[PATCH 08/14] powerpc/vdso: Remove an unsupported flag from vgettimeofday-32.o with clang

[Nick Desaulniers]

On Wed, Jan 4, 2023 at 11:55 AM Nathan Chancellor <nathan at kernel.org> wrote:
>
> When clang's -Qunused-arguments is dropped from KBUILD_CPPFLAGS, it
> warns:
>
>   clang-16: error: argument unused during compilation: '-fno-stack-clash-protection' [-Werror,-Wunused-command-line-argument]
>
> This flag is supported for 64-bit powerpc but not 32-bit, hence the warning.
> Just remove the flag from vgettimeofday-32.o's CFLAGS when using clang, as has
> been done for other flags previously.
>
> Signed-off-by: Nathan Chancellor <nathan at kernel.org>

Hmm...so this was added by the top level Makefile doing a cc-option
test.  How did the test pass if this was unsupported? That worries me
that perhaps other cc-option tests are passing erroneously for certain
ppc -m32/-m64 configs?

> ---
> Cc: mpe at ellerman.id.au
> Cc: npiggin at gmail.com
> Cc: christophe.leroy at csgroup.eu
> Cc: linuxppc-dev at lists.ozlabs.org
> ---
>  arch/powerpc/kernel/vdso/Makefile | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/arch/powerpc/kernel/vdso/Makefile b/arch/powerpc/kernel/vdso/Makefile
> index 769b62832b38..4ee7d36ce752 100644
> --- a/arch/powerpc/kernel/vdso/Makefile
> +++ b/arch/powerpc/kernel/vdso/Makefile
> @@ -16,6 +16,11 @@ ifneq ($(c-gettimeofday-y),)
>    CFLAGS_vgettimeofday-32.o += -ffreestanding -fasynchronous-unwind-tables
>    CFLAGS_REMOVE_vgettimeofday-32.o = $(CC_FLAGS_FTRACE)
>    CFLAGS_REMOVE_vgettimeofday-32.o += -mcmodel=medium -mabi=elfv1 -mabi=elfv2 -mcall-aixdesc
> +  # This flag is supported by clang for 64-bit but not 32-bit so it will cause
> +  # an unused command line flag warning for this file.
> +  ifdef CONFIG_CC_IS_CLANG
> +  CFLAGS_REMOVE_vgettimeofday-32.o += -fno-stack-clash-protection
> +  endif
>    CFLAGS_vgettimeofday-64.o += -include $(c-gettimeofday-y)
>    CFLAGS_vgettimeofday-64.o += $(DISABLE_LATENT_ENTROPY_PLUGIN)
>    CFLAGS_vgettimeofday-64.o += $(call cc-option, -fno-stack-protector)
>
> --
> 2.39.0



-- 
Thanks,
~Nick Desaulniers