From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 50615C4360C for ; Wed, 16 Oct 2019 09:36:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 297AA21848 for ; Wed, 16 Oct 2019 09:36:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571218580; bh=7iGCiUA8DsfOeZRBbJH2/3JPK3rNLE9Zn4bSFVsNXXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=A0wiiOIGDW8qsMKRjoLomN1cs1UjGSHAdXRD2C9KR6NOk8OulMwVRGLYCuPzo/bVa Oq64Y5bd3XvM4lD+yR58PdeS7ik4Arh8qePRbgyGW3+JT0tsrkMW4b8cy+k3zVmxN0 16K2sbB3Z5UQbHOCK1voueDl6p/4rdh+qKyfpHrU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404243AbfJPJgT (ORCPT ); Wed, 16 Oct 2019 05:36:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:53460 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387686AbfJPJgS (ORCPT ); Wed, 16 Oct 2019 05:36:18 -0400 Received: from linux-8ccs (unknown [95.90.219.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 010D721835; Wed, 16 Oct 2019 09:36:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1571218577; bh=7iGCiUA8DsfOeZRBbJH2/3JPK3rNLE9Zn4bSFVsNXXE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YC57lJR5lzAVNAZ6I1Z2q+ON/NxPLsKhs4WjZNnYHdNb2N+QNNVHpa2OKvnUSskf7 tEhlUERt0wVM9V+k1cKFZwNmyZ1b3PZanQ75nJb5OjXFxgBRAgUGJ/wBbgn/hldKDz eI+og3oTyU1gvPW6uyUJbeiWv+j8IhGesPBPmn18= Date: Wed, 16 Oct 2019 11:36:10 +0200 From: Jessica Yu To: Peter Zijlstra Cc: Miroslav Benes , Joe Lawrence , Steven Rostedt , x86@kernel.org, linux-kernel@vger.kernel.org, mhiramat@kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, mingo@kernel.org, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, live-patching@vger.kernel.org Subject: Re: [PATCH v3 5/6] x86/ftrace: Use text_poke() Message-ID: <20191016093610.GA9193@linux-8ccs> References: <20191010140513.GT2311@hirez.programming.kicks-ass.net> <20191010115449.22044b53@gandalf.local.home> <20191010172819.GS2328@hirez.programming.kicks-ass.net> <20191011125903.GN2359@hirez.programming.kicks-ass.net> <20191015130739.GA23565@linux-8ccs> <20191015135634.GK2328@hirez.programming.kicks-ass.net> <88bab814-ea24-ece9-2bc0-7a1e10a62f12@redhat.com> <20191016092304.GL2294@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20191016092304.GL2294@hirez.programming.kicks-ass.net> X-OS: Linux linux-8ccs 4.12.14-lp150.12.28-default x86_64 User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +++ Peter Zijlstra [16/10/19 11:23 +0200]: >On Wed, Oct 16, 2019 at 08:51:27AM +0200, Miroslav Benes wrote: >> On Tue, 15 Oct 2019, Joe Lawrence wrote: >> >> > On 10/15/19 10:13 AM, Miroslav Benes wrote: >> > > Yes, it does. klp_module_coming() calls module_disable_ro() on all >> > > patching modules which patch the coming module in order to call >> > > apply_relocate_add(). New (patching) code for a module can be relocated >> > > only when the relevant module is loaded. >> > >> > FWIW, would the LPC blue-sky2 model (ie, Steve's suggestion @ plumber's where >> > livepatches only patch a single object and updates are kept on disk to handle >> > coming module updates as they are loaded) eliminate those outstanding >> > relocations and the need to perform this late permission flipping? >> >> Yes, it should, but we don't have to wait for it. PeterZ proposed a >> different solution to this specific issue in >> https://lore.kernel.org/lkml/20191015141111.GP2359@hirez.programming.kicks-ass.net/ >> >> It should not be a problem to create a live patch module like that and the >> code in kernel/livepatch/ is almost ready. Something like >> module_section_disable_ro(mod, section) (and similar for X protection) >> should be enough. Module reloads would still require juggling with the >> protections, but I think it is all feasible. > >Just had a browse around the module code, and while the section info is >in load_info, it doesn't get retained for active modules. > >So I suppose I'll go add that for KLP enabled things. Elf section info does get saved for livepatch modules though, see mod->klp_info. And wouldn't this only be needed for livepatch modules?