From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755140Ab3KKUEj (ORCPT ); Mon, 11 Nov 2013 15:04:39 -0500 Received: from terminus.zytor.com ([198.137.202.10]:48262 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754074Ab3KKUEb (ORCPT ); Mon, 11 Nov 2013 15:04:31 -0500 Message-ID: <52813842.40709@zytor.com> Date: Mon, 11 Nov 2013 12:04:18 -0800 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Ingo Molnar CC: Kees Cook , LKML , Thomas Gleixner , "H. Peter Anvin" , "linux-tip-commits@vger.kernel.org" Subject: Re: [tip:x86/kaslr] x86, kaslr: Provide randomness functions References: <1381450698-28710-4-git-send-email-keescook@chromium.org> <20131111182046.GA14961@gmail.com> <52812F92.1020006@zytor.com> <52813334.2040405@zytor.com> <20131111195852.GA17408@gmail.com> In-Reply-To: <20131111195852.GA17408@gmail.com> X-Enigmail-Version: 1.6 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 On 11/11/2013 11:58 AM, Ingo Molnar wrote: >> >> Use the i8254 if and only if nothing else is available, it isn't safe to >> touch on some newer systems. > > I concur - the i8254 is probably also a low entry source, given that this > all runs early bootup. > Well, it is a 16-bit 1.19318 MHz counter so at least on older systems it is likely to provide at least a modicum on entropy. On systems with a TSC it is likely to be redundant with the TSC. > In any case there's no excuse for not mixing RDRAND and RDTSC entropy. -hpa