From patchwork Thu Dec 23 18:43:12 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 49222 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 74F8F385801A for ; Thu, 23 Dec 2021 18:44:14 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 74F8F385801A DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1640285054; bh=IeToeK1bNwKEjZdHncTgXb1NlH0iZsCjKPsxxbcN4Fc=; 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=PyY+Jz2mLx27+5cHdHkWQNLnvWQ4VYiCJtjtTqKUOg2u4Pna9vN3t13Y9RVvjDNw4 J8kIRNQwAWHqCvsX94KC+X2NTnbAhZJvV2bnHmf0jWDNO8JxL9m3daYSO+mlxl3CQV OVi7rMWMeTw0jvMfbqqoYV5toVi3aSOzJCGXXGIQ= 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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 7E08C3858418 for ; Thu, 23 Dec 2021 18:43:17 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 7E08C3858418 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-642-uv4zXRPFPqy6jky4RPcnvA-1; Thu, 23 Dec 2021 13:43:16 -0500 X-MC-Unique: uv4zXRPFPqy6jky4RPcnvA-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 4ECB818460E5 for ; Thu, 23 Dec 2021 18:43:15 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 714F85BE31 for ; Thu, 23 Dec 2021 18:43:14 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 1/4] elf: Introduce separate _r_debug_array variable In-Reply-To: References: X-From-Line: 542db0fb1943e2fbd47eec83d044a471b8d7c810 Mon Sep 17 00:00:00 2001 Message-Id: <542db0fb1943e2fbd47eec83d044a471b8d7c810.1640284721.git.fweimer@redhat.com> Date: Thu, 23 Dec 2021 19:43:12 +0100 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=-12.3 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" It replaces the ns_debug member of the namespaces. Previously, the base namespace had an unused ns_debug member. This change also fixes a concurrency issue: _dl_debug_initialize only updates r_next of the previous namespace's r_debug after the new r_debug is initialized, so that only the initialized version is observed. --- elf/dl-debug.c | 91 +++++++++++++++++++++----------------- sysdeps/generic/ldsodefs.h | 2 - 2 files changed, 50 insertions(+), 43 deletions(-) diff --git a/elf/dl-debug.c b/elf/dl-debug.c index f637d4bb8d..649386d5a6 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -30,17 +30,37 @@ extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr) && VERIFY_MEMBER (l_prev)) ? 1 : -1]; +#ifdef SHARED +/* r_debug structs for secondary namespaces. The first namespace is + handled separately because its r_debug structure must overlap with + the public _r_debug symbol, so the first array element corresponds + to LM_ID_BASE + 1. See elf/dl-debug-symbols.S. */ +struct r_debug_extended _r_debug_array[DL_NNS - 1]; + +/* Return the r_debug object for the namespace NS. */ +static inline struct r_debug_extended * +get_rdebug (Lmid_t ns) +{ + if (ns == LM_ID_BASE) + return &_r_debug_extended; + else + return &_r_debug_array[ns - 1]; +} +#else /* !SHARED */ +static inline struct r_debug_extended * +get_rdebug (Lmid_t ns) +{ + return &_r_debug_extended; /* There is just one namespace. */ +} +#endif /* !SHARED */ + /* Update the `r_map' member and return the address of `struct r_debug' of the namespace NS. */ struct r_debug * _dl_debug_update (Lmid_t ns) { - struct r_debug_extended *r; - if (ns == LM_ID_BASE) - r = &_r_debug_extended; - else - r = &GL(dl_ns)[ns]._ns_debug; + struct r_debug_extended *r = get_rdebug (ns); if (r->base.r_map == NULL) atomic_store_release (&r->base.r_map, (void *) GL(dl_ns)[ns]._ns_loaded); @@ -54,34 +74,7 @@ _dl_debug_update (Lmid_t ns) struct r_debug * _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) { - struct r_debug_extended *r, **pp = NULL; - - if (ns == LM_ID_BASE) - { - r = &_r_debug_extended; - /* Initialize r_version to 1. */ - if (_r_debug_extended.base.r_version == 0) - _r_debug_extended.base.r_version = 1; - } - else if (DL_NNS > 1) - { - r = &GL(dl_ns)[ns]._ns_debug; - if (r->base.r_brk == 0) - { - /* Add the new namespace to the linked list. After a namespace - is initialized, r_brk becomes non-zero. A namespace becomes - empty (r_map == NULL) when it is unused. But it is never - removed from the linked list. */ - struct r_debug_extended *p; - for (pp = &_r_debug_extended.r_next; - (p = *pp) != NULL; - pp = &p->r_next) - ; - - r->base.r_version = 2; - } - } - + struct r_debug_extended *r = get_rdebug (ns); if (r->base.r_brk == 0) { /* Tell the debugger where to find the map of loaded objects. @@ -89,20 +82,36 @@ _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) only once. */ r->base.r_ldbase = ldbase ?: _r_debug_extended.base.r_ldbase; r->base.r_brk = (ElfW(Addr)) &_dl_debug_state; - r->r_next = NULL; + +#ifdef SHARED + /* Add the new namespace to the linked list. This assumes that + namespaces are allocated in increasing order. After a + namespace is initialized, r_brk becomes non-zero. A + namespace becomes empty (r_map == NULL) when it is unused. + But it is never removed from the linked list. */ + + if (ns != LM_ID_BASE) + { + r->base.r_version = 2; + if (ns - 1 == LM_ID_BASE) + { + atomic_store_release (&_r_debug_extended.r_next, r); + /* Now there are multiple namespaces. */ + atomic_store_release (&_r_debug_extended.base.r_version, 2); + } + else + /* Update r_debug_extended of the previous namespace. */ + atomic_store_release (&_r_debug_array[ns - 2].r_next, r); + } + else +#endif /* SHARED */ + r->base.r_version = 1; } if (r->base.r_map == NULL) atomic_store_release (&r->base.r_map, (void *) GL(dl_ns)[ns]._ns_loaded); - if (pp != NULL) - { - atomic_store_release (pp, r); - /* Bump r_version to 2 for the new namespace. */ - atomic_store_release (&_r_debug_extended.base.r_version, 2); - } - return &r->base; } diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index c26860430c..a9189f5501 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -368,8 +368,6 @@ struct rtld_global size_t n_elements; void (*free) (void *); } _ns_unique_sym_table; - /* Keep track of changes to each namespace' list. */ - struct r_debug_extended _ns_debug; } _dl_ns[DL_NNS]; /* One higher than index of last used namespace. */ EXTERN size_t _dl_nns; From patchwork Thu Dec 23 18:43:17 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 49223 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 8F6713858012 for ; Thu, 23 Dec 2021 18:44:56 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 8F6713858012 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1640285096; bh=2QFi3kasPR9HI7689CgfdFLJbMGnhwOmrzRQtVU5KNA=; 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=LiDcfqboC9e5HGOJqEyJcrt65MvqYIBwIzKH6vYpyjXEZSmhu14PweiO5bH7UqUUw 7Ij7uHaLM2kG1v+MjFqqaj0IyMUxVVRklOdP4oUhR0S03jjTOlNEJhuyNrkgsdUEID T9x4jEFJujzkD7F5qxZca3ErgWjv7UPCLiDIEfMk= 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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id D30F93858016 for ; Thu, 23 Dec 2021 18:43:22 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D30F93858016 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-16-HvcyTUgXPIixmcHmxAN2zg-1; Thu, 23 Dec 2021 13:43:21 -0500 X-MC-Unique: HvcyTUgXPIixmcHmxAN2zg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5282E802CB7 for ; Thu, 23 Dec 2021 18:43:20 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 75DCC5BD06 for ; Thu, 23 Dec 2021 18:43:19 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 2/4] elf: Introduce _dl_debug_change_state In-Reply-To: References: X-From-Line: 3dbe34711e326e9910e548619aaea2cc44bdb204 Mon Sep 17 00:00:00 2001 Message-Id: <3dbe34711e326e9910e548619aaea2cc44bdb204.1640284721.git.fweimer@redhat.com> Date: Thu, 23 Dec 2021 19:43:17 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.3 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" It combines updating r_state with the debugger notification. The change to _dl_open introduces an additional debugger notification for dlmopen, but debuggers are expected to ignore it. --- elf/dl-close.c | 6 ++---- elf/dl-debug.c | 7 +++++++ elf/dl-load.c | 6 ++---- elf/dl-open.c | 5 ++--- elf/rtld.c | 6 ++---- sysdeps/generic/ldsodefs.h | 14 ++++++++++++-- 6 files changed, 27 insertions(+), 17 deletions(-) diff --git a/elf/dl-close.c b/elf/dl-close.c index 4f5cfcc1c3..660a46e8ed 100644 --- a/elf/dl-close.c +++ b/elf/dl-close.c @@ -495,8 +495,7 @@ _dl_close_worker (struct link_map *map, bool force) /* Notify the debugger we are about to remove some loaded objects. */ struct r_debug *r = _dl_debug_update (nsid); - r->r_state = RT_DELETE; - _dl_debug_state (); + _dl_debug_change_state (r, RT_DELETE); LIBC_PROBE (unmap_start, 2, nsid, r); if (unload_global) @@ -820,8 +819,7 @@ _dl_close_worker (struct link_map *map, bool force) while (GL(dl_ns)[GL(dl_nns) - 1]._ns_loaded == NULL); /* Notify the debugger those objects are finalized and gone. */ - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (unmap_complete, 2, nsid, r); /* Recheck if we need to retry, release the lock. */ diff --git a/elf/dl-debug.c b/elf/dl-debug.c index 649386d5a6..f840a1b922 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -67,6 +67,13 @@ _dl_debug_update (Lmid_t ns) return &r->base; } +void +_dl_debug_change_state (struct r_debug *r, int state) +{ + atomic_store_release (&r->r_state, state); + _dl_debug_state (); +} + /* Initialize _r_debug_extended for the namespace NS. LDBASE is the run-time load address of the dynamic linker, to be put in _r_debug_extended.r_ldbase. Return the address of _r_debug. */ diff --git a/elf/dl-load.c b/elf/dl-load.c index 2a1443387f..94b5bd619a 100644 --- a/elf/dl-load.c +++ b/elf/dl-load.c @@ -987,8 +987,7 @@ _dl_map_object_from_fd (const char *name, const char *origname, int fd, if (make_consistent && r != NULL) { - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (map_failed, 2, nsid, r); } @@ -1506,8 +1505,7 @@ cannot enable executable stack as shared object requires"); /* Notify the debugger we have added some objects. We need to call _dl_debug_initialize in a static program in case dynamic linking has not been used before. */ - r->r_state = RT_ADD; - _dl_debug_state (); + _dl_debug_change_state (r, RT_ADD); LIBC_PROBE (map_start, 2, nsid, r); make_consistent = true; } diff --git a/elf/dl-open.c b/elf/dl-open.c index 6ea5dd2457..545037a031 100644 --- a/elf/dl-open.c +++ b/elf/dl-open.c @@ -634,8 +634,7 @@ dl_open_worker_begin (void *a) /* Notify the debugger all new objects are now ready to go. */ struct r_debug *r = _dl_debug_update (args->nsid); - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (map_complete, 3, args->nsid, r, new); _dl_open_check (new); @@ -863,7 +862,7 @@ no more namespaces available for dlmopen()")); ++GL(dl_nns); } - _dl_debug_update (nsid)->r_state = RT_CONSISTENT; + _dl_debug_change_state (_dl_debug_update (nsid), RT_CONSISTENT); } /* Never allow loading a DSO in a namespace which is empty. Such direct placements is only causing problems. Also don't allow diff --git a/elf/rtld.c b/elf/rtld.c index 4b09e84b0d..dd4173c2ca 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -1807,8 +1807,7 @@ dl_main (const ElfW(Phdr) *phdr, #endif /* We start adding objects. */ - r->r_state = RT_ADD; - _dl_debug_state (); + _dl_debug_change_state (r, RT_ADD); LIBC_PROBE (init_start, 2, LM_ID_BASE, r); /* Auditing checkpoint: we are ready to signal that the initial map @@ -2527,8 +2526,7 @@ dl_main (const ElfW(Phdr) *phdr, /* Notify the debugger all new objects are now ready to go. We must re-get the address since by now the variable might be in another object. */ r = _dl_debug_update (LM_ID_BASE); - r->r_state = RT_CONSISTENT; - _dl_debug_state (); + _dl_debug_change_state (r, RT_CONSISTENT); LIBC_PROBE (init_complete, 2, LM_ID_BASE, r); #if defined USE_LDCONFIG && !defined MAP_COPY diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index a9189f5501..9efd5506b6 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1125,8 +1125,14 @@ extern void _dl_debug_state (void); rtld_hidden_proto (_dl_debug_state) /* Initialize `struct r_debug_extended' for the namespace NS. LDBASE - is the run-time load address of the dynamic linker, to be put in the - `r_ldbase' member. Return the address of the structure. */ + is the run-time load address of the dynamic linker, to be put in + the `r_ldbase' member. + + This function returns the address of the r_debug structure for the + namespace. This is not merely a convenience or optimization, but + it is necessary for the LIBC_PROBE Systemtap/debugger probes to + work reliably: direct variable access can create probes that tools + cannot consume. */ extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) attribute_hidden; @@ -1134,6 +1140,10 @@ extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) of the namespace NS. */ extern struct r_debug *_dl_debug_update (Lmid_t ns) attribute_hidden; +/* Updates R->r_state to STATE and notifies the debugger by calling + _dl_debug_state. */ +void _dl_debug_change_state (struct r_debug *r, int state) attribute_hidden; + /* Initialize the basic data structure for the search paths. SOURCE is either "LD_LIBRARY_PATH" or "--library-path". GLIBC_HWCAPS_PREPEND adds additional glibc-hwcaps subdirectories to From patchwork Thu Dec 23 18:43:22 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 49224 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 A32733858012 for ; Thu, 23 Dec 2021 18:45:38 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A32733858012 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1640285138; bh=qwbetgKJXWFj4xBXuuexilTGne/VyB4r1Uob1v+b1ak=; 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=yP+WdXiNdHU90taLIjAtfvQs3sgTdKzY1jR5b0fRIUyXXmE8ye9pyI0Cj59M04MRT 9gYh1MztqZUSVKAJvDcmOsBFw0kgsxGKEXuLEkIoGHb33Qcwe31IkyKOe2GCFnvCih xlLWRuG4R7aCEbaO1Oq+c2T9GMiQBSyb/K0NMpyo= 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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 6D1923858016 for ; Thu, 23 Dec 2021 18:43:27 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 6D1923858016 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-168-xwD_dMkOP5C4xcnal_UBcg-1; Thu, 23 Dec 2021 13:43:25 -0500 X-MC-Unique: xwD_dMkOP5C4xcnal_UBcg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 084561800D50 for ; Thu, 23 Dec 2021 18:43:25 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6181AE2FE for ; Thu, 23 Dec 2021 18:43:24 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 3/4] elf: Support version-less lookup in _dl_lookup_direct In-Reply-To: References: X-From-Line: 52bda11381ea8bec52decc1809373971e46abbab Mon Sep 17 00:00:00 2001 Message-Id: <52bda11381ea8bec52decc1809373971e46abbab.1640284721.git.fweimer@redhat.com> Date: Thu, 23 Dec 2021 19:43:22 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.3 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" --- elf/dl-lookup-direct.c | 5 +++++ sysdeps/generic/ldsodefs.h | 7 ++++--- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/elf/dl-lookup-direct.c b/elf/dl-lookup-direct.c index 08ac4d4104..6617962c4d 100644 --- a/elf/dl-lookup-direct.c +++ b/elf/dl-lookup-direct.c @@ -54,6 +54,11 @@ check_match (const struct link_map *const map, const char *const undef_name, /* Not the symbol we are looking for. */ return NULL; + if (map->l_versyms == NULL || version == NULL) + /* No symbol versioning information available, or no symbol + version requested. Accepted the symbol. */ + return sym; + ElfW(Half) ndx = map->l_versyms[symidx] & 0x7fff; if (map->l_versions[ndx].hash != version_hash || strcmp (map->l_versions[ndx].name, version) != 0) diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 9efd5506b6..8ff06d6b02 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1051,9 +1051,10 @@ extern lookup_t _dl_lookup_symbol_x (const char *undef, MAP) for the symbol UNDEF_NAME, with GNU hash NEW_HASH (computed with dl_new_hash), symbol version VERSION, and symbol version hash VERSION_HASH (computed with _dl_elf_hash). Returns a pointer to - the symbol table entry in MAP on success, or NULL on failure. MAP - must have symbol versioning information, or otherwise the result is - undefined. */ + the symbol table entry in MAP on success, or NULL on failure. + + If VERSION is NULL or MAP does not have symbol versioning + information, any symbol version is accepted. */ const ElfW(Sym) *_dl_lookup_direct (struct link_map *map, const char *undef_name, uint32_t new_hash, From patchwork Thu Dec 23 18:43:28 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Florian Weimer X-Patchwork-Id: 49225 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 A8B3C3858008 for ; Thu, 23 Dec 2021 18:46:20 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org A8B3C3858008 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1640285180; bh=usQBOWRAEI19RTtae1NY8d4cvpn+bnSsVO8dO+fhhfs=; 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=GQA9ekxlD4+9xW9VJUsjhFN4zIuA5wccphji57LiB4XP7lbsj/+WM1IADpQEFjoY4 vMVrIxXVHNl1XWKtGiXy8rBOJnjnBgu+nW45SFJ8F5kXC/n90golKlyK74IkEXzKFN sHruRQhxmqSQEV7tA7E0DlXD5XiOr+Z3tfli9hGk= 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 [170.10.133.124]) by sourceware.org (Postfix) with ESMTPS id 70C9F385800C for ; Thu, 23 Dec 2021 18:43:37 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 70C9F385800C Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-402-VGzvdUwoOUWjck3Hq6xPxg-1; Thu, 23 Dec 2021 13:43:34 -0500 X-MC-Unique: VGzvdUwoOUWjck3Hq6xPxg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C0CB55A07E for ; Thu, 23 Dec 2021 18:43:33 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.104]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 84C755BD17 for ; Thu, 23 Dec 2021 18:43:30 +0000 (UTC) To: libc-alpha@sourceware.org Subject: [PATCH 4/4] elf: Restore support for _r_debug copy relocations In-Reply-To: References: X-From-Line: 3476c853788916a9a189ca0a9d31234cc05bb27d Mon Sep 17 00:00:00 2001 Message-Id: <3476c853788916a9a189ca0a9d31234cc05bb27d.1640284721.git.fweimer@redhat.com> Date: Thu, 23 Dec 2021 19:43:28 +0100 User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-11.5 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_STOCKGEN, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) 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+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" The changes in commit a93d9e03a31ec14405cb3a09aa95413b67067380 ("Extend struct r_debug to support multiple namespaces [BZ #15971]") break the dyninst dynamic instrumentation tool. It turns out it is rather hard to use the proposed handshake for accessing _r_debug via DT_DEBUG. Therefore, this commit restores copy relocation support by adjusting the copy of _r_debug in the main executable if a copy relocation is in play. --- elf/Makefile | 8 +++++++ elf/dl-debug.c | 46 +++++++++++++++++++++++++++++++++++--- elf/rtld.c | 4 ++++ elf/tst-dlmopen4-nonpic.c | 2 ++ elf/tst-dlmopen4-pic.c | 2 ++ elf/tst-dlmopen4.c | 22 ++++++++++++++++++ sysdeps/generic/ldsodefs.h | 4 ++++ 7 files changed, 85 insertions(+), 3 deletions(-) create mode 100644 elf/tst-dlmopen4-nonpic.c create mode 100644 elf/tst-dlmopen4-pic.c diff --git a/elf/Makefile b/elf/Makefile index fe42caeb0e..000f9311ca 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -210,6 +210,7 @@ tests += restest1 preloadtest loadfail multiload origtest resolvfail \ tst-align tst-align2 tst-align3 \ tst-dlmodcount tst-dlopenrpath tst-deep1 \ tst-dlmopen1 tst-dlmopen3 tst-dlmopen4 \ + tst-dlmopen4-pic tst-dlmopen4-nonpic \ unload3 unload4 unload5 unload6 unload7 unload8 tst-global1 order2 \ tst-audit1 tst-audit2 tst-audit8 tst-audit9 \ tst-addr1 tst-thrlock \ @@ -1308,6 +1309,13 @@ $(objpfx)tst-dlmopen3.out: $(objpfx)tst-dlmopen1mod.so $(objpfx)tst-dlmopen4.out: $(objpfx)tst-dlmopen1mod.so +CFLAGS-tst-dlmopen4-pic.c += -fPIC +$(objpfx)tst-dlmopen4-pic.out: $(objpfx)tst-dlmopen1mod.so + +CFLAGS-tst-dlmopen4-nonpic.c += -fno-pie +tst-dlmopen4-nonpic-no-pie = yes +$(objpfx)tst-dlmopen4-nonpic.out: $(objpfx)tst-dlmopen1mod.so + $(objpfx)tst-audit1.out: $(objpfx)tst-auditmod1.so tst-audit1-ENV = LD_AUDIT=$(objpfx)tst-auditmod1.so diff --git a/elf/dl-debug.c b/elf/dl-debug.c index f840a1b922..1aa79bc9b5 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -37,6 +37,32 @@ extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr) to LM_ID_BASE + 1. See elf/dl-debug-symbols.S. */ struct r_debug_extended _r_debug_array[DL_NNS - 1]; +/* If not null, pointer to the _r_debug in the main executable. */ +static struct r_debug *_r_debug_main; + +void +_dl_debug_post_relocate (struct link_map *main_map) +{ + const ElfW(Sym) *sym = _dl_lookup_direct (main_map, "_r_debug", 0x5475103c, + NULL, 0); + if (sym != NULL && sym->st_size >= sizeof (struct r_debug)) + { + struct r_debug *main_r_debug = DL_SYMBOL_ADDRESS (main_map, sym); + if (main_r_debug != &_r_debug_extended.base) + { + /* The extended version of the struct is not available in + the main executable because a copy relocation has been + used. r_map etc. have already been copied as part of the + copy relocation processing. */ + main_r_debug->r_version = 1; + + /* Record that dual updates of the initial link map are + required. */ + _r_debug_main = main_r_debug; + } + } +} + /* Return the r_debug object for the namespace NS. */ static inline struct r_debug_extended * get_rdebug (Lmid_t ns) @@ -71,6 +97,11 @@ void _dl_debug_change_state (struct r_debug *r, int state) { atomic_store_release (&r->r_state, state); +#ifdef SHARED + if (r == &_r_debug_extended.base && _r_debug_main != NULL) + /* Update the copy-relocation of _r_debug. */ + atomic_store_release (&_r_debug_main->r_state, state); +#endif _dl_debug_state (); } @@ -103,7 +134,9 @@ _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) if (ns - 1 == LM_ID_BASE) { atomic_store_release (&_r_debug_extended.r_next, r); - /* Now there are multiple namespaces. */ + /* Now there are multiple namespaces. Note that this + deliberately does not update the copy in the main + executable (if it exists). */ atomic_store_release (&_r_debug_extended.base.r_version, 2); } else @@ -116,8 +149,15 @@ _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) } if (r->base.r_map == NULL) - atomic_store_release (&r->base.r_map, - (void *) GL(dl_ns)[ns]._ns_loaded); + { + struct link_map *l = (void *) GL(dl_ns)[ns]._ns_loaded; + atomic_store_release (&r->base.r_map, l); +#ifdef SHARED + if (ns == LM_ID_BASE && _r_debug_main != NULL) + /* Update the copy-relocation of _r_debug. */ + atomic_store_release (&_r_debug_main->r_map, l); +#endif + } return &r->base; } diff --git a/elf/rtld.c b/elf/rtld.c index dd4173c2ca..ae3514eade 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -2428,6 +2428,7 @@ dl_main (const ElfW(Phdr) *phdr, if (l->l_tls_blocksize != 0 && tls_init_tp_called) _dl_add_to_slotinfo (l, true); } + rtld_timer_stop (&relocate_time, start); /* Now enable profiling if needed. Like the previous call, @@ -2439,6 +2440,9 @@ dl_main (const ElfW(Phdr) *phdr, _dl_start_profile (); } + /* Update _r_debug if necessary. */ + _dl_debug_post_relocate (main_map); + if ((!was_tls_init_tp_called && GL(dl_tls_max_dtv_idx) > 0) || count_modids != _dl_count_modids ()) ++GL(dl_tls_generation); diff --git a/elf/tst-dlmopen4-nonpic.c b/elf/tst-dlmopen4-nonpic.c new file mode 100644 index 0000000000..ad4e409953 --- /dev/null +++ b/elf/tst-dlmopen4-nonpic.c @@ -0,0 +1,2 @@ +#define BUILD_FOR_NONPIC +#include "tst-dlmopen4.c" diff --git a/elf/tst-dlmopen4-pic.c b/elf/tst-dlmopen4-pic.c new file mode 100644 index 0000000000..919fa85c25 --- /dev/null +++ b/elf/tst-dlmopen4-pic.c @@ -0,0 +1,2 @@ +#define BUILD_FOR_PIC +#include "tst-dlmopen4.c" diff --git a/elf/tst-dlmopen4.c b/elf/tst-dlmopen4.c index 3fe150e50b..633addf419 100644 --- a/elf/tst-dlmopen4.c +++ b/elf/tst-dlmopen4.c @@ -53,6 +53,15 @@ do_test (void) TEST_COMPARE (debug->base.r_version, 1); TEST_VERIFY_EXIT (debug->r_next == NULL); +#ifdef BUILD_FOR_PIC + /* In a PIC build, using _r_debug directly should give us the same + object. */ + TEST_VERIFY (&_r_debug == &debug->base); +#endif +#ifdef BUILD_FOR_NONPIC + TEST_COMPARE (_r_debug.r_version, 1); +#endif + void *h = xdlmopen (LM_ID_NEWLM, "$ORIGIN/tst-dlmopen1mod.so", RTLD_LAZY); @@ -64,6 +73,19 @@ do_test (void) const char *name = basename (debug->r_next->base.r_map->l_name); TEST_COMPARE_STRING (name, "tst-dlmopen1mod.so"); +#ifdef BUILD_FOR_NONPIC + /* If a copy relocation is used, it must be at version 1. */ + if (&_r_debug != &debug->base) + { + TEST_COMPARE (_r_debug.r_version, 1); + TEST_COMPARE ((uintptr_t) _r_debug.r_map, + (uintptr_t) debug->base.r_map); + TEST_COMPARE (_r_debug.r_brk, debug->base.r_brk); + TEST_COMPARE (_r_debug.r_state, debug->base.r_state); + TEST_COMPARE (_r_debug.r_ldbase, debug->base.r_ldbase); + } +#endif + xdlclose (h); return 0; diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 8ff06d6b02..4658636d71 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1137,6 +1137,10 @@ rtld_hidden_proto (_dl_debug_state) extern struct r_debug *_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns) attribute_hidden; +/* This is called after relocation processing to handle a potential + copy relocation for _r_debug. */ +void _dl_debug_post_relocate (struct link_map *main_map) attribute_hidden; + /* Update the `r_map' member and return the address of `struct r_debug' of the namespace NS. */ extern struct r_debug *_dl_debug_update (Lmid_t ns) attribute_hidden;