[v2] Add scripts/move-symbol-to-libc.py

  This helper script can be used to move symbols to libc.abilist across
all architectures, while preserving their symbol version.

---
 scripts/move-symbol-to-libc.py | 217 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 217 insertions(+)
  

* Florian Weimer:

> This helper script can be used to move symbols to libc.abilist across
> all architectures, while preserving their symbol version.

Ping.  This patch still needs review:

  <https://sourceware.org/pipermail/libc-alpha/2020-May/113995.html>

Thanks,
Florian
  

On 15/05/2020 10:47, Florian Weimer wrote:
> This helper script can be used to move symbols to libc.abilist across
> all architectures, while preserving their symbol version.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> 
> ---
>  scripts/move-symbol-to-libc.py | 217 +++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 217 insertions(+)
> 
> diff --git a/scripts/move-symbol-to-libc.py b/scripts/move-symbol-to-libc.py
> new file mode 100644
> index 0000000000..4863c4dd8a
> --- /dev/null
> +++ b/scripts/move-symbol-to-libc.py
> @@ -0,0 +1,217 @@
> +#!/usr/bin/python3
> +# Move symbols from other shared objects into libc.so.
> +# Copyright (C) 2020 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
> +# <https://www.gnu.org/licenses/>.
> +
> +"""Move symbols from other shared objects into libc.so.
> +
> +This script moves ABI symbols from non-libc abilists in to
> +libc.abilist.  Symbol versions are preserved.  The script must be
> +called from the top of the glibc source tree.
> +
> +"""
> +
> +import argparse
> +import os.path
> +import sys
> +
> +def replace_file(path, new_contents):
> +    """Atomically replace PATH with lines from NEW_CONTENTS.
> +
> +    NEW_CONTENTS must be a sequence of strings.
> +
> +    """
> +    temppath = path + 'T'
> +    with open(temppath, 'w') as out:
> +        for line in new_contents:
> +            out.write(line)
> +    os.rename(temppath, path)
> +
> +class VersionedSymbol:
> +    """A combination of a symbol and its version."""
> +
> +    def __init__(self, symbol, version):
> +        """Construct a new versioned symbol."""
> +        assert symbol
> +        assert version
> +        self.symbol = symbol
> +        self.version = version
> +
> +    def __str__(self):
> +        return self.symbol + '@' + self.version
> +
> +    def __eq__(self, other):
> +        return self.symbol == other.symbol and self.version == other.version
> +
> +    def __hash__(self):
> +        return hash(self.symbol) ^ hash(self.version)

Ok.

> +
> +def read_abilist(path):
> +    """Read the abilist file at PATH.
> +
> +    Return a dictionary from VersionedSymbols to their flags (as
> +    strings).
> +
> +    """
> +    result = {}
> +    with open(path) as inp:
> +        for line in inp:
> +            version, symbol, flags = line.strip().split(' ', 2)
> +            result[VersionedSymbol(symbol, version)] = flags
> +    return result

Ok.

> +
> +def abilist_lines(symbols):
> +    """Build the abilist file contents (as a list of lines).
> +
> +    SYMBOLS is a dictionary from VersionedSymbols to their flags.
> +
> +    """
> +    result = []
> +    for versym, flags in symbols.items():
> +        result.append('{} {} {}\n'.format(
> +            versym.version, versym.symbol, flags))
> +    result.sort()
> +    return result
> +
> +def add_to_libc_path(path, new_symbols):
> +    """Add SYMBOLS to the abilist file PATH.
> +
> +    NEW_SYMBOLS is a dictionary from VersionedSymbols to their flags.
> +
> +    """
> +    original_symbols = read_abilist(path)
> +    updated_symbols = original_symbols.copy()
> +    updated_symbols.update(new_symbols)
> +    if updated_symbols != original_symbols:
> +        sys.stdout.write('updating libc abilist {}\n'.format(path))
> +        replace_file(path, abilist_lines(updated_symbols))

Ok.

> +
> +# The name of the libc.so abilist file.
> +libc_abilist = 'libc.abilist'
> +
> +def add_to_libc_fallback(directory, subdirs, symbol_lines):
> +    """Add SYMBOL_LINES to the libc.abilist files in SUBDIRS in DIRECTORY.
> +
> +    All subdirectories must exist.  If they do, return True.  If not,
> +    skip processing and return False.
> +
> +    """
> +    abilists = [os.path.join(directory, subdir, libc_abilist)
> +                for subdir in subdirs]
> +    for abilist in abilists:
> +        if not os.path.exists(abilist):
> +            return False
> +    for abilist in abilists:
> +            add_to_libc_path(abilist, symbol_lines)
> +    return True

Ok.

> +
> +def add_to_libc(directory, symbol_lines):
> +
> +    """Add SYMBOL_LINES (a list of strings) to libc.abilist in DIRECTORY.
> +
> +    Try specific subdirectories as well if libc.abilist is not found
> +    in DIRECTORY.
> +
> +    """
> +    libc_path = os.path.join(directory, libc_abilist)
> +    if os.path.exists(libc_path):
> +        add_to_libc_path(libc_path, symbol_lines)
> +        return
> +
> +    # Special case for powerpc32 and mips32 variants.
> +    if add_to_libc_fallback(directory, ('fpu', 'nofpu'), symbol_lines):
> +        return
> +
> +    # Special case for mips64.
> +    if add_to_libc_fallback(directory, ('n32', 'n64'), symbol_lines):
> +        return
> +
> +    raise IOError('No libc.abilist found for: {}'.format(directory))

Ok.

> +
> +def move_symbols_1(path, to_move, moved_symbols):
> +    """Move SYMBOLS from the abilist file PATH to MOVED_SYMBOLS.
> +
> +    TO_MOVE must be a set of strings.  MOVED_SYMBOLS is a dictionary.
> +
> +    """
> +    suffix = '.abilist'
> +    assert path.endswith('.abilist')
> +    library = os.path.basename(path)[:-len(suffix)]
> +    placeholder = '__{}_version_placeholder'.format(library)
> +
> +    new_lines = []
> +    changed = False
> +
> +    old_symbols = read_abilist(path)
> +    old_versions = set(versym.version for versym in old_symbols.keys())
> +    matching_symbols = dict(e for e in old_symbols.items()
> +                            if e[0].symbol in to_move)
> +    if matching_symbols:
> +        sys.stdout.write('updating {} abilist {}\n'.format(library, path))
> +        new_symbols = dict(e for e in old_symbols.items()
> +                           if e[0].symbol not in to_move)
> +
> +        # Add placeholder symbols to prevent symbol versions from
> +        # going away completely.
> +        new_versions = set(versym.version for versym in new_symbols.keys())
> +        for missing_version in old_versions - new_versions:
> +            new_symbols[VersionedSymbol(placeholder, missing_version)] = 'F'
> +
> +        replace_file(path, abilist_lines(new_symbols))
> +
> +        moved_symbols.update(matching_symbols)


Ok.

> +
> +def move_symbols(directory, files, symbols):
> +    """Move SYMBOLS from FILES (a list of abilist file names) in DIRECTORY.
> +
> +    SYMBOLS must be a set of strings.
> +
> +    """
> +    moved_symbols = {}
> +    for filename in files:
> +        move_symbols_1(os.path.join(directory, filename), symbols,
> +                       moved_symbols)
> +    if moved_symbols:
> +        add_to_libc(directory, moved_symbols)

Ok.

> +
> +def get_parser():
> +    """Return an argument parser for this module."""
> +    parser = argparse.ArgumentParser(description=__doc__)
> +    parser.add_argument('--only-linux', action='store_true',
> +                        help='Restrict the operation to Linux abilists')
> +    parser.add_argument('symbols', help='name of the symbol to move',
> +                        nargs='+')
> +    return parser
> +
> +def main(argv):
> +    """The main entry point."""
> +    parser = get_parser()
> +    opts = parser.parse_args(argv)
> +    if opts.only_linux:
> +        sysdeps = 'sysdeps/unix/sysv/linux'
> +    else:
> +        sysdeps = 'sysdeps'
> +
> +    symbols = frozenset(opts.symbols)
> +
> +    for directory, dirs, files in os.walk(sysdeps):
> +        move_symbols(directory, [name for name in files
> +                                 if name != 'libc.abilist'
> +                                 and name.endswith('.abilist')], symbols)
> +
> +if __name__ == '__main__':
> +    main(sys.argv[1:])
> 

Ok.