From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934881AbeEJKOO (ORCPT ); Thu, 10 May 2018 06:14:14 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:48636 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934263AbeEJKOL (ORCPT ); Thu, 10 May 2018 06:14:11 -0400 Date: Thu, 10 May 2018 12:14:06 +0200 From: Peter Zijlstra To: Alexey Budankov Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Andi Kleen , linux-kernel , linux-perf-users@vger.kernel.org, Andy Lutomirski Subject: Re: [PATCH v2]: perf/x86: store user space frame-pointer value on a sample Message-ID: <20180510101406.GA12217@hirez.programming.kicks-ass.net> References: <31205dc8-b756-e12b-0249-2ed06c2db9c9@linux.intel.com> <20180509145436.GV12217@hirez.programming.kicks-ass.net> <3ecedd91-1c01-6fc5-4648-89eaf5ff0930@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ecedd91-1c01-6fc5-4648-89eaf5ff0930@linux.intel.com> User-Agent: Mutt/1.9.5 (2018-04-13) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 10, 2018 at 12:42:38PM +0300, Alexey Budankov wrote: > > The Changelog needs to state that user_regs->bp is in fact valid and > > That actually was tested on binaries compiled without and with BP exposed > and in the latter case proved the value of that change. Mostly works is not the same as 'always initialized', if there are entry paths that do not store that register, then using the value might leak values from the kernel stack, which would be bad. But like said, I think much of the kernel entry code was sanitized with the PTI effort and I suspect things are in fact fine now, but lets wait for Andy to confirm.