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 602C93858D20 for ; Tue, 1 Mar 2022 15:11:35 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 602C93858D20 Received: by mail-pj1-x102e.google.com with SMTP id gb21so14308809pjb.5 for ; Tue, 01 Mar 2022 07:11:35 -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=NQr3j4U0S1W4GOIWQeNPegXwlC0wkPZwVw9KkwAQYtk=; b=BEHDvXsaRPGDtKNRFVcc/xq5DuLgEDyoflfnsav3AaKOFa/zCA5T5+rdwui+IJ+L3Z GSl2wmgEhG76lVmIIws8XPcJ5g+olufVEzcTcGeYA8I+14L1xssxE6Ocyftb5dzpTm5B zHC7V+ns8XH/12Clj7pA7JVBHUvoVq7vaRoq/PVEwZDUQO1ViInTdVkYsCSTjgSClHqa co64wvphoBSHm+pBimUmGh/AP+TSFt8BnVlqScDDAPNgGnOWekw8zNW3z+pcTRFy017X r01pVgZDjQbCxJRSAP700HqwLGhQvB0+h7OfO13QXxOLzJNod2KYhST0H9sA2JVouUCa u5Bg== X-Gm-Message-State: AOAM532wNdn9ztAsNbMw8iG5VpeZl1E71nJA5N790EEv94zZ7GZHGjbH ezqBcOhiFHMT6z/WbANrboKehxR3irRf6p6YQVeuS+KtY40= X-Google-Smtp-Source: ABdhPJyP+gp0HBOCw5iEviiG+fJSXaWJRk+3HMGoxgrO+j3/X5NaVyBL892QtBjErVXyu/qOSEdqv4boSokIrLIE55A= X-Received: by 2002:a17:90a:20a:b0:1be:e850:1a37 with SMTP id c10-20020a17090a020a00b001bee8501a37mr1730500pjc.28.1646147494429; Tue, 01 Mar 2022 07:11:34 -0800 (PST) MIME-Version: 1.0 References: <20220207235127.1807294-1-hjl.tools@gmail.com> <20220207235127.1807294-4-hjl.tools@gmail.com> <20220301042243.gnaav6w57cj33egw@google.com> In-Reply-To: From: "H.J. Lu" Date: Tue, 1 Mar 2022 07:10:58 -0800 Message-ID: Subject: Re: [PATCH v3 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=-3026.2 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 15:11:37 -0000 On Tue, Mar 1, 2022 at 6:42 AM H.J. Lu wrote: > > On Mon, Feb 28, 2022 at 8:22 PM Fangrui Song wrote: > > > > 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. > > Does lld support version dependency without a symbol? > I want to avoid adding the unused symbols to libc.so. > > > GNU nm before binutils 2.35 does not display @ or @@ in -D mode. > > I will check it. check-abi-version-libc.out doesn't depend on DT_RELR support in binutils. I will update it. > > >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 > > > > -- > H.J. -- H.J.