From: Andrey Konovalov <andreyknvl@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>,
Alexander Potapenko <glider@google.com>,
Dmitry Vyukov <dvyukov@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Christoph Lameter <cl@linux.com>,
Mark Rutland <mark.rutland@arm.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Marc Zyngier <marc.zyngier@arm.com>,
Dave Martin <dave.martin@arm.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
"Eric W . Biederman" <ebiederm@xmission.com>,
Ingo Molnar <mingo@kernel.org>,
Paul Lawrence <paullawrence@google.com>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Arnd Bergmann <arnd@arndb.de>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Kate Stewart <kstewart@linuxfoundation.org>,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
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Chintan Pandya <cpandya@codeaurora.org>,
Vishwath Mohan <vishwath@google.com>
Subject: Re: [PATCH mm] kasan, arm64: use ARCH_SLAB_MINALIGN instead of manual aligning
Date: Thu, 20 Dec 2018 14:02:45 +0100 [thread overview]
Message-ID: <CAAeHK+yggnKfkycdUdTHG4MvWBMq_XK70m0rQuH873DZU+RnGQ@mail.gmail.com> (raw)
In-Reply-To: <20181218125453.4c5e6c056d31ccaa3a73d4a5@linux-foundation.org>
On Tue, Dec 18, 2018 at 9:55 PM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue, 18 Dec 2018 14:30:33 +0100 Andrey Konovalov <andreyknvl@google.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);
>
> This looks unreliable. include/linux/slab.h has
>
> /*
> * Setting ARCH_SLAB_MINALIGN in arch headers allows a different alignment.
> * Intended for arches that get misalignment faults even for 64 bit integer
> * aligned buffers.
> */
> #ifndef ARCH_SLAB_MINALIGN
> #define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
> #endif
>
> so if a .c file includes arch/arm64/include/asm/kasan.h after
> include/linux/slab.h, it can get a macro-redefined warning. If the .c
> file includes those headers in the other order, ARCH_SLAB_MINALIGN will
> get a different value compared to other .c files.
>
> Or something like that.
>
> Different architectures define ARCH_SLAB_MINALIGN in different place:
>
> ./arch/microblaze/include/asm/page.h:#define ARCH_SLAB_MINALIGN L1_CACHE_BYTES
> ./arch/arm/include/asm/cache.h:#define ARCH_SLAB_MINALIGN 8
> ./arch/sh/include/asm/page.h:#define ARCH_SLAB_MINALIGN 8
> ./arch/c6x/include/asm/cache.h:#define ARCH_SLAB_MINALIGN L1_CACHE_BYTES
> ./arch/sparc/include/asm/cache.h:#define ARCH_SLAB_MINALIGN __alignof__(unsigned long long)
> ./arch/xtensa/include/asm/processor.h:#define ARCH_SLAB_MINALIGN STACK_ALIGN
>
> which is rather bad of us.
>
> But still. I think your definition should occur in an arch header file
> which is reliably included from slab.h. And kasan code should get its
> definition of ARCH_SLAB_MINALIGN by including slab.h.
>
KASAN code doesn't use this macro directly, so I don't think it needs
to get it's definition.
What do you think about adding #include <linux/kasan.h> into
linux/slab.h? Perhaps with a comment that this is needed to get
definition of ARCH_SLAB_MINALIGN?
prev parent reply other threads:[~2018-12-20 13:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-18 13:30 Andrey Konovalov
2018-12-18 20:54 ` Andrew Morton
2018-12-20 13:02 ` Andrey Konovalov [this message]
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