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

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Message-ID: <30b90e66-2ac0-82b3-b590-5a2b35fad446@arm.com>
Date:   Thu, 27 Aug 2020 14:45:09 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Andrey Konovalov <andreyknvl@...gle.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

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.

> 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