Fixed disassembler regression by adding handlers for TEST r/m8, r8 and TEST r/m8, imm8 instructions

X86Disassembler/X86/Handlers/Group3/TestImmWithRm8Handler.cs

@@ -0,0 +1,107 @@
+namespace X86Disassembler.X86.Handlers.Group3;
+
+/// <summary>
+/// Handler for TEST r/m8, imm8 instruction (0xF6 /0)
+/// </summary>
+public class TestImmWithRm8Handler : Group3BaseHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the TestImmWithRm8Handler class
+    /// </summary>
+    /// <param name="codeBuffer">The buffer containing the code to decode</param>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    /// <param name="length">The length of the buffer</param>
+    public TestImmWithRm8Handler(byte[] codeBuffer, InstructionDecoder decoder, int length) 
+        : base(codeBuffer, decoder, length)
+    {
+    }
+    
+    /// <summary>
+    /// Checks if this handler can decode the given opcode
+    /// </summary>
+    /// <param name="opcode">The opcode to check</param>
+    /// <returns>True if this handler can decode the opcode</returns>
+    public override bool CanHandle(byte opcode)
+    {
+        if (opcode != 0xF6)
+            return false;
+            
+        // Check if the reg field of the ModR/M byte is 0 (TEST)
+        int position = Decoder.GetPosition();
+        if (position >= Length)
+            return false;
+            
+        byte modRM = CodeBuffer[position];
+        byte reg = (byte)((modRM & 0x38) >> 3);
+        
+        return reg == 0; // 0 = TEST
+    }
+    
+    /// <summary>
+    /// Decodes a TEST r/m8, imm8 instruction
+    /// </summary>
+    /// <param name="opcode">The opcode of the instruction</param>
+    /// <param name="instruction">The instruction object to populate</param>
+    /// <returns>True if the instruction was successfully decoded</returns>
+    public override bool Decode(byte opcode, Instruction instruction)
+    {
+        // Set the mnemonic
+        instruction.Mnemonic = "test";
+        
+        int position = Decoder.GetPosition();
+        
+        if (position >= Length)
+        {
+            return false;
+        }
+        
+        // Read the ModR/M byte
+        byte modRM = CodeBuffer[position++];
+        Decoder.SetPosition(position);
+        
+        // Extract the fields from the ModR/M byte
+        byte mod = (byte)((modRM & 0xC0) >> 6);
+        byte reg = (byte)((modRM & 0x38) >> 3); // Should be 0 for TEST
+        byte rm = (byte)(modRM & 0x07);
+        
+        // Decode the destination operand
+        string destOperand;
+        
+        // Special case for direct register addressing (mod == 3)
+        if (mod == 3)
+        {
+            // Get the register name based on the rm field
+            destOperand = GetRegister8(rm);
+        }
+        else
+        {
+            // Use the ModR/M decoder for memory addressing
+            destOperand = _modRMDecoder.DecodeModRM(mod, rm, true);
+        }
+        
+        // Read the immediate value
+        if (position >= Length)
+        {
+            return false;
+        }
+        
+        byte imm8 = CodeBuffer[position];
+        Decoder.SetPosition(position + 1);
+        
+        // Set the operands
+        instruction.Operands = $"{destOperand}, 0x{imm8:X2}";
+        
+        return true;
+    }
+    
+    /// <summary>
+    /// Gets the 8-bit register name for the given register index
+    /// </summary>
+    /// <param name="reg">The register index</param>
+    /// <returns>The register name</returns>
+    private static new string GetRegister8(byte reg)
+    {
+        string[] registerNames = { "al", "cl", "dl", "bl", "ah", "ch", "dh", "bh" };
+        return registerNames[reg & 0x07];
+    }
+}

X86Disassembler/X86/Handlers/InstructionHandlerFactory.cs

@@ -41,6 +41,7 @@ public class InstructionHandlerFactory
         _handlers.Add(new JmpRel8Handler(_codeBuffer, _decoder, _length));
         _handlers.Add(new CallRel32Handler(_codeBuffer, _decoder, _length));
         _handlers.Add(new XorRegMemHandler(_codeBuffer, _decoder, _length));
+        _handlers.Add(new TestRegMem8Handler(_codeBuffer, _decoder, _length));
         _handlers.Add(new TestRegMemHandler(_codeBuffer, _decoder, _length));
         _handlers.Add(new TestAlImmHandler(_codeBuffer, _decoder, _length));
         _handlers.Add(new TestEaxImmHandler(_codeBuffer, _decoder, _length));
@@ -104,8 +105,9 @@ public class InstructionHandlerFactory
     /// </summary>
     private void RegisterGroup3Handlers()
     {
-        // TEST handler
+        // TEST handlers
         _handlers.Add(new TestImmWithRm32Handler(_codeBuffer, _decoder, _length));
+        _handlers.Add(new TestImmWithRm8Handler(_codeBuffer, _decoder, _length));
         
         // NOT handler
         _handlers.Add(new NotRm32Handler(_codeBuffer, _decoder, _length));

X86Disassembler/X86/Handlers/TestRegMem8Handler.cs

@@ -0,0 +1,82 @@
+namespace X86Disassembler.X86.Handlers;
+
+/// <summary>
+/// Handler for TEST r/m8, r8 instruction (0x84)
+/// </summary>
+public class TestRegMem8Handler : InstructionHandler
+{
+    // ModR/M decoder
+    private readonly ModRMDecoder _modRMDecoder;
+    
+    /// <summary>
+    /// Initializes a new instance of the TestRegMem8Handler class
+    /// </summary>
+    /// <param name="codeBuffer">The buffer containing the code to decode</param>
+    /// <param name="decoder">The instruction decoder that owns this handler</param>
+    /// <param name="length">The length of the buffer</param>
+    public TestRegMem8Handler(byte[] codeBuffer, InstructionDecoder decoder, int length) 
+        : base(codeBuffer, decoder, length)
+    {
+        _modRMDecoder = new ModRMDecoder(codeBuffer, decoder, length);
+    }
+    
+    /// <summary>
+    /// Checks if this handler can decode the given opcode
+    /// </summary>
+    /// <param name="opcode">The opcode to check</param>
+    /// <returns>True if this handler can decode the opcode</returns>
+    public override bool CanHandle(byte opcode)
+    {
+        return opcode == 0x84;
+    }
+    
+    /// <summary>
+    /// Decodes a TEST r/m8, r8 instruction
+    /// </summary>
+    /// <param name="opcode">The opcode of the instruction</param>
+    /// <param name="instruction">The instruction object to populate</param>
+    /// <returns>True if the instruction was successfully decoded</returns>
+    public override bool Decode(byte opcode, Instruction instruction)
+    {
+        // Set the mnemonic
+        instruction.Mnemonic = "test";
+        
+        int position = Decoder.GetPosition();
+        
+        if (position >= Length)
+        {
+            return false;
+        }
+        
+        // Read the ModR/M byte
+        byte modRM = CodeBuffer[position++];
+        Decoder.SetPosition(position);
+        
+        // Extract the fields from the ModR/M byte
+        byte mod = (byte)((modRM & 0xC0) >> 6);
+        byte reg = (byte)((modRM & 0x38) >> 3);
+        byte rm = (byte)(modRM & 0x07);
+        
+        // Decode the destination operand
+        string destOperand = _modRMDecoder.DecodeModRM(mod, rm, true);
+        
+        // Get the source register
+        string srcReg = GetRegister8(reg);
+        
+        // Set the operands
+        instruction.Operands = $"{destOperand}, {srcReg}";
+        
+        return true;
+    }
+    
+    /// <summary>
+    /// Gets the 8-bit register name for the given register index
+    /// </summary>
+    /// <param name="reg">The register index</param>
+    /// <returns>The register name</returns>
+    private static string GetRegister8(byte reg)
+    {
+        string[] registerNames = { "al", "cl", "dl", "bl", "ah", "ch", "dh", "bh" };
+        return registerNames[reg & 0x07];
+    }
+}