linux-kernel - Re: [PATCH V2 03/41] compiler_types.h: Add __noinstr

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Date:   Mon, 27 Sep 2021 11:09:35 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Marco Elver <elver@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: [PATCH V2 03/41] compiler_types.h: Add __noinstr_section() for
 noinstr

On Sun, Sep 26, 2021 at 11:08:00PM +0800, Lai Jiangshan wrote:
> From: Lai Jiangshan <laijs@...ux.alibaba.com>
> 
> And it will be extended for C entry code.
> 
> Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> ---
>  include/linux/compiler_types.h | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
> index b6ff83a714ca..3c77631c68bd 100644
> --- a/include/linux/compiler_types.h
> +++ b/include/linux/compiler_types.h
> @@ -208,10 +208,12 @@ struct ftrace_likely_data {
>  #endif
>  
>  /* Section for code which can't be instrumented at all */
> -#define noinstr								\
> -	noinline notrace __attribute((__section__(".noinstr.text")))	\
> +#define __noinstr_section(section)				\

bikeshed: this could be just __noinstr(section) instead
of __noinstr_section(section) just to avoid semi-redundant
information. *shrug*

Reviewed-by: Kees Cook <keescook@...omium.org>

> +	noinline notrace __attribute((__section__(section)))	\
>  	__no_kcsan __no_sanitize_address __no_profile __no_sanitize_coverage
>  
> +#define noinstr __noinstr_section(".noinstr.text")
> +
>  #endif /* __KERNEL__ */
>  
>  #endif /* __ASSEMBLY__ */
> -- 
> 2.19.1.6.gb485710b
> 

-- 
Kees Cook