From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754565AbaCKQr6 (ORCPT ); Tue, 11 Mar 2014 12:47:58 -0400 Received: from mga02.intel.com ([134.134.136.20]:38085 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752304AbaCKQr5 (ORCPT ); Tue, 11 Mar 2014 12:47:57 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,631,1389772800"; d="scan'208";a="489893307" Message-ID: <531F3D02.30706@linux.intel.com> Date: Tue, 11 Mar 2014 09:42:42 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Linus Torvalds CC: Andy Lutomirski , "linux-kernel@vger.kernel.org" , Stefani Seibold , the arch/x86 maintainers , Dave Jones , Martin Runge , Andreas Brief Subject: Re: [PATCH v2] x86: Remove compat vdso support References: <531F365B.4060000@linux.intel.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/11/2014 09:30 AM, Linus Torvalds wrote: > > No, the trivial solution is to stop adding crap to it. > > And no, "just reserve a little more space for it" is neither trivial > nor a good idea. The fixed VDSO address is very much at the top of the > address space, so you can't allocate more space for it unless you do > one of > > (a) make it non-contiguous > (b) get rid of the hole that is the very last page > (c) mess with the vsyscall pages and make it contiguous "backwards" > > all of which sound like *horrible* ideas. Certainly not "trivial solution". > > No, the trivial solution is to not mess with that legacy page at all. > > Why is *that* trivial solution not on the table? Why the heck are > people hell-bent on changing this stupid legacy page around? > > I find this whole thread very annoying. We shouldn't care about > x86-32, and certainly not from a performance angle - we should > consider it a "it's done, don't touch it" issue. > Andy actually did the research, and found that even the legacy VDSO doesn't have to live at any one particular address, it just has to live at the address it is linked at. So we can move it just fine, but we have to change the link address to match. That gives us a lot more maneuvering room than saying it has to be at one specific address. -hpa