linux/Documentation/prctl/disable-tsc-test.c
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   1/*
   2 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
   3 *
   4 * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC
   5 */
   6
   7#include <stdio.h>
   8#include <stdlib.h>
   9#include <unistd.h>
  10#include <signal.h>
  11#include <inttypes.h>
  12
  13
  14#include <sys/prctl.h>
  15#include <linux/prctl.h>
  16
  17/* Get/set the process' ability to use the timestamp counter instruction */
  18#ifndef PR_GET_TSC
  19#define PR_GET_TSC 25
  20#define PR_SET_TSC 26
  21# define PR_TSC_ENABLE          1   /* allow the use of the timestamp counter */
  22# define PR_TSC_SIGSEGV         2   /* throw a SIGSEGV instead of reading the TSC */
  23#endif
  24
  25const char *tsc_names[] =
  26{
  27        [0] = "[not set]",
  28        [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
  29        [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
  30};
  31
  32uint64_t rdtsc() {
  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
  39void sigsegv_cb(int sig)
  40{
  41        int tsc_val = 0;
  42
  43        printf("[ SIG_SEGV ]\n");
  44        printf("prctl(PR_GET_TSC, &tsc_val); ");
  45        fflush(stdout);
  46
  47        if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  48                perror("prctl");
  49
  50        printf("tsc_val == %s\n", tsc_names[tsc_val]);
  51        printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
  52        fflush(stdout);
  53        if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  54                perror("prctl");
  55
  56        printf("rdtsc() == ");
  57}
  58
  59int main(int argc, char **argv)
  60{
  61        int tsc_val = 0;
  62
  63        signal(SIGSEGV, sigsegv_cb);
  64
  65        printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  66        printf("prctl(PR_GET_TSC, &tsc_val); ");
  67        fflush(stdout);
  68
  69        if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  70                perror("prctl");
  71
  72        printf("tsc_val == %s\n", tsc_names[tsc_val]);
  73        printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  74        printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
  75        fflush(stdout);
  76
  77        if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  78                perror("prctl");
  79
  80        printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  81        printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
  82        fflush(stdout);
  83
  84        if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
  85                perror("prctl");
  86
  87        printf("rdtsc() == ");
  88        fflush(stdout);
  89        printf("%llu\n", (unsigned long long)rdtsc());
  90        fflush(stdout);
  91
  92        exit(EXIT_SUCCESS);
  93}
  94
  95
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