From: Ignat Korchagin <ignat@cloudflare.com>
To: jdike@addtoit.com, richard@nod.at,
anton.ivanov@cambridgegreys.com, brendanhiggins@google.com,
linux-um@lists.infradead.org, linux-kernel@vger.kernel.org
Cc: Ignat Korchagin <ignat@cloudflare.com>, kernel-team@cloudflare.com
Subject: [PATCH v2 1/3] um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS
Date: Sat, 4 Jul 2020 09:52:11 +0100 [thread overview]
Message-ID: <20200704085213.444645-2-ignat@cloudflare.com> (raw)
In-Reply-To: <20200704085213.444645-1-ignat@cloudflare.com>
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 <ignat@cloudflare.com>
---
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 a46aa8f3174d..717a3ada765e 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) -static $(m64-flag)) if 64BIT
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static $(m32-flag))
+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) -static -Xlinker --fatal-warnings $(m64-flag)) if 64BIT
+ default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) -static -Xlinker --fatal-warnings $(m32-flag))
+
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 <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
int main(void)
{
- printf("");
+ getpwent();
return 0;
}
END
--
2.20.1
next prev parent reply other threads:[~2020-07-04 8:52 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-04 8:52 [PATCH v2 0/3] um: allow static linking for non-glibc libc implementations Ignat Korchagin
2020-07-04 8:52 ` Ignat Korchagin [this message]
2020-07-15 8:38 ` [PATCH v2 1/3] um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS Brendan Higgins
2020-07-04 8:52 ` [PATCH v2 2/3] um: some fixes to build UML with musl Ignat Korchagin
2020-07-14 8:40 ` Anton Ivanov
2020-07-14 10:23 ` Ignat Korchagin
2020-07-14 10:43 ` Anton Ivanov
2020-07-14 16:02 ` Johannes Berg
2020-07-15 8:47 ` Brendan Higgins
2020-07-04 8:52 ` [PATCH v2 3/3] um: allow static linking for non-glibc implementations Ignat Korchagin
2020-07-15 8:44 ` Brendan Higgins
2020-07-15 9:30 ` Ignat Korchagin
2020-07-15 8:36 ` [PATCH v2 0/3] um: allow static linking for non-glibc libc implementations Brendan Higgins
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