about summary refs log tree commit diff
path: root/nptl/nptl-printers.py
blob: e402f232c7e7ff6f729a5911fe5a5defd209238a (plain) (blame)
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
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
# Pretty printers for the NPTL lock types.
#
# Copyright (C) 2016 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
#
# The GNU C Library 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.
#
# The GNU C Library 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 Lesser General Public
# License along with the GNU C Library; if not, see
# <http://www.gnu.org/licenses/>.

"""This file contains the gdb pretty printers for the following types:

    * pthread_mutex_t
    * pthread_mutexattr_t
    * pthread_cond_t
    * pthread_condattr_t
    * pthread_rwlock_t
    * pthread_rwlockattr_t

You can check which printers are registered and enabled by issuing the
'info pretty-printer' gdb command.  Printers should trigger automatically when
trying to print a variable of one of the types mentioned above.
"""

from __future__ import print_function

import gdb
import gdb.printing
from nptl_lock_constants import *

MUTEX_TYPES = {
    PTHREAD_MUTEX_NORMAL: ('Type', 'Normal'),
    PTHREAD_MUTEX_RECURSIVE: ('Type', 'Recursive'),
    PTHREAD_MUTEX_ERRORCHECK: ('Type', 'Error check'),
    PTHREAD_MUTEX_ADAPTIVE_NP: ('Type', 'Adaptive')
}

class MutexPrinter(object):
    """Pretty printer for pthread_mutex_t."""

    def __init__(self, mutex):
        """Initialize the printer's internal data structures.

        Args:
            mutex: A gdb.value representing a pthread_mutex_t.
        """

        data = mutex['__data']
        self.lock = data['__lock']
        self.count = data['__count']
        self.owner = data['__owner']
        self.kind = data['__kind']
        self.values = []
        self.read_values()

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_mutex_t.
        """

        return 'pthread_mutex_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_mutex_t.
        """

        return self.values

    def read_values(self):
        """Read the mutex's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        self.read_type()
        self.read_status()
        self.read_attributes()
        self.read_misc_info()

    def read_type(self):
        """Read the mutex's type."""

        mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK

        # mutex_type must be casted to int because it's a gdb.Value
        self.values.append(MUTEX_TYPES[int(mutex_type)])

    def read_status(self):
        """Read the mutex's status.

        For architectures which support lock elision, this method reads
        whether the mutex appears as locked in memory (i.e. it may show it as
        unlocked even after calling pthread_mutex_lock).
        """

        if self.kind == PTHREAD_MUTEX_DESTROYED:
            self.values.append(('Status', 'Destroyed'))
        elif self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
            self.read_status_robust()
        else:
            self.read_status_no_robust()

    def read_status_robust(self):
        """Read the status of a robust mutex.

        In glibc robust mutexes are implemented in a very different way than
        non-robust ones.  This method reads their locking status,
        whether it may have waiters, their registered owner (if any),
        whether the owner is alive or not, and the status of the state
        they're protecting.
        """

        if self.lock == PTHREAD_MUTEX_UNLOCKED:
            self.values.append(('Status', 'Unlocked'))
        else:
            if self.lock & FUTEX_WAITERS:
                self.values.append(('Status', 'Locked, possibly with waiters'))
            else:
                self.values.append(('Status',
                                    'Locked, possibly with no waiters'))

            if self.lock & FUTEX_OWNER_DIED:
                self.values.append(('Owner ID', '%d (dead)' % self.owner))
            else:
                self.values.append(('Owner ID', self.lock & FUTEX_TID_MASK))

        if self.owner == PTHREAD_MUTEX_INCONSISTENT:
            self.values.append(('State protected by this mutex',
                                'Inconsistent'))
        elif self.owner == PTHREAD_MUTEX_NOTRECOVERABLE:
            self.values.append(('State protected by this mutex',
                                'Not recoverable'))

    def read_status_no_robust(self):
        """Read the status of a non-robust mutex.

        Read info on whether the mutex is locked, if it may have waiters
        and its owner (if any).
        """

        lock_value = self.lock

        if self.kind & PTHREAD_MUTEX_PRIO_PROTECT_NP:
            lock_value &= ~(PTHREAD_MUTEX_PRIO_CEILING_MASK)

        if lock_value == PTHREAD_MUTEX_UNLOCKED:
            self.values.append(('Status', 'Unlocked'))
        else:
            if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
                waiters = self.lock & FUTEX_WAITERS
                owner = self.lock & FUTEX_TID_MASK
            else:
                # Mutex protocol is PP or none
                waiters = (self.lock != PTHREAD_MUTEX_LOCKED_NO_WAITERS)
                owner = self.owner

            if waiters:
                self.values.append(('Status', 'Locked, possibly with waiters'))
            else:
                self.values.append(('Status',
                                    'Locked, possibly with no waiters'))

            self.values.append(('Owner ID', owner))

    def read_attributes(self):
        """Read the mutex's attributes."""

        if self.kind != PTHREAD_MUTEX_DESTROYED:
            if self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
                self.values.append(('Robust', 'Yes'))
            else:
                self.values.append(('Robust', 'No'))

            # In glibc, robust mutexes always have their pshared flag set to
            # 'shared' regardless of what the pshared flag of their
            # mutexattr was.  Therefore a robust mutex will act as shared
            # even if it was initialized with a 'private' mutexattr.
            if self.kind & PTHREAD_MUTEX_PSHARED_BIT:
                self.values.append(('Shared', 'Yes'))
            else:
                self.values.append(('Shared', 'No'))

            if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
                self.values.append(('Protocol', 'Priority inherit'))
            elif self.kind & PTHREAD_MUTEX_PRIO_PROTECT_NP:
                prio_ceiling = ((self.lock & PTHREAD_MUTEX_PRIO_CEILING_MASK)
                                >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT)

                self.values.append(('Protocol', 'Priority protect'))
                self.values.append(('Priority ceiling', prio_ceiling))
            else:
                # PTHREAD_PRIO_NONE
                self.values.append(('Protocol', 'None'))

    def read_misc_info(self):
        """Read miscellaneous info on the mutex.

        For now this reads the number of times a recursive mutex was locked
        by the same thread.
        """

        mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK

        if mutex_type == PTHREAD_MUTEX_RECURSIVE and self.count > 1:
            self.values.append(('Times locked recursively', self.count))

class MutexAttributesPrinter(object):
    """Pretty printer for pthread_mutexattr_t.

    In the NPTL this is a type that's always casted to struct pthread_mutexattr
    which has a single 'mutexkind' field containing the actual attributes.
    """

    def __init__(self, mutexattr):
        """Initialize the printer's internal data structures.

        Args:
            mutexattr: A gdb.value representing a pthread_mutexattr_t.
        """

        self.values = []

        try:
            mutexattr_struct = gdb.lookup_type('struct pthread_mutexattr')
            self.mutexattr = mutexattr.cast(mutexattr_struct)['mutexkind']
            self.read_values()
        except gdb.error:
            # libpthread doesn't have debug symbols, thus we can't find the
            # real struct type.  Just print the union members.
            self.values.append(('__size', mutexattr['__size']))
            self.values.append(('__align', mutexattr['__align']))

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_mutexattr_t.
        """

        return 'pthread_mutexattr_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_mutexattr_t.
        """

        return self.values

    def read_values(self):
        """Read the mutexattr's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        mutexattr_type = (self.mutexattr
                          & ~PTHREAD_MUTEXATTR_FLAG_BITS
                          & ~PTHREAD_MUTEX_NO_ELISION_NP)

        # mutexattr_type must be casted to int because it's a gdb.Value
        self.values.append(MUTEX_TYPES[int(mutexattr_type)])

        if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_ROBUST:
            self.values.append(('Robust', 'Yes'))
        else:
            self.values.append(('Robust', 'No'))

        if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_PSHARED:
            self.values.append(('Shared', 'Yes'))
        else:
            self.values.append(('Shared', 'No'))

        protocol = ((self.mutexattr & PTHREAD_MUTEXATTR_PROTOCOL_MASK) >>
                    PTHREAD_MUTEXATTR_PROTOCOL_SHIFT)

        if protocol == PTHREAD_PRIO_NONE:
            self.values.append(('Protocol', 'None'))
        elif protocol == PTHREAD_PRIO_INHERIT:
            self.values.append(('Protocol', 'Priority inherit'))
        elif protocol == PTHREAD_PRIO_PROTECT:
            self.values.append(('Protocol', 'Priority protect'))

CLOCK_IDS = {
    CLOCK_REALTIME: 'CLOCK_REALTIME',
    CLOCK_MONOTONIC: 'CLOCK_MONOTONIC',
    CLOCK_PROCESS_CPUTIME_ID: 'CLOCK_PROCESS_CPUTIME_ID',
    CLOCK_THREAD_CPUTIME_ID: 'CLOCK_THREAD_CPUTIME_ID',
    CLOCK_MONOTONIC_RAW: 'CLOCK_MONOTONIC_RAW',
    CLOCK_REALTIME_COARSE: 'CLOCK_REALTIME_COARSE',
    CLOCK_MONOTONIC_COARSE: 'CLOCK_MONOTONIC_COARSE'
}

class ConditionVariablePrinter(object):
    """Pretty printer for pthread_cond_t."""

    def __init__(self, cond):
        """Initialize the printer's internal data structures.

        Args:
            cond: A gdb.value representing a pthread_cond_t.
        """

        # Since PTHREAD_COND_SHARED is an integer, we need to cast it to void *
        # to be able to compare it to the condvar's __data.__mutex member.
        #
        # While it looks like self.shared_value should be a class variable,
        # that would result in it having an incorrect size if we're loading
        # these printers through .gdbinit for a 64-bit objfile in AMD64.
        # This is because gdb initially assumes the pointer size to be 4 bytes,
        # and only sets it to 8 after loading the 64-bit objfiles.  Since
        # .gdbinit runs before any objfiles are loaded, this would effectively
        # make self.shared_value have a size of 4, thus breaking later
        # comparisons with pointers whose types are looked up at runtime.
        void_ptr_type = gdb.lookup_type('void').pointer()
        self.shared_value = gdb.Value(PTHREAD_COND_SHARED).cast(void_ptr_type)

        data = cond['__data']
        self.total_seq = data['__total_seq']
        self.mutex = data['__mutex']
        self.nwaiters = data['__nwaiters']
        self.values = []

        self.read_values()

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_cond_t.
        """

        return 'pthread_cond_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_cond_t.
        """

        return self.values

    def read_values(self):
        """Read the condvar's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        self.read_status()
        self.read_attributes()
        self.read_mutex_info()

    def read_status(self):
        """Read the status of the condvar.

        This method reads whether the condvar is destroyed and how many threads
        are waiting for it.
        """

        if self.total_seq == PTHREAD_COND_DESTROYED:
            self.values.append(('Status', 'Destroyed'))

        self.values.append(('Threads waiting for this condvar',
                            self.nwaiters >> COND_NWAITERS_SHIFT))

    def read_attributes(self):
        """Read the condvar's attributes."""

        clock_id = self.nwaiters & ((1 << COND_NWAITERS_SHIFT) - 1)

        # clock_id must be casted to int because it's a gdb.Value
        self.values.append(('Clock ID', CLOCK_IDS[int(clock_id)]))

        shared = (self.mutex == self.shared_value)

        if shared:
            self.values.append(('Shared', 'Yes'))
        else:
            self.values.append(('Shared', 'No'))

    def read_mutex_info(self):
        """Read the data of the mutex this condvar is bound to.

        A pthread_cond_t's __data.__mutex member is a void * which
        must be casted to pthread_mutex_t *.  For shared condvars, this
        member isn't recorded and has a special value instead.
        """

        if self.mutex and self.mutex != self.shared_value:
            mutex_type = gdb.lookup_type('pthread_mutex_t')
            mutex = self.mutex.cast(mutex_type.pointer()).dereference()

            self.values.append(('Mutex', mutex))

class ConditionVariableAttributesPrinter(object):
    """Pretty printer for pthread_condattr_t.

    In the NPTL this is a type that's always casted to struct pthread_condattr,
    which has a single 'value' field containing the actual attributes.
    """

    def __init__(self, condattr):
        """Initialize the printer's internal data structures.

        Args:
            condattr: A gdb.value representing a pthread_condattr_t.
        """

        self.values = []

        try:
            condattr_struct = gdb.lookup_type('struct pthread_condattr')
            self.condattr = condattr.cast(condattr_struct)['value']
            self.read_values()
        except gdb.error:
            # libpthread doesn't have debug symbols, thus we can't find the
            # real struct type.  Just print the union members.
            self.values.append(('__size', condattr['__size']))
            self.values.append(('__align', condattr['__align']))

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_condattr_t.
        """

        return 'pthread_condattr_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_condattr_t.
        """

        return self.values

    def read_values(self):
        """Read the condattr's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        clock_id = self.condattr & ((1 << COND_NWAITERS_SHIFT) - 1)

        # clock_id must be casted to int because it's a gdb.Value
        self.values.append(('Clock ID', CLOCK_IDS[int(clock_id)]))

        if self.condattr & 1:
            self.values.append(('Shared', 'Yes'))
        else:
            self.values.append(('Shared', 'No'))

class RWLockPrinter(object):
    """Pretty printer for pthread_rwlock_t."""

    def __init__(self, rwlock):
        """Initialize the printer's internal data structures.

        Args:
            rwlock: A gdb.value representing a pthread_rwlock_t.
        """

        data = rwlock['__data']
        self.readers = data['__nr_readers']
        self.queued_readers = data['__nr_readers_queued']
        self.queued_writers = data['__nr_writers_queued']
        self.writer_id = data['__writer']
        self.shared = data['__shared']
        self.prefers_writers = data['__flags']
        self.values = []
        self.read_values()

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_rwlock_t.
        """

        return 'pthread_rwlock_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_rwlock_t.
        """

        return self.values

    def read_values(self):
        """Read the rwlock's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        self.read_status()
        self.read_attributes()

    def read_status(self):
        """Read the status of the rwlock."""

        # Right now pthread_rwlock_destroy doesn't do anything, so there's no
        # way to check if an rwlock is destroyed.

        if self.writer_id:
            self.values.append(('Status', 'Locked (Write)'))
            self.values.append(('Writer ID', self.writer_id))
        elif self.readers:
            self.values.append(('Status', 'Locked (Read)'))
            self.values.append(('Readers', self.readers))
        else:
            self.values.append(('Status', 'Unlocked'))

        self.values.append(('Queued readers', self.queued_readers))
        self.values.append(('Queued writers', self.queued_writers))

    def read_attributes(self):
        """Read the attributes of the rwlock."""

        if self.shared:
            self.values.append(('Shared', 'Yes'))
        else:
            self.values.append(('Shared', 'No'))

        if self.prefers_writers:
            self.values.append(('Prefers', 'Writers'))
        else:
            self.values.append(('Prefers', 'Readers'))

class RWLockAttributesPrinter(object):
    """Pretty printer for pthread_rwlockattr_t.

    In the NPTL this is a type that's always casted to
    struct pthread_rwlockattr, which has two fields ('lockkind' and 'pshared')
    containing the actual attributes.
    """

    def __init__(self, rwlockattr):
        """Initialize the printer's internal data structures.

        Args:
            rwlockattr: A gdb.value representing a pthread_rwlockattr_t.
        """

        self.values = []

        try:
            rwlockattr_struct = gdb.lookup_type('struct pthread_rwlockattr')
            self.rwlockattr = rwlockattr.cast(rwlockattr_struct)
            self.read_values()
        except gdb.error:
            # libpthread doesn't have debug symbols, thus we can't find the
            # real struct type.  Just print the union members.
            self.values.append(('__size', rwlockattr['__size']))
            self.values.append(('__align', rwlockattr['__align']))

    def to_string(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_rwlockattr_t.
        """

        return 'pthread_rwlockattr_t'

    def children(self):
        """gdb API function.

        This is called from gdb when we try to print a pthread_rwlockattr_t.
        """

        return self.values

    def read_values(self):
        """Read the rwlockattr's info and store it in self.values.

        The data contained in self.values will be returned by the Iterator
        created in self.children.
        """

        rwlock_type = self.rwlockattr['lockkind']
        shared = self.rwlockattr['pshared']

        if shared == PTHREAD_PROCESS_SHARED:
            self.values.append(('Shared', 'Yes'))
        else:
            # PTHREAD_PROCESS_PRIVATE
            self.values.append(('Shared', 'No'))

        if (rwlock_type == PTHREAD_RWLOCK_PREFER_READER_NP or
            rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NP):
            # This is a known bug.  Using PTHREAD_RWLOCK_PREFER_WRITER_NP will
            # still make the rwlock prefer readers.
            self.values.append(('Prefers', 'Readers'))
        elif rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP:
            self.values.append(('Prefers', 'Writers'))

def register(objfile):
    """Register the pretty printers within the given objfile."""

    printer = gdb.printing.RegexpCollectionPrettyPrinter('glibc-pthread-locks')

    printer.add_printer('pthread_mutex_t', r'^pthread_mutex_t$',
                        MutexPrinter)
    printer.add_printer('pthread_mutexattr_t', r'^pthread_mutexattr_t$',
                        MutexAttributesPrinter)
    printer.add_printer('pthread_cond_t', r'^pthread_cond_t$',
                        ConditionVariablePrinter)
    printer.add_printer('pthread_condattr_t', r'^pthread_condattr_t$',
                        ConditionVariableAttributesPrinter)
    printer.add_printer('pthread_rwlock_t', r'^pthread_rwlock_t$',
                        RWLockPrinter)
    printer.add_printer('pthread_rwlockattr_t', r'^pthread_rwlockattr_t$',
                        RWLockAttributesPrinter)

    if objfile == None:
        objfile = gdb

    gdb.printing.register_pretty_printer(objfile, printer)

register(gdb.current_objfile())