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(localhost [IPv6:::1]) by gnu-tgl-3.localdomain (Postfix) with ESMTP id 20DADC0EDD; Sat, 8 Jan 2022 10:38:39 -0800 (PST) To: binutils@sourceware.org Subject: [PATCH v2 4/9] ld: Initial DT_RELR support Date: Sat, 8 Jan 2022 10:38:33 -0800 Message-Id: <20220108183838.1920397-5-hjl.tools@gmail.com> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20220108183838.1920397-1-hjl.tools@gmail.com> References: <20220108183838.1920397-1-hjl.tools@gmail.com> MIME-Version: 1.0 X-Spam-Status: No, score=-3028.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, RCVD_IN_BARRACUDACENTRAL, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, 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: "H.J. Lu via Libc-alpha" From: "H.J. Lu" Reply-To: "H.J. Lu" Cc: libc-alpha@sourceware.org, Nick Clifton , Alan Modra Errors-To: libc-alpha-bounces+patchwork=sourceware.org@sourceware.org Sender: "Libc-alpha" Add a -z pack-relative-relocs option to enable DT_RELR and create a relr.dyn section for DT_RELR. DT_RELR is implemented with the linker relaxation infrastructure, but it doesn't require the --relax option enabled. -z pack-relative-relocs implies -z combreloc. -z nocombreloc implies -z nopack-relative-relocs. -z pack-relative-relocs is chosen over the similar option in lld, --pack-dyn-relocs=relr, to implement a glibc binary lockout mechanism with a special glibc version symbol, to avoid random crashes of DT_RELR binaries with the existing glibc binaries. bfd/ * elf-bfd.h (elf_link_hash_table): Add srelrdyn. * elflink.c (_bfd_elf_link_create_dynamic_sections): Create a .relr.dyn section for DT_RELR. include/ * bfdlink.h (bfd_link_info): Add enable_dt_relr. ld/ * News: Mention -z pack-relative-relocs and -z nopack-relative-relocs. * ld.texi: Document -z pack-relative-relocs and -z nopack-relative-relocs. * ldelf.c (ldelf_after_parse): Disable DT_RELR if not building PIE nor shared library. Add 3 spare dynamic tags for DT_RELR, DT_RELRSZ and DT_RELRENT. * ldlang.c (lang_relax_sections): Also enable relaxation if DT_RELR is enabled. * emulparams/elf32_x86_64.sh: Source dt-relr.sh. * emulparams/elf_i386.sh: Likewise. * emulparams/elf_x86_64.sh: Likewise. * emulparams/dt-relr.sh: New file. * emultempl/elf.em (gld${EMULATION_NAME}_handle_option): Disable DT_RELR for -z nocombreloc. * scripttempl/elf.sc: Support .relr.dyn. --- bfd/elf-bfd.h | 1 + bfd/elflink.c | 11 +++++++++++ include/bfdlink.h | 4 ++++ ld/NEWS | 3 +++ ld/emulparams/dt-relr.sh | 21 +++++++++++++++++++++ ld/emulparams/elf32_x86_64.sh | 1 + ld/emulparams/elf_i386.sh | 1 + ld/emulparams/elf_x86_64.sh | 1 + ld/emultempl/elf.em | 5 ++++- ld/ld.texi | 11 +++++++++++ ld/ldelf.c | 9 +++++++++ ld/ldlang.c | 3 ++- ld/scripttempl/elf.sc | 4 ++++ 13 files changed, 73 insertions(+), 2 deletions(-) create mode 100644 ld/emulparams/dt-relr.sh diff --git a/bfd/elf-bfd.h b/bfd/elf-bfd.h index c4d2ef00d6b..4e73d79ee77 100644 --- a/bfd/elf-bfd.h +++ b/bfd/elf-bfd.h @@ -707,6 +707,7 @@ struct elf_link_hash_table asection *irelplt; asection *irelifunc; asection *dynsym; + asection *srelrdyn; }; /* Returns TRUE if the hash table is a struct elf_link_hash_table. */ diff --git a/bfd/elflink.c b/bfd/elflink.c index bea413ec24e..d51b00b6c10 100644 --- a/bfd/elflink.c +++ b/bfd/elflink.c @@ -359,6 +359,17 @@ _bfd_elf_link_create_dynamic_sections (bfd *abfd, struct bfd_link_info *info) elf_section_data (s)->this_hdr.sh_entsize = 4; } + if (info->enable_dt_relr) + { + s = bfd_make_section_anyway_with_flags (abfd, ".relr.dyn", + (bed->dynamic_sec_flags + | SEC_READONLY)); + if (s == NULL + || !bfd_set_section_alignment (s, bed->s->log_file_align)) + return false; + elf_hash_table (info)->srelrdyn = s; + } + /* Let the backend create the rest of the sections. This lets the backend set the right flags. The backend will normally create the .got and .plt sections. */ diff --git a/include/bfdlink.h b/include/bfdlink.h index 01f57c22edf..92e3e32360b 100644 --- a/include/bfdlink.h +++ b/include/bfdlink.h @@ -413,6 +413,10 @@ struct bfd_link_info /* TRUE if PT_GNU_RELRO segment should be created. */ unsigned int relro: 1; + /* TRUE if DT_RELR should be enabled for compact relative + relocations. */ + unsigned int enable_dt_relr: 1; + /* TRUE if separate code segment should be created. */ unsigned int separate_code: 1; diff --git a/ld/NEWS b/ld/NEWS index 5d3d80dbbba..77c716b577d 100644 --- a/ld/NEWS +++ b/ld/NEWS @@ -1,5 +1,8 @@ -*- text -*- +* Add -z pack-relative-relocs/-z no pack-relative-relocs to x86 ELF + linker to pack relative relocations in the DT_RELR section. + * Add support for the LoongArch architecture. * Add -z indirect-extern-access/-z noindirect-extern-access to x86 ELF diff --git a/ld/emulparams/dt-relr.sh b/ld/emulparams/dt-relr.sh new file mode 100644 index 00000000000..ed93ee2b5c2 --- /dev/null +++ b/ld/emulparams/dt-relr.sh @@ -0,0 +1,21 @@ +HAVE_DT_RELR=yes +PARSE_AND_LIST_OPTIONS_PACK_RELATIVE_RELOCS=' + fprintf (file, _("\ + -z pack-relative-relocs Pack relative relocations\n")); + fprintf (file, _("\ + -z nopack-relative-relocs Do not pack relative relocations (default)\n")); +' + +PARSE_AND_LIST_ARGS_CASE_Z_PACK_RELATIVE_RELOCS=' + else if (strcmp (optarg, "pack-relative-relocs") == 0) + { + link_info.enable_dt_relr = true; + link_info.combreloc = true; + } + else if (strcmp (optarg, "nopack-relative-relocs") == 0) + link_info.enable_dt_relr = false; +' + + +PARSE_AND_LIST_OPTIONS="$PARSE_AND_LIST_OPTIONS $PARSE_AND_LIST_OPTIONS_PACK_RELATIVE_RELOCS" +PARSE_AND_LIST_ARGS_CASE_Z="$PARSE_AND_LIST_ARGS_CASE_Z $PARSE_AND_LIST_ARGS_CASE_Z_PACK_RELATIVE_RELOCS" diff --git a/ld/emulparams/elf32_x86_64.sh b/ld/emulparams/elf32_x86_64.sh index ac0a7aa6dcf..4bff41287c1 100644 --- a/ld/emulparams/elf32_x86_64.sh +++ b/ld/emulparams/elf32_x86_64.sh @@ -7,6 +7,7 @@ source_sh ${srcdir}/emulparams/cet.sh source_sh ${srcdir}/emulparams/x86-report-relative.sh source_sh ${srcdir}/emulparams/x86-64-level.sh source_sh ${srcdir}/emulparams/static.sh +source_sh ${srcdir}/emulparams/dt-relr.sh SCRIPT_NAME=elf ELFSIZE=32 OUTPUT_FORMAT="elf32-x86-64" diff --git a/ld/emulparams/elf_i386.sh b/ld/emulparams/elf_i386.sh index 98532e5edbc..ae17bb4b3f7 100644 --- a/ld/emulparams/elf_i386.sh +++ b/ld/emulparams/elf_i386.sh @@ -6,6 +6,7 @@ source_sh ${srcdir}/emulparams/cet.sh source_sh ${srcdir}/emulparams/x86-report-relative.sh source_sh ${srcdir}/emulparams/x86-64-level.sh source_sh ${srcdir}/emulparams/static.sh +source_sh ${srcdir}/emulparams/dt-relr.sh SCRIPT_NAME=elf OUTPUT_FORMAT="elf32-i386" NO_RELA_RELOCS=yes diff --git a/ld/emulparams/elf_x86_64.sh b/ld/emulparams/elf_x86_64.sh index 48d0974711b..5f2743ed409 100644 --- a/ld/emulparams/elf_x86_64.sh +++ b/ld/emulparams/elf_x86_64.sh @@ -8,6 +8,7 @@ source_sh ${srcdir}/emulparams/x86-report-relative.sh source_sh ${srcdir}/emulparams/x86-64-level.sh source_sh ${srcdir}/emulparams/x86-64-lam.sh source_sh ${srcdir}/emulparams/static.sh +source_sh ${srcdir}/emulparams/dt-relr.sh SCRIPT_NAME=elf ELFSIZE=64 OUTPUT_FORMAT="elf64-x86-64" diff --git a/ld/emultempl/elf.em b/ld/emultempl/elf.em index 59775260b06..7a32a4cc4d4 100644 --- a/ld/emultempl/elf.em +++ b/ld/emultempl/elf.em @@ -822,7 +822,10 @@ fragment < link_info.maxpagesize) einfo (_("%F%P: common page size (0x%v) > maximum page size (0x%v)\n"), diff --git a/ld/ldlang.c b/ld/ldlang.c index 9dbc8752f87..84536a5b24d 100644 --- a/ld/ldlang.c +++ b/ld/ldlang.c @@ -7699,7 +7699,8 @@ lang_find_relro_sections (void) void lang_relax_sections (bool need_layout) { - if (RELAXATION_ENABLED) + /* NB: Also enable relaxation to layout sections for DT_RELR. */ + if (RELAXATION_ENABLED || link_info.enable_dt_relr) { /* We may need more than one relaxation pass. */ int i = link_info.relax_pass; diff --git a/ld/scripttempl/elf.sc b/ld/scripttempl/elf.sc index a9a39ad402c..f3552a4a554 100644 --- a/ld/scripttempl/elf.sc +++ b/ld/scripttempl/elf.sc @@ -10,6 +10,7 @@ # empty. # HAVE_NOINIT - Include a .noinit output section in the script. # HAVE_PERSISTENT - Include a .persistent output section in the script. +# HAVE_DT_RELR - Include a .relr.dyn output section in the script. # SMALL_DATA_CTOR - .ctors contains small data. # SMALL_DATA_DTOR - .dtors contains small data. # DATA_ADDR - if end-of-text-plus-one-page isn't right for data start @@ -520,6 +521,9 @@ emit_dyn() fi fi rm -f ldscripts/dyntmp.$$ + if test -n "${COMBRELOC}" && test -n "${HAVE_DT_RELR}"; then + echo " .relr.dyn : { *(.relr.dyn) }" + fi } test -n "${NON_ALLOC_DYN}${SEPARATE_CODE}" || emit_dyn