[net-next-2.6.git] / Documentation / prctl / disable-tsc-on-off-stress-test.c

/*
 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
 *
 * Tests if the control register is updated correctly
 * when set with prctl()
 *
 * Warning: this test will cause a very high load for a few seconds
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <inttypes.h>
#include <wait.h>


#include <sys/prctl.h>
#include <linux/prctl.h>

/* Get/set the process' ability to use the timestamp counter instruction */
#ifndef PR_GET_TSC
#define PR_GET_TSC 25
#define PR_SET_TSC 26
# define PR_TSC_ENABLE		1   /* allow the use of the timestamp counter */
# define PR_TSC_SIGSEGV		2   /* throw a SIGSEGV instead of reading the TSC */
#endif

/* snippet from wikipedia :-) */

uint64_t rdtsc() {
uint32_t lo, hi;
/* We cannot use "=A", since this would use %rax on x86_64 */
__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
return (uint64_t)hi << 32 | lo;
}

int should_segv = 0;

void sigsegv_cb(int sig)
{
	if (!should_segv)
	{
		fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
		exit(0);
	}
	if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
	{
		perror("prctl");
		exit(0);
	}
	should_segv = 0;

	rdtsc();
}

void task(void)
{
	signal(SIGSEGV, sigsegv_cb);
	alarm(10);
	for(;;)
	{
		rdtsc();
		if (should_segv)
		{
			fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
			exit(0);
		}
		if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
		{
			perror("prctl");
			exit(0);
		}
		should_segv = 1;
	}
}


int main(int argc, char **argv)
{
	int n_tasks = 100, i;

	fprintf(stderr, "[No further output means we're allright]\n");

	for (i=0; i<n_tasks; i++)
		if (fork() == 0)
			task();

	for (i=0; i<n_tasks; i++)
		wait(NULL);

	exit(0);
}
Commit	Line	Data
f1326973 EB	1	/*
	2	* Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
	3	*
	4	* Tests if the control register is updated correctly
	5	* when set with prctl()
	6	*
	7	* Warning: this test will cause a very high load for a few seconds
	8	*
	9	*/
	10
	11	#include <stdio.h>
	12	#include <stdlib.h>
	13	#include <unistd.h>
	14	#include <signal.h>
	15	#include <inttypes.h>
	16	#include <wait.h>
	17
	18
	19	#include <sys/prctl.h>
	20	#include <linux/prctl.h>
	21
	22	/* Get/set the process' ability to use the timestamp counter instruction */
	23	#ifndef PR_GET_TSC
	24	#define PR_GET_TSC 25
	25	#define PR_SET_TSC 26
	26	# define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
	27	# define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
	28	#endif
	29
	30	/* snippet from wikipedia :-) */
	31
	32	uint64_t rdtsc() {
	33	uint32_t lo, hi;
	34	/* We cannot use "=A", since this would use %rax on x86_64 */
	35	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
	36	return (uint64_t)hi << 32 \| lo;
	37	}
	38
	39	int should_segv = 0;
	40
	41	void sigsegv_cb(int sig)
	42	{
	43	if (!should_segv)
	44	{
	45	fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
	46	exit(0);
	47	}
	48	if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
	49	{
	50	perror("prctl");
	51	exit(0);
	52	}
	53	should_segv = 0;
	54
	55	rdtsc();
	56	}
	57
	58	void task(void)
	59	{
	60	signal(SIGSEGV, sigsegv_cb);
	61	alarm(10);
	62	for(;;)
	63	{
	64	rdtsc();
65	if (should_segv)
66	{
67	fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
68	exit(0);
69	}
70	if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
71	{
72	perror("prctl");
73	exit(0);
74	}
75	should_segv = 1;
76	}
77	}
78
79
80	int main(int argc, char **argv)
81	{
82	int n_tasks = 100, i;
83
84	fprintf(stderr, "[No further output means we're allright]\n");
85
86	for (i=0; i<n_tasks; i++)
87	if (fork() == 0)
88	task();
89
90	for (i=0; i<n_tasks; i++)
91	wait(NULL);
92
93	exit(0);
94	}
95