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Documentation / prctl / disable-tsc-test.c




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Based on kernel version 4.1. Page generated on 2015-06-28 12:14 EST.

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	
25	const char *tsc_names[] =
26	{
27		[0] = "[not set]",
28		[PR_TSC_ENABLE] = "PR_TSC_ENABLE",
29		[PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
30	};
31	
32	static uint64_t rdtsc(void)
33	{
34	uint32_t lo, hi;
35	/* We cannot use "=A", since this would use %rax on x86_64 */
36	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
37	return (uint64_t)hi << 32 | lo;
38	}
39	
40	static void sigsegv_cb(int sig)
41	{
42		int tsc_val = 0;
43	
44		printf("[ SIG_SEGV ]\n");
45		printf("prctl(PR_GET_TSC, &tsc_val); ");
46		fflush(stdout);
47	
48		if ( prctl(PR_GET_TSC, &tsc_val) == -1)
49			perror("prctl");
50	
51		printf("tsc_val == %s\n", tsc_names[tsc_val]);
52		printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
53		fflush(stdout);
54		if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
55			perror("prctl");
56	
57		printf("rdtsc() == ");
58	}
59	
60	int main(int argc, char **argv)
61	{
62		int tsc_val = 0;
63	
64		signal(SIGSEGV, sigsegv_cb);
65	
66		printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
67		printf("prctl(PR_GET_TSC, &tsc_val); ");
68		fflush(stdout);
69	
70		if ( prctl(PR_GET_TSC, &tsc_val) == -1)
71			perror("prctl");
72	
73		printf("tsc_val == %s\n", tsc_names[tsc_val]);
74		printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
75		printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)\n");
76		fflush(stdout);
77	
78		if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
79			perror("prctl");
80	
81		printf("rdtsc() == %llu\n", (unsigned long long)rdtsc());
82		printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)\n");
83		fflush(stdout);
84	
85		if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
86			perror("prctl");
87	
88		printf("rdtsc() == ");
89		fflush(stdout);
90		printf("%llu\n", (unsigned long long)rdtsc());
91		fflush(stdout);
92	
93		exit(EXIT_SUCCESS);
94	}
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