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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 * at context switches7 *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 31static uint64_t rdtsc(void)32{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 39static void sigsegv_expect(int sig)40{41 /* */42}43 44static void segvtask(void)45{46 if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)47 {48 perror("prctl");49 exit(0);50 }51 signal(SIGSEGV, sigsegv_expect);52 alarm(10);53 rdtsc();54 fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");55 exit(0);56}57 58 59static void sigsegv_fail(int sig)60{61 fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");62 exit(0);63}64 65static void rdtsctask(void)66{67 if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)68 {69 perror("prctl");70 exit(0);71 }72 signal(SIGSEGV, sigsegv_fail);73 alarm(10);74 for(;;) rdtsc();75}76 77 78int main(void)79{80 int n_tasks = 100, i;81 82 fprintf(stderr, "[No further output means we're all right]\n");83 84 for (i=0; i<n_tasks; i++)85 if (fork() == 0)86 {87 if (i & 1)88 segvtask();89 else90 rdtsctask();91 }92 93 for (i=0; i<n_tasks; i++)94 wait(NULL);95 96 exit(0);97}98 99