linux-kernel - Re: [PATCH RFC v2 07/21] kasan, arm64: move initialization message

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Date:   Tue, 3 Nov 2020 16:33:54 +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 07/21] kasan, arm64: move initialization message

On Thu, Oct 29, 2020 at 9:14 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
>
> On Wed, Oct 28, 2020 at 11:56 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
> >
> > On Thu, Oct 22, 2020 at 3:19 PM Andrey Konovalov <andreyknvl@...gle.com> wrote:
> > >
> > > Tag-based KASAN modes are fully initialized with kasan_init_tags(),
> > > while the generic mode only requireds kasan_init(). Move the
> > > initialization message for tag-based modes into kasan_init_tags().
> > >
> > > Also fix pr_fmt() usage for KASAN code: generic mode doesn't need it,
> >
> > Why doesn't it need it? What's the difference with tag modes?
>
> I need to reword the patch descriptions: it's not the mode that
> doesn't need it, it's the generic.c file, as it doesn't use any pr_*()
> functions.
>
> >
> > > tag-based modes should use "kasan:" instead of KBUILD_MODNAME.
> >
> > With generic KASAN I currently see:
> >
> > [    0.571473][    T0] kasan: KernelAddressSanitizer initialized
> >
> > So KBUILD_MODNAME somehow works. Is there some difference between files?
>
> That code is printed from arch/xxx/mm/kasan_init*.c, which has its own
> pr_fmt defined.
>
> >
> > > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > > Link: https://linux-review.googlesource.com/id/Idfd1e50625ffdf42dfc3dbf7455b11bd200a0a49
> > > ---
> > >  arch/arm64/mm/kasan_init.c | 3 +++
> > >  mm/kasan/generic.c         | 2 --
> > >  mm/kasan/hw_tags.c         | 4 ++++
> > >  mm/kasan/sw_tags.c         | 4 +++-
> > >  4 files changed, 10 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/arch/arm64/mm/kasan_init.c b/arch/arm64/mm/kasan_init.c
> > > index b6b9d55bb72e..8f17fa834b62 100644
> > > --- a/arch/arm64/mm/kasan_init.c
> > > +++ b/arch/arm64/mm/kasan_init.c
> > > @@ -290,5 +290,8 @@ void __init kasan_init(void)
> > >  {
> > >         kasan_init_shadow();
> > >         kasan_init_depth();
> > > +#if defined(CONFIG_KASAN_GENERIC)
> > > +       /* CONFIG_KASAN_SW/HW_TAGS also requires kasan_init_tags(). */
> >
> > A bit cleaner way may be to introduce kasan_init_early() and
> > kasan_init_late(). Late() will do tag init and always print the
> > message.
>
> It appears we'll also need kasan_init_even_later() for some
> MTE-related stuff. I'll try to figure out some sane naming scheme here
> and include it into the next version.

Actually, it looks like some arches already have
kasan_init_early/late() along with kasan_init(). I'd say we better
keep those for generic KASAN mode, and kasan_init_tags() for tag-based
modes.