/*
* Copyright (c) 2007 The Hewlett-Packard Development Company
* All rights reserved.
*
* Redistribution and use of this software in source and binary forms,
* with or without modification, are permitted provided that the
* following conditions are met:
*
* The software must be used only for Non-Commercial Use which means any
* use which is NOT directed to receiving any direct monetary
* compensation for, or commercial advantage from such use. Illustrative
* examples of non-commercial use are academic research, personal study,
* teaching, education and corporate research & development.
* Illustrative examples of commercial use are distributing products for
* commercial advantage and providing services using the software for
* commercial advantage.
*
* If you wish to use this software or functionality therein that may be
* covered by patents for commercial use, please contact:
* Director of Intellectual Property Licensing
* Office of Strategy and Technology
* Hewlett-Packard Company
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*
* 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
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* the COPYRIGHT HOLDER(s), HEWLETT-PACKARD COMPANY, nor the names of its
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* this software without specific prior written permission. No right of
* sublicense is granted herewith. Derivatives of the software and
* output created using the software may be prepared, but only for
* Non-Commercial Uses. Derivatives of the software may be shared with
* others provided: (i) the others agree to abide by the list of
* conditions herein which includes the Non-Commercial Use restrictions;
* and (ii) such Derivatives of the software include the above copyright
* notice to acknowledge the contribution from this software where
* applicable, this list of conditions and the disclaimer below.
*
* 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.
*
* Authors: Gabe Black
*/
#include "arch/x86/predecoder.hh"
#include "base/misc.hh"
#include "base/trace.hh"
#include "sim/host.hh"
namespace X86ISA
{
void Predecoder::process()
{
//This function drives the predecoder 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
//predecoder ExtMachInst.
assert(!outOfBytes);
assert(!emiIsReady);
//While there's still something to do...
while(!emiIsReady && !outOfBytes)
{
uint8_t nextByte = getNextByte();
switch(state)
{
case PrefixState:
state = doPrefixState(nextByte);
break;
case OpcodeState:
state = doOpcodeState(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 predecoder.\n");
default:
panic("Unrecognized state! %d\n", state);
}
}
}
//Either get a prefix and record it in the ExtMachInst, or send the
//state machine on to get the opcode(s).
Predecoder::State Predecoder::doPrefixState(uint8_t nextByte)
{
uint8_t prefix = Prefixes[nextByte];
State nextState = PrefixState;
if(prefix)
consumeByte();
switch(prefix)
{
//Operand size override prefixes
case OperandSizeOverride:
DPRINTF(Predecoder, "Found operand size override prefix.\n");
emi.legacy.op = true;
break;
case AddressSizeOverride:
DPRINTF(Predecoder, "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(Predecoder, "Found segment override.\n");
emi.legacy.seg = prefix;
break;
case Lock:
DPRINTF(Predecoder, "Found lock prefix.\n");
emi.legacy.lock = true;
break;
case Rep:
DPRINTF(Predecoder, "Found rep prefix.\n");
emi.legacy.rep = true;
break;
case Repne:
DPRINTF(Predecoder, "Found repne prefix.\n");
emi.legacy.repne = true;
break;
case RexPrefix:
DPRINTF(Predecoder, "Found Rex prefix %#x.\n", nextByte);
emi.rex = nextByte;
break;
case 0:
emi.opcode.num = 0;
nextState = OpcodeState;
break;
default:
panic("Unrecognized prefix %#x\n", nextByte);
}
return nextState;
}
//Load all the opcodes (currently up to 2) and then figure out
//what immediate and/or ModRM is needed.
Predecoder::State Predecoder::doOpcodeState(uint8_t nextByte)
{
State nextState = ErrorState;
emi.opcode.num++;
//We can't handle 3+ byte opcodes right now
assert(emi.opcode.num < 3);
consumeByte();
if(emi.opcode.num == 1 && nextByte == 0x0f)
{
nextState = OpcodeState;
DPRINTF(Predecoder, "Found two byte opcode.\n");
emi.opcode.prefixA = nextByte;
}
else if(emi.opcode.num == 2 &&
(nextByte == 0x0f ||
(nextByte & 0xf8) == 0x38))
{
panic("Three byte opcodes aren't yet supported!\n");
nextState = OpcodeState;
DPRINTF(Predecoder, "Found three byte opcode.\n");
emi.opcode.prefixB = nextByte;
}
else
{
DPRINTF(Predecoder, "Found opcode %#x.\n", nextByte);
emi.opcode.op = nextByte;
//Prepare for any immediate/displacement we might need
immediateCollected = 0;
emi.immediate = 0;
displacementCollected = 0;
emi.displacement = 0;
//Figure out the effective operand size. This can be overriden to
//a fixed value at the decoder level.
if(/*FIXME long mode*/1)
{
if(emi.rex && emi.rex.w)
emi.opSize = 3; // 64 bit operand size
else if(emi.legacy.op)
emi.opSize = 1; // 16 bit operand size
else
emi.opSize = 2; // 32 bit operand size
}
else if(/*FIXME default 32*/1)
{
if(emi.legacy.op)
emi.opSize = 1; // 16 bit operand size
else
emi.opSize = 2; // 32 bit operand size
}
else // 16 bit default operand size
{
if(emi.legacy.op)
emi.opSize = 2; // 32 bit operand size
else
emi.opSize = 1; // 16 bit operand size
}
//Figure out how big of an immediate we'll retreive based
//on the opcode.
int immType = ImmediateType[emi.opcode.num - 1][nextByte];
immediateSize = SizeTypeToSize[emi.opSize - 1][immType];
//Determine what to expect next
if (UsesModRM[emi.opcode.num - 1][nextByte]) {
nextState = ModRMState;
} else {
//If there's no modRM byte, set it to 0 so we can detect
//that later.
emi.modRM = 0;
if(immediateSize) {
nextState = ImmediateState;
} else {
emiIsReady = true;
nextState = PrefixState;
}
}
}
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.
Predecoder::State Predecoder::doModRMState(uint8_t nextByte)
{
State nextState = ErrorState;
emi.modRM = nextByte;
DPRINTF(Predecoder, "Found modrm byte %#x.\n", nextByte);
if (0) {//FIXME in 16 bit mode
//figure out 16 bit displacement size
if(nextByte & 0xC7 == 0x06 ||
nextByte & 0xC0 == 0x80)
displacementSize = 2;
else if(nextByte & 0xC0 == 0x40)
displacementSize = 1;
else
displacementSize = 0;
} else {
//figure out 32/64 bit displacement size
if(nextByte & 0xC6 == 0x04 ||
nextByte & 0xC0 == 0x80)
displacementSize = 4;
else if(nextByte & 0xC0 == 0x40)
displacementSize = 1;
else
displacementSize = 0;
}
//If there's an SIB, get that next.
//There is no SIB in 16 bit mode.
if(nextByte & 0x7 == 4 &&
nextByte & 0xC0 != 0xC0) {
// && in 32/64 bit mode)
nextState = SIBState;
} else if(displacementSize) {
nextState = DisplacementState;
} else if(immediateSize) {
nextState = ImmediateState;
} else {
emiIsReady = true;
nextState = PrefixState;
}
//The ModRM byte is consumed no matter what
consumeByte();
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.
Predecoder::State Predecoder::doSIBState(uint8_t nextByte)
{
State nextState = ErrorState;
emi.sib = nextByte;
DPRINTF(Predecoder, "Found SIB byte %#x.\n", nextByte);
consumeByte();
if(displacementSize) {
nextState = DisplacementState;
} else if(immediateSize) {
nextState = ImmediateState;
} else {
emiIsReady = true;
nextState = PrefixState;
}
return nextState;
}
//Gather up the displacement, or at least as much of it
//as we can get.
Predecoder::State Predecoder::doDisplacementState()
{
State nextState = ErrorState;
getImmediate(displacementCollected,
emi.displacement,
displacementSize);
DPRINTF(Predecoder, "Collecting %d byte displacement, got %d bytes.\n",
displacementSize, displacementCollected);
if(displacementSize == displacementCollected) {
//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(Predecoder, "Collected displacement %#x.\n",
emi.displacement);
if(immediateSize) {
nextState = ImmediateState;
} else {
emiIsReady = true;
nextState = PrefixState;
}
}
else
nextState = DisplacementState;
return nextState;
}
//Gather up the immediate, or at least as much of it
//as we can get
Predecoder::State Predecoder::doImmediateState()
{
State nextState = ErrorState;
getImmediate(immediateCollected,
emi.immediate,
immediateSize);
DPRINTF(Predecoder, "Collecting %d byte immediate, got %d bytes.\n",
immediateSize, immediateCollected);
if(immediateSize == immediateCollected)
{
//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.
if(immediateSize == 4)
emi.immediate = sext<32>(emi.immediate);
DPRINTF(Predecoder, "Collected immediate %#x.\n",
emi.immediate);
emiIsReady = true;
nextState = PrefixState;
}
else
nextState = ImmediateState;
return nextState;
}
}