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
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
/*
* libpulp - User-space Livepatching Library
*
* Copyright (C) 2021 SUSE Software Solutions GmbH
*
* This file is part of libpulp.
*
* libpulp is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* libpulp is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with libpulp. If not, see <http://www.gnu.org/licenses/>.
*/
#include <err.h>
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#define NUM_THREADS 2
static pthread_t threads[NUM_THREADS];
static pthread_barrier_t barrier;
char *banner_get(void);
char **banner_get_ref(void);
void banner_set(char *);
/* On two threads this should work. If more, race conditions will appear. */
static volatile int gate1 = 0;
static volatile int gate2 = 0;
void *
thread_func(void *arg)
{
long i = (long)arg;
static __thread char buf[256];
if (i == 1) {
// Thread 1 must be slower and print after thread 0.
while (gate1 == 0)
usleep(1000); // Await.
}
/* Original banner. */
printf("Banner addr: 0x%lX\n", (unsigned long)banner_get_ref());
printf("%s\n", banner_get());
sprintf(buf, "Banner changed from thread_func: %lu\n", i);
/* Use original banner setting function. */
banner_set(strdup(buf));
printf("%s\n", banner_get());
if (i == 0) {
// Allow thread 1 to run.
gate1++;
}
pthread_barrier_wait(&barrier);
if (i == 1) {
// Thread 1 must be slower and print after thread 0.
while (gate2 == 0)
usleep(1000); // Await.
}
/*
* Use banner setting function again, which is supposed to have been
* changed by the test driver. The patched function ignores the
* argument, so 'String from main' should not be in the output.
*/
sprintf(buf, "String from thread_func: %lu\n", i);
banner_set(buf);
printf("%s\n", banner_get());
if (i == 0) {
// Allow thread 1 to run.
gate2++;
}
return NULL;
}
static void
create_threads()
{
int i;
for (i = 0; i < NUM_THREADS; i++) {
if (pthread_create(&threads[i], NULL, thread_func, (void *)((long)i))) {
errx(1, "Thread creation failure.");
}
}
}
static void
join_threads()
{
int i;
for (i = 0; i < NUM_THREADS; i++) {
if (pthread_join(threads[i], NULL)) {
errx(1, "Thread join failure.");
}
}
}
int
main(void)
{
char buffer[128];
pthread_barrier_init(&barrier, NULL, NUM_THREADS + 1);
create_threads();
/* Wait for input. */
if (fgets(buffer, sizeof(buffer), stdin) == NULL) {
if (errno) {
perror("tls");
return 1;
}
}
pthread_barrier_wait(&barrier);
join_threads();
return 0;
}
|
