6f85dbf102
The files NEWS, include/link.h, and sysdeps/generic/ldsodefs.h contribute to the version fingerprint used for detection. The fingerprint can be further refined using the --with-extra-version-id configure argument. _dl_call_libc_early_init is replaced with _dl_lookup_libc_early_init. The new function is used store a pointer to libc.so's __libc_early_init function in the libc_map_early_init member of the ld.so namespace structure. This function pointer can then be called directly, so the separate invocation function is no longer needed. The versioned symbol lookup needs the symbol versioning data structures, so the initialization of libc_map and libc_map_early_init is now done from _dl_check_map_versions, after this information becomes available. (_dl_map_object_from_fd does not set this up in time, so the initialization code had to be moved from there.) This means that the separate initialization code can be removed from dl_main because _dl_check_map_versions covers all maps, including the initial executable loaded by the kernel. The lookup still happens before relocation and the invocation of IFUNC resolvers, so IFUNC resolvers are protected from ABI mismatch. The __libc_early_init function pointer is not protected because so little code runs between the pointer write and the invocation (only dynamic linker code and IFUNC resolvers). Reviewed-by: Carlos O'Donell <carlos@redhat.com>
90 lines
3.2 KiB
Python
90 lines
3.2 KiB
Python
#!/usr/bin/python3
|
|
# Compute the hash-based name of the __libc_early_init function.
|
|
# Copyright (C) 2022 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/>.
|
|
|
|
"""Compute the name of the __libc_early_init function, which is used
|
|
as a protocol version marker between ld.so and libc.so.
|
|
|
|
The name contains a hash suffix, and the hash changes if certain key
|
|
files in the source tree change. Distributions can also configure
|
|
with --with-extra-version-id, to make the computed hash dependent on
|
|
the package version.
|
|
|
|
"""
|
|
|
|
import argparse
|
|
import hashlib
|
|
import os
|
|
import string
|
|
import sys
|
|
|
|
def gnu_hash(s):
|
|
"""Computes the GNU hash of the string."""
|
|
h = 5381
|
|
for ch in s:
|
|
if type(ch) is not int:
|
|
ch = ord(ch)
|
|
h = (h * 33 + ch) & 0xffffffff
|
|
return h
|
|
|
|
# Parse the command line.
|
|
parser = argparse.ArgumentParser(description=__doc__)
|
|
parser.add_argument('--output', metavar='PATH',
|
|
help='path to header file this tool generates')
|
|
parser.add_argument('--extra-version-id', metavar='ID',
|
|
help='extra string to influence hash computation')
|
|
parser.add_argument('inputs', metavar='PATH', nargs='*',
|
|
help='files whose contents influences the generated hash')
|
|
opts = parser.parse_args()
|
|
|
|
# Obtain the blobs that affect the generated hash.
|
|
blobs = [(opts.extra_version_id or '').encode('UTF-8')]
|
|
for path in opts.inputs:
|
|
with open(path, 'rb') as inp:
|
|
blobs.append(inp.read())
|
|
|
|
# Hash the file boundaries.
|
|
md = hashlib.sha256()
|
|
md.update(repr([len(blob) for blob in blobs]).encode('UTF-8'))
|
|
|
|
# And then hash the file contents. Do not hash the paths, to avoid
|
|
# impacting reproducibility.
|
|
for blob in blobs:
|
|
md.update(blob)
|
|
|
|
# These are the bits used to compute the suffix.
|
|
derived_bits = int.from_bytes(md.digest(), byteorder='big', signed=False)
|
|
|
|
# These digits are used in the suffix (should result in base-62 encoding).
|
|
# They must be valid in C identifiers.
|
|
digits = string.digits + string.ascii_letters
|
|
|
|
# Generate eight digits as a suffix. They should provide enough
|
|
# uniqueness (47.6 bits).
|
|
name = '__libc_early_init_'
|
|
for n in range(8):
|
|
name += digits[derived_bits % len(digits)]
|
|
derived_bits //= len(digits)
|
|
|
|
# Write the output file.
|
|
with open(opts.output, 'w') if opts.output else sys.stdout as out:
|
|
out.write('#define LIBC_EARLY_INIT_NAME {}\n'.format(name))
|
|
out.write('#define LIBC_EARLY_INIT_NAME_STRING "{}"\n'.format(name))
|
|
out.write('#define LIBC_EARLY_INIT_GNU_HASH {}\n'.format(
|
|
gnu_hash(name)))
|