HijackMethod

HijackMethod

 public static void HijackMethod(MethodInfo source, MethodInfo target)
    {
      RuntimeHelpers.PrepareMethod(source.MethodHandle);
      RuntimeHelpers.PrepareMethod(target.MethodHandle);

      var sourceAddress = source.MethodHandle.GetFunctionPointer();
      var targetAddress = (long)target.MethodHandle.GetFunctionPointer();

      int offset = (int)(targetAddress - (long)sourceAddress - 4 - 1); // four bytes for relative address and one byte for opcode

      byte[] instruction = {
        0xE9, // Long jump relative instruction
        (byte)(offset & 0xFF),
        (byte)((offset >> 8) & 0xFF),
        (byte)((offset >> 16) & 0xFF),
        (byte)((offset >> 24) & 0xFF)
      };

      Marshal.Copy(instruction, 0, sourceAddress, instruction.Length);
    }