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Code Issues Releases Activity

Fixed instruction boundary detection for complex instruction sequences

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This commit is contained in:
bird_egop
2025-04-13 03:08:37 +03:00
parent 33b151d856
commit e12f5b5bdf
4 changed files with 267 additions and 23 deletions
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51
X86Disassembler/X86/Handlers/Add/AddEaxImmHandler.cs
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@ -34,24 +34,67 @@ 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";
// Read the immediate value
int position = Decoder.GetPosition();
if (position + 4 > Length)
// 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
}
// 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)
{
// 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;
}
// Read the 32-bit immediate value
uint imm32 = Decoder.ReadUInt32();
uint imm32 = 0;
for (int i = 0; i < 4; i++)
{
if (startPosition + i < Length)
{
imm32 |= (uint)(CodeBuffer[startPosition + i] << (i * 8));
}
}
// Advance the decoder position
Decoder.SetPosition(startPosition + 4);
// Set the operands
instruction.Operands = $"eax, 0x{imm32:X8}";
// 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;
return true;
}
}