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Subject: Re: [PATCH] arm64: increase stack size for KASAN_EXTRA
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From: Qian Cai <cai@lca.pw>
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To: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Alexander Potapenko <glider@google.com>, Dmitry Vyukov <dvyukov@google.com>, kasan-dev <kasan-dev@googlegroups.com>, Linux-MM <linux-mm@kvack.org>, Linux ARM <linux-arm-kernel@lists.infradead.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>



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
>