linux-kernel - Re: [PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector

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Date:   Wed, 1 Jul 2020 08:01:50 +0200
From:   Marco Elver <elver@...gle.com>
To:     Masahiro Yamada <masahiroy@...nel.org>
Cc:     linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        x86@...nel.org, linux-efi@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, paulmck@...nel.org
Subject: Re: [PATCH 1/2] kbuild: remove cc-option test of -fno-stack-protector

On Sat, Jun 27, 2020 at 03:59AM +0900, Masahiro Yamada wrote:
> Some Makefiles already pass -fno-stack-protector unconditionally.
> For example, arch/arm64/kernel/vdso/Makefile, arch/x86/xen/Makefile.
> No problem report so far about hard-coding this option. So, we can
> assume all supported compilers know -fno-stack-protector.
> 
> GCC 4.8 and Clang support this option (https://godbolt.org/z/_HDGzN)
> 
> Get rid of cc-option from -fno-stack-protector.
> 
> Remove CONFIG_CC_HAS_STACKPROTECTOR_NONE, which should always be 'y'.
> 
> Note:
> arch/mips/vdso/Makefile adds -fno-stack-protector twice, first
> unconditionally, and second conditionally. I removed the second one.
> 
> Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
> ---
> 
>  Documentation/kbuild/kconfig-language.rst | 4 ++--
>  Makefile                                  | 2 +-
>  arch/Kconfig                              | 3 ---
>  arch/arm/boot/compressed/Makefile         | 3 +--
>  arch/mips/vdso/Makefile                   | 3 +--
>  arch/powerpc/kernel/Makefile              | 2 +-
>  arch/powerpc/platforms/powermac/Makefile  | 2 +-
>  arch/sparc/vdso/Makefile                  | 4 ++--
>  arch/um/Makefile                          | 3 +--
>  arch/x86/Makefile                         | 2 +-
>  arch/x86/boot/compressed/Makefile         | 2 +-
>  arch/x86/entry/vdso/Makefile              | 4 ++--
>  arch/x86/kernel/cpu/Makefile              | 3 +--
>  arch/x86/lib/Makefile                     | 2 +-
>  arch/x86/mm/Makefile                      | 7 +++----
>  arch/x86/power/Makefile                   | 3 +--
>  arch/x86/purgatory/Makefile               | 2 +-
>  arch/x86/um/vdso/Makefile                 | 2 +-
>  arch/x86/xen/Makefile                     | 5 ++---
>  drivers/firmware/efi/libstub/Makefile     | 2 +-
>  drivers/xen/Makefile                      | 3 +--
>  kernel/kcsan/Makefile                     | 3 +--

Is it possible that this patch drops the KCSAN portion? We have a patch
that is part of a series intended for 5.9 that also removes the
cc-option from -fno-stack-protector, but can't easily be dropped from
the surrounding series.

Please see: https://lkml.kernel.org/r/20200624190236.GA6603@paulmck-ThinkPad-P72

Thanks,
-- Marco