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

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
   4 *
   5 * Tests if the control register is updated correctly
   6 * when set with prctl()
   7 *
   8 * Warning: this test will cause a very high load for a few seconds
   9 *
  10 */
  11
  12#include <stdio.h>
  13#include <stdlib.h>
  14#include <unistd.h>
  15#include <signal.h>
  16#include <inttypes.h>
  17#include <wait.h>
  18
  19
  20#include <sys/prctl.h>
  21#include <linux/prctl.h>
  22
  23/* Get/set the process' ability to use the timestamp counter instruction */
  24#ifndef PR_GET_TSC
  25#define PR_GET_TSC 25
  26#define PR_SET_TSC 26
  27# define PR_TSC_ENABLE          1   /* allow the use of the timestamp counter */
  28# define PR_TSC_SIGSEGV         2   /* throw a SIGSEGV instead of reading the TSC */
  29#endif
  30
  31/* snippet from wikipedia :-) */
  32
  33static uint64_t rdtsc(void)
  34{
  35uint32_t lo, hi;
  36/* We cannot use "=A", since this would use %rax on x86_64 */
  37__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  38return (uint64_t)hi << 32 | lo;
  39}
  40
  41int should_segv = 0;
  42
  43static void sigsegv_cb(int sig)
  44{
  45        if (!should_segv)
  46        {
  47                fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
  48                exit(0);
  49        }
  50        if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
  51        {
  52                perror("prctl");
  53                exit(0);
  54        }
  55        should_segv = 0;
  56
  57        rdtsc();
  58}
  59
  60static void task(void)
  61{
  62        signal(SIGSEGV, sigsegv_cb);
  63        alarm(10);
  64        for(;;)
  65        {
  66                rdtsc();
  67                if (should_segv)
  68                {
  69                        fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
  70                        exit(0);
  71                }
  72                if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
  73                {
  74                        perror("prctl");
  75                        exit(0);
  76                }
  77                should_segv = 1;
  78        }
  79}
  80
  81
  82int main(void)
  83{
  84        int n_tasks = 100, i;
  85
  86        fprintf(stderr, "[No further output means we're allright]\n");
  87
  88        for (i=0; i<n_tasks; i++)
  89                if (fork() == 0)
  90                        task();
  91
  92        for (i=0; i<n_tasks; i++)
  93                wait(NULL);
  94
  95        exit(0);
  96}
  97
  98