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;