From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753357AbbETTKV (ORCPT ); Wed, 20 May 2015 15:10:21 -0400 Received: from cantor2.suse.de ([195.135.220.15]:43006 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751962AbbETTKT (ORCPT ); Wed, 20 May 2015 15:10:19 -0400 Date: Wed, 20 May 2015 21:10:16 +0200 (CEST) From: Jiri Kosina To: Peter Zijlstra cc: Andy Lutomirski , Ingo Molnar , Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , X86 ML , live-patching@vger.kernel.org, "linux-kernel@vger.kernel.org" , Linus Torvalds , Andy Lutomirski , Denys Vlasenko , Brian Gerst , Borislav Petkov , Andrew Morton Subject: Re: [PATCH v4 0/3] Compile-time stack frame pointer validation In-Reply-To: <20150520172700.GM3644@twins.programming.kicks-ass.net> Message-ID: References: <20150520103339.GA22205@gmail.com> <20150520141331.GA16995@treble.redhat.com> <20150520144810.GA10374@gmail.com> <20150520172700.GM3644@twins.programming.kicks-ass.net> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 20 May 2015, Peter Zijlstra wrote: > > I think it would be nice to have full DWARF unwind support for > > everything at some point. Unfortunately, I don't see any easy path to > > getting there. It doesn't help that AFAIK no one has ever proposed a > > usable in-kernel DWARF unwinder. > > There's a bit of history here; SuSE (iirc) actually has one, however: > > https://lkml.org/lkml/2012/2/10/356 Oh absolutely, there are stories behind this :) Just for the sake of completness -- the current implementation can be found in our public GIT repository, for not-really-complete picture see [1] [2] [3] [4]. It turned out to be rather useful on many ocasions when debugging customer reports, but I of course also understand what Linus is saying above. The bugs in unwinder can be *really* painful. Our experience so far has been that it did pay off at the end of the day (and of course analyzing stacktraces is our daily bread). [1] http://kernel.suse.com/cgit/kernel-source/tree/patches.suse/stack-unwind?h=SLE12 [2] http://kernel.suse.com/cgit/kernel-source/tree/patches.suse/no-frame-pointer-select?h=SLE12 [3] http://kernel.suse.com/cgit/kernel-source/tree/patches.arch/stack-unwind-cfi_ignore-takes-more-arguments?h=SLE12 [4] http://kernel.suse.com/cgit/kernel-source/tree/patches.arch/x86_64-unwind-annotations?h=SLE12 -- Jiri Kosina SUSE Labs