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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=unavailable 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 C0AF0C3F2D1 for ; Wed, 4 Mar 2020 21:46:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9FBDC20717 for ; Wed, 4 Mar 2020 21:46:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388352AbgCDVqp (ORCPT ); Wed, 4 Mar 2020 16:46:45 -0500 Received: from baldur.buserror.net ([165.227.176.147]:34414 "EHLO baldur.buserror.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387931AbgCDVqo (ORCPT ); Wed, 4 Mar 2020 16:46:44 -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 1j9boT-0000Xs-8g; Wed, 04 Mar 2020 15:44:21 -0600 Message-ID: <10913e48efea24c1d217bc5a723d6cd827945de7.camel@buserror.net> From: Scott Wood To: 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 15:44:19 -0600 In-Reply-To: <20200206025825.22934-4-yanaijie@huawei.com> References: <20200206025825.22934-1-yanaijie@huawei.com> <20200206025825.22934-4-yanaijie@huawei.com> 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: 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 3/6] powerpc/fsl_booke/64: implement KASLR for fsl_booke64 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 Thu, 2020-02-06 at 10:58 +0800, Jason Yan wrote: > 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. > > To support secondary cpu boot up, a variable __kaslr_offset was added in > first_256B section. This can help secondary cpu get the kaslr offset > before the 1:1 mapping has been setup. What specifically requires __kaslr_offset instead of using kernstart_virt_addr like 32-bit does? > > diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S > index ad79fddb974d..744624140fb8 100644 > --- a/arch/powerpc/kernel/head_64.S > +++ b/arch/powerpc/kernel/head_64.S > @@ -104,6 +104,13 @@ __secondary_hold_acknowledge: > .8byte 0x0 > > #ifdef CONFIG_RELOCATABLE > +#ifdef CONFIG_RANDOMIZE_BASE > + . = 0x58 > + .globl __kaslr_offset > +__kaslr_offset: > +DEFINE_FIXED_SYMBOL(__kaslr_offset) > + .long 0 > +#endif > /* This flag is set to 1 by a loader if the kernel should run > * at the loaded address instead of the linked address. This > * is used by kexec-tools to keep the the kdump kernel in the Why does it need to go here at a fixed address? > > /* check for a reserved-memory node and record its cell sizes */ > regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory"); > @@ -363,6 +374,17 @@ notrace void __init kaslr_early_init(void *dt_ptr, > phys_addr_t size) > unsigned long offset; > unsigned long kernel_sz; > > +#ifdef CONFIG_PPC64 > + unsigned int *__kaslr_offset = (unsigned int *)(KERNELBASE + 0x58); > + unsigned int *__run_at_load = (unsigned int *)(KERNELBASE + 0x5c); Why are you referencing these by magic offset rather than by symbol? > + /* Setup flat device-tree pointer */ > + initial_boot_params = dt_ptr; > +#endif Why does 64-bit need this but 32-bit doesn't? -Scott