LXR linux/tools/testing/selftests/prctl/disable-tsc-ctxt-sw-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 * at context switches
   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
  31static uint64_t rdtsc(void)
  32{
  33uint32_t lo, hi;
  34/* We cannot use "=A", since this would use %rax on x86_64 */
  35__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  36return (uint64_t)hi << 32 | lo;
  37}
  38
  39static void sigsegv_expect(int sig)
  40{
  41        /* */
  42}
  43
  44static void segvtask(void)
  45{
  46        if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
  47        {
  48                perror("prctl");
  49                exit(0);
  50        }
  51        signal(SIGSEGV, sigsegv_expect);
  52        alarm(10);
  53        rdtsc();
  54        fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
  55        exit(0);
  56}
  57
  58
  59static void sigsegv_fail(int sig)
  60{
  61        fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
  62        exit(0);
  63}
  64
  65static void rdtsctask(void)
  66{
  67        if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
  68        {
  69                perror("prctl");
  70                exit(0);
  71        }
  72        signal(SIGSEGV, sigsegv_fail);
  73        alarm(10);
  74        for(;;) rdtsc();
  75}
  76
  77
  78int main(void)
  79{
  80        int n_tasks = 100, i;
  81
  82        fprintf(stderr, "[No further output means we're allright]\n");
  83
  84        for (i=0; i<n_tasks; i++)
  85                if (fork() == 0)
  86                {
  87                        if (i & 1)
  88                                segvtask();
  89                        else
  90                                rdtsctask();
  91                }
  92
  93        for (i=0; i<n_tasks; i++)
  94                wait(NULL);
  95
  96        exit(0);
  97}
  98
  99