0ec9933f5113b29dbda6c678768659cfdcb55dbc
1 #-------------------------------------------------------------------------------
2 # elftools example: dwarf_location_info.py
4 # Examine DIE entries which have either location list values or location
5 # expression values and decode that information.
7 # Location information can either be completely contained within a DIE
8 # (using 'DW_FORM_exprloc' in DWARFv4 or 'DW_FORM_block1' in earlier
9 # versions) or be a reference to a location list contained within
10 # the .debug_loc section (using 'DW_FORM_sec_offset' in DWARFv4 or
11 # 'DW_FORM_data4' / 'DW_FORM_data8' in earlier versions).
13 # The LocationParser object parses the DIE attributes and handles both
16 # The directory 'test/testfiles_for_location_info' contains test files with
17 # location information represented in both DWARFv4 and DWARFv2 forms.
19 # Eli Bendersky (eliben@gmail.com)
20 # This code is in the public domain
21 #-------------------------------------------------------------------------------
22 from __future__
import print_function
25 # If pyelftools is not installed, the example can also run from the root or
26 # examples/ dir of the source distribution.
27 sys
.path
[0:0] = ['.', '..']
29 from elftools
.common
.py3compat
import itervalues
30 from elftools
.elf
.elffile
import ELFFile
31 from elftools
.dwarf
.descriptions
import (
32 describe_DWARF_expr
, set_global_machine_arch
)
33 from elftools
.dwarf
.locationlists
import (
34 LocationEntry
, LocationExpr
, LocationParser
)
36 def process_file(filename
):
37 print('Processing file:', filename
)
38 with
open(filename
, 'rb') as f
:
41 if not elffile
.has_dwarf_info():
42 print(' file has no DWARF info')
45 # get_dwarf_info returns a DWARFInfo context object, which is the
46 # starting point for all DWARF-based processing in pyelftools.
47 dwarfinfo
= elffile
.get_dwarf_info()
49 # The location lists are extracted by DWARFInfo from the .debug_loc
50 # section, and returned here as a LocationLists object.
51 location_lists
= dwarfinfo
.location_lists()
53 # This is required for the descriptions module to correctly decode
54 # register names contained in DWARF expressions.
55 set_global_machine_arch(elffile
.get_machine_arch())
57 # Create a LocationParser object that parses the DIE attributes and
58 # creates objects representing the actual location information.
59 loc_parser
= LocationParser(location_lists
)
61 for CU
in dwarfinfo
.iter_CUs():
62 # DWARFInfo allows to iterate over the compile units contained in
63 # the .debug_info section. CU is a CompileUnit object, with some
64 # computed attributes (such as its offset in the section) and
65 # a header which conforms to the DWARF standard. The access to
66 # header elements is, as usual, via item-lookup.
67 print(' Found a compile unit at offset %s, length %s' % (
68 CU
.cu_offset
, CU
['unit_length']))
70 # A CU provides a simple API to iterate over all the DIEs in it.
71 for DIE
in CU
.iter_DIEs():
72 # Go over all attributes of the DIE. Each attribute is an
73 # AttributeValue object (from elftools.dwarf.die), which we
75 for attr
in itervalues(DIE
.attributes
):
76 # Check if this attribute contains location information
77 if loc_parser
.attribute_has_location(attr
, CU
['version']):
78 print(' DIE %s. attr %s.' % (DIE
.tag
, attr
.name
))
79 loc
= loc_parser
.parse_from_attribute(attr
,
81 # We either get a list (in case the attribute is a
82 # reference to the .debug_loc section) or a LocationExpr
83 # object (in case the attribute itself contains location
85 if isinstance(loc
, LocationExpr
):
87 describe_DWARF_expr(loc
.loc_expr
,
88 dwarfinfo
.structs
, CU
.cu_offset
)))
89 elif isinstance(loc
, list):
90 print(show_loclist(loc
,
94 def show_loclist(loclist
, dwarfinfo
, indent
, cu_offset
):
95 """ Display a location list nicely, decoding the DWARF expressions
99 for loc_entity
in loclist
:
100 if isinstance(loc_entity
, LocationEntry
):
101 d
.append('%s <<%s>>' % (
103 describe_DWARF_expr(loc_entity
.loc_expr
, dwarfinfo
.structs
, cu_offset
)))
105 d
.append(str(loc_entity
))
106 return '\n'.join(indent
+ s
for s
in d
)
108 if __name__
== '__main__':
109 if sys
.argv
[1] == '--test':
110 for filename
in sys
.argv
[2:]:
111 process_file(filename
)