linux-kernel - Re: [PATCH] arm64: increase stack size for KASAN

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Date:   Tue, 11 Dec 2018 22:54:37 -0500
From:   Qian Cai <cai@....pw>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] arm64: increase stack size for KASAN_EXTRA



On 12/11/18 6:06 PM, Arnd Bergmann wrote:
>> I am thinking about something it is probably best just waiting for those major
>> distors to complete upgrading to GCC9 or back-porting those stack reduction
>> patches first. Then, it is good time to tie up loose ends for those default
>> stack sizes in all combinations.
> 
> I was basically trying to make sure we don't forget it when it gets to that.

I added a reminder in my calendar to check the GCC9 adoption in Q2 FY19.

> 
> Another alternative would be to just disable KASAN_EXTRA now
> for gcc versions before 9, which essentially means for everyone,
> but then we get it back once a working version gets released. As
> I understand, this kasan option is actually fairly useless given its
> cost, so very few people would miss it.
> 
> On a related note, I think we have to turn off asan-stack entirely
> on all released clang versions. asan-stack in general is much more
> useful than the use-after-scope check, but we clang produces some
> very large stack frames with it and we probably can't even work
> around it with KASAN_THREAD_SHIFT=2 but would need even
> more than that otherwise.
> 
>          Arnd
>