Commit | Line | Data |
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f1326973 EB |
1 | /* |
2 | * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...) | |
3 | * | |
4 | * Tests if the control register is updated correctly | |
5 | * when set with prctl() | |
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 | ||
30 | /* snippet from wikipedia :-) */ | |
31 | ||
32 | uint64_t rdtsc() { | |
33 | uint32_t lo, hi; | |
34 | /* We cannot use "=A", since this would use %rax on x86_64 */ | |
35 | __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); | |
36 | return (uint64_t)hi << 32 | lo; | |
37 | } | |
38 | ||
39 | int should_segv = 0; | |
40 | ||
41 | void sigsegv_cb(int sig) | |
42 | { | |
43 | if (!should_segv) | |
44 | { | |
45 | fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n"); | |
46 | exit(0); | |
47 | } | |
48 | if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) | |
49 | { | |
50 | perror("prctl"); | |
51 | exit(0); | |
52 | } | |
53 | should_segv = 0; | |
54 | ||
55 | rdtsc(); | |
56 | } | |
57 | ||
58 | void task(void) | |
59 | { | |
60 | signal(SIGSEGV, sigsegv_cb); | |
61 | alarm(10); | |
62 | for(;;) | |
63 | { | |
64 | rdtsc(); | |
65 | if (should_segv) | |
66 | { | |
67 | fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n"); | |
68 | exit(0); | |
69 | } | |
70 | if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) | |
71 | { | |
72 | perror("prctl"); | |
73 | exit(0); | |
74 | } | |
75 | should_segv = 1; | |
76 | } | |
77 | } | |
78 | ||
79 | ||
80 | int main(int argc, char **argv) | |
81 | { | |
82 | int n_tasks = 100, i; | |
83 | ||
84 | fprintf(stderr, "[No further output means we're allright]\n"); | |
85 | ||
86 | for (i=0; i<n_tasks; i++) | |
87 | if (fork() == 0) | |
88 | task(); | |
89 | ||
90 | for (i=0; i<n_tasks; i++) | |
91 | wait(NULL); | |
92 | ||
93 | exit(0); | |
94 | } | |
95 |