Re: [PATCH -mm] fixup "Decouple build from userspace headers"

From: Masahiro Yamada <masahiroy@kernel.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH -mm] fixup "Decouple build from userspace headers"
Date: Sun, 18 Jul 2021 21:36:00 +0900	[thread overview]
Message-ID: <CAK7LNASq9DwxTF90u_8XZJo8VBLbEPDbP8kVk6c+AHpaCtH01g@mail.gmail.com> (raw)
In-Reply-To: <YPClYgoJOTUn4V0w@localhost.localdomain>

On Fri, Jul 16, 2021 at 6:15 AM Alexey Dobriyan <adobriyan@gmail.com> wrote:
>
> Allow to find SIMD headers where necessary.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
> ---
>
>         fold into decouple-build-from-userspace-headers.patch
>
>  arch/arm64/lib/Makefile   |    2 +-
>  arch/powerpc/lib/Makefile |    2 +-
>  lib/raid6/Makefile        |    4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)

OK. Perhaps, we can import <arm_neon.h> and  <altivec.h>
into the kernel tree as we did for <stdarg.h>,
then remove "-isystem $(shell $(CC) -print-file-name=include)"
entirely, but I did not look into it.

If we can avoid the arm_neon.h mess,
we can clean up arch/arm/include/uapi/asm/types.h as well.
It is a possible future work.

Anyway, could you add some comments?
(see blew)

> --- a/arch/arm64/lib/Makefile
> +++ b/arch/arm64/lib/Makefile
> @@ -8,7 +8,7 @@ lib-y           := clear_user.o delay.o copy_from_user.o                \
>  ifeq ($(CONFIG_KERNEL_MODE_NEON), y)
>  obj-$(CONFIG_XOR_BLOCKS)       += xor-neon.o
>  CFLAGS_REMOVE_xor-neon.o       += -mgeneral-regs-only
> -CFLAGS_xor-neon.o              += -ffreestanding

Can you add comment, # for <arm_neon.h>

> +CFLAGS_xor-neon.o              += -ffreestanding -isystem $(shell $(CC) -print-file-name=include)
>  endif
>
>  lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -64,6 +64,6 @@ obj-$(CONFIG_PPC_LIB_RHEAP) += rheap.o
>  obj-$(CONFIG_FTR_FIXUP_SELFTEST) += feature-fixups-test.o
>
>  obj-$(CONFIG_ALTIVEC)  += xor_vmx.o xor_vmx_glue.o
> -CFLAGS_xor_vmx.o += -maltivec $(call cc-option,-mabi=altivec)

Can you add comment, # for <altivec.h>

> +CFLAGS_xor_vmx.o += -maltivec $(call cc-option,-mabi=altivec) -isystem $(shell $(CC) -print-file-name=include)
>
>  obj-$(CONFIG_PPC64) += $(obj64-y)
> --- a/lib/raid6/Makefile
> +++ b/lib/raid6/Makefile
> @@ -13,7 +13,7 @@ raid6_pq-$(CONFIG_S390) += s390vx8.o recov_s390xc.o
>  hostprogs      += mktables
>
>  ifeq ($(CONFIG_ALTIVEC),y)
> -altivec_flags := -maltivec $(call cc-option,-mabi=altivec)

Can you add comment, # for <altivec.h>

> +altivec_flags := -maltivec $(call cc-option,-mabi=altivec) -isystem $(shell $(CC) -print-file-name=include)
>
>  ifdef CONFIG_CC_IS_CLANG
>  # clang ppc port does not yet support -maltivec when -msoft-float is
> @@ -33,7 +33,7 @@ endif
>  # The GCC option -ffreestanding is required in order to compile code containing
>  # ARM/NEON intrinsics in a non C99-compliant environment (such as the kernel)
>  ifeq ($(CONFIG_KERNEL_MODE_NEON),y)
> -NEON_FLAGS := -ffreestanding

Can you add comment, # for <arm_neon.h>

> +NEON_FLAGS := -ffreestanding -isystem $(shell $(CC) -print-file-name=include)
>  ifeq ($(ARCH),arm)
>  NEON_FLAGS += -march=armv7-a -mfloat-abi=softfp -mfpu=neon
>  endif

-- 
Best Regards
Masahiro Yamada