src/third_party/pyelftools/elftools/elf/dynamic.py

   1 #-------------------------------------------------------------------------------
   2 # elftools: elf/dynamic.py
   3 #
   4 # ELF Dynamic Tags
   5 #
   6 # Mike Frysinger (vapier@gentoo.org)
   7 # This code is in the public domain
   8 #-------------------------------------------------------------------------------
   9 import itertools
  10
  11 from .sections import Section
  12 from .segments import Segment
  13 from ..common.utils import struct_parse
  14
  15 from enums import ENUM_D_TAG
  16
  17
  18 class DynamicTag(object):
  19     """ Dynamic Tag object - representing a single dynamic tag entry from a
  20         dynamic section.
  21
  22         Similarly to Section objects, allows dictionary-like access to the
  23         dynamic tag.
  24     """
  25
  26     _HANDLED_TAGS = frozenset(['DT_NEEDED', 'DT_RPATH', 'DT_RUNPATH'])
  27
  28     def __init__(self, entry, elffile):
  29         self.entry = entry
  30         if entry.d_tag in self._HANDLED_TAGS:
  31             dynstr = elffile.get_section_by_name('.dynstr')
  32             setattr(self, entry.d_tag[3:].lower(), dynstr.get_string(self.entry.d_val))
  33
  34     def __getitem__(self, name):
  35         """ Implement dict-like access to entries
  36         """
  37         return self.entry[name]
  38
  39     def __repr__(self):
  40         return '<DynamicTag (%s): %r>' % (self.entry.d_tag, self.entry)
  41
  42     def __str__(self):
  43         if self.entry.d_tag in self._HANDLED_TAGS:
  44             s = '"%s"' % getattr(self, self.entry.d_tag[3:].lower())
  45         else:
  46             s = '%#x' % self.entry.d_ptr
  47         return '<DynamicTag (%s) %s>' % (self.entry.d_tag, s)
  48
  49
  50 class Dynamic(object):
  51     def __init__(self, stream, elffile, position):
  52         self._stream = stream
  53         self._elffile = elffile
  54         self._elfstructs = elffile.structs
  55         self._num_tags = -1;
  56         self._offset = position
  57         self._tagsize = self._elfstructs.Elf_Dyn.sizeof()
  58
  59     def iter_tags(self, type=None):
  60         """ Yield all tags (limit to |type| if specified)
  61         """
  62         for n in itertools.count():
  63             tag = self.get_tag(n)
  64             if type is None or tag.entry.d_tag == type:
  65                 yield tag
  66             if tag.entry.d_tag == 'DT_NULL':
  67                 break
  68
  69     def get_tag(self, n):
  70         """ Get the tag at index #n from the file (DynamicTag object)
  71         """
  72         offset = self._offset + n * self._tagsize
  73         entry = struct_parse(
  74             self._elfstructs.Elf_Dyn,
  75             self._stream,
  76             stream_pos=offset)
  77         return DynamicTag(entry, self._elffile)
  78
  79     @property
  80     def num_tags(self):
  81         """ Number of dynamic tags in the file
  82         """
  83         if self._num_tags != -1:
  84             return self._num_tags
  85
  86         for n in itertools.count():
  87             tag = self.get_tag(n)
  88             if tag.entry.d_tag == 'DT_NULL':
  89                 self._num_tags = n
  90                 return n
  91
  92
  93 class DynamicSection(Section, Dynamic):
  94     """ ELF dynamic table section.  Knows how to process the list of tags.
  95     """
  96     def __init__(self, header, name, stream, elffile):
  97         Section.__init__(self, header, name, stream)
  98         Dynamic.__init__(self, stream, elffile, self['sh_offset'])
  99
 100
 101 class DynamicSegment(Segment, Dynamic):
 102     """ ELF dynamic table segment.  Knows how to process the list of tags.
 103     """
 104     def __init__(self, header, stream, elffile):
 105         Segment.__init__(self, header, stream)
 106         Dynamic.__init__(self, stream, elffile, self['p_offset'])