#include <stdio.h>

int main() 
{ 
	unsigned int regr;
	unsigned int a, b;
	unsigned int avg;
	asm volatile("mrc p15, 0, %0, c9, c14, 0" : "=r" (regr));
	printf("regr: %x\n", regr);

	for (regr = 0; regr < 100; regr++) {
		asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (a));
		asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (b));
		regr += (b - a);
	}

	regr /= 100;
	printf("Measurement overhead: %u\n", regr);
	regr = 0;
	while (regr < 100)	{
	asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (a));
	fork();
	asm volatile("mrc p15, 0, %0, c9, c13, 0" : "=r" (b));
	printf("Time for fork: %u\n", b - a);
	avg += (b - a);
	regr++;
	}

	printf("Fork avg: %u\n", avg);
	return 1; 
}