LXR linux/tools/testing/selftests/prctl/disable-tsc-on-off-stress-test.c

   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
  32static uint64_t rdtsc(void)
  33{
  34uint32_t lo, hi;
  35/* We cannot use "=A", since this would use %rax on x86_64 */
  36__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  37return (uint64_t)hi << 32 | lo;
  38}
  39
  40int should_segv = 0;
  41
  42static void sigsegv_cb(int sig)
  43{
  44        if (!should_segv)
  45        {
  46                fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
  47                exit(0);
  48        }
  49        if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
  50        {
  51                perror("prctl");
  52                exit(0);
  53        }
  54        should_segv = 0;
  55
  56        rdtsc();
  57}
  58
  59static void task(void)
  60{
  61        signal(SIGSEGV, sigsegv_cb);
  62        alarm(10);
  63        for(;;)
  64        {
  65                rdtsc();
  66                if (should_segv)
  67                {
  68                        fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
  69                        exit(0);
  70                }
  71                if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
  72                {
  73                        perror("prctl");
  74                        exit(0);
  75                }
  76                should_segv = 1;
  77        }
  78}
  79
  80
  81int main(void)
  82{
  83        int n_tasks = 100, i;
  84
  85        fprintf(stderr, "[No further output means we're allright]\n");
  86
  87        for (i=0; i<n_tasks; i++)
  88                if (fork() == 0)
  89                        task();
  90
  91        for (i=0; i<n_tasks; i++)
  92                wait(NULL);
  93
  94        exit(0);
  95}
  96
  97