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Adds a presently-unreachable step for SIB consumption.

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Thomas Harte 2022-02-19 18:00:27 -05:00
parent 30b355fd6f
commit 4d2e8cd71d
3 changed files with 14 additions and 1 deletions
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8
InstructionSets/x86/Decoder.cpp
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@ -637,6 +637,14 @@ std::pair<int, InstructionSet::x86::Instruction> Decoder::decode(const uint8_t *
phase_ = (displacement_size_ + operand_size_) ? Phase::DisplacementOrOperand : Phase::ReadyToPost; phase_ = (displacement_size_ + operand_size_) ? Phase::DisplacementOrOperand : Phase::ReadyToPost;
} }
// MARK: - ScaleIndexBase
if(phase_ == Phase::ScaleIndexBase && source != end) {
sib_ = *source;
++source;
++consumed_;
}
// MARK: - Displacement and operand. // MARK: - Displacement and operand.
if(phase_ == Phase::DisplacementOrOperand && source != end) { if(phase_ == Phase::DisplacementOrOperand && source != end) {

5
InstructionSets/x86/Decoder.hpp
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@ -53,6 +53,8 @@ class Decoder {
/// Receives a ModRegRM byte and either populates the source_ and dest_ fields appropriately /// Receives a ModRegRM byte and either populates the source_ and dest_ fields appropriately
/// or completes decoding of the instruction, as per the instruction format. /// or completes decoding of the instruction, as per the instruction format.
ModRegRM, ModRegRM,
/// Awaits n 80386+-style scale-index-base byte ('SIB'), indicating the form of indirect addressing.
ScaleIndexBase,
/// Waits for sufficiently many bytes to pass for the required displacement and operand to be captured. /// Waits for sufficiently many bytes to pass for the required displacement and operand to be captured.
/// Cf. displacement_size_ and operand_size_. /// Cf. displacement_size_ and operand_size_.
DisplacementOrOperand, DisplacementOrOperand,
@ -143,6 +145,9 @@ class Decoder {
uint16_t operand_ = 0; uint16_t operand_ = 0;
uint64_t inward_data_ = 0; uint64_t inward_data_ = 0;
// Indirection style.
uint8_t sib_;
// Facts about the instruction. // Facts about the instruction.
int displacement_size_ = 0; // i.e. size of in-stream displacement, if any. int displacement_size_ = 0; // i.e. size of in-stream displacement, if any.
int operand_size_ = 0; // i.e. size of in-stream operand, if any. int operand_size_ = 0; // i.e. size of in-stream operand, if any.

2
InstructionSets/x86/Instruction.hpp
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@ -319,7 +319,7 @@ enum class Size: uint8_t {
enum class Source: uint8_t { enum class Source: uint8_t {
// These are in SIB order; this matters for packing later on. // These are in SIB order; this matters for packing later on.
// Whether each refers to e.g. EAX or AX depends on the // Whether each refers to e.g. EAX, AX or AL depends on the
// instruction's data size. // instruction's data size.
eAX, eCX, eDX, eBX, eSP, eBP, eSI, eDI, eAX, eCX, eDX, eBX, eSP, eBP, eSI, eDI,