Root/Documentation/prctl/disable-tsc-test.c

1/*
2 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
3 *
4 * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC
5 */
6
7#include <stdio.h>
8#include <stdlib.h>
9#include <unistd.h>
10#include <signal.h>
11#include <inttypes.h>
12
13
14#include <sys/prctl.h>
15#include <linux/prctl.h>
16
17/* Get/set the process' ability to use the timestamp counter instruction */
18#ifndef PR_GET_TSC
19#define PR_GET_TSC 25
20#define PR_SET_TSC 26
21# define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
22# define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
23#endif
24
25const char *tsc_names[] =
26{
27    [0] = "[not set]",
28    [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
29    [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
30};
31
32uint64_t rdtsc() {
33uint32_t lo, hi;
34/* We cannot use "=A", since this would use %rax on x86_64 */
35__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
36return (uint64_t)hi << 32 | lo;
37}
38
39void sigsegv_cb(int sig)
40{
41    int tsc_val = 0;
42
43    printf("[ SIG_SEGV ]\n");
44    printf("prctl(PR_GET_TSC, &tsc_val); ");
45    fflush(stdout);
46
47    if ( prctl(PR_GET_TSC, &tsc_val) == -1)
48        perror("prctl");
49
50    printf("tsc_val == %s\n", tsc_names[tsc_val]);
51    printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
52    fflush(stdout);
53    if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
54        perror("prctl");
55
56    printf("rdtsc() == ");
57}
58
59int main(int argc, char **argv)
60{
61    int tsc_val = 0;
62
63    signal(SIGSEGV, sigsegv_cb);
64
65    printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
66    printf("prctl(PR_GET_TSC, &tsc_val); ");
67    fflush(stdout);
68
69    if ( prctl(PR_GET_TSC, &tsc_val) == -1)
70        perror("prctl");
71
72    printf("tsc_val == %s\n", tsc_names[tsc_val]);
73    printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
74    printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
75    fflush(stdout);
76
77    if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
78        perror("prctl");
79
80    printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
81    printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
82    fflush(stdout);
83
84    if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
85        perror("prctl");
86
87    printf("rdtsc() == ");
88    fflush(stdout);
89    printf("%llu\n", (unsigned long long)rdtsc());
90    fflush(stdout);
91
92    exit(EXIT_SUCCESS);
93}
94
95

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