From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-x102e.google.com (mail-pj1-x102e.google.com [IPv6:2607:f8b0:4864:20::102e]) by sourceware.org (Postfix) with ESMTPS id E1082385840C for ; Tue, 29 Mar 2022 22:30:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E1082385840C Received: by mail-pj1-x102e.google.com with SMTP id o3-20020a17090a3d4300b001c6bc749227so4379639pjf.1 for ; Tue, 29 Mar 2022 15:30:25 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=87Qi09Fegfmgnqv+0jNVrJYlBHfr+lnEdAVVQSww9SQ=; b=xBJ8v9HBXK4wkODvEP19tRqiyfEn9cyVHsKuusU1d/hXUlMa+aDRcwIx9oM3uGfe3j NxnBxgTwubYpoeF7TW6zaccdqVJ/e4u/rd7vbbv5bhi1g3KynM5Km9gGPineqFR2/yWO EeDZAnMJ2yorHgg6iW0yBhkLr9j6K6+6eAzBvZsdHzB55pal8W/WDSHR56yjNt94wMRh 3ZIaQwtGqqTBhoSH+n1BLPEdHjZyHej6bnophYwH28oF1TkDh09YPRMXnPbXhTUUO7Ih 9ksXyc+jjtnCFK+qFA+6tfhjaz0pj28YmwspclMb13qLt4DBPkekwat23/KnS8z2Y/ft Qdyg== X-Gm-Message-State: AOAM533Zf+kxXaIb+uKAjelt2iEprlVkQyv8TFYXkeWGOguNVaenwEAL o4fHepq/TR3I0Qpjkj7zSDk5FYmEbdT3xOep4dmDviVi3pU= X-Google-Smtp-Source: ABdhPJzxOIKDNgl/oGjKesBA9UnzpE1u4oNC2zzHJx6AIBij7dYZxLrvdIjCPm3FA8MOaXn8nAsMz8lG+vum2TC0P+c= X-Received: by 2002:a17:902:f690:b0:154:2ceb:f18a with SMTP id l16-20020a170902f69000b001542cebf18amr32186035plg.4.1648593024827; Tue, 29 Mar 2022 15:30:24 -0700 (PDT) MIME-Version: 1.0 References: <20220310200329.1935466-1-hjl.tools@gmail.com> <20220310200329.1935466-4-hjl.tools@gmail.com> In-Reply-To: From: "H.J. Lu" Date: Tue, 29 Mar 2022 15:29:48 -0700 Message-ID: Subject: Re: [PATCH v6 3/5] Add GLIBC_ABI_DT_RELR for DT_RELR support To: Adhemerval Zanella Cc: GNU C Library , Joseph Myers Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3025.7 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, GIT_PATCH_0, KAM_SHORT, 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 22:30:28 -0000 On Tue, Mar 29, 2022 at 9:52 AM Adhemerval Zanella wrote: > > > > 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). The DT_RELR set enables DT_RELR in glibc for all targets. > > --- > > 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. Fixed in v7. > > 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. This test checks if libc.so has the GLIBC_ABI_DT_RELR version definition. Since it doesn't require a new linker, there is no need to check $(have-dt-relr). This test passes with an old linker. > > 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) { -- H.J.