From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5A98AC3F2D1 for ; Wed, 4 Mar 2020 21:26:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2FD9220866 for ; Wed, 4 Mar 2020 21:26:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729600AbgCDV0I (ORCPT ); Wed, 4 Mar 2020 16:26:08 -0500 Received: from baldur.buserror.net ([165.227.176.147]:34358 "EHLO baldur.buserror.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726440AbgCDV0H (ORCPT ); Wed, 4 Mar 2020 16:26:07 -0500 Received: from [2601:449:8480:af0:12bf:48ff:fe84:c9a0] by baldur.buserror.net with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1j9bSE-0000Sw-JS; Wed, 04 Mar 2020 15:21:23 -0600 Message-ID: From: Scott Wood To: Daniel Axtens , Jason Yan , mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, diana.craciun@nxp.com, christophe.leroy@c-s.fr, benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, keescook@chromium.org, kernel-hardening@lists.openwall.com Cc: linux-kernel@vger.kernel.org, zhaohongjiang@huawei.com Date: Wed, 04 Mar 2020 15:21:21 -0600 In-Reply-To: <87tv3drf79.fsf@dja-thinkpad.axtens.net> References: <20200206025825.22934-1-yanaijie@huawei.com> <87tv3drf79.fsf@dja-thinkpad.axtens.net> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2601:449:8480:af0:12bf:48ff:fe84:c9a0 X-SA-Exim-Rcpt-To: dja@axtens.net, yanaijie@huawei.com, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, diana.craciun@nxp.com, christophe.leroy@c-s.fr, benh@kernel.crashing.org, paulus@samba.org, npiggin@gmail.com, keescook@chromium.org, kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, zhaohongjiang@huawei.com X-SA-Exim-Mail-From: oss@buserror.net Subject: Re: [PATCH v3 0/6] implement KASLR for powerpc/fsl_booke/64 X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on baldur.buserror.net) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-02-26 at 18:16 +1100, Daniel Axtens wrote: > Hi Jason, > > > This is a try to implement KASLR for Freescale BookE64 which is based on > > my earlier implementation for Freescale BookE32: > > https://patchwork.ozlabs.org/project/linuxppc-dev/list/?series=131718 > > > > The implementation for Freescale BookE64 is similar as BookE32. One > > difference is that Freescale BookE64 set up a TLB mapping of 1G during > > booting. Another difference is that ppc64 needs the kernel to be > > 64K-aligned. So we can randomize the kernel in this 1G mapping and make > > it 64K-aligned. This can save some code to creat another TLB map at > > early boot. The disadvantage is that we only have about 1G/64K = 16384 > > slots to put the kernel in. > > > > KERNELBASE > > > > 64K |--> kernel <--| > > | | | > > +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ > > | | | |....| | | | | | | | | |....| | | > > +--+--+--+ +--+--+--+--+--+--+--+--+--+ +--+--+ > > | | 1G > > |-----> offset <-----| > > > > kernstart_virt_addr > > > > I'm not sure if the slot numbers is enough or the design has any > > defects. If you have some better ideas, I would be happy to hear that. > > > > Thank you all. > > > > Are you making any attempt to hide kernel address leaks in this series? > I've just been looking at the stackdump code just now, and it directly > prints link registers and stack pointers, which is probably enough to > determine the kernel base address: > > SPs: LRs: %pS pointer > [ 0.424506] [c0000000de403970] [c000000001fc0458] dump_stack+0xfc/0x154 > (unreliable) > [ 0.424593] [c0000000de4039c0] [c000000000267eec] panic+0x258/0x5ac > [ 0.424659] [c0000000de403a60] [c0000000024d7a00] > mount_block_root+0x634/0x7c0 > [ 0.424734] [c0000000de403be0] [c0000000024d8100] > prepare_namespace+0x1ec/0x23c > [ 0.424811] [c0000000de403c60] [c0000000024d7010] > kernel_init_freeable+0x804/0x880 > > git grep \\\"REG\\\" arch/powerpc shows a few other uses like this, all > in process.c or in xmon. > > Maybe replacing the REG format string in KASLR mode would be sufficient? Whatever we decide to do here, it's not book3e-specific so it should be considered separately from these patches. -Scott