From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751768AbdCCO3j (ORCPT ); Fri, 3 Mar 2017 09:29:39 -0500 Received: from mx2.suse.de ([195.135.220.15]:55434 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751415AbdCCO3X (ORCPT ); Fri, 3 Mar 2017 09:29:23 -0500 Date: Fri, 3 Mar 2017 15:28:30 +0100 From: Borislav Petkov To: Baoquan He Cc: tglx@linutronix.de, hpa@zytor.com, mingo@redhat.com, linux-kernel@vger.kernel.org, x86@kernel.org, keescook@chromium.org, yinghai@kernel.org, anderson@redhat.com, luto@kernel.org, thgarnie@google.com, kuleshovmail@gmail.com Subject: Re: [PATCH v4 1/3] x86: Introduce a new constant KERNEL_MAPPING_SIZE Message-ID: <20170303142830.pkkvn2iz7dwceei6@pd.tnic> References: <1486040077-3719-1-git-send-email-bhe@redhat.com> <1486040077-3719-2-git-send-email-bhe@redhat.com> <20170214173217.3qtf6fhiklhgsmi5@pd.tnic> <20170226040908.GB14810@x1> <20170303114349.krl6s5qfjmwz3mrg@pd.tnic> <20170303120616.GE18391@x1> <20170303121614.7cgyb6gfhtgmcide@pd.tnic> <20170303125213.GF18391@x1> <20170303131152.GG18391@x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20170303131152.GG18391@x1> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 03, 2017 at 09:11:52PM +0800, Baoquan He wrote: > And another meaning of defining kernel iamge size and mapping size > differently is we can randomize the limited kernel image in the mapping > area. If they are the same or kernel image can be very large, the > position will be fixed or very few, kernel text KASLR will be > meaningless. This is simply not true: @@ -408,9 +408,9 @@ static unsigned long find_random_virt_addr(unsigned long minimum, /* * There are how many CONFIG_PHYSICAL_ALIGN-sized slots * that can hold image_size within the range of minimum to - * KERNEL_IMAGE_SIZE? + * KERNEL_MAPPING_SIZE? */ - slots = (KERNEL_IMAGE_SIZE - minimum - image_size) / + slots = (KERNEL_MAPPING_SIZE - minimum - image_size) / CONFIG_PHYSICAL_ALIGN + 1; *With* kaslr, KERNEL_IMAGE_SIZE = 1G and KERNEL_MAPPING_SIZE = 1G. Before your patch KERNEL_IMAGE_SIZE = 1G too with kaslr enabled. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --