From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-x442.google.com ([2a00:1450:4864:20::442]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jvnlN-0005qY-0z for linux-um@lists.infradead.org; Wed, 15 Jul 2020 20:12:21 +0000 Received: by mail-wr1-x442.google.com with SMTP id a6so4203065wrm.4 for ; Wed, 15 Jul 2020 13:12:19 -0700 (PDT) From: Ignat Korchagin Subject: [PATCH v3 1/3] um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS Date: Wed, 15 Jul 2020 21:11:57 +0100 Message-Id: <20200715201159.54166-2-ignat@cloudflare.com> In-Reply-To: <20200715201159.54166-1-ignat@cloudflare.com> References: <20200715201159.54166-1-ignat@cloudflare.com> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org To: jdike@addtoit.com, richard@nod.at, anton.ivanov@cambridgegreys.com, brendanhiggins@google.com, masahiroy@kernel.org, linux-um@lists.infradead.org, linux-kernel@vger.kernel.org Cc: kernel-team@cloudflare.com, Ignat Korchagin For statically linked UML build it is important to take into account the standard C-library implementation. Some implementations, notably glibc have caveats: even when linked statically, the final program might require some runtime dependencies, if certain functions are used within the code. Consider the following program: int main(void) { getpwent(); return 0; } Compiling this program and linking statically with glibc produces the following warning from the linker: /usr/sbin/ld: /tmp/ccuthw1o.o: in function `main': test.c:(.text+0x5): warning: Using 'getpwent' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking We will use the flag to detect such C-library implementation build time and possibly disable static linking for UML to avoid producing a binary with unexpected behaviour and dependencies. Signed-off-by: Ignat Korchagin Reviewed-by: Brendan Higgins Tested-by: Brendan Higgins --- init/Kconfig | 6 ++++++ scripts/cc-can-link.sh | 5 +++-- 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/init/Kconfig b/init/Kconfig index 0498af567f70..0a1ec56c9f33 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -57,6 +57,12 @@ config CC_CAN_LINK_STATIC default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static) +config CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS + bool + depends on UML && CC_CAN_LINK_STATIC + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static -Xlinker --fatal-warnings) if 64BIT + default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static -Xlinker --fatal-warnings) + config CC_HAS_ASM_GOTO def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC)) diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh index 6efcead31989..e5011a46103e 100755 --- a/scripts/cc-can-link.sh +++ b/scripts/cc-can-link.sh @@ -2,10 +2,11 @@ # SPDX-License-Identifier: GPL-2.0 cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1 -#include +#include +#include int main(void) { - printf(""); + getpwent(); return 0; } END -- 2.20.1 _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um