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Introduces the easy F page instructions.

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This commit is contained in:
Thomas Harte 2022-02-10 09:35:05 -05:00
parent 7ceb3369eb
commit 0bd63cf00f
2 changed files with 42 additions and 7 deletions
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45
InstructionSets/x86/Decoder.cpp
View File

@ -81,6 +81,12 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
displacement_size_ = 2; \
operand_size_ = 1; \
#define undefined() { \
const auto result = std::make_pair(consumed_, Instruction()); \
reset_parsing(); \
return result; \
}
while(phase_ == Phase::Instruction && source != end) {
// Retain the instruction byte, in case additional decoding is deferred
// to the ModRegRM byte.
@ -88,12 +94,6 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
++source;
++consumed_;
#define undefined() { \
const auto result = std::make_pair(consumed_, Instruction()); \
reset_parsing(); \
return result; \
}
switch(instr_) {
default: undefined();
@ -112,6 +112,13 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
PartialBlock(0x08, OR); break;
case 0x0e: Complete(PUSH, CS, None, 2); break;
// The 286 onwards have a further set of instructions
// prefixed with $0f.
case 0x0f:
if(model_ < Model::i80286) undefined();
phase_ = Phase::InstructionPageF;
break;
PartialBlock(0x10, ADC); break;
case 0x16: Complete(PUSH, SS, None, 2); break;
case 0x17: Complete(POP, None, SS, 2); break;
@ -167,6 +174,10 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
if(model_ < Model::i80186) undefined();
MemRegReg(BOUND, Reg_MemReg, 2);
break;
case 0x63:
if(model_ < Model::i80286) undefined();
MemRegReg(ARPL, MemReg_Reg, 2);
break;
case 0x6c: // INSB
if(model_ < Model::i80186) undefined();
Complete(INS, None, None, 1);
@ -365,6 +376,28 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
}
}
// MARK: - Additional F page of instructions.
if(phase_ == Phase::InstructionPageF && source != end) {
// Update the instruction acquired.
instr_ = 0x0f00 | *source;
++source;
++consumed_;
// NB: to reach here, the instruction set must be at least
// that of an 80286.
switch(instr_) {
default: undefined();
case 0x02: MemRegReg(LAR, Reg_MemReg, 2); break;
case 0x03: MemRegReg(LSL, Reg_MemReg, 2); break;
case 0x06: Complete(CLTS, None, None, 1); break;
}
// TODO: 0x0f 0x00 -> LLDT/SLDT/VERR/VERW/LTR/STR
// TODO: 0x0f 0x01 -> LGDT/LIDT/SGDT/SIDT/LMSW/SMSW
// TODO: 0x0f 0x05 -> LOADALL
}
#undef Far
#undef Jump
#undef MemRegReg

4
InstructionSets/x86/Decoder.hpp
View File

@ -48,6 +48,8 @@ class Decoder {
enum class Phase {
/// Captures all prefixes and continues until an instruction byte is encountered.
Instruction,
/// Having encountered a 0x0f first instruction byte, waits for the next byte fully to determine the instruction.
InstructionPageF,
/// Receives a ModRegRM byte and either populates the source_ and dest_ fields appropriately
/// or completes decoding of the instruction, as per the instruction format.
ModRegRM,
@ -119,7 +121,7 @@ class Decoder {
// Ephemeral decoding state.
Operation operation_ = Operation::Invalid;
uint8_t instr_ = 0x00; // TODO: is this desired, versus loading more context into ModRegRMFormat?
uint16_t instr_ = 0x0000; // TODO: is this desired, versus loading more context into ModRegRMFormat?
int consumed_ = 0, operand_bytes_ = 0;
// Source and destination locations.