState;
}
emi.dispSize = displacementSize;
}
else
nextState = DisplacementState;
return nextState;
}
// Gather up the immediate, or at least as much of it as we can get.
Decoder::State
Decoder::doImmediateState()
{
State nextState = ErrorState;
getImmediate(immediateCollected, emi.immediate, immediateSize);
DPRINTF(Decoder, "Collecting %d byte immediate, got %d bytes.\n",
immediateSize, immediateCollected);
if (immediateSize == immediateCollected) {
// Reset this for other immediates.
immediateCollected = 0;
//XXX Warning! The following is an observed pattern and might
// not always be true!
// Instructions which use 64 bit operands but 32 bit immediates
// need to have the immediate sign extended to 64 bits.
// Instructions which use true 64 bit immediates won't be
// affected, and instructions that use true 32 bit immediates
// won't notice.
switch(immediateSize) {
case 4:
emi.immediate = sext<32>(emi.immediate);
break;
case 1:
emi.immediate = sext<8>(emi.immediate);
}
DPRINTF(Decoder, "Collected immediate %#x.\n",
emi.immediate);
instDone = true;
nextState = ResetState;
} else {
nextState = ImmediateState;
}
return nextState;
}
Decoder::InstBytes Decoder::dummy;
Decoder::InstCacheMap Decoder::instCacheMap;
StaticInstPtr
Decoder::decode(ExtMachInst mach_inst, Addr addr)
{
StaticInstPtr si;
auto iter = instMap->find(mach_inst);
if (iter != instMap->end()) {
si = iter->second;
} else {
si = decodeInst(mach_inst);
(*instMap)[mach_inst] = si;
}
DPRINTF(Decode, "Decode: Decoded %s instruction: %#x\n",
si->getName(), mach_inst);
return si;
}
StaticInstPtr
Decoder::decode(PCStateBase &next_pc)
{
if (!instDone)
return NULL;
instDone = false;
updateNPC(next_pc.as<PCState>());
StaticInstPtr &si = instBytes->si;
if (si)
return si;
// We didn't match in the AddrMap, but we still populated an entry. Fix
// up its byte masks.
const int chunkSize = sizeof(MachInst);
instBytes->lastOffset = offset;
Addr firstBasePC = basePC - (instBytes->chunks.size() - 1) * chunkSize;
Addr firstOffset = origPC - firstBasePC;
Addr totalSize = instBytes->lastOffset - firstOffset +
(instBytes->chunks.size() - 1) * chunkSize;
int start = firstOffset;
instBytes->masks.clear();
while (totalSize) {
int end = start + totalSize;
end = (chunkSize < end) ? chunkSize : end;
int size = end - start;
int idx = instBytes->masks.size();
MachInst maskVal = mask(size * 8) << (start * 8);
assert(maskVal);
instBytes->masks.push_back(maskVal);
instBytes->chunks[idx] &= instBytes->masks[idx];
totalSize -= size;
start = 0;
}
si = decode(emi, origPC);
return si;
}
StaticInstPtr
Decoder::fetchRomMicroop(MicroPC micropc, StaticInstPtr curMacroop)
{
return microcodeRom.fetchMicroop(micropc, curMacroop);
}
} // namespace X86ISA
} // namespace gem5