benchmarking

time-syscall.c (text/x-c), 2.38 KB, created by Anthony Basile on 2014-11-16 20:48:37 UTC

/* Compile with `gcc -fno-stack-protector -m32 -O1 -o time-syscall time-syscall.c` */ 

#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <syscall.h>
#include <time.h>

pid_t getpid_int80() {
        register unsigned int ret=__NR_getpid;
        asm volatile (
                "int $0x80\n\t"
                : "+&a" (ret)
                : 
                : "memory", "cc"
        );
        return (pid_t)ret;
}

pid_t getpid_vsyscall() {
        register unsigned int ret = __NR_getpid;
        asm volatile (
                "call *%%gs:0x10\n\t"
                : "+&a" (ret)
                : 
                : "memory", "cc"
        );
        return (pid_t)ret;
}


static void * got_vsyscall;
void init_got() {
        asm volatile (
                "movl %%gs:0x10, %0\n\t"
                : "=r" (got_vsyscall)
                : 
                : "memory", "cc"
        );
}

pid_t getpid_vsyscall_got() {
        register unsigned int ret = __NR_getpid;
        asm volatile (
                "call *%1"
                : "+&a" (ret)
                : "m" (got_vsyscall)
                : "memory", "cc"
        );
        return (pid_t)ret;
}

#define LOOPS 100000000

int main( int argc, char* argv[] ) {
	pid_t p, q, r, s;
	int i;
	clock_t before, after;

	before = clock();
	for (i = 0; i < LOOPS; i++)
		p = getpid_int80();
	after = clock();
	printf("time-int80 = %lf\n", (double)(after-before)/(double)CLOCKS_PER_SEC);

	before = clock();
	for (i = 0; i < LOOPS; i++)
		q = getpid_vsyscall();
	after = clock();
	printf("time-vsyscall = %lf\n", (double)(after-before)/(double)CLOCKS_PER_SEC);

	init_got();
	before = clock();
	for (i = 0; i < LOOPS; i++)
		r = getpid_vsyscall_got();
	after = clock();
	printf("time-got = %lf\n", (double)(after-before)/(double)CLOCKS_PER_SEC);

	before = clock();
	for (i = 0; i < LOOPS; i++)
		s = getpid();
	after = clock();
	printf("time-libc = %lf\n", (double)(after-before)/(double)CLOCKS_PER_SEC);

	printf("pid_int80 = %ld, pid_vsyscal = %ld, pid_got = %ld, pid_libc = %ld\n", (long)p, (long)q, (long)r, (long)s);

}

/*
pid_t getpid_int80() {
	register unsigned int ret;
	asm volatile (
		"int $0x80\n\t"
		: "=a" (ret)
		: "a" (__NR_getpid)
		: "memory", "cc"
	);
	return (pid_t)ret;
}

static unsigned int temp;
pid_t getpid_vsyscall() {
	asm volatile (
		"movl $20, %eax\n\t"
		"call *%gs:0x10\n\t"
		"movl %eax, temp\n\t"
	);
	return (pid_t)temp;
}
*/