From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-x235.google.com (mail-oi1-x235.google.com [IPv6:2607:f8b0:4864:20::235]) by sourceware.org (Postfix) with ESMTPS id 2DDD13858D39 for ; Tue, 1 Mar 2022 22:34:08 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 2DDD13858D39 Received: by mail-oi1-x235.google.com with SMTP id ay7so124658oib.8 for ; Tue, 01 Mar 2022 14:34:08 -0800 (PST) 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=EwyDhz6tk2BFf7klM9Of68mazfjeW1GYVxZj70zMaPM=; b=P0UnWnYUeQGrmbYk99Kx5vEPrKkWjfi5I/ifkeb3y/NzQ/JuLGmKJ5W5jBr1VcQE7i h9Ba9hhaKHGMSBCrhintCVOY+ClCT8ySvYOFtBErznDBJ68zVEr9Vm0yGP1pRlw0ucSP VVoiTgcASr1+1Tpk1PzlPfvRzmgMj9K+x5b8FwUm67r+rvFvO7iA6+3sXqTTsIt0wNIM kStrfQmuy9KEDeSVazX6lwx6yy/QK3164nfcQa6UPXnsXp78JKwqJ+G1dOIP8u6wcyQx m2a7Kr8M8eQe4bbYl533Hw6rWyCING0jQUYfX0FtYM0HcF1hpPnqIrdn1Rb1/tipCJmg LDoA== X-Gm-Message-State: AOAM533+odrR1iqEvrnYafwl22fLEgwaImOwmLwpXeNeqYtPoNUGFuEi z8zh1SM/3zOfBsswtbSIwB2dahPzXmNfXCaD6lRAF6+YuLI= X-Google-Smtp-Source: ABdhPJyHwR2QSpcQxHWG78sQ27MCYVVQ3f7nvn+otl6rLC8AEMLAP0PCpPUFDLqjjYCCj0hv3Is0I6dqfwW/Vj7kFzU= X-Received: by 2002:a54:4f1c:0:b0:2d0:6df2:808e with SMTP id e28-20020a544f1c000000b002d06df2808emr17023879oiy.67.1646174047345; Tue, 01 Mar 2022 14:34:07 -0800 (PST) MIME-Version: 1.0 References: <20220301161706.185216-1-hjl.tools@gmail.com> <20220301161706.185216-4-hjl.tools@gmail.com> <20220301193145.izbrur2kma6fc6to@google.com> In-Reply-To: <20220301193145.izbrur2kma6fc6to@google.com> From: "H.J. Lu" Date: Tue, 1 Mar 2022 14:33:31 -0800 Message-ID: Subject: Re: [PATCH v4 3/5] Add GLIBC_ABI_DT_RELR for DT_RELR support To: Fangrui Song Cc: GNU C Library , Joseph Myers Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3026.4 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, 01 Mar 2022 22:34:10 -0000 On Tue, Mar 1, 2022 at 11:31 AM Fangrui Song wrote: > > On 2022-03-01, 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 | 16 ++++++++++++++-- > > 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, 65 insertions(+), 5 deletions(-) > > create mode 100644 elf/libc-abi-version.exp > > > >diff --git a/elf/Makefile b/elf/Makefile > >index fd462ba315..f533d377fd 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 > > update-abi: update-abi-ld > > update-all-abi: update-all-abi-ld > > > >@@ -2739,3 +2741,13 @@ $(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 $(OBJDUMP) --dynamic-syms $< | grep " GLIBC_ABI_" \ > >+ | sed "s/0\+/00000000/g;s/[ \t]\+/ /g" > $@T > >+ mv -f $@T $@ > > As just mentioned on https://sourceware.org/pipermail/libc-alpha/2022-March/136764.html , > perhaps use something like $(READELF) -V $< | grep GLIBC_ABI_DT_RELR > > > % nm -D a/glibc > U stat@GLIBC_2.33 > % objdump --dynamic-syms a/glibc > > a/glibc: file format elf64-x86-64 > > DYNAMIC SYMBOL TABLE: > 0000000000000000 D *UND* 0000000000000000 (GLIBC_2.33) stat It is easier to run cmp on "objdump --dynamic-syms" outputs on different targets. > > % readelf -V a/glibc > > Version symbols section '.gnu.version' contains 2 entries: > Addr: 0x0000000000000230 Offset: 0x000230 Link: 1 (.dynsym) > 000: 0 (*local*) 2 (GLIBC_2.33) > > Version needs section '.gnu.version_r' contains 1 entry: > Addr: 0x0000000000000234 Offset: 0x000234 Link: 6 (.dynstr) > 000000: Version: 1 File: libc.so.6 Cnt: 2 > 0x0010: Name: GLIBC_2.33 Flags: none Version: 2 > 0x0020: Name: GLIBC_ABI_DT_RELR Flags: none Version: 3 > > > Is there a static pie test? A static pie has DT_RELR but does not have verneed. If linker supports DT_RELR, static PIE programs and tests will have DT_RELR. They will be tested. > >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..ff8506b3ba > >--- /dev/null > >+++ b/elf/libc-abi-version.exp > >@@ -0,0 +1 @@ > >+00000000 g DO *ABS* 00000000 GLIBC_ABI_DT_RELR GLIBC_ABI_DT_RELR > >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) { > >-- > >2.35.1 > > -- H.J.