Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030932AbbD1OJE (ORCPT ); Tue, 28 Apr 2015 10:09:04 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:44230 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030210AbbD1OI4 (ORCPT ); Tue, 28 Apr 2015 10:08:56 -0400 Date: Tue, 28 Apr 2015 16:08:42 +0200 From: Peter Zijlstra To: Josh Poimboeuf Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Michal Marek , x86@kernel.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] x86, stackvalidate: Compile-time stack frame pointer validation Message-ID: <20150428140842.GC23123@twins.programming.kicks-ass.net> References: <0c54981fcba75d6a32ad4074786b99bbf0fc0810.1430142416.git.jpoimboe@redhat.com> <20150428121606.GX23123@twins.programming.kicks-ass.net> <20150428140454.GA17315@treble.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150428140454.GA17315@treble.redhat.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1474 Lines: 27 On Tue, Apr 28, 2015 at 09:04:54AM -0500, Josh Poimboeuf wrote: > On Tue, Apr 28, 2015 at 02:16:06PM +0200, Peter Zijlstra wrote: > > On Mon, Apr 27, 2015 at 08:56:27AM -0500, Josh Poimboeuf wrote: > > > Frame pointer based stack traces aren't always reliable. One big reason > > > is that most asm functions don't set up the frame pointer. > > > > > > Fix that by enforcing that all asm functions honor CONFIG_FRAME_POINTER. > > > This is done with a new stackvalidate host tool which is automatically > > > run for every compiled .S file and which validates that every asm > > > function does the proper frame pointer setup. > > > > Would it make sense (maybe as an additional CONFIG_*_DEBUG thing) to > > also process the output of GCC with this tool? To both double check GCC > > and to give the tool more input? > > I tried that, but I discovered that gcc's usage of frame pointers would > be a lot harder to validate. It only sets up the frame pointer in code > paths which have call instructions. There are a lot of functions which > have conditional jumps at the beginning which can jump straight to a > return instruction without first doing the frame pointer setup. Hmm, would not such code break your patching? -- 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/