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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 | * 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 | ||
0421fc83 PF |
30 | static uint64_t rdtsc(void) |
31 | { | |
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32 | uint32_t lo, hi; |
33 | /* We cannot use "=A", since this would use %rax on x86_64 */ | |
34 | __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); | |
35 | return (uint64_t)hi << 32 | lo; | |
36 | } | |
37 | ||
0421fc83 | 38 | static void sigsegv_expect(int sig) |
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39 | { |
40 | /* */ | |
41 | } | |
42 | ||
0421fc83 | 43 | static void segvtask(void) |
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44 | { |
45 | if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) | |
46 | { | |
47 | perror("prctl"); | |
48 | exit(0); | |
49 | } | |
50 | signal(SIGSEGV, sigsegv_expect); | |
51 | alarm(10); | |
52 | rdtsc(); | |
53 | fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n"); | |
54 | exit(0); | |
55 | } | |
56 | ||
57 | ||
0421fc83 | 58 | static void sigsegv_fail(int sig) |
f1326973 EB |
59 | { |
60 | fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n"); | |
61 | exit(0); | |
62 | } | |
63 | ||
0421fc83 | 64 | static void rdtsctask(void) |
f1326973 EB |
65 | { |
66 | if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) | |
67 | { | |
68 | perror("prctl"); | |
69 | exit(0); | |
70 | } | |
71 | signal(SIGSEGV, sigsegv_fail); | |
72 | alarm(10); | |
73 | for(;;) rdtsc(); | |
74 | } | |
75 | ||
76 | ||
77 | int main(int argc, char **argv) | |
78 | { | |
79 | int n_tasks = 100, i; | |
80 | ||
81 | fprintf(stderr, "[No further output means we're allright]\n"); | |
82 | ||
83 | for (i=0; i<n_tasks; i++) | |
84 | if (fork() == 0) | |
85 | { | |
86 | if (i & 1) | |
87 | segvtask(); | |
88 | else | |
89 | rdtsctask(); | |
90 | } | |
91 | ||
92 | for (i=0; i<n_tasks; i++) | |
93 | wait(NULL); | |
94 | ||
95 | exit(0); | |
96 | } | |
97 |