scripts/readelf.py

   1 #!/usr/bin/env python
   2 #-------------------------------------------------------------------------------
   3 # scripts/readelf.py
   4 #
   5 # A clone of 'readelf' in Python, based on the pyelftools library
   6 #
   7 # Eli Bendersky (eliben@gmail.com)
   8 # This code is in the public domain
   9 #-------------------------------------------------------------------------------
  10 import os, sys
  11 from optparse import OptionParser
  12 import string
  13
  14
  15 # If elftools is not installed, maybe we're running from the root or scripts
  16 # dir of the source distribution
  17 #
  18 try:
  19     import elftools
  20 except ImportError:
  21     sys.path.extend(['.', '..'])
  22
  23 from elftools import __version__
  24 from elftools.common.exceptions import ELFError
  25 from elftools.elf.elffile import ELFFile
  26 from elftools.elf.segments import InterpSegment
  27 from elftools.elf.sections import SymbolTableSection, RelocationSection
  28 from elftools.elf.descriptions import (
  29     describe_ei_class, describe_ei_data, describe_ei_version,
  30     describe_ei_osabi, describe_e_type, describe_e_machine,
  31     describe_e_version_numeric, describe_p_type, describe_p_flags,
  32     describe_sh_type, describe_sh_flags,
  33     describe_symbol_type, describe_symbol_bind, describe_symbol_visibility,
  34     describe_symbol_shndx, describe_reloc_type,
  35     )
  36
  37
  38 class ReadElf(object):
  39     """ display_* methods are used to emit output into the output stream
  40     """
  41     def __init__(self, file, output):
  42         """ file:
  43                 stream object with the ELF file to read
  44
  45             output:
  46                 output stream to write to
  47         """
  48         self.elffile = ELFFile(file)
  49         self.output = output
  50
  51     def display_file_header(self):
  52         """ Display the ELF file header
  53         """
  54         self._emitline('ELF Header:')
  55         self._emit('  Magic:   ')
  56         self._emitline(' '.join('%2.2x' % ord(b)
  57                                     for b in self.elffile.e_ident_raw))
  58         header = self.elffile.header
  59         e_ident = header['e_ident']
  60         self._emitline('  Class:                             %s' %
  61                 describe_ei_class(e_ident['EI_CLASS']))
  62         self._emitline('  Data:                              %s' %
  63                 describe_ei_data(e_ident['EI_DATA']))
  64         self._emitline('  Version:                           %s' %
  65                 describe_ei_version(e_ident['EI_VERSION']))
  66         self._emitline('  OS/ABI:                            %s' %
  67                 describe_ei_osabi(e_ident['EI_OSABI']))
  68         self._emitline('  ABI Version:                       %d' %
  69                 e_ident['EI_ABIVERSION'])
  70         self._emitline('  Type:                              %s' %
  71                 describe_e_type(header['e_type']))
  72         self._emitline('  Machine:                           %s' %
  73                 describe_e_machine(header['e_machine']))
  74         self._emitline('  Version:                           %s' %
  75                 describe_e_version_numeric(header['e_version']))
  76         self._emitline('  Entry point address:               %s' %
  77                 self._format_hex(header['e_entry']))
  78         self._emit('  Start of program headers:          %s' %
  79                 header['e_phoff'])
  80         self._emitline(' (bytes into file)')
  81         self._emit('  Start of section headers:          %s' %
  82                 header['e_shoff'])
  83         self._emitline(' (bytes into file)')
  84         self._emitline('  Flags:                             %s' %
  85                 self._format_hex(header['e_flags']))
  86         self._emitline('  Size of this header:               %s (bytes)' %
  87                 header['e_ehsize'])
  88         self._emitline('  Size of program headers:           %s (bytes)' %
  89                 header['e_phentsize'])
  90         self._emitline('  Number of program headers:         %s' %
  91                 header['e_phnum'])
  92         self._emitline('  Size of section headers:           %s (bytes)' %
  93                 header['e_shentsize'])
  94         self._emitline('  Number of section headers:         %s' %
  95                 header['e_shnum'])
  96         self._emitline('  Section header string table index: %s' %
  97                 header['e_shstrndx'])
  98
  99     def display_program_headers(self, show_heading=True):
 100         """ Display the ELF program headers.
 101             If show_heading is True, displays the heading for this information
 102             (Elf file type is...)
 103         """
 104         self._emitline()
 105         if self.elffile.num_segments() == 0:
 106             self._emitline('There are no program headers in this file.')
 107             return
 108
 109         elfheader = self.elffile.header
 110         if show_heading:
 111             self._emitline('Elf file type is %s' %
 112                 describe_e_type(elfheader['e_type']))
 113             self._emitline('Entry point is %s' %
 114                 self._format_hex(elfheader['e_entry']))
 115             # readelf weirness - why isn't e_phoff printed as hex? (for section
 116             # headers, it is...)
 117             self._emitline('There are %s program headers, starting at offset %s' % (
 118                 elfheader['e_phnum'], elfheader['e_phoff']))
 119             self._emitline()
 120
 121         self._emitline('Program Headers:')
 122
 123         # Now comes the table of program headers with their attributes. Note
 124         # that due to different formatting constraints of 32-bit and 64-bit
 125         # addresses, there are some conditions on elfclass here.
 126         #
 127         # First comes the table heading
 128         #
 129         if self.elffile.elfclass == 32:
 130             self._emitline('  Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align')
 131         else:
 132             self._emitline('  Type           Offset             VirtAddr           PhysAddr')
 133             self._emitline('                 FileSiz            MemSiz              Flags  Align')
 134
 135         # Now the entries
 136         #
 137         for segment in self.elffile.iter_segments():
 138             self._emit('  %-14s ' % describe_p_type(segment['p_type']))
 139
 140             if self.elffile.elfclass == 32:
 141                 self._emitline('%s %s %s %s %s %-3s %s' % (
 142                     self._format_hex(segment['p_offset'], fieldsize=6),
 143                     self._format_hex(segment['p_vaddr'], fullhex=True),
 144                     self._format_hex(segment['p_paddr'], fullhex=True),
 145                     self._format_hex(segment['p_filesz'], fieldsize=5),
 146                     self._format_hex(segment['p_memsz'], fieldsize=5),
 147                     describe_p_flags(segment['p_flags']),
 148                     self._format_hex(segment['p_align'])))
 149             else: # 64
 150                 self._emitline('%s %s %s' % (
 151                     self._format_hex(segment['p_offset'], fullhex=True),
 152                     self._format_hex(segment['p_vaddr'], fullhex=True),
 153                     self._format_hex(segment['p_paddr'], fullhex=True)))
 154                 self._emitline('                 %s %s  %-3s    %s' % (
 155                     self._format_hex(segment['p_filesz'], fullhex=True),
 156                     self._format_hex(segment['p_memsz'], fullhex=True),
 157                     describe_p_flags(segment['p_flags']),
 158                     # lead0x set to False for p_align, to mimic readelf.
 159                     # No idea why the difference from 32-bit mode :-|
 160                     self._format_hex(segment['p_align'], lead0x=False)))
 161
 162             if isinstance(segment, InterpSegment):
 163                 self._emitline('      [Requesting program interpreter: %s]' %
 164                     segment.get_interp_name())
 165
 166         # Sections to segments mapping
 167         #
 168         if self.elffile.num_sections() == 0:
 169             # No sections? We're done
 170             return
 171
 172         self._emitline('\n Section to Segment mapping:')
 173         self._emitline('  Segment Sections...')
 174
 175         for nseg, segment in enumerate(self.elffile.iter_segments()):
 176             self._emit('   %2.2d     ' % nseg)
 177
 178             for section in self.elffile.iter_sections():
 179                 if (    not section.is_null() and
 180                         segment.section_in_segment(section)):
 181                     self._emit('%s ' % section.name)
 182
 183             self._emitline('')
 184
 185     def display_section_headers(self, show_heading=True):
 186         """ Display the ELF section headers
 187         """
 188         elfheader = self.elffile.header
 189         if show_heading:
 190             self._emitline('There are %s section headers, starting at offset %s' % (
 191                 elfheader['e_shnum'], self._format_hex(elfheader['e_shoff'])))
 192
 193         self._emitline('\nSection Header%s:' % (
 194             's' if elfheader['e_shnum'] > 1 else ''))
 195
 196         # Different formatting constraints of 32-bit and 64-bit addresses
 197         #
 198         if self.elffile.elfclass == 32:
 199             self._emitline('  [Nr] Name              Type            Addr     Off    Size   ES Flg Lk Inf Al')
 200         else:
 201             self._emitline('  [Nr] Name              Type             Address           Offset')
 202             self._emitline('       Size              EntSize          Flags  Link  Info  Align')
 203
 204         # Now the entries
 205         #
 206         for nsec, section in enumerate(self.elffile.iter_sections()):
 207             self._emit('  [%2u] %-17.17s %-15.15s ' % (
 208                 nsec, section.name, describe_sh_type(section['sh_type'])))
 209
 210             if self.elffile.elfclass == 32:
 211                 self._emitline('%s %s %s %s %3s %2s %3s %2s' % (
 212                     self._format_hex(section['sh_addr'], fieldsize=8, lead0x=False),
 213                     self._format_hex(section['sh_offset'], fieldsize=6, lead0x=False),
 214                     self._format_hex(section['sh_size'], fieldsize=6, lead0x=False),
 215                     self._format_hex(section['sh_entsize'], fieldsize=2, lead0x=False),
 216                     describe_sh_flags(section['sh_flags']),
 217                     section['sh_link'], section['sh_info'],
 218                     section['sh_addralign']))
 219             else: # 64
 220                 self._emitline(' %s  %s' % (
 221                     self._format_hex(section['sh_addr'], fullhex=True, lead0x=False),
 222                     self._format_hex(section['sh_offset'],
 223                         fieldsize=16 if section['sh_offset'] > 0xffffffff else 8,
 224                         lead0x=False)))
 225                 self._emitline('       %s  %s %3s      %2s   %3s     %s' % (
 226                     self._format_hex(section['sh_size'], fullhex=True, lead0x=False),
 227                     self._format_hex(section['sh_entsize'], fullhex=True, lead0x=False),
 228                     describe_sh_flags(section['sh_flags']),
 229                     section['sh_link'], section['sh_info'],
 230                     section['sh_addralign']))
 231
 232         self._emitline('Key to Flags:')
 233         self._emitline('  W (write), A (alloc), X (execute), M (merge), S (strings)')
 234         self._emitline('  I (info), L (link order), G (group), x (unknown)')
 235         self._emitline('  O (extra OS processing required) o (OS specific), p (processor specific)')
 236
 237     def display_symbol_tables(self):
 238         """ Display the symbol tables contained in the file
 239         """
 240         for section in self.elffile.iter_sections():
 241             if not isinstance(section, SymbolTableSection):
 242                 continue
 243
 244             if section['sh_entsize'] == 0:
 245                 self._emitline("\nSymbol table '%s' has a sh_entsize of zero!" % (
 246                     section.name))
 247                 continue
 248
 249             self._emitline("\nSymbol table '%s' contains %s entries:" % (
 250                 section.name, section.num_symbols()))
 251
 252             if self.elffile.elfclass == 32:
 253                 self._emitline('   Num:    Value  Size Type    Bind   Vis      Ndx Name')
 254             else: # 64
 255                 self._emitline('   Num:    Value          Size Type    Bind   Vis      Ndx Name')
 256
 257             for nsym, symbol in enumerate(section.iter_symbols()):
 258                 # symbol names are truncated to 25 chars, similarly to readelf
 259                 self._emitline('%6d: %s %5d %-7s %-6s %-7s %4s %.25s' % (
 260                     nsym,
 261                     self._format_hex(symbol['st_value'], fullhex=True, lead0x=False),
 262                     symbol['st_size'],
 263                     describe_symbol_type(symbol['st_info']['type']),
 264                     describe_symbol_bind(symbol['st_info']['bind']),
 265                     describe_symbol_visibility(symbol['st_other']['visibility']),
 266                     describe_symbol_shndx(symbol['st_shndx']),
 267                     symbol.name))
 268
 269     def display_relocations(self):
 270         """ Display the relocations contained in the file
 271         """
 272         has_relocation_sections = False
 273         for section in self.elffile.iter_sections():
 274             if not isinstance(section, RelocationSection):
 275                 continue
 276
 277             has_relocation_sections = True
 278             self._emitline("\nRelocation section '%s' at offset %s contains %s entries:" % (
 279                 section.name,
 280                 self._format_hex(section['sh_offset']),
 281                 section.num_relocations()))
 282             if section.is_RELA():
 283                 self._emitline("  Offset          Info           Type           Sym. Value    Sym. Name + Addend")
 284             else:
 285                 self._emitline(" Offset     Info    Type            Sym.Value  Sym. Name")
 286
 287             # The symbol table section pointed to in sh_link
 288             symtable = self.elffile.get_section(section['sh_link'])
 289
 290             for rel in section.iter_relocations():
 291                 hexwidth = 8 if self.elffile.elfclass == 32 else 12
 292                 self._emit('%s  %s %-17.17s' % (
 293                     self._format_hex(rel['r_offset'],
 294                         fieldsize=hexwidth, lead0x=False),
 295                     self._format_hex(rel['r_info'],
 296                         fieldsize=hexwidth, lead0x=False),
 297                     describe_reloc_type(
 298                         rel['r_info_type'], self.elffile['e_machine'])))
 299
 300                 if rel['r_info_sym'] == 0:
 301                     self._emitline()
 302                     continue
 303
 304                 symbol = symtable.get_symbol(rel['r_info_sym'])
 305                 self._emit(' %s %s%s' % (
 306                     self._format_hex(
 307                         symbol['st_value'],
 308                         fullhex=True, lead0x=False),
 309                     '  ' if self.elffile.elfclass == 32 else '',
 310                     symbol.name))
 311                 if section.is_RELA():
 312                     self._emit(' %s %x' % (
 313                         '+' if rel['r_addend'] >= 0 else '-',
 314                         abs(rel['r_addend'])))
 315                 self._emitline()
 316
 317         if not has_relocation_sections:
 318             self._emitline('\nThere are no relocations in this file.')
 319
 320     def display_hex_dump(self, section_spec):
 321         """ Display a hex dump of a section. section_spec is either a section
 322             number or a name.
 323         """
 324         section = self._section_from_spec(section_spec)
 325         if section is None:
 326             self._emitline("Section '%s' does not exist in the file!" % (
 327                 section_spec))
 328             return
 329
 330         self._emitline("\nHex dump of section '%s':" % section.name)
 331
 332         addr = section['sh_addr']
 333         data = section.data()
 334         dataptr = 0
 335
 336         while dataptr < len(data):
 337             bytesleft = len(data) - dataptr
 338             # chunks of 16 bytes per line
 339             linebytes = 16 if bytesleft > 16 else bytesleft
 340
 341             self._emit('  %s ' % self._format_hex(addr, fieldsize=8))
 342             for i in range(16):
 343                 if i < linebytes:
 344                     self._emit('%2.2x' % ord(data[dataptr + i]))
 345                 else:
 346                     self._emit('  ')
 347                 if i % 4 == 3:
 348                     self._emit(' ')
 349
 350             for i in range(linebytes):
 351                 c = data[dataptr + i]
 352                 if c >= ' ' and ord(c) < 0x7f:
 353                     self._emit(c)
 354                 else:
 355                     self._emit('.')
 356
 357             self._emitline()
 358             addr += linebytes
 359             dataptr += linebytes
 360
 361         self._emitline()
 362
 363     def display_string_dump(self, section_spec):
 364         """ Display a strings dump of a section. section_spec is either a
 365             section number or a name.
 366         """
 367         section = self._section_from_spec(section_spec)
 368         if section is None:
 369             self._emitline("Section '%s' does not exist in the file!" % (
 370                 section_spec))
 371             return
 372
 373         printables = set(string.printable)
 374         self._emitline("\nString dump of section '%s':" % section.name)
 375
 376         found = False
 377         data = section.data()
 378         dataptr = 0
 379
 380         while dataptr < len(data):
 381             while dataptr < len(data) and data[dataptr] not in printables:
 382                 dataptr += 1
 383
 384             if dataptr >= len(data):
 385                 break
 386
 387             endptr = dataptr
 388             while endptr < len(data) and data[endptr] != '\x00':
 389                 endptr += 1
 390
 391             found = True
 392             self._emitline('  [%6x]  %s' % (
 393                 dataptr, data[dataptr:endptr]))
 394
 395             dataptr = endptr
 396
 397         if not found:
 398             self._emitline('  No strings found in this section.')
 399         else:
 400             self._emitline()
 401
 402     def _format_hex(self, addr, fieldsize=None, fullhex=False, lead0x=True):
 403         """ Format an address into a hexadecimal string.
 404
 405             fieldsize:
 406                 Size of the hexadecimal field (with leading zeros to fit the
 407                 address into. For example with fieldsize=8, the format will
 408                 be %08x
 409                 If None, the minimal required field size will be used.
 410
 411             fullhex:
 412                 If True, override fieldsize to set it to the maximal size
 413                 needed for the elfclass
 414
 415             lead0x:
 416                 If True, leading 0x is added
 417         """
 418         s = '0x' if lead0x else ''
 419         if fullhex:
 420             fieldsize = 8 if self.elffile.elfclass == 32 else 16
 421         if fieldsize is None:
 422             field = '%x'
 423         else:
 424             field = '%' + '0%sx' % fieldsize
 425         return s + field % addr
 426
 427     def _section_from_spec(self, spec):
 428         """ Retrieve a section given a "spec" (either number or name).
 429             Return None if no such section exists in the file.
 430         """
 431         try:
 432             num = int(spec)
 433             if num < self.elffile.num_sections():
 434                 return self.elffile.get_section(num)
 435             else:
 436                 return None
 437         except ValueError:
 438             # Not a number. Must be a name then
 439             return self.elffile.get_section_by_name(spec)
 440
 441     def _emit(self, s=''):
 442         """ Emit an object to output
 443         """
 444         self.output.write(str(s))
 445
 446     def _emitline(self, s=''):
 447         """ Emit an object to output, followed by a newline
 448         """
 449         self.output.write(str(s) + '\n')
 450
 451
 452 SCRIPT_DESCRIPTION = 'Display information about the contents of ELF format files'
 453 VERSION_STRING = '%%prog: based on pyelftools %s' % __version__
 454
 455
 456 def main():
 457     # parse the command-line arguments and invoke ReadElf
 458     optparser = OptionParser(
 459             usage='usage: %prog [options] <elf-file>',
 460             description=SCRIPT_DESCRIPTION,
 461             add_help_option=False, # -h is a real option of readelf
 462             prog='readelf.py',
 463             version=VERSION_STRING)
 464     optparser.add_option('-H', '--help',
 465             action='store_true', dest='help',
 466             help='Display this information')
 467     optparser.add_option('-h', '--file-header',
 468             action='store_true', dest='show_file_header',
 469             help='Display the ELF file header')
 470     optparser.add_option('-l', '--program-headers', '--segments',
 471             action='store_true', dest='show_program_header',
 472             help='Display the program headers')
 473     optparser.add_option('-S', '--section-headers', '--sections',
 474             action='store_true', dest='show_section_header',
 475             help="Display the sections' headers")
 476     optparser.add_option('-e', '--headers',
 477             action='store_true', dest='show_all_headers',
 478             help='Equivalent to: -h -l -S')
 479     optparser.add_option('-s', '--symbols', '--syms',
 480             action='store_true', dest='show_symbols',
 481             help='Display the symbol table')
 482     optparser.add_option('-r', '--relocs',
 483             action='store_true', dest='show_relocs',
 484             help='Display the relocations (if present)')
 485     optparser.add_option('-x', '--hex-dump',
 486             action='store', dest='show_hex_dump', metavar='<number|name>',
 487             help='Dump the contents of section <number|name> as bytes')
 488     optparser.add_option('-p', '--string-dump',
 489             action='store', dest='show_string_dump', metavar='<number|name>',
 490             help='Dump the contents of section <number|name> as strings')
 491
 492     options, args = optparser.parse_args()
 493
 494     if options.help or len(args) == 0:
 495         optparser.print_help()
 496         sys.exit(0)
 497
 498     if options.show_all_headers:
 499         do_file_header = do_section_header = do_program_header = True
 500     else:
 501         do_file_header = options.show_file_header
 502         do_section_header = options.show_section_header
 503         do_program_header = options.show_program_header
 504
 505     with open(args[0], 'rb') as file:
 506         try:
 507             readelf = ReadElf(file, sys.stdout)
 508             if do_file_header:
 509                 readelf.display_file_header()
 510             if do_section_header:
 511                 readelf.display_section_headers(
 512                         show_heading=not do_file_header)
 513             if do_program_header:
 514                 readelf.display_program_headers(
 515                         show_heading=not do_file_header)
 516             if options.show_symbols:
 517                 readelf.display_symbol_tables()
 518             if options.show_relocs:
 519                 readelf.display_relocations()
 520             if options.show_hex_dump:
 521                 readelf.display_hex_dump(options.show_hex_dump)
 522             if options.show_string_dump:
 523                 readelf.display_string_dump(options.show_string_dump)
 524         except ELFError as ex:
 525             sys.stderr.write('ELF error: %s\n' % ex)
 526             sys.exit(1)
 527
 528
 529 #-------------------------------------------------------------------------------
 530 if __name__ == '__main__':
 531     main()
 532