Documentation/prctl/disable-tsc-test.c

   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
  25 const char *tsc_names[] =
  26 {
  27         [0] = "[not set]",
  28         [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
  29         [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
  30 };
  31
  32 static uint64_t rdtsc(void)
  33 {
  34 uint32_t lo, hi;
  35 /* We cannot use "=A", since this would use %rax on x86_64 */
  36 __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  37 return (uint64_t)hi << 32 | lo;
  38 }
  39
  40 static void sigsegv_cb(int sig)
  41 {
  42         int tsc_val = 0;
  43
  44         printf("[ SIG_SEGV ]\n");
  45         printf("prctl(PR_GET_TSC, &tsc_val); ");
  46         fflush(stdout);
  47
  48         if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  49                 perror("prctl");
  50
  51         printf("tsc_val == %s\n", tsc_names[tsc_val]);
  52         printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
  53         fflush(stdout);
  54         if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  55                 perror("prctl");
  56
  57         printf("rdtsc() == ");
  58 }
  59
  60 int main(int argc, char **argv)
  61 {
  62         int tsc_val = 0;
  63
  64         signal(SIGSEGV, sigsegv_cb);
  65
  66         printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  67         printf("prctl(PR_GET_TSC, &tsc_val); ");
  68         fflush(stdout);
  69
  70         if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  71                 perror("prctl");
  72
  73         printf("tsc_val == %s\n", tsc_names[tsc_val]);
  74         printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  75         printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
  76         fflush(stdout);
  77
  78         if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  79                 perror("prctl");
  80
  81         printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
  82         printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
  83         fflush(stdout);
  84
  85         if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
  86                 perror("prctl");
  87
  88         printf("rdtsc() == ");
  89         fflush(stdout);
  90         printf("%llu\n", (unsigned long long)rdtsc());
  91         fflush(stdout);
  92
  93         exit(EXIT_SUCCESS);
  94 }
  95