From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f72.google.com (mail-io1-f72.google.com [209.85.166.72]) by kanga.kvack.org (Postfix) with ESMTP id 76F156B0006 for ; Wed, 14 Nov 2018 14:20:00 -0500 (EST) Received: by mail-io1-f72.google.com with SMTP id m1so4189306ioh.23 for ; Wed, 14 Nov 2018 11:20:00 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id p138-v6sor24502236itp.10.2018.11.14.11.19.59 for (Google Transport Security); Wed, 14 Nov 2018 11:19:59 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20181107172306.3w2pjecaggsvl5z2@lakrids.cambridge.arm.com> References: <20181107172306.3w2pjecaggsvl5z2@lakrids.cambridge.arm.com> From: Andrey Konovalov Date: Wed, 14 Nov 2018 20:19:57 +0100 Message-ID: Subject: Re: [PATCH v10 09/22] kasan: add tag related helper functions Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Mark Rutland 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, "open list:DOCUMENTATION" , LKML , Linux ARM , linux-sparse@vger.kernel.org, Linux Memory Management List , Linux Kbuild mailing list , Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan On Wed, Nov 7, 2018 at 6:23 PM, Mark Rutland wrote: > 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) Will do in v11, thanks!