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Code Issues Releases Activity

Moved AND instruction handlers from ArithmeticImmediate to dedicated And namespace for better organization

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bird_egop 2025-04-13 04:11:06 +03:00
parent af94b88868
commit e8a16e7ecd
4 changed files with 0 additions and 263 deletions
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84
X86Disassembler/X86/Handlers/ArithmeticImmediate/AndImmWithRm32Handler.cs
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@ -1,84 +0,0 @@
namespace X86Disassembler.X86.Handlers.ArithmeticImmediate;
/// <summary>
/// Handler for AND r/m32, imm32 instruction (0x81 /4)
/// </summary>
public class AndImmWithRm32Handler : InstructionHandler
{
/// <summary>
/// Initializes a new instance of the AndImmWithRm32Handler class
/// </summary>
/// <param name="codeBuffer">The buffer containing the code to decode</param>
/// <param name="decoder">The instruction decoder that owns this handler</param>
/// <param name="length">The length of the buffer</param>
public AndImmWithRm32Handler(byte[] codeBuffer, InstructionDecoder decoder, int length)
: base(codeBuffer, decoder, length)
{
}
/// <summary>
/// Checks if this handler can decode the given opcode
/// </summary>
/// <param name="opcode">The opcode to check</param>
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
if (opcode != 0x81)
return false;
// Check if the reg field of the ModR/M byte is 4 (AND)
int position = Decoder.GetPosition();
if (position >= Length)
return false;
byte modRM = CodeBuffer[position];
byte reg = (byte)((modRM & 0x38) >> 3);
return reg == 4; // 4 = AND
}
/// <summary>
/// Decodes an AND r/m32, imm32 instruction
/// </summary>
/// <param name="opcode">The opcode of the instruction</param>
/// <param name="instruction">The instruction object to populate</param>
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Set the mnemonic
instruction.Mnemonic = "and";
int position = Decoder.GetPosition();
if (position >= Length)
{
return false;
}
// 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 4 for AND
byte rm = (byte)(modRM & 0x07);
// Decode the destination operand
string destOperand = ModRMDecoder.DecodeModRM(mod, rm, false);
// Read the immediate value
if (position + 3 >= Length)
{
return false;
}
uint imm32 = BitConverter.ToUInt32(CodeBuffer, position);
Decoder.SetPosition(position + 4);
// Set the operands
instruction.Operands = $"{destOperand}, 0x{imm32:X8}";
return true;
}
}

85
X86Disassembler/X86/Handlers/ArithmeticImmediate/AndImmWithRm32SignExtendedHandler.cs
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@ -1,85 +0,0 @@
namespace X86Disassembler.X86.Handlers.ArithmeticImmediate;
/// <summary>
/// Handler for AND r/m32, imm8 (sign-extended) instruction (0x83 /4)
/// </summary>
public class AndImmWithRm32SignExtendedHandler : InstructionHandler
{
/// <summary>
/// Initializes a new instance of the AndImmWithRm32SignExtendedHandler class
/// </summary>
/// <param name="codeBuffer">The buffer containing the code to decode</param>
/// <param name="decoder">The instruction decoder that owns this handler</param>
/// <param name="length">The length of the buffer</param>
public AndImmWithRm32SignExtendedHandler(byte[] codeBuffer, InstructionDecoder decoder, int length)
: base(codeBuffer, decoder, length)
{
}
/// <summary>
/// Checks if this handler can decode the given opcode
/// </summary>
/// <param name="opcode">The opcode to check</param>
/// <returns>True if this handler can decode the opcode</returns>
public override bool CanHandle(byte opcode)
{
if (opcode != 0x83)
return false;
// Check if the reg field of the ModR/M byte is 4 (AND)
int position = Decoder.GetPosition();
if (position >= Length)
return false;
byte modRM = CodeBuffer[position];
byte reg = (byte)((modRM & 0x38) >> 3);
return reg == 4; // 4 = AND
}
/// <summary>
/// Decodes an AND r/m32, imm8 (sign-extended) instruction
/// </summary>
/// <param name="opcode">The opcode of the instruction</param>
/// <param name="instruction">The instruction object to populate</param>
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Set the mnemonic
instruction.Mnemonic = "and";
int position = Decoder.GetPosition();
if (position >= Length)
{
return false;
}
// 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 4 for AND
byte rm = (byte)(modRM & 0x07);
// Decode the destination operand
string destOperand = ModRMDecoder.DecodeModRM(mod, rm, false);
// Read the immediate value (sign-extended from 8 to 32 bits)
if (position >= Length)
{
return false;
}
sbyte imm8 = (sbyte)CodeBuffer[position];
int imm32 = imm8; // Sign-extend to 32 bits
Decoder.SetPosition(position + 1);
// Set the operands
instruction.Operands = $"{destOperand}, 0x{imm32:X8}";
return true;
}
}

4
X86Disassembler/X86/Handlers/InstructionHandlerFactory.cs
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@ -114,10 +114,6 @@ public class InstructionHandlerFactory
_handlers.Add(new SbbImmFromRm32Handler(_codeBuffer, _decoder, _length)); _handlers.Add(new SbbImmFromRm32Handler(_codeBuffer, _decoder, _length));
_handlers.Add(new SbbImmFromRm32SignExtendedHandler(_codeBuffer, _decoder, _length)); _handlers.Add(new SbbImmFromRm32SignExtendedHandler(_codeBuffer, _decoder, _length));
// AND handlers
_handlers.Add(new AndImmWithRm32Handler(_codeBuffer, _decoder, _length));
_handlers.Add(new AndImmWithRm32SignExtendedHandler(_codeBuffer, _decoder, _length));
// SUB handlers // SUB handlers
_handlers.Add(new SubImmFromRm32Handler(_codeBuffer, _decoder, _length)); _handlers.Add(new SubImmFromRm32Handler(_codeBuffer, _decoder, _length));
_handlers.Add(new SubImmFromRm32SignExtendedHandler(_codeBuffer, _decoder, _length)); _handlers.Add(new SubImmFromRm32SignExtendedHandler(_codeBuffer, _decoder, _length));

90
X86DisassemblerTests/SequenceDebuggingTests.cs
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@ -1,90 +0,0 @@
namespace X86DisassemblerTests;
using System;
using Xunit;
using X86Disassembler.X86;
using X86Disassembler.X86.Handlers;
using X86Disassembler.X86.Handlers.ArithmeticImmediate;
using X86Disassembler.X86.Handlers.Inc;
/// <summary>
/// Tests for debugging the specific problematic sequence
/// </summary>
public class SequenceDebuggingTests
{
/// <summary>
/// Tests each byte in the problematic sequence individually
/// </summary>
[Fact]
public void Debug_ProblematicSequence_ByteByByte()
{
// The problematic sequence
byte[] fullSequence = new byte[] { 0x08, 0x83, 0xC1, 0x04, 0x50, 0xE8, 0x42, 0x01, 0x00, 0x00 };
// Test each byte individually
for (int i = 0; i < fullSequence.Length; i++)
{
byte opcode = fullSequence[i];
string expectedMnemonic = GetExpectedMnemonic(opcode);
// Create a buffer with just this byte
byte[] buffer = new byte[] { opcode };
var decoder = new InstructionDecoder(buffer, buffer.Length);
var factory = new InstructionHandlerFactory(buffer, decoder, buffer.Length);
// Get the handler for this opcode
var handler = factory.GetHandler(opcode);
// Output debug information
Console.WriteLine($"Byte 0x{opcode:X2} at position {i}: Handler = {(handler != null ? handler.GetType().Name : "null")}");
// If we have a handler, decode the instruction
if (handler != null)
{
var instruction = new Instruction();
bool success = handler.Decode(opcode, instruction);
Console.WriteLine($" Decoded as: {instruction.Mnemonic} {instruction.Operands}");
}
}
// Now test the specific sequence 0x83 0xC1 0x04 (ADD ecx, 0x04)
byte[] addSequence = new byte[] { 0x83, 0xC1, 0x04 };
var addDecoder = new InstructionDecoder(addSequence, addSequence.Length);
var addInstruction = addDecoder.DecodeInstruction();
Console.WriteLine($"\nDecoding 0x83 0xC1 0x04 directly: {addInstruction?.Mnemonic} {addInstruction?.Operands}");
// Now test the sequence 0x08 0x83 0xC1 0x04
byte[] orAddSequence = new byte[] { 0x08, 0x83, 0xC1, 0x04 };
var orAddDecoder = new InstructionDecoder(orAddSequence, orAddSequence.Length);
// Decode the first instruction (0x08)
var orInstruction = orAddDecoder.DecodeInstruction();
Console.WriteLine($"\nDecoding 0x08 in sequence 0x08 0x83 0xC1 0x04: {orInstruction?.Mnemonic} {orInstruction?.Operands}");
// Decode the second instruction (0x83 0xC1 0x04)
var secondInstruction = orAddDecoder.DecodeInstruction();
Console.WriteLine($"Decoding 0x83 0xC1 0x04 after 0x08: {secondInstruction?.Mnemonic} {secondInstruction?.Operands}");
// Assert that we get the expected mnemonic for the second instruction
Assert.Equal("add", secondInstruction?.Mnemonic);
}
/// <summary>
/// Gets the expected mnemonic for a given opcode
/// </summary>
private string GetExpectedMnemonic(byte opcode)
{
return opcode switch
{
0x08 => "or",
0x83 => "add", // Assuming reg field is 0 (ADD)
0x50 => "push",
0xE8 => "call",
0x40 => "inc",
0x41 => "inc",
0x42 => "inc",
_ => "??"
};
}
}