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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 6FA8CC433E6 for ; Mon, 18 Jan 2021 17:52:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 384CC2253A for ; Mon, 18 Jan 2021 17:52:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2406081AbhARRwV (ORCPT ); Mon, 18 Jan 2021 12:52:21 -0500 Received: from foss.arm.com ([217.140.110.172]:40148 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727931AbhARRvo (ORCPT ); Mon, 18 Jan 2021 12:51:44 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8FAD631B; Mon, 18 Jan 2021 09:50:58 -0800 (PST) Received: from C02TD0UTHF1T.local (unknown [10.57.39.202]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EC8753F719; Mon, 18 Jan 2021 09:50:56 -0800 (PST) Date: Mon, 18 Jan 2021 17:50:54 +0000 From: Mark Rutland To: Petr Mladek Cc: Mark Brown , linux-kernel@vger.kernel.org, Jiri Kosina , Joe Lawrence , Jonathan Corbet , Miroslav Benes , linux-doc@vger.kernel.org, live-patching@vger.kernel.org, Josh Poimboeuf Subject: Re: [PATCH v4] Documentation: livepatch: document reliable stacktrace Message-ID: <20210118175054.GB38844@C02TD0UTHF1T.local> References: <20210115171617.47273-1-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org Hi Petr, On Mon, Jan 18, 2021 at 03:02:31PM +0100, Petr Mladek wrote: > On Fri 2021-01-15 17:16:17, Mark Brown wrote: > > I've made a few assumptions about preferred behaviour, notably: > > > > * If you can reliably unwind through exceptions, you should (as x86_64 > > does). IIRC this was confirmed as desireable, and the text already reflects this. > > * It's fine to omit ftrace_return_to_handler and other return > > trampolines so long as these are not subject to patching and the > > original return address is reported. Most architectures do this for > > ftrace_return_handler, but not other return trampolines. Likewise I think we agreed this was fine, given these were not themselves subkect to patching. > > * For cases where link register unreliability could result in duplicate > > entries in the trace or an inverted trace, I've assumed this should be > > treated as unreliable. This specific case shouldn't matter to > > livepatching, but I assume that that we want a reliable trace to have > > the correct order. I don't think we had any comments either way on this, but I think it's sane to say this for now and later relax it if we need to. ... so I reckon we can just delete all this as Josh suggests. Any acks for the patch itself tacitly agrees with these points. :) Thanks, Mark.