1 // SPDX-License-Identifier: GPL-2.0
3 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
5 * Tests if the control register is updated correctly
6 * when set with prctl()
8 * Warning: this test will cause a very high load for a few seconds
20 #include <sys/prctl.h>
21 #include <linux/prctl.h>
23 /* Get/set the process' ability to use the timestamp counter instruction */
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 */
31 /* snippet from wikipedia :-) */
33 static uint64_t rdtsc(void)
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;
43 static void sigsegv_cb(int sig)
47 fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
50 if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
60 static void task(void)
62 signal(SIGSEGV, sigsegv_cb);
69 fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
72 if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
86 fprintf(stderr, "[No further output means we're allright]\n");
88 for (i=0; i<n_tasks; i++)
92 for (i=0; i<n_tasks; i++)