Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932294AbcDDRyk (ORCPT ); Mon, 4 Apr 2016 13:54:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48767 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754398AbcDDRyj (ORCPT ); Mon, 4 Apr 2016 13:54:39 -0400 Date: Mon, 4 Apr 2016 12:54:37 -0500 From: Josh Poimboeuf To: Miroslav Benes Cc: Jiri Kosina , Jessica Yu , linux-kernel@vger.kernel.org, live-patching@vger.kernel.org, Vojtech Pavlik Subject: Re: [RFC PATCH v1.9 07/14] x86/stacktrace: add function for detecting reliable stack traces Message-ID: <20160404175437.gjj2ghphzv5foh4j@treble.redhat.com> References: <1f8c648ed8b8eb49a75f5a6cacf8b7ca76f44fa9.1458933243.git.jpoimboe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1234 Lines: 31 On Thu, Mar 31, 2016 at 03:03:16PM +0200, Miroslav Benes wrote: > On Fri, 25 Mar 2016, Josh Poimboeuf wrote: > > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > > index 2dc18605..76274b8 100644 > > --- a/arch/x86/Kconfig > > +++ b/arch/x86/Kconfig > > @@ -138,6 +138,7 @@ config X86 > > select HAVE_PERF_REGS > > select HAVE_PERF_USER_STACK_DUMP > > select HAVE_REGS_AND_STACK_ACCESS_API > > + select HAVE_RELIABLE_STACKTRACE if X86_64 && FRAME_POINTER > > I understand we have to rely on frame pointer for now. Do you plan to > switch to dwarf unwinder one day in the future? IOW is there a plan to > implement dwarf stuff generation in objtool and then to have a dwarf-based > stack unwinder upstream and to use it for live patching? Yes, adding DWARF validation and generation to objtool and creating a DWARF unwinder upstream are all planned, hopefully soon. > We have FRAME_POINTER unset in SLES for performance reasons (there was > some 5 percent slowdown measured in the past. However we should redo the > experiments.) and one day we'd really like to switch to upstream from > kgraft :). So I'm just asking. If you redo the experiments and have some useful data to share, please do share :-) -- Josh