tools/gdb/gdb_chrome.py

# Copyright 2011 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""GDB support for Chrome types.

Add this to your gdb by amending your ~/.gdbinit as follows:
  python
  import sys
  sys.path.insert(1, "/path/to/tools/gdb/")
  import gdb_chrome
  end

Use
  (gdb) p /r any_variable
to print |any_variable| without using any printers.

To interactively type Python for development of the printers:
  (gdb) python foo = gdb.parse_and_eval('bar')
to put the C++ value 'bar' in the current scope into a Python variable 'foo'.
Then you can interact with that variable:
  (gdb) python print foo['impl_']
"""

import datetime
import gdb
import gdb.printing
import os
import re
import sys

sys.path.insert(
    1, os.path.join(os.path.dirname(os.path.abspath(__file__)), 'util'))
import class_methods

sys.path.insert(
    1,
    os.path.join(
        os.path.dirname(os.path.abspath(__file__)), '..', '..', 'third_party',
        'blink', 'tools', 'gdb'))
try:
  import blink
finally:
  sys.path.pop(1)

# When debugging this module, set the below variable to True, and then use
#   (gdb) python del sys.modules['gdb_chrome']
#   (gdb) python import gdb_chrome
# to reload.
_DEBUGGING = False

pp_set = gdb.printing.RegexpCollectionPrettyPrinter("chromium")


def typed_ptr(ptr):
  """Prints a pointer along with its exact type.

    By default, gdb would print just the address, which takes more
    steps to interpret.
    """
  # Returning this as a cast expression surrounded by parentheses
  # makes it easier to cut+paste inside of gdb.
  return '((%s)%s)' % (ptr.dynamic_type, ptr)


def yield_fields(val):
  """Use this in a printer's children() method to print an object's fields.

    e.g.
      def children():
        for result in yield_fields(self.val):
          yield result
    """
  try:
    fields = val.type.target().fields()
  except:
    fields = val.type.fields()
  for field in fields:
    if field.is_base_class:
      yield (field.name, val.cast(gdb.lookup_type(field.name)))
    else:
      yield (field.name, val[field.name])


class Printer(object):

  def __init__(self, val):
    self.val = val


class StringPrinter(Printer):

  def display_hint(self):
    return 'string'


class String16Printer(StringPrinter):

  def to_string(self):
    return blink.ustring_to_string(self.val['_M_dataplus']['_M_p'])


pp_set.add_printer('string16',
                   '^string16|std::basic_string<(unsigned short|char16_t).*>$',
                   String16Printer)


class GURLPrinter(StringPrinter):

  def to_string(self):
    return self.val['spec_']


pp_set.add_printer('GURL', '^GURL$', GURLPrinter)


class FilePathPrinter(StringPrinter):

  def to_string(self):
    return self.val['path_']['_M_dataplus']['_M_p']


pp_set.add_printer('FilePath', '^FilePath$', FilePathPrinter)


class SmartPtrPrinter(Printer):

  def to_string(self):
    return '%s%s' % (self.typename, typed_ptr(self.ptr()))


class ScopedPtrPrinter(SmartPtrPrinter):
  typename = 'scoped_ptr'

  def ptr(self):
    return self.val['impl_']['data_']['ptr']


pp_set.add_printer('scoped_ptr', '^scoped_ptr<.*>$', ScopedPtrPrinter)


class ScopedRefPtrPrinter(SmartPtrPrinter):
  typename = 'scoped_refptr'

  def ptr(self):
    return self.val['ptr_']


pp_set.add_printer('scoped_refptr', '^scoped_refptr<.*>$', ScopedRefPtrPrinter)


class LinkedPtrPrinter(SmartPtrPrinter):
  typename = 'linked_ptr'

  def ptr(self):
    return self.val['value_']


pp_set.add_printer('linked_ptr', '^linked_ptr<.*>$', LinkedPtrPrinter)


class WeakPtrPrinter(SmartPtrPrinter):
  typename = 'base::WeakPtr'

  def ptr(self):
    # Check that the pointer is valid. The invalidated flag is stored at
    # val.ref_.flag_.ptr_->invalidated_.flag_.__a_.__a_value. This is a gdb
    # implementation of base::WeakReference::IsValid(). This is necessary
    # because calling gdb.parse_and_eval('(*(%s*)(%s)).ref_.IsValid()' %
    # (self.val.type, self.val.address))) does not work in all cases.
    ptr = self.val['ref_']['flag_']['ptr_']
    if (ptr and
        not ptr.dereference()['invalidated_']['flag_']['__a_']['__a_value']):
      return self.val['ptr_']
    return gdb.Value(0).cast(self.val['ptr_'].type)


pp_set.add_printer('base::WeakPtr', '^base::WeakPtr<.*>$', WeakPtrPrinter)


class CallbackPrinter(Printer):
  """Callbacks provide no usable information so reduce the space they take."""

  def to_string(self):
    return '...'


pp_set.add_printer('base::OnceCallback', '^base::OnceCallback<.*>$',
                   CallbackPrinter)
pp_set.add_printer('base::RepeatingCallback', '^base::RepeatingCallback<.*>$',
                   CallbackPrinter)


class LocationPrinter(Printer):

  def to_string(self):
    return '%s()@%s:%s' % (self.val['function_name_'].string(),
                           self.val['file_name_'].string(),
                           self.val['line_number_'])


pp_set.add_printer('base::Location', '^base::Location$', LocationPrinter)


class PendingTaskPrinter(Printer):

  def to_string(self):
    return 'From %s' % (self.val['posted_from'],)

  def children(self):
    for result in yield_fields(self.val):
      if result[0] not in ('task', 'posted_from'):
        yield result


pp_set.add_printer('base::PendingTask', '^base::PendingTask$',
                   PendingTaskPrinter)


class LockPrinter(Printer):

  def to_string(self):
    try:
      if self.val['owned_by_thread_']:
        return 'Locked by thread %s' % self.val['owning_thread_id_']
      else:
        return 'Unlocked'
    except gdb.error:
      return 'Unknown state'


pp_set.add_printer('base::Lock', '^base::Lock$', LockPrinter)


class AbslOptionalPrinter(Printer):

  def to_string(self):
    if self.val['engaged_']:
      return "%s: %s" % (str(self.val.type.tag), self.val['data_'])
    else:
      return "%s: is empty" % str(self.val.type.tag)


pp_set.add_printer('absl::optional', '^absl::optional<.*>$',
                   AbslOptionalPrinter)


class ClampedNumericPrinter(Printer):
  type_re = r'^base::internal::ClampedNumeric<(.*)>$'

  def to_string(self):
    m = type_re.search(self.val.type)
    if m is None:
      return self.val['value']
    return '(%s) %s' % (m.group(1), self.val['value_'])


pp_set.add_printer('base::internal::ClampedNumeric',
                   '^base::internal::ClampedNumeric<.*>$',
                   ClampedNumericPrinter)


class TimeDeltaPrinter(object):

  def __init__(self, val):
    self._timedelta = datetime.timedelta(
        microseconds=int(val['delta_']['value_']))

  def timedelta(self):
    return self._timedelta

  def to_string(self):
    return str(self._timedelta)


pp_set.add_printer('base::TimeDelta', '^base::TimeDelta$', TimeDeltaPrinter)


class TimeTicksPrinter(TimeDeltaPrinter):

  def __init__(self, val):
    self._timedelta = datetime.timedelta(microseconds=int(val['us_']['value_']))


pp_set.add_printer('base::TimeTicks', '^base::TimeTicks$', TimeTicksPrinter)


class TimePrinter(object):

  def __init__(self, val):
    timet_offset = gdb.parse_and_eval('base::Time::kTimeTToMicrosecondsOffset')
    self._datetime = (
        datetime.datetime.fromtimestamp(0) + datetime.timedelta(
            microseconds=int(val['us_']['value_']) - int(timet_offset)))

  def datetime(self):
    return self._datetime

  def to_string(self):
    return str(self._datetime)


pp_set.add_printer('base::Time', '^base::Time$', TimePrinter)


class FlatTreePrinter(object):

  def __init__(self, val):
    self.val = val

  def to_string(self):
    # It would be nice to match the output of std::map which is a little
    # nicer than printing the vector of pairs. But iterating over it in
    # Python is much more complicated and this output is reasonable.
    # (Without this printer, a flat_map will output 7 lines of internal
    # template goop before the vector contents.)
    return 'base::flat_tree with ' + str(self.val['body_'])


pp_set.add_printer('base::flat_map', '^base::flat_map<.*>$', FlatTreePrinter)
pp_set.add_printer('base::flat_set', '^base::flat_set<.*>$', FlatTreePrinter)
pp_set.add_printer('base::flat_tree', '^base::internal::flat_tree<.*>$',
                   FlatTreePrinter)


class ValuePrinter(object):

  def __init__(self, val):
    self.val = val

  def get_type(self):
    return self.val['type_']

  def to_string(self):
    typestr = str(self.get_type())
    # Trim prefix to just get the emum short name.
    typestr = typestr[typestr.rfind(':') + 1:]

    if typestr == 'NONE':
      return 'base::Value of type NONE'
    if typestr == 'BOOLEAN':
      valuestr = self.val['bool_value_']
    if typestr == 'INTEGER':
      valuestr = self.val['int_value_']
    if typestr == 'DOUBLE':
      valuestr = self.val['double_value_']
    if typestr == 'STRING':
      valuestr = self.val['string_value_']
    if typestr == 'BINARY':
      valuestr = self.val['binary_value_']
    if typestr == 'DICTIONARY':
      valuestr = self.val['dict_']
    if typestr == 'LIST':
      valuestr = self.val['list_']

    return "base::Value of type %s = %s" % (typestr, str(valuestr))


pp_set.add_printer('base::Value', '^base::Value$', ValuePrinter)
pp_set.add_printer('base::ListValue', '^base::ListValue$', ValuePrinter)
pp_set.add_printer('base::DictionaryValue', '^base::DictionaryValue$',
                   ValuePrinter)


class IpcMessagePrinter(Printer):

  def header(self):
    return self.val['header_'].cast(
        gdb.lookup_type('IPC::Message::Header').pointer())

  def to_string(self):
    message_type = self.header()['type']
    return '%s of kind %s line %s' % (self.val.dynamic_type,
                                      (message_type >> 16).cast(
                                          gdb.lookup_type('IPCMessageStart')),
                                      message_type & 0xffff)

  def children(self):
    yield ('header_', self.header().dereference())
    yield ('capacity_after_header_', self.val['capacity_after_header_'])
    for field in self.val.type.fields():
      if field.is_base_class:
        continue
      yield (field.name, self.val[field.name])


pp_set.add_printer('IPC::Message', '^IPC::Message$', IpcMessagePrinter)


class NotificationRegistrarPrinter(Printer):

  def to_string(self):
    try:
      registrations = self.val['registered_']
      vector_finish = registrations['_M_impl']['_M_finish']
      vector_start = registrations['_M_impl']['_M_start']
      if vector_start == vector_finish:
        return 'Not watching notifications'
      if vector_start.dereference().type.sizeof == 0:
        # Incomplete type: b/8242773
        return 'Watching some notifications'
      return ('Watching %s notifications; '
              'print %s->registered_ for details') % (int(
                  vector_finish - vector_start), typed_ptr(self.val.address))
    except gdb.error:
      return 'NotificationRegistrar'


pp_set.add_printer('content::NotificationRegistrar',
                   '^content::NotificationRegistrar$',
                   NotificationRegistrarPrinter)


class SiteInstanceImplPrinter(object):

  def __init__(self, val):
    self.val = val.cast(val.dynamic_type)

  def to_string(self):
    return 'SiteInstanceImpl@%s for %s' % (self.val.address, self.val['site_'])

  def children(self):
    yield ('id_', self.val['id_'])
    yield ('has_site_', self.val['has_site_'])
    if self.val['browsing_instance_']['ptr_']:
      yield ('browsing_instance_', self.val['browsing_instance_']['ptr_'])
    if self.val['process_']:
      yield ('process_', typed_ptr(self.val['process_']))


pp_set.add_printer('content::SiteInstanceImpl', '^content::SiteInstanceImpl$',
                   SiteInstanceImplPrinter)


class RenderProcessHostImplPrinter(object):

  def __init__(self, val):
    self.val = val.cast(val.dynamic_type)

  def to_string(self):
    pid = ''
    try:
      child_process_launcher_ptr = (
          self.val['child_process_launcher_']['impl_']['data_']['ptr'])
      if child_process_launcher_ptr:
        context = (child_process_launcher_ptr['context_']['ptr_'])
        if context:
          pid = ' PID %s' % str(context['process_']['process_'])
    except gdb.error:
      # The definition of the Context type may not be available.
      # b/8242773
      pass
    return 'RenderProcessHostImpl@%s%s' % (self.val.address, pid)

  def children(self):
    yield ('id_', self.val['id_'])
    yield ('listeners_', self.val['listeners_']['data_'])
    yield ('worker_ref_count_', self.val['worker_ref_count_'])
    yield ('fast_shutdown_started_', self.val['fast_shutdown_started_'])
    yield ('deleting_soon_', self.val['deleting_soon_'])
    yield ('pending_views_', self.val['pending_views_'])
    yield ('visible_widgets_', self.val['visible_widgets_'])
    yield ('backgrounded_', self.val['backgrounded_'])
    yield ('widget_helper_', self.val['widget_helper_'])
    yield ('is_initialized_', self.val['is_initialized_'])
    yield ('browser_context_', typed_ptr(self.val['browser_context_']))
    yield ('sudden_termination_allowed_',
           self.val['sudden_termination_allowed_'])
    yield ('ignore_input_events_', self.val['ignore_input_events_'])
    yield ('is_guest_', self.val['is_guest_'])


pp_set.add_printer('content::RenderProcessHostImpl',
                   '^content::RenderProcessHostImpl$',
                   RenderProcessHostImplPrinter)


class AtomicPrinter(Printer):
  typename = 'atomic'

  def to_string(self):
    return self.val['__a_']['__a_value']


pp_set.add_printer('std::__Cr::__atomic', '^std::__Cr::(__)?atomic<.*>$',
                   AtomicPrinter)

gdb.printing.register_pretty_printer(gdb, pp_set, replace=_DEBUGGING)
"""Implementations of inlined libc++ std container functions."""


def gdb_running_under_rr():
  try:
    # rr defines the when command to return the current event number.
    gdb.execute('when')

    # If there was no error executing the command, we are running under rr.
    return True
  except gdb.error:
    return False


def find_nearest_frame_matching(frame, predicate):
  while frame and not predicate(frame):
    frame = frame.older()
  return frame


class ReverseCallback(gdb.Command):
  """Find when the currently running callback was created."""

  def __init__(self):
    super(ReverseCallback, self).__init__("reverse-callback", gdb.COMMAND_USER)

  def invoke(self, arg, from_tty):
    if not gdb_running_under_rr():
      raise gdb.error('reverse-callback requires debugging under rr: ' +
                      'https://rr-project.org/')

    # Find the stack frame which extracts the bind state from the task.
    bind_state_frame = find_nearest_frame_matching(
        gdb.selected_frame(),
        lambda frame : frame.function() and
            re.match('^base::internal::Invoker<base::internal::BindState<.*>' +
                     '::RunOnce\(base::internal::BindStateBase\*\)$',
                     frame.function().name))
    if bind_state_frame is None:
      raise Exception(
          'base::internal::Invoker frame not found; are you in a callback?')
    bind_state_frame.select()

    # Disable all existing breakpoints.
    was_enabled = []
    for breakpoint in gdb.breakpoints():
      was_enabled.append(breakpoint.enabled)
      breakpoint.enabled = False

    # Break on the initialization of the BindState.
    storage_address = gdb.parse_and_eval('storage')
    watchpoint = gdb.Breakpoint('*' + str(storage_address), gdb.BP_WATCHPOINT)

    # Find the construction.
    gdb.execute('reverse-continue')

    # Restore breakpoints
    watchpoint.delete()
    for breakpoint, enabled in zip(gdb.breakpoints(), was_enabled):
      breakpoint.enabled = enabled

    # Find the stack frame which created the BindState.
    def in_bindstate(frame):
      return frame.function() and frame.function().name.startswith(
          'base::internal::BindState<')

    creation_frame = find_nearest_frame_matching(
        find_nearest_frame_matching(gdb.selected_frame(), in_bindstate),
        lambda frame: not in_bindstate(frame))

    # The callback creates the bindstate, step up once more to get the creator
    # of the callback.
    creation_frame.older().select()


ReverseCallback()


@class_methods.Class('std::__1::vector', template_types=['T'])
class LibcppVector(object):

  @class_methods.member_function('T&', 'operator[]', ['int'])
  def element(obj, i):
    return obj['__begin_'][i]

  @class_methods.member_function('size_t', 'size', [])
  def size(obj):
    return obj['__end_'] - obj['__begin_']


@class_methods.Class('std::__1::unique_ptr', template_types=['T'])
class LibcppUniquePtr(object):

  @class_methods.member_function('T*', 'get', [])
  def get(obj):
    return obj['__ptr_']['__value_']

  @class_methods.member_function('T*', 'operator->', [])
  def arrow(obj):
    return obj['__ptr_']['__value_']

  @class_methods.member_function('T&', 'operator*', [])
  def dereference(obj):
    return obj['__ptr_']['__value_'].dereference()