From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexey Budankov Subject: Re: [PATCH v2]: perf/x86: store user space frame-pointer value on a sample Date: Thu, 10 May 2018 13:29:28 +0300 Message-ID: <6be7739b-8c6c-bbd8-6866-a26d8d25266d@linux.intel.com> References: <31205dc8-b756-e12b-0249-2ed06c2db9c9@linux.intel.com> <20180509145436.GV12217@hirez.programming.kicks-ass.net> <3ecedd91-1c01-6fc5-4648-89eaf5ff0930@linux.intel.com> <20180510101406.GA12217@hirez.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180510101406.GA12217@hirez.programming.kicks-ass.net> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Peter Zijlstra 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 List-Id: linux-perf-users.vger.kernel.org Hi, On 10.05.2018 13:14, Peter Zijlstra wrote: > 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. Yep, absolutely agree. Extra care needs to be taken here. > > 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. > Thanks, Alexey