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
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
|
// SPDX-License-Identifier: GPL-2.0
#define _GNU_SOURCE
#include <pthread.h>
#include <stdio.h>
#include <dlfcn.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>
#include "include/liblockdep/mutex.h"
#include "../../include/linux/rbtree.h"
/**
* struct lock_lookup - liblockdep's view of a single unique lock
* @orig: pointer to the original pthread lock, used for lookups
* @dep_map: lockdep's dep_map structure
* @key: lockdep's key structure
* @node: rb-tree node used to store the lock in a global tree
* @name: a unique name for the lock
*/
struct lock_lookup {
void *orig; /* Original pthread lock, used for lookups */
struct lockdep_map dep_map; /* Since all locks are dynamic, we need
* a dep_map and a key for each lock */
/*
* Wait, there's no support for key classes? Yup :(
* Most big projects wrap the pthread api with their own calls to
* be compatible with different locking methods. This means that
* "classes" will be brokes since the function that creates all
* locks will point to a generic locking function instead of the
* actual code that wants to do the locking.
*/
struct lock_class_key key;
struct rb_node node;
#define LIBLOCKDEP_MAX_LOCK_NAME 22
char name[LIBLOCKDEP_MAX_LOCK_NAME];
};
/* This is where we store our locks */
static struct rb_root locks = RB_ROOT;
static pthread_rwlock_t locks_rwlock = PTHREAD_RWLOCK_INITIALIZER;
/* pthread mutex API */
#ifdef __GLIBC__
extern int __pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *attr);
extern int __pthread_mutex_lock(pthread_mutex_t *mutex);
extern int __pthread_mutex_trylock(pthread_mutex_t *mutex);
extern int __pthread_mutex_unlock(pthread_mutex_t *mutex);
extern int __pthread_mutex_destroy(pthread_mutex_t *mutex);
#else
#define __pthread_mutex_init NULL
#define __pthread_mutex_lock NULL
#define __pthread_mutex_trylock NULL
#define __pthread_mutex_unlock NULL
#define __pthread_mutex_destroy NULL
#endif
static int (*ll_pthread_mutex_init)(pthread_mutex_t *mutex,
const pthread_mutexattr_t *attr) = __pthread_mutex_init;
static int (*ll_pthread_mutex_lock)(pthread_mutex_t *mutex) = __pthread_mutex_lock;
static int (*ll_pthread_mutex_trylock)(pthread_mutex_t *mutex) = __pthread_mutex_trylock;
static int (*ll_pthread_mutex_unlock)(pthread_mutex_t *mutex) = __pthread_mutex_unlock;
static int (*ll_pthread_mutex_destroy)(pthread_mutex_t *mutex) = __pthread_mutex_destroy;
/* pthread rwlock API */
#ifdef __GLIBC__
extern int __pthread_rwlock_init(pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr);
extern int __pthread_rwlock_destroy(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_wrlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_rdlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock);
extern int __pthread_rwlock_unlock(pthread_rwlock_t *rwlock);
#else
#define __pthread_rwlock_init NULL
#define __pthread_rwlock_destroy NULL
#define __pthread_rwlock_wrlock NULL
#define __pthread_rwlock_trywrlock NULL
#define __pthread_rwlock_rdlock NULL
#define __pthread_rwlock_tryrdlock NULL
#define __pthread_rwlock_unlock NULL
#endif
static int (*ll_pthread_rwlock_init)(pthread_rwlock_t *rwlock,
const pthread_rwlockattr_t *attr) = __pthread_rwlock_init;
static int (*ll_pthread_rwlock_destroy)(pthread_rwlock_t *rwlock) = __pthread_rwlock_destroy;
static int (*ll_pthread_rwlock_rdlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_rdlock;
static int (*ll_pthread_rwlock_tryrdlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_tryrdlock;
static int (*ll_pthread_rwlock_trywrlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_trywrlock;
static int (*ll_pthread_rwlock_wrlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_wrlock;
static int (*ll_pthread_rwlock_unlock)(pthread_rwlock_t *rwlock) = __pthread_rwlock_unlock;
enum { none, prepare, done, } __init_state;
static void init_preload(void);
static void try_init_preload(void)
{
if (__init_state != done)
init_preload();
}
static struct rb_node **__get_lock_node(void *lock, struct rb_node **parent)
{
struct rb_node **node = &locks.rb_node;
struct lock_lookup *l;
*parent = NULL;
while (*node) {
l = rb_entry(*node, struct lock_lookup, node);
*parent = *node;
if (lock < l->orig)
node = &l->node.rb_left;
else if (lock > l->orig)
node = &l->node.rb_right;
else
return node;
}
return node;
}
#ifndef LIBLOCKDEP_STATIC_ENTRIES
#define LIBLOCKDEP_STATIC_ENTRIES 1024
#endif
static struct lock_lookup __locks[LIBLOCKDEP_STATIC_ENTRIES];
static int __locks_nr;
static inline bool is_static_lock(struct lock_lookup *lock)
{
return lock >= __locks && lock < __locks + ARRAY_SIZE(__locks);
}
static struct lock_lookup *alloc_lock(void)
{
if (__init_state != done) {
/*
* Some programs attempt to initialize and use locks in their
* allocation path. This means that a call to malloc() would
* result in locks being initialized and locked.
*
* Why is it an issue for us? dlsym() below will try allocating
* to give us the original function. Since this allocation will
* result in a locking operations, we have to let pthread deal
* with it, but we can't! we don't have the pointer to the
* original API since we're inside dlsym() trying to get it
*/
int idx = __locks_nr++;
if (idx >= ARRAY_SIZE(__locks)) {
dprintf(STDERR_FILENO,
"LOCKDEP error: insufficient LIBLOCKDEP_STATIC_ENTRIES\n");
exit(EX_UNAVAILABLE);
}
return __locks + idx;
}
return malloc(sizeof(struct lock_lookup));
}
static inline void free_lock(struct lock_lookup *lock)
{
if (likely(!is_static_lock(lock)))
free(lock);
}
/**
* __get_lock - find or create a lock instance
* @lock: pointer to a pthread lock function
*
* Try to find an existing lock in the rbtree using the provided pointer. If
* one wasn't found - create it.
*/
static struct lock_lookup *__get_lock(void *lock)
{
struct rb_node **node, *parent;
struct lock_lookup *l;
ll_pthread_rwlock_rdlock(&locks_rwlock);
node = __get_lock_node(lock, &parent);
ll_pthread_rwlock_unlock(&locks_rwlock);
if (*node) {
return rb_entry(*node, struct lock_lookup, node);
}
/* We didn't find the lock, let's create it */
l = alloc_lock();
if (l == NULL)
return NULL;
l->orig = lock;
/*
* Currently the name of the lock is the ptr value of the pthread lock,
* while not optimal, it makes debugging a bit easier.
*
* TODO: Get the real name of the lock using libdwarf
*/
sprintf(l->name, "%p", lock);
lockdep_init_map(&l->dep_map, l->name, &l->key, 0);
ll_pthread_rwlock_wrlock(&locks_rwlock);
/* This might have changed since the last time we fetched it */
node = __get_lock_node(lock, &parent);
rb_link_node(&l->node, parent, node);
rb_insert_color(&l->node, &locks);
ll_pthread_rwlock_unlock(&locks_rwlock);
return l;
}
static void __del_lock(struct lock_lookup *lock)
{
ll_pthread_rwlock_wrlock(&locks_rwlock);
rb_erase(&lock->node, &locks);
ll_pthread_rwlock_unlock(&locks_rwlock);
free_lock(lock);
}
int pthread_mutex_init(pthread_mutex_t *mutex,
const pthread_mutexattr_t *attr)
{
int r;
/*
* We keep trying to init our preload module because there might be
* code in init sections that tries to touch locks before we are
* initialized, in that case we'll need to manually call preload
* to get us going.
*
* Funny enough, kernel's lockdep had the same issue, and used
* (almost) the same solution. See look_up_lock_class() in
* kernel/locking/lockdep.c for details.
*/
try_init_preload();
r = ll_pthread_mutex_init(mutex, attr);
if (r == 0)
/*
* We do a dummy initialization here so that lockdep could
* warn us if something fishy is going on - such as
* initializing a held lock.
*/
__get_lock(mutex);
return r;
}
int pthread_mutex_lock(pthread_mutex_t *mutex)
{
int r;
try_init_preload();
lock_acquire(&__get_lock(mutex)->dep_map, 0, 0, 0, 1, NULL,
(unsigned long)_RET_IP_);
/*
* Here's the thing with pthread mutexes: unlike the kernel variant,
* they can fail.
*
* This means that the behaviour here is a bit different from what's
* going on in the kernel: there we just tell lockdep that we took the
* lock before actually taking it, but here we must deal with the case
* that locking failed.
*
* To do that we'll "release" the lock if locking failed - this way
* we'll get lockdep doing the correct checks when we try to take
* the lock, and if that fails - we'll be back to the correct
* state by releasing it.
*/
r = ll_pthread_mutex_lock(mutex);
if (r)
lock_release(&__get_lock(mutex)->dep_map, (unsigned long)_RET_IP_);
return r;
}
int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
int r;
try_init_preload();
lock_acquire(&__get_lock(mutex)->dep_map, 0, 1, 0, 1, NULL, (unsigned
|