1/* 2 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...) 3 * 4 * Tests if the control register is updated correctly 5 * when set with prctl() 6 * 7 * Warning: this test will cause a very high load for a few seconds 8 * 9 */ 10 11#include <stdio.h> 12#include <stdlib.h> 13#include <unistd.h> 14#include <signal.h> 15#include <inttypes.h> 16#include <wait.h> 17 18 19#include <sys/prctl.h> 20#include <linux/prctl.h> 21 22/* Get/set the process' ability to use the timestamp counter instruction */ 23#ifndef PR_GET_TSC 24#define PR_GET_TSC 25 25#define PR_SET_TSC 26 26# define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */ 27# define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */ 28#endif 29 30/* snippet from wikipedia :-) */ 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 39int should_segv = 0; 40 41void sigsegv_cb(int sig) 42{ 43 if (!should_segv) 44 { 45 fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n"); 46 exit(0); 47 } 48 if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) 49 { 50 perror("prctl"); 51 exit(0); 52 } 53 should_segv = 0; 54 55 rdtsc(); 56} 57 58void task(void) 59{ 60 signal(SIGSEGV, sigsegv_cb); 61 alarm(10); 62 for(;;) 63 { 64 rdtsc(); 65 if (should_segv) 66 { 67 fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n"); 68 exit(0); 69 } 70 if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) 71 { 72 perror("prctl"); 73 exit(0); 74 } 75 should_segv = 1; 76 } 77} 78 79 80int main(int argc, char **argv) 81{ 82 int n_tasks = 100, i; 83 84 fprintf(stderr, "[No further output means we're allright]\n"); 85 86 for (i=0; i<n_tasks; i++) 87 if (fork() == 0) 88 task(); 89 90 for (i=0; i<n_tasks; i++) 91 wait(NULL); 92 93 exit(0); 94} 95