From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <3tBxlYAcKCos1p7z6pDv33v0t.r310xqr-p04wp7396rtBp6t.36v@flex--maskray.bounces.google.com> Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by sourceware.org (Postfix) with ESMTPS id CC0F33858C27 for ; Thu, 1 Apr 2021 01:07:00 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org CC0F33858C27 Received: by mail-yb1-xb4a.google.com with SMTP id i6so4161260ybk.2 for ; Wed, 31 Mar 2021 18:07:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc:content-transfer-encoding; bh=3BQ+AmfTqGx/XgZd5DDqy0yY1uaB6w3a7UBXMoHg2Js=; b=XQTBebuuoDJyAJaBOjVEGICkfWJFLOfTjl2SAobv/szE9URv+/r3sGU0xIKyHW24Th 3Pf0v2rTBwGVGlLw3YCcqYtvHluLXPShZXf6gFod1ntBhP568oSg2sUBJxmlmaiTEymE 5AOgueaLiiPJYlJQNVT5Y/3VXTI+wbjMPZ4XyUnkOBqQRj9pFGhAOuVZhJvrXvEVrWo5 CsyBG5+/vP1LGbVQWIDDNTC6YFIs4RLCCtcSB5cpmPrs9uOdFQCRByRe7iX8QklChb6k hywyKB0RwgpN0du51Bj8iKCxO717j753VoOlgQ/y0k43BKIbRYCPRJ0KkfSwGlr/YikQ ZtiQ== X-Gm-Message-State: AOAM532/FeihCoPJ/WlcbnxQHCIVaJ69pSePuwMw3LQ69EyyHygcKsDn dkoolwa9SB3surirrsiHQjw63AL1vp0VdcttwbuHzRLXDil2NO+kG7PCjT9pcZ4LKHhcAiR8gBg Z076GG7Lcc165r/tcjb9dplOn5n7PDVMY0b47eOoObhXlW0ClnFv+sHoNz3hxFFegD5ln X-Google-Smtp-Source: ABdhPJzNHZL2djpKL+op9GutPQ/+qkjCU4QNoy8JVYJ+Rj9P5ECsCAau55UXM1MEct+LnwqAhW300PRwfEh2 X-Received: from maskray1.svl.corp.google.com ([2620:15c:2ce:0:9106:8d2e:6ec7:9708]) (user=maskray job=sendgmr) by 2002:a5b:341:: with SMTP id q1mr8514615ybp.386.1617239220278; Wed, 31 Mar 2021 18:07:00 -0700 (PDT) Date: Wed, 31 Mar 2021 18:06:57 -0700 In-Reply-To: Message-Id: <20210401010657.3474569-1-maskray@google.com> Mime-Version: 1.0 References: X-Mailer: git-send-email 2.31.0.291.g576ba9dcdaf-goog Subject: [PATCH v5] Set the retain attribute on _elf_set_element if CC supports [BZ #27492] From: Fangrui Song To: libc-alpha@sourceware.org, Florian Weimer , "H . J . Lu " Cc: Fangrui Song Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-19.6 required=5.0 tests=BAYES_00, DKIMWL_WL_MED, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP, USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Thu, 01 Apr 2021 01:07:02 -0000 So that text_set_element/data_set_element/bss_set_element defined variables will be retained by the linker. Note: 'used' and 'retain' are orthogonal: 'used' makes sure the variable will not be optimized out; 'retain' prevents section garbage collection if the linker support SHF_GNU_RETAIN. GNU ld 2.37 and LLD 13 will support -z start-stop-gc which allow C identifier name sections to be GCed even if there are live __start_/__stop_ references. Without the change, there are some static linking problems, e.g. _IO_cleanup (libio/genops.c) may be discarded by ld --gc-sections, so stdout is not flushed on exit. Note: GCC may warning =E2=80=98retain=E2=80=99 attribute ignored while __ha= s_attribute(retain) is 1 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D99587). --- Changes in v1 -> v2: * Define attribute_used_retain_section Changes in v2 -> v3: * Use attribute_used_retain instead attribute_used_retain_section Changes in v3 -> v4: * Add LIBC_LINKER_FEATURE detection for -z start-stop-gc and add tst-cleanu= p* tests Changes in v4 -> v5: * Enable -z start-stop-gc tests if both retain and -z start-stop-gc are sup= ported * Rename *gcc_retain* to *gnu_retain* --- config.h.in | 3 +++ configure | 59 ++++++++++++++++++++++++++++++++++++++++++ configure.ac | 21 +++++++++++++++ include/libc-symbols.h | 14 +++++++--- libio/Makefile | 32 +++++++++++++++++++++++ libio/tst-cleanup.c | 33 +++++++++++++++++++++++ libio/tst-cleanup.exp | 1 + 7 files changed, 159 insertions(+), 4 deletions(-) create mode 100644 libio/tst-cleanup.c create mode 100644 libio/tst-cleanup.exp diff --git a/config.h.in b/config.h.in index ca1547ae67..96a08c7757 100644 --- a/config.h.in +++ b/config.h.in @@ -187,6 +187,9 @@ /* Define if gcc supports attribute ifunc. */ #undef HAVE_GCC_IFUNC =20 +/* Define if CC supports attribute retain. */ +#undef HAVE_GNU_RETAIN + /* Define if the linker defines __ehdr_start. */ #undef HAVE_EHDR_START =20 diff --git a/configure b/configure index fcf43bf7de..e64b7f8efe 100755 --- a/configure +++ b/configure @@ -4105,6 +4105,31 @@ fi $as_echo "$libc_cv_textrel_ifunc" >&6; } =20 =20 +# Check if CC supports attribute retain as it is used in attribute_used_re= tain macro. +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for GNU attribute retain= support" >&5 +$as_echo_n "checking for GNU attribute retain support... " >&6; } +if ${libc_cv_gnu_retain+:} false; then : + $as_echo_n "(cached) " >&6 +else + cat > conftest.c <&5 \ + 2>&5 ; then + libc_cv_gnu_retain=3Dyes +fi +rm -f conftest* +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gnu_retain" >&5 +$as_echo "$libc_cv_gnu_retain" >&6; } +if test $libc_cv_gnu_retain =3D yes; then + $as_echo "#define HAVE_GNU_RETAIN 1" >>confdefs.h + +fi +config_vars=3D"$config_vars +have-gnu-retain =3D $libc_cv_gnu_retain" + # Check if gcc warns about alias for function with incompatible types. { $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about = alias for function with incompatible types" >&5 $as_echo_n "checking if compiler warns about alias for function with incom= patible types... " >&6; } @@ -5871,6 +5896,40 @@ fi $as_echo "$libc_linker_feature" >&6; } =20 =20 +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports= -z start-stop-gc" >&5 +$as_echo_n "checking for linker that supports -z start-stop-gc... " >&6; } +libc_linker_feature=3Dno +if test x"$gnu_ld" =3D x"yes"; then + libc_linker_check=3D`$LD -v --help 2>/dev/null | grep "\-z start-stop-gc= "` + if test -n "$libc_linker_check"; then + cat > conftest.c <&5' + { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5 + (eval $ac_try) 2>&5 + ac_status=3D$? + $as_echo "$as_me:${as_lineno-$LINENO}: \$? =3D $ac_status" >&5 + test $ac_status =3D 0; }; } + then + libc_linker_feature=3Dyes + fi + rm -f conftest* + fi +fi +if test $libc_linker_feature =3D yes; then + libc_cv_z_start_stop_gc=3Dyes +else + libc_cv_z_start_stop_gc=3Dno +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_linker_feature" >&5 +$as_echo "$libc_linker_feature" >&6; } +config_vars=3D"$config_vars +have-z-start-stop-gc =3D $libc_cv_z_start_stop_gc" + { $as_echo "$as_me:${as_lineno-$LINENO}: checking for linker that supports= --no-dynamic-linker" >&5 $as_echo_n "checking for linker that supports --no-dynamic-linker... " >&6= ; } libc_linker_feature=3Dno diff --git a/configure.ac b/configure.ac index fce967f2c2..cc47e56e82 100644 --- a/configure.ac +++ b/configure.ac @@ -707,6 +707,23 @@ fi rm -f conftest*]) AC_SUBST(libc_cv_textrel_ifunc) =20 +# Check if CC supports attribute retain as it is used in attribute_used_re= tain macro. +AC_CACHE_CHECK([for GNU attribute retain support], + libc_cv_gnu_retain, [dnl +cat > conftest.c <&AS_MESSAGE_LOG_FD \ + 2>&AS_MESSAGE_LOG_FD ; then + libc_cv_gnu_retain=3Dyes +fi +rm -f conftest*]) +if test $libc_cv_gnu_retain =3D yes; then + AC_DEFINE(HAVE_GNU_RETAIN) +fi +LIBC_CONFIG_VAR([have-gnu-retain], [$libc_cv_gnu_retain]) + # Check if gcc warns about alias for function with incompatible types. AC_CACHE_CHECK([if compiler warns about alias for function with incompatib= le types], libc_cv_gcc_incompatible_alias, [dnl @@ -1317,6 +1334,10 @@ LIBC_LINKER_FEATURE([-z execstack], [-Wl,-z,execstac= k], [libc_cv_z_execstack=3Dyes], [libc_cv_z_execstack=3Dno]) AC_SUBST(libc_cv_z_execstack) =20 +LIBC_LINKER_FEATURE([-z start-stop-gc], [-Wl,-z,start-stop-gc], + [libc_cv_z_start_stop_gc=3Dyes], [libc_cv_z_start_stop_gc=3Dno]) +LIBC_CONFIG_VAR([have-z-start-stop-gc], [$libc_cv_z_start_stop_gc]) + LIBC_LINKER_FEATURE([--no-dynamic-linker], [-Wl,--no-dynamic-linker], [libc_cv_no_dynamic_linker=3Dyes], diff --git a/include/libc-symbols.h b/include/libc-symbols.h index 546fc26a7b..127ea656c2 100644 --- a/include/libc-symbols.h +++ b/include/libc-symbols.h @@ -352,6 +352,12 @@ for linking") =0C */ =20 +#ifdef HAVE_GNU_RETAIN +# define attribute_used_retain __attribute__ ((__used__, __retain__)) +#else +# define attribute_used_retain __attribute__ ((__used__)) +#endif + /* Symbol set support macros. */ =20 /* Make SYMBOL, which is in the text segment, an element of SET. */ @@ -367,12 +373,12 @@ for linking") /* When building a shared library, make the set section writable, because it will need to be relocated at run time anyway. */ # define _elf_set_element(set, symbol) \ - static const void *__elf_set_##set##_element_##symbol##__ \ - __attribute__ ((used, section (#set))) =3D &(symbol) + static const void *__elf_set_##set##_element_##symbol##__ \ + attribute_used_retain __attribute__ ((section (#set))) =3D &(symbol) #else # define _elf_set_element(set, symbol) \ - static const void *const __elf_set_##set##_element_##symbol##__ \ - __attribute__ ((used, section (#set))) =3D &(symbol) + static const void *const __elf_set_##set##_element_##symbol##__ \ + attribute_used_retain __attribute__ ((section (#set))) =3D &(symbol) #endif =20 /* Define SET as a symbol set. This may be required (it is in a.out) to diff --git a/libio/Makefile b/libio/Makefile index 12ce41038f..c9c232ebc2 100644 --- a/libio/Makefile +++ b/libio/Makefile @@ -195,6 +195,20 @@ ifeq (yes,$(build-shared)) tests-special +=3D $(objpfx)tst-fopenloc-cmp.out $(objpfx)tst-fopenloc-mem= .out \ $(objpfx)tst-bz24228-mem.out endif + +tests +=3D tst-cleanup-default +tests-static +=3D tst-cleanup-default +tests-special +=3D $(objpfx)tst-cleanup-default-cmp.out +LDFLAGS-tst-cleanup-default =3D -Wl,--gc-sections + +ifeq ($(have-gnu-retain)$(have-z-start-stop-gc),yesyes) +tests +=3D tst-cleanup-start-stop-gc tst-cleanup-nostart-stop-gc +tests-static +=3D tst-cleanup-start-stop-gc tst-cleanup-nostart-stop-gc +tests-special +=3D $(objpfx)tst-cleanup-start-stop-gc-cmp.out \ + $(objpfx)tst-cleanup-nostart-stop-gc-cmp.out +LDFLAGS-tst-cleanup-start-stop-gc =3D -Wl,--gc-sections,-z,start-stop-gc +LDFLAGS-tst-cleanup-nostart-stop-gc =3D -Wl,--gc-sections,-z,nostart-stop-= gc +endif endif =20 include ../Rules @@ -224,6 +238,24 @@ $(objpfx)tst_wprintf2.out: $(gen-locales) $(objpfx)tst-wfile-sync.out: $(gen-locales) endif =20 +$(objpfx)tst-cleanup-default-cmp.out: tst-cleanup.exp $(objpfx)tst-cleanup= -default.out + cmp $^ > $@; \ + $(evaluate-test) +$(objpfx)tst-cleanup-default.o: tst-cleanup.c + $(compile.c) -o $@ + +$(objpfx)tst-cleanup-start-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst-c= leanup-start-stop-gc.out + cmp $^ > $@; \ + $(evaluate-test) +$(objpfx)tst-cleanup-start-stop-gc.o: tst-cleanup.c + $(compile.c) -o $@ + +$(objpfx)tst-cleanup-nostart-stop-gc-cmp.out: tst-cleanup.exp $(objpfx)tst= -cleanup-nostart-stop-gc.out + cmp $^ > $@; \ + $(evaluate-test) +$(objpfx)tst-cleanup-nostart-stop-gc.o: tst-cleanup.c + $(compile.c) -o $@ + $(objpfx)test-freopen.out: test-freopen.sh $(objpfx)test-freopen $(SHELL) $< $(common-objpfx) '$(test-program-prefix)' \ $(common-objpfx)libio/; \ diff --git a/libio/tst-cleanup.c b/libio/tst-cleanup.c new file mode 100644 index 0000000000..7f0a34a91e --- /dev/null +++ b/libio/tst-cleanup.c @@ -0,0 +1,33 @@ +/* Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +/* Test that stdout is flushed after atexit callbacks were run. */ + +#include +#include + +void +hook (void) +{ + puts ("hello"); +} + +int +main (void) +{ + atexit (hook); +} diff --git a/libio/tst-cleanup.exp b/libio/tst-cleanup.exp new file mode 100644 index 0000000000..ce01362503 --- /dev/null +++ b/libio/tst-cleanup.exp @@ -0,0 +1 @@ +hello --=20 2.31.0.291.g576ba9dcdaf-goog