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 pyelftools is not installed, the example can also run from the root or
  14 # examples/ dir of the source distribution.
  15 sys.path[0:0] = ['.', '..']
  16
  17 from elftools.common.py3compat import itervalues
  18 from elftools.elf.elffile import ELFFile
  19 from elftools.dwarf.descriptions import (
  20     describe_DWARF_expr, set_global_machine_arch)
  21 from elftools.dwarf.ranges import RangeEntry
  22
  23
  24 def process_file(filename):
  25     print('Processing file:', filename)
  26     with open(filename, 'rb') as f:
  27         elffile = ELFFile(f)
  28
  29         if not elffile.has_dwarf_info():
  30             print('  file has no DWARF info')
  31             return
  32
  33         # get_dwarf_info returns a DWARFInfo context object, which is the
  34         # starting point for all DWARF-based processing in pyelftools.
  35         dwarfinfo = elffile.get_dwarf_info()
  36
  37         # The range lists are extracted by DWARFInfo from the .debug_ranges
  38         # section, and returned here as a RangeLists object.
  39         range_lists = dwarfinfo.range_lists()
  40
  41         for CU in dwarfinfo.iter_CUs():
  42             # DWARFInfo allows to iterate over the compile units contained in
  43             # the .debug_info section. CU is a CompileUnit object, with some
  44             # computed attributes (such as its offset in the section) and
  45             # a header which conforms to the DWARF standard. The access to
  46             # header elements is, as usual, via item-lookup.
  47             print('  Found a compile unit at offset %s, length %s' % (
  48                 CU.cu_offset, CU['unit_length']))
  49
  50             # A CU provides a simple API to iterate over all the DIEs in it.
  51             for DIE in CU.iter_DIEs():
  52                 # Go over all attributes of the DIE. Each attribute is an
  53                 # AttributeValue object (from elftools.dwarf.die), which we
  54                 # can examine.
  55                 for attr in itervalues(DIE.attributes):
  56                     if attribute_has_range_list(attr):
  57                         # This is a range list. Its value is an offset into
  58                         # the .debug_ranges section, so we can use the range
  59                         # lists object to decode it.
  60                         rangelist = range_lists.get_range_list_at_offset(
  61                             attr.value)
  62
  63                         print('   DIE %s. attr %s.\n%s' % (
  64                             DIE.tag,
  65                             attr.name,
  66                             rangelist))
  67
  68
  69 def attribute_has_range_list(attr):
  70     """ Only some attributes can have range list values, if they have the
  71         required DW_FORM (rangelistptr "class" in DWARF spec v3)
  72     """
  73     if attr.name == 'DW_AT_ranges':
  74         if attr.form in ('DW_FORM_data4', 'DW_FORM_data8'):
  75             return True
  76     return False
  77
  78
  79 if __name__ == '__main__':
  80     for filename in sys.argv[1:]:
  81         process_file(filename)
  82
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