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 * at context switches
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
rdtsc(void)31*4882a593Smuzhiyun static uint64_t rdtsc(void)
32*4882a593Smuzhiyun {
33*4882a593Smuzhiyun uint32_t lo, hi;
34*4882a593Smuzhiyun /* We cannot use "=A", since this would use %rax on x86_64 */
35*4882a593Smuzhiyun __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
36*4882a593Smuzhiyun return (uint64_t)hi << 32 | lo;
37*4882a593Smuzhiyun }
38*4882a593Smuzhiyun
sigsegv_expect(int sig)39*4882a593Smuzhiyun static void sigsegv_expect(int sig)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun /* */
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun
segvtask(void)44*4882a593Smuzhiyun static void segvtask(void)
45*4882a593Smuzhiyun {
46*4882a593Smuzhiyun if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
47*4882a593Smuzhiyun {
48*4882a593Smuzhiyun perror("prctl");
49*4882a593Smuzhiyun exit(0);
50*4882a593Smuzhiyun }
51*4882a593Smuzhiyun signal(SIGSEGV, sigsegv_expect);
52*4882a593Smuzhiyun alarm(10);
53*4882a593Smuzhiyun rdtsc();
54*4882a593Smuzhiyun fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
55*4882a593Smuzhiyun exit(0);
56*4882a593Smuzhiyun }
57*4882a593Smuzhiyun
58*4882a593Smuzhiyun
sigsegv_fail(int sig)59*4882a593Smuzhiyun static void sigsegv_fail(int sig)
60*4882a593Smuzhiyun {
61*4882a593Smuzhiyun fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
62*4882a593Smuzhiyun exit(0);
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun
rdtsctask(void)65*4882a593Smuzhiyun static void rdtsctask(void)
66*4882a593Smuzhiyun {
67*4882a593Smuzhiyun if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
68*4882a593Smuzhiyun {
69*4882a593Smuzhiyun perror("prctl");
70*4882a593Smuzhiyun exit(0);
71*4882a593Smuzhiyun }
72*4882a593Smuzhiyun signal(SIGSEGV, sigsegv_fail);
73*4882a593Smuzhiyun alarm(10);
74*4882a593Smuzhiyun for(;;) rdtsc();
75*4882a593Smuzhiyun }
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun
main(void)78*4882a593Smuzhiyun int main(void)
79*4882a593Smuzhiyun {
80*4882a593Smuzhiyun int n_tasks = 100, i;
81*4882a593Smuzhiyun
82*4882a593Smuzhiyun fprintf(stderr, "[No further output means we're allright]\n");
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun for (i=0; i<n_tasks; i++)
85*4882a593Smuzhiyun if (fork() == 0)
86*4882a593Smuzhiyun {
87*4882a593Smuzhiyun if (i & 1)
88*4882a593Smuzhiyun segvtask();
89*4882a593Smuzhiyun else
90*4882a593Smuzhiyun rdtsctask();
91*4882a593Smuzhiyun }
92*4882a593Smuzhiyun
93*4882a593Smuzhiyun for (i=0; i<n_tasks; i++)
94*4882a593Smuzhiyun wait(NULL);
95*4882a593Smuzhiyun
96*4882a593Smuzhiyun exit(0);
97*4882a593Smuzhiyun }
98*4882a593Smuzhiyun
99