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

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Message-ID: <CAAeHK+ws8H=Ba7Q2J-UiaweK1KuKYMQA17RD3U3CO7b5FvMx2g@mail.gmail.com>
Date:   Thu, 27 Aug 2020 16:36:19 +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 3:42 PM Vincenzo Frascino
<vincenzo.frascino@....com> wrote:
>
> Hi Andrey,
>
> On 8/27/20 1:43 PM, Andrey Konovalov wrote:
> > 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.
> >
>
> I am happy to do that. I will be on holiday though from this Saturday till the
> September, 9. After that I will start the rebasing.

Ah, OK. I'll see if I can do the rebase and fix some of Catalin's
comments myself then. I'll let you know the current status once you're
back.

>
> > 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.
> >
>
> I can reuse the patches as they are, unless they require changes when I start
> rebasing. In such a case to not duplicate the work I will scale back to use a
> simple module.
>
> --
> Regards,
> Vincenzo