linux-kernel - Re: [PATCH] kbuild: move <linux/compiler

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Date:   Tue, 27 Mar 2018 20:10:28 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     linux-kbuild <linux-kbuild@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sam Ravnborg <sam@...nborg.org>, Arnd Bergmann <arnd@...db.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] kbuild: move <linux/compiler_types.h> out of <linux/kconfig.h>

On Tue, Mar 27, 2018 at 7:40 PM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
> Since commit 28128c61e08e ("kconfig.h: Include compiler types to avoid
> missed struct attributes"), <linux/kconfig.h> pulls in kernel-space
> headers to unrelated file.
>
> Commit 0f9da844d877 ("MIPS: boot: Define __ASSEMBLY__ for its.S build")
> suppressed the build error by defining __ASSEMBLY__, but ITS (i.e. DTS)
> is not assembly, and should not include <linux/compiler_types.h> in the
> first place.
>
> Looking at arch/s390/tools/Makefile, host programs gen_facilities and
> gen_opcode_table now pull in <linux/compiler_types.h> as well.
>
> The motivation for that commit was to define necessary attributes
> before any struct is defined.  Obviously, this happens only in C.
>
> It is enough to include <linux/compiler_types.h> only when compiling
> C files, and only when compiling kernel space.
>
> Move the <linux/compiler_types.h> inclusion to c_flags.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
> I will also send a correct fix-up for MIPS Makefile later.

As long as the result is the same: it's impossible to define a
structure without defined attributes, I'm fine with it. :)

Question below...

>
>
>
>  include/linux/kconfig.h | 3 ---
>  scripts/Makefile.lib    | 1 +
>  2 files changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/include/linux/kconfig.h b/include/linux/kconfig.h
> index dcde947..cc8fa10 100644
> --- a/include/linux/kconfig.h
> +++ b/include/linux/kconfig.h
> @@ -70,7 +70,4 @@
>   */
>  #define IS_ENABLED(option) __or(IS_BUILTIN(option), IS_MODULE(option))
>
> -/* Make sure we always have all types and struct attributes defined. */
> -#include <linux/compiler_types.h>
> -
>  #endif /* __LINUX_KCONFIG_H */
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index c114ce5..07d0740 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -152,6 +152,7 @@ __cpp_flags     = $(call flags,_cpp_flags)
>  endif
>
>  c_flags        = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE)     \
> +                -include $(srctree)/include/linux/compiler_types.h       \

Why here instead of adding it to LINUXINCLUDE ?

>                  $(__c_flags) $(modkern_cflags)                           \
>                  $(basename_flags) $(modname_flags)
>
> --
> 2.7.4
>

-Kees

-- 
Kees Cook
Pixel Security