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_1 autolearn=ham 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 E3B29C3F2D1 for ; Thu, 5 Mar 2020 02:32:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C272D20838 for ; Thu, 5 Mar 2020 02:32:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725880AbgCECch (ORCPT ); Wed, 4 Mar 2020 21:32:37 -0500 Received: from szxga06-in.huawei.com ([45.249.212.32]:41414 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725810AbgCECch (ORCPT ); Wed, 4 Mar 2020 21:32:37 -0500 Received: from DGGEMS410-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id B7B85929861A7F9C9A0F; Thu, 5 Mar 2020 10:32:35 +0800 (CST) Received: from [127.0.0.1] (10.173.221.195) by DGGEMS410-HUB.china.huawei.com (10.3.19.210) with Microsoft SMTP Server id 14.3.439.0; Thu, 5 Mar 2020 10:32:26 +0800 Subject: Re: [PATCH v3 3/6] powerpc/fsl_booke/64: implement KASLR for fsl_booke64 To: Scott Wood , , , , , , , , , CC: , References: <20200206025825.22934-1-yanaijie@huawei.com> <20200206025825.22934-4-yanaijie@huawei.com> <10913e48efea24c1d217bc5a723d6cd827945de7.camel@buserror.net> From: Jason Yan Message-ID: Date: Thu, 5 Mar 2020 10:32:25 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <10913e48efea24c1d217bc5a723d6cd827945de7.camel@buserror.net> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.173.221.195] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2020/3/5 5:44, Scott Wood 写道: > 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? > kernstart_virt_addr is in the data section. At the early boot we only have a 64M tlb mapping. For the 32-bit I limited the kernel in a 64M-aligned region so that we can always get kernstart_virt_addr. But for the 64-bit the kernel is bigger and not suitable to limit it in a 64M-aligned region. So if we use kernstart_virt_addr and the kernel is randomized like below , the secondary cpus will not boot up: +------------+------------+ | 64M | 64M | +------------+------------+ ^ ^ | kernel | ^ kernstart_virt_addr So I have to put the kernel offset in the first 64K along with the init text. >> >> 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? > It does not need to be at a fixed address. I just want to keep consistent and stay along with __run_at_load. > >> >> /* 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? > I'm not sure if relocat works for fixed symbols. I will have a test and swith to reference them by symbols if it works fine. > >> + /* Setup flat device-tree pointer */ >> + initial_boot_params = dt_ptr; >> +#endif > > Why does 64-bit need this but 32-bit doesn't? 32-bit called early_get_first_memblock_info() very early which implicitly setup the device-tree pointer. > > -Scott > > > > . >