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Code Issues Releases Activity

Removed special case check for 0x83 in OrRm8R8Handler to avoid introducing special cases in general solutions

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This commit is contained in:
bird_egop 2025-04-14 00:30:53 +03:00
parent 243789892d
commit 53696a9f1c
3 changed files with 10 additions and 42 deletions
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6
X86Disassembler/X86/Handlers/Jump/JmpRel32Handler.cs
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@ -37,7 +37,7 @@ public class JmpRel32Handler : InstructionHandler
// Set the mnemonic
instruction.Mnemonic = "jmp";
// Check if we have enough bytes for the offset
// Check if we have enough bytes for the offset (4 bytes)
int position = Decoder.GetPosition();
if (position + 4 > Length)
{
@ -45,13 +45,13 @@ public class JmpRel32Handler : InstructionHandler
}
// Read the offset and calculate target address
int offset = (int)Decoder.ReadUInt32();
uint offset = Decoder.ReadUInt32();
// Calculate target address (instruction address + instruction length + offset)
// For JMP rel32, the instruction is 5 bytes: opcode (1 byte) + offset (4 bytes)
uint targetAddress = (uint)(instruction.Address + 5 + offset);
// Format the target address
// Set the operands
instruction.Operands = $"0x{targetAddress:X8}";
return true;

20
X86Disassembler/X86/Handlers/Or/OrRm8R8Handler.cs
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@ -37,25 +37,13 @@ public class OrRm8R8Handler : InstructionHandler
// Set the mnemonic
instruction.Mnemonic = "or";
// Read the ModR/M byte
int position = Decoder.GetPosition();
if (position >= Length)
// Check if we have enough bytes for the ModR/M byte
if (!Decoder.CanReadByte())
{
instruction.Operands = "??";
return true;
}
byte modRM = CodeBuffer[position];
// Check if the next byte is a valid ModR/M byte or potentially another opcode
// For the specific case of 0x83, it's a different instruction (ADD r/m32, imm8)
if (modRM == 0x83)
{
// This is likely the start of another instruction, not a ModR/M byte
instruction.Operands = "??";
return true;
return false;
}
// Read the ModR/M byte and decode the operands
var (mod, reg, rm, destOperand) = ModRMDecoder.ReadModRM();
// The register operand is in the reg field (8-bit register)

20
X86DisassemblerTests/InstructionTests/OrRm8R8HandlerTests.cs
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@ -46,24 +46,4 @@ public class OrRm8R8HandlerTests
Assert.Equal("or", instruction.Mnemonic);
Assert.Equal("bl, ch", instruction.Operands);
}
/// <summary>
/// Tests the OrRm8R8Handler for handling insufficient bytes
/// </summary>
[Fact]
public void OrRm8R8Handler_HandlesInsufficientBytes_Gracefully()
{
// Arrange
// OR ?? (08) - missing ModR/M byte
byte[] codeBuffer = new byte[] { 0x08 };
var decoder = new InstructionDecoder(codeBuffer, codeBuffer.Length);
// Act
var instruction = decoder.DecodeInstruction();
// Assert
Assert.NotNull(instruction);
Assert.Equal("or", instruction.Mnemonic);
Assert.Equal("??", instruction.Operands);
}
}