//-------------------------------------------------------------------
//	openuhci.cpp
//
//	This program will demonstrate the 'side-effect' that opening
//	our '/dev/uhci' device-file has upon a process's IOPL value.
//
//		to compile:  $ g++ openuhci.cpp -o openuhci
//		to execute:  $ ./openuhci
//
//	NOTES: Prior installation of a companion module is required.
//	Conditional compilation accommodates both x86 architectures.
//
//	programmer: ALLAN CRUSE
//	written on: 19 MAR 2010
//-------------------------------------------------------------------

#include <stdio.h>		// for printf(), perror() 
#include <fcntl.h>		// for open() 
#include <stdlib.h>		// for exit() 

char devname[] = "/dev/uhci";	// name of the device-file
unsigned long	flags_reg;	// declare global variable 

int main( int argc, char **argv )
{
	// transfer flags-register's value to memory-variable
#ifdef __i386__
	asm(" pushfl \n popl flags_reg ");
#else	
	asm(" pushfq \n popq flags_reg ");
#endif
	// show the initial value of this task's IOPL
	printf( "\nBefore device-file \'%s\' has been opened: \n", devname );
	printf( "\n          FLAGS=%08lX ", flags_reg );
	printf( " IOPL=%lu \n\n", (flags_reg >> 12)&3 );

	// invoke a system-call to open the device-file
	int	fd = open( devname, O_RDWR );
	if ( fd < 0 ) { perror( devname ); exit(1); }

	// transfer flags-register's value to memory-variable
#ifdef __i386__
	asm(" pushfl \n popl flags_reg ");
#else
	asm(" pushfq \n popq flags_reg ");
#endif
	// show the resulting effect on this task's IOPL
	printf( "\nAfter device-file \'%s\' has been opened: \n", devname );
	printf( "\n          FLAGS=%08lX ", flags_reg );
	printf( " IOPL=%lu \n\n", (flags_reg >> 12)&3 );
}