From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi1-f197.google.com (mail-oi1-f197.google.com [209.85.167.197]) by kanga.kvack.org (Postfix) with ESMTP id 88B406B052C for ; Wed, 7 Nov 2018 12:23:18 -0500 (EST) Received: by mail-oi1-f197.google.com with SMTP id u188-v6so11018921oie.23 for ; Wed, 07 Nov 2018 09:23:18 -0800 (PST) Received: from foss.arm.com (usa-sjc-mx-foss1.foss.arm.com. [217.140.101.70]) by mx.google.com with ESMTP id s200-v6si477598ois.222.2018.11.07.09.23.16 for ; Wed, 07 Nov 2018 09:23:17 -0800 (PST) Date: Wed, 7 Nov 2018 17:23:08 +0000 From: Mark Rutland Subject: Re: [PATCH v10 09/22] kasan: add tag related helper functions Message-ID: <20181107172306.3w2pjecaggsvl5z2@lakrids.cambridge.arm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Konovalov Cc: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sparse@vger.kernel.org, linux-mm@kvack.org, linux-kbuild@vger.kernel.org, Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan On Tue, Nov 06, 2018 at 06:30:24PM +0100, Andrey Konovalov wrote: > This commit adds a few helper functions, that are meant to be used to > work with tags embedded in the top byte of kernel pointers: to set, to > get or to reset (set to 0xff) the top byte. > > Reviewed-by: Andrey Ryabinin > Reviewed-by: Dmitry Vyukov > Signed-off-by: Andrey Konovalov > --- > arch/arm64/mm/kasan_init.c | 2 ++ > include/linux/kasan.h | 13 +++++++++ > mm/kasan/kasan.h | 55 ++++++++++++++++++++++++++++++++++++++ > mm/kasan/tags.c | 37 +++++++++++++++++++++++++ > 4 files changed, 107 insertions(+) > > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c > index 18ebc8994a7b..370b19d0e2fb 100644 > --- a/arch/arm64/mm/kasan_init.c > +++ b/arch/arm64/mm/kasan_init.c > @@ -249,6 +249,8 @@ void __init kasan_init(void) > memset(kasan_zero_page, KASAN_SHADOW_INIT, PAGE_SIZE); > cpu_replace_ttbr1(lm_alias(swapper_pg_dir)); > > + kasan_init_tags(); > + > /* At this point kasan is fully initialized. Enable error messages */ > init_task.kasan_depth = 0; > pr_info("KernelAddressSanitizer initialized\n"); > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > index 7f6574c35c62..4c9d6f9029f2 100644 > --- a/include/linux/kasan.h > +++ b/include/linux/kasan.h > @@ -169,6 +169,19 @@ static inline void kasan_cache_shutdown(struct kmem_cache *cache) {} > > #define KASAN_SHADOW_INIT 0xFF > > +void kasan_init_tags(void); > + > +void *kasan_reset_tag(const void *addr); > + > +#else /* CONFIG_KASAN_SW_TAGS */ > + > +static inline void kasan_init_tags(void) { } > + > +static inline void *kasan_reset_tag(const void *addr) > +{ > + return (void *)addr; > +} > + > +#ifdef CONFIG_KASAN_SW_TAGS > + > +#define KASAN_PTR_TAG_SHIFT 56 > +#define KASAN_PTR_TAG_MASK (0xFFUL << KASAN_PTR_TAG_SHIFT) > + > +u8 random_tag(void); > + > +static inline void *set_tag(const void *addr, u8 tag) > +{ > + u64 a = (u64)addr; > + > + a &= ~KASAN_PTR_TAG_MASK; > + a |= ((u64)tag << KASAN_PTR_TAG_SHIFT); > + > + return (void *)a; > +} > + > +static inline u8 get_tag(const void *addr) > +{ > + return (u8)((u64)addr >> KASAN_PTR_TAG_SHIFT); > +} > + > +static inline void *reset_tag(const void *addr) > +{ > + return set_tag(addr, KASAN_TAG_KERNEL); > +} We seem to be duplicating this functionality in several places. Could we please make it so that the arch code defines macros: arch_kasan_set_tag(addr, tag) arch_kasan_get_tag(addr) arch_kasan_reset_tag(addr) ... and use thoses consistently rather than open-coding them? > + > +#else /* CONFIG_KASAN_SW_TAGS */ > + > +static inline u8 random_tag(void) > +{ > + return 0; > +} > + > +static inline void *set_tag(const void *addr, u8 tag) > +{ > + return (void *)addr; > +} > + > +static inline u8 get_tag(const void *addr) > +{ > + return 0; > +} > + > +static inline void *reset_tag(const void *addr) > +{ > + return (void *)addr; > +} ... these can be defined in linux/kasan.h as: #define arch_kasan_set_tag(addr, tag) (addr) #define arch_kasan_get_tag(addr) 0 #define arch_kasan_reset_tag(addr) (addr) Thanks, Mark.