examples/dwarf_range_lists.py

   1 #-------------------------------------------------------------------------------
   2 # elftools example: dwarf_range_lists.py
   3 #
   4 # Examine DIE entries which have range list values, and decode these range
   5 # lists.
   6 #
   7 # Eli Bendersky (eliben@gmail.com)
   8 # This code is in the public domain
   9 #-------------------------------------------------------------------------------
  10 from __future__ import print_function
  11 import sys
  12
  13 # If elftools is not installed, maybe we're running from the root or examples
  14 # dir of the source distribution
  15 try:
  16     import elftools
  17 except ImportError:
  18     sys.path.extend(['.', '..'])
  19
  20 from elftools.common.py3compat import itervalues
  21 from elftools.elf.elffile import ELFFile
  22 from elftools.dwarf.descriptions import (
  23     describe_DWARF_expr, set_global_machine_arch)
  24 from elftools.dwarf.ranges import RangeEntry
  25
  26
  27 def process_file(filename):
  28     print('Processing file:', filename)
  29     with open(filename, 'rb') as f:
  30         elffile = ELFFile(f)
  31
  32         if not elffile.has_dwarf_info():
  33             print('  file has no DWARF info')
  34             return
  35
  36         # get_dwarf_info returns a DWARFInfo context object, which is the
  37         # starting point for all DWARF-based processing in pyelftools.
  38         dwarfinfo = elffile.get_dwarf_info()
  39
  40         # The range lists are extracted by DWARFInfo from the .debug_ranges
  41         # section, and returned here as a RangeLists object.
  42         range_lists = dwarfinfo.range_lists()
  43
  44         for CU in dwarfinfo.iter_CUs():
  45             # DWARFInfo allows to iterate over the compile units contained in
  46             # the .debug_info section. CU is a CompileUnit object, with some
  47             # computed attributes (such as its offset in the section) and
  48             # a header which conforms to the DWARF standard. The access to
  49             # header elements is, as usual, via item-lookup.
  50             print('  Found a compile unit at offset %s, length %s' % (
  51                 CU.cu_offset, CU['unit_length']))
  52
  53             # A CU provides a simple API to iterate over all the DIEs in it.
  54             for DIE in CU.iter_DIEs():
  55                 # Go over all attributes of the DIE. Each attribute is an
  56                 # AttributeValue object (from elftools.dwarf.die), which we
  57                 # can examine.
  58                 for attr in itervalues(DIE.attributes):
  59                     if attribute_has_range_list(attr):
  60                         # This is a range list. Its value is an offset into
  61                         # the .debug_ranges section, so we can use the range
  62                         # lists object to decode it.
  63                         rangelist = range_lists.get_range_list_at_offset(
  64                             attr.value)
  65
  66                         print('   DIE %s. attr %s.\n%s' % (
  67                             DIE.tag,
  68                             attr.name,
  69                             rangelist))
  70
  71
  72 def attribute_has_range_list(attr):
  73     """ Only some attributes can have range list values, if they have the
  74         required DW_FORM (rangelistptr "class" in DWARF spec v3)
  75     """
  76     if attr.name == 'DW_AT_ranges':
  77         if attr.form in ('DW_FORM_data4', 'DW_FORM_data8'):
  78             return True
  79     return False
  80
  81
  82 if __name__ == '__main__':
  83     for filename in sys.argv[1:]:
  84         process_file(filename)
  85
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