Implemented Group1 instruction handlers for CMP r/m8, imm8 and fixed OR r/m8, imm8

X86Disassembler/X86/Handlers/Group1/CmpImmWithRm8Handler.cs

@@ -0,0 +1,136 @@
+namespace X86Disassembler.X86.Handlers.Group1;
+
+/// <summary>
+/// Handler for CMP r/m8, imm8 instruction (0x80 /7)
+/// </summary>
+public class CmpImmWithRm8Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the CmpImmWithRm8Handler 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 CmpImmWithRm8Handler(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 != 0x80)
+            return false;
+            
+        // Check if the reg field of the ModR/M byte is 7 (CMP)
+        int position = Decoder.GetPosition();
+        if (position >= Length)
+            return false;
+            
+        byte modRM = CodeBuffer[position];
+        byte reg = (byte)((modRM & 0x38) >> 3);
+        
+        return reg == 7; // 7 = CMP
+    }
+
+    /// <summary>
+    /// Decodes a CMP 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)
+    {
+        int position = Decoder.GetPosition();
+
+        if (position >= Length)
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte
+        byte modRM = CodeBuffer[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);
+        
+        // CMP r/m8, imm8 is encoded as 80 /7
+        if (reg != 7)
+        {
+            return false;
+        }
+        
+        // Process SIB and displacement bytes if needed
+        if (mod != 3 && rm == 4) // SIB byte present
+        {
+            if (position >= Length)
+            {
+                return false;
+            }
+            position++; // Skip SIB byte
+        }
+        
+        // Handle displacement
+        if ((mod == 1 && position >= Length) || (mod == 2 && position + 3 >= Length))
+        {
+            return false;
+        }
+        
+        if (mod == 1) // 8-bit displacement
+        {
+            position++;
+        }
+        else if (mod == 2) // 32-bit displacement
+        {
+            position += 4;
+        }
+        
+        // Read the immediate byte
+        if (position >= Length)
+        {
+            return false;
+        }
+        
+        byte imm8 = CodeBuffer[position++];
+        Decoder.SetPosition(position);
+
+        // Set the mnemonic
+        instruction.Mnemonic = "cmp";
+
+        // Get the operand string
+        string operand;
+        if (mod != 3) // Memory operand
+        {
+            string memOperand = ModRMDecoder.DecodeModRM(mod, rm, true);
+            
+            // Replace the size prefix with "byte ptr"
+            if (memOperand.StartsWith("qword ptr "))
+            {
+                operand = memOperand.Replace("qword ptr ", "byte ptr ");
+            }
+            else if (memOperand.StartsWith("dword ptr "))
+            {
+                operand = memOperand.Replace("dword ptr ", "byte ptr ");
+            }
+            else
+            {
+                operand = $"byte ptr {memOperand}";
+            }
+        }
+        else // Register operand
+        {
+            operand = GetRegister8(rm);
+        }
+
+        // Set the operands
+        instruction.Operands = $"{operand}, 0x{imm8:X2}";
+
+        return true;
+    }
+}

X86Disassembler/X86/Handlers/Group1/OrImmWithRm8Handler.cs

@@ -0,0 +1,136 @@
+namespace X86Disassembler.X86.Handlers.Group1;
+
+/// <summary>
+/// Handler for OR r/m8, imm8 instruction (0x80 /1)
+/// </summary>
+public class OrImmWithRm8Handler : InstructionHandler
+{
+    /// <summary>
+    /// Initializes a new instance of the OrImmWithRm8Handler 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 OrImmWithRm8Handler(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 != 0x80)
+            return false;
+            
+        // Check if the reg field of the ModR/M byte is 1 (OR)
+        int position = Decoder.GetPosition();
+        if (position >= Length)
+            return false;
+            
+        byte modRM = CodeBuffer[position];
+        byte reg = (byte)((modRM & 0x38) >> 3);
+        
+        return reg == 1; // 1 = OR
+    }
+
+    /// <summary>
+    /// Decodes an OR 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)
+    {
+        int position = Decoder.GetPosition();
+
+        if (position >= Length)
+        {
+            return false;
+        }
+
+        // Read the ModR/M byte
+        byte modRM = CodeBuffer[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);
+        
+        // OR r/m8, imm8 is encoded as 80 /1
+        if (reg != 1)
+        {
+            return false;
+        }
+        
+        // Process SIB and displacement bytes if needed
+        if (mod != 3 && rm == 4) // SIB byte present
+        {
+            if (position >= Length)
+            {
+                return false;
+            }
+            position++; // Skip SIB byte
+        }
+        
+        // Handle displacement
+        if ((mod == 1 && position >= Length) || (mod == 2 && position + 3 >= Length))
+        {
+            return false;
+        }
+        
+        if (mod == 1) // 8-bit displacement
+        {
+            position++;
+        }
+        else if (mod == 2) // 32-bit displacement
+        {
+            position += 4;
+        }
+        
+        // Read the immediate byte
+        if (position >= Length)
+        {
+            return false;
+        }
+        
+        byte imm8 = CodeBuffer[position++];
+        Decoder.SetPosition(position);
+
+        // Set the mnemonic
+        instruction.Mnemonic = "or";
+
+        // Get the operand string
+        string operand;
+        if (mod != 3) // Memory operand
+        {
+            string memOperand = ModRMDecoder.DecodeModRM(mod, rm, true);
+            
+            // Replace the size prefix with "byte ptr"
+            if (memOperand.StartsWith("qword ptr "))
+            {
+                operand = memOperand.Replace("qword ptr ", "byte ptr ");
+            }
+            else if (memOperand.StartsWith("dword ptr "))
+            {
+                operand = memOperand.Replace("dword ptr ", "byte ptr ");
+            }
+            else
+            {
+                operand = $"byte ptr {memOperand}";
+            }
+        }
+        else // Register operand
+        {
+            operand = GetRegister8(rm);
+        }
+
+        // Set the operands
+        instruction.Operands = $"{operand}, 0x{imm8:X2}";
+
+        return true;
+    }
+}

X86Disassembler/X86/OpcodeMap.cs

@@ -91,9 +91,9 @@ public static class OpcodeMap
         OneByteOpcodes[0x05] = "add"; // ADD EAX, imm32
         
         // Group 1 instructions (ADD, OR, ADC, SBB, AND, SUB, XOR, CMP)
-        OneByteOpcodes[0x80] = "group1b";
+        OneByteOpcodes[0x80] = "group1b"; // Group 1 8-bit operations with immediate 8-bit
-        OneByteOpcodes[0x81] = "group1d";
+        OneByteOpcodes[0x81] = "group1d"; // Group 1 32-bit operations with immediate 32-bit
-        OneByteOpcodes[0x83] = "group1s"; // Sign-extended immediate
+        OneByteOpcodes[0x83] = "group1ds"; // Group 1 32-bit operations with immediate 8-bit sign-extended
         
         // Group 3 instructions (TEST, NOT, NEG, MUL, IMUL, DIV, IDIV)
         OneByteOpcodes[0xF6] = "group3b"; // 8-bit operations