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[128.68.180.17]) by smtp.gmail.com with ESMTPSA id m1sm3205465lfb.56.2019.01.28.16.12.25 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 16:12:26 -0800 (PST) Reply-To: alex.popov@linux.com Subject: Re: [PATCH 0/3] gcc-plugins: Introduce stackinit plugin To: Kees Cook , linux-kernel@vger.kernel.org Cc: Ard Biesheuvel , Laura Abbott , xen-devel@lists.xenproject.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, dev@openvswitch.org, linux-kbuild@vger.kernel.org, linux-security-module@vger.kernel.org, kernel-hardening@lists.openwall.com, Greg KH , Jann Horn , William Kucharski , Jani Nikula , Edwin Zimmerman , Matthew Wilcox , Jeff Kirsher References: <20190123110349.35882-1-keescook@chromium.org> From: Alexander Popov Openpgp: preference=signencrypt Autocrypt: addr=alex.popov@linux.com; prefer-encrypt=mutual; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <20190123110349.35882-1-keescook@chromium.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 23.01.2019 14:03, Kees Cook wrote: > This adds a new plugin "stackinit" that attempts to perform unconditional > initialization of all stack variables Hello Kees! Hello everyone! I was curious about the performance impact of the initialization of all stack variables. So I did a very brief test with this plugin on top of 4.20.5. hackbench on Intel Core i7-4770 showed ~0.7% slowdown. hackbench on Kirin 620 (ARM Cortex-A53 Octa-core 1.2GHz) showed ~1.3% slowdown. This test involves the kernel scheduler and allocator. I can't say whether they use stack aggressively. Maybe performance tests of other subsystems (e.g. network subsystem) can show different numbers. Did you try? I've heard a hypothesis that the initialization of all stack variables would pollute CPU caches, which is critical for some types of computations. Maybe some micro-benchmarks can disprove/confirm that? Thanks! Best regards, Alexander