1 #-------------------------------------------------------------------------------
2 # elftools: dwarf/dwarfinfo.py
4 # DWARFInfo - Main class for accessing DWARF debug information
6 # Eli Bendersky (eliben@gmail.com)
7 # This code is in the public domain
8 #-------------------------------------------------------------------------------
9 from collections
import namedtuple
11 from ..common
.exceptions
import DWARFError
12 from ..common
.utils
import (struct_parse
, dwarf_assert
,
13 parse_cstring_from_stream
)
14 from .structs
import DWARFStructs
15 from .compileunit
import CompileUnit
16 from .abbrevtable
import AbbrevTable
17 from .lineprogram
import LineProgram
20 # Describes a debug section
22 # stream: a stream object containing the data of this section
23 # name: section name in the container file
24 # global_offset: the global offset of the section in its container file
25 # size: the size of the section's data, in bytes
27 DebugSectionDescriptor
= namedtuple('DebugSectionDescriptor',
28 'stream name global_offset size')
31 class DWARFInfo(object):
32 """ Acts also as a "context" to other major objects, bridging between
33 various parts of the debug infromation.
42 A stream (file-like object) that contains debug sections
48 DebugSectionDescriptor for a section
50 self
.elffile
= elffile
51 self
.debug_info_sec
= debug_info_sec
52 self
.debug_abbrev_sec
= debug_abbrev_sec
53 self
.debug_str_sec
= debug_str_sec
54 self
.debug_line_sec
= debug_line_sec
56 self
.little_endian
= self
.elffile
.little_endian
58 # This is the DWARFStructs the context uses, so it doesn't depend on
59 # DWARF format and address_size (these are determined per CU) - set them
61 self
.structs
= DWARFStructs(
62 little_endian
=self
.little_endian
,
66 # A list of CUs. Populated lazily when they're actually requested.
69 # Cache for abbrev tables: a dict keyed by offset
70 self
._abbrevtable
_cache
= {}
73 """ Yield all the compile units (CompileUnit objects) in the debug info
76 self
._CUs
= self
._parse
_CUs
()
77 return iter(self
._CUs
)
79 def get_abbrev_table(self
, offset
):
80 """ Get an AbbrevTable from the given offset in the debug_abbrev
83 The only verification done on the offset is that it's within the
84 bounds of the section (if not, an exception is raised).
85 It is the caller's responsibility to make sure the offset actually
86 points to a valid abbreviation table.
88 AbbrevTable objects are cached internally (two calls for the same
89 offset will return the same object).
92 offset
< self
.debug_abbrev_sec
.size
,
93 "Offset '0x%x' to abbrev table out of section bounds" % offset
)
94 if offset
not in self
._abbrevtable
_cache
:
95 self
._abbrevtable
_cache
[offset
] = AbbrevTable(
97 stream
=self
.debug_abbrev_sec
.stream
,
99 return self
._abbrevtable
_cache
[offset
]
101 def get_string_from_table(self
, offset
):
102 """ Obtain a string from the string table section, given an offset
103 relative to the section.
105 return parse_cstring_from_stream(self
.debug_str_sec
.stream
, offset
)
107 def line_program_for_CU(self
, CU
):
108 """ Given a CU object, fetch the line program it points to from the
110 If the CU doesn't point to a line program, return None.
112 # The line program is pointed to by the DW_AT_stmt_list attribute of
113 # the top DIE of a CU.
114 top_DIE
= CU
.get_top_DIE()
115 if 'DW_AT_stmt_list' in top_DIE
.attributes
:
116 return self
._parse
_line
_program
_at
_offset
(
117 top_DIE
.attributes
['DW_AT_stmt_list'].value
, CU
.structs
)
121 #------ PRIVATE ------#
123 def _parse_CUs(self
):
124 """ Parse CU entries from debug_info.
128 while offset
< self
.debug_info_sec
.size
:
129 # Section 7.4 (32-bit and 64-bit DWARF Formats) of the DWARF spec v3
130 # states that the first 32-bit word of the CU header determines
131 # whether the CU is represented with 32-bit or 64-bit DWARF format.
133 # So we peek at the first word in the CU header to determine its
134 # dwarf format. Based on it, we then create a new DWARFStructs
135 # instance suitable for this CU and use it to parse the rest.
137 initial_length
= struct_parse(
138 self
.structs
.Dwarf_uint32(''), self
.debug_info_sec
.stream
, offset
)
139 dwarf_format
= 64 if initial_length
== 0xFFFFFFFF else 32
141 # At this point we still haven't read the whole header, so we don't
142 # know the address_size. Therefore, we're going to create structs
143 # with a default address_size=4. If, after parsing the header, we
144 # find out address_size is actually 8, we just create a new structs
145 # object for this CU.
147 cu_structs
= DWARFStructs(
148 little_endian
=self
.little_endian
,
149 dwarf_format
=dwarf_format
,
152 cu_header
= struct_parse(
153 cu_structs
.Dwarf_CU_header
, self
.debug_info_sec
.stream
, offset
)
154 if cu_header
['address_size'] == 8:
155 cu_structs
= DWARFStructs(
156 little_endian
=self
.little_endian
,
157 dwarf_format
=dwarf_format
,
160 cu_die_offset
= self
.debug_info_sec
.stream
.tell()
162 self
._is
_supported
_version
(cu_header
['version']),
163 "Expected supported DWARF version. Got '%s'" % cu_header
['version'])
164 CUlist
.append(CompileUnit(
169 cu_die_offset
=cu_die_offset
))
170 # Compute the offset of the next CU in the section. The unit_length
171 # field of the CU header contains its size not including the length
174 cu_header
['unit_length'] +
175 cu_structs
.initial_length_field_size())
178 def _is_supported_version(self
, version
):
179 """ DWARF version supported by this parser
181 return 2 <= version
<= 3
183 def _parse_line_program_at_offset(self
, debug_line_offset
, structs
):
184 """ Given an offset to the .debug_line section, parse the line program
185 starting at this offset in the section and return it.
186 structs is the DWARFStructs object used to do this parsing.
188 lineprog_header
= struct_parse(
189 structs
.Dwarf_lineprog_header
,
190 self
.debug_line_sec
.stream
,
193 # Calculate the offset to the next line program (see DWARF 6.2.4)
194 end_offset
= ( debug_line_offset
+ lineprog_header
['unit_length'] +
195 structs
.initial_length_field_size())
198 header
=lineprog_header
,
201 program_start_offset
=self
.debug_line_sec
.stream
.tell(),
202 program_end_offset
=end_offset
)