Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753463AbbGRDFb (ORCPT ); Fri, 17 Jul 2015 23:05:31 -0400 Received: from mail-wi0-f176.google.com ([209.85.212.176]:38570 "EHLO mail-wi0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752051AbbGRDF3 (ORCPT ); Fri, 17 Jul 2015 23:05:29 -0400 Date: Sat, 18 Jul 2015 05:05:24 +0200 From: Ingo Molnar To: Andy Lutomirski Cc: Josh Poimboeuf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , Pedro Alves , X86 ML , live-patching@vger.kernel.org, "linux-kernel@vger.kernel.org" Subject: Re: [RFC PATCH 00/21] x86: Proposed fixes for stackvalidate warnings Message-ID: <20150718030524.GC13059@gmail.com> References: <20150715101627.GA21770@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2183 Lines: 52 * Andy Lutomirski wrote: > On Fri, Jul 17, 2015 at 9:47 AM, Josh Poimboeuf wrote: > > These patches fix many of the warnings reported by stackvalidate. > > They're based on top of the "Compile-time stack validation" v7 patch set > > [1]. > > > > They've been compile-tested and boot tested in a VM, but I haven't > > attempted any meaningful testing for most of them. This should give an > > idea of what kinds of changes I think are needed. > > > > [1] https://lkml.kernel.org/r/cover.1436893563.git.jpoimboe@redhat.com > > > > Nothing here looks all that bad, but I think the extra frame pointers > staring us in the face (as opposed to the ones that gcc adds > transparently) might serve as added incentive to suck it up and get > CFI unwinding working. So there are two aspects to frame pointers staring us in the face: - Syntactically there's extra debuginfo cruft added to the source code. Not good but very fixable: I already made a couple of suggestions of how to trim all that in a way that improves general readability as well over what we have today. - Instruction wise in the generated code. I'm afraid the 'transparent' frame pointers added by GCC are staring me in the face in perf top/report disassembly output just as much! ;-) But naming details aside, I like the direction of these patches a lot better than that of any previous debuginfo approach, because the approach is very proactive. ( Which it really has to be, given that deep down these patches are motivated by enabling more complex models of live kernel patching. But that's a win-win. ) Once the cleanliness of the annotations is improved and we have a reasonable path towards having no warnings on a regular kernel build, I plan on starting to apply the patches. So if anyone has any deep objections that were kept close to the vest so far, please holler now. Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/