Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752511AbbLIRFK (ORCPT ); Wed, 9 Dec 2015 12:05:10 -0500 Received: from www.sr71.net ([198.145.64.142]:34492 "EHLO blackbird.sr71.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752338AbbLIRFI (ORCPT ); Wed, 9 Dec 2015 12:05:08 -0500 Subject: Re: [PATCH 26/34] mm: implement new mprotect_key() system call To: mtk.manpages@gmail.com References: <20151204011424.8A36E365@viggo.jf.intel.com> <20151204011500.69487A6C@viggo.jf.intel.com> <5662894B.7090903@gmail.com> <5665B767.8020802@sr71.net> <56680BA6.20406@gmail.com> <56684D3B.5050805@sr71.net> Cc: lkml , "linux-mm@kvack.org" , "x86@kernel.org" , dave.hansen@linux.intel.com, Linux API From: Dave Hansen Message-ID: <56685F42.8070109@sr71.net> Date: Wed, 9 Dec 2015 09:05:06 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1101 Lines: 26 On 12/09/2015 08:45 AM, Michael Kerrisk (man-pages) wrote: >>> >> * Explanation of what a protection domain is. >> > >> > A protection domain is a unique view of memory and is represented by the >> > value in the PKRU register. > Out something about this in pkey(7), but explain what you mean by a > "unique view of memory". Let's say there are only two protection keys: 0 and 1. There are two disable bits per protection key (Access and Write Disable), so a two-key PKRU looks like: | PKEY0 | PKEY1 | | AD0 | WD0 | AD1 | WD1 | In this example, there are 16 possible protection domains, one for each possible combination of the 4 rights-disable bits. "Changing a protection domain" would mean changing (setting or clearing) the value of any of those 4 bits. Each unique value of PKRU represents a view of memory, or unique protection domain. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/