From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754767AbcGUVvH (ORCPT ); Thu, 21 Jul 2016 17:51:07 -0400 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:54918 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754531AbcGUVvF (ORCPT ); Thu, 21 Jul 2016 17:51:05 -0400 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.33 X-Original-MAILFROM: byungchul.park@lge.com Date: Fri, 22 Jul 2016 06:49:01 +0900 From: Byungchul Park To: Josh Poimboeuf Cc: Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , x86@kernel.org, linux-kernel@vger.kernel.org, Andy Lutomirski , Linus Torvalds , Steven Rostedt , Brian Gerst , Kees Cook , Peter Zijlstra , Frederic Weisbecker Subject: Re: [PATCH 15/19] x86/dumpstack: convert show_trace_log_lvl() to the new unwinder Message-ID: <20160721214901.GT2279@X58A-UD3R> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 21, 2016 at 04:21:52PM -0500, Josh Poimboeuf wrote: > Convert show_trace_log_lvl() to the new unwinder. dump_trace() has been > deprecated. > > show_trace_log_lvl() is special compared to other users of the unwinder. > It's the only place where both reliable *and* unreliable addresses are > needed. With frame pointers enabled, most stack walking code doesn't > want to know about unreliable addresses. But in this case, when we're > dumping the stack to the console because something presumably went > wrong, the unreliable addresses are useful: > > - They show stale data on the stack which can provide useful clues. > > - If something goes wrong with the unwinder, or if frame pointers are > corrupt or missing, all the stack addresses still get shown. > > So in order to show all addresses on the stack, and at the same time > figure out which addresses are reliable, we have to do the scanning and > the unwinding in parallel. > > The scanning is done with the help of get_stack_info() to traverse the > stacks. The unwinding is done separately by the new unwinder. > > In theory we could simplify show_trace_log_lvl() by instead pushing some > of this logic into the unwind code. But then we would need some kind of > "fake" frame logic in the unwinder which would add a lot of complexity > and wouldn't be worth it in order to support only one user. > > Another benefit of this approach is that once we have a DWARF unwinder, > we should be able to just plug it in with minimal impact to this code. > > Another change here is that callers of show_trace_log_lvl() don't need > to provide the 'bp' argument. The unwinder already finds the relevant > frame pointer by unwinding until it reaches the first frame after the > provided stack pointer. Hello, You seem to have changed a lot of code with which I dealt in another patch. I might be supposed to wait until yours will be done. I need to check yours at first anyway.