From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753705AbbAUEsm (ORCPT ); Tue, 20 Jan 2015 23:48:42 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45477 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751581AbbAUEsl (ORCPT ); Tue, 20 Jan 2015 23:48:41 -0500 Date: Wed, 21 Jan 2015 12:46:44 +0800 From: Baoquan He To: Andy Lutomirski Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, x86@kernel.org, keescook@chromium.org, vgoyal@redhat.com, whissi@whissi.de Subject: Re: [PATCH 0/6] randomize kernel physical address and virtual address separately Message-ID: <20150121044644.GH2461@dhcp-16-105.nay.redhat.com> References: <1421811437-2787-1-git-send-email-bhe@redhat.com> <54BF28D8.70107@amacapital.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <54BF28D8.70107@amacapital.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/20/15 at 08:19pm, Andy Lutomirski wrote: > On 01/20/2015 07:37 PM, Baoquan He wrote: > > Currently kaslr only randomize physical address of kernel loading, then add the delta > > to virtual address of kernel text mapping. Because kernel virtual address can only be > > from __START_KERNEL_map to LOAD_PHYSICAL_ADDR+CONFIG_RANDOMIZE_BASE_MAX_OFFSET, namely > > [0xffffffff80000000, 0xffffffffc0000000], so physical address can only be randomized > > in region [LOAD_PHYSICAL_ADDR, CONFIG_RANDOMIZE_BASE_MAX_OFFSET], namely [16M, 1G]. > > > > So hpa and Vivek suggested the randomization should be done separately for both physical > > and virtual address. In this patchset I tried it. And after randomization, relocation > > handling only depends on virtual address changing, means I only check whether virtual > > address is randomized to other position, if yes relocation need be handled, if no just > > skip the relocation handling though physical address is randomized to different place. > > Now physical address can be randomized from 16M to 4G, virtual address offset can be > > from 16M to 1G. > > > > Leftover problem: > > hpa want to see the physical randomization can cover the whole physical memory. I > > checked code and found it's hard to do. Because in arch/x86/boot/compressed/head_64.S > > an identity mapping of 4G is built and then kaslr and decompressing are done. The #PF > > handler solution which he suggested is only available after jump into decompressed > > kernel, namely in arch/x86/kernel/head_64.S. I didn't think of a way to do the whole > > memory covering for physical address randomization, any suggestion or idea? > > > > I have no idea what the #PF thing you're referring to is, but I have > code to implement a #PF handler in boot/compressed if it would be > helpful. It's two patches: > > https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=89476ea6a2becbaee4f45c3b6689ff31b6aa959a It's awesome, I am gonna try it. Thanks a lot! Thanks Baoquan > > https://git.kernel.org/cgit/linux/kernel/git/luto/linux.git/commit/?h=sync_rand_seed&id=142d86921e6f271261584016fc8cfa5cdbf455ba > > You can't recover from a page fault in my version of this code, but that > would be straightforward to add. > > --Andy