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Revert "Detect ld.so and libc.so version inconsistency during startup" 

This reverts commit 6f85dbf102.

Once this change hits the release branches, it will require relinking
of all statically linked applications before static dlopen works
again, for the majority of updates on release branches: The NEWS file
is regularly updated with bug references, so the __libc_early_init
suffix changes, and static dlopen cannot find the function anymore.

While this ABI check is still technically correct (we do require
rebuilding & relinking after glibc updates to keep static dlopen
working), it is too drastic for stable release branches.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>
This commit is contained in:
Florian Weimer 2022-08-25 18:46:41 +02:00
parent 025a8cce63
commit 89baed0b93
17 changed files with 45 additions and 198 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
INSTALL
View File

@ -120,16 +120,6 @@ if 'CFLAGS' is specified it must enable optimization. For example:
compiler flags which target a later instruction set architecture
(ISA).
'--with-extra-version-id=STRING'
Use STRING as part of the fingerprint that is used by the dynamic
linker to detect an incompatible version of 'libc.so'. For
example, STRING could be the full package version and release
string used by a distribution build of the GNU C Library. This
way, concurrent process creation during a package update will fail
with an error message, _error while loading shared libraries:
/lib64/libc.so.6: ld.so/libc.so mismatch detected (upgrade in
progress?)_, rather than crashing mysteriously.
'--with-timeoutfactor=NUM'
Specify an integer NUM to scale the timeout of test programs. This
factor can be changed at run time using 'TIMEOUTFACTOR' environment

14
Makerules
View File

@ -112,20 +112,6 @@ before-compile := $(common-objpfx)first-versions.h \
$(common-objpfx)ldbl-compat-choose.h $(before-compile)
$(common-objpfx)first-versions.h: $(common-objpfx)versions.stmp
$(common-objpfx)ldbl-compat-choose.h: $(common-objpfx)versions.stmp
# libc_early_init_name.h provides the actual name of the
# __libc_early_init function. It is used as a protocol version marker
# between ld.so and libc.so
before-compile := $(common-objpfx)libc_early_init_name.h $(before-compile)
libc_early_init_name-deps = \
$(..)NEWS $(..)sysdeps/generic/ldsodefs.h $(..)include/link.h
$(common-objpfx)libc_early_init_name.h: $(..)scripts/libc_early_init_name.py \
$(common-objpfx)config.make $(libc_early_init_name-deps)
$(PYTHON) $(..)scripts/libc_early_init_name.py \
--output=$@T \
--extra-version-id="$(extra-version-id)" \
$(libc_early_init_name-deps)
$(move-if-change) $@T $@
endif # avoid-generated
endif # $(build-shared) = yes

7
NEWS
View File

@ -9,12 +9,7 @@ Version 2.37
Major new features:
* The dynamic loader now prints an error message, "ld.so/libc.so
mismatch detected (upgrade in progress?)" if it detects that the
version of libc.so it loaded comes from a different build of glibc.
The new configure option --with-extra-version-id can be used to
specify an arbitrary string that affects the computation of the
version fingerprint.
[Add new features here]
Deprecated and removed features, and other changes affecting compatibility:

1
config.make.in
View File

@ -98,7 +98,6 @@ build-hardcoded-path-in-tests= @hardcoded_path_in_tests@
build-pt-chown = @build_pt_chown@
have-tunables = @have_tunables@
pthread-in-libc = @pthread_in_libc@
extra-version-id = @extra_version_id@
# Build tools.
CC = @CC@

11
configure vendored
View File

@ -760,7 +760,6 @@ with_headers
with_default_link
with_nonshared_cflags
with_rtld_early_cflags
with_extra_version_id
with_timeoutfactor
enable_sanity_checks
enable_shared
@ -1482,9 +1481,6 @@ Optional Packages:
build nonshared libraries with additional CFLAGS
--with-rtld-early-cflags=CFLAGS
build early initialization with additional CFLAGS
--extra-version-id=STRING
specify an extra version string to use in internal
ABI checks
--with-timeoutfactor=NUM
specify an integer to scale the timeout
--with-cpu=CPU select code for CPU variant
@ -3401,13 +3397,6 @@ fi
# Check whether --with-extra-version-id was given.
if test "${with_extra_version_id+set}" = set; then :
withval=$with_extra_version_id; extra_version_id="$withval"
fi
# Check whether --with-timeoutfactor was given.
if test "${with_timeoutfactor+set}" = set; then :
withval=$with_timeoutfactor; timeoutfactor=$withval

5
configure.ac
View File

@ -169,11 +169,6 @@ AC_ARG_WITH([rtld-early-cflags],
[rtld_early_cflags=])
AC_SUBST(rtld_early_cflags)
AC_ARG_WITH([extra-version-id],
AS_HELP_STRING([--extra-version-id=STRING],
[specify an extra version string to use in internal ABI checks]),
[extra_version_id="$withval"])
AC_ARG_WITH([timeoutfactor],
AS_HELP_STRING([--with-timeoutfactor=NUM],
[specify an integer to scale the timeout]),

2
elf/Makefile
View File

@ -52,6 +52,7 @@ routines = \
# The core dynamic linking functions are in libc for the static and
# profiled libraries.
dl-routines = \
dl-call-libc-early-init \
dl-close \
dl-debug \
dl-debug-symbols \
@ -64,7 +65,6 @@ dl-routines = \
dl-load \
dl-lookup \
dl-lookup-direct \
dl-lookup_libc_early_init \
dl-minimal-malloc \
dl-misc \
dl-object \

4
elf/Versions
View File

@ -29,8 +29,8 @@ libc {
__placeholder_only_for_empty_version_map;
}
GLIBC_PRIVATE {
# A pattern is needed here because the suffix is dynamically generated.
__libc_early_init_*;
# functions used in other libraries
__libc_early_init;
# Internal error handling support. Interposes the functions in ld.so.
_dl_signal_exception; _dl_catch_exception;

23
elf/dl-lookup_libc_early_init.c → elf/dl-call-libc-early-init.c
View File

@ -1,4 +1,4 @@
/* Find the address of the __libc_early_init function.
/* Invoke the early initialization function in libc.so.
Copyright (C) 2020-2022 Free Software Foundation, Inc.
This file is part of the GNU C Library.
@ -16,21 +16,26 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <ldsodefs.h>
#include <libc-early-init.h>
#include <link.h>
#include <stddef.h>
__typeof (__libc_early_init) *
_dl_lookup_libc_early_init (struct link_map *libc_map)
void
_dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
{
/* There is nothing to do if we did not actually load libc.so. */
if (libc_map == NULL)
return;
const ElfW(Sym) *sym
= _dl_lookup_direct (libc_map, LIBC_EARLY_INIT_NAME_STRING,
LIBC_EARLY_INIT_GNU_HASH,
= _dl_lookup_direct (libc_map, "__libc_early_init",
0x069682ac, /* dl_new_hash output. */
"GLIBC_PRIVATE",
0x0963cf85); /* _dl_elf_hash output. */
if (sym == NULL)
_dl_signal_error (0, libc_map->l_name, NULL, "\
ld.so/libc.so mismatch detected (upgrade in progress?)");
return DL_SYMBOL_ADDRESS (libc_map, sym);
assert (sym != NULL);
__typeof (__libc_early_init) *early_init
= DL_SYMBOL_ADDRESS (libc_map, sym);
early_init (initial);
}

9
elf/dl-load.c
View File

@ -31,6 +31,7 @@
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <gnu/lib-names.h>
/* Type for the buffer we put the ELF header and hopefully the program
header. This buffer does not really have to be too large. In most
@ -1465,6 +1466,14 @@ cannot enable executable stack as shared object requires");
add_name_to_object (l, ((const char *) D_PTR (l, l_info[DT_STRTAB])
+ l->l_info[DT_SONAME]->d_un.d_val));
/* If we have newly loaded libc.so, update the namespace
description. */
if (GL(dl_ns)[nsid].libc_map == NULL
&& l->l_info[DT_SONAME] != NULL
&& strcmp (((const char *) D_PTR (l, l_info[DT_STRTAB])
+ l->l_info[DT_SONAME]->d_un.d_val), LIBC_SO) == 0)
GL(dl_ns)[nsid].libc_map = l;
/* _dl_close can only eventually undo the module ID assignment (via
remove_slotinfo) if this function returns a pointer to a link
map. Therefore, delay this step until all possibilities for

4
elf/dl-open.c
View File

@ -760,8 +760,8 @@ dl_open_worker_begin (void *a)
if (!args->libc_already_loaded)
{
/* dlopen cannot be used to load an initial libc by design. */
if (GL(dl_ns)[args->nsid].libc_map != NULL)
GL(dl_ns)[args->nsid].libc_map_early_init (false);
struct link_map *libc_map = GL(dl_ns)[args->nsid].libc_map;
_dl_call_libc_early_init (libc_map, false);
}
args->worker_continue = true;

18
elf/dl-version.c
View File

@ -23,8 +23,6 @@
#include <string.h>
#include <ldsodefs.h>
#include <_itoa.h>
#include <gnu/lib-names.h>
#include <libc-early-init.h>
#include <assert.h>
@ -361,22 +359,6 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode)
}
}
/* Detect a libc.so loaded into this namespace. The
__libc_early_init lookup below means that we have to do this
after parsing the version data. */
if (GL(dl_ns)[map->l_ns].libc_map == NULL
&& map->l_info[DT_SONAME] != NULL
&& strcmp (((const char *) D_PTR (map, l_info[DT_STRTAB])
+ map->l_info[DT_SONAME]->d_un.d_val), LIBC_SO) == 0)
{
/* Look up this symbol early to trigger a mismatch error before
relocation (which may call IFUNC resolvers, and those can
have an internal ABI dependency). */
GL(dl_ns)[map->l_ns].libc_map_early_init
= _dl_lookup_libc_early_init (map);
GL(dl_ns)[map->l_ns].libc_map = map;
}
/* When there is a DT_VERNEED entry with libc.so on DT_NEEDED, issue
an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR
dependency. */

21
elf/libc-early-init.h
View File

@ -19,10 +19,13 @@
#ifndef _LIBC_EARLY_INIT_H
#define _LIBC_EARLY_INIT_H
#include <libc_early_init_name.h>
struct link_map;
/* If LIBC_MAP is not NULL, look up the __libc_early_init symbol in it
and call this function, with INITIAL as the argument. */
void _dl_call_libc_early_init (struct link_map *libc_map, _Bool initial)
attribute_hidden;
/* In the shared case, this function is defined in libc.so and invoked
from ld.so (or on the fist static dlopen) after complete relocation
of a new loaded libc.so, but before user-defined ELF constructors
@ -30,18 +33,6 @@ struct link_map;
startup code. If INITIAL is true, the libc being initialized is
the libc for the main program. INITIAL is false for libcs loaded
for audit modules, dlmopen, and static dlopen. */
void __libc_early_init (_Bool initial)
#ifdef SHARED
/* Redirect to the actual implementation name. */
__asm__ (LIBC_EARLY_INIT_NAME_STRING)
#endif
;
/* Attempts to find the appropriately named __libc_early_init function
in LIBC_MAP. On lookup failure, an exception is signaled,
indicating an ld.so/libc.so mismatch. */
__typeof (__libc_early_init) *_dl_lookup_libc_early_init (struct link_map *
libc_map)
attribute_hidden;
void __libc_early_init (_Bool initial);
#endif /* _LIBC_EARLY_INIT_H */

12
elf/rtld.c
View File

@ -1707,6 +1707,15 @@ dl_main (const ElfW(Phdr) *phdr,
/* Extract the contents of the dynamic section for easy access. */
elf_get_dynamic_info (main_map, false, false);
/* If the main map is libc.so, update the base namespace to
refer to this map. If libc.so is loaded later, this happens
in _dl_map_object_from_fd. */
if (main_map->l_info[DT_SONAME] != NULL
&& (strcmp (((const char *) D_PTR (main_map, l_info[DT_STRTAB])
+ main_map->l_info[DT_SONAME]->d_un.d_val), LIBC_SO)
== 0))
GL(dl_ns)[LM_ID_BASE].libc_map = main_map;
/* Set up our cache of pointers into the hash table. */
_dl_setup_hash (main_map);
}
@ -2377,8 +2386,7 @@ dl_main (const ElfW(Phdr) *phdr,
/* Relocation is complete. Perform early libc initialization. This
is the initial libc, even if audit modules have been loaded with
other libcs. */
if (GL(dl_ns)[LM_ID_BASE].libc_map != NULL)
GL(dl_ns)[LM_ID_BASE].libc_map_early_init (true);
_dl_call_libc_early_init (GL(dl_ns)[LM_ID_BASE].libc_map, true);
/* Do any necessary cleanups for the startup OS interface code.
We do these now so that no calls are made after rtld re-relocation

9
manual/install.texi
View File

@ -144,15 +144,6 @@ dynamic linker diagnostics to run on CPUs which are not compatible with
the rest of @theglibc{}, for example, due to compiler flags which target
a later instruction set architecture (ISA).
@item --with-extra-version-id=@var{string}
Use @var{string} as part of the fingerprint that is used by the dynamic
linker to detect an incompatible version of @file{libc.so}. For
example, @var{string} could be the full package version and release
string used by a distribution build of @theglibc{}. This way,
concurrent process creation during a package update will fail with an
error message, @emph{ld.so/libc.so mismatch detected (upgrade in
progress?)}, rather than crashing mysteriously.
@item --with-timeoutfactor=@var{NUM}
Specify an integer @var{NUM} to scale the timeout of test programs.
This factor can be changed at run time using @env{TIMEOUTFACTOR}

89
scripts/libc_early_init_name.py
View File

@ -1,89 +0,0 @@
#!/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)))

4
sysdeps/generic/ldsodefs.h
View File

@ -333,10 +333,6 @@ struct rtld_global
its link map. */
struct link_map *libc_map;
/* __libc_early_init function in libc_map. Initialized at the
same time as libc_map. */
void (*libc_map_early_init) (_Bool);
/* Search table for unique objects. */
struct unique_sym_table
{