feat(code): add instruction rewriter implementation
This commit is contained in:
boykopovar
parent
88fca26a28
commit
2ac8a96d70
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@ -11,6 +11,7 @@ add_executable(relinker
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${CMAKE_CURRENT_SOURCE_DIR}/io/src/FileWriter.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/InstructionScanner.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/x86/X64InstructionDecoder.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/codegen/src/x86/X64InstructionRewriter.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/src/parsing/ElfReader.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/src/analysis/SyscallScanner.cpp
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${CMAKE_CURRENT_SOURCE_DIR}/relinker/src/analysis/CallSiteResolver.cpp
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@ -2,6 +2,7 @@
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#define CODEGEN_X86_X64INSTRUCTIONREWRITER_HPP
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#include <codegen/IInstructionRewriter.hpp>
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#include <cstdint>
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namespace Codegen {
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@ -11,6 +12,71 @@ public:
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const std::vector<std::uint8_t>& codeSection,
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const RewriteRequest& request
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) const override;
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private:
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enum class ReferenceKind {
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None,
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Rel8Branch,
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Rel32Branch,
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RipRelativeDisp32
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};
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struct ReferenceSite {
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ReferenceKind Kind;
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std::size_t FieldOffset;
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};
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static constexpr std::uint8_t OpcodePrefixLock = 0xF0;
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static constexpr std::uint8_t OpcodePrefixRepne = 0xF2;
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static constexpr std::uint8_t OpcodePrefixRep = 0xF3;
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static constexpr std::uint8_t OpcodePrefixSegCs = 0x2E;
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static constexpr std::uint8_t OpcodePrefixSegSs = 0x36;
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static constexpr std::uint8_t OpcodePrefixSegDs = 0x3E;
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static constexpr std::uint8_t OpcodePrefixSegEs = 0x26;
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static constexpr std::uint8_t OpcodePrefixSegFs = 0x64;
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static constexpr std::uint8_t OpcodePrefixSegGs = 0x65;
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static constexpr std::uint8_t OpcodePrefixOperandSize = 0x66;
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static constexpr std::uint8_t OpcodePrefixAddressSize = 0x67;
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static constexpr std::uint8_t RexMin = 0x40;
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static constexpr std::uint8_t RexMax = 0x4F;
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static constexpr std::uint8_t TwoByteOpcodeEscape = 0x0F;
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static constexpr std::uint8_t OpcodeCallRel32 = 0xE8;
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static constexpr std::uint8_t OpcodeJmpRel32 = 0xE9;
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static constexpr std::uint8_t OpcodeJmpRel8 = 0xEB;
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static constexpr std::uint8_t OpcodeJccRel8Min = 0x70;
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static constexpr std::uint8_t OpcodeJccRel8Max = 0x7F;
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static constexpr std::uint8_t OpcodeJccRel32Min = 0x80;
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static constexpr std::uint8_t OpcodeJccRel32Max = 0x8F;
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static constexpr std::size_t Rel32InstructionLength = 5;
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static constexpr std::size_t Rel8FieldSize = 1;
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static constexpr std::size_t Rel32FieldSize = 4;
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static constexpr std::size_t Disp32FieldSize = 4;
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static constexpr std::uint8_t ModRmModShift = 6;
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static constexpr std::uint8_t ModRmModMask = 0x03;
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static constexpr std::uint8_t ModRmRmMask = 0x07;
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static constexpr std::uint8_t ModRmModIndirect = 0x00;
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static constexpr std::uint8_t ModRmRmRipRelative = 0x05;
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[[nodiscard]] static ReferenceSite ClassifyInstruction(
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const std::uint8_t* data,
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std::size_t length
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);
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[[nodiscard]] static std::int32_t ReadInt32(const std::uint8_t* data);
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static void WriteInt32(std::uint8_t* data, std::int32_t value);
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[[nodiscard]] static std::int64_t AdjustedDelta(
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std::int64_t instrPosition,
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std::int64_t targetPosition,
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std::int64_t cutStart,
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std::int64_t delta
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);
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};
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}
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@ -0,0 +1,219 @@
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#include <codegen/x86/X64InstructionRewriter.hpp>
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#include <codegen/x86/X64InstructionDecoder.hpp>
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#include <codegen/CodegenException.hpp>
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#include <codegen/IInstructionScanner.hpp>
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#include <cstdint>
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#include <limits>
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namespace Codegen {
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X64InstructionRewriter::ReferenceSite X64InstructionRewriter::ClassifyInstruction(
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const std::uint8_t* data,
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std::size_t length
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) {
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std::size_t pos = 0;
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while (pos < length) {
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const std::uint8_t b = data[pos];
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if (b == OpcodePrefixLock || b == OpcodePrefixRepne || b == OpcodePrefixRep ||
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b == OpcodePrefixSegCs || b == OpcodePrefixSegSs || b == OpcodePrefixSegDs ||
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b == OpcodePrefixSegEs || b == OpcodePrefixSegFs || b == OpcodePrefixSegGs ||
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b == OpcodePrefixOperandSize || b == OpcodePrefixAddressSize) {
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pos += 1;
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continue;
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}
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break;
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}
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if (pos < length && data[pos] >= RexMin && data[pos] <= RexMax) {
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pos += 1;
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}
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if (pos >= length) {
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return {ReferenceKind::None, 0};
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}
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std::uint8_t opcode = data[pos];
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const std::size_t opcodeOffset = pos;
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pos += 1;
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bool twoByteOpcode = false;
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if (opcode == TwoByteOpcodeEscape) {
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if (pos >= length) {
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return {ReferenceKind::None, 0};
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}
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twoByteOpcode = true;
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opcode = data[pos];
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pos += 1;
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}
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if (!twoByteOpcode) {
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if (opcode == OpcodeCallRel32 || opcode == OpcodeJmpRel32) {
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if (length >= opcodeOffset + Rel32InstructionLength) {
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return {ReferenceKind::Rel32Branch, pos};
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}
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return {ReferenceKind::None, 0};
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}
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if (opcode == OpcodeJmpRel8 || (opcode >= OpcodeJccRel8Min && opcode <= OpcodeJccRel8Max)) {
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if (length >= pos + Rel8FieldSize) {
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return {ReferenceKind::Rel8Branch, pos};
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}
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return {ReferenceKind::None, 0};
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}
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} else {
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if (opcode >= OpcodeJccRel32Min && opcode <= OpcodeJccRel32Max) {
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if (length >= pos + Rel32FieldSize) {
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return {ReferenceKind::Rel32Branch, pos};
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}
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return {ReferenceKind::None, 0};
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}
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}
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if (pos >= length) {
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return {ReferenceKind::None, 0};
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}
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const std::uint8_t modrm = data[pos];
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const std::uint8_t mod = static_cast<std::uint8_t>((modrm >> ModRmModShift) & ModRmModMask);
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const std::uint8_t rm = static_cast<std::uint8_t>(modrm & ModRmRmMask);
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if (mod == ModRmModIndirect && rm == ModRmRmRipRelative) {
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const std::size_t dispOffset = pos + 1;
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if (length >= dispOffset + Disp32FieldSize) {
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return {ReferenceKind::RipRelativeDisp32, dispOffset};
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}
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}
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return {ReferenceKind::None, 0};
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}
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std::int32_t X64InstructionRewriter::ReadInt32(const std::uint8_t* data) {
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return static_cast<std::int32_t>(
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static_cast<std::uint32_t>(data[0]) |
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(static_cast<std::uint32_t>(data[1]) << 8) |
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(static_cast<std::uint32_t>(data[2]) << 16) |
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(static_cast<std::uint32_t>(data[3]) << 24));
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}
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void X64InstructionRewriter::WriteInt32(std::uint8_t* data, std::int32_t value) {
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const auto unsignedValue = static_cast<std::uint32_t>(value);
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data[0] = static_cast<std::uint8_t>(unsignedValue & 0xFF);
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data[1] = static_cast<std::uint8_t>((unsignedValue >> 8) & 0xFF);
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data[2] = static_cast<std::uint8_t>((unsignedValue >> 16) & 0xFF);
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data[3] = static_cast<std::uint8_t>((unsignedValue >> 24) & 0xFF);
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}
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std::int64_t X64InstructionRewriter::AdjustedDelta(
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std::int64_t instrPosition,
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std::int64_t targetPosition,
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std::int64_t cutStart,
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std::int64_t delta
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) {
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const bool instrBeforeCut = instrPosition < cutStart;
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const bool targetBeforeCut = targetPosition < cutStart;
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if (instrBeforeCut == targetBeforeCut) {
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return 0;
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}
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return instrBeforeCut ? delta : -delta;
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}
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RewriteResult X64InstructionRewriter::Rewrite(
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const std::vector<std::uint8_t>& codeSection,
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const RewriteRequest& request
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) const {
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const auto offset = static_cast<std::size_t>(request.Offset);
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if (offset > codeSection.size()) {
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throw CodegenException("Rewrite offset is out of bounds", request.Offset);
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}
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const X64InstructionDecoder decoder;
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const auto decoded = decoder.Decode(codeSection.data() + offset, codeSection.size() - offset);
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if (!decoded.Valid || decoded.Length == 0) {
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throw CodegenException("Cannot decode instruction at rewrite offset", request.Offset);
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}
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const auto oldLength = static_cast<std::int64_t>(decoded.Length);
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const auto newLength = static_cast<std::int64_t>(request.NewBytes.size());
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const std::int64_t delta = newLength - oldLength;
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const auto cutStart = static_cast<std::int64_t>(offset);
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const std::int64_t cutEnd = cutStart + oldLength;
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std::vector<std::uint8_t> rewritten;
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rewritten.reserve(codeSection.size() + static_cast<std::size_t>(delta > 0 ? delta : 0));
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rewritten.insert(rewritten.end(), codeSection.begin(), codeSection.begin() + offset);
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rewritten.insert(rewritten.end(), request.NewBytes.begin(), request.NewBytes.end());
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rewritten.insert(rewritten.end(), codeSection.begin() + offset + decoded.Length, codeSection.end());
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const auto scanner = MakeInstructionScanner();
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const auto matches = scanner->ScanCodeSection(codeSection, 0, codeSection.size());
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std::vector<AddressAdjustment> adjustments;
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for (const auto& match : matches) {
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const auto matchOffset = static_cast<std::int64_t>(match.Offset);
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if (matchOffset >= cutStart && matchOffset < cutEnd) {
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continue;
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}
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const auto site = ClassifyInstruction(codeSection.data() + match.Offset, match.Length);
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if (site.Kind != ReferenceKind::None) {
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const std::int64_t instrEnd = matchOffset + static_cast<std::int64_t>(match.Length);
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const std::size_t fieldPosition = static_cast<std::size_t>(match.Offset) + site.FieldOffset;
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if (site.Kind == ReferenceKind::Rel8Branch) {
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const auto disp = static_cast<std::int8_t>(codeSection[fieldPosition]);
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const std::int64_t targetPosition = instrEnd + disp;
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const std::int64_t adjust = AdjustedDelta(matchOffset, targetPosition, cutStart, delta);
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if (adjust != 0) {
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const std::int64_t newDisp = static_cast<std::int64_t>(disp) + adjust;
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if (newDisp < std::numeric_limits<std::int8_t>::min() ||
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newDisp > std::numeric_limits<std::int8_t>::max()) {
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throw CodegenException("Rel8 branch displacement overflow after rewrite", match.Offset);
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}
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const std::int64_t newMatchOffset = matchOffset < cutStart ? matchOffset : matchOffset + delta;
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const auto newFieldPosition = static_cast<std::size_t>(
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newMatchOffset + static_cast<std::int64_t>(site.FieldOffset));
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rewritten[newFieldPosition] = static_cast<std::uint8_t>(static_cast<std::int8_t>(newDisp));
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}
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} else {
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const auto disp = ReadInt32(codeSection.data() + fieldPosition);
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const std::int64_t targetPosition = instrEnd + disp;
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const std::int64_t adjust = AdjustedDelta(matchOffset, targetPosition, cutStart, delta);
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if (adjust != 0) {
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const std::int64_t newDisp = static_cast<std::int64_t>(disp) + adjust;
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if (newDisp < std::numeric_limits<std::int32_t>::min() ||
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newDisp > std::numeric_limits<std::int32_t>::max()) {
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throw CodegenException("Rel32/disp32 displacement overflow after rewrite", match.Offset);
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}
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const std::int64_t newMatchOffset = matchOffset < cutStart ? matchOffset : matchOffset + delta;
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const auto newFieldPosition = static_cast<std::size_t>(
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newMatchOffset + static_cast<std::int64_t>(site.FieldOffset));
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WriteInt32(rewritten.data() + newFieldPosition, static_cast<std::int32_t>(newDisp));
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}
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}
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}
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if (matchOffset >= cutEnd && delta != 0) {
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const auto newOffset = static_cast<Domain::FileByteOffset>(matchOffset + delta);
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adjustments.push_back({match.Offset, newOffset, delta});
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}
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}
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return {rewritten, adjustments};
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}
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}
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