linux-kernel - Re: [PATCH v2 1/3] kasan, arm64: use ARCH_SLAB

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Message-ID: <CAAeHK+yE38g0dSbL7LiVPSgECgdcJ5w7+kwaiBaRYr5YkHtbjQ@mail.gmail.com>
Date:   Thu, 3 Jan 2019 19:46:20 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     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>,
        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>,
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        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
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        Mark Brand <markbrand@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Vishwath Mohan <vishwath@...gle.com>
Subject: Re: [PATCH v2 1/3] kasan, arm64: use ARCH_SLAB_MINALIGN instead of
 manual aligning

On Wed, Jan 2, 2019 at 9:14 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Wed,  2 Jan 2019 18:36:06 +0100 Andrey Konovalov <andreyknvl@...gle.com> 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.
> >
> > ...
> >
> > --- a/arch/arm64/include/asm/kasan.h
> > +++ b/arch/arm64/include/asm/kasan.h
> > @@ -36,6 +36,10 @@
> >  #define KASAN_SHADOW_OFFSET     (KASAN_SHADOW_END - (1ULL << \
> >                                       (64 - KASAN_SHADOW_SCALE_SHIFT)))
> >
> > +#ifdef CONFIG_KASAN_SW_TAGS
> > +#define ARCH_SLAB_MINALIGN   (1ULL << KASAN_SHADOW_SCALE_SHIFT)
> > +#endif
> > +
> >  void kasan_init(void);
> >  void kasan_copy_shadow(pgd_t *pgdir);
> >  asmlinkage void kasan_early_init(void);
> > diff --git a/include/linux/slab.h b/include/linux/slab.h
> > index 11b45f7ae405..d87f913ab4e8 100644
> > --- a/include/linux/slab.h
> > +++ b/include/linux/slab.h
> > @@ -16,6 +16,7 @@
> >  #include <linux/overflow.h>
> >  #include <linux/types.h>
> >  #include <linux/workqueue.h>
> > +#include <linux/kasan.h>
> >
>
> This still seems unadvisable.  Like other architectures, arm defines
> ARCH_SLAB_MINALIGN in arch/arm/include/asm/cache.h.
> arch/arm/include/asm64/cache.h doesn't define ARCH_SLAB_MINALIGN
> afaict.
>
> If arch/arm/include/asm64/cache.h later gets a definition of
> ARCH_SLAB_MINALIGN then we again face the risk that different .c files
> will see different values of ARCH_SLAB_MINALIGN depending on which
> headers they include.
>
> So what to say about this?  The architecture's ARCH_SLAB_MINALIGN
> should be defined in the architecture's cache.h, end of story.  Not in
> slab.h, not in kasan.h.

Done in v3, thanks!

>
>
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