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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 CF9EBC433E0 for ; Wed, 22 Jul 2020 17:03:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AAC20206F5 for ; Wed, 22 Jul 2020 17:03:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ALIKBDfs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729866AbgGVRDJ (ORCPT ); Wed, 22 Jul 2020 13:03:09 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:40554 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726666AbgGVRDJ (ORCPT ); Wed, 22 Jul 2020 13:03:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1595437387; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=rNxAC2081w6KkDSHTZofG7jYDLRJsJOKNUQR0/igp1I=; b=ALIKBDfsvDxoH5zu0hVo39m/t08eIebmpgAxHLw7Uns570kyWUw9yIxgXJNRRVaVEKZ1g5 kvqktIjETNJAiQSgAY4X/V0F59Jyk6y71+NKFAjCoc+ZvrmCKn/LQMWFeUruOnPyGDa903 fVGCKTVirGgoYrJJ7I9g28sDVYkGFaw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-506-UlCdbfnNNT6NNRdnZGjhwA-1; Wed, 22 Jul 2020 13:03:05 -0400 X-MC-Unique: UlCdbfnNNT6NNRdnZGjhwA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C422181EDEE; Wed, 22 Jul 2020 17:03:04 +0000 (UTC) Received: from [10.10.114.255] (ovpn-114-255.rdu2.redhat.com [10.10.114.255]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 611221017E28; Wed, 22 Jul 2020 17:03:04 +0000 (UTC) From: Joe Lawrence Subject: Re: [PATCH 1/2] docs/livepatch: Add new compiler considerations doc To: Josh Poimboeuf Cc: live-patching@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200721161407.26806-1-joe.lawrence@redhat.com> <20200721161407.26806-2-joe.lawrence@redhat.com> <20200721230442.5v6ah7bpjx4puqva@treble> Message-ID: Date: Wed, 22 Jul 2020 13:03:03 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200721230442.5v6ah7bpjx4puqva@treble> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: live-patching-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: live-patching@vger.kernel.org On 7/21/20 7:04 PM, Josh Poimboeuf wrote: > On Tue, Jul 21, 2020 at 12:14:06PM -0400, Joe Lawrence wrote: >> Compiler optimizations can have serious implications on livepatching. >> Create a document that outlines common optimization patterns and safe >> ways to livepatch them. >> >> Signed-off-by: Joe Lawrence > > There's a lot of good info here, but I wonder if it should be > reorganized a bit and instead called "how to create a livepatch module", > because that's really the point of it all. > That would be nice. Would you consider a stand-alone compiler-optimizations doc an incremental step towards that end? Note that the other files (callbacks, shadow-vars, system-state) in their current form might be as confusing to the newbie. > I'm thinking a newcomer reading this might be lost. It's not > necessarily clear that there are currently two completely different > approaches to creating a livepatch module, each with their own quirks > and benefits/drawbacks. There is one mention of a "source-based > livepatch author" but no explanation of what that means. > Yes, the initial draft was light on source-based patching since I only really tinker with it for samples/kselftests. The doc was the result of an experienced livepatch developer and Sunday afternoon w/the compiler. I'm sure it reads as such. :) > Maybe it could begin with an overview of the two approaches, and then > delve more into the details of each approach, and then delve even more > into the gory details about compiler optimizations. > Up until now, the livepatch documentation has danced around the particular creation method and only described the API in abstract. If a compiler considerations doc needs to have that complete context then I'd suggest we reorganize the entire lot as a prerequisite. > Also the kpatch-build section can reference the patch author guide which > we have on github. > Good point. I think there are a few kpatch-specific implications (sibling call changes maybe) to consider. -- Joe