from ..common.utils import struct_parse
-
+LocationExpr = namedtuple('LocationExpr', 'loc_expr')
LocationEntry = namedtuple('LocationEntry', 'begin_offset end_offset loc_expr')
BaseAddressEntry = namedtuple('BaseAddressEntry', 'base_address')
-
class LocationLists(object):
""" A single location list is a Python list consisting of LocationEntry or
BaseAddressEntry objects.
end_offset=end_offset,
loc_expr=loc_expr))
return lst
+
+class LocationParser(object):
+ """ A parser for location information in DIEs.
+ Handles both location information contained within the attribute
+ itself (represented as a LocationExpr object) and references to
+ location lists in the .debug_loc section (represented as a
+ list).
+ """
+ def __init__(self, location_lists):
+ self.location_lists = location_lists
+
+ @staticmethod
+ def attribute_has_location(attr, dwarf_version):
+ """ Checks if a DIE attribute contains location information.
+ """
+ return (LocationParser._attribute_is_loclistptr_class(attr) and
+ (LocationParser._attribute_has_loc_expr(attr, dwarf_version) or
+ LocationParser._attribute_has_loc_list(attr, dwarf_version)))
+
+ def parse_from_attribute(self, attr, dwarf_version):
+ """ Parses a DIE attribute and returns either a LocationExpr or
+ a list.
+ """
+ if self.attribute_has_location(attr, dwarf_version):
+ if self._attribute_has_loc_expr(attr, dwarf_version):
+ return LocationExpr(attr.value)
+ elif self._attribute_has_loc_list(attr, dwarf_version):
+ return self.location_lists.get_location_list_at_offset(
+ attr.value)
+ else:
+ raise ValueError("Attribute does not have location information")
+
+ #------ PRIVATE ------#
+
+ @staticmethod
+ def _attribute_has_loc_expr(attr, dwarf_version):
+ return (dwarf_version < 4 and attr.form == 'DW_FORM_block1' or
+ attr.form == 'DW_FORM_exprloc')
+
+ @staticmethod
+ def _attribute_has_loc_list(attr, dwarf_version):
+ return ((dwarf_version < 4 and
+ attr.form in ('DW_FORM_data4', 'DW_FORM_data8')) or
+ attr.form == 'DW_FORM_sec_offset')
+
+ @staticmethod
+ def _attribute_is_loclistptr_class(attr):
+ return (attr.name 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'))
--- /dev/null
+#-------------------------------------------------------------------------------
+# elftools example: dwarf_location_info.py
+#
+# Examine DIE entries which have either location list values or location
+# expression values and decode that information.
+#
+# Location information can either be completely contained within a DIE
+# (using 'DW_FORM_exprloc' in DWARFv4 or 'DW_FORM_block1' in earlier
+# versions) or be a reference to a location list contained within
+# the .debug_loc section (using 'DW_FORM_sec_offset' in DWARFv4 or
+# 'DW_FORM_data4' / 'DW_FORM_data8' in earlier versions).
+#
+# The LocationParser object parses the DIE attributes and handles both
+# formats.
+#
+# The directory 'test/testfiles_for_location_info' contains test files with
+# location information represented in both DWARFv4 and DWARFv2 forms.
+#
+# Eli Bendersky (eliben@gmail.com)
+# This code is in the public domain
+#-------------------------------------------------------------------------------
+from __future__ import print_function
+import sys
+
+# If pyelftools is not installed, the example can also run from the root or
+# examples/ dir of the source distribution.
+sys.path[0:0] = ['.', '..']
+
+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, LocationExpr, LocationParser)
+
+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')
+ return
+
+ # 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.
+ set_global_machine_arch(elffile.get_machine_arch())
+
+ # Create a LocationParser object that parses the DIE attributes and
+ # creates objects representing the actual location information.
+ loc_parser = LocationParser(location_lists)
+
+ 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):
+ # Check if this attribute contains location information
+ if loc_parser.attribute_has_location(attr, CU['version']):
+ print(' DIE %s. attr %s.' % (DIE.tag, attr.name))
+ loc = loc_parser.parse_from_attribute(attr,
+ CU['version'])
+ # We either get a list (in case the attribute is a
+ # reference to the .debug_loc section) or a LocationExpr
+ # object (in case the attribute itself contains location
+ # information).
+ if isinstance(loc, LocationExpr):
+ print(' %s' % (
+ describe_DWARF_expr(loc.loc_expr,
+ dwarfinfo.structs)))
+ elif isinstance(loc, list):
+ print(show_loclist(loc,
+ 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>>' % (
+ loc_entity,
+ describe_DWARF_expr(loc_entity.loc_expr, dwarfinfo.structs)))
+ else:
+ d.append(str(loc_entity))
+ return '\n'.join(indent + s for s in d)
+
+if __name__ == '__main__':
+ if sys.argv[1] == '--test':
+ for filename in sys.argv[2:]:
+ process_file(filename)
+++ /dev/null
-#-------------------------------------------------------------------------------
-# elftools example: dwarf_location_lists.py
-#
-# Examine DIE entries which have location list values, and decode these
-# location lists.
-#
-# Eli Bendersky (eliben@gmail.com)
-# This code is in the public domain
-#-------------------------------------------------------------------------------
-from __future__ import print_function
-import sys
-
-# If pyelftools is not installed, the example can also run from the root or
-# examples/ dir of the source distribution.
-sys.path[0:0] = ['.', '..']
-
-
-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')
- return
-
- # 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.
- set_global_machine_arch(elffile.get_machine_arch())
-
- 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, CU['version']):
- # 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(
- attr.value)
-
- print(' DIE %s. attr %s.\n%s' % (
- DIE.tag,
- attr.name,
- 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>>' % (
- loc_entity,
- describe_DWARF_expr(loc_entity.loc_expr, dwarfinfo.structs)))
- else:
- d.append(str(loc_entity))
- return '\n'.join(indent + s for s in d)
-
-
-def attribute_has_location_list(attr, dwarf_version):
- """ Only some attributes can have location list values, if they have the
- required DW_FORM (loclistptr "class" in DWARF spec v3)
- """
- if (attr.name 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 (dwarf_version < 4 and attr.form in ('DW_FORM_data4', 'DW_FORM_data8') or
- attr.form == 'DW_FORM_sec_offset'):
- return True
- return False
-
-
-if __name__ == '__main__':
- if sys.argv[1] == '--test':
- for filename in sys.argv[2:]:
- process_file(filename)
--- /dev/null
+Processing file: ./examples/sample_exe64.elf
+ Found a compile unit at offset 0, length 115
+ Found a compile unit at offset 119, length 135
+ DIE DW_TAG_variable. attr DW_AT_location.
+ (DW_OP_addr: 400608)
+ Found a compile unit at offset 258, length 156
+ DIE DW_TAG_subprogram. attr DW_AT_frame_base.
+ LocationEntry(begin_offset=0, end_offset=1, loc_expr=[119, 8]) <<(DW_OP_breg7 (rsp): 8)>>
+ LocationEntry(begin_offset=1, end_offset=4, loc_expr=[119, 16]) <<(DW_OP_breg7 (rsp): 16)>>
+ LocationEntry(begin_offset=4, end_offset=43, loc_expr=[118, 16]) <<(DW_OP_breg6 (rbp): 16)>>
+ DIE DW_TAG_formal_parameter. attr DW_AT_location.
+ (DW_OP_fbreg: -20)
+ DIE DW_TAG_formal_parameter. attr DW_AT_location.
+ (DW_OP_fbreg: -32)
+ DIE DW_TAG_variable. attr DW_AT_location.
+ (DW_OP_addr: 601018)
+ Found a compile unit at offset 418, length 300
+ DIE DW_TAG_subprogram. attr DW_AT_frame_base.
+ (DW_OP_breg7 (rsp): 8)
+ DIE DW_TAG_subprogram. attr DW_AT_frame_base.
+ LocationEntry(begin_offset=16, end_offset=64, loc_expr=[119, 8]) <<(DW_OP_breg7 (rsp): 8)>>
+ LocationEntry(begin_offset=64, end_offset=153, loc_expr=[119, 192, 0]) <<(DW_OP_breg7 (rsp): 64)>>
+ DIE DW_TAG_formal_parameter. attr DW_AT_location.
+ LocationEntry(begin_offset=16, end_offset=85, loc_expr=[85]) <<(DW_OP_reg5 (rdi))>>
+ LocationEntry(begin_offset=85, end_offset=143, loc_expr=[94]) <<(DW_OP_reg14 (r14))>>
+ DIE DW_TAG_formal_parameter. attr DW_AT_location.
+ LocationEntry(begin_offset=16, end_offset=85, loc_expr=[84]) <<(DW_OP_reg4 (rsi))>>
+ LocationEntry(begin_offset=85, end_offset=138, loc_expr=[93]) <<(DW_OP_reg13 (r13))>>
+ DIE DW_TAG_formal_parameter. attr DW_AT_location.
+ LocationEntry(begin_offset=16, end_offset=85, loc_expr=[81]) <<(DW_OP_reg1 (rdx))>>
+ LocationEntry(begin_offset=85, end_offset=133, loc_expr=[92]) <<(DW_OP_reg12 (r12))>>
+ DIE DW_TAG_variable. attr DW_AT_location.
+ LocationEntry(begin_offset=92, end_offset=123, loc_expr=[83]) <<(DW_OP_reg3 (rbx))>>
+++ /dev/null
-Processing file: ./examples/sample_exe64.elf
- Found a compile unit at offset 0, length 115
- Found a compile unit at offset 119, length 135
- Found a compile unit at offset 258, length 156
- DIE DW_TAG_subprogram. attr DW_AT_frame_base.
- LocationEntry(begin_offset=0, end_offset=1, loc_expr=[119, 8]) <<(DW_OP_breg7 (rsp): 8)>>
- LocationEntry(begin_offset=1, end_offset=4, loc_expr=[119, 16]) <<(DW_OP_breg7 (rsp): 16)>>
- LocationEntry(begin_offset=4, end_offset=43, loc_expr=[118, 16]) <<(DW_OP_breg6 (rbp): 16)>>
- Found a compile unit at offset 418, length 300
- DIE DW_TAG_subprogram. attr DW_AT_frame_base.
- LocationEntry(begin_offset=16, end_offset=64, loc_expr=[119, 8]) <<(DW_OP_breg7 (rsp): 8)>>
- LocationEntry(begin_offset=64, end_offset=153, loc_expr=[119, 192, 0]) <<(DW_OP_breg7 (rsp): 64)>>
- DIE DW_TAG_formal_parameter. attr DW_AT_location.
- LocationEntry(begin_offset=16, end_offset=85, loc_expr=[85]) <<(DW_OP_reg5 (rdi))>>
- LocationEntry(begin_offset=85, end_offset=143, loc_expr=[94]) <<(DW_OP_reg14 (r14))>>
- DIE DW_TAG_formal_parameter. attr DW_AT_location.
- LocationEntry(begin_offset=16, end_offset=85, loc_expr=[84]) <<(DW_OP_reg4 (rsi))>>
- LocationEntry(begin_offset=85, end_offset=138, loc_expr=[93]) <<(DW_OP_reg13 (r13))>>
- DIE DW_TAG_formal_parameter. attr DW_AT_location.
- LocationEntry(begin_offset=16, end_offset=85, loc_expr=[81]) <<(DW_OP_reg1 (rdx))>>
- LocationEntry(begin_offset=85, end_offset=133, loc_expr=[92]) <<(DW_OP_reg12 (r12))>>
- DIE DW_TAG_variable. attr DW_AT_location.
- LocationEntry(begin_offset=92, end_offset=123, loc_expr=[83]) <<(DW_OP_reg3 (rbx))>>
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