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
|
/*
* Tests for prctl(PR_GET_TSC, ...) / prctl(PR_SET_TSC, ...)
*
* Tests if the control register is updated correctly
* at context switches
*
* Warning: this test will cause a very high load for a few seconds
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <inttypes.h>
#include <wait.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
static uint64_t rdtsc(void)
{
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;
}
static void sigsegv_expect(int sig)
{
/* */
}
static void segvtask(void)
{
if (prctl(PR_SET_TSC, PR_TSC_SIGSEGV) < 0)
{
perror("prctl");
exit(0);
}
signal(SIGSEGV, sigsegv_expect);
alarm(10);
rdtsc();
fprintf(stderr, "FATAL ERROR, rdtsc() succeeded while disabled\n");
exit(0);
}
static void sigsegv_fail(int sig)
{
fprintf(stderr, "FATAL ERROR, rdtsc() failed while enabled\n");
exit(0);
}
static void rdtsctask(void)
{
if (prctl(PR_SET_TSC, PR_TSC_ENABLE) < 0)
{
perror("prctl");
exit(0);
}
signal(SIGSEGV, sigsegv_fail);
alarm(10);
for(;;) rdtsc();
}
int main(void)
{
int n_tasks = 100, i;
fprintf(stderr, "[No further output means we're allright]\n");
for (i=0; i<n_tasks; i++)
if (fork() == 0)
{
if (i & 1)
segvtask();
else
rdtsctask();
}
for (i=0; i<n_tasks; i++)
wait(NULL);
exit(0);
}
|
