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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id 195sm8762104qki.76.2018.12.11.19.54.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 Dec 2018 19:54:39 -0800 (PST) Subject: Re: [PATCH] arm64: increase stack size for KASAN_EXTRA To: Arnd Bergmann Cc: Catalin Marinas , Will Deacon , Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , kasan-dev , Linux-MM , Linux ARM , Linux Kernel Mailing List References: <721E7B42-2D55-4866-9C1A-3E8D64F33F9C@gmx.us> <20181207223449.38808-1-cai@lca.pw> <1544548707.18411.3.camel@lca.pw> <1544565158.18411.5.camel@lca.pw> <1544565572.18411.7.camel@lca.pw> <1544566937.18411.9.camel@lca.pw> From: Qian Cai Message-ID: <9248f272-4b8f-183d-73eb-28fed1debcd2@lca.pw> Date: Tue, 11 Dec 2018 22:54:37 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-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 >