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#-------------------------------------------------------------------------------
# elftools: elf/dynamic.py
#
# ELF Dynamic Tags
#
# Mike Frysinger (vapier@gentoo.org)
# This code is in the public domain
#-------------------------------------------------------------------------------
import itertools
from .sections import Section
from .segments import Segment
from ..common.utils import struct_parse
from enums import ENUM_D_TAG
class DynamicTag(object):
""" Dynamic Tag object - representing a single dynamic tag entry from a
dynamic section.
Similarly to Section objects, allows dictionary-like access to the
dynamic tag.
"""
_HANDLED_TAGS = frozenset(['DT_NEEDED', 'DT_RPATH', 'DT_RUNPATH'])
def __init__(self, entry, elffile):
self.entry = entry
if entry.d_tag in self._HANDLED_TAGS:
dynstr = elffile.get_section_by_name('.dynstr')
setattr(self, entry.d_tag[3:].lower(), dynstr.get_string(self.entry.d_val))
def __getitem__(self, name):
""" Implement dict-like access to entries
"""
return self.entry[name]
def __repr__(self):
return '<DynamicTag (%s): %r>' % (self.entry.d_tag, self.entry)
def __str__(self):
if self.entry.d_tag in self._HANDLED_TAGS:
s = '"%s"' % getattr(self, self.entry.d_tag[3:].lower())
else:
s = '%#x' % self.entry.d_ptr
return '<DynamicTag (%s) %s>' % (self.entry.d_tag, s)
class Dynamic(object):
def __init__(self, stream, elffile, position):
self._stream = stream
self._elffile = elffile
self._elfstructs = elffile.structs
self._num_tags = -1;
self._offset = position
self._tagsize = self._elfstructs.Elf_Dyn.sizeof()
def iter_tags(self, type=None):
""" Yield all tags (limit to |type| if specified)
"""
for n in itertools.count():
tag = self.get_tag(n)
if type is None or tag.entry.d_tag == type:
yield tag
if tag.entry.d_tag == 'DT_NULL':
break
def get_tag(self, n):
""" Get the tag at index #n from the file (DynamicTag object)
"""
offset = self._offset + n * self._tagsize
entry = struct_parse(
self._elfstructs.Elf_Dyn,
self._stream,
stream_pos=offset)
return DynamicTag(entry, self._elffile)
@property
def num_tags(self):
""" Number of dynamic tags in the file
"""
if self._num_tags != -1:
return self._num_tags
for n in itertools.count():
tag = self.get_tag(n)
if tag.entry.d_tag == 'DT_NULL':
self._num_tags = n
return n
class DynamicSection(Section, Dynamic):
""" ELF dynamic table section. Knows how to process the list of tags.
"""
def __init__(self, header, name, stream, elffile):
Section.__init__(self, header, name, stream)
Dynamic.__init__(self, stream, elffile, self['sh_offset'])
class DynamicSegment(Segment, Dynamic):
""" ELF dynamic table segment. Knows how to process the list of tags.
"""
def __init__(self, header, stream, elffile):
Segment.__init__(self, header, stream)
Dynamic.__init__(self, stream, elffile, self['p_offset'])
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