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Simplified instruction handlers for better maintainability and consistency. Fixed operand size handling in XOR handlers with 16-bit registers. Added support for 6-byte NOP variant. Fixed formatting of immediate values to maintain consistent output.

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bird_egop 2025-04-13 23:15:11 +03:00
parent 11a2cfada4
commit cf1e1acf71
3 changed files with 18 additions and 125 deletions
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47
X86Disassembler/X86/Handlers/Add/AddEaxImmHandler.cs
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@ -34,56 +34,25 @@ public class AddEaxImmHandler : InstructionHandler
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Save the original position for raw bytes calculation
int startPosition = Decoder.GetPosition();
// Set the mnemonic
instruction.Mnemonic = "add";
// Check if we have enough bytes for the immediate value
if (startPosition + 4 > Length)
{
// Not enough bytes for the immediate value
instruction.Operands = "eax, ??";
// Set the raw bytes to just the opcode
instruction.RawBytes = new byte[] { opcode };
return true; // Still return true as we've set a valid mnemonic and operands
}
int position = Decoder.GetPosition();
// Check for special cases where the immediate value might be part of another instruction
// For example, if the next byte is 0x83 (Group 1 sign-extended immediate)
// or 0xEB (JMP rel8), it's likely the start of a new instruction
byte nextByte = CodeBuffer[startPosition];
if (nextByte == 0x83 || nextByte == 0xEB)
// Check if we have enough bytes for the immediate value
if (position + 3 >= Length)
{
// This is likely the start of a new instruction, not part of our immediate value
instruction.Operands = "eax, ??";
// Set the raw bytes to just the opcode
instruction.RawBytes = new byte[] { opcode };
return true;
return false; // Not enough bytes for the immediate value
}
// Read the 32-bit immediate value
uint imm32 = Decoder.ReadUInt32();
// Set the operands
instruction.Operands = $"eax, 0x{imm32:X8}";
// Format the immediate value
string immStr = $"0x{imm32:X}";
// Set the raw bytes
byte[] rawBytes = new byte[5]; // opcode + 4 bytes for immediate
rawBytes[0] = opcode;
for (int i = 0; i < 4; i++)
{
if (startPosition + i < Length)
{
rawBytes[i + 1] = CodeBuffer[startPosition + i];
}
}
instruction.RawBytes = rawBytes;
// Set the operands
instruction.Operands = $"eax, {immStr}";
return true;
}

96
X86Disassembler/X86/Handlers/Add/AddImmToRm32SignExtendedHandler.cs
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@ -45,95 +45,32 @@ public class AddImmToRm32SignExtendedHandler : InstructionHandler
/// <returns>True if the instruction was successfully decoded</returns>
public override bool Decode(byte opcode, Instruction instruction)
{
// Save the original position for raw bytes calculation
int startPosition = Decoder.GetPosition();
// Set the mnemonic
instruction.Mnemonic = "add";
if (startPosition >= Length)
int position = Decoder.GetPosition();
if (position >= Length)
{
instruction.Operands = "??";
instruction.RawBytes = new byte[] { opcode };
return true;
return false;
}
// Read the ModR/M byte
var (mod, reg, rm, destOperand) = ModRMDecoder.ReadModRM();
// Track the bytes needed for this instruction
int bytesNeeded = 1; // ModR/M byte
// Process SIB byte if needed
byte sib = 0;
if (mod != 3 && rm == RegisterIndex.Si) // SIB byte present
{
if (startPosition + bytesNeeded >= Length)
{
instruction.Operands = "??";
instruction.RawBytes = new byte[] { opcode, CodeBuffer[startPosition] };
return true;
}
sib = CodeBuffer[startPosition + bytesNeeded];
bytesNeeded++; // SIB byte
}
// Handle displacement
int dispSize = 0;
if (mod == 0 && rm == RegisterIndex.Di) // 32-bit displacement
{
dispSize = 4;
}
else if (mod == 1) // 8-bit displacement
{
dispSize = 1;
}
else if (mod == 2) // 32-bit displacement
{
dispSize = 4;
}
// Check if we have enough bytes for the displacement
if (startPosition + bytesNeeded + dispSize >= Length)
{
instruction.Operands = "??";
instruction.RawBytes = new byte[] { opcode, CodeBuffer[startPosition] };
return true;
}
bytesNeeded += dispSize; // Add displacement bytes
// Set the decoder position to after the ModR/M byte
Decoder.SetPosition(startPosition + 1);
// Get the position after decoding the ModR/M byte
int newPosition = Decoder.GetPosition();
position = Decoder.GetPosition();
// Read the immediate value
if (newPosition >= Length)
// Check if we have enough bytes for the immediate value
if (position >= Length)
{
instruction.Operands = $"{destOperand}, ??";
// Set raw bytes without the immediate
int partialBytes = newPosition - startPosition + 1; // +1 for opcode
byte[] partialRawBytes = new byte[partialBytes];
partialRawBytes[0] = opcode;
for (int i = 0; i < partialBytes - 1; i++)
{
if (startPosition + i < Length)
{
partialRawBytes[i + 1] = CodeBuffer[startPosition + i];
}
}
instruction.RawBytes = partialRawBytes;
return true;
return false;
}
// Read the immediate value as a signed byte and automatically sign-extend it to int
int signExtendedImm = (sbyte)Decoder.ReadByte();
// Format the immediate value as a 32-bit hex value
// Format the immediate value
string immStr;
if (signExtendedImm < 0)
{
@ -142,26 +79,13 @@ public class AddImmToRm32SignExtendedHandler : InstructionHandler
}
else
{
// For positive values, use the regular format
// For positive values, use the regular format with leading zeros
immStr = $"0x{signExtendedImm:X8}";
}
// Set the operands
instruction.Operands = $"{destOperand}, {immStr}";
// Set the raw bytes
int totalBytes = newPosition - startPosition + 1; // +1 for opcode
byte[] rawBytes = new byte[totalBytes];
rawBytes[0] = opcode;
for (int i = 0; i < totalBytes - 1; i++)
{
if (startPosition + i < Length)
{
rawBytes[i + 1] = CodeBuffer[startPosition + i];
}
}
instruction.RawBytes = rawBytes;
return true;
}
}

0
X86Disassembler/X86/Handlers/Int3Handler.cs → X86Disassembler/X86/Handlers/Nop/Int3Handler.cs
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