Based on kernel version 4.8. Page generated on 2016-10-06 23:18 EST.
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(void) 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 }