linux-kernel - Re: [PATCH RFC v2 10/21] kasan: inline random_tag for HW

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Date:   Wed, 28 Oct 2020 12:08:23 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Serban Constantinescu <serbanc@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC v2 10/21] kasan: inline random_tag for HW_TAGS

On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> Using random_tag() currently results in a function call. Move its
> definition to mm/kasan/kasan.h and turn it into a static inline function
> for hardware tag-based mode to avoid uneeded function call.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> Link: https://linux-review.googlesource.com/id/Iac5b2faf9a912900e16cca6834d621f5d4abf427
> ---
>  mm/kasan/hw_tags.c |  5 -----
>  mm/kasan/kasan.h   | 37 ++++++++++++++++++++-----------------
>  2 files changed, 20 insertions(+), 22 deletions(-)
>
> diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c
> index c3a0e83b5e7a..4c24bfcfeff9 100644
> --- a/mm/kasan/hw_tags.c
> +++ b/mm/kasan/hw_tags.c
> @@ -36,11 +36,6 @@ void kasan_unpoison_memory(const void *address, size_t size)
>                           round_up(size, KASAN_GRANULE_SIZE), get_tag(address));
>  }
>
> -u8 random_tag(void)
> -{
> -       return get_random_tag();
> -}
> -
>  bool check_invalid_free(void *addr)
>  {
>         u8 ptr_tag = get_tag(addr);
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 0ccbb3c4c519..94ba15c2f860 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -188,6 +188,12 @@ static inline bool addr_has_metadata(const void *addr)
>
>  #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
>
> +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> +void print_tags(u8 addr_tag, const void *addr);
> +#else
> +static inline void print_tags(u8 addr_tag, const void *addr) { }
> +#endif
> +
>  bool check_invalid_free(void *addr);
>
>  void *find_first_bad_addr(void *addr, size_t size);
> @@ -223,23 +229,6 @@ static inline void quarantine_reduce(void) { }
>  static inline void quarantine_remove_cache(struct kmem_cache *cache) { }
>  #endif
>
> -#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> -
> -void print_tags(u8 addr_tag, const void *addr);
> -
> -u8 random_tag(void);
> -
> -#else
> -
> -static inline void print_tags(u8 addr_tag, const void *addr) { }
> -
> -static inline u8 random_tag(void)
> -{
> -       return 0;
> -}
> -
> -#endif
> -
>  #ifndef arch_kasan_set_tag
>  static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
>  {
> @@ -273,6 +262,20 @@ static inline const void *arch_kasan_set_tag(const void *addr, u8 tag)
>  #define get_mem_tag(addr)                      arch_get_mem_tag(addr)
>  #define set_mem_tag_range(addr, size, tag)     arch_set_mem_tag_range((addr), (size), (tag))
>
> +#ifdef CONFIG_KASAN_SW_TAGS
> +u8 random_tag(void);
> +#elif defined(CONFIG_KASAN_HW_TAGS)
> +static inline u8 random_tag(void)
> +{
> +       return get_random_tag();

What's the difference between random_tag() and get_random_tag()? Do we
need both?


> +}
> +#else
> +static inline u8 random_tag(void)
> +{
> +       return 0;
> +}
> +#endif
> +
>  /*
>   * Exported functions for interfaces called from assembly or from generated
>   * code. Declarations here to avoid warning about missing declarations.
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>