From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753813Ab2LQS5J (ORCPT ); Mon, 17 Dec 2012 13:57:09 -0500 Received: from mailhub.sw.ru ([195.214.232.25]:8014 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753782Ab2LQS5H (ORCPT ); Mon, 17 Dec 2012 13:57:07 -0500 Message-ID: <50CF6ACC.4090701@parallels.com> Date: Mon, 17 Dec 2012 22:56:12 +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: "H. Peter Anvin" CC: Andy Lutomirski , 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> <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> 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 12/17/2012 07:21 PM, H. Peter Anvin wrote: > Because it is almost impossible to do right? In the generic case -- I tend to agree. But it's possible to describe how a library should communicate to crtools to make it possible. Anyway, what I wanted to say -- we didn't have this scenario in our plans, but criu project is open, and if someone comes with sane idea, we will not object merging it. > 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 >