From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id A4DD73851172 for ; Tue, 6 Sep 2022 10:27:38 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org A4DD73851172 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1662460058; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=WNmyGVglKjDBh66eEMzTpXNyet/gA742sBedSfPmTHM=; b=X9MrA/N3vcJ0XHuUiRr3JP6Bqd7u5vn91t7xsy47MiAy9T742aJMS0sxAHlVFjGkU6XbIe h6Mokxs9F6gkBuy9WbB2pGj6ZWhsvrAIOSzE0idSKtheRPhUnqbv56cbB0ErHkPtw38J0c vBAhekK0ktYh4irSrAlqcSsFnlshy1o= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-583-HUNTg5RiNNm1sEYpkDEt2Q-1; Tue, 06 Sep 2022 06:27:37 -0400 X-MC-Unique: HUNTg5RiNNm1sEYpkDEt2Q-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8CF96805B98 for ; Tue, 6 Sep 2022 10:27:36 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.109]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 95CCA9458A for ; Tue, 6 Sep 2022 10:27:35 +0000 (UTC) From: Florian Weimer To: libc-alpha@sourceware.org Subject: [PATCH v2 3/3] elf: Restore support for _r_debug interpositions and copy relocations In-Reply-To: References: X-From-Line: 564187d57abfb2aa436d2facb6965336fc8e0a4e Mon Sep 17 00:00:00 2001 Message-Id: <564187d57abfb2aa436d2facb6965336fc8e0a4e.1662456433.git.fweimer@redhat.com> Date: Tue, 06 Sep 2022 12:27:34 +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 10.11.54.5 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-10.3 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,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: The changes in commit a93d9e03a31ec14405cb3a09aa95413b67067380 ("Extend struct r_debug to support multiple namespaces [BZ #15971]") break the dyninst dynamic instrumentation tool. It brings its own definition of _r_debug (rather than a declaration). Furthermore, it turns out it is rather hard to use the proposed handshake for accessing _r_debug via DT_DEBUG. If applications want to access _r_debug, they can do so directly if the relevant code has been built as PIC. To protect against harm from accidental copy relocations due to linker relaxations, this commit restores copy relocation support by adjusting both copies if interposition or copy relocations are in play. --- elf/Makefile | 9 +++++++ elf/dl-debug.c | 52 +++++++++++++++++++++++++++++++++++--- elf/rtld.c | 3 +++ 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, 91 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 008770bfaf..62a3e3e88d 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -408,6 +408,8 @@ tests += \ tst-dlmopen1 \ tst-dlmopen3 \ tst-dlmopen4 \ + tst-dlmopen4-nonpic \ + tst-dlmopen4-pic \ tst-dlmopen-dlerror \ tst-dlmopen-gethostbyname \ tst-dlmopen-twice \ @@ -1998,6 +2000,13 @@ $(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 47961236cf..2762e01c16 100644 --- a/elf/dl-debug.c +++ b/elf/dl-debug.c @@ -16,6 +16,7 @@ License along with the GNU C Library; if not, see . */ +#include #include @@ -37,6 +38,37 @@ 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) +{ + /* Perform a full symbol search in all objects, to maintain + compatibility if interposed _r_debug definitions. The lookup + cannot faul because there is a definition in ld.so. */ + const ElfW(Sym) *sym = NULL; + lookup_t result =_dl_lookup_symbol_x ("_r_debug", main_map, &sym, + main_map->l_scope, NULL, 0, 0, NULL); + assert (sym != NULL); + if (sym->st_size >= sizeof (struct r_debug)) + { + struct r_debug *main_r_debug = DL_SYMBOL_ADDRESS (result, 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 +103,11 @@ 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 +140,9 @@ _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 +155,15 @@ _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_public *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 ad67d7e4c5..40aed9d2c4 100644 --- a/elf/rtld.c +++ b/elf/rtld.c @@ -2334,6 +2334,9 @@ dl_main (const ElfW(Phdr) *phdr, /* We must prepare the profiling. */ _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 8456f89053..6db928950d 100644 --- a/elf/tst-dlmopen4.c +++ b/elf/tst-dlmopen4.c @@ -46,6 +46,15 @@ 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); @@ -57,6 +66,19 @@ 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 31fb19c871..341f48a7ae 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -1071,6 +1071,10 @@ 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; -- 2.37.2