#include <stdlib.h>
#include <stdio.h>

#include <sys/io.h>

int main(void)
{
	unsigned long cycles;

	if (iopl(3) < 0) {
		perror("iopl");
		return EXIT_FAILURE;
	}

	asm (	"cli			\n\t"	
		"rdtsc			\n\t"
		"movl	%%eax, %%ecx	\n\t"	
		"outb	%%al, $0x80	\n\t"
		"rdtsc			\n\t"
		"subl	%%ecx, %%eax	\n\t"
		"sti			"			

		: "=a" (cycles) : : "ecx", "edx");

	printf("out = %lu\n", cycles);

	asm (	"cli			\n\t"	
		"rdtsc			\n\t"
		"movl	%%eax, %%ecx	\n\t"	
		"inb	$0x80, %%al	\n\t"
		"rdtsc			\n\t"
		"subl	%%ecx, %%eax	\n\t"
		"sti			"			

		: "=a" (cycles) : : "ecx", "edx");

	printf("in  = %lu\n", cycles);

	return EXIT_FAILURE;
}