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