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[67.180.167.114]) by smtp.gmail.com with ESMTPSA id 5-v6sm24652882pgc.86.2018.08.01.04.28.47 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 01 Aug 2018 04:28:49 -0700 (PDT) Subject: Re: SLAB_TYPESAFE_BY_RCU without constructors (was Re: [PATCH v4 13/17] khwasan: add hooks implementation) To: Dmitry Vyukov , Eric Dumazet Cc: Andrey Ryabinin , Linus Torvalds , Christoph Lameter , Theodore Ts'o , Jan Kara , linux-ext4@vger.kernel.org, Greg Kroah-Hartman , Pablo Neira Ayuso , Jozsef Kadlecsik , Florian Westphal , David Miller , NetFilter , coreteam@netfilter.org, Network Development , Gerrit Renker , dccp@vger.kernel.org, Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Dave Airlie , intel-gfx , DRI , Eric Dumazet , Alexey Kuznetsov , Hideaki YOSHIFUJI , Ursula Braun , linux-s390 , Linux Kernel Mailing List , Andrew Morton , linux-mm , Andrey Konovalov References: <01000164f169bc6b-c73a8353-d7d9-47ec-a782-90aadcb86bfb-000000@email.amazonses.com> <30ee6c72-dc90-275a-8e23-54221f393cb0@virtuozzo.com> From: Eric Dumazet Message-ID: Date: Wed, 1 Aug 2018 04:28:47 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 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 08/01/2018 03:34 AM, Dmitry Vyukov wrote: > On Wed, Aug 1, 2018 at 12:23 PM, Eric Dumazet wrote: >> On 08/01/2018 02:03 AM, Andrey Ryabinin wrote: >> >>> I can't think of any advantage in not having the constructor. >> >> I can't see any advantage adding another indirect call, >> in RETPOLINE world. > > Can you please elaborate what's the problem here? > If slab ctor call have RETPOLINE, then using ctors more does not > introduce any security problems and they are not _that_ slow. They _are_ slow, when we have dozens of them in a code path. I object "having to add" yet another indirect call, if this can be avoided [*] If some people want to use ctor, fine, but do not request this. [*] This can be tricky, but worth the pain.