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Tue, 02 Feb 2021 09:16:10 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Andrey Konovalov Date: Tue, 2 Feb 2021 18:15:58 +0100 Message-ID: Subject: Re: [PATCH 02/12] kasan, mm: optimize kmalloc poisoning To: Marco Elver Cc: Catalin Marinas , Vincenzo Frascino , Dmitry Vyukov , Alexander Potapenko , Andrew Morton , Will Deacon , Andrey Ryabinin , Peter Collingbourne , Evgenii Stepanov , Branislav Rankov , Kevin Brodsky , kasan-dev , Linux ARM , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 2, 2021 at 5:25 PM Marco Elver 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.