linux-kernel - Re: [PATCH 26/35] kasan, arm64: Enable TBI EL1

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Date:   Thu, 27 Aug 2020 14:43:25 +0200
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Vincenzo Frascino <vincenzo.frascino@....com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Elena Petrova <lenaptr@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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 26/35] kasan, arm64: Enable TBI EL1

On Thu, Aug 27, 2020 at 1:15 PM Vincenzo Frascino
<vincenzo.frascino@....com> wrote:
>
>
>
> On 8/27/20 12:13 PM, Catalin Marinas wrote:
> > On Thu, Aug 27, 2020 at 12:05:55PM +0100, Vincenzo Frascino wrote:
> >> On 8/27/20 11:40 AM, Catalin Marinas wrote:
> >>> On Fri, Aug 14, 2020 at 07:27:08PM +0200, Andrey Konovalov wrote:
> >>>> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> >>>> index 152d74f2cc9c..6880ddaa5144 100644
> >>>> --- a/arch/arm64/mm/proc.S
> >>>> +++ b/arch/arm64/mm/proc.S
> >>>> @@ -38,7 +38,7 @@
> >>>>  /* PTWs cacheable, inner/outer WBWA */
> >>>>  #define TCR_CACHE_FLAGS   TCR_IRGN_WBWA | TCR_ORGN_WBWA
> >>>>
> >>>> -#ifdef CONFIG_KASAN_SW_TAGS
> >>>> +#if defined(CONFIG_KASAN_SW_TAGS) || defined(CONFIG_KASAN_HW_TAGS)
> >>>>  #define TCR_KASAN_FLAGS TCR_TBI1
> >>>>  #else
> >>>>  #define TCR_KASAN_FLAGS 0
> >>>
> >>> I prefer to turn TBI1 on only if MTE is present. So on top of the v8
> >>> user series, just do this in __cpu_setup.
> >>
> >> Not sure I understand... Enabling TBI1 only if MTE is present would break
> >> KASAN_SW_TAGS which is based on TBI1 but not on MTE.
> >
> > You keep the KASAN_SW_TAGS as above but for HW_TAGS, only set TBI1 later
> > in __cpu_setup().
> >
>
> Ok, sounds good.

Sounds good to me too.

Vincenzo, could you take care of Catalin's comments on your (arm64)
patches, do the rebase onto user mte v8, and share it with me? I'll
work on KASAN changes in the meantime, and then integrate everything
together for v2.

Perhaps the best way to test only the arm64 part is writing a simple
module that causes an MTE fault. (At least that's what I did when I
was testing core in-kernel MTE patches separately.) Or reuse this
series, all KASAN patches should rebase cleanly on top of the latest
mainline.