1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
4 *
5 * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC
6 */
7
8#include <stdio.h>
9#include <stdlib.h>
10#include <unistd.h>
11#include <signal.h>
12#include <inttypes.h>
13
14
15#include <sys/prctl.h>
16#include <linux/prctl.h>
17
18/* Get/set the process' ability to use the timestamp counter instruction */
19#ifndef PR_GET_TSC
20#define PR_GET_TSC 25
21#define PR_SET_TSC 26
22# define PR_TSC_ENABLE 1 /* allow the use of the timestamp counter */
23# define PR_TSC_SIGSEGV 2 /* throw a SIGSEGV instead of reading the TSC */
24#endif
25
26const char *tsc_names[] =
27{
28 [0] = "[not set]",
29 [PR_TSC_ENABLE] = "PR_TSC_ENABLE",
30 [PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
31};
32
33static uint64_t rdtsc(void)
34{
35uint32_t lo, hi;
36/* We cannot use "=A", since this would use %rax on x86_64 */
37__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
38return (uint64_t)hi << 32 | lo;
39}
40
41static void sigsegv_cb(int sig)
42{
43 int tsc_val = 0;
44
45 printf("[ SIG_SEGV ]\n");
46 printf("prctl(PR_GET_TSC, &tsc_val); ");
47 fflush(stdout);
48
49 if ( prctl(PR_GET_TSC, &tsc_val) == -1)
50 perror("prctl");
51
52 printf("tsc_val == %s\n", tsc_names[tsc_val]);
53 printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
54 fflush(stdout);
55 if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
56 perror("prctl");
57
58 printf("rdtsc() == ");
59}
60
61int main(void)
62{
63 int tsc_val = 0;
64
65 signal(SIGSEGV, sigsegv_cb);
66
67 printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
68 printf("prctl(PR_GET_TSC, &tsc_val); ");
69 fflush(stdout);
70
71 if ( prctl(PR_GET_TSC, &tsc_val) == -1)
72 perror("prctl");
73
74 printf("tsc_val == %s\n", tsc_names[tsc_val]);
75 printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
76 printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
77 fflush(stdout);
78
79 if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
80 perror("prctl");
81
82 printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
83 printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
84 fflush(stdout);
85
86 if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
87 perror("prctl");
88
89 printf("rdtsc() == ");
90 fflush(stdout);
91 printf("%llu\n", (unsigned long long)rdtsc());
92 fflush(stdout);
93
94 exit(EXIT_SUCCESS);
95}
96
97

source code of linux/tools/testing/selftests/prctl/disable-tsc-test.c