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218 lines
7.3 KiB
218 lines
7.3 KiB
#-------------------------------------------------------------------------------
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# elftools: dwarf/die.py
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#
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# DWARF Debugging Information Entry
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#
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# Eli Bendersky (eliben@gmail.com)
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# This code is in the public domain
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#-------------------------------------------------------------------------------
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from collections import namedtuple, OrderedDict
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import os
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from ..common.exceptions import DWARFError
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from ..common.py3compat import bytes2str, iteritems
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from ..common.utils import struct_parse, preserve_stream_pos
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from .enums import DW_FORM_raw2name
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# AttributeValue - describes an attribute value in the DIE:
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#
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# name:
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# The name (DW_AT_*) of this attribute
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#
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# form:
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# The DW_FORM_* name of this attribute
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#
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# value:
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# The value parsed from the section and translated accordingly to the form
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# (e.g. for a DW_FORM_strp it's the actual string taken from the string table)
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#
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# raw_value:
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# Raw value as parsed from the section - used for debugging and presentation
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# (e.g. for a DW_FORM_strp it's the raw string offset into the table)
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#
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# offset:
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# Offset of this attribute's value in the stream (absolute offset, relative
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# the beginning of the whole stream)
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#
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AttributeValue = namedtuple(
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'AttributeValue', 'name form value raw_value offset')
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class DIE(object):
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""" A DWARF debugging information entry. On creation, parses itself from
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the stream. Each DIE is held by a CU.
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Accessible attributes:
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tag:
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The DIE tag
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size:
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The size this DIE occupies in the section
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offset:
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The offset of this DIE in the stream
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attributes:
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An ordered dictionary mapping attribute names to values. It's
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ordered to preserve the order of attributes in the section
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has_children:
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Specifies whether this DIE has children
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abbrev_code:
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The abbreviation code pointing to an abbreviation entry (note
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that this is for informational pusposes only - this object
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interacts with its abbreviation table transparently).
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See also the public methods.
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"""
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def __init__(self, cu, stream, offset):
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""" cu:
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CompileUnit object this DIE belongs to. Used to obtain context
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information (structs, abbrev table, etc.)
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stream, offset:
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The stream and offset into it where this DIE's data is located
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"""
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self.cu = cu
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self.dwarfinfo = self.cu.dwarfinfo # get DWARFInfo context
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self.stream = stream
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self.offset = offset
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self.attributes = OrderedDict()
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self.tag = None
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self.has_children = None
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self.abbrev_code = None
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self.size = 0
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# Null DIE terminator. It can be used to obtain offset range occupied
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# by this DIE including its whole subtree.
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self._terminator = None
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self._parent = None
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self._parse_DIE()
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def is_null(self):
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""" Is this a null entry?
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"""
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return self.tag is None
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def get_parent(self):
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""" The parent DIE of this DIE. None if the DIE has no parent (i.e. a
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top-level DIE).
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"""
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return self._parent
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def get_full_path(self):
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""" Return the full path filename for the DIE.
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The filename is the join of 'DW_AT_comp_dir' and 'DW_AT_name',
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either of which may be missing in practice. Note that its value is
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usually a string taken from the .debug_string section and the
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returned value will be a string.
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"""
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comp_dir_attr = self.attributes.get('DW_AT_comp_dir', None)
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comp_dir = bytes2str(comp_dir_attr.value) if comp_dir_attr else ''
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fname_attr = self.attributes.get('DW_AT_name', None)
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fname = bytes2str(fname_attr.value) if fname_attr else ''
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return os.path.join(comp_dir, fname)
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def iter_children(self):
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""" Iterates all children of this DIE
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"""
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return self.cu.iter_DIE_children(self)
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def iter_siblings(self):
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""" Yield all siblings of this DIE
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"""
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if self._parent:
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for sibling in self._parent.iter_children():
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if sibling is not self:
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yield sibling
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else:
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raise StopIteration()
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# The following methods are used while creating the DIE and should not be
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# interesting to consumers
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#
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def set_parent(self, die):
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self._parent = die
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#------ PRIVATE ------#
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def __repr__(self):
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s = 'DIE %s, size=%s, has_children=%s\n' % (
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self.tag, self.size, self.has_children)
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for attrname, attrval in iteritems(self.attributes):
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s += ' |%-18s: %s\n' % (attrname, attrval)
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return s
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def __str__(self):
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return self.__repr__()
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def _parse_DIE(self):
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""" Parses the DIE info from the section, based on the abbreviation
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table of the CU
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"""
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structs = self.cu.structs
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# A DIE begins with the abbreviation code. Read it and use it to
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# obtain the abbrev declaration for this DIE.
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# Note: here and elsewhere, preserve_stream_pos is used on operations
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# that manipulate the stream by reading data from it.
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self.abbrev_code = struct_parse(
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structs.Dwarf_uleb128(''), self.stream, self.offset)
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# This may be a null entry
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if self.abbrev_code == 0:
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self.size = self.stream.tell() - self.offset
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return
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abbrev_decl = self.cu.get_abbrev_table().get_abbrev(self.abbrev_code)
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self.tag = abbrev_decl['tag']
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self.has_children = abbrev_decl.has_children()
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# Guided by the attributes listed in the abbreviation declaration, parse
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# values from the stream.
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for name, form in abbrev_decl.iter_attr_specs():
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attr_offset = self.stream.tell()
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raw_value = struct_parse(structs.Dwarf_dw_form[form], self.stream)
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value = self._translate_attr_value(form, raw_value)
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self.attributes[name] = AttributeValue(
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name=name,
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form=form,
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value=value,
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raw_value=raw_value,
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offset=attr_offset)
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self.size = self.stream.tell() - self.offset
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def _translate_attr_value(self, form, raw_value):
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""" Translate a raw attr value according to the form
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"""
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value = None
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if form == 'DW_FORM_strp':
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with preserve_stream_pos(self.stream):
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value = self.dwarfinfo.get_string_from_table(raw_value)
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elif form == 'DW_FORM_flag':
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value = not raw_value == 0
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elif form == 'DW_FORM_flag_present':
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value = True
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elif form == 'DW_FORM_indirect':
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try:
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form = DW_FORM_raw2name[raw_value]
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except KeyError as err:
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raise DWARFError(
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'Found DW_FORM_indirect with unknown raw_value=' +
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str(raw_value))
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raw_value = struct_parse(
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self.cu.structs.Dwarf_dw_form[form], self.stream)
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# Let's hope this doesn't get too deep :-)
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return self._translate_attr_value(form, raw_value)
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else:
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value = raw_value
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return value
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