selftests/prctl/disable-tsc-on-off-stress-test.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
0004  *
0005  * Tests if the control register is updated correctly
0006  * when set with prctl()
0007  *
0008  * Warning: this test will cause a very high load for a few seconds
0009  *
0010  */
0011
0012 #include <stdio.h>
0013 #include <stdlib.h>
0014 #include <unistd.h>
0015 #include <signal.h>
0016 #include <inttypes.h>
0017 #include <wait.h>
0018
0019
0020 #include <sys/prctl.h>
0021 #include <linux/prctl.h>
0022
0023 /* Get/set the process' ability to use the timestamp counter instruction */
0024 #ifndef PR_GET_TSC
0025 #define PR_GET_TSC 25
0026 #define PR_SET_TSC 26
0027 # define PR_TSC_ENABLE      1   /* allow the use of the timestamp counter */
0028 # define PR_TSC_SIGSEGV     2   /* throw a SIGSEGV instead of reading the TSC */
0029 #endif
0030
0031 /* snippet from wikipedia :-) */
0032
0033 static uint64_t rdtsc(void)
0034 {
0035 uint32_t lo, hi;
0036 /* We cannot use "=A", since this would use %rax on x86_64 */
0037 __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
0038 return (uint64_t)hi << 32 | lo;
0039 }
0040
0041 int should_segv = 0;
0042
0043 static void sigsegv_cb(int sig)
0044 {
0045     if (!should_segv)
0046     {
0047         fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
0048         exit(0);
0049     }
0050     if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
0051     {
0052         perror("prctl");
0053         exit(0);
0054     }
0055     should_segv = 0;
0056
0057     rdtsc();
0058 }
0059
0060 static void task(void)
0061 {
0062     signal(SIGSEGV, sigsegv_cb);
0063     alarm(10);
0064     for(;;)
0065     {
0066         rdtsc();
0067         if (should_segv)
0068         {
0069             fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
0070             exit(0);
0071         }
0072         if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
0073         {
0074             perror("prctl");
0075             exit(0);
0076         }
0077         should_segv = 1;
0078     }
0079 }
0080
0081
0082 int main(void)
0083 {
0084     int n_tasks = 100, i;
0085
0086     fprintf(stderr, "[No further output means we're allright]\n");
0087
0088     for (i=0; i<n_tasks; i++)
0089         if (fork() == 0)
0090             task();
0091
0092     for (i=0; i<n_tasks; i++)
0093         wait(NULL);
0094
0095     exit(0);
0096 }
0097