From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753109Ab2LQPWg (ORCPT ); Mon, 17 Dec 2012 10:22:36 -0500 Received: from terminus.zytor.com ([198.137.202.10]:46997 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751822Ab2LQPWf (ORCPT ); Mon, 17 Dec 2012 10:22:35 -0500 User-Agent: K-9 Mail for Android In-Reply-To: <50CEE06B.9040508@parallels.com> 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> <50CEE06B.9040508@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Subject: Re: [CRIU] [PATCH] Add VDSO time function support for x86 32-bit kernel From: "H. Peter Anvin" Date: Mon, 17 Dec 2012 07:21:45 -0800 To: Pavel Emelyanov , Andy Lutomirski CC: 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 Message-ID: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Because it is almost impossible to do right? Pavel Emelyanov wrote: >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 -- Sent from my mobile phone. Please excuse brevity and lack of formatting.