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

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Message-ID: <CAAeHK+x+5EcgiS8wZ9mbh-a32w4_CVOdrzw8yrtpPuquaJrPQA@mail.gmail.com>
Date:   Fri, 30 Oct 2020 16:48:23 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Dmitry Vyukov <dvyukov@...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 Wed, Oct 28, 2020 at 12:08 PM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> 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?

Not really. Will simplify this in the next version and give cleaner names.