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