Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752436AbbGNWcy (ORCPT ); Tue, 14 Jul 2015 18:32:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37292 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751146AbbGNWcx (ORCPT ); Tue, 14 Jul 2015 18:32:53 -0400 Date: Tue, 14 Jul 2015 17:32:50 -0500 From: Josh Poimboeuf To: Peter Zijlstra Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , Andy Lutomirski , Borislav Petkov , Linus Torvalds , Andi Kleen , Pedro Alves , x86@kernel.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt Subject: Re: [PATCH v7 2/4] x86/stackvalidate: Compile-time stack validation Message-ID: <20150714223250.GD13950@treble.redhat.com> References: <20150714210858.GP19282@twins.programming.kicks-ass.net> <20150714213034.GB13950@treble.redhat.com> <20150714215649.GQ19282@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20150714215649.GQ19282@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1170 Lines: 26 On Tue, Jul 14, 2015 at 11:56:49PM +0200, Peter Zijlstra wrote: > On Tue, Jul 14, 2015 at 04:30:34PM -0500, Josh Poimboeuf wrote: > > the past few years for newer versions of gcc, stackvalidate silently > > ignores __fentry__ calls and assumes that ftrace indeed knows wtf it's > > doing. I don't see a problem there as long as the ftrace handler > > doesn't sleep. > > They should not indeed, however it would be very nice if backtraces > would still be 'good'. Agreed, though I don't know if it's possible for stackvalidate to reasonably understand what ftrace is doing. I tend to doubt it, since ftrace does some code modification at runtime. It does spit out some warnings for mcount_64.S. I'll need to look at that code in more detail to figure out if the warnings should be whitelisted as false positives, or if there's some way to annotate the code to help stackvalidate understand it and validate it. -- Josh -- 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/