Add pretty printers for the NPTL lock types

This patch adds pretty printers for the following NPTL types:

- pthread_mutex_t
- pthread_mutexattr_t
- pthread_cond_t
- pthread_condattr_t
- pthread_rwlock_t
- pthread_rwlockattr_t

To load the pretty printers into your gdb session, do the following:

python
import sys
sys.path.insert(0, '/path/to/glibc/build/nptl/pretty-printers')
end

source /path/to/glibc/source/pretty-printers/nptl-printers.py

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.

The printers are architecture-independent, and were manually tested on both
the gdb CLI and Eclipse CDT.

In order to work, the printers need to know the values of various flags that
are scattered throughout pthread.h and pthreadP.h as enums and #defines. Since
replicating these constants in the printers file itself would create a
maintenance burden, I wrote a script called gen-py-const.awk that Makerules uses
to extract the constants. This script is pretty much the same as gen-as-const.awk,
except it doesn't cast the constant values to 'long' and is thorougly documented.
The constants need only to be enumerated in a .pysym file, which is then referenced
by a Make variable called gen-py-const-headers.

As for the install directory, I discussed this with Mike Frysinger and Siddhesh
Poyarekar, and we agreed that it can be handled in a separate patch, and it shouldn't
block merging of this one.

In addition, I've written a series of test cases for the pretty printers.
Each lock type (mutex, condvar and rwlock) has two test programs, one for itself
and other for its related 'attributes' object. Each test program in turn has a
PExpect-based Python script that drives gdb and compares its output to the
expected printer's. The tests run on the glibc host, which is assumed to have
both gdb and PExpect; if either is absent the tests will fail with code 77
(UNSUPPORTED). For cross-testing you should use cross-test-ssh.sh as test-wrapper.
I've tested the printers on both a native build and a cross build using a Beaglebone
Black, with the build system's filesystem shared with the board through NFS.

Finally, I've written a README that explains all this and more.

Hopefully this should be good to go in now. Thanks.

ChangeLog:

2016-07-04  Martin Galvan  <martin.galvan@tallertechnologies.com>

	* Makeconfig (build-hardcoded-path-in-tests): Set to 'yes' for shared builds
	if tests-need-hardcoded-path is defined.
	(all-subdirs): Add pretty-printers.
	* Makerules ($(py-const)): New rule.
	* Rules (others): Add $(py-const), if defined.
	* nptl/Makefile (gen-py-const-headers): Define.
	* nptl/nptl-printers.py: New file.
	* nptl/nptl_lock_constants.pysym: Likewise.
	* pretty-printers/Makefile: Likewise.
	* pretty-printers/README: Likewise.
	* pretty-printers/test-condvar-attributes.c: Likewise.
	* pretty-printers/test-condvar-attributes.p: Likewise.
	* pretty-printers/test-condvar-printer.c: Likewise.
	* pretty-printers/test-condvar-printer.py: Likewise.
	* pretty-printers/test-mutex-attributes.c: Likewise.
	* pretty-printers/test-mutex-attributes.py: Likewise.
	* pretty-printers/test-mutex-printer.c: Likewise.
	* pretty-printers/test-mutex-printer.py: Likewise.
	* pretty-printers/test-rwlock-attributes.c: Likewise.
	* pretty-printers/test-rwlock-attributes.py: Likewise.
	* pretty-printers/test-rwlock-printer.c: Likewise.
	* pretty-printers/test-rwlock-printer.py: Likewise.
	* pretty-printers/test_common.py: Likewise.
	* scripts/gen-py-const.awk: Likewise.

1 files changed, 593 insertions, 0 deletions

diff --git a/nptl/nptl-printers.py b/nptl/nptl-printers.py
new file mode 100644
index 0000000000..f64216fb57
--- /dev/null
+++ b/nptl/nptl-printers.py
@@ -0,0 +1,593 @@
+# 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
+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.
+        """
+
+        mutexattr_struct = gdb.lookup_type('struct pthread_mutexattr')
+        self.mutexattr = mutexattr.cast(mutexattr_struct)['mutexkind']
+        self.values = []
+        self.read_values()
+
+    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.
+        """
+
+        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 == PTHREAD_COND_SHARED)
+
+        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 value of ~0l instead.
+        """
+
+        if self.mutex and self.mutex != PTHREAD_COND_SHARED:
+            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.
+        """
+
+        condattr_struct = gdb.lookup_type('struct pthread_condattr')
+        self.condattr = condattr.cast(condattr_struct)['value']
+        self.values = []
+        self.read_values()
+
+    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.
+        """
+
+        rwlockattr_struct = gdb.lookup_type('struct pthread_rwlockattr')
+        self.rwlockattr = rwlockattr.cast(rwlockattr_struct)
+        self.values = []
+        self.read_values()
+
+    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)
+
+    gdb.printing.register_pretty_printer(objfile, printer)
+
+register(gdb.current_objfile())