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Code Issues Releases Activity

Fixed segment override prefix handling for 0x64 (FS) opcode with tests

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This commit is contained in:
bird_egop
2025-04-13 01:39:38 +03:00
parent b4a85d2839
commit bfaeba0d5f
2 changed files with 81 additions and 4 deletions
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34
X86Disassembler/X86/InstructionDecoder.cs
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@ -86,7 +86,7 @@ public class InstructionDecoder
_addressSizePrefix = true;
_position++;
}
else if (prefix >= 0x26 && prefix <= 0x3E && (prefix & 0x7) == 0x6) // Segment override prefix
else if ((prefix >= 0x26 && prefix <= 0x3E && (prefix & 0x7) == 0x6) || prefix == 0x64 || prefix == 0x65) // Segment override prefix
{
_segmentOverridePrefix = true;
switch (prefix)
@ -118,6 +118,21 @@ public class InstructionDecoder
if (_position >= _length)
{
// If we reached the end of the buffer while processing prefixes,
// create an instruction with just the prefix information
if (_segmentOverridePrefix)
{
instruction.Mnemonic = _segmentOverride;
instruction.Operands = "";
// Set the raw bytes
int length = _position - startPosition;
instruction.RawBytes = new byte[length];
Array.Copy(_codeBuffer, startPosition, instruction.RawBytes, 0, length);
return instruction;
}
return null;
}
@ -142,10 +157,21 @@ public class InstructionDecoder
instruction.Operands = "??";
}
// Add segment override prefix to the instruction if present
if (_segmentOverridePrefix && !string.IsNullOrEmpty(instruction.Operands))
{
// If the instruction has memory operands, add the segment override
if (instruction.Operands.Contains("["))
{
// Replace the first '[' with the segment override
instruction.Operands = instruction.Operands.Replace("[", $"{_segmentOverride}:[" );
}
}
// Set the raw bytes
int length = _position - startPosition;
instruction.RawBytes = new byte[length];
Array.Copy(_codeBuffer, startPosition, instruction.RawBytes, 0, length);
int instructionLength = _position - startPosition;
instruction.RawBytes = new byte[instructionLength];
Array.Copy(_codeBuffer, startPosition, instruction.RawBytes, 0, instructionLength);
return instruction;
}