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 A01FAC433EF for ; Thu, 19 May 2022 11:09:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237291AbiESLJi (ORCPT ); Thu, 19 May 2022 07:09:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40542 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237168AbiESLJY (ORCPT ); Thu, 19 May 2022 07:09:24 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD0DFB0429; Thu, 19 May 2022 04:09:22 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4L3nCd4PfdzjWwl; Thu, 19 May 2022 19:08:29 +0800 (CST) Received: from dggpemm500014.china.huawei.com (7.185.36.153) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 19 May 2022 19:09:20 +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; Thu, 19 May 2022 19:09:19 +0800 Message-ID: <7058b8d8-c0cb-108e-0db9-2fdf5fb154cf@huawei.com> Date: Thu, 19 May 2022 19:09:18 +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 2022/5/7 17:28, mawupeng 写道: > > > 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? Is this a feasible proposal to relocate the static kernel image itself into more reliable memory? > >> - 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; >> .