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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 DAF43C4360C for ; Wed, 16 Oct 2019 09:52:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B0A6B21848 for ; Wed, 16 Oct 2019 09:52:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="1Kf0nQX7" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387981AbfJPJwK (ORCPT ); Wed, 16 Oct 2019 05:52:10 -0400 Received: from merlin.infradead.org ([205.233.59.134]:43562 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729546AbfJPJwK (ORCPT ); Wed, 16 Oct 2019 05:52:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=5qozCDX/yJndEZNii2UlhEPMWacdmgMjo8HEhdGpong=; b=1Kf0nQX7fyNljQyjC3ZCNXLSD Hedmdolv5CFm5kDAVzBez2GZ6wEaWdDPjifRGNfz3dYlaQHo+QwWaQvJnhCws8FdEETI8T6tDoGoc BzA/Kpg2toHbl7FGrV+4rfhWnsF1dpPgsJzPPNsrQJA7LHOO6cn6hF5IMnbhOncxz3RBAcAT/Lq4w tp3Yd7ff7ljsBH6XBp4cMS6cbcGHFQ2830IxJMSCSCJD645tJpA5vded9fkRduCrFXgmAlIVyVv/g 4EUPQ5XVY5aNfsMFWghuV/TURbrjQJ1GnS2o76347wHKtGUb9AGT8yG0SU58RCh0ENuQaoCCbjvnl xLATuYPTw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iKfy6-0005CP-GV; Wed, 16 Oct 2019 09:51:46 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 5483D305FCB; Wed, 16 Oct 2019 11:50:48 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 2DD9B2995106C; Wed, 16 Oct 2019 11:51:43 +0200 (CEST) Date: Wed, 16 Oct 2019 11:51:43 +0200 From: Peter Zijlstra To: Jessica Yu 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: <20191016095143.GA3818@hirez.programming.kicks-ass.net> References: <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> <20191016093610.GA9193@linux-8ccs> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191016093610.GA9193@linux-8ccs> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Wed, Oct 16, 2019 at 11:36:10AM +0200, Jessica Yu wrote: > +++ 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? Right, I just found that, but it is x86 only for some mysterious reason. And yes, it's KLP only. I was thikning of adding a KLP only list of {name,addr,size} sections that start with ".klp" in layout_sections(). Would that not work across architectures?