From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756914Ab0CDRIK (ORCPT ); Thu, 4 Mar 2010 12:08:10 -0500 Received: from fallback.mail.elte.hu ([157.181.151.13]:56392 "EHLO fallback.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756356Ab0CDRIF (ORCPT ); Thu, 4 Mar 2010 12:08:05 -0500 Date: Thu, 4 Mar 2010 12:04:29 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Frederic Weisbecker , linux-kernel@vger.kernel.org, paulus@samba.org, eranian@google.com, robert.richter@amd.com Subject: Re: [RFC][PATCH 07/11] perf: Provide PERF_SAMPLE_REGS Message-ID: <20100304110429.GC21977@elte.hu> References: <20100303163936.906011640@chello.nl> <20100303164306.375353163@chello.nl> <20100303220249.GF5194@nowhere> <1267693087.25158.148.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1267693087.25158.148.camel@laptop> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.2.5 _SUMMARY_ Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Wed, 2010-03-03 at 23:02 +0100, Frederic Weisbecker wrote: > > On Wed, Mar 03, 2010 at 05:39:43PM +0100, Peter Zijlstra wrote: > > > Simply copy out the provided pt_regs in a u64 aligned fashion. > > > > > > XXX: do task_pt_regs() and get_irq_regs() always clear everything or > > > are we now leaking data? > > > > > > It looks like there is a leak in case of non trace syscalls. > > where we don't appear to save r12-15. > > > > Then task_pt_regs() may leak the top of a process stack...? > > Right, I was afraid of that. I've put this PERF_SAMPLE_REGS thing in the > freezer for now as people seem unsure how to deal with it. Also, we dont want to expose PEBS nor LBR on an ABI level without there being a user-space component making good use of it. For example tools/perf/ support would qualify. Raw libraries alone dont really count as they generally lag plus there's no guarantee for a full feedback loop either. Adding ABI details is always a tricky business and we only want to do it if there's direct, immediate, close involvement with the user-space side, and real, immediate benefits to users. Thanks, Ingo