From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-f179.google.com (mail-pg1-f179.google.com [209.85.215.179]) by sourceware.org (Postfix) with ESMTPS id 170E4385735B for ; Mon, 27 Jun 2022 17:53:07 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 170E4385735B Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=maskray.me Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pg1-f179.google.com with SMTP id d129so9766746pgc.9 for ; Mon, 27 Jun 2022 10:53:07 -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:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=MIQUmnIW93LhGoa2lTNwADrQNYlt0xOp4yyJ8GObEl4=; b=00YO0SoRqY2v8Q0s1s/UTJ15gqaMIFvR5pF/nnNXog6BVb3Jr26HVKd7k8SlowkWAc Vpp7NJoAuyw7xs0U/9bO+GNP2f0sXJfElKohkL+4kQlOwbUMU+ZdJVItRdMp6KiCTW4a 8Am2UqSj/Om/OECQm7odSLtfRcizBkiE38VKqFIuZ+8C8QznYjgP7PN8XJBMJ/BjPqt3 8LgyuZqnJ/9m1XTPj/nvA6XVFzwie3aRbxOyYootgkmS/eZi9A7CW6nDDcDQvqiNbvji UKdTTdK19F63aBeI7enQeHpAjv14BuFk1K6vB9/oi3nJkXETnXgzRYXEHa6ETIrU8F9v VOdA== X-Gm-Message-State: AJIora/mC+6IZ2a+lxJjwzco8c3J/Gv1vgXGHSbixRNDJ5YZK2J+YlJx 72+KzLt+zjR0ap8zqwr29fYJ1GsRaug= X-Google-Smtp-Source: AGRyM1vo5EYqviuGxNW/ogNxdQ9WOjj7EacOxA3VCkzU2tJXqqRal3KYHKPDQK0tc7rwuv0leemsdg== X-Received: by 2002:a05:6a00:1803:b0:525:6ed7:cdc4 with SMTP id y3-20020a056a00180300b005256ed7cdc4mr226790pfa.15.1656352385991; Mon, 27 Jun 2022 10:53:05 -0700 (PDT) Received: from localhost ([2601:647:6300:b760:896d:43da:187f:15b5]) by smtp.gmail.com with ESMTPSA id a23-20020a17090a6d9700b001eccb13dfb0sm9984228pjk.4.2022.06.27.10.53.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 27 Jun 2022 10:53:05 -0700 (PDT) Date: Mon, 27 Jun 2022 10:53:04 -0700 From: Fangrui Song To: "H.J. Lu" Cc: Binutils Subject: Re: [PATCH] x86: Make protected symbols local for -shared Message-ID: <20220627175304.pgmjcsxopjbq3gvn@gmail.com> References: <20220625174426.1475218-1-i@maskray.me> <20220626190301.44tptog54cqex4re@gmail.com> <20220627170903.nyi5lyjs4jubwbxs@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-7.6 required=5.0 tests=BAYES_00, FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM, GIT_PATCH_0, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, KAM_INFOUSMEBIZ, KAM_STOCKGEN, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, 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 X-BeenThere: binutils@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Binutils mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 27 Jun 2022 17:53:10 -0000 On 2022-06-27, H.J. Lu wrote: >On Mon, Jun 27, 2022 at 10:09 AM Fangrui Song wrote: >> >> On 2022-06-27, H.J. Lu wrote: >> >On Sun, Jun 26, 2022 at 12:03 PM Fangrui Song wrote: >> >> >> >> On 2022-06-26, H.J. Lu wrote: >> >> >On Sat, Jun 25, 2022 at 10:44 AM Fangrui Song wrote: >> >> >> >> >> >> Call _bfd_elf_symbol_refs_local_p with local_protected==true. This has >> >> >> 2 noticeable effects for -shared: >> >> >> >> >> >> * GOT-generating relocations referencing a protected data symbol no >> >> >> longer lead to a GLOB_DAT (similar to a hidden symbol). >> >> >> * Direct access relocations (e.g. R_X86_64_PC32) no longer has the >> >> >> confusing diagnostic below. >> >> >> >> >> >> __attribute__((visibility("protected"))) void *foo() { >> >> >> return (void *)foo; >> >> >> } >> >> >> >> >> >> // gcc -fpic -shared -fuse-ld=bfd >> >> >> relocation R_X86_64_PC32 against protected symbol `foo' can not be used when making a shared object >> >> >> >> >> >> The new behavior matches arm, aarch64 (commit >> >> >> 83c325007c5599fa9b60b8d5f7b84842160e1d1b), and powerpc ports, and other >> >> >> linkers: gold and ld.lld. >> >> >> >> >> >> Note: if some code tries to use direct access relocations to take the >> >> >> address of foo, the pointer equality will break, but the error should be >> >> >> reported on the executable link, not on the innocent shared object link. >> >> >> glibc 2.36 will give a warning at relocation resolving time. >> >> > >> >> >It should be controlled by -z [no]indirect-extern-access. Can you enable >> >> >-z indirect-extern-access with -shared by default instead? >> >> >> >> If I set `link_info.indirect_extern_access = 1;` in ld/ldmain.c, >> >> bfd/elf-properties.c:654 will create a >> >> GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS note. >> >> This will probably be unexpected (and check-ld will have 280+ failures). >> > >> >This is normal when the default behavior is changed. You can pass >> >-z noindirect-extern-access to these testcases. >> >> Adding GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS will be a >> significant behavior change and may unnecessarily break user programs >> (glibc will report an error instead of a warning). > >If glibc reports an error, it is a real bug with unknown consequences >when the copy in the executable is out of sync with the protected >symbol in the shared library, Not necessary. In glibc, GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS has two effects, 1 (copy relocations) and 2 (non-zero value of an undefined function symbol) on https://sourceware.org/pipermail/libc-alpha/2022-June/139552.html 2 does not necessarily cause a problem. In many cases it doesn't as function pointer equality is not an invariant a program relies upon (at least, for many functions, the property is not used). My previous comment has mentioned two cases. 1 likely causes a problem, but technically the shared object can define a protected data symbol without accessing it. >> If the executable takes the address of a protected function defined in a >> shared object, it may or may not cause a pointer equality problem (the >> shared object may not take the address) and the problem (if exists) may or >> may not be a broken invariance to the program (it may not expect pointer >> equality). >> >> All of aarch64/arm/powerpc64/riscv (likely most except x86, but I >> haven't enumerated) consider a protected data symbol local in -shared >> links. x86 did so a while ago (before 2015?). (For >> aarch64/arm/powerpc64/riscv, I wish that we never need >> GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS. The property will just >> waste some bytes in every shared object without carrying much >> information.) >> >> The 280+ failures in check-ld due to the default >> GNU_PROPERTY_1_NEEDED_INDIRECT_EXTERN_ACCESS need to be considered as >> well. >> >> >> >> With this change, `#define elf_backend_extern_protected_data 1` is no >> >> >> longer effective. Just remove it. >> >> >> >> >> >> Remove the test "Run protected-func-1 without PIE" since -fno-pic >> >> >> address taken operation in the executable doesn't work with protected >> >> >> symbol in a shared object by default. Similarly, remove >> >> >> protected-data-1a and protected-data-1b. protected-data-1b can be made >> >> >> working by removing HAVE_LD_PIE_COPYRELOC from GCC >> >> >> (https://sourceware.org/pipermail/gcc-patches/2022-June/596678.html). >> >> >> --- >> >> >> bfd/elf32-i386.c | 1 - >> >> >> bfd/elf64-x86-64.c | 1 - >> >> >> bfd/elfxx-x86.c | 2 +- >> >> >> ld/testsuite/ld-i386/protected1.d | 4 +++- >> >> >> ld/testsuite/ld-i386/protected3.d | 2 +- >> >> >> ld/testsuite/ld-i386/protected6a.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/pr24151a-x32.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/pr24151a.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/protected1.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/protected3.d | 2 +- >> >> >> ld/testsuite/ld-x86-64/protected6a.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/protected7a.d | 4 +++- >> >> >> ld/testsuite/ld-x86-64/x86-64.exp | 27 --------------------------- >> >> >> 13 files changed, 24 insertions(+), 39 deletions(-) >> >> >> >> >> >> diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c >> >> >> index e4106d9fd3b..c3c46795731 100644 >> >> >> --- a/bfd/elf32-i386.c >> >> >> +++ b/bfd/elf32-i386.c >> >> >> @@ -4424,7 +4424,6 @@ elf_i386_link_setup_gnu_properties (struct bfd_link_info *info) >> >> >> #define elf_backend_got_header_size 12 >> >> >> #define elf_backend_plt_alignment 4 >> >> >> #define elf_backend_dtrel_excludes_plt 1 >> >> >> -#define elf_backend_extern_protected_data 1 >> >> >> #define elf_backend_caches_rawsize 1 >> >> >> #define elf_backend_want_dynrelro 1 >> >> >> >> >> >> diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c >> >> >> index 6154a70bdd7..aaa5f1496b9 100644 >> >> >> --- a/bfd/elf64-x86-64.c >> >> >> +++ b/bfd/elf64-x86-64.c >> >> >> @@ -5275,7 +5275,6 @@ elf_x86_64_special_sections[]= >> >> >> #define elf_backend_got_header_size (GOT_ENTRY_SIZE*3) >> >> >> #define elf_backend_rela_normal 1 >> >> >> #define elf_backend_plt_alignment 4 >> >> >> -#define elf_backend_extern_protected_data 1 >> >> >> #define elf_backend_caches_rawsize 1 >> >> >> #define elf_backend_dtrel_excludes_plt 1 >> >> >> #define elf_backend_want_dynrelro 1 >> >> >> diff --git a/bfd/elfxx-x86.c b/bfd/elfxx-x86.c >> >> >> index acb2cc8528d..18f3d335458 100644 >> >> >> --- a/bfd/elfxx-x86.c >> >> >> +++ b/bfd/elfxx-x86.c >> >> >> @@ -3094,7 +3094,7 @@ _bfd_x86_elf_link_symbol_references_local (struct bfd_link_info *info, >> >> >> 2. When building executable, there is no dynamic linker. Or >> >> >> 3. or "-z nodynamic-undefined-weak" is used. >> >> >> */ >> >> >> - if (SYMBOL_REFERENCES_LOCAL (info, h) >> >> >> + if (_bfd_elf_symbol_refs_local_p (h, info, 1) >> >> >> || (h->root.type == bfd_link_hash_undefweak >> >> >> && (ELF_ST_VISIBILITY (h->other) != STV_DEFAULT >> >> >> || (bfd_link_executable (info) >> >> >> diff --git a/ld/testsuite/ld-i386/protected1.d b/ld/testsuite/ld-i386/protected1.d >> >> >> index a3cb5cef140..531645b8fe8 100644 >> >> >> --- a/ld/testsuite/ld-i386/protected1.d >> >> >> +++ b/ld/testsuite/ld-i386/protected1.d >> >> >> @@ -1,3 +1,5 @@ >> >> >> #as: --32 >> >> >> #ld: -shared -melf_i386 >> >> >> -#error: .*relocation R_386_GOTOFF against protected function `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-i386/protected3.d b/ld/testsuite/ld-i386/protected3.d >> >> >> index c3a6888d900..77367c4738f 100644 >> >> >> --- a/ld/testsuite/ld-i386/protected3.d >> >> >> +++ b/ld/testsuite/ld-i386/protected3.d >> >> >> @@ -8,7 +8,7 @@ >> >> >> Disassembly of section .text: >> >> >> >> >> >> 0+[a-f0-9]+ : >> >> >> -[ ]*[a-f0-9]+: 8b 81 [a-f0-9][a-f0-9] [a-f0-9][a-f0-9] ff ff mov -0x[a-f0-9]+\(%ecx\),%eax >> >> >> +[ ]*[a-f0-9]+: 8d 81 00 00 00 00 lea 0x0\(%ecx\),%eax >> >> >> [ ]*[a-f0-9]+: 8b 00 mov \(%eax\),%eax >> >> >> [ ]*[a-f0-9]+: c3 ret >> >> >> #pass >> >> >> diff --git a/ld/testsuite/ld-i386/protected6a.d b/ld/testsuite/ld-i386/protected6a.d >> >> >> index 7dc350432f4..4d3873239f9 100644 >> >> >> --- a/ld/testsuite/ld-i386/protected6a.d >> >> >> +++ b/ld/testsuite/ld-i386/protected6a.d >> >> >> @@ -1,4 +1,6 @@ >> >> >> #source: protected6.s >> >> >> #as: --32 >> >> >> #ld: -shared -melf_i386 >> >> >> -#error: .*relocation R_386_GOTOFF against protected data `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/pr24151a-x32.d b/ld/testsuite/ld-x86-64/pr24151a-x32.d >> >> >> index 130611ddf49..1f49b655f7d 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/pr24151a-x32.d >> >> >> +++ b/ld/testsuite/ld-x86-64/pr24151a-x32.d >> >> >> @@ -1,4 +1,6 @@ >> >> >> #source: pr24151a.s >> >> >> #as: --x32 >> >> >> #ld: -shared -melf32_x86_64 >> >> >> -#error: .*relocation R_X86_64_PC32 against protected symbol `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/pr24151a.d b/ld/testsuite/ld-x86-64/pr24151a.d >> >> >> index 783b85a1a6f..6c48e383e01 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/pr24151a.d >> >> >> +++ b/ld/testsuite/ld-x86-64/pr24151a.d >> >> >> @@ -1,3 +1,5 @@ >> >> >> #as: --64 >> >> >> #ld: -shared -melf_x86_64 >> >> >> -#error: .*relocation R_X86_64_PC32 against protected symbol `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/protected1.d b/ld/testsuite/ld-x86-64/protected1.d >> >> >> index 783b85a1a6f..6c48e383e01 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/protected1.d >> >> >> +++ b/ld/testsuite/ld-x86-64/protected1.d >> >> >> @@ -1,3 +1,5 @@ >> >> >> #as: --64 >> >> >> #ld: -shared -melf_x86_64 >> >> >> -#error: .*relocation R_X86_64_PC32 against protected symbol `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/protected3.d b/ld/testsuite/ld-x86-64/protected3.d >> >> >> index 57950e4d6b6..ba63991582f 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/protected3.d >> >> >> +++ b/ld/testsuite/ld-x86-64/protected3.d >> >> >> @@ -8,7 +8,7 @@ >> >> >> Disassembly of section .text: >> >> >> >> >> >> 0+[a-f0-9]+ : >> >> >> -[ ]*[a-f0-9]+: 48 8b 05 ([0-9a-f]{2} ){4} * mov 0x[a-f0-9]+\(%rip\),%rax # [a-f0-9]+ <.*> >> >> >> +[ ]*[a-f0-9]+: 48 8d 05 ([0-9a-f]{2} ){4} * lea 0x[a-f0-9]+\(%rip\),%rax # [a-f0-9]+ <.*> >> >> >> [ ]*[a-f0-9]+: 8b 00 mov \(%rax\),%eax >> >> >> [ ]*[a-f0-9]+: c3 ret >> >> >> #pass >> >> >> diff --git a/ld/testsuite/ld-x86-64/protected6a.d b/ld/testsuite/ld-x86-64/protected6a.d >> >> >> index 3a7963ffd2f..50d6430b577 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/protected6a.d >> >> >> +++ b/ld/testsuite/ld-x86-64/protected6a.d >> >> >> @@ -1,4 +1,6 @@ >> >> >> #source: protected6.s >> >> >> #as: --64 >> >> >> #ld: -shared -melf_x86_64 >> >> >> -#error: .*relocation R_X86_64_GOTOFF64 against protected data `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/protected7a.d b/ld/testsuite/ld-x86-64/protected7a.d >> >> >> index 3082084a7b8..3974246a2a8 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/protected7a.d >> >> >> +++ b/ld/testsuite/ld-x86-64/protected7a.d >> >> >> @@ -1,4 +1,6 @@ >> >> >> #source: protected7.s >> >> >> #as: --64 >> >> >> #ld: -shared -melf_x86_64 >> >> >> -#error: .*relocation R_X86_64_GOTOFF64 against protected function `foo' can not be used when making a shared object >> >> >> +#readelf: -rW >> >> >> +#... >> >> >> +There are no relocations in this file. >> >> >> diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp >> >> >> index 5e5636bcebe..a096c0b9d0f 100644 >> >> >> --- a/ld/testsuite/ld-x86-64/x86-64.exp >> >> >> +++ b/ld/testsuite/ld-x86-64/x86-64.exp >> >> >> @@ -1832,15 +1832,6 @@ if { [isnative] && [check_compiler_available] } { >> >> >> "pr23997" \ >> >> >> "pass.out" \ >> >> >> ] \ >> >> >> - [list \ >> >> >> - "Run protected-func-1 without PIE" \ >> >> >> - "$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libprotected-func-1.so" \ >> >> >> - "-Wa,-mx86-used-note=yes" \ >> >> >> - { protected-func-1b.c } \ >> >> >> - "protected-func-1a" \ >> >> >> - "pass.out" \ >> >> >> - "$NOPIE_CFLAGS" \ >> >> >> - ] \ >> >> >> [list \ >> >> >> "Run protected-func-1 with PIE" \ >> >> >> "-Wl,--no-as-needed -pie tmpdir/libprotected-func-1.so" \ >> >> >> @@ -1904,24 +1895,6 @@ if { [isnative] && [check_compiler_available] } { >> >> >> "pass.out" \ >> >> >> "-fPIE" \ >> >> >> ] \ >> >> >> - [list \ >> >> >> - "Run protected-data-1a without PIE" \ >> >> >> - "$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libprotected-data-1a.so" \ >> >> >> - "-Wa,-mx86-used-note=yes" \ >> >> >> - { protected-data-1b.c } \ >> >> >> - "protected-data-1a" \ >> >> >> - "pass.out" \ >> >> >> - "$NOPIE_CFLAGS" \ >> >> >> - ] \ >> >> >> - [list \ >> >> >> - "Run protected-data-1b with PIE" \ >> >> >> - "-Wl,--no-as-needed -pie tmpdir/libprotected-data-1a.so" \ >> >> >> - "-Wa,-mx86-used-note=yes" \ >> >> >> - { protected-data-1b.c } \ >> >> >> - "protected-data-1b" \ >> >> >> - "pass.out" \ >> >> >> - "-fPIE" \ >> >> >> - ] \ >> >> >> [list \ >> >> >> "Run protected-data-2a without PIE" \ >> >> >> "$NOPIE_LDFLAGS -Wl,--no-as-needed tmpdir/libprotected-data-2a.so" \ >> >> >> -- >> >> >> 2.37 >> >> >> >> >> > >> >> > >> >> >-- >> >> >H.J. >> > >> > >> > >> >-- >> >H.J. > > > >-- >H.J.