1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...) |
4 | * |
5 | * Tests if the control register is updated correctly |
6 | * when set with prctl() |
7 | * |
8 | * Warning: this test will cause a very high load for a few seconds |
9 | * |
10 | */ |
11 | |
12 | #include <stdio.h> |
13 | #include <stdlib.h> |
14 | #include <unistd.h> |
15 | #include <signal.h> |
16 | #include <inttypes.h> |
17 | #include <wait.h> |
18 | |
19 | |
20 | #include <sys/prctl.h> |
21 | #include <linux/prctl.h> |
22 | |
23 | /* Get/set the process' ability to use the timestamp counter instruction */ |
24 | #ifndef PR_GET_TSC |
25 | #define PR_GET_TSC 25 |
26 | #define PR_SET_TSC 26 |
27 | # define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */ |
28 | # define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */ |
29 | #endif |
30 | |
31 | /* snippet from wikipedia :-) */ |
32 | |
33 | static uint64_t rdtsc(void) |
34 | { |
35 | uint32_t lo, hi; |
36 | /* We cannot use "=A", since this would use %rax on x86_64 */ |
37 | __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi)); |
38 | return (uint64_t)hi << 32 | lo; |
39 | } |
40 | |
41 | int should_segv = 0; |
42 | |
43 | static void sigsegv_cb(int sig) |
44 | { |
45 | if (!should_segv) |
46 | { |
47 | fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n" ); |
48 | exit(0); |
49 | } |
50 | if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) |
51 | { |
52 | perror("prctl" ); |
53 | exit(0); |
54 | } |
55 | should_segv = 0; |
56 | |
57 | rdtsc(); |
58 | } |
59 | |
60 | static void task(void) |
61 | { |
62 | signal(SIGSEGV, sigsegv_cb); |
63 | alarm(10); |
64 | for(;;) |
65 | { |
66 | rdtsc(); |
67 | if (should_segv) |
68 | { |
69 | fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n" ); |
70 | exit(0); |
71 | } |
72 | if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) |
73 | { |
74 | perror("prctl" ); |
75 | exit(0); |
76 | } |
77 | should_segv = 1; |
78 | } |
79 | } |
80 | |
81 | |
82 | int main(void) |
83 | { |
84 | int n_tasks = 100, i; |
85 | |
86 | fprintf(stderr, "[No further output means we're all right]\n" ); |
87 | |
88 | for (i=0; i<n_tasks; i++) |
89 | if (fork() == 0) |
90 | task(); |
91 | |
92 | for (i=0; i<n_tasks; i++) |
93 | wait(NULL); |
94 | |
95 | exit(0); |
96 | } |
97 | |
98 | |