blob: 62896189c1e717f7c3fa645e04dc50f175fe2553 [file] [log] [blame]
# elftools example:
# Examine DIE entries which have location list values, and decode these
# location lists.
# Eli Bendersky (
# This code is in the public domain
from __future__ import print_function
import sys
# If elftools is not installed, maybe we're running from the root or examples
# dir of the source distribution
import elftools
except ImportError:
sys.path.extend(['.', '..'])
from elftools.common.py3compat import itervalues
from elftools.elf.elffile import ELFFile
from elftools.dwarf.descriptions import (
describe_DWARF_expr, set_global_machine_arch)
from elftools.dwarf.locationlists import LocationEntry
def process_file(filename):
print('Processing file:', filename)
with open(filename, 'rb') as f:
elffile = ELFFile(f)
if not elffile.has_dwarf_info():
print(' file has no DWARF info')
# get_dwarf_info returns a DWARFInfo context object, which is the
# starting point for all DWARF-based processing in pyelftools.
dwarfinfo = elffile.get_dwarf_info()
# The location lists are extracted by DWARFInfo from the .debug_loc
# section, and returned here as a LocationLists object.
location_lists = dwarfinfo.location_lists()
# This is required for the descriptions module to correctly decode
# register names contained in DWARF expressions.
for CU in dwarfinfo.iter_CUs():
# DWARFInfo allows to iterate over the compile units contained in
# the .debug_info section. CU is a CompileUnit object, with some
# computed attributes (such as its offset in the section) and
# a header which conforms to the DWARF standard. The access to
# header elements is, as usual, via item-lookup.
print(' Found a compile unit at offset %s, length %s' % (
CU.cu_offset, CU['unit_length']))
# A CU provides a simple API to iterate over all the DIEs in it.
for DIE in CU.iter_DIEs():
# Go over all attributes of the DIE. Each attribute is an
# AttributeValue object (from elftools.dwarf.die), which we
# can examine.
for attr in itervalues(DIE.attributes):
if attribute_has_location_list(attr):
# This is a location list. Its value is an offset into
# the .debug_loc section, so we can use the location
# lists object to decode it.
loclist = location_lists.get_location_list_at_offset(
print(' DIE %s. attr %s.\n%s' % (
show_loclist(loclist, dwarfinfo, indent=' ')))
def show_loclist(loclist, dwarfinfo, indent):
""" Display a location list nicely, decoding the DWARF expressions
contained within.
d = []
for loc_entity in loclist:
if isinstance(loc_entity, LocationEntry):
d.append('%s <<%s>>' % (
describe_DWARF_expr(loc_entity.loc_expr, dwarfinfo.structs)))
return '\n'.join(indent + s for s in d)
def attribute_has_location_list(attr):
""" Only some attributes can have location list values, if they have the
required DW_FORM (loclistptr "class" in DWARF spec v3)
if ( in ( 'DW_AT_location', 'DW_AT_string_length',
'DW_AT_const_value', 'DW_AT_return_addr',
'DW_AT_data_member_location', 'DW_AT_frame_base',
'DW_AT_segment', 'DW_AT_static_link',
'DW_AT_use_location', 'DW_AT_vtable_elem_location')):
if attr.form in ('DW_FORM_data4', 'DW_FORM_data8'):
return True
return False
if __name__ == '__main__':
for filename in sys.argv[1:]: