From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751950AbXCEWBq (ORCPT ); Mon, 5 Mar 2007 17:01:46 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751956AbXCEWBq (ORCPT ); Mon, 5 Mar 2007 17:01:46 -0500 Received: from gw.goop.org ([64.81.55.164]:47699 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751950AbXCEWBp (ORCPT ); Mon, 5 Mar 2007 17:01:45 -0500 Message-ID: <45EC9347.9030009@goop.org> Date: Mon, 05 Mar 2007 14:01:43 -0800 From: Jeremy Fitzhardinge User-Agent: Thunderbird 1.5.0.9 (X11/20070212) MIME-Version: 1.0 To: Roland McGrath CC: Andi Kleen , Ingo Molnar , Andrew Morton , linux-kernel@vger.kernel.org, Rusty Russell , Jan Beulich Subject: Re: [patch] paravirt: VDSO page is essential References: <20070305215838.051CD1800E5@magilla.sf.frob.com> In-Reply-To: <20070305215838.051CD1800E5@magilla.sf.frob.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Roland McGrath wrote: > Does the old userland compatibility you're concerned about really need the > vdso to be at 0xfffffe000 in particular, or just need it to be at a fixed > address that matches the phdrs inside the image? My recollection of the old > glibc's limitation was that it expected the image's phdrs to match its load > address. The xen kernels used to change this to 0xffffd000 or something, > and AFAIK that was fine. If that's all that's needed, it is not so hard to > adjust the vDSO contents at boot time (phdrs, shdrs, and symbols; no code > contents use the absolute address). Under CONFIG_COMPAT_VDSO, it can see > where the paravirt moved the fixmap to, and apply adjustments. > Jan Beulich just posted a patch to do just this - relocate the vdso's ELF header. If that's all that's really required to keep COMPAT_VDSO viable under PARAVIRT, then it seems like the way to go. J