From e134452edab0c0fdcac6e46f77ee323cbffefcb2 Mon Sep 17 00:00:00 2001
From: bird_egop <sampletext32@bk.ru>
Date: Mon, 14 Apr 2025 00:33:39 +0300
Subject: [PATCH] Improved PUSH handlers by moving reg field check to CanHandle
 and adding proper boundary checking

---
 .../X86/Handlers/Push/PushImm32Handler.cs     | 13 +++++--
 .../X86/Handlers/Push/PushImm8Handler.cs      |  5 +++
 .../X86/Handlers/Push/PushRm32Handler.cs      | 38 ++++++++++++-------
 3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/X86Disassembler/X86/Handlers/Push/PushImm32Handler.cs b/X86Disassembler/X86/Handlers/Push/PushImm32Handler.cs
index ebf98b4..26937af 100644
--- a/X86Disassembler/X86/Handlers/Push/PushImm32Handler.cs
+++ b/X86Disassembler/X86/Handlers/Push/PushImm32Handler.cs
@@ -11,11 +11,11 @@ public class PushImm32Handler : InstructionHandler
     /// <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 PushImm32Handler(byte[] codeBuffer, InstructionDecoder decoder, int length)
+    public PushImm32Handler(byte[] codeBuffer, InstructionDecoder decoder, int length) 
         : base(codeBuffer, decoder, length)
     {
     }
-
+    
     /// <summary>
     /// Checks if this handler can decode the given opcode
     /// </summary>
@@ -25,7 +25,7 @@ public class PushImm32Handler : InstructionHandler
     {
         return opcode == 0x68;
     }
-
+    
     /// <summary>
     /// Decodes a PUSH imm32 instruction
     /// </summary>
@@ -37,9 +37,14 @@ public class PushImm32Handler : InstructionHandler
         // Set the mnemonic
         instruction.Mnemonic = "push";
 
+        if(!Decoder.CanReadUInt())
+        {
+            return false;
+        }
+
         // Read the immediate value
         uint imm32 = Decoder.ReadUInt32();
-
+        
         // Set the operands with 8-digit padding to match test expectations
         instruction.Operands = $"0x{imm32:X8}";
 
diff --git a/X86Disassembler/X86/Handlers/Push/PushImm8Handler.cs b/X86Disassembler/X86/Handlers/Push/PushImm8Handler.cs
index 5057fd1..cfbd679 100644
--- a/X86Disassembler/X86/Handlers/Push/PushImm8Handler.cs
+++ b/X86Disassembler/X86/Handlers/Push/PushImm8Handler.cs
@@ -37,6 +37,11 @@ public class PushImm8Handler : InstructionHandler
         // Set the mnemonic
         instruction.Mnemonic = "push";
 
+        if(!Decoder.CanReadByte())
+        {
+            return false;
+        }
+
         // Read the immediate value
         byte imm8 = Decoder.ReadByte();
 
diff --git a/X86Disassembler/X86/Handlers/Push/PushRm32Handler.cs b/X86Disassembler/X86/Handlers/Push/PushRm32Handler.cs
index 70fe020..7e63cbe 100644
--- a/X86Disassembler/X86/Handlers/Push/PushRm32Handler.cs
+++ b/X86Disassembler/X86/Handlers/Push/PushRm32Handler.cs
@@ -23,7 +23,26 @@ public class PushRm32Handler : InstructionHandler
     /// <returns>True if this handler can decode the opcode</returns>
     public override bool CanHandle(byte opcode)
     {
-        return opcode == 0xFF;
+        // PUSH r/m32 is encoded as FF /6
+        if (opcode != 0xFF)
+        {
+            return false;
+        }
+        
+        // Check if we have enough bytes to read the ModR/M byte
+        if (!Decoder.CanReadByte())
+        {
+            return false;
+        }
+        
+        // Peek at the ModR/M byte without advancing the position
+        byte modRM = CodeBuffer[Decoder.GetPosition()];
+        
+        // Extract the reg field (bits 3-5)
+        byte reg = (byte)((modRM & 0x38) >> 3);
+        
+        // PUSH r/m32 is encoded as FF /6 (reg field = 6)
+        return reg == 6;
     }
 
     /// <summary>
@@ -34,9 +53,11 @@ public class PushRm32Handler : InstructionHandler
     /// <returns>True if the instruction was successfully decoded</returns>
     public override bool Decode(byte opcode, Instruction instruction)
     {
-        int position = Decoder.GetPosition();
-
-        if (position >= Length)
+        // Set the mnemonic
+        instruction.Mnemonic = "push";
+        
+        // Check if we have enough bytes for the ModR/M byte
+        if (!Decoder.CanReadByte())
         {
             return false;
         }
@@ -44,15 +65,6 @@ public class PushRm32Handler : InstructionHandler
         // Read the ModR/M byte
         var (mod, reg, rm, destOperand) = ModRMDecoder.ReadModRM();
 
-        // PUSH r/m32 is encoded as FF /6
-        if (reg != RegisterIndex.Sp)
-        {
-            return false;
-        }
-
-        // Set the mnemonic
-        instruction.Mnemonic = "push";
-
         // For memory operands, set the operand
         if (mod != 3) // Memory operand
         {