From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755587AbcBVUuy (ORCPT ); Mon, 22 Feb 2016 15:50:54 -0500 Received: from mga02.intel.com ([134.134.136.20]:2129 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755464AbcBVUux (ORCPT ); Mon, 22 Feb 2016 15:50:53 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.22,486,1449561600"; d="scan'208";a="921495028" Date: Mon, 22 Feb 2016 12:48:29 -0800 From: Yu-cheng Yu To: Dave Hansen Cc: x86@kernel.org, "H. Peter Anvin" , Thomas Gleixner , Ingo Molnar , linux-kernel@vger.kernel.org, Andy Lutomirski , Borislav Petkov , Sai Praneeth Prakhya , "Ravi V. Shankar" , Fenghua Yu Subject: Re: [PATCH 08/10] x86/xsaves: Fix PTRACE frames for XSAVES Message-ID: <20160222204828.GC4140@test-lenovo> References: <1456167621-3974-1-git-send-email-yu-cheng.yu@intel.com> <56CB68C2.6010003@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56CB68C2.6010003@linux.intel.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 22, 2016 at 12:00:02PM -0800, Dave Hansen wrote: > On 02/22/2016 11:00 AM, Yu-cheng Yu wrote: > > + if (xsave->header.xfeatures & XFEATURE_MASK_SUPERVISOR) > > + xsave->header.xfeatures = xfeatures | XFEATURE_MASK_SUPERVISOR; > > + else > > + xsave->header.xfeatures = xfeatures; > > This is dangerous. It says, "if any supervisor feature bit is set, then > set *ALL* of the known bits". There's no way that can work. > > Don't you just want to or in the new bits that were in the passed-in > 'xfeatures': > > xsave->header.xfeatures |= xfeatures; > > 'xfeatures' is known not to contain any supervisor bits. > It should have been: xsave->header.xfeatures = xfeatures | (xsave->header.xfeatures & XFEATURE_MASK_SUPERVISOR); I'll fix it. --Yu-cheng