linux-kernel - Re: [PATCH v3 1/3] kasan, arm64: use ARCH_SLAB

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Date:   Wed, 9 Jan 2019 10:10:26 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev@...glegroups.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sparse@...r.kernel.org, linux-mm@...ck.org,
        linux-kbuild@...r.kernel.org
Cc:     Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Jann Horn <jannh@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Vishwath Mohan <vishwath@...gle.com>
Subject: Re: [PATCH v3 1/3] kasan, arm64: use ARCH_SLAB_MINALIGN instead of
 manual aligning

On 03/01/2019 18:45, Andrey Konovalov wrote:
> Instead of changing cache->align to be aligned to KASAN_SHADOW_SCALE_SIZE
> in kasan_cache_create() we can reuse the ARCH_SLAB_MINALIGN macro.
> 
> Suggested-by: Vincenzo Frascino <vincenzo.frascino@....com>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
>  arch/arm64/include/asm/cache.h | 6 ++++++
>  mm/kasan/common.c              | 2 --
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
> index 13dd42c3ad4e..eb43e09c1980 100644
> --- a/arch/arm64/include/asm/cache.h
> +++ b/arch/arm64/include/asm/cache.h
> @@ -58,6 +58,12 @@
>   */
>  #define ARCH_DMA_MINALIGN	(128)
>  
> +#ifdef CONFIG_KASAN_SW_TAGS
> +#define ARCH_SLAB_MINALIGN	(1ULL << KASAN_SHADOW_SCALE_SHIFT)
> +#else
> +#define ARCH_SLAB_MINALIGN	__alignof__(unsigned long long)
> +#endif
> +

Could you please remove the "#else" case here, because it is redundant (it is
defined in linux/slab.h as ifndef) and could be misleading in future?

>  #ifndef __ASSEMBLY__
>  
>  #include <linux/bitops.h>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 03d5d1374ca7..44390392d4c9 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -298,8 +298,6 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
>  		return;
>  	}
>  
> -	cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
> -
>  	*flags |= SLAB_KASAN;
>  }
>  
> 

-- 
Regards,
Vincenzo