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Date: Tue, 2 Feb 2021 18:39:35 +0100
From: Marco Elver <elver@...gle.com>
To: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
Vincenzo Frascino <vincenzo.frascino@....com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Alexander Potapenko <glider@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Will Deacon <will.deacon@....com>,
Andrey Ryabinin <aryabinin@...tuozzo.com>,
Peter Collingbourne <pcc@...gle.com>,
Evgenii Stepanov <eugenis@...gle.com>,
Branislav Rankov <Branislav.Rankov@....com>,
Kevin Brodsky <kevin.brodsky@....com>,
kasan-dev <kasan-dev@...glegroups.com>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>,
Linux Memory Management List <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 02/12] kasan, mm: optimize kmalloc poisoning
On Tue, 2 Feb 2021 at 18:16, Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> On Tue, Feb 2, 2021 at 5:25 PM Marco Elver <elver@...gle.com> wrote:
> >
> > > +#ifdef CONFIG_KASAN_GENERIC
> > > +
> > > +/**
> > > + * kasan_poison_last_granule - mark the last granule of the memory range as
> > > + * unaccessible
> > > + * @addr - range start address, must be aligned to KASAN_GRANULE_SIZE
> > > + * @size - range size
> > > + *
> > > + * This function is only available for the generic mode, as it's the only mode
> > > + * that has partially poisoned memory granules.
> > > + */
> > > +void kasan_poison_last_granule(const void *address, size_t size);
> > > +
> > > +#else /* CONFIG_KASAN_GENERIC */
> > > +
> > > +static inline void kasan_poison_last_granule(const void *address, size_t size) { }
>
> ^
>
> > > +
> > > +#endif /* CONFIG_KASAN_GENERIC */
> > > +
> > > /*
> > > * Exported functions for interfaces called from assembly or from generated
> > > * code. Declarations here to avoid warning about missing declarations.
>
> > > @@ -96,6 +92,16 @@ void kasan_poison(const void *address, size_t size, u8 value)
> > > }
> > > EXPORT_SYMBOL(kasan_poison);
> > >
> > > +#ifdef CONFIG_KASAN_GENERIC
> > > +void kasan_poison_last_granule(const void *address, size_t size)
> > > +{
> > > + if (size & KASAN_GRANULE_MASK) {
> > > + u8 *shadow = (u8 *)kasan_mem_to_shadow(address + size);
> > > + *shadow = size & KASAN_GRANULE_MASK;
> > > + }
> > > +}
> > > +#endif
> >
> > The function declaration still needs to exist in the dead branch if
> > !IS_ENABLED(CONFIG_KASAN_GENERIC). It appears in that case it's declared
> > (in kasan.h), but not defined. We shouldn't get linker errors because
> > the optimizer should remove the dead branch. Nevertheless, is this code
> > generally acceptable?
>
> The function is defined as empty when !CONFIG_KASAN_GENERIC, see above.
I missed that, thanks.
Reviewed-by: Marco Elver <elver@...gle.com>
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