From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg1-x52b.google.com (mail-pg1-x52b.google.com [IPv6:2607:f8b0:4864:20::52b]) by sourceware.org (Postfix) with ESMTPS id 450353858D20 for ; Tue, 1 Mar 2022 14:43:25 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 450353858D20 Received: by mail-pg1-x52b.google.com with SMTP id c1so14549605pgk.11 for ; Tue, 01 Mar 2022 06:43:25 -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=mTRntzzrGvIhfB1oBq93x5nF4FMqi8DppmIjIaouhSU=; b=mcMuLjsQeGk2+akCP6LdEyK73iWJskOtMaL1TVaw7pmMcvUUI6FiHO542muoYMnyz4 fs0D7G19PF6WnCKnSclWBJkFDSIM5nw+mrnHvmHBDqQYUyLOIRF2PFIN6seN1awKlj0o UMEv1J+jtiwHrBPjc6rVARhpLi/gXiAKvIJtMR3ohdhqOZFiP9z3qZ/xPN5gNtDv9+pn VXaHFbR8WVfA+PSlJMcYL9SuuA77Tz7LKPoJhgzrNhJBc+4BI0/VI4AK+8lQYJCS0FoS StN0hk7akX6L+j95xgBejgplnO4H5W4nJfLfDFFxAi7xwdLmhzi2e5QXrL5DliK1pjwL s6Ow== X-Gm-Message-State: AOAM533xvsU2pX3iG3hYegK77Ul40CT/aAR9HbJwHKqmtzA91vHzUl6+ Ad1priRhPxRm2L0YRb4h1L5+0gBzZ0x94m4dojhcfOQe X-Google-Smtp-Source: ABdhPJxJ3olOTc08Ym3Gtj4DHGG+SfEQoa1e8TYKfYz/MMo9CqjRVpwfRSOEt2/rcUBW4IGRvLszT3GeC3pqkiTxC+M= X-Received: by 2002:aa7:8d54:0:b0:4e0:bd6:cfb9 with SMTP id s20-20020aa78d54000000b004e00bd6cfb9mr27967823pfe.60.1646145804179; Tue, 01 Mar 2022 06:43:24 -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: <20220301042243.gnaav6w57cj33egw@google.com> From: "H.J. Lu" Date: Tue, 1 Mar 2022 06:42:48 -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=-3026.0 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 14:43:27 -0000 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. > >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.