src/third_party/pyelftools/examples/dwarf_decode_address.py

   1 #-------------------------------------------------------------------------------
   2 # elftools example: dwarf_decode_address.py
   3 #
   4 # Decode an address in an ELF file to find out which function it belongs to
   5 # and from which filename/line it comes in the original source file.
   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 maxint, bytes2str
  21 from elftools.elf.elffile import ELFFile
  22
  23
  24 def process_file(filename, address):
  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         funcname = decode_funcname(dwarfinfo, address)
  38         file, line = decode_file_line(dwarfinfo, address)
  39
  40         print('Function:', bytes2str(funcname))
  41         print('File:', bytes2str(file))
  42         print('Line:', line)
  43
  44
  45 def decode_funcname(dwarfinfo, address):
  46     # Go over all DIEs in the DWARF information, looking for a subprogram
  47     # entry with an address range that includes the given address. Note that
  48     # this simplifies things by disregarding subprograms that may have
  49     # split address ranges.
  50     for CU in dwarfinfo.iter_CUs():
  51         for DIE in CU.iter_DIEs():
  52             try:
  53                 if DIE.tag == 'DW_TAG_subprogram':
  54                     lowpc = DIE.attributes['DW_AT_low_pc'].value
  55                     highpc = DIE.attributes['DW_AT_high_pc'].value
  56                     if lowpc <= address <= highpc:
  57                         return DIE.attributes['DW_AT_name'].value
  58             except KeyError:
  59                 continue
  60     return None
  61
  62
  63 def decode_file_line(dwarfinfo, address):
  64     # Go over all the line programs in the DWARF information, looking for
  65     # one that describes the given address.
  66     for CU in dwarfinfo.iter_CUs():
  67         # First, look at line programs to find the file/line for the address
  68         lineprog = dwarfinfo.line_program_for_CU(CU)
  69         prevaddr = maxint
  70         for entry in lineprog.get_entries():
  71             # We're interested in those entries where a new state is assigned
  72             state = entry.state
  73             if state is not None and not state.end_sequence:
  74                 if prevaddr <= address <= state.address:
  75                     filename = lineprog['file_entry'][state.file - 1].name
  76                     line = state.line
  77                     return filename, line
  78                 prevaddr = state.address
  79     return None, None
  80
  81
  82 if __name__ == '__main__':
  83     for filename in sys.argv[1:]:
  84         # For testing we use a hardcoded address.
  85         process_file(filename, 0x400503)
  86