Blame view

Documentation/prctl/disable-tsc-test.c 2.07 KB
f13269732   Erik Bosman   generic, x86: add...
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
  /*
   * Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
   *
   * Basic test to test behaviour of PR_GET_TSC and PR_SET_TSC
   */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <unistd.h>
  #include <signal.h>
  #include <inttypes.h>
  
  
  #include <sys/prctl.h>
  #include <linux/prctl.h>
  
  /* Get/set the process' ability to use the timestamp counter instruction */
  #ifndef PR_GET_TSC
  #define PR_GET_TSC 25
  #define PR_SET_TSC 26
  # define PR_TSC_ENABLE		1   /* allow the use of the timestamp counter */
  # define PR_TSC_SIGSEGV		2   /* throw a SIGSEGV instead of reading the TSC */
  #endif
  
  const char *tsc_names[] =
  {
  	[0] = "[not set]",
  	[PR_TSC_ENABLE] = "PR_TSC_ENABLE",
  	[PR_TSC_SIGSEGV] = "PR_TSC_SIGSEGV",
  };
  
  uint64_t rdtsc() {
  uint32_t lo, hi;
  /* We cannot use "=A", since this would use %rax on x86_64 */
  __asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
  return (uint64_t)hi << 32 | lo;
  }
  
  void sigsegv_cb(int sig)
  {
  	int tsc_val = 0;
  
  	printf("[ SIG_SEGV ]
  ");
  	printf("prctl(PR_GET_TSC, &tsc_val); ");
  	fflush(stdout);
  
  	if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  		perror("prctl");
  
  	printf("tsc_val == %s
  ", tsc_names[tsc_val]);
  	printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)
  ");
  	fflush(stdout);
  	if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  		perror("prctl");
  
  	printf("rdtsc() == ");
  }
  
  int main(int argc, char **argv)
  {
  	int tsc_val = 0;
  
  	signal(SIGSEGV, sigsegv_cb);
  
  	printf("rdtsc() == %llu
  ", (unsigned long long)rdtsc());
  	printf("prctl(PR_GET_TSC, &tsc_val); ");
  	fflush(stdout);
  
  	if ( prctl(PR_GET_TSC, &tsc_val) == -1)
  		perror("prctl");
  
  	printf("tsc_val == %s
  ", tsc_names[tsc_val]);
  	printf("rdtsc() == %llu
  ", (unsigned long long)rdtsc());
  	printf("prctl(PR_SET_TSC, PR_TSC_ENABLE)
  ");
  	fflush(stdout);
  
  	if ( prctl(PR_SET_TSC, PR_TSC_ENABLE) == -1)
  		perror("prctl");
  
  	printf("rdtsc() == %llu
  ", (unsigned long long)rdtsc());
  	printf("prctl(PR_SET_TSC, PR_TSC_SIGSEGV)
  ");
  	fflush(stdout);
  
  	if ( prctl(PR_SET_TSC, PR_TSC_SIGSEGV) == -1)
  		perror("prctl");
  
  	printf("rdtsc() == ");
  	fflush(stdout);
  	printf("%llu
  ", (unsigned long long)rdtsc());
  	fflush(stdout);
  
  	exit(EXIT_SUCCESS);
  }