elftools/dwarf/ranges.py

   1 #-------------------------------------------------------------------------------
   2 # elftools: dwarf/ranges.py
   3 #
   4 # DWARF ranges section decoding (.debug_ranges)
   5 #
   6 # Eli Bendersky (eliben@gmail.com)
   7 # This code is in the public domain
   8 #-------------------------------------------------------------------------------
   9 import os
  10 from collections import namedtuple
  11
  12 from ..common.utils import struct_parse
  13
  14
  15 RangeEntry = namedtuple('RangeEntry', 'entry_offset entry_length begin_offset end_offset is_absolute')
  16 BaseAddressEntry = namedtuple('BaseAddressEntry', 'entry_offset base_address')
  17
  18 def not_implemented(e):
  19     raise NotImplementedError("Range list entry %s is not supported yet" % (e.entry_type,))
  20
  21 # Maps parsed entry types to RangeEntry/BaseAddressEntry objects
  22 entry_translate = {
  23     'DW_RLE_base_address' : lambda e: BaseAddressEntry(e.entry_offset, e.address),
  24     'DW_RLE_offset_pair'  : lambda e: RangeEntry(e.entry_offset, e.entry_length, e.start_offset, e.end_offset, False),
  25     'DW_RLE_start_end'    : lambda e: RangeEntry(e.entry_offset, e.entry_length, e.start_address, e.end_address, True),
  26     'DW_RLE_start_length' : lambda e: RangeEntry(e.entry_offset, e.entry_length, e.start_address, e.start_address + e.length, True),
  27     'DW_RLE_base_addressx': not_implemented,
  28     'DW_RLE_startx_endx'  : not_implemented,
  29     'DW_RLE_startx_length': not_implemented
  30 }
  31
  32 class RangeLists(object):
  33     """ A single range list is a Python list consisting of RangeEntry or
  34         BaseAddressEntry objects.
  35
  36         Since v0.29, two new parameters - version and dwarfinfo
  37
  38         version is used to distinguish DWARFv5 rnglists section from
  39         the DWARF<=4 ranges section. Only the 4/5 distinction matters.
  40
  41         The dwarfinfo is needed for enumeration, because enumeration
  42         requires scanning the DIEs, because ranges may overlap, even on DWARF<=4
  43     """
  44     def __init__(self, stream, structs, version, dwarfinfo):
  45         self.stream = stream
  46         self.structs = structs
  47         self._max_addr = 2 ** (self.structs.address_size * 8) - 1
  48         self.version = version
  49         self._dwarfinfo = dwarfinfo
  50
  51     def get_range_list_at_offset(self, offset):
  52         """ Get a range list at the given offset in the section.
  53         """
  54         self.stream.seek(offset, os.SEEK_SET)
  55         return self._parse_range_list_from_stream()
  56
  57     def iter_range_lists(self):
  58         """ Yield all range lists found in the section.
  59         """
  60         # Calling parse until the stream ends is wrong, because ranges can overlap.
  61         # Need to scan the DIEs to know all range locations
  62         all_offsets = list(set(die.attributes['DW_AT_ranges'].value
  63             for cu in self._dwarfinfo.iter_CUs()
  64             for die in cu.iter_DIEs()
  65             if 'DW_AT_ranges' in die.attributes))
  66         all_offsets.sort()
  67
  68         for offset in all_offsets:
  69             yield self.get_range_list_at_offset(offset)
  70
  71     #------ PRIVATE ------#
  72
  73     def _parse_range_list_from_stream(self):
  74         if self.version >= 5:
  75             return list(entry_translate[entry.entry_type](entry)
  76                 for entry
  77                 in struct_parse(self.structs.Dwarf_rnglists_entries, self.stream))
  78         else:
  79             lst = []
  80             while True:
  81                 entry_offset = self.stream.tell()
  82                 begin_offset = struct_parse(
  83                     self.structs.Dwarf_target_addr(''), self.stream)
  84                 end_offset = struct_parse(
  85                     self.structs.Dwarf_target_addr(''), self.stream)
  86                 if begin_offset == 0 and end_offset == 0:
  87                     # End of list - we're done.
  88                     break
  89                 elif begin_offset == self._max_addr:
  90                     # Base address selection entry
  91                     lst.append(BaseAddressEntry(entry_offset=entry_offset, base_address=end_offset))
  92                 else:
  93                     # Range entry
  94                     lst.append(RangeEntry(
  95                         entry_offset=entry_offset,
  96                         entry_length=self.stream.tell() - entry_offset,
  97                         begin_offset=begin_offset,
  98                         end_offset=end_offset,
  99                         is_absolute=False))
 100             return lst