From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-x229.google.com (mail-oi1-x229.google.com [IPv6:2607:f8b0:4864:20::229]) by sourceware.org (Postfix) with ESMTPS id D8FD53858C50 for ; Tue, 29 Mar 2022 16:52:47 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D8FD53858C50 Received: by mail-oi1-x229.google.com with SMTP id k10so19658352oia.0 for ; Tue, 29 Mar 2022 09:52:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=gPJMumETmx59guX+zoWp8zgrwz3t8jLuzye+MTnAneU=; b=zE9ttOJAax2rd6+kTRP83yEg991DnTTDAcey0DhXvDVB5XbNoXJbleWIpRuaeNPqSZ DauNBPUoh8VLIN8ozIpFbVMGH6gCWXbv570onARYGLZMr24lPCzE80YAsF7H07rC7yxA vNUcmLF2yzEXsS31RPGAfdLxM+c+ritR6R3EbHcIZQoEkm4qwBBDdFMjGkznAdN5UWpW 0oOeIF1ljrhnmJPVgc/qVruBNe2pmIGoFjb0TWCRb53YjiPFAayZHFAuGy53JcwdBW3U Mg3Ot5O+aI1G7jw/g5xPOF6m3zzHHMOSpJImuGsNs8V8Ceg7G3kOTNbKfqiHGHGXl8v1 1mCA== X-Gm-Message-State: AOAM530zKhs+t3vuH+u5G2dtBvGuLLlm46NKe++hH27wiezEajFgGm1u mMOxyVSqWSmIs/geOacGc6F6Eg== X-Google-Smtp-Source: ABdhPJxWS+ikRAFU5ir0tIb92JVGPDY45KlQVEND3+V4H9+R4IeyL4GaqFSNzPxUg6SU8X/AXBovfQ== X-Received: by 2002:a54:450e:0:b0:2ef:3c3f:f61d with SMTP id l14-20020a54450e000000b002ef3c3ff61dmr31250oil.99.1648572767027; Tue, 29 Mar 2022 09:52:47 -0700 (PDT) Received: from ?IPV6:2804:431:c7cb:a6c0:f1e1:dcf6:8c18:df3b? ([2804:431:c7cb:a6c0:f1e1:dcf6:8c18:df3b]) by smtp.gmail.com with ESMTPSA id bn13-20020a056808230d00b002f75bfbcf5asm2440486oib.56.2022.03.29.09.52.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 29 Mar 2022 09:52:46 -0700 (PDT) Message-ID: Date: Tue, 29 Mar 2022 13:52:44 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v6 3/5] Add GLIBC_ABI_DT_RELR for DT_RELR support Content-Language: en-US To: "H.J. Lu" , libc-alpha@sourceware.org Cc: Joseph Myers References: <20220310200329.1935466-1-hjl.tools@gmail.com> <20220310200329.1935466-4-hjl.tools@gmail.com> From: Adhemerval Zanella In-Reply-To: <20220310200329.1935466-4-hjl.tools@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-11.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, T_SCC_BODY_TEXT_LINE, URIBL_BLACK 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, 29 Mar 2022 16:52:51 -0000 On 10/03/2022 17:03, H.J. Lu via Libc-alpha 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. I think it only make sense to add the GLIBC_ABI_DT_RELR if the ABI actually supports DT_RELR, otherwise if the ABI start to support old glibcs might wrongly assumes DT_RELR and fails with undefined behavior at runtime (which this patch essentially tries to avoid). > --- > elf/Makefile | 12 ++++++++++-- > elf/Versions | 5 +++++ > elf/dl-version.c | 33 +++++++++++++++++++++++++++++++-- > include/link.h | 6 ++++++ > scripts/abilist.awk | 2 ++ > scripts/versions.awk | 7 ++++++- > 6 files changed, 60 insertions(+), 5 deletions(-) > > diff --git a/elf/Makefile b/elf/Makefile > index fd462ba315..d3118b9777 100644 > --- a/elf/Makefile > +++ b/elf/Makefile > @@ -1113,8 +1113,10 @@ $(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 \ > + $(objpfx)check-abi-version-libc.out > +tests-special += $(objpfx)check-abi-ld.out \ > + $(objpfx)check-abi-version-libc.out One line per definition. > update-abi: update-abi-ld > update-all-abi: update-all-abi-ld > > @@ -2739,3 +2741,9 @@ $(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: $(common-objpfx)libc.so > + LC_ALL=C $(READELF) -V -W $< \ > + | sed -ne '/.gnu.version_d/, /.gnu.version_r/ p' \ > + | grep GLIBC_ABI_DT_RELR > $@; \ > + $(evaluate-test) This test should be enable iff for $(have-dt-relr) == yes. > 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; > + } Same as before. Maybe use the same strategy we do for time64: add a config.h define to HAVE_DTRELR (set by configure) and use it to set the symbol if it is defined. This define would be used on dl-version.c to also enable the l_abi_version check. > 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/include/link.h b/include/link.h > index 03db14c7b0..8ec5e35cf2 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) {