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 uint64_t rdtsc() {
  33 uint32_t lo, hi;
  34 /* We cannot use "=A", since this would use %rax on x86_64 */
  35 __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  36 return (uint64_t)hi << 32 | lo;
  37 }
  38
  39 void 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
  59 int 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