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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9B8DBC433F5 for ; Sat, 7 May 2022 09:28:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1446156AbiEGJcU (ORCPT ); Sat, 7 May 2022 05:32:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37550 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S245217AbiEGJcP (ORCPT ); Sat, 7 May 2022 05:32:15 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C1F1A55343; Sat, 7 May 2022 02:28:28 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KwMXR5vqtz1JBtC; Sat, 7 May 2022 17:27:19 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 7 May 2022 17:28:26 +0800 Received: from [10.174.178.120] (10.174.178.120) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Sat, 7 May 2022 17:28:25 +0800 Message-ID: Date: Sat, 7 May 2022 17:28:24 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH 0/2] Add support to relocate kernel image to mirrored region To: CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , References: <20220419070150.254377-1-mawupeng1@huawei.com> From: mawupeng In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.120] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/5/3 17:58, Ard Biesheuvel 写道: > On Tue, 19 Apr 2022 at 08:43, Wupeng Ma wrote: >> >> From: Ma Wupeng >> >> Now system image will perfer to be located to mirrored regions both KASLR >> on and off. >> > > Hello Ma Wupeng, > > I wonder if we could simplify this as follows: > - ignore the non-KASLR case for now, and rely on the bootloader > load the image into mirrored memory if it exists; In grub, memory for static image is allocated via the following path: grub_cmd_linux kernel = grub_malloc(filelen) kernel_alloc_addr = grub_efi_allocate_any_pages (kernel_alloc_pages) grub_memcpy (kernel_addr, kernel, grub_min(filelen, kernel_size)) grub_loader_set (grub_linux_boot, grub_linux_unload, 0) Can we get memory from mirrored region by the following steps: 1. get memory map by calling grub_efi_get_memory_map() 2. iter all memory map to find a suitable mirrored memory area 3. locate kernel image to this area So, if kaslr is not enabled - grub will load kernel into mirrored region else - arm64-stub.c will relocate kernel image to mirrored region Is this feasible? > - simplify the KASLR case to the below. Yes, we can certainly do this. I will remove my code and use yours. > > I think this is reasonable, because it means we take mirrored memory > into account when we decide to move the image anyway, but expect the > boot chain to take care of this if there is no need to move the image. > > -------------8<------------------ > --- a/drivers/firmware/efi/libstub/randomalloc.c > +++ b/drivers/firmware/efi/libstub/randomalloc.c > @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size, > unsigned long random_seed) > { > unsigned long map_size, desc_size, total_slots = 0, target_slot; > + unsigned long total_mirrored_slots = 0; > unsigned long buff_size; > efi_status_t status; > efi_memory_desc_t *memory_map; > @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size, > slots = get_entry_num_slots(md, size, ilog2(align)); > MD_NUM_SLOTS(md) = slots; > total_slots += slots; > + if (md->attribute & EFI_MEMORY_MORE_RELIABLE) > + total_mirrored_slots += slots; > } > > + /* only consider mirrored slots for randomization if any exist */ > + if (total_mirrored_slots > 0) > + total_slots = total_mirrored_slots; > + > /* find a random number between 0 and total_slots */ > target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32; > > @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size, > efi_physical_addr_t target; > unsigned long pages; > > + if (total_mirrored_slots > 0 && > + !(md->attribute & EFI_MEMORY_MORE_RELIABLE)) > + continue; > + > if (target_slot >= MD_NUM_SLOTS(md)) { > target_slot -= MD_NUM_SLOTS(md); > continue; > .