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

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Date:   Thu, 29 Oct 2020 21:14:12 +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 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.