linux-kernel - Re: [PATCH v3] Compiler Attributes: don't pollute userspace with macro definitions

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Message-ID: <CANiq72ndmEBLm_0A6iKXta1rVhYgsaHBL6QE+UFa7xFt8xdzTA@mail.gmail.com>
Date:   Fri, 14 Dec 2018 17:06:33 +0100
From:   Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:     liuxiaozhou@...edance.com
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Paul Burton <paul.burton@...s.com>,
        Kees Cook <keescook@...omium.org>,
        Arnd Bergmann <arnd@...db.de>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] Compiler Attributes: don't pollute userspace with
 macro definitions

On Fri, Dec 14, 2018 at 3:16 PM Xiaozhou Liu <liuxiaozhou@...edance.com> wrote:
>
> Macros 'inline' and '__gnu_inline' used to be defined in compiler-gcc.h,
> which was (and is) included entirely in (__KERNEL__ && !__ASSEMBLY__).
> Commit 815f0ddb346c ("include/linux/compiler*.h: make compiler-*.h mutually
> exclusive") had those macros exposed to userspace, unintentionally.
>
> Then commit a3f8a30f3f00 ("Compiler Attributes: use feature checks
> instead of version checks") moved '__gnu_inline' back into
> (__KERNEL__ && !__ASSEMBLY__) and 'inline' was left behind. Since 'inline'
> depends on '__gnu_inline', compiling error showing "unknown type name
> ‘__gnu_inline’" will pop up, if userspace somehow includes
> <linux/compiler.h>.
>
> Other macros like __must_check, notrace, etc. are in a similar situation.
> So just move all these macros back into (__KERNEL__ && !__ASSEMBLY__).
>
> Note:
>   1. This patch only affects what userspace sees.
>   2. __must_check (when !CONFIG_ENABLE_MUST_CHECK) and noinline_for_stack
>      were once defined in __KERNEL__ only, but we believe that they can
>      be put into !__ASSEMBLY__ too.
>
> Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>
> Signed-off-by: Xiaozhou Liu <liuxiaozhou@...edance.com>

Thanks Xiaozhou, picked into compiler-attributes with a slightly
modified title (since it is not about compiler attributes this time),
and let's see if there is any problem with it in linux-next.

Nick: I kept your Ack, even if it is a different patch. Let me know if
you don't want to Ack this version.

Cheers,
Miguel