98 lines · c
1// SPDX-License-Identifier: GPL-2.02/*3 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)4 *5 * Tests if the control register is updated correctly6 * when set with prctl()7 *8 * Warning: this test will cause a very high load for a few seconds9 *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_TSC25#define PR_GET_TSC 2526#define PR_SET_TSC 2627# 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#endif30 31/* snippet from wikipedia :-) */32 33static uint64_t rdtsc(void)34{35uint32_t lo, hi;36/* We cannot use "=A", since this would use %rax on x86_64 */37__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));38return (uint64_t)hi << 32 | lo;39}40 41int should_segv = 0;42 43static 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 60static 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 82int 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