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 CDE4DC2BB55 for ; Fri, 17 Apr 2020 08:27:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A8AA9207FC for ; Fri, 17 Apr 2020 08:27:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729712AbgDQI1H (ORCPT ); Fri, 17 Apr 2020 04:27:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:47780 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729166AbgDQI1H (ORCPT ); Fri, 17 Apr 2020 04:27:07 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id D2ABFACCA; Fri, 17 Apr 2020 08:27:04 +0000 (UTC) Date: Fri, 17 Apr 2020 10:27:04 +0200 (CEST) From: Miroslav Benes To: Josh Poimboeuf cc: Jessica Yu , Peter Zijlstra , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 0/7] livepatch,module: Remove .klp.arch and module_disable_ro() In-Reply-To: <20200416154514.xqqyvdtm6hjynbx2@treble> Message-ID: References: <20200414182726.GF2483@worktop.programming.kicks-ass.net> <20200414190814.glra2gceqgy34iyx@treble> <20200415142415.GH20730@hirez.programming.kicks-ass.net> <20200415161706.3tw5o4se2cakxmql@treble> <20200416153131.GC6164@linux-8ccs.fritz.box> <20200416154514.xqqyvdtm6hjynbx2@treble> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On Thu, 16 Apr 2020, Josh Poimboeuf wrote: > On Thu, Apr 16, 2020 at 05:31:31PM +0200, Jessica Yu wrote: > > > But I still not a fan of the fact that COMING has two different > > > "states". For example, after your patch, when apply_relocate_add() is > > > called from klp_module_coming(), it can use memcpy(), but when called > > > from klp module init() it has to use text poke. But both are COMING so > > > there's no way to look at the module state to know which can be used. > > > > This is a good observation, thanks for bringing it up. I agree that we > > should strive to be consistent with what the module states mean. In my > > head, I think it is easiest to assume/establish the following meanings > > for each module state: > > > > MODULE_STATE_UNFORMED - no protections. relocations, alternatives, > > ftrace module initialization, etc. any other text modifications are > > in the process of being applied. Direct writes are permissible. > > > > MODULE_STATE_COMING - module fully formed, text modifications are > > done, protections applied, module is ready to execute init or is > > executing init. > > > > I wonder if we could enforce the meaning of these two states more > > consistently without needing to add another module state. > > > > Regarding Peter's patches, with the set_all_modules_text_*() api gone, > > and ftrace reliance on MODULE_STATE_COMING gone (I think?), is there > > anything preventing ftrace_module_init+enable from being called > > earlier (i.e., before complete_formation()) while the module is > > unformed? Then you don't have to move module_enable_ro/nx later and we > > keep the MODULE_STATE_COMING semantics. And if we're enforcing the > > above module state meanings, I would also be OK with moving jump_label > > and static_call out of the coming notifier chain and making them > > explicit calls while the module is still writable. > > > > Sorry in advance if I missed anything above, I'm still trying to wrap > > my head around which callers need what module state and what module > > permissions :/ > > Sounds reasonable to me... > > BTW, instead of hard-coding the jump-label/static-call/ftrace calls, we > could instead call notifiers with MODULE_STATE_UNFORMED. That was exactly what I was thinking about too while reading Jessica's email. Since (hopefully all if I remember correctly. I checked only random subset now) existing module notifiers check module state, it should not be a problem. Miroslav