nptl/nptl-printers.py

   1 # Pretty printers for the NPTL lock types.
   2 #
   3 # Copyright (C) 2016-2022 Free Software Foundation, Inc.
   4 # This file is part of the GNU C Library.
   5 #
   6 # The GNU C Library is free software; you can redistribute it and/or
   7 # modify it under the terms of the GNU Lesser General Public
   8 # License as published by the Free Software Foundation; either
   9 # version 2.1 of the License, or (at your option) any later version.
  10 #
  11 # The GNU C Library is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 # Lesser General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU Lesser General Public
  17 # License along with the GNU C Library; if not, see
  18 # <https://www.gnu.org/licenses/>.
  19
  20 """This file contains the gdb pretty printers for the following types:
  21
  22     * pthread_mutex_t
  23     * pthread_mutexattr_t
  24     * pthread_cond_t
  25     * pthread_condattr_t
  26     * pthread_rwlock_t
  27     * pthread_rwlockattr_t
  28
  29 You can check which printers are registered and enabled by issuing the
  30 'info pretty-printer' gdb command.  Printers should trigger automatically when
  31 trying to print a variable of one of the types mentioned above.
  32 """
  33
  34 from __future__ import print_function
  35
  36 import gdb
  37 import gdb.printing
  38 from nptl_lock_constants import *
  39
  40 MUTEX_TYPES = {
  41     PTHREAD_MUTEX_NORMAL: ('Type', 'Normal'),
  42     PTHREAD_MUTEX_RECURSIVE: ('Type', 'Recursive'),
  43     PTHREAD_MUTEX_ERRORCHECK: ('Type', 'Error check'),
  44     PTHREAD_MUTEX_ADAPTIVE_NP: ('Type', 'Adaptive')
  45 }
  46
  47 class MutexPrinter(object):
  48     """Pretty printer for pthread_mutex_t."""
  49
  50     def __init__(self, mutex):
  51         """Initialize the printer's internal data structures.
  52
  53         Args:
  54             mutex: A gdb.value representing a pthread_mutex_t.
  55         """
  56
  57         data = mutex['__data']
  58         self.lock = data['__lock']
  59         self.count = data['__count']
  60         self.owner = data['__owner']
  61         self.kind = data['__kind']
  62         self.values = []
  63         self.read_values()
  64
  65     def to_string(self):
  66         """gdb API function.
  67
  68         This is called from gdb when we try to print a pthread_mutex_t.
  69         """
  70
  71         return 'pthread_mutex_t'
  72
  73     def children(self):
  74         """gdb API function.
  75
  76         This is called from gdb when we try to print a pthread_mutex_t.
  77         """
  78
  79         return self.values
  80
  81     def read_values(self):
  82         """Read the mutex's info and store it in self.values.
  83
  84         The data contained in self.values will be returned by the Iterator
  85         created in self.children.
  86         """
  87
  88         self.read_type()
  89         self.read_status()
  90         self.read_attributes()
  91         self.read_misc_info()
  92
  93     def read_type(self):
  94         """Read the mutex's type."""
  95
  96         mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK
  97
  98         # mutex_type must be casted to int because it's a gdb.Value
  99         self.values.append(MUTEX_TYPES[int(mutex_type)])
 100
 101     def read_status(self):
 102         """Read the mutex's status.
 103
 104         Architectures that support lock elision might not record the mutex owner
 105         ID in the __owner field.  In that case, the owner will be reported as
 106         "Unknown".
 107         """
 108
 109         if self.kind == PTHREAD_MUTEX_DESTROYED:
 110             self.values.append(('Status', 'Destroyed'))
 111         elif self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
 112             self.read_status_robust()
 113         else:
 114             self.read_status_no_robust()
 115
 116     def read_status_robust(self):
 117         """Read the status of a robust mutex.
 118
 119         In glibc robust mutexes are implemented in a very different way than
 120         non-robust ones.  This method reads their locking status,
 121         whether it may have waiters, their registered owner (if any),
 122         whether the owner is alive or not, and the status of the state
 123         they're protecting.
 124         """
 125
 126         if self.lock == PTHREAD_MUTEX_UNLOCKED:
 127             self.values.append(('Status', 'Not acquired'))
 128         else:
 129             if self.lock & FUTEX_WAITERS:
 130                 self.values.append(('Status',
 131                                     'Acquired, possibly with waiters'))
 132             else:
 133                 self.values.append(('Status',
 134                                     'Acquired, possibly with no waiters'))
 135
 136             if self.lock & FUTEX_OWNER_DIED:
 137                 self.values.append(('Owner ID', '%d (dead)' % self.owner))
 138             else:
 139                 self.values.append(('Owner ID', self.lock & FUTEX_TID_MASK))
 140
 141         if self.owner == PTHREAD_MUTEX_INCONSISTENT:
 142             self.values.append(('State protected by this mutex',
 143                                 'Inconsistent'))
 144         elif self.owner == PTHREAD_MUTEX_NOTRECOVERABLE:
 145             self.values.append(('State protected by this mutex',
 146                                 'Not recoverable'))
 147
 148     def read_status_no_robust(self):
 149         """Read the status of a non-robust mutex.
 150
 151         Read info on whether the mutex is acquired, if it may have waiters
 152         and its owner (if any).
 153         """
 154
 155         lock_value = self.lock
 156
 157         if self.kind & PTHREAD_MUTEX_PRIO_PROTECT_NP:
 158             lock_value &= 0xffffffff & ~(PTHREAD_MUTEX_PRIO_CEILING_MASK)
 159
 160         if lock_value == PTHREAD_MUTEX_UNLOCKED:
 161             self.values.append(('Status', 'Not acquired'))
 162         else:
 163             if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
 164                 waiters = self.lock & FUTEX_WAITERS
 165                 owner = self.lock & FUTEX_TID_MASK
 166             else:
 167                 # Mutex protocol is PP or none
 168                 waiters = (self.lock != PTHREAD_MUTEX_LOCKED_NO_WAITERS)
 169                 owner = self.owner
 170
 171             if waiters:
 172                 self.values.append(('Status',
 173                                     'Acquired, possibly with waiters'))
 174             else:
 175                 self.values.append(('Status',
 176                                     'Acquired, possibly with no waiters'))
 177
 178             if self.owner != 0:
 179                 self.values.append(('Owner ID', owner))
 180             else:
 181                 # Owner isn't recorded, probably because lock elision
 182                 # is enabled.
 183                 self.values.append(('Owner ID', 'Unknown'))
 184
 185     def read_attributes(self):
 186         """Read the mutex's attributes."""
 187
 188         if self.kind != PTHREAD_MUTEX_DESTROYED:
 189             if self.kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP:
 190                 self.values.append(('Robust', 'Yes'))
 191             else:
 192                 self.values.append(('Robust', 'No'))
 193
 194             # In glibc, robust mutexes always have their pshared flag set to
 195             # 'shared' regardless of what the pshared flag of their
 196             # mutexattr was.  Therefore a robust mutex will act as shared
 197             # even if it was initialized with a 'private' mutexattr.
 198             if self.kind & PTHREAD_MUTEX_PSHARED_BIT:
 199                 self.values.append(('Shared', 'Yes'))
 200             else:
 201                 self.values.append(('Shared', 'No'))
 202
 203             if self.kind & PTHREAD_MUTEX_PRIO_INHERIT_NP:
 204                 self.values.append(('Protocol', 'Priority inherit'))
 205             elif self.kind & PTHREAD_MUTEX_PRIO_PROTECT_NP:
 206                 prio_ceiling = ((self.lock & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 207                                 >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT)
 208
 209                 self.values.append(('Protocol', 'Priority protect'))
 210                 self.values.append(('Priority ceiling', prio_ceiling))
 211             else:
 212                 # PTHREAD_PRIO_NONE
 213                 self.values.append(('Protocol', 'None'))
 214
 215     def read_misc_info(self):
 216         """Read miscellaneous info on the mutex.
 217
 218         For now this reads the number of times a recursive mutex was acquired
 219         by the same thread.
 220         """
 221
 222         mutex_type = self.kind & PTHREAD_MUTEX_KIND_MASK
 223
 224         if mutex_type == PTHREAD_MUTEX_RECURSIVE and self.count > 1:
 225             self.values.append(('Times acquired by the owner', self.count))
 226
 227 class MutexAttributesPrinter(object):
 228     """Pretty printer for pthread_mutexattr_t.
 229
 230     In the NPTL this is a type that's always casted to struct pthread_mutexattr
 231     which has a single 'mutexkind' field containing the actual attributes.
 232     """
 233
 234     def __init__(self, mutexattr):
 235         """Initialize the printer's internal data structures.
 236
 237         Args:
 238             mutexattr: A gdb.value representing a pthread_mutexattr_t.
 239         """
 240
 241         self.values = []
 242
 243         try:
 244             mutexattr_struct = gdb.lookup_type('struct pthread_mutexattr')
 245             self.mutexattr = mutexattr.cast(mutexattr_struct)['mutexkind']
 246             self.read_values()
 247         except gdb.error:
 248             # libpthread doesn't have debug symbols, thus we can't find the
 249             # real struct type.  Just print the union members.
 250             self.values.append(('__size', mutexattr['__size']))
 251             self.values.append(('__align', mutexattr['__align']))
 252
 253     def to_string(self):
 254         """gdb API function.
 255
 256         This is called from gdb when we try to print a pthread_mutexattr_t.
 257         """
 258
 259         return 'pthread_mutexattr_t'
 260
 261     def children(self):
 262         """gdb API function.
 263
 264         This is called from gdb when we try to print a pthread_mutexattr_t.
 265         """
 266
 267         return self.values
 268
 269     def read_values(self):
 270         """Read the mutexattr's info and store it in self.values.
 271
 272         The data contained in self.values will be returned by the Iterator
 273         created in self.children.
 274         """
 275
 276         mutexattr_type = (self.mutexattr
 277                           & 0xffffffff
 278                           & ~PTHREAD_MUTEXATTR_FLAG_BITS
 279                           & ~PTHREAD_MUTEX_NO_ELISION_NP)
 280
 281         # mutexattr_type must be casted to int because it's a gdb.Value
 282         self.values.append(MUTEX_TYPES[int(mutexattr_type)])
 283
 284         if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_ROBUST:
 285             self.values.append(('Robust', 'Yes'))
 286         else:
 287             self.values.append(('Robust', 'No'))
 288
 289         if self.mutexattr & PTHREAD_MUTEXATTR_FLAG_PSHARED:
 290             self.values.append(('Shared', 'Yes'))
 291         else:
 292             self.values.append(('Shared', 'No'))
 293
 294         protocol = ((self.mutexattr & PTHREAD_MUTEXATTR_PROTOCOL_MASK) >>
 295                     PTHREAD_MUTEXATTR_PROTOCOL_SHIFT)
 296
 297         if protocol == PTHREAD_PRIO_NONE:
 298             self.values.append(('Protocol', 'None'))
 299         elif protocol == PTHREAD_PRIO_INHERIT:
 300             self.values.append(('Protocol', 'Priority inherit'))
 301         elif protocol == PTHREAD_PRIO_PROTECT:
 302             self.values.append(('Protocol', 'Priority protect'))
 303
 304 class ConditionVariablePrinter(object):
 305     """Pretty printer for pthread_cond_t."""
 306
 307     def __init__(self, cond):
 308         """Initialize the printer's internal data structures.
 309
 310         Args:
 311             cond: A gdb.value representing a pthread_cond_t.
 312         """
 313
 314         data = cond['__data']
 315         self.wrefs = data['__wrefs']
 316         self.values = []
 317
 318         self.read_values()
 319
 320     def to_string(self):
 321         """gdb API function.
 322
 323         This is called from gdb when we try to print a pthread_cond_t.
 324         """
 325
 326         return 'pthread_cond_t'
 327
 328     def children(self):
 329         """gdb API function.
 330
 331         This is called from gdb when we try to print a pthread_cond_t.
 332         """
 333
 334         return self.values
 335
 336     def read_values(self):
 337         """Read the condvar's info and store it in self.values.
 338
 339         The data contained in self.values will be returned by the Iterator
 340         created in self.children.
 341         """
 342
 343         self.read_status()
 344         self.read_attributes()
 345
 346     def read_status(self):
 347         """Read the status of the condvar.
 348
 349         This method reads whether the condvar is destroyed and how many threads
 350         are waiting for it.
 351         """
 352
 353         self.values.append(('Threads known to still execute a wait function',
 354                             self.wrefs >> PTHREAD_COND_WREFS_SHIFT))
 355
 356     def read_attributes(self):
 357         """Read the condvar's attributes."""
 358
 359         if (self.wrefs & PTHREAD_COND_CLOCK_MONOTONIC_MASK) != 0:
 360             self.values.append(('Clock ID', 'CLOCK_MONOTONIC'))
 361         else:
 362             self.values.append(('Clock ID', 'CLOCK_REALTIME'))
 363
 364         if (self.wrefs & PTHREAD_COND_SHARED_MASK) != 0:
 365             self.values.append(('Shared', 'Yes'))
 366         else:
 367             self.values.append(('Shared', 'No'))
 368
 369 class ConditionVariableAttributesPrinter(object):
 370     """Pretty printer for pthread_condattr_t.
 371
 372     In the NPTL this is a type that's always casted to struct pthread_condattr,
 373     which has a single 'value' field containing the actual attributes.
 374     """
 375
 376     def __init__(self, condattr):
 377         """Initialize the printer's internal data structures.
 378
 379         Args:
 380             condattr: A gdb.value representing a pthread_condattr_t.
 381         """
 382
 383         self.values = []
 384
 385         try:
 386             condattr_struct = gdb.lookup_type('struct pthread_condattr')
 387             self.condattr = condattr.cast(condattr_struct)['value']
 388             self.read_values()
 389         except gdb.error:
 390             # libpthread doesn't have debug symbols, thus we can't find the
 391             # real struct type.  Just print the union members.
 392             self.values.append(('__size', condattr['__size']))
 393             self.values.append(('__align', condattr['__align']))
 394
 395     def to_string(self):
 396         """gdb API function.
 397
 398         This is called from gdb when we try to print a pthread_condattr_t.
 399         """
 400
 401         return 'pthread_condattr_t'
 402
 403     def children(self):
 404         """gdb API function.
 405
 406         This is called from gdb when we try to print a pthread_condattr_t.
 407         """
 408
 409         return self.values
 410
 411     def read_values(self):
 412         """Read the condattr's info and store it in self.values.
 413
 414         The data contained in self.values will be returned by the Iterator
 415         created in self.children.
 416         """
 417
 418         clock_id = (self.condattr >> 1) & ((1 << COND_CLOCK_BITS) - 1)
 419
 420         if clock_id != 0:
 421             self.values.append(('Clock ID', 'CLOCK_MONOTONIC'))
 422         else:
 423             self.values.append(('Clock ID', 'CLOCK_REALTIME'))
 424
 425         if self.condattr & 1:
 426             self.values.append(('Shared', 'Yes'))
 427         else:
 428             self.values.append(('Shared', 'No'))
 429
 430 class RWLockPrinter(object):
 431     """Pretty printer for pthread_rwlock_t."""
 432
 433     def __init__(self, rwlock):
 434         """Initialize the printer's internal data structures.
 435
 436         Args:
 437             rwlock: A gdb.value representing a pthread_rwlock_t.
 438         """
 439
 440         data = rwlock['__data']
 441         self.readers = data['__readers']
 442         self.cur_writer = data['__cur_writer']
 443         self.shared = data['__shared']
 444         self.flags = data['__flags']
 445         self.values = []
 446         self.read_values()
 447
 448     def to_string(self):
 449         """gdb API function.
 450
 451         This is called from gdb when we try to print a pthread_rwlock_t.
 452         """
 453
 454         return 'pthread_rwlock_t'
 455
 456     def children(self):
 457         """gdb API function.
 458
 459         This is called from gdb when we try to print a pthread_rwlock_t.
 460         """
 461
 462         return self.values
 463
 464     def read_values(self):
 465         """Read the rwlock's info and store it in self.values.
 466
 467         The data contained in self.values will be returned by the Iterator
 468         created in self.children.
 469         """
 470
 471         self.read_status()
 472         self.read_attributes()
 473
 474     def read_status(self):
 475         """Read the status of the rwlock."""
 476
 477         if self.readers & PTHREAD_RWLOCK_WRPHASE:
 478             if self.readers & PTHREAD_RWLOCK_WRLOCKED:
 479                 self.values.append(('Status', 'Acquired (Write)'))
 480                 self.values.append(('Writer ID', self.cur_writer))
 481             else:
 482                 self.values.append(('Status', 'Not acquired'))
 483         else:
 484             r = self.readers >> PTHREAD_RWLOCK_READER_SHIFT
 485             if r > 0:
 486                 self.values.append(('Status', 'Acquired (Read)'))
 487                 self.values.append(('Readers', r))
 488             else:
 489                 self.values.append(('Status', 'Not acquired'))
 490
 491     def read_attributes(self):
 492         """Read the attributes of the rwlock."""
 493
 494         if self.shared:
 495             self.values.append(('Shared', 'Yes'))
 496         else:
 497             self.values.append(('Shared', 'No'))
 498
 499         if self.flags == PTHREAD_RWLOCK_PREFER_READER_NP:
 500             self.values.append(('Prefers', 'Readers'))
 501         elif self.flags == PTHREAD_RWLOCK_PREFER_WRITER_NP:
 502             self.values.append(('Prefers', 'Writers'))
 503         else:
 504             self.values.append(('Prefers', 'Writers no recursive readers'))
 505
 506 class RWLockAttributesPrinter(object):
 507     """Pretty printer for pthread_rwlockattr_t.
 508
 509     In the NPTL this is a type that's always casted to
 510     struct pthread_rwlockattr, which has two fields ('lockkind' and 'pshared')
 511     containing the actual attributes.
 512     """
 513
 514     def __init__(self, rwlockattr):
 515         """Initialize the printer's internal data structures.
 516
 517         Args:
 518             rwlockattr: A gdb.value representing a pthread_rwlockattr_t.
 519         """
 520
 521         self.values = []
 522
 523         try:
 524             rwlockattr_struct = gdb.lookup_type('struct pthread_rwlockattr')
 525             self.rwlockattr = rwlockattr.cast(rwlockattr_struct)
 526             self.read_values()
 527         except gdb.error:
 528             # libpthread doesn't have debug symbols, thus we can't find the
 529             # real struct type.  Just print the union members.
 530             self.values.append(('__size', rwlockattr['__size']))
 531             self.values.append(('__align', rwlockattr['__align']))
 532
 533     def to_string(self):
 534         """gdb API function.
 535
 536         This is called from gdb when we try to print a pthread_rwlockattr_t.
 537         """
 538
 539         return 'pthread_rwlockattr_t'
 540
 541     def children(self):
 542         """gdb API function.
 543
 544         This is called from gdb when we try to print a pthread_rwlockattr_t.
 545         """
 546
 547         return self.values
 548
 549     def read_values(self):
 550         """Read the rwlockattr's info and store it in self.values.
 551
 552         The data contained in self.values will be returned by the Iterator
 553         created in self.children.
 554         """
 555
 556         rwlock_type = self.rwlockattr['lockkind']
 557         shared = self.rwlockattr['pshared']
 558
 559         if shared == PTHREAD_PROCESS_SHARED:
 560             self.values.append(('Shared', 'Yes'))
 561         else:
 562             # PTHREAD_PROCESS_PRIVATE
 563             self.values.append(('Shared', 'No'))
 564
 565         if rwlock_type == PTHREAD_RWLOCK_PREFER_READER_NP:
 566             self.values.append(('Prefers', 'Readers'))
 567         elif rwlock_type == PTHREAD_RWLOCK_PREFER_WRITER_NP:
 568             self.values.append(('Prefers', 'Writers'))
 569         else:
 570             self.values.append(('Prefers', 'Writers no recursive readers'))
 571
 572 def register(objfile):
 573     """Register the pretty printers within the given objfile."""
 574
 575     printer = gdb.printing.RegexpCollectionPrettyPrinter('glibc-pthread-locks')
 576
 577     printer.add_printer('pthread_mutex_t', r'^pthread_mutex_t$',
 578                         MutexPrinter)
 579     printer.add_printer('pthread_mutexattr_t', r'^pthread_mutexattr_t$',
 580                         MutexAttributesPrinter)
 581     printer.add_printer('pthread_cond_t', r'^pthread_cond_t$',
 582                         ConditionVariablePrinter)
 583     printer.add_printer('pthread_condattr_t', r'^pthread_condattr_t$',
 584                         ConditionVariableAttributesPrinter)
 585     printer.add_printer('pthread_rwlock_t', r'^pthread_rwlock_t$',
 586                         RWLockPrinter)
 587     printer.add_printer('pthread_rwlockattr_t', r'^pthread_rwlockattr_t$',
 588                         RWLockAttributesPrinter)
 589
 590     if objfile == None:
 591         objfile = gdb
 592
 593     gdb.printing.register_pretty_printer(objfile, printer)
 594
 595 register(gdb.current_objfile())