linux-kernel - Re: [PATCH] kasan: add no_sanitize attribute for clang builds

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Date:   Fri, 13 Apr 2018 18:31:46 +0300
From:   Andrey Ryabinin <aryabinin@...tuozzo.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Will Deacon <will.deacon@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Sandipan Das <sandipan@...ux.vnet.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        linux-mm@...ck.org
Cc:     Kostya Serebryany <kcc@...gle.com>
Subject: Re: [PATCH] kasan: add no_sanitize attribute for clang builds



On 04/12/2018 08:29 PM, Andrey Konovalov wrote:
> KASAN uses the __no_sanitize_address macro to disable instrumentation
> of particular functions. Right now it's defined only for GCC build,
> which causes false positives when clang is used.
> 
> This patch adds a definition for clang.
> 
> Note, that clang's revision 329612 or higher is required.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
>  include/linux/compiler-clang.h | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index ceb96ecab96e..5a1d8580febe 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -25,6 +25,11 @@
>  #define __SANITIZE_ADDRESS__
>  #endif
>  
> +#ifdef CONFIG_KASAN

If, for whatever reason, developer decides to add __no_sanitize_address to some
generic function, guess what will happen next when he/she will try to build CONFIG_KASAN=n kernel?

> +#undef __no_sanitize_address
> +#define __no_sanitize_address __attribute__((no_sanitize("address")))
> +#endif
> +
>  /* Clang doesn't have a way to turn it off per-function, yet. */
>  #ifdef __noretpoline
>  #undef __noretpoline
>