linux-kernel - Re: [PATCH 05/11] kasan, arm64: allow using KUnit tests with HW

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Date:   Fri, 15 Jan 2021 14:11:37 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/11] kasan, arm64: allow using KUnit tests with HW_TAGS mode

On Tue, Jan 12, 2021 at 8:01 PM Catalin Marinas <catalin.marinas@....com> wrote:
>
> On Tue, Jan 05, 2021 at 07:27:49PM +0100, Andrey Konovalov wrote:
> > diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> > index 3c40da479899..57d3f165d907 100644
> > --- a/arch/arm64/mm/fault.c
> > +++ b/arch/arm64/mm/fault.c
> > @@ -302,12 +302,20 @@ static void die_kernel_fault(const char *msg, unsigned long addr,
> >  static void report_tag_fault(unsigned long addr, unsigned int esr,
> >                            struct pt_regs *regs)
> >  {
> > -     bool is_write  = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
> > +     static bool reported;
> > +     bool is_write;
> > +
> > +     if (READ_ONCE(reported))
> > +             return;
> > +
> > +     if (mte_report_once())
> > +             WRITE_ONCE(reported, true);
>
> I guess the assumption here is that you don't get any report before the
> tests start and temporarily set report_once to false. It's probably
> fine, if we get a tag check failure we'd notice in the logs anyway.

Good point. I'll add a note in a comment in v4.

> >       /*
> >        * SAS bits aren't set for all faults reported in EL1, so we can't
> >        * find out access size.
> >        */
> > +     is_write = ((esr & ESR_ELx_WNR) >> ESR_ELx_WNR_SHIFT) != 0;
>
> I now noticed, you could write this in a shorter way:
>
>         is_write = !!(esr & ESR_ELx_WNR);
>
> >       kasan_report(addr, 0, is_write, regs->pc);
> >  }

Will do in v4.

> The patch looks fine to me.
>
> Reviewed-by: Catalin Marinas <catalin.marinas@....com>

Thanks!