From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752609AbdFOIqO (ORCPT ); Thu, 15 Jun 2017 04:46:14 -0400 Received: from mgwym02.jp.fujitsu.com ([211.128.242.41]:44773 "EHLO mgwym02.jp.fujitsu.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097AbdFOIqL (ORCPT ); Thu, 15 Jun 2017 04:46:11 -0400 X-Greylist: delayed 664 seconds by postgrey-1.27 at vger.kernel.org; Thu, 15 Jun 2017 04:46:11 EDT From: "Izumi, Taku" To: "'Baoquan He'" , "linux-kernel@vger.kernel.org" CC: "keescook@chromium.org" , "x86@kernel.org" , "Fan, Chao" , "Cao, Jin" , "Dou, Liyang" Subject: RE: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if existed Thread-Topic: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if existed Thread-Index: AQHS5a3qc4zmiy2IQUafbuRtqaZlzqIlk/hA Date: Thu, 15 Jun 2017 08:34:57 +0000 Message-ID: References: <1497513169-25283-1-git-send-email-bhe@redhat.com> <20170615080329.GB16181@x1> In-Reply-To: <20170615080329.GB16181@x1> Accept-Language: ja-JP, en-US Content-Language: ja-JP X-MS-Has-Attach: X-MS-TNEF-Correlator: x-securitypolicycheck: OK by SHieldMailChecker v2.4.6 x-shieldmailcheckerpolicyversion: FJ-ISEC-20160315 x-shieldmailcheckermailid: cb2d954d11f548f1be2f0095944f632f x-originating-ip: [10.33.110.157] Content-Type: text/plain; charset="gb2312" MIME-Version: 1.0 X-SecurityPolicyCheck-GC: OK by FENCE-Mail X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id v5F8kLKi025065 Dear Baoquan, > > Our customer reported that Kernel text may be located on non-mirror > > region (movable zone) when both address range mirroring feature and > > KASLR are enabled. I know your customer :) > > The functions of address range mirroring feature are as follows. > > - The physical memory region whose descriptors in EFI memory map have > > EFI_MEMORY_MORE_RELIABLE attribute (bit: 16) are mirrored > > - The function arranges such mirror region into normal zone and other > region > > into movable zone in order to locate kernel code and data on mirror > > region > > > > So we need restrict kernel to be located inside mirror region if it is > > existed. > > > > The method is very simple. If efi is enabled, just iterate all efi > > memory map and pick up mirror region to process for adding candidate > > of slot. If efi disabled or no mirror region existed, still process > > e820 memory map. This won't bring much efficiency loss, at worst we > > just go through all efi memory maps and found no mirror. > > > > One question: > > From code, though mirror regions are existed, they are meaningful only > > if kernelcore=mirror kernel option is specified. Not sure if my > > understanding is correct. Your understanding is almost correct. Only when "kernelcore=mirror" specified, the above procedure works. But, if mirrored regions are existed, bootmem allocator tries to allocate from mirrored region independently of "kerenelcore=mirror" option. So, IMHO, kernel text is important, so putting it to mirrored (more reliable) region is reasonable whether or not "kernelcore=mirror" is specified. Anyway thanks for submitting patch. We have Address Range Mirroring capable machine, so we'll test your patch. Sincerely, Taku Izumi > > Since you are the author of kernelcore=mirror related code and expert on > mirror feature, could you help answer above question? > > Thanks > Baoquan > > > > NOTE: > > I haven't got a machine with efi mirror region enabled, so only test > > the > > e820 map processing case and the case of no mirror region on efi machine. > > So set this as a RFC patchset, will post formal one after above > > question is made clear and mirror issue test passed. > > > > Baoquan He (2): > > x86/boot/KASLR: Adapt process_e820_entry for all kinds of memory map > > x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if > > existed > > > > arch/x86/boot/compressed/kaslr.c | 129 > > +++++++++++++++++++++++++++++++-------- > > 1 file changed, 104 insertions(+), 25 deletions(-) > > > > -- > > 2.5.5 > >