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 | * at context switches |
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 | static uint64_t rdtsc(void) |
32 | { |
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 | static void sigsegv_expect(int sig) |
40 | { |
41 | /* */ |
42 | } |
43 | |
44 | static void segvtask(void) |
45 | { |
46 | if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0) |
47 | { |
48 | perror("prctl" ); |
49 | exit(0); |
50 | } |
51 | signal(SIGSEGV, sigsegv_expect); |
52 | alarm(10); |
53 | rdtsc(); |
54 | fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n" ); |
55 | exit(0); |
56 | } |
57 | |
58 | |
59 | static void sigsegv_fail(int sig) |
60 | { |
61 | fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n" ); |
62 | exit(0); |
63 | } |
64 | |
65 | static void rdtsctask(void) |
66 | { |
67 | if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0) |
68 | { |
69 | perror("prctl" ); |
70 | exit(0); |
71 | } |
72 | signal(SIGSEGV, sigsegv_fail); |
73 | alarm(10); |
74 | for(;;) rdtsc(); |
75 | } |
76 | |
77 | |
78 | int main(void) |
79 | { |
80 | int n_tasks = 100, i; |
81 | |
82 | fprintf(stderr, "[No further output means we're all right]\n" ); |
83 | |
84 | for (i=0; i<n_tasks; i++) |
85 | if (fork() == 0) |
86 | { |
87 | if (i & 1) |
88 | segvtask(); |
89 | else |
90 | rdtsctask(); |
91 | } |
92 | |
93 | for (i=0; i<n_tasks; i++) |
94 | wait(NULL); |
95 | |
96 | exit(0); |
97 | } |
98 | |
99 | |