From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752301AbdETRTW (ORCPT ); Sat, 20 May 2017 13:19:22 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44756 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750732AbdETRTT (ORCPT ); Sat, 20 May 2017 13:19:19 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 583A8C057FAB Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx08.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jpoimboe@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 583A8C057FAB Date: Sat, 20 May 2017 12:19:17 -0500 From: Josh Poimboeuf To: Andy Lutomirski Cc: "H. J. Lu" , "H. Peter Anvin" , "linux-kernel@vger.kernel.org" , Jiri Slaby , Andrew Morton , live-patching@vger.kernel.org, Thomas Gleixner , Ingo Molnar , the arch/x86 maintainers , Jiri Kosina , Linus Torvalds Subject: Re: [PATCH 7/7] DWARF: add the config option Message-ID: <20170520171917.6vru6sohd2wvotw3@treble> References: <20170505122200.31436-1-jslaby@suse.cz> <20170505122200.31436-7-jslaby@suse.cz> <20170507165524.cdxfuwbd5alr7v6k@treble> <20170519205354.caeyqri2k6gvso3w@treble> <8dbbb971-fc41-fba2-f356-931a7eabe6ef@zytor.com> <20170519212913.otir6mlujoxoy3ha@treble> <20170519213556.pv5kxocfprfkloay@treble> <20170520162034.fcciinh3nw5mvad5@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170520162034.fcciinh3nw5mvad5@treble> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Sat, 20 May 2017 17:19:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, May 20, 2017 at 11:20:34AM -0500, Josh Poimboeuf wrote: > But then, if we're going that far, why not just have objtool reformat > the data into something much simpler? It already has the knowledge > to do so. Then we don't have to jump through all those hoops to > justify jumping through more hoops in the kernel (i.e., having a > complex DWARF state machine). With a simple debuginfo format, the > kernel unwinder is simple enough that we don't need to validate its > functionality in a simulator. I should clarify that it doesn't have to be objtool which does this. It could instead be a simple DWARF-to-undwarf conversion tool which runs during the vmlinux linking stage. Anyway we're both proposing simplifying the DWARF data into an easier-to-parse format. I think the question is whether we want that simplification process to happen in the kernel (in the middle of a kernel unwind operation), or at build time. -- Josh