linux-kernel - Re: [PATCH v3 24/39] arm64: mte: Add in-kernel MTE helpers

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Date:   Fri, 25 Sep 2020 14:36:29 +0100
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, 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-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 24/39] arm64: mte: Add in-kernel MTE helpers



On 9/25/20 1:50 PM, Catalin Marinas wrote:
>>>> + */
>>>> +SYM_FUNC_START(mte_assign_mem_tag_range)
>>>> +	/* if (src == NULL) return; */
>>>> +	cbz	x0, 2f
>>>> +	/* if (size == 0) return; */
>>>> +	cbz	x1, 2f
>>> I find these checks unnecessary, as I said a couple of times before,
>>> just document the function pre-conditions. They are also incomplete
>>> (i.e. you check for NULL but not alignment).
>>>
>> I thought we agreed to harden the code further, based on [1]. Maybe I
>> misunderstood. I am going to remove them and extend the comment in the next version.
>>
>> [1]
>> https://lore.kernel.org/linux-arm-kernel/921c4ed0-b5b5-bc01-5418-c52d80f1af59@arm.com/
> Well, you concluded that but I haven't confirmed ;). Since it's called
> from a single place which does the checks already, I don't see the point
> in duplicating them. Documenting should be sufficient.

Have you ever heard about "tacit consent"? ;) Anw, fine by me, I will add a
comment here.

-- 
Regards,
Vincenzo