From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752012Ab2LQJGu (ORCPT ); Mon, 17 Dec 2012 04:06:50 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:47096 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751798Ab2LQJGs (ORCPT ); Mon, 17 Dec 2012 04:06:48 -0500 Message-ID: <50CEE06B.9040508@parallels.com> Date: Mon, 17 Dec 2012 13:05:47 +0400 From: Pavel Emelyanov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 MIME-Version: 1.0 To: Andy Lutomirski CC: "H. Peter Anvin" , aarcange@redhat.com, ak@linux.intel.com, Stefani Seibold , x86@kernel.org, linux-kernel@vger.kernel.org, criu@openvz.org, mingo@redhat.com, john.stultz@linaro.org, tglx@linutronix.de Subject: Re: [CRIU] [PATCH] Add VDSO time function support for x86 32-bit kernel References: <1355343572-23074-1-git-send-email-stefani@seibold.net> <50C9148C.4040308@zytor.com> <1355378005.24283.11.camel@wall-e> <1d3061cb-76d0-4e42-9b75-a975b05384ec@email.android.com> <1355379433.24701.1.camel@wall-e> <1355383038.18653.2.camel@wall-e> <50CA6E4C.6000305@zytor.com> <50CA81A4.9040702@zytor.com> <50CA85BD.7070502@zytor.com> <8c3585bc-fc7d-4826-913c-f4581494d91d@email.android.com> <50CAE485.5020608@parallels.com> <50CB716D.6020501@zytor.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/14/2012 10:44 PM, Andy Lutomirski wrote: > On Fri, Dec 14, 2012 at 10:35 AM, H. Peter Anvin wrote: >> On 12/14/2012 12:34 AM, Pavel Emelyanov wrote: >>> On 12/14/2012 06:20 AM, Andy Lutomirski wrote: >>>> On Thu, Dec 13, 2012 at 6:18 PM, H. Peter Anvin wrote: >>>>> Wouldn't the vdso get mapped already and could be mremap()'d. If we >>>> really need more control I'd almost push for a device/filesystem node >>>> that could be mmapped the usual way. >>>> >>>> Hmm. That may work, but it'll still break ABI. I'm not sure that >>>> criu is stable enough yet that we should care. Criu people? >>> >>> It's not yet, but we'd still appreciate the criu-friendly vdso redesign. >>> >>>> (In brief summary: how annoying would it be if the vdso was no longer >>>> just a bunch of constant bytes that lived somewhere?) >>> >>> It depends on what vdso is going to be. In the perfect case it should >>> a) be mremap-able to any address (or be at fixed address _forever_, but >>> I assume this is not feasible); >>> b) have entry points at fixed (or somehow movable) places. >>> >>> I admit that I didn't understand your question properly, if I did, >>> please correct me. >>> >> >> mremap() should work. At the same time, the code itself is not going to >> have any stability guarantees between kernel versions -- it obviously >> cannot. > > We could guarantee that the symbols in the vdso resolve to particular > offsets within the vdso. (Yes, this is ugly.) > > Does criu support checkpointing with one version of a shared library > and restoring with another? No, neither we have this in plans. However, if somebody needs this and implements -- why not?! Thanks, Pavel