Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753286AbbLKUOB (ORCPT ); Fri, 11 Dec 2015 15:14:01 -0500 Received: from mail-wm0-f50.google.com ([74.125.82.50]:37373 "EHLO mail-wm0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751358AbbLKUN7 (ORCPT ); Fri, 11 Dec 2015 15:13:59 -0500 Message-ID: <566B2E83.4070002@gmail.com> Date: Fri, 11 Dec 2015 21:13:55 +0100 From: "Michael Kerrisk (man-pages)" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: Dave Hansen CC: mtk.manpages@gmail.com, lkml , "linux-mm@kvack.org" , "x86@kernel.org" , dave.hansen@linux.intel.com, Linux API Subject: Re: [PATCH 26/34] mm: implement new mprotect_key() system call 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> <56685F42.8070109@sr71.net> In-Reply-To: <56685F42.8070109@sr71.net> 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: 1519 Lines: 43 On 12/09/2015 06:05 PM, Dave Hansen wrote: > 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. Again, some of this could make its way into pkey(7). And I guess there are useful nuggets for that page to be found in Jon's article at https://lwn.net/Articles/667156/ Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/ -- 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/