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/*
* 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 :-) */
static uint64_t rdtsc(void)
{
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;
static 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();
}
static 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);
}
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