#------------------------------------------------------------------------------ # elftools: elf/gnuversions.py # # ELF sections # # Yann Rouillard (yann@pleiades.fr.eu.org) # This code is in the public domain #------------------------------------------------------------------------------ from ..construct import CString from ..common.utils import struct_parse, elf_assert from .sections import Section, Symbol class Version(object): """ Version object - representing a version definition or dependency entry from a "Version Needed" or a "Version Dependency" table section. This kind of entry contains a pointer to an array of auxiliary entries that store the information about version names or dependencies. These entries are not stored in this object and should be accessed through the appropriate method of a section object which will return an iterator of VersionAuxiliary objects. Similarly to Section objects, allows dictionary-like access to verdef/verneed entry """ def __init__(self, entry, name=None): self.entry = entry self.name = name def __getitem__(self, name): """ Implement dict-like access to entry """ return self.entry[name] class VersionAuxiliary(object): """ Version Auxiliary object - representing an auxiliary entry of a version definition or dependency entry Similarly to Section objects, allows dictionary-like access to the verdaux/vernaux entry """ def __init__(self, entry, name): self.entry = entry self.name = name def __getitem__(self, name): """ Implement dict-like access to entries """ return self.entry[name] class GNUVersionSection(Section): """ Common ancestor class for ELF SUNW|GNU Version Needed/Dependency sections class which contains shareable code """ def __init__(self, header, name, stream, elffile, stringtable, field_prefix, version_struct, version_auxiliaries_struct): super(GNUVersionSection, self).__init__(header, name, stream) self.elffile = elffile self.stringtable = stringtable self.field_prefix = field_prefix self.version_struct = version_struct self.version_auxiliaries_struct = version_auxiliaries_struct def num_versions(self): """ Number of version entries in the section """ return self['sh_info'] def _field_name(self, name, auxiliary=False): """ Return the real field's name of version or a version auxiliary entry """ middle = 'a_' if auxiliary else '_' return self.field_prefix + middle + name def _iter_version_auxiliaries(self, entry_offset, count): """ Yield all auxiliary entries of a version entry """ name_field = self._field_name('name', auxiliary=True) next_field = self._field_name('next', auxiliary=True) for _ in range(count): entry = struct_parse( self.version_auxiliaries_struct, self.stream, stream_pos=entry_offset) name = self.stringtable.get_string(entry[name_field]) version_aux = VersionAuxiliary(entry, name) yield version_aux entry_offset += entry[next_field] def iter_versions(self): """ Yield all the version entries in the section Each time it returns the main version structure and an iterator to walk through its auxiliaries entries """ aux_field = self._field_name('aux') count_field = self._field_name('cnt') next_field = self._field_name('next') entry_offset = self['sh_offset'] for _ in range(self.num_versions()): entry = struct_parse( self.version_struct, self.stream, stream_pos=entry_offset) elf_assert(entry[count_field] > 0, 'Expected number of version auxiliary entries (%s) to be > 0' 'for the following version entry: %s' % ( count_field, str(entry))) version = Version(entry) aux_entries_offset = entry_offset + entry[aux_field] version_auxiliaries_iter = self._iter_version_auxiliaries( aux_entries_offset, entry[count_field]) yield version, version_auxiliaries_iter entry_offset += entry[next_field] class GNUVerNeedSection(GNUVersionSection): """ ELF SUNW or GNU Version Needed table section. Has an associated StringTableSection that's passed in the constructor. """ def __init__(self, header, name, stream, elffile, stringtable): super(GNUVerNeedSection, self).__init__( header, name, stream, elffile, stringtable, 'vn', elffile.structs.Elf_Verneed, elffile.structs.Elf_Vernaux) self._has_indexes = None def has_indexes(self): """ Return True if at least one version definition entry has an index that is stored in the vna_other field. This information is used for symbol versioning """ if self._has_indexes is None: self._has_indexes = False for _, vernaux_iter in self.iter_versions(): for vernaux in vernaux_iter: if vernaux['vna_other']: self._has_indexes = True break return self._has_indexes def iter_versions(self): for verneed, vernaux in super(GNUVerNeedSection, self).iter_versions(): verneed.name = self.stringtable.get_string(verneed['vn_file']) yield verneed, vernaux def get_version(self, index): """ Get the version information located at index #n in the table Return boths the verneed structure and the vernaux structure that contains the name of the version """ for verneed, vernaux_iter in self.iter_versions(): for vernaux in vernaux_iter: if vernaux['vna_other'] == index: return verneed, vernaux return None class GNUVerDefSection(GNUVersionSection): """ ELF SUNW or GNU Version Definition table section. Has an associated StringTableSection that's passed in the constructor. """ def __init__(self, header, name, stream, elffile, stringtable): super(GNUVerDefSection, self).__init__( header, name, stream, elffile, stringtable, 'vd', elffile.structs.Elf_Verdef, elffile.structs.Elf_Verdaux) def get_version(self, index): """ Get the version information located at index #n in the table Return boths the verdef structure and an iterator to retrieve both the version names and dependencies in the form of verdaux entries """ for verdef, verdaux_iter in self.iter_versions(): if verdef['vd_ndx'] == index: return verdef, verdaux_iter return None class GNUVerSymSection(Section): """ ELF SUNW or GNU Versym table section. Has an associated SymbolTableSection that's passed in the constructor. """ def __init__(self, header, name, stream, elffile, symboltable): super(GNUVerSymSection, self).__init__(header, name, stream) self.elffile = elffile self.elfstructs = self.elffile.structs self.symboltable = symboltable def num_symbols(self): """ Number of symbols in the table """ return self['sh_size'] // self['sh_entsize'] def get_symbol(self, n): """ Get the symbol at index #n from the table (Symbol object) It begins at 1 and not 0 since the first entry is used to store the current version of the syminfo table """ # Grab the symbol's entry from the stream entry_offset = self['sh_offset'] + n * self['sh_entsize'] entry = struct_parse( self.elfstructs.Elf_Versym, self.stream, stream_pos=entry_offset) # Find the symbol name in the associated symbol table name = self.symboltable.get_symbol(n).name return Symbol(entry, name) def iter_symbols(self): """ Yield all the symbols in the table """ for i in range(self.num_symbols()): yield self.get_symbol(i)