scripts/move-symbol-to-libc.py

   1 #!/usr/bin/python3
   2 # Move symbols from other shared objects into libc.so.
   3 # Copyright (C) 2020-2022 Free Software Foundation, Inc.
   4 # This file is part of the GNU C Library.
   5 #
   6 # The GNU C Library is free software; you can redistribute it and/or
   7 # modify it under the terms of the GNU Lesser General Public
   8 # License as published by the Free Software Foundation; either
   9 # version 2.1 of the License, or (at your option) any later version.
  10 #
  11 # The GNU C Library is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 # Lesser General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU Lesser General Public
  17 # License along with the GNU C Library; if not, see
  18 # <https://www.gnu.org/licenses/>.
  19
  20 """Move symbols from other shared objects into libc.so.
  21
  22 This script moves ABI symbols from non-libc abilists in to
  23 libc.abilist.  Symbol versions are preserved.  The script must be
  24 called from the top of the glibc source tree.
  25
  26 """
  27
  28 import argparse
  29 import os.path
  30 import sys
  31
  32 # Make available glibc Python modules.
  33 sys.path.append(os.path.dirname(os.path.realpath(__file__)))
  34
  35 import glibcsymbols
  36
  37 def add_to_libc_path(path, new_symbols):
  38     """Add SYMBOLS to the abilist file PATH.
  39
  40     NEW_SYMBOLS is a dictionary from glibcsymbols.VersionedSymbol
  41     objects to their flags.
  42
  43     """
  44     original_symbols = glibcsymbols.read_abilist(path)
  45     updated_symbols = original_symbols.copy()
  46     updated_symbols.update(new_symbols)
  47     if updated_symbols != original_symbols:
  48         sys.stdout.write('updating libc abilist {}\n'.format(path))
  49         glibcsymbols.replace_file(
  50             path, glibcsymbols.abilist_lines(updated_symbols))
  51
  52 # The name of the libc.so abilist file.
  53 libc_abilist = 'libc.abilist'
  54
  55 def add_to_libc_fallback(directory, subdirs, symbol_lines):
  56     """Add SYMBOL_LINES to the libc.abilist files in SUBDIRS in DIRECTORY.
  57
  58     All subdirectories must exist.  If they do, return True.  If not,
  59     skip processing and return False.
  60
  61     """
  62     abilists = [os.path.join(directory, subdir, libc_abilist)
  63                 for subdir in subdirs]
  64     for abilist in abilists:
  65         if not os.path.exists(abilist):
  66             return False
  67     for abilist in abilists:
  68             add_to_libc_path(abilist, symbol_lines)
  69     return True
  70
  71 def add_to_libc(directory, symbol_lines):
  72
  73     """Add SYMBOL_LINES (a list of strings) to libc.abilist in DIRECTORY.
  74
  75     Try specific subdirectories as well if libc.abilist is not found
  76     in DIRECTORY.
  77
  78     """
  79     libc_path = os.path.join(directory, libc_abilist)
  80     if os.path.exists(libc_path):
  81         add_to_libc_path(libc_path, symbol_lines)
  82         return
  83
  84     # Special case for powerpc32 and mips32 variants.
  85     if add_to_libc_fallback(directory, ('fpu', 'nofpu'), symbol_lines):
  86         return
  87
  88     # Special case for mips64.
  89     if add_to_libc_fallback(directory, ('n32', 'n64'), symbol_lines):
  90         return
  91
  92     raise IOError('No libc.abilist found for: {}'.format(directory))
  93
  94 def move_symbols_1(path, to_move, moved_symbols):
  95     """Move SYMBOLS from the abilist file PATH to MOVED_SYMBOLS.
  96
  97     TO_MOVE must be a set of strings.  MOVED_SYMBOLS is a dictionary.
  98
  99     """
 100     suffix = '.abilist'
 101     assert path.endswith('.abilist')
 102     library = os.path.basename(path)[:-len(suffix)]
 103     placeholder = '__{}_version_placeholder'.format(library)
 104
 105     new_lines = []
 106     changed = False
 107
 108     old_symbols = glibcsymbols.read_abilist(path)
 109     old_versions = set(versym.version for versym in old_symbols.keys())
 110     matching_symbols = dict(e for e in old_symbols.items()
 111                             if e[0].symbol in to_move)
 112     if matching_symbols:
 113         sys.stdout.write('updating {} abilist {}\n'.format(library, path))
 114         new_symbols = dict(e for e in old_symbols.items()
 115                            if e[0].symbol not in to_move)
 116
 117         # Add placeholder symbols to prevent symbol versions from
 118         # going away completely.
 119         new_versions = set(versym.version for versym in new_symbols.keys())
 120         for missing_version in old_versions - new_versions:
 121             new_symbols[glibcsymbols.VersionedSymbol(
 122                 placeholder, missing_version)] = 'F'
 123
 124         glibcsymbols.replace_file(
 125             path, glibcsymbols.abilist_lines(new_symbols))
 126
 127         moved_symbols.update(matching_symbols)
 128
 129 def move_symbols(directory, files, symbols):
 130     """Move SYMBOLS from FILES (a list of abilist file names) in DIRECTORY.
 131
 132     SYMBOLS must be a set of strings.
 133
 134     """
 135     moved_symbols = {}
 136     for filename in files:
 137         move_symbols_1(os.path.join(directory, filename), symbols,
 138                        moved_symbols)
 139     if moved_symbols:
 140         add_to_libc(directory, moved_symbols)
 141
 142 def get_parser():
 143     """Return an argument parser for this module."""
 144     parser = argparse.ArgumentParser(description=__doc__)
 145     parser.add_argument('--only-linux', action='store_true',
 146                         help='Restrict the operation to Linux abilists')
 147     parser.add_argument('symbols', help='name of the symbol to move',
 148                         nargs='+')
 149     return parser
 150
 151 def main(argv):
 152     """The main entry point."""
 153     parser = get_parser()
 154     opts = parser.parse_args(argv)
 155     if opts.only_linux:
 156         sysdeps = 'sysdeps/unix/sysv/linux'
 157     else:
 158         sysdeps = 'sysdeps'
 159
 160     symbols = frozenset(opts.symbols)
 161
 162     for directory, dirs, files in os.walk(sysdeps):
 163         move_symbols(directory, [name for name in files
 164                                  if name != 'libc.abilist'
 165                                  and name.endswith('.abilist')], symbols)
 166
 167 if __name__ == '__main__':
 168     main(sys.argv[1:])