From patchwork Tue May 4 10:21:23 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 43251 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id C929A395663F; Tue, 4 May 2021 10:21:16 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org C929A395663F DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1620123676; bh=MjiPaz1QO1V66s6GjqhQ/cVRmEFnqhSX9losMOFouSA=; h=To:Subject:In-Reply-To:References:Date:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To: From; b=W2/oImxcbxWlVGvNvOKj8JcaoO1yo3Co6vKQog5hGaAQbCfvjij/kiy8mAR8ZYk6/ SlUtTxwrOwtd+xVFWhjHCm7N3KSVtVW29YchzXcX/uz4SRBSf+LkkwrVsfHq83/pTw TVkQECGlgATdXURbOQ6KxAzuliKPsIHAiJN6jPCw= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id CCFA5394FC38 for ; Tue, 4 May 2021 10:21:13 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org CCFA5394FC38 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-109-ZQNrRrYYNn6Vvs7fmP1gkA-1; Tue, 04 May 2021 06:21:10 -0400 X-MC-Unique: ZQNrRrYYNn6Vvs7fmP1gkA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 97BA71008060 for ; Tue, 4 May 2021 10:21:09 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-137.ams2.redhat.com [10.36.112.137]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C07475D703 for ; Tue, 4 May 2021 10:21:08 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 2/2] elf, nptl: Resolve recursive lock implementation early In-Reply-To: References: Message-Id: <758cdeaa2a8ffb10e6ac85ca83ddf294cbd7f7dd.1620123473.git.fweimer@redhat.com> Date: Tue, 04 May 2021 12:21:23 +0200 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, KAM_STOCKGEN, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Florian Weimer via Libc-alpha From: Florian Weimer Reply-To: Florian Weimer Errors-To: libc-alpha-bounces@sourceware.org Sender: "Libc-alpha" If libpthread is included in libc, it is not necessary to delay initialization of the lock/unlock function pointers until libpthread is loaded. This eliminates two unprotected function pointers from _rtld_global and removes some initialization code from libpthread. --- elf/Makefile | 3 +- elf/dl-lock.c | 69 ++++++++++++++++++++++++++++++++++++++ elf/rtld.c | 6 ++++ nptl/nptl-init.c | 9 ----- sysdeps/generic/ldsodefs.h | 24 ++++++++++++- sysdeps/nptl/libc-lockP.h | 17 +++------- 6 files changed, 104 insertions(+), 24 deletions(-) create mode 100644 elf/dl-lock.c diff --git a/elf/Makefile b/elf/Makefile index f09988f7d2..08cfa75ffe 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -66,7 +66,8 @@ elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \ # interpreter and operating independent of libc. rtld-routines = rtld $(all-dl-routines) dl-sysdep dl-environ dl-minimal \ dl-error-minimal dl-conflict dl-hwcaps dl-hwcaps_split dl-hwcaps-subdirs \ - dl-usage dl-diagnostics dl-diagnostics-kernel dl-diagnostics-cpu + dl-usage dl-diagnostics dl-diagnostics-kernel dl-diagnostics-cpu \ + dl-lock all-rtld-routines = $(rtld-routines) $(sysdep-rtld-routines) CFLAGS-dl-runtime.c += -fexceptions -fasynchronous-unwind-tables diff --git a/elf/dl-lock.c b/elf/dl-lock.c new file mode 100644 index 0000000000..698dbf199c --- /dev/null +++ b/elf/dl-lock.c @@ -0,0 +1,69 @@ +/* Recursive locking implementation for the dynamic loader. + Copyright (C) 2021 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 + . */ + +/* If libpthread is not part of libc, a legal mechanism using + late-initialized function pointers in _rtld_global is used, and not + the code below. */ +#if PTHREAD_IN_LIBC +# include +# include +# include + +/* Pointers to the real implementation. Until they have been + initialized, the locking is a no-op. */ +static __typeof (pthread_mutex_lock) *rtld_mutex_lock attribute_relro; +static __typeof (pthread_mutex_unlock) *rtld_mutex_unlock attribute_relro; + +void +___rtld_lock_lock (__rtld_lock_recursive_t *lock) +{ + if (rtld_mutex_lock != NULL) + rtld_mutex_lock (&lock->mutex); +} + +void +___rtld_lock_unlock (__rtld_lock_recursive_t *lock) +{ + if (rtld_mutex_unlock != NULL) + rtld_mutex_unlock (&lock->mutex); +} + +void +__rtld_lock_init (void) +{ + /* There is an implicit assumption here that the lock counters are + zero and this function is called while nothing is locked. */ + + struct link_map *libc_map = GL (dl_ns)[LM_ID_BASE].libc_map; + + const ElfW(Sym) *sym + = _dl_lookup_direct (libc_map, "pthread_mutex_lock", + 0x4f152227, /* dl_new_hash output. */ + FIRST_VERSION_libc_pthread_mutex_lock_STRING, + FIRST_VERSION_libc_pthread_mutex_lock_HASH); + assert (sym != NULL); + rtld_mutex_lock = DL_SYMBOL_ADDRESS (libc_map, sym); + + sym = _dl_lookup_direct (libc_map, "pthread_mutex_unlock", + 0x7dd7aaaa, /* dl_new_hash output. */ + FIRST_VERSION_libc_pthread_mutex_unlock_STRING, + FIRST_VERSION_libc_pthread_mutex_unlock_HASH); + assert (sym != NULL); + rtld_mutex_unlock = DL_SYMBOL_ADDRESS (libc_map, sym); +} +#endif diff --git a/elf/rtld.c b/elf/rtld.c index 34879016ad..283d1770fd 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -2361,6 +2361,9 @@ dl_main (const ElfW(Phdr) *phdr, loader. */ __rtld_malloc_init_real (main_map); + /* Likewise for the locking implementation. */ + __rtld_lock_init (); + /* Mark all the objects so we know they have been already relocated. */ for (struct link_map *l = main_map; l != NULL; l = l->l_next) { @@ -2466,6 +2469,9 @@ dl_main (const ElfW(Phdr) *phdr, at this point. */ __rtld_malloc_init_real (main_map); + /* Likewise for the locking implementation. */ + __rtld_lock_init (); + RTLD_TIMING_VAR (start); rtld_timer_start (&start); diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c index b0879bd87e..f7d1c2c21e 100644 --- a/nptl/nptl-init.c +++ b/nptl/nptl-init.c @@ -179,15 +179,6 @@ __pthread_initialize_minimal_internal (void) lll_unlock (__default_pthread_attr_lock, LLL_PRIVATE); #ifdef SHARED - /* Make __rtld_lock_{,un}lock_recursive use pthread_mutex_{,un}lock, - keep the lock count from the ld.so implementation. */ - GL(dl_rtld_lock_recursive) = (void *) __pthread_mutex_lock; - GL(dl_rtld_unlock_recursive) = (void *) __pthread_mutex_unlock; - unsigned int rtld_lock_count = GL(dl_load_lock).mutex.__data.__count; - GL(dl_load_lock).mutex.__data.__count = 0; - while (rtld_lock_count-- > 0) - __pthread_mutex_lock (&GL(dl_load_lock).mutex); - GL(dl_make_stack_executable_hook) = &__make_stacks_executable; #endif diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 67c6686015..f70105aede 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -403,7 +403,7 @@ struct rtld_global struct auditstate _dl_rtld_auditstate[DL_NNS]; #endif -#if defined SHARED && defined _LIBC_REENTRANT \ +#if !PTHREAD_IN_LIBC && defined SHARED \ && defined __rtld_lock_default_lock_recursive EXTERN void (*_dl_rtld_lock_recursive) (void *); EXTERN void (*_dl_rtld_unlock_recursive) (void *); @@ -1299,6 +1299,28 @@ link_map_audit_state (struct link_map *l, size_t index) } #endif /* SHARED */ +#if PTHREAD_IN_LIBC && defined SHARED +/* Recursive locking implementation for use within the dynamic loader. + Used to define the __rtld_lock_lock_recursive and + __rtld_lock_unlock_recursive via . + + For the !PTHREAD_IN_LIBC case, GL (dl_rtld_lock_recursive) and GL + (dl_rtld_unlock_recursive) are used instead. */ +void ___rtld_lock_lock (__rtld_lock_recursive_t *lock) attribute_hidden; +void ___rtld_lock_unlock (__rtld_lock_recursive_t *lock) attribute_hidden; + +/* Called after libc has been loaded, but before RELRO is activated. + Used to initialize the function pointers to the actual + implementations. */ +void __rtld_lock_init (void) attribute_hidden; +#else /* !PTHREAD_IN_LIBC */ +static inline void +__rtld_lock_init (void) +{ + /* The initialization happens later. */ +} +#endif /* !PTHREAD_IN_LIBC */ + #if THREAD_GSCOPE_IN_TCB void __thread_gscope_wait (void) attribute_hidden; # define THREAD_GSCOPE_WAIT() __thread_gscope_wait () diff --git a/sysdeps/nptl/libc-lockP.h b/sysdeps/nptl/libc-lockP.h index ae9691d40e..76d15ed9eb 100644 --- a/sysdeps/nptl/libc-lockP.h +++ b/sysdeps/nptl/libc-lockP.h @@ -151,9 +151,6 @@ _Static_assert (LLL_LOCK_INITIALIZER == 0, "LLL_LOCK_INITIALIZER != 0"); __libc_maybe_call (__pthread_mutex_trylock, (&(NAME)), 0) #endif -#define __rtld_lock_trylock_recursive(NAME) \ - __libc_maybe_call (__pthread_mutex_trylock, (&(NAME).mutex), 0) - /* Unlock the named lock variable. */ #if IS_IN (libc) || IS_IN (libpthread) # define __libc_lock_unlock(NAME) \ @@ -163,19 +160,13 @@ _Static_assert (LLL_LOCK_INITIALIZER == 0, "LLL_LOCK_INITIALIZER != 0"); #endif #define __libc_rwlock_unlock(NAME) __pthread_rwlock_unlock (&(NAME)) -#ifdef SHARED -# define __rtld_lock_default_lock_recursive(lock) \ - ++((pthread_mutex_t *)(lock))->__data.__count; - -# define __rtld_lock_default_unlock_recursive(lock) \ - --((pthread_mutex_t *)(lock))->__data.__count; - +#if IS_IN (rtld) # define __rtld_lock_lock_recursive(NAME) \ - GL(dl_rtld_lock_recursive) (&(NAME).mutex) + ___rtld_lock_lock (&(NAME)) # define __rtld_lock_unlock_recursive(NAME) \ - GL(dl_rtld_unlock_recursive) (&(NAME).mutex) -#else + ___rtld_lock_unlock (&(NAME)) +#else /* Not in the dynamic loader. */ # define __rtld_lock_lock_recursive(NAME) \ __pthread_mutex_lock (&(NAME).mutex)