1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Tests if the control register is updated correctly
6*4882a593Smuzhiyun * when set with prctl()
7*4882a593Smuzhiyun *
8*4882a593Smuzhiyun * Warning: this test will cause a very high load for a few seconds
9*4882a593Smuzhiyun *
10*4882a593Smuzhiyun */
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun #include <stdio.h>
13*4882a593Smuzhiyun #include <stdlib.h>
14*4882a593Smuzhiyun #include <unistd.h>
15*4882a593Smuzhiyun #include <signal.h>
16*4882a593Smuzhiyun #include <inttypes.h>
17*4882a593Smuzhiyun #include <wait.h>
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun
20*4882a593Smuzhiyun #include <sys/prctl.h>
21*4882a593Smuzhiyun #include <linux/prctl.h>
22*4882a593Smuzhiyun
23*4882a593Smuzhiyun /* Get/set the process' ability to use the timestamp counter instruction */
24*4882a593Smuzhiyun #ifndef PR_GET_TSC
25*4882a593Smuzhiyun #define PR_GET_TSC 25
26*4882a593Smuzhiyun #define PR_SET_TSC 26
27*4882a593Smuzhiyun # define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
28*4882a593Smuzhiyun # define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
29*4882a593Smuzhiyun #endif
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun /* snippet from wikipedia :-) */
32*4882a593Smuzhiyun
rdtsc(void)33*4882a593Smuzhiyun static uint64_t rdtsc(void)
34*4882a593Smuzhiyun {
35*4882a593Smuzhiyun uint32_t lo, hi;
36*4882a593Smuzhiyun /* We cannot use "=A", since this would use %rax on x86_64 */
37*4882a593Smuzhiyun __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
38*4882a593Smuzhiyun return (uint64_t)hi << 32 | lo;
39*4882a593Smuzhiyun }
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun int should_segv = 0;
42*4882a593Smuzhiyun
sigsegv_cb(int sig)43*4882a593Smuzhiyun static void sigsegv_cb(int sig)
44*4882a593Smuzhiyun {
45*4882a593Smuzhiyun if (!should_segv)
46*4882a593Smuzhiyun {
47*4882a593Smuzhiyun fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
48*4882a593Smuzhiyun exit(0);
49*4882a593Smuzhiyun }
50*4882a593Smuzhiyun if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
51*4882a593Smuzhiyun {
52*4882a593Smuzhiyun perror("prctl");
53*4882a593Smuzhiyun exit(0);
54*4882a593Smuzhiyun }
55*4882a593Smuzhiyun should_segv = 0;
56*4882a593Smuzhiyun
57*4882a593Smuzhiyun rdtsc();
58*4882a593Smuzhiyun }
59*4882a593Smuzhiyun
task(void)60*4882a593Smuzhiyun static void task(void)
61*4882a593Smuzhiyun {
62*4882a593Smuzhiyun signal(SIGSEGV, sigsegv_cb);
63*4882a593Smuzhiyun alarm(10);
64*4882a593Smuzhiyun for(;;)
65*4882a593Smuzhiyun {
66*4882a593Smuzhiyun rdtsc();
67*4882a593Smuzhiyun if (should_segv)
68*4882a593Smuzhiyun {
69*4882a593Smuzhiyun fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
70*4882a593Smuzhiyun exit(0);
71*4882a593Smuzhiyun }
72*4882a593Smuzhiyun if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
73*4882a593Smuzhiyun {
74*4882a593Smuzhiyun perror("prctl");
75*4882a593Smuzhiyun exit(0);
76*4882a593Smuzhiyun }
77*4882a593Smuzhiyun should_segv = 1;
78*4882a593Smuzhiyun }
79*4882a593Smuzhiyun }
80*4882a593Smuzhiyun
81*4882a593Smuzhiyun
main(void)82*4882a593Smuzhiyun int main(void)
83*4882a593Smuzhiyun {
84*4882a593Smuzhiyun int n_tasks = 100, i;
85*4882a593Smuzhiyun
86*4882a593Smuzhiyun fprintf(stderr, "[No further output means we're allright]\n");
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun for (i=0; i<n_tasks; i++)
89*4882a593Smuzhiyun if (fork() == 0)
90*4882a593Smuzhiyun task();
91*4882a593Smuzhiyun
92*4882a593Smuzhiyun for (i=0; i<n_tasks; i++)
93*4882a593Smuzhiyun wait(NULL);
94*4882a593Smuzhiyun
95*4882a593Smuzhiyun exit(0);
96*4882a593Smuzhiyun }
97*4882a593Smuzhiyun
98