From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by sourceware.org (Postfix) with ESMTPS id 4F7CB3858D20 for ; Tue, 1 Mar 2022 04:22:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4F7CB3858D20 Received: by mail-pl1-x632.google.com with SMTP id h17so6907360plc.5 for ; Mon, 28 Feb 2022 20:22:48 -0800 (PST) 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=o6S1SGNTEtvExRwU6QGFX9L6cJX08wEDLMQQEt039tk=; b=DlwZ18DQt0CZ9ugQI4jwax2m18S5P4+nna/bB+nPOMCFHVF4CX94dg20G3lJbIyHPL gt4BVrVcCuWiNseLKLZ5JmiamVBCcMMyqPTrNUgJ9nKZOvQMB/hp6PKMWxnJtuKNzUcc X49NZ6kDZXxY03wLvjYoSAuFYZQbrsIL/q6nXLUPfIKWrTaFjODUt60dWfh801pDVOqV 2Lshiwck2V4Z27do9VIJlZZ9N0nVlpPHfiwyHcvk9QZ0IcHtgO3OEoz/Z7RjwpbSwf6t EY7bYNQcQeXQ2vnqDzEB7aYA6n1nbFg8BQLyU1McLd40EDX6Pxh5VcKOraYazmMdk95S cdjw== X-Gm-Message-State: AOAM533aJsG3Wqr74TluGtgcGa6MoFO0Qv801giL1EF/SmsXdej5IxKd LQmBb8a+af2AM/iV/sS5cbmEVQ== X-Google-Smtp-Source: ABdhPJwy68+mhP95KpM8mdCoHeZJE+FM87Wx8fWNUSq2TvhYcdnCXHCgDpGMJ3yV85ZPXTCVSFpAqA== X-Received: by 2002:a17:902:c443:b0:14f:f74e:ebf0 with SMTP id m3-20020a170902c44300b0014ff74eebf0mr23611792plm.171.1646108567242; Mon, 28 Feb 2022 20:22:47 -0800 (PST) Received: from google.com ([2620:15c:2ce:200:88f6:4b70:bdc0:5a68]) by smtp.gmail.com with ESMTPSA id m12-20020a17090a2c0c00b001bc4cf0107esm756435pjd.53.2022.02.28.20.22.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Feb 2022 20:22:46 -0800 (PST) Date: Mon, 28 Feb 2022 20:22:43 -0800 From: Fangrui Song To: "H.J. Lu" Cc: libc-alpha@sourceware.org, Joseph Myers Subject: Re: [PATCH v3 3/5] Add GLIBC_ABI_DT_RELR for DT_RELR support Message-ID: <20220301042243.gnaav6w57cj33egw@google.com> References: <20220207235127.1807294-1-hjl.tools@gmail.com> <20220207235127.1807294-4-hjl.tools@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20220207235127.1807294-4-hjl.tools@gmail.com> X-Spam-Status: No, score=-26.6 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, ENV_AND_HDR_SPF_MATCH, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE, URIBL_BLACK, USER_IN_DEF_DKIM_WL, USER_IN_DEF_SPF_WL 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-List-Received-Date: Tue, 01 Mar 2022 04:22:50 -0000 On 2022-02-07, H.J. Lu wrote: >The EI_ABIVERSION field of the ELF header in executables and shared >libraries can be bumped to indicate the minimum ABI requirement on the >dynamic linker. However, EI_ABIVERSION in executables isn't checked by >the Linux kernel ELF loader nor the existing dynamic linker. Executables >will crash mysteriously if the dynamic linker doesn't support the ABI >features required by the EI_ABIVERSION field. The dynamic linker should >be changed to check EI_ABIVERSION in executables. > >Add a glibc version, GLIBC_ABI_DT_RELR, to indicate DT_RELR support so >that the existing dynamic linkers will issue an error on executables with >GLIBC_ABI_DT_RELR dependency. Issue an error if there is a DT_RELR entry >without GLIBC_ABI_DT_RELR dependency nor GLIBC_PRIVATE definition. > >Support __placeholder_only_for_empty_version_map as the placeholder symbol >used only for empty version map to generate GLIBC_ABI_DT_RELR without any >symbols. >--- > elf/Makefile | 18 ++++++++++++++++-- > elf/Versions | 5 +++++ > elf/dl-version.c | 33 +++++++++++++++++++++++++++++++-- > elf/libc-abi-version.exp | 1 + > include/link.h | 6 ++++++ > scripts/abilist.awk | 2 ++ > scripts/versions.awk | 7 ++++++- > 7 files changed, 67 insertions(+), 5 deletions(-) > create mode 100644 elf/libc-abi-version.exp > >diff --git a/elf/Makefile b/elf/Makefile >index 71b08c75dd..a6515e8a21 100644 >--- a/elf/Makefile >+++ b/elf/Makefile >@@ -48,6 +48,10 @@ routines = \ > rtld_static_init \ > # routines > >+ifeq ($(have-dt-relr),yes) >+check-abi-version-libc = $(objpfx)check-abi-version-libc.out >+endif >+ > # The core dynamic linking functions are in libc for the static and > # profiled libraries. > dl-routines = \ >@@ -1106,8 +1110,8 @@ $(eval $(call include_dsosort_tests,dso-sort-tests-1.def)) > $(eval $(call include_dsosort_tests,dso-sort-tests-2.def)) > endif > >-check-abi: $(objpfx)check-abi-ld.out >-tests-special += $(objpfx)check-abi-ld.out >+check-abi: $(objpfx)check-abi-ld.out $(check-abi-version-libc) >+tests-special += $(objpfx)check-abi-ld.out $(check-abi-version-libc) > update-abi: update-abi-ld > update-all-abi: update-all-abi-ld > >@@ -2747,3 +2751,13 @@ $(objpfx)check-tst-relr-pie.out: $(objpfx)tst-relr-pie > | sed -ne '/required from libc.so/,$$ p' \ > | grep GLIBC_ABI_DT_RELR > $@; \ > $(evaluate-test) >+ >+$(objpfx)check-abi-version-libc.out: libc-abi-version.exp \ >+ $(objpfx)libc.symlist-abi-version >+ cmp $^ > $@; \ >+ $(evaluate-test) >+ >+$(objpfx)libc.symlist-abi-version: $(common-objpfx)libc.so >+ LC_ALL=C $(NM) -D $< | grep " GLIBC_ABI_" \ >+ | sed "s/^0\+/00000000/" > $@T >+ mv -f $@T $@ This checks the SHN_ABS symbol. ld.lld does not add the SHN_ABS symbol and does not plan to add it as, Perhaps just check the placeholder symbol. GNU nm before binutils 2.35 does not display @ or @@ in -D mode. >diff --git a/elf/Versions b/elf/Versions >index 8bed855d8c..a9ff278de7 100644 >--- a/elf/Versions >+++ b/elf/Versions >@@ -23,6 +23,11 @@ libc { > GLIBC_2.35 { > _dl_find_object; > } >+ GLIBC_ABI_DT_RELR { >+ # This symbol is used only for empty version map and will be removed >+ # by scripts/versions.awk. >+ __placeholder_only_for_empty_version_map; >+ } > GLIBC_PRIVATE { > # functions used in other libraries > __libc_early_init; >diff --git a/elf/dl-version.c b/elf/dl-version.c >index b47bd91727..720ec596a5 100644 >--- a/elf/dl-version.c >+++ b/elf/dl-version.c >@@ -214,12 +214,20 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) > while (1) > { > /* Match the symbol. */ >+ const char *string = strtab + aux->vna_name; > result |= match_symbol (DSO_FILENAME (map->l_name), > map->l_ns, aux->vna_hash, >- strtab + aux->vna_name, >- needed->l_real, verbose, >+ string, needed->l_real, verbose, > aux->vna_flags & VER_FLG_WEAK); > >+ if (map->l_abi_version == lav_none >+ /* 0xfd0e42: _dl_elf_hash ("GLIBC_ABI_DT_RELR"). */ >+ && aux->vna_hash == 0xfd0e42 >+ && __glibc_likely (strcmp (string, >+ "GLIBC_ABI_DT_RELR") >+ == 0)) >+ map->l_abi_version = lav_dt_relr_ref; >+ > /* Compare the version index. */ > if ((unsigned int) (aux->vna_other & 0x7fff) > ndx_high) > ndx_high = aux->vna_other & 0x7fff; >@@ -253,6 +261,16 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) > ent = (ElfW(Verdef) *) (map->l_addr + def->d_un.d_ptr); > while (1) > { >+ /* 0x0963cf85: _dl_elf_hash ("GLIBC_PRIVATE"). */ >+ if (ent->vd_hash == 0x0963cf85) >+ { >+ ElfW(Verdaux) *aux = (ElfW(Verdaux) *) ((char *) ent >+ + ent->vd_aux); >+ if (__glibc_likely (strcmp ("GLIBC_PRIVATE", >+ strtab + aux->vda_name) == 0)) >+ map->l_abi_version = lav_private_def; >+ } >+ > if ((unsigned int) (ent->vd_ndx & 0x7fff) > ndx_high) > ndx_high = ent->vd_ndx & 0x7fff; > >@@ -352,6 +370,17 @@ _dl_check_map_versions (struct link_map *map, int verbose, int trace_mode) > } > } > >+ /* Issue an error if there is a DT_RELR entry without GLIBC_ABI_DT_RELR >+ dependency nor GLIBC_PRIVATE definition. */ >+ if (map->l_info[DT_RELR] != NULL >+ && __glibc_unlikely (map->l_abi_version == lav_none)) >+ { >+ _dl_exception_create >+ (&exception, DSO_FILENAME (map->l_name), >+ N_("DT_RELR without GLIBC_ABI_DT_RELR dependency")); >+ goto call_error; >+ } >+ > return result; > } > >diff --git a/elf/libc-abi-version.exp b/elf/libc-abi-version.exp >new file mode 100644 >index 0000000000..455088dc6b >--- /dev/null >+++ b/elf/libc-abi-version.exp >@@ -0,0 +1 @@ >+00000000 A GLIBC_ABI_DT_RELR >diff --git a/include/link.h b/include/link.h >index bef2820b40..ce9e3d5214 100644 >--- a/include/link.h >+++ b/include/link.h >@@ -177,6 +177,12 @@ struct link_map > lt_library, /* Library needed by main executable. */ > lt_loaded /* Extra run-time loaded shared object. */ > } l_type:2; >+ enum /* ABI dependency of this object. */ >+ { >+ lav_none, /* No ABI dependency. */ >+ lav_dt_relr_ref, /* Need GLIBC_ABI_DT_RELR. */ >+ lav_private_def /* Define GLIBC_PRIVATE. */ >+ } l_abi_version:2; > unsigned int l_relocated:1; /* Nonzero if object's relocations done. */ > unsigned int l_init_called:1; /* Nonzero if DT_INIT function called. */ > unsigned int l_global:1; /* Nonzero if object in _dl_global_scope. */ >diff --git a/scripts/abilist.awk b/scripts/abilist.awk >index 24a34ccbed..6cc7af6ac8 100644 >--- a/scripts/abilist.awk >+++ b/scripts/abilist.awk >@@ -55,6 +55,8 @@ $2 == "g" || $2 == "w" && (NF == 7 || NF == 8) { > # caused STV_HIDDEN symbols to appear in .dynsym, though that is useless. > if (NF > 7 && $7 == ".hidden") next; > >+ if (version ~ /^GLIBC_ABI_/ && !include_abi_version) next; >+ > if (version == "GLIBC_PRIVATE" && !include_private) next; > > desc = ""; >diff --git a/scripts/versions.awk b/scripts/versions.awk >index 357ad1355e..d70b07bd1a 100644 >--- a/scripts/versions.awk >+++ b/scripts/versions.awk >@@ -185,8 +185,13 @@ END { > closeversion(oldver, veryoldver); > veryoldver = oldver; > } >- printf("%s {\n global:\n", $2) > outfile; > oldver = $2; >+ # Skip the placeholder symbol used only for empty version map. >+ if ($3 == "__placeholder_only_for_empty_version_map;") { >+ printf("%s {\n", $2) > outfile; >+ continue; >+ } >+ printf("%s {\n global:\n", $2) > outfile; > } > printf(" ") > outfile; > for (n = 3; n <= NF; ++n) { >-- >2.34.1 > Looks like a Serpent OS contributor has noticed this patch series https://github.com/llvm/llvm-project/issues/53775#issuecomment-1046361237 . I will try implementing -z pack-relative-relocs for ld.lld