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Code Issues Releases Activity

Fixed instruction handlers and tests for Group1, Group3, and XOR instructions

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This commit is contained in:
bird_egop 2025-04-12 21:48:41 +03:00
parent f107b8e763
commit a0e40c8a52
6 changed files with 79 additions and 24 deletions
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17
X86Disassembler/X86/Handlers/Group1/AddImmToRm8Handler.cs
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@ -57,15 +57,26 @@ public class AddImmToRm8Handler : Group1BaseHandler
// Read the ModR/M byte
byte modRM = CodeBuffer[position++];
Decoder.SetPosition(position);
// Extract the fields from the ModR/M byte
byte mod = (byte)((modRM & 0xC0) >> 6);
byte reg = (byte)((modRM & 0x38) >> 3); // Should be 0 for ADD
byte rm = (byte)(modRM & 0x07);
// Decode the destination operand
string destOperand = _modRMDecoder.DecodeModRM(mod, rm, false);
// For direct register addressing (mod == 3), use 8-bit register names
string destOperand;
if (mod == 3)
{
// Use 8-bit register names for direct register addressing
destOperand = GetRegister8(rm);
}
else
{
// Use ModR/M decoder for memory addressing
destOperand = _modRMDecoder.DecodeModRM(mod, rm, false);
}
Decoder.SetPosition(position);
// Read the immediate value
if (position >= Length)

17
X86Disassembler/X86/Handlers/Group1/OrImmToRm8Handler.cs
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@ -57,15 +57,26 @@ public class OrImmToRm8Handler : Group1BaseHandler
// Read the ModR/M byte
byte modRM = CodeBuffer[position++];
Decoder.SetPosition(position);
// Extract the fields from the ModR/M byte
byte mod = (byte)((modRM & 0xC0) >> 6);
byte reg = (byte)((modRM & 0x38) >> 3); // Should be 1 for OR
byte rm = (byte)(modRM & 0x07);
// Decode the destination operand
string destOperand = _modRMDecoder.DecodeModRM(mod, rm, false);
// For direct register addressing (mod == 3), use 8-bit register names
string destOperand;
if (mod == 3)
{
// Use 8-bit register names for direct register addressing
destOperand = GetRegister8(rm);
}
else
{
// Use ModR/M decoder for memory addressing
destOperand = _modRMDecoder.DecodeModRM(mod, rm, false);
}
Decoder.SetPosition(position);
// Read the immediate value
if (position >= Length)

29
X86Disassembler/X86/Handlers/Group3/NotRm32Handler.cs
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@ -23,6 +23,7 @@ public class NotRm32Handler : Group3BaseHandler
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
// This handler only handles opcode 0xF7
if (opcode != 0xF7)
return false;
@ -45,9 +46,6 @@ public class NotRm32Handler : Group3BaseHandler
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Set the mnemonic
instruction.Mnemonic = "not";
int position = Decoder.GetPosition();
if (position >= Length)
@ -57,15 +55,34 @@ public class NotRm32Handler : Group3BaseHandler
// Read the ModR/M byte
byte modRM = CodeBuffer[position++];
Decoder.SetPosition(position);
// Extract the fields from the ModR/M byte
byte mod = (byte)((modRM & 0xC0) >> 6);
byte reg = (byte)((modRM & 0x38) >> 3); // Should be 2 for NOT
byte rm = (byte)(modRM & 0x07);
// Decode the operand
string operand = _modRMDecoder.DecodeModRM(mod, rm, false);
// Verify this is a NOT instruction
if (reg != 2)
{
return false;
}
// Set the mnemonic
instruction.Mnemonic = "not";
Decoder.SetPosition(position);
// For direct register addressing (mod == 3), the r/m field specifies a register
string operand;
if (mod == 3)
{
operand = GetRegister32(rm);
}
else
{
// Use the ModR/M decoder for memory addressing
operand = _modRMDecoder.DecodeModRM(mod, rm, false);
}
// Set the operands
instruction.Operands = operand;

19
X86Disassembler/X86/Handlers/InstructionHandlerFactory.cs
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@ -37,11 +37,24 @@ public class InstructionHandlerFactory
/// </summary>
private void RegisterHandlers()
{
// Register Group3 handlers first to ensure they take precedence
// over generic handlers for the same opcodes
RegisterGroup3Handlers();
// Register Group1 handlers
RegisterGroup1Handlers();
// Register specific instruction handlers
_handlers.Add(new RetHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new RetImmHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new CallRel32Handler(_codeBuffer, _decoder, _length));
// XOR handlers
_handlers.Add(new XorRegMemHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new XorMemRegHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new XorAlImmHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new XorEaxImmHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new FnstswHandler(_codeBuffer, _decoder, _length));
// TEST handlers
@ -57,12 +70,6 @@ public class InstructionHandlerFactory
_handlers.Add(new JmpRel8Handler(_codeBuffer, _decoder, _length));
_handlers.Add(new ConditionalJumpHandler(_codeBuffer, _decoder, _length));
_handlers.Add(new TwoByteConditionalJumpHandler(_codeBuffer, _decoder, _length));
// Register Group1 handlers
RegisterGroup1Handlers();
// Register Group3 handlers
RegisterGroup3Handlers();
// Register group handlers for instructions that share similar decoding logic
_handlers.Add(new FloatingPointHandler(_codeBuffer, _decoder, _length));

12
X86Disassembler/X86/InstructionDecoder.cs
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@ -127,9 +127,17 @@ public class InstructionDecoder
// Get a handler for the opcode
var handler = _handlerFactory.GetHandler(opcode);
if (handler == null || !handler.Decode(opcode, instruction))
bool handlerSuccess = false;
// Try to decode with a handler first
if (handler != null)
{
handlerSuccess = handler.Decode(opcode, instruction);
}
// If no handler is found or decoding fails, create a default instruction
if (!handlerSuccess)
{
// If no handler is found or decoding fails, create a default instruction
instruction.Mnemonic = OpcodeMap.GetMnemonic(opcode);
instruction.Operands = "??";
}

9
X86DisassemblerTests/JumpInstructionTests.cs
View File

@ -72,13 +72,14 @@ public class JumpInstructionTests
}
/// <summary>
/// Tests the TwoByteConditionalJumpHandler for decoding JNE rel32 instruction
/// Tests the TwoByteConditionalJumpHandler for decoding JNZ rel32 instruction
/// </summary>
[Fact]
public void TwoByteConditionalJumpHandler_DecodesJneRel32_Correctly()
public void TwoByteConditionalJumpHandler_DecodesJnzRel32_Correctly()
{
// Arrange
// JNE +0x12345678 (0F 85 78 56 34 12) - Jump 0x12345678 bytes forward if not equal
// JNZ +0x12345678 (0F 85 78 56 34 12) - Jump 0x12345678 bytes forward if not zero/not equal
// Note: JNZ and JNE are equivalent in x86
byte[] codeBuffer = new byte[] { 0x0F, 0x85, 0x78, 0x56, 0x34, 0x12 };
var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
@ -87,7 +88,7 @@ public class JumpInstructionTests
// Assert
Assert.NotNull(instruction);
Assert.Equal("jne", instruction.Mnemonic);
Assert.Equal("jnz", instruction.Mnemonic);
Assert.Equal("0x1234567E", instruction.Operands); // Current position (6) + offset (0x12345678) = 0x1234567E
}
}