Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765895Ab3DEBJd (ORCPT ); Thu, 4 Apr 2013 21:09:33 -0400 Received: from terminus.zytor.com ([198.137.202.10]:59606 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765881Ab3DEBJc (ORCPT ); Thu, 4 Apr 2013 21:09:32 -0400 Message-ID: <515E2425.6080601@zytor.com> Date: Thu, 04 Apr 2013 18:08:53 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130311 Thunderbird/17.0.4 MIME-Version: 1.0 To: Eric Northup CC: Kees Cook , Linux Kernel Mailing List , kernel-hardening@lists.openwall.com, Thomas Gleixner , Ingo Molnar , the arch/x86 maintainers , Jarkko Sakkinen , Matthew Garrett , Matt Fleming , Dan Rosenberg , Julien Tinnes , Will Drewry Subject: Re: [PATCH 3/3] x86: kernel base offset ASLR References: <1365106055-22939-1-git-send-email-keescook@chromium.org> <1365106055-22939-4-git-send-email-keescook@chromium.org> <515DE0C9.3030709@zytor.com> In-Reply-To: X-Enigmail-Version: 1.5.1 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: 1376 Lines: 37 On 04/04/2013 01:47 PM, Eric Northup wrote: >> >> 1. actually compose the kernel of multiple independently relocatable >> pieces (maybe chunk it on 2M boundaries or something.) > > Without increasing the entropy bits, does this actually increase the # > of tries necessary for an attacker to guess correctly? It > dramatically increases the number of possible configurations of kernel > address space, but for any given piece there are only 256 possible > locations. > The 2M chunk was a red herring; one would of course effectively pack blocks together, probably packed back to back, in random order. >> 2. compile the kernel as one of the memory models which can be executed >> anywhere in the 64-bit address space. The cost of this would have >> to be quantified, of course. > > I attempted to do this, but was limited by my knowledge of the > toolchain. I would welcome help or suggestions! Start by looking at the ABI document. I suspect what we need is some variant of the small PIC model. -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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/