From patchwork Sat May 28 04:42:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fangrui Song X-Patchwork-Id: 54476 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 20C69384A876 for ; Sat, 28 May 2022 04:43:19 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 20C69384A876 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1653712999; bh=5GjnMWLNCJDJptEk9ed180b+MWCZIWvOd+kV1J+QbSM=; h=Date:Subject:To:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:From; b=xAVVjtGsJlpJqQ39A5EvwX0UjQ74ldJ67U+doEvsTSbxnQDJVrSmsl86gq3wf9goy PjsCfYC3yTgy068dXhCAnxjqpJqYlc2d39Yv7Mr9NdpgsfyqFHFeNfs6qO2A7WXoRa +BJKKGqaABzq2A5ulDCHZaOz/I1NB7R7336COPMg= X-Original-To: libc-alpha@sourceware.org Delivered-To: libc-alpha@sourceware.org Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by sourceware.org (Postfix) with ESMTPS id 0087C3857410 for ; Sat, 28 May 2022 04:42:55 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 0087C3857410 Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-2dc7bdd666fso54275757b3.7 for ; Fri, 27 May 2022 21:42:55 -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=5GjnMWLNCJDJptEk9ed180b+MWCZIWvOd+kV1J+QbSM=; b=UyUSoLRj0USlTGdfrwebjJKf0sM7/+8cTtqhn/dmjIyp3RS3IiiX3RaOzMKU9QFKZg Uje/7Q6TU9s3sWLSzC7qupyIA9L1qCLB67uO5P2lpG5XIeMwrYJXQizpmYnpzAmUPueQ y3P7ab7vUtRAcK8H3jMfC8lS5zMV2woq+gC5TmiQYGqGTcQ9R2Afn6pkGbFCVoBEHNpE McNONGrz6qWPSPHXHlaxLh2k+WAAhdKUTdU3Elp8ZeYr3xF8+p/1/ymacYIxyPMDrk18 nyzC9VSXWGdh2voem7NzWeuq2Gk5ZLoFYyyhYvUDTrZ5Vvy55TXxQGghEVAW5ckc1zUN t8QQ== X-Gm-Message-State: AOAM530Y4VLu3+wT+8C/ZUvpLA5N+ZM6SjWJWre/GlXKBddsQvfpK7sz vPh9O7YB0AFoNb3O9+nX6G4rsU8DMQD3EQnqdmtVfaZ8Mq6fUjJTfReuGEyLkQrQGj9J4LdvP5s JX8eSrh8wUpfAuH1c5+4kjO9i29Y5O9y3NAeYQWWrisqWzkoJY/gKKW3r3qMoBPRyorql X-Google-Smtp-Source: ABdhPJyy6VxI/vroyG715VbVBGlijPyPt/5F6LRDOh3z3CrAQrF9Za9nmwiv7jLf/f3FlNbFlb5asU+4yx8m X-Received: from maskray1.svl.corp.google.com ([2620:15c:2ce:200:781f:286a:7724:6870]) (user=maskray job=sendgmr) by 2002:a5b:312:0:b0:633:75de:5ab4 with SMTP id j18-20020a5b0312000000b0063375de5ab4mr46274482ybp.124.1653712975324; Fri, 27 May 2022 21:42:55 -0700 (PDT) Date: Fri, 27 May 2022 21:42:25 -0700 Message-Id: <20220528044225.1312621-1-maskray@google.com> Mime-Version: 1.0 Subject: [PATCH] elf: Remove ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA To: libc-alpha@sourceware.org X-Spam-Status: No, score=-19.5 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+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" Say both a.so and b.so define protected var and the executable copy relocates var. ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA has strange semantics: a.so accesses the copy in the executable while b.so accesses its own. This behavior requires that (a) the compiler emits GOT-generating relocations (b) the linker produces GLOB_DAT instead of RELATIVE. The behavior change is from commit 62da1e3b00b51383ffa7efc89d8addda0502e107 (x86) and then copied to nios2 (ae5eae7cfc9c4a8297ff82ec6b794faca1976ecc) and arc (0e7d930c4c11de896fe807f67fa1eb756c9c1e05). Without the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA code, b.so's GLOB_DAT will bind to the executable (normal behavior). It's extremely unlikely anyone relies on the ELF_RTYPE_CLASS_EXTERN_PROTECTED_DATA behavior, so just remove it. --- 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