From: Greg KH <gregkh@linuxfoundation.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: masahiroy@kernel.org, stable-commits@vger.kernel.org,
llvm@lists.linux.dev, linux-kbuild@vger.kernel.org
Subject: Re: Patch "um: Fix adding '-no-pie' for clang" has been added to the 5.15-stable tree
Date: Tue, 20 Feb 2024 08:51:31 +0100 [thread overview]
Message-ID: <2024022024-control-coliseum-1d40@gregkh> (raw)
In-Reply-To: <20240219192837.GD2348301@dev-arch.thelio-3990X>
On Mon, Feb 19, 2024 at 12:28:37PM -0700, Nathan Chancellor wrote:
> Hi Greg,
>
> On Mon, Feb 19, 2024 at 06:02:39PM +0100, gregkh@linuxfoundation.org wrote:
> >
> > This is a note to let you know that I've just added the patch titled
> >
> > um: Fix adding '-no-pie' for clang
> >
> > to the 5.15-stable tree which can be found at:
> > http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >
> > The filename of the patch is:
> > um-fix-adding-no-pie-for-clang.patch
> > and it can be found in the queue-5.15 subdirectory.
> >
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> >
> >
> > From 846cfbeed09b45d985079a9173cf390cc053715b Mon Sep 17 00:00:00 2001
> > From: Nathan Chancellor <nathan@kernel.org>
> > Date: Tue, 23 Jan 2024 15:59:54 -0700
> > Subject: um: Fix adding '-no-pie' for clang
> >
> > From: Nathan Chancellor <nathan@kernel.org>
> >
> > commit 846cfbeed09b45d985079a9173cf390cc053715b upstream.
> >
> > The kernel builds with -fno-PIE, so commit 883354afbc10 ("um: link
> > vmlinux with -no-pie") added the compiler linker flag '-no-pie' via
> > cc-option because '-no-pie' was only supported in GCC 6.1.0 and newer.
> >
> > While this works for GCC, this does not work for clang because cc-option
> > uses '-c', which stops the pipeline right before linking, so '-no-pie'
> > is unconsumed and clang warns, causing cc-option to fail just as it
> > would if the option was entirely unsupported:
> >
> > $ clang -Werror -no-pie -c -o /dev/null -x c /dev/null
> > clang-16: error: argument unused during compilation: '-no-pie' [-Werror,-Wunused-command-line-argument]
> >
> > A recent version of clang exposes this because it generates a relocation
> > under '-mcmodel=large' that is not supported in PIE mode:
> >
> > /usr/sbin/ld: init/main.o: relocation R_X86_64_32 against symbol `saved_command_line' can not be used when making a PIE object; recompile with -fPIE
> > /usr/sbin/ld: failed to set dynamic section sizes: bad value
> > clang: error: linker command failed with exit code 1 (use -v to see invocation)
> >
> > Remove the cc-option check altogether. It is wasteful to invoke the
> > compiler to check for '-no-pie' because only one supported compiler
> > version does not support it, GCC 5.x (as it is supported with the
> > minimum version of clang and GCC 6.1.0+). Use a combination of the
> > gcc-min-version macro and CONFIG_CC_IS_CLANG to unconditionally add
> > '-no-pie' with CONFIG_LD_SCRIPT_DYN=y, so that it is enabled with all
> > compilers that support this. Furthermore, using gcc-min-version can help
> > turn this back into
> >
> > LINK-$(CONFIG_LD_SCRIPT_DYN) += -no-pie
> >
> > when the minimum version of GCC is bumped past 6.1.0.
> >
> > Cc: stable@vger.kernel.org
> > Closes: https://github.com/ClangBuiltLinux/linux/issues/1982
> > Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > ---
> > arch/um/Makefile | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > --- a/arch/um/Makefile
> > +++ b/arch/um/Makefile
> > @@ -118,7 +118,9 @@ archprepare:
> > $(Q)$(MAKE) $(build)=$(HOST_DIR)/um include/generated/user_constants.h
> >
> > LINK-$(CONFIG_LD_SCRIPT_STATIC) += -static
> > -LINK-$(CONFIG_LD_SCRIPT_DYN) += $(call cc-option, -no-pie)
> > +ifdef CONFIG_LD_SCRIPT_DYN
> > +LINK-$(call gcc-min-version, 60100)$(CONFIG_CC_IS_CLANG) += -no-pie
>
> 5.15 does not have support for gcc-min-version, so I think this just
> breaks ARCH=um for GCC. I do not think this patch matters much in 5.15
> and earlier, we only test ARCH=um with Linux 6.1 and newer, so it can be
> dropped.
Thanks, now dropped.
greg k-h
prev parent reply other threads:[~2024-02-20 7:51 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <2024021939-dullness-calculate-a293@gregkh>
2024-02-19 19:28 ` Patch "um: Fix adding '-no-pie' for clang" has been added to the 5.15-stable tree Nathan Chancellor
2024-02-20 7:51 ` Greg KH [this message]
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