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Diffstat (limited to 'conform/linknamespace.py')
| -rw-r--r-- | conform/linknamespace.py | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/conform/linknamespace.py b/conform/linknamespace.py new file mode 100644 index 0000000000..07a775499d --- /dev/null +++ b/conform/linknamespace.py @@ -0,0 +1,217 @@ +#!/usr/bin/python +# Check that use of symbols declared in a given header does not result +# in any symbols being brought in that are not reserved with external +# linkage for the given standard. +# Copyright (C) 2014-2018 Free Software Foundation, Inc. +# This file is part of the GNU C Library. +# +# The GNU C Library is free software; you can redistribute it and/or +# modify it under the terms of the GNU Lesser General Public +# License as published by the Free Software Foundation; either +# version 2.1 of the License, or (at your option) any later version. +# +# The GNU C Library is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +# Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public +# License along with the GNU C Library; if not, see +# <http://www.gnu.org/licenses/>. + +import argparse +from collections import defaultdict +import os.path +import re +import subprocess +import sys +import tempfile + +import glibcconform + +# The following whitelisted symbols are also allowed for now. +# +# * Bug 17576: stdin, stdout, stderr only reserved with external +# linkage when stdio.h included (and possibly not then), not +# generally. +# +# * Bug 18442: re_syntax_options wrongly brought in by regcomp and +# used by re_comp. +# +WHITELIST = {'stdin', 'stdout', 'stderr', 're_syntax_options'} + + +def list_syms(filename): + """Return information about GLOBAL and WEAK symbols listed in readelf + -s output.""" + ret = [] + cur_file = filename + with open(filename, 'r') as syms_file: + for line in syms_file: + line = line.rstrip() + if line.startswith('File: '): + cur_file = line[len('File: '):] + cur_file = cur_file.split('/')[-1] + continue + # Architecture-specific st_other bits appear inside [] and + # disrupt the format of readelf output. + line = re.sub(r'\[.*?\]', '', line) + fields = line.split() + if len(fields) < 8: + continue + bind = fields[4] + ndx = fields[6] + sym = fields[7] + if bind not in ('GLOBAL', 'WEAK'): + continue + if not re.fullmatch('[A-Za-z0-9_]+', sym): + continue + ret.append((cur_file, sym, bind, ndx != 'UND')) + return ret + + +def main(): + """The main entry point.""" + parser = argparse.ArgumentParser(description='Check link-time namespace.') + parser.add_argument('--header', metavar='HEADER', + help='name of header') + parser.add_argument('--standard', metavar='STD', + help='standard to use when processing header') + parser.add_argument('--cc', metavar='CC', + help='C compiler to use') + parser.add_argument('--flags', metavar='CFLAGS', + help='Compiler flags to use with CC') + parser.add_argument('--stdsyms', metavar='FILE', + help='File with list of standard symbols') + parser.add_argument('--libsyms', metavar='FILE', + help='File with symbol information from libraries') + parser.add_argument('--readelf', metavar='READELF', + help='readelf program to use') + args = parser.parse_args() + + # Load the list of symbols that are OK. + stdsyms = set() + with open(args.stdsyms, 'r') as stdsyms_file: + for line in stdsyms_file: + stdsyms.add(line.rstrip()) + stdsyms |= WHITELIST + + # Load information about GLOBAL and WEAK symbols defined or used + # in the standard libraries. + # Symbols from a given object, except for weak defined symbols. + seen_syms = defaultdict(list) + # Strong undefined symbols from a given object. + strong_undef_syms = defaultdict(list) + # Objects defining a given symbol (strongly or weakly). + sym_objs = defaultdict(list) + for file, name, bind, defined in list_syms(args.libsyms): + if defined: + sym_objs[name].append(file) + if bind == 'GLOBAL' or not defined: + seen_syms[file].append(name) + if bind == 'GLOBAL' and not defined: + strong_undef_syms[file].append(name) + + # Determine what ELF-level symbols are brought in by use of C-level + # symbols declared in the given header. + # + # The rules followed are heuristic and so may produce false + # positives and false negatives. + # + # * All undefined symbols are considered of signficance, but it is + # possible that (a) any standard library definition is weak, so + # can be overridden by the user's definition, and (b) the symbol + # is only used conditionally and not if the program is limited to + # standard functionality. + # + # * If a symbol reference is only brought in by the user using a + # data symbol rather than a function from the standard library, + # this will not be detected. + # + # * If a symbol reference is only brought in by crt*.o or libgcc, + # this will not be detected. + # + # * If a symbol reference is only brought in through __builtin_foo + # in a standard macro being compiled to call foo, this will not be + # detected. + # + # * Header inclusions should be compiled several times with + # different options such as -O2, -D_FORTIFY_SOURCE and + # -D_FILE_OFFSET_BITS=64 to find out what symbols are undefined + # from such a compilation; this is not yet implemented. + # + # * This script finds symbols referenced through use of macros on + # the basis that if a macro calls an internal function, that + # function must also be declared in the header. However, the + # header might also declare implementation-namespace functions + # that are not called by any standard macro in the header, + # resulting in false positives for any symbols brought in only + # through use of those implementation-namespace functions. + # + # * Namespace issues can apply for dynamic linking as well as + # static linking, when a call is from one shared library to + # another or uses a PLT entry for a call within a shared library; + # such issues are only detected by this script if the same + # namespace issue applies for static linking. + seen_where = {} + files_seen = set() + all_undef = {} + current_undef = {} + compiler = '%s %s' % (args.cc, args.flags) + c_syms = glibcconform.list_exported_functions(compiler, args.standard, + args.header) + with tempfile.TemporaryDirectory() as temp_dir: + cincfile_name = os.path.join(temp_dir, 'undef.c') + cincfile_o_name = os.path.join(temp_dir, 'undef.o') + cincfile_sym_name = os.path.join(temp_dir, 'undef.sym') + cincfile_text = ('#include <%s>\n%s\n' + % (args.header, + '\n'.join('void *__glibc_test_%s = (void *) &%s;' + % (sym, sym) for sym in sorted(c_syms)))) + with open(cincfile_name, 'w') as cincfile: + cincfile.write(cincfile_text) + cmd = ('%s %s -D_ISOMAC %s -c %s -o %s' + % (args.cc, args.flags, glibcconform.CFLAGS[args.standard], + cincfile_name, cincfile_o_name)) + subprocess.check_call(cmd, shell=True) + cmd = ('LC_ALL=C %s -W -s %s > %s' + % (args.readelf, cincfile_o_name, cincfile_sym_name)) + subprocess.check_call(cmd, shell=True) + for file, name, bind, defined in list_syms(cincfile_sym_name): + if bind == 'GLOBAL' and not defined: + sym_text = '[initial] %s' % name + seen_where[name] = sym_text + all_undef[name] = sym_text + current_undef[name] = sym_text + + while current_undef: + new_undef = {} + for sym, cu_sym in sorted(current_undef.items()): + for file in sym_objs[sym]: + if file in files_seen: + continue + files_seen.add(file) + for ssym in seen_syms[file]: + if ssym not in seen_where: + seen_where[ssym] = ('%s -> [%s] %s' + % (cu_sym, file, ssym)) + for usym in strong_undef_syms[file]: + if usym not in all_undef: + usym_text = '%s -> [%s] %s' % (cu_sym, file, usym) + all_undef[usym] = usym_text + new_undef[usym] = usym_text + current_undef = new_undef + + ret = 0 + for sym in sorted(seen_where): + if sym.startswith('_'): + continue + if sym in stdsyms: + continue + print(seen_where[sym]) + ret = 1 + sys.exit(ret) + + +if __name__ == '__main__': + main() |