selftests/prctl/disable-tsc-ctxt-sw-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  * at context switches
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 static uint64_t rdtsc(void)
0032 {
0033 uint32_t lo, hi;
0034 /* We cannot use "=A", since this would use %rax on x86_64 */
0035 __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
0036 return (uint64_t)hi << 32 | lo;
0037 }
0038
0039 static void sigsegv_expect(int sig)
0040 {
0041     /* */
0042 }
0043
0044 static void segvtask(void)
0045 {
0046     if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
0047     {
0048         perror("prctl");
0049         exit(0);
0050     }
0051     signal(SIGSEGV, sigsegv_expect);
0052     alarm(10);
0053     rdtsc();
0054     fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
0055     exit(0);
0056 }
0057
0058
0059 static void sigsegv_fail(int sig)
0060 {
0061     fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
0062     exit(0);
0063 }
0064
0065 static void rdtsctask(void)
0066 {
0067     if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
0068     {
0069         perror("prctl");
0070         exit(0);
0071     }
0072     signal(SIGSEGV, sigsegv_fail);
0073     alarm(10);
0074     for(;;) rdtsc();
0075 }
0076
0077
0078 int main(void)
0079 {
0080     int n_tasks = 100, i;
0081
0082     fprintf(stderr, "[No further output means we're allright]\n");
0083
0084     for (i=0; i<n_tasks; i++)
0085         if (fork() == 0)
0086         {
0087             if (i & 1)
0088                 segvtask();
0089             else
0090                 rdtsctask();
0091         }
0092
0093     for (i=0; i<n_tasks; i++)
0094         wait(NULL);
0095
0096     exit(0);
0097 }
0098