内联汇编，SEHException

Question

I have created a .dll file in cpp to access the I/O ports and write to them.For this purpose I am calling this .dll from my c# console application but when try to run it, I get "SEHException was unhandled" exception. Do you have any idea?

this is c#:

[DllImport("testlib.dll")]
public static extern void enableWatchDog();

static void Main(string[] args)
{
    enableWatchDog();
}

this is cpp (which creates .dll):

extern "C" __declspec(dllexport) void enableWatchDog() { 
   _asm {
      mov al, 41
      out 66, al
      mov al, 4
      out 62, al
   }
}   

Answer 1

You cannot access arbitrary I/O ports directly from user mode applications in Windows. You need to use a special kernel mode driver for that.