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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 BE6E6ECE599 for ; Wed, 16 Oct 2019 06:51:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A22762067D for ; Wed, 16 Oct 2019 06:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389026AbfJPGvb (ORCPT ); Wed, 16 Oct 2019 02:51:31 -0400 Received: from mx2.suse.de ([195.135.220.15]:35846 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388363AbfJPGvb (ORCPT ); Wed, 16 Oct 2019 02:51:31 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 2435DB715; Wed, 16 Oct 2019 06:51:29 +0000 (UTC) Date: Wed, 16 Oct 2019 08:51:27 +0200 (CEST) From: Miroslav Benes To: Joe Lawrence cc: Peter Zijlstra , Jessica Yu , 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() In-Reply-To: <88bab814-ea24-ece9-2bc0-7a1e10a62f12@redhat.com> Message-ID: References: <20191007081945.10951536.8@infradead.org> <20191008104335.6fcd78c9@gandalf.local.home> <20191009224135.2dcf7767@oasis.local.home> <20191010092054.GR2311@hirez.programming.kicks-ass.net> <20191010091956.48fbcf42@gandalf.local.home> <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> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Miroslav