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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 | ||
0421fc83 PF |
32 | static uint64_t rdtsc(void) |
33 | { | |
f1326973 EB |
34 | uint32_t lo, hi; |
35 | /* We cannot use "=A", since this would use %rax on x86_64 */ | |
36 | __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); | |
37 | return (uint64_t)hi << 32 | lo; | |
38 | } | |
39 | ||
40 | int should_segv = 0; | |
41 | ||
0421fc83 | 42 | static void sigsegv_cb(int sig) |
f1326973 EB |
43 | { |
44 | if (!should_segv) | |
45 | { | |
46 | fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n"); | |
47 | exit(0); | |
48 | } | |
49 | if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) | |
50 | { | |
51 | perror("prctl"); | |
52 | exit(0); | |
53 | } | |
54 | should_segv = 0; | |
55 | ||
56 | rdtsc(); | |
57 | } | |
58 | ||
0421fc83 | 59 | static void task(void) |
f1326973 EB |
60 | { |
61 | signal(SIGSEGV, sigsegv_cb); | |
62 | alarm(10); | |
63 | for(;;) | |
64 | { | |
65 | rdtsc(); | |
66 | if (should_segv) | |
67 | { | |
68 | fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n"); | |
69 | exit(0); | |
70 | } | |
71 | if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) | |
72 | { | |
73 | perror("prctl"); | |
74 | exit(0); | |
75 | } | |
76 | should_segv = 1; | |
77 | } | |
78 | } | |
79 | ||
80 | ||
f0cd147e | 81 | int main(void) |
f1326973 EB |
82 | { |
83 | int n_tasks = 100, i; | |
84 | ||
85 | fprintf(stderr, "[No further output means we're allright]\n"); | |
86 | ||
87 | for (i=0; i<n_tasks; i++) | |
88 | if (fork() == 0) | |
89 | task(); | |
90 | ||
91 | for (i=0; i<n_tasks; i++) | |
92 | wait(NULL); | |
93 | ||
94 | exit(0); | |
95 | } | |
96 |