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Fix x86 disassembler issues with direct memory addressing and immediate value formatting

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bird_egop
2025-04-15 02:29:32 +03:00
parent d351f41808
commit 3ea327064a
67 changed files with 854 additions and 453 deletions
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37
X86Disassembler/X86/Handlers/Nop/MultiByteNopHandler.cs
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@ -74,7 +74,7 @@ public class MultiByteNopHandler : InstructionHandler
// Set the instruction type
instruction.Type = InstructionType.Nop;
// Skip the second byte (0x1F)
// Read the second byte (0x1F)
Decoder.ReadByte();
// Check if we have enough bytes to read the ModR/M byte
@ -89,14 +89,13 @@ public class MultiByteNopHandler : InstructionHandler
// Determine the size of the operand
int operandSize = hasOperandSizePrefix ? 16 : 32;
// Read the ModR/M byte but don't advance the position yet
byte modRm = Decoder.PeakByte();
// Read the ModR/M byte
byte modRm = Decoder.ReadByte();
// Default memory operand parameters
RegisterIndex baseReg = RegisterIndex.A;
RegisterIndex? indexReg = null;
int scale = 0;
int bytesToSkip = 1; // Skip at least the ModR/M byte
// Try to find a matching NOP variant (we check longest patterns first)
foreach (var (variantModRm, expectedBytes, variantBaseReg, variantIndexReg, variantScale) in NopVariants)
@ -108,18 +107,29 @@ public class MultiByteNopHandler : InstructionHandler
}
// Check if we have enough bytes for this pattern
if (!Decoder.CanRead(expectedBytes.Length + 1)) // +1 for ModR/M byte
if (!Decoder.CanRead(expectedBytes.Length))
{
continue;
}
// Create a buffer to read the expected bytes
byte[] buffer = new byte[expectedBytes.Length];
// Read the bytes into the buffer without advancing the decoder position
for (int i = 0; i < expectedBytes.Length; i++)
{
if (!Decoder.CanReadByte())
{
break;
}
buffer[i] = Decoder.PeakByte(i);
}
// Check if the expected bytes match
bool isMatch = true;
for (int i = 0; i < expectedBytes.Length; i++)
{
// Check the byte at position
byte actualByte = Decoder.PeakByte();
if (actualByte != expectedBytes[i])
if (buffer[i] != expectedBytes[i])
{
isMatch = false;
break;
@ -132,14 +142,17 @@ public class MultiByteNopHandler : InstructionHandler
baseReg = variantBaseReg;
indexReg = variantIndexReg;
scale = variantScale;
bytesToSkip = 1 + expectedBytes.Length; // ModR/M byte + additional bytes
// Consume the expected bytes
for (int i = 0; i < expectedBytes.Length; i++)
{
Decoder.ReadByte();
}
break;
}
}
// Skip the bytes we've processed
Decoder.SetPosition(Decoder.GetPosition() + bytesToSkip);
// Create the appropriate structured operand based on the NOP variant
if (indexReg.HasValue && scale > 0)
{