From patchwork Tue Mar 1 06:49:53 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Kefeng Wang X-Patchwork-Id: 547692 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 10FFAC433F5 for ; Tue, 1 Mar 2022 06:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231262AbiCAGui (ORCPT ); Tue, 1 Mar 2022 01:50:38 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43560 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232304AbiCAGuh (ORCPT ); Tue, 1 Mar 2022 01:50:37 -0500 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3DEA21C930 for ; Mon, 28 Feb 2022 22:49:56 -0800 (PST) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4K777d4gNRz9sSK; Tue, 1 Mar 2022 14:46:21 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Tue, 1 Mar 2022 14:49:54 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2308.21; Tue, 1 Mar 2022 14:49:53 +0800 Message-ID: <894d1598-7b05-9406-5c1a-162b749bb4e8@huawei.com> Date: Tue, 1 Mar 2022 14:49:53 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.5.1 Content-Language: en-US To: Will Deacon , Ard Biesheuvel CC: Linux ARM , , Mark Rutland From: Kefeng Wang Subject: [Question] Should retain 2M alignment if kernel image is bad aligned at entry or BSS overlaps? X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggeme710-chm.china.huawei.com (10.1.199.106) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org Hi Ard，Will and all maintainer， As commit 3a262423755b ("efi/libstub: arm64: Relax 2M alignment again for relocatable kernels") saids, a relocatable image does not need to be copied to a 2M aligned offset if it was loaded on a 64k boundary (for a 4 KB granule kernel) by EFI. But if there is some FIRMWARE BUG, 1) kernel image not aligned on 64k boundary or 2) Image BSS overlaps adjacent EFI memory region When kaslr is disabled(eg, EFI_RNG_PROTOCOL unavailable), it will leads KPTI forced ON after kernel image relocated, message shown below,   CPU features: kernel page table isolation forced ON by KASLR   ...   KASLR disabled due to lack of seed The KASLR don't enabled actually, and KPTI is forced enabled which could affect performance. I found commit 7c116db24d94 ("efi/libstub/arm64: Retain 2MB kernel Image alignment if !KASLR") in v5.8, should we retain 2M alignment if kernel image is bad aligned at entry or BSS overlaps?         /* @@ -119,9 +120,11 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,         if (image->image_base != _text)                 efi_err("FIRMWARE BUG: efi_loaded_image_t::image_base has bogus value\n"); -       if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN)) +       if (!IS_ALIGNED((u64)_text, SEGMENT_ALIGN)) { +               need_2m_aligned = true;                 efi_err("FIRMWARE BUG: kernel image not aligned on %dk boundary\n",                         SEGMENT_ALIGN >> 10); +       }         kernel_size = _edata - _text;         kernel_memsize = kernel_size + (_end - _edata); @@ -142,6 +145,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,         if (status != EFI_SUCCESS) {                 if (!check_image_region((u64)_text, kernel_memsize)) { +                       need_2m_aligned = true;                         efi_err("FIRMWARE BUG: Image BSS overlaps adjacent EFI memory region\n");                 } else if (IS_ALIGNED((u64)_text, min_kimg_align)) {                         /* @@ -152,7 +156,8 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,                         *reserve_size = 0;                         return EFI_SUCCESS;                 } - +               if (efi_nokaslr & need_2m_aligned) +                       min_kimg_align = MIN_KIMG_ALIGN;                 status = efi_allocate_pages_aligned(*reserve_size, reserve_addr,                                                     ULONG_MAX, min_kimg_align); diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c index 9cc556013d08..47ecd9b80db3 100644 --- a/drivers/firmware/efi/libstub/arm64-stub.c +++ b/drivers/firmware/efi/libstub/arm64-stub.c @@ -87,6 +87,7 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,  {         efi_status_t status;         unsigned long kernel_size, kernel_memsize = 0; +       bool need_2m_aligned = false;         u32 phys_seed = 0;