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123 lines
4.9 KiB
123 lines
4.9 KiB
#-------------------------------------------------------------------------------
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# elftools: dwarf/locationlists.py
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#
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# DWARF location lists section decoding (.debug_loc)
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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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import os
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from collections import namedtuple
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from ..common.utils import struct_parse
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LocationExpr = namedtuple('LocationExpr', 'loc_expr')
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LocationEntry = namedtuple('LocationEntry', 'begin_offset end_offset loc_expr')
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BaseAddressEntry = namedtuple('BaseAddressEntry', 'base_address')
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class LocationLists(object):
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""" A single location list is a Python list consisting of LocationEntry or
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BaseAddressEntry objects.
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"""
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def __init__(self, stream, structs):
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self.stream = stream
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self.structs = structs
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self._max_addr = 2 ** (self.structs.address_size * 8) - 1
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def get_location_list_at_offset(self, offset):
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""" Get a location list at the given offset in the section.
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"""
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self.stream.seek(offset, os.SEEK_SET)
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return self._parse_location_list_from_stream()
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def iter_location_lists(self):
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""" Yield all location lists found in the section.
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"""
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# Just call _parse_location_list_from_stream until the stream ends
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self.stream.seek(0, os.SEEK_END)
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endpos = self.stream.tell()
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self.stream.seek(0, os.SEEK_SET)
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while self.stream.tell() < endpos:
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yield self._parse_location_list_from_stream()
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#------ PRIVATE ------#
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def _parse_location_list_from_stream(self):
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lst = []
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while True:
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begin_offset = struct_parse(
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self.structs.Dwarf_target_addr(''), self.stream)
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end_offset = struct_parse(
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self.structs.Dwarf_target_addr(''), self.stream)
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if begin_offset == 0 and end_offset == 0:
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# End of list - we're done.
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break
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elif begin_offset == self._max_addr:
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# Base address selection entry
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lst.append(BaseAddressEntry(base_address=end_offset))
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else:
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# Location list entry
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expr_len = struct_parse(
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self.structs.Dwarf_uint16(''), self.stream)
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loc_expr = [struct_parse(self.structs.Dwarf_uint8(''),
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self.stream)
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for i in range(expr_len)]
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lst.append(LocationEntry(
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begin_offset=begin_offset,
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end_offset=end_offset,
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loc_expr=loc_expr))
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return lst
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class LocationParser(object):
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""" A parser for location information in DIEs.
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Handles both location information contained within the attribute
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itself (represented as a LocationExpr object) and references to
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location lists in the .debug_loc section (represented as a
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list).
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"""
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def __init__(self, location_lists):
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self.location_lists = location_lists
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@staticmethod
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def attribute_has_location(attr, dwarf_version):
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""" Checks if a DIE attribute contains location information.
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"""
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return (LocationParser._attribute_is_loclistptr_class(attr) and
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(LocationParser._attribute_has_loc_expr(attr, dwarf_version) or
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LocationParser._attribute_has_loc_list(attr, dwarf_version)))
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def parse_from_attribute(self, attr, dwarf_version):
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""" Parses a DIE attribute and returns either a LocationExpr or
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a list.
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"""
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if self.attribute_has_location(attr, dwarf_version):
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if self._attribute_has_loc_expr(attr, dwarf_version):
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return LocationExpr(attr.value)
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elif self._attribute_has_loc_list(attr, dwarf_version):
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return self.location_lists.get_location_list_at_offset(
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attr.value)
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else:
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raise ValueError("Attribute does not have location information")
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#------ PRIVATE ------#
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@staticmethod
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def _attribute_has_loc_expr(attr, dwarf_version):
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return (dwarf_version < 4 and attr.form == 'DW_FORM_block1' or
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attr.form == 'DW_FORM_exprloc')
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@staticmethod
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def _attribute_has_loc_list(attr, dwarf_version):
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return ((dwarf_version < 4 and
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attr.form in ('DW_FORM_data4', 'DW_FORM_data8')) or
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attr.form == 'DW_FORM_sec_offset')
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@staticmethod
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def _attribute_is_loclistptr_class(attr):
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return (attr.name in ( 'DW_AT_location', 'DW_AT_string_length',
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'DW_AT_const_value', 'DW_AT_return_addr',
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'DW_AT_data_member_location',
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'DW_AT_frame_base', 'DW_AT_segment',
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'DW_AT_static_link', 'DW_AT_use_location',
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'DW_AT_vtable_elem_location'))
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