linux-kernel - Re: [PATCH] efi/libstub: Disable some warnings for x86{,

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Date:   Wed, 24 Oct 2018 09:22:01 +0200
From:   Sedat Dilek <sedat.dilek@...il.com>
To:     natechancellor@...il.com
Cc:     ard.biesheuvel@...aro.org, linux-efi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] efi/libstub: Disable some warnings for x86{,_64}

On Tue, Oct 23, 2018 at 7:53 PM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Fri, Oct 12, 2018 at 06:03:49PM -0700, Nathan Chancellor wrote:
> > When building the kernel with Clang, some disabled warnings appear
> > because this Makefile overrides KBUILD_CFLAGS for x86{,_64}. Add them to
> > this list so that the build is clean again.
> >
> > -Wpointer-sign was disabled for the whole kernel before the beginning
> > of git history.
> >
> > -Waddress-of-packed-member was disabled for the whole kernel in
> > commit bfb38988c51e ("kbuild: clang: Disable 'address-of-packed-member'
> > warning") and for x86/boot/compressed in commit 20c6c1890455 ("x86/boot:
> > Disable the address-of-packed-member compiler warning").
> >
> > -Wgnu was disabled for the whole kernel in commit 61163efae020 ("kbuild:
> > LLVMLinux: Add Kbuild support for building kernel with Clang") and for
> > x86/boot/compressed in commit 6c3b56b19730 ("x86/boot: Disable Clang
> > warnings about GNU extensions").
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/112
> > Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
> > ---
> >
> > Nick expressed concern that this Makefile is overwriting KBUILD_CFLAGS
> > and suggested potentially rewriting the x86 portion of this Makefile to
> > behave like the arm/arm64 one where problematic flags are filtered out.
> > While that comes to fruition, it would be nice for this folder to behave
> > like the rest of the kernel when it comes to this warnings so that the
> > build is cleaner, thus this patch.
> >
> >  drivers/firmware/efi/libstub/Makefile | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> > index c51627660dbb..d9845099635e 100644
> > --- a/drivers/firmware/efi/libstub/Makefile
> > +++ b/drivers/firmware/efi/libstub/Makefile
> > @@ -9,7 +9,10 @@ cflags-$(CONFIG_X86_32)              := -march=i386
> >  cflags-$(CONFIG_X86_64)              := -mcmodel=small
> >  cflags-$(CONFIG_X86)         += -m$(BITS) -D__KERNEL__ -O2 \
> >                                  -fPIC -fno-strict-aliasing -mno-red-zone \
> > -                                -mno-mmx -mno-sse -fshort-wchar
> > +                                -mno-mmx -mno-sse -fshort-wchar \
> > +                                -Wno-pointer-sign \
> > +                                $(call cc-disable-warning, address-of-packed-member) \
> > +                                $(call cc-disable-warning, gnu)
> >
> >  # arm64 uses the full KBUILD_CFLAGS so it's necessary to explicitly
> >  # disable the stackleak plugin
> > --
> > 2.19.1
> >
>
> + Sedat for review/testing.

Thanks Nathan.

Reviewed-by: Sedat Dilek <sedat.dilek@...il.com>
Tested-by: Sedat Dilek <sedat.dilek@...il.com>
[ Reported-by: Sedat Dilek <sedat.dilek@...il.com> ]
[ See duplicate "arch/x86/include/asm/processor.h: Warning
-Waddress-of-packed-member "
<https://github.com/ClangBuiltLinux/linux/issues/234> ]

Regards,
- Sedat -