From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755559Ab1FHKjo (ORCPT ); Wed, 8 Jun 2011 06:39:44 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:34505 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752955Ab1FHKjn (ORCPT ); Wed, 8 Jun 2011 06:39:43 -0400 Date: Wed, 8 Jun 2011 12:39:06 +0200 From: Ingo Molnar To: pageexec@freemail.hu Cc: Andi Kleen , Andrew Lutomirski , x86@kernel.org, Thomas Gleixner , linux-kernel@vger.kernel.org, Jesper Juhl , Borislav Petkov , Linus Torvalds , Andrew Morton , Arjan van de Ven , Jan Beulich , richard -rw- weinberger , Mikael Pettersson , Brian Gerst , Louis Rilling , Valdis.Kletnieks@vt.edu Subject: Re: [PATCH v5 8/9] x86-64: Emulate legacy vsyscalls Message-ID: <20110608103906.GB13393@elte.hu> References: <20110608091120.GI27166@one.firstfloor.org> <4DEF424F.2351.1C15AD40@pageexec.freemail.hu> <20110608100612.GJ27166@one.firstfloor.org> <4DEF4E69.14274.1C44F04F@pageexec.freemail.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4DEF4E69.14274.1C44F04F@pageexec.freemail.hu> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * pageexec@freemail.hu wrote: > On 8 Jun 2011 at 12:06, Andi Kleen wrote: > > > > eventually may even go away as time progresses and linux > > > systems begin to fully rely on the vdso instead. > > > > That assumes that everyone uses glibc and also updates their > > userland. As pointed out many times that's a deeply flawed > > assumption. > > i think the assumption is not that everyone uses glibc but that > everyone else (as in, every other libc) can simply take the > necessary changes from glibc, provided they need such changes at > all (i.e., they're using the vsyscall entry points over the vdso > ones). > > i frankly didn't check any of the alternatives myself > (uclibc/klibc/bionic/etc) but i can't imagine that it'd be that > much harder to patch them than glibc. Correct. Also, as i pointed it out in the previous mail, ABI does not mean 'will execute the same instructions', that would be silly. We *do* fix serious wide-scale performance regressions (obviously), but if it's about some weird crazy legacy path that we had good security reasons to change, and which is trivial to performance-improve in the library then we are well within our boundaries to keep the change. > as i said, this was a compromise solution but then i think you > already made it clear that you didn't even think there was a > problem here to solve, so i guess we should work that out first, if > you want to ;). Heh, indeed ;-) Thanks, Ingo