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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 | |
96 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
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