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From:   Alexander Potapenko <glider@google.com>
Date:   Wed, 11 Nov 2020 15:30:23 +0100
Message-ID: <CAG_fn=Vze9yV7Hy6rf-Sy+F0NP-bPPZZ8QYa3QQu5J8a1q=5hw@mail.gmail.com>
Subject: Re: [PATCH v9 15/44] kasan, arm64: only init shadow for software modes
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux Memory Management List <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Tue, Nov 10, 2020 at 11:11 PM Andrey Konovalov <andreyknvl@google.com> w=
rote:
>
> This is a preparatory commit for the upcoming addition of a new hardware
> tag-based (MTE-based) KASAN mode.
>
> Hardware tag-based KASAN won't be using shadow memory. Only initialize
> it when one of the software KASAN modes are enabled.
>
> No functional changes for software modes.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
> ---
> Change-Id: I055e0651369b14d3e54cdaa8c48e6329b2e8952d
> ---
>  arch/arm64/include/asm/kasan.h |  8 ++++++--
>  arch/arm64/mm/kasan_init.c     | 15 ++++++++++++++-
>  2 files changed, 20 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kasan.h b/arch/arm64/include/asm/kasa=
n.h
> index b0dc4abc3589..f7ea70d02cab 100644
> --- a/arch/arm64/include/asm/kasan.h
> +++ b/arch/arm64/include/asm/kasan.h
> @@ -13,6 +13,12 @@
>  #define arch_kasan_get_tag(addr)       __tag_get(addr)
>
>  #ifdef CONFIG_KASAN
> +void kasan_init(void);
> +#else
> +static inline void kasan_init(void) { }
> +#endif
> +
> +#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
>
>  /*
>   * KASAN_SHADOW_START: beginning of the kernel virtual addresses.
> @@ -33,12 +39,10 @@
>  #define _KASAN_SHADOW_START(va)        (KASAN_SHADOW_END - (1UL << ((va)=
 - KASAN_SHADOW_SCALE_SHIFT)))
>  #define KASAN_SHADOW_START      _KASAN_SHADOW_START(vabits_actual)
>
> -void kasan_init(void);
>  void kasan_copy_shadow(pgd_t *pgdir);
>  asmlinkage void kasan_early_init(void);
>
>  #else
> -static inline void kasan_init(void) { }
>  static inline void kasan_copy_shadow(pgd_t *pgdir) { }
>  #endif
>
> diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> index b24e43d20667..ffeb80d5aa8d 100644
> --- a/arch/arm64/mm/kasan_init.c
> +++ b/arch/arm64/mm/kasan_init.c
> @@ -21,6 +21,8 @@
>  #include <asm/sections.h>
>  #include <asm/tlbflush.h>
>
> +#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
> +
>  static pgd_t tmp_pg_dir[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
>
>  /*
> @@ -208,7 +210,7 @@ static void __init clear_pgds(unsigned long start,
>                 set_pgd(pgd_offset_k(start), __pgd(0));
>  }
>
> -void __init kasan_init(void)
> +static void __init kasan_init_shadow(void)
>  {
>         u64 kimg_shadow_start, kimg_shadow_end;
>         u64 mod_shadow_start, mod_shadow_end;
> @@ -269,6 +271,17 @@ void __init kasan_init(void)
>
>         memset(kasan_early_shadow_page, KASAN_SHADOW_INIT, PAGE_SIZE);
>         cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
> +}
> +
> +#else /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS) */
> +
> +static inline void __init kasan_init_shadow(void) { }
> +
> +#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
> +
> +void __init kasan_init(void)
> +{
> +       kasan_init_shadow();
>
>         /* At this point kasan is fully initialized. Enable error message=
s */
>         init_task.kasan_depth =3D 0;
> --
> 2.29.2.222.g5d2a92d10f8-goog
>


--=20
Alexander Potapenko
Software Engineer

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