From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933896AbdBVUwR (ORCPT ); Wed, 22 Feb 2017 15:52:17 -0500 Received: from terminus.zytor.com ([65.50.211.136]:47122 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934655AbdBVUwG (ORCPT ); Wed, 22 Feb 2017 15:52:06 -0500 Subject: Re: v4.10: kernel stack frame pointer .. has bad value (null) To: Josh Poimboeuf References: <20170221221418.GA6918@amd> <20170221231216.y56gb62vkn5ewgea@treble> <20170222164515.zfnwysnuvce2ixdw@treble> Cc: Pavel Machek , kernel list , mingo@kernel.org, luto@kernel.org, bp@alien8.de, brgerst@gmail.com, dvlasenk@redhat.com, torvalds@linux-foundation.org, peterz@infradead.org, tglx@linutronix.de From: "H. Peter Anvin" Message-ID: Date: Wed, 22 Feb 2017 12:51:11 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: <20170222164515.zfnwysnuvce2ixdw@treble> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/22/17 08:45, Josh Poimboeuf wrote: >> >> FWIW, it would be really darned nice to not have all those zeroes in a >> 32-bit stack frame dump. > > Yeah, I'll fix that. > >> Is not a zero stack frame pointer value an end of stack token? > > There's no end of stack "token" per se, though any frame pointer value > outside the bounds of the stack will terminate the stack trace (and that > still happened here). > Well, my understanding is that at least gdb and perhaps other unwinders consider a zero stack frame pointer to be an indicator that the stack has reached its end. That's why I'm wondering if this is possible in this case or if it is unlikely because of the value. > The warning is because the stack trace didn't make it all the way to the > "end" location of the stack (right before the syscall pt_regs location). > The warning is part of the effort to ensure reliable stacks. It would be useful to get an understanding why... -hpa