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