From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id E269F6B0038 for ; Wed, 7 Oct 2015 16:24:06 -0400 (EDT) Received: by padhy16 with SMTP id hy16so30837869pad.1 for ; Wed, 07 Oct 2015 13:24:06 -0700 (PDT) Received: from blackbird.sr71.net ([2001:19d0:2:6:209:6bff:fe9a:902]) by mx.google.com with ESMTP id fn8si60273077pad.50.2015.10.07.13.24.02 for ; Wed, 07 Oct 2015 13:24:02 -0700 (PDT) Subject: Re: [PATCH 26/26] x86, pkeys: Documentation References: <20150916174903.E112E464@viggo.jf.intel.com> <20150916174913.AF5FEA6D@viggo.jf.intel.com> <20150920085554.GA21906@gmail.com> <55FF88BA.6080006@sr71.net> <20150924094956.GA30349@gmail.com> <20151003081710.GA26206@gmail.com> From: Dave Hansen Message-ID: <56157F60.1000503@sr71.net> Date: Wed, 7 Oct 2015 13:24:00 -0700 MIME-Version: 1.0 In-Reply-To: <20151003081710.GA26206@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Ingo Molnar Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Linus Torvalds , Andrew Morton , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Kees Cook , Brian Gerst On 10/03/2015 01:17 AM, Ingo Molnar wrote: > Right now the native x86 PTE format allows two protection related bits for > user-space pages: > > _PAGE_BIT_RW: if 0 the page is read-only, if 1 then it's read-write > _PAGE_BIT_NX: if 0 the page is executable, if 1 then it's not executable > > As discussed previously, pkeys allows 'true execute only (--x)' mappings. > > Another possibility would be 'true write-only (-w-)' mappings. How would those work? Protection Keys has a Write-Disable and an Access-Disable bit. But, Access-Disable denies _all_ data access to the region. There's no way to allow only writes. Or am I missing something? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org