linux-kernel - Re: [PATCH mm v4 28/39] kasan, page_alloc: allow skipping unpoisoning for HW

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Date:   Tue, 21 Dec 2021 13:19:45 +0100
From:   Marco Elver <elver@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH mm v4 28/39] kasan, page_alloc: allow skipping unpoisoning
 for HW_TAGS

On Tue, 21 Dec 2021 at 13:14, Marco Elver <elver@...gle.com> wrote:
>
> On Mon, Dec 20, 2021 at 11:02PM +0100, andrey.konovalov@...ux.dev wrote:
> [...]
> > +static inline bool should_skip_kasan_unpoison(gfp_t flags, bool init_tags)
> > +{
> > +     /* Don't skip if a software KASAN mode is enabled. */
> > +     if (IS_ENABLED(CONFIG_KASAN_GENERIC) ||
> > +         IS_ENABLED(CONFIG_KASAN_SW_TAGS))
> > +             return false;
> > +
> > +     /* Skip, if hardware tag-based KASAN is not enabled. */
> > +     if (!kasan_hw_tags_enabled())
> > +             return true;
>
> Same question here: why is IS_ENABLED(CONFIG_KASAN_{GENERIC,SW_TAGS})
> check required if kasan_hw_tags_enabled() is always false if one of
> those is configured?

Hmm, I pattern-matched too quickly. In this case there's probably no
way around it because the return value is different, so not exactly
like the should_skip_init().