From patchwork Wed Jun 1 04:50:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fangrui Song X-Patchwork-Id: 1637737 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: bilbo.ozlabs.org; dkim=pass (1024-bit key; secure) header.d=sourceware.org header.i=@sourceware.org header.a=rsa-sha256 header.s=default header.b=POY/Eldc; dkim-atps=neutral Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=sourceware.org (client-ip=8.43.85.97; helo=sourceware.org; envelope-from=libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org; receiver=) Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by bilbo.ozlabs.org (Postfix) with ESMTPS id 4LCcDD1l9fz9s0r for ; Wed, 1 Jun 2022 14:51:08 +1000 (AEST) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id ADB9F3856DD4 for ; Wed, 1 Jun 2022 04:51:05 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org ADB9F3856DD4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1654059065; bh=EghgaIezPM9Vk11oetR2WrckrL3k1w0z6sHTrPZr3yw=; h=Date:Subject:To:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=POY/EldcED4n9D7TaL0IfdxOxQchkj4mdJL8ipNCs3JdfZpz955kx8PbCpjkC8ykD zdlfsbOCm43rqEeUduiCHxon/IL9dZNyKDnWDkMDfbkhD30N4MM6HyUl/tC50Y+rCG uNtoGmHh0Y/AFGmQ4Nen2dB5OLKWXr+ifaPZMO04= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by sourceware.org (Postfix) with ESMTPS id D55503858430 for ; Wed, 1 Jun 2022 04:50:49 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D55503858430 Received: by mail-yb1-xb4a.google.com with SMTP id i204-20020a2522d5000000b006524ae5d7d7so495991ybi.16 for ; Tue, 31 May 2022 21:50:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=EghgaIezPM9Vk11oetR2WrckrL3k1w0z6sHTrPZr3yw=; b=2jVtz2nKJsS1RFOySjFiYGzq9nDlhmkfr12aNZ038YkimmjHPt84yatFrLVPir/chf gpBVqPUqDJFGZtW2Gq5tEMEcUMNNHYhjLJZJSB1ISv1yYUnoDc5fh1AN9W18WwzFtYJT AzZUHt3gm/NihLd4/ywjN84CZHTeiJEY/rNYWdMWdeJxkHu3h0AyhynRWUmgXMpuvHPj DAlyjcn7Ijr7php2qnfvx1vla68PiLaDXPpYA3G01Tj09wOyuf/h/7On4Vwq+EgKBjr5 uh1XzNpMiMlMRHTsfOkFHMWx9giznmPLkMd41g90uw5qzcER/bu9YTC852SpYWKUJpbq csaA== X-Gm-Message-State: AOAM533lfYjXq67n/g3alP6zqNakjQjn7MZmk8g3VmWmRBnY9N0gBnDl 7myuvIDvxlAFYmC9XG4GIC+hnJTayWGDvL945bLjo9VwjjPEpzjF9gbnruFN44hR4UC5a7ZCRiq IiSbtoHShBFt9+WxExN/vxa55AKhWeS9IjIkfxiu0wQsukAg8UO97Ta81Odblvd0KgAMG X-Google-Smtp-Source: ABdhPJzL1vYspiygGQETok67tpKD4793r8ST4LZ1ry416Ra/fOnKqyfio+BSa3X2bZSuVN68S4Ba34JMGXph X-Received: from maskray1.svl.corp.google.com ([2620:15c:2ce:200:d5a8:eb1:a3e6:329f]) (user=maskray job=sendgmr) by 2002:a25:d50f:0:b0:64a:784b:960 with SMTP id r15-20020a25d50f000000b0064a784b0960mr61201055ybe.318.1654059049143; Tue, 31 May 2022 21:50:49 -0700 (PDT) Date: Tue, 31 May 2022 21:50:33 -0700 Message-Id: <20220601045033.809671-1-maskray@google.com> Mime-Version: 1.0 Subject: [PATCH v2] elf: Remove ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA To: libc-alpha@sourceware.org, Szabolcs Nagy X-Spam-Status: No, score=-19.6 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) 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: Fangrui Song via Libc-alpha From: Fangrui Song Reply-To: Fangrui Song Errors-To: libc-alpha-bounces+incoming=patchwork.ozlabs.org@sourceware.org Sender: "Libc-alpha" If an executable has copy relocations for extern protected data, that can only work if the library containing the definition is built with assumptions (a) the compiler emits GOT-generating relocations (b) the linker produces R_*_GLOB_DAT instead of R_*_RELATIVE. Otherwise the library uses its own definition directly and the executable accesses a stale copy. Note: the GOT relocations defeat the purpose of protected visibility as an optimization, but allow rtld to make the executable and library use the same copy when copy relocations are present, but it turns out this never worked perfectly. ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA has strange semantics when both a.so and b.so define protected var and the executable copy relocates var: b.so accesses its own copy even with GLOB_DAT. The behavior change is from commit 62da1e3b00b51383ffa7efc89d8addda0502e107 (x86) and then copied to nios2 (ae5eae7cfc9c4a8297ff82ec6b794faca1976ecc) and arc (0e7d930c4c11de896fe807f67fa1eb756c9c1e05). Without ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA, b.so accesses the copy relocated data like a.so. It's extremely unlikely anyone relies on the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA behavior, so let's remove it. --- Changes from v1: * Reword commit message as suggested by Szabolcs Nagy --- elf/dl-lookup.c | 90 ------------------------------------- sysdeps/arc/dl-sysdep.h | 21 --------- sysdeps/generic/ldsodefs.h | 12 +---- sysdeps/i386/dl-machine.h | 3 +- sysdeps/nios2/dl-sysdep.h | 21 --------- sysdeps/x86/dl-lookupcfg.h | 4 -- sysdeps/x86_64/dl-machine.h | 8 +--- 7 files changed, 4 insertions(+), 155 deletions(-) delete mode 100644 sysdeps/arc/dl-sysdep.h delete mode 100644 sysdeps/nios2/dl-sysdep.h diff --git a/elf/dl-lookup.c b/elf/dl-lookup.c index a42f6d5390..41d108e0b8 100644 --- a/elf/dl-lookup.c +++ b/elf/dl-lookup.c @@ -456,59 +456,6 @@ do_lookup_x (const char *undef_name, unsigned int new_hash, if (sym != NULL) { found_it: - /* When UNDEF_MAP is NULL, which indicates we are called from - do_lookup_x on relocation against protected data, we skip - the data definion in the executable from copy reloc. */ - if (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA - && undef_map == NULL - && map->l_type == lt_executable - && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA) - { - const ElfW(Sym) *s; - unsigned int i; - -#if ! ELF_MACHINE_NO_RELA - if (map->l_info[DT_RELA] != NULL - && map->l_info[DT_RELASZ] != NULL - && map->l_info[DT_RELASZ]->d_un.d_val != 0) - { - const ElfW(Rela) *rela - = (const ElfW(Rela) *) D_PTR (map, l_info[DT_RELA]); - unsigned int rela_count - = map->l_info[DT_RELASZ]->d_un.d_val / sizeof (*rela); - - for (i = 0; i < rela_count; i++, rela++) - if (elf_machine_type_class (ELFW(R_TYPE) (rela->r_info)) - == ELF_RTYPE_CLASS_COPY) - { - s = &symtab[ELFW(R_SYM) (rela->r_info)]; - if (!strcmp (strtab + s->st_name, undef_name)) - goto skip; - } - } -#endif -#if ! ELF_MACHINE_NO_REL - if (map->l_info[DT_REL] != NULL - && map->l_info[DT_RELSZ] != NULL - && map->l_info[DT_RELSZ]->d_un.d_val != 0) - { - const ElfW(Rel) *rel - = (const ElfW(Rel) *) D_PTR (map, l_info[DT_REL]); - unsigned int rel_count - = map->l_info[DT_RELSZ]->d_un.d_val / sizeof (*rel); - - for (i = 0; i < rel_count; i++, rel++) - if (elf_machine_type_class (ELFW(R_TYPE) (rel->r_info)) - == ELF_RTYPE_CLASS_COPY) - { - s = &symtab[ELFW(R_SYM) (rel->r_info)]; - if (!strcmp (strtab + s->st_name, undef_name)) - goto skip; - } - } -#endif - } - /* Hidden and internal symbols are local, ignore them. */ if (__glibc_unlikely (dl_symbol_visibility_binds_local_p (sym))) goto skip; @@ -854,43 +801,6 @@ _dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map, return 0; } - int protected = (*ref - && ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED); - if (__glibc_unlikely (protected != 0)) - { - /* It is very tricky. We need to figure out what value to - return for the protected symbol. */ - if (type_class == ELF_RTYPE_CLASS_PLT) - { - if (current_value.s != NULL && current_value.m != undef_map) - { - current_value.s = *ref; - current_value.m = undef_map; - } - } - else - { - struct sym_val protected_value = { NULL, NULL }; - - for (scope = symbol_scope; *scope != NULL; i = 0, ++scope) - if (do_lookup_x (undef_name, new_hash, &old_hash, *ref, - &protected_value, *scope, i, version, flags, - skip_map, - (ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA - && ELFW(ST_TYPE) ((*ref)->st_info) == STT_OBJECT - && type_class == ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA) - ? ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA - : ELF_RTYPE_CLASS_PLT, NULL) != 0) - break; - - if (protected_value.s != NULL && protected_value.m != undef_map) - { - current_value.s = *ref; - current_value.m = undef_map; - } - } - } - /* We have to check whether this would bind UNDEF_MAP to an object in the global scope which was dynamically loaded. In this case we have to prevent the latter from being unloaded unless the diff --git a/sysdeps/arc/dl-sysdep.h b/sysdeps/arc/dl-sysdep.h deleted file mode 100644 index cf4d160a73..0000000000 --- a/sysdeps/arc/dl-sysdep.h +++ /dev/null @@ -1,21 +0,0 @@ -/* System-specific settings for dynamic linker code. ARC version. - Copyright (C) 2020-2022 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 - . */ - -#include_next - -#define DL_EXTERN_PROTECTED_DATA diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h index 6716e1f382..d3cbfd4f95 100644 --- a/sysdeps/generic/ldsodefs.h +++ b/sysdeps/generic/ldsodefs.h @@ -149,23 +149,13 @@ dl_symbol_visibility_binds_local_p (const ElfW(Sym) *sym) satisfied by any symbol in the executable. Some architectures do not support copy relocations. In this case we define the macro to zero so that the code for handling them gets automatically optimized - out. ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA means address of protected - data defined in the shared library may be external, i.e., due to copy - relocation. */ + out. */ #define ELF_RTYPE_CLASS_PLT 1 #ifndef DL_NO_COPY_RELOCS # define ELF_RTYPE_CLASS_COPY 2 #else # define ELF_RTYPE_CLASS_COPY 0 #endif -/* If DL_EXTERN_PROTECTED_DATA is defined, address of protected data - defined in the shared library may be external, i.e., due to copy - relocation. */ -#ifdef DL_EXTERN_PROTECTED_DATA -# define ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA 4 -#else -# define ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA 0 -#endif /* ELF uses the PF_x macros to specify the segment permissions, mmap uses PROT_xxx. In most cases the three macros have the values 1, 2, diff --git a/sysdeps/i386/dl-machine.h b/sysdeps/i386/dl-machine.h index 1f8d734215..3311631a3e 100644 --- a/sysdeps/i386/dl-machine.h +++ b/sysdeps/i386/dl-machine.h @@ -203,8 +203,7 @@ _dl_start_user:\n\ || (type) == R_386_TLS_DTPOFF32 || (type) == R_386_TLS_TPOFF32 \ || (type) == R_386_TLS_TPOFF || (type) == R_386_TLS_DESC) \ * ELF_RTYPE_CLASS_PLT) \ - | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY) \ - | (((type) == R_386_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)) + | (((type) == R_386_COPY) * ELF_RTYPE_CLASS_COPY)) /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */ #define ELF_MACHINE_JMP_SLOT R_386_JMP_SLOT diff --git a/sysdeps/nios2/dl-sysdep.h b/sysdeps/nios2/dl-sysdep.h deleted file mode 100644 index 257b37c258..0000000000 --- a/sysdeps/nios2/dl-sysdep.h +++ /dev/null @@ -1,21 +0,0 @@ -/* System-specific settings for dynamic linker code. Nios II version. - Copyright (C) 2009-2022 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 - . */ - -#include_next - -#define DL_EXTERN_PROTECTED_DATA diff --git a/sysdeps/x86/dl-lookupcfg.h b/sysdeps/x86/dl-lookupcfg.h index 18b3b49f6e..e136cc63af 100644 --- a/sysdeps/x86/dl-lookupcfg.h +++ b/sysdeps/x86/dl-lookupcfg.h @@ -20,10 +20,6 @@ #include_next -/* Address of protected data defined in the shared library may be - external due to copy relocation. */ -#define DL_EXTERN_PROTECTED_DATA - struct link_map; extern void _dl_unmap (struct link_map *map) attribute_hidden; diff --git a/sysdeps/x86_64/dl-machine.h b/sysdeps/x86_64/dl-machine.h index 7f607f6dff..78aecfc9fd 100644 --- a/sysdeps/x86_64/dl-machine.h +++ b/sysdeps/x86_64/dl-machine.h @@ -181,10 +181,7 @@ _dl_start_user:\n\ TLS variable, so undefined references should not be allowed to define the value. ELF_RTYPE_CLASS_COPY iff TYPE should not be allowed to resolve to one - of the main executable's symbols, as for a COPY reloc. - ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA iff TYPE describes relocation may - against protected data whose address be external due to copy relocation. - */ + of the main executable's symbols, as for a COPY reloc. */ #define elf_machine_type_class(type) \ ((((type) == R_X86_64_JUMP_SLOT \ || (type) == R_X86_64_DTPMOD64 \ @@ -192,8 +189,7 @@ _dl_start_user:\n\ || (type) == R_X86_64_TPOFF64 \ || (type) == R_X86_64_TLSDESC) \ * ELF_RTYPE_CLASS_PLT) \ - | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY) \ - | (((type) == R_X86_64_GLOB_DAT) * ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA)) + | (((type) == R_X86_64_COPY) * ELF_RTYPE_CLASS_COPY)) /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries. */ #define ELF_MACHINE_JMP_SLOT R_X86_64_JUMP_SLOT