From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755121AbbERXfY (ORCPT ); Mon, 18 May 2015 19:35:24 -0400 Received: from www.linutronix.de ([62.245.132.108]:51692 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754866AbbERXfW (ORCPT ); Mon, 18 May 2015 19:35:22 -0400 Date: Tue, 19 May 2015 01:35:31 +0200 (CEST) From: Thomas Gleixner To: Dave Hansen cc: linux-kernel@vger.kernel.org, x86@kernel.org, dave.hansen@linux.intel.com Subject: Re: [PATCH 09/19] x86, mpx: trace entry to bounds exception paths In-Reply-To: <555A7087.5080409@sr71.net> Message-ID: References: <20150508185948.4C19F4B0@viggo.jf.intel.com> <20150508185952.3D3B9085@viggo.jf.intel.com> <555A7087.5080409@sr71.net> User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 18 May 2015, Dave Hansen wrote: > On 05/18/2015 01:58 PM, Thomas Gleixner wrote: > > On Fri, 8 May 2015, Dave Hansen wrote: > >> > This patch adds a trace point for the case where we are > >> > passing the exception up to userspace with a signal. > >> > > >> > We are also explicit that we're printing out the inverse of > >> > the 'upper' that we encounter. If you want to filter, for > >> > instance, you need to ~ the value first. > > Confused. What is the point of printing the complement of upper? > > If a pointer's range is > > 0x1000 -> 0x2000 > > it is stored in the bounds table as (32-bits here for brevity): > > lower: 0x00001000 > upper: 0xffffdfff > > That is so that an all 0's entry: > > lower: 0x00000000 > upper: 0x00000000 > > corresponds to the "init" bounds which store a *range* of: > > 0x00000000 -> 0xffffffff > > The 'upper' stored in the table is gibberish to print by itself, so we > print ~upper to get the *actual*, logical value. Some comment in the code and the changelog might be helpful then :) Thanks, tglx