From patchwork Wed Feb 19 09:43:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ard Biesheuvel X-Patchwork-Id: 206561 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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT 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 96AACC34047 for ; Wed, 19 Feb 2020 09:43:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 70BB024676 for ; Wed, 19 Feb 2020 09:43:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582105431; bh=IFeKqUgeJV2n7+UfgpcbERriRaaDjRKasrOnKGYW4KE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=dCjs+mhEMkipEY5Ji2hxkc8+EqdB1c/LBUN3ojC8m9kp7qz70/l5D6cw2UgUpOJtm pgtOdM0i5ks62VF+JxHjBzuwqF1xZqQwuSYUL0yhGyZ97krw3EjYhB0UuUneg2H129 4LUDSGvCxGc6BqSNCcx3I0bwVrZi87wFt6oJJkCE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726385AbgBSJnv (ORCPT ); Wed, 19 Feb 2020 04:43:51 -0500 Received: from mail.kernel.org ([198.145.29.99]:56130 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726210AbgBSJnv (ORCPT ); Wed, 19 Feb 2020 04:43:51 -0500 Received: from e123331-lin.home (amontpellier-657-1-18-247.w109-210.abo.wanadoo.fr [109.210.65.247]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DA20D24671; Wed, 19 Feb 2020 09:43:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582105430; bh=IFeKqUgeJV2n7+UfgpcbERriRaaDjRKasrOnKGYW4KE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=p2MTQBZizJ4UrgefK5SkbPxOEESDJrHLVICZbwMsWK7jr1wha9aA37dROV0bjUsKX SVTyYC3YVlQYlwSV/GcPiMbRg4+LVDquCGj/r8DlVTcv3HXP5AUYtxk17/YEsqaSRa N2IWtLzo9GMmVN8yDtdNa7sROdhZcH5SzHSHcPd4= From: Ard Biesheuvel To: linux-efi@vger.kernel.org Cc: linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Russell King , Marc Zyngier , Nicolas Pitre , Catalin Marinas , Tony Lindgren Subject: [PATCH v2 1/4] efi/arm: work around missing cache maintenance in decompressor handover Date: Wed, 19 Feb 2020 10:43:37 +0100 Message-Id: <20200219094340.16597-2-ardb@kernel.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200219094340.16597-1-ardb@kernel.org> References: <20200219094340.16597-1-ardb@kernel.org> Sender: linux-efi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-efi@vger.kernel.org The EFI stub executes within the context of the zImage as it was loaded by the firmware, which means it is treated as an ordinary PE/COFF executable, which is loaded into memory, and cleaned to the PoU to ensure that it can be executed safely while the MMU and caches are on. When the EFI stub hands over to the decompressor, we clean the caches by set/way and disable the MMU and D-cache, to comply with the Linux boot protocol for ARM. However, cache maintenance by set/way is not sufficient to ensure that subsequent instruction fetches and data accesses done with the MMU off see the correct data. This means that proceeding as we do currently is not safe, especially since we also perform data accesses with the MMU off, from a literal pool as well as the stack. So let's kick this can down the road a bit, and jump into the relocated zImage before disabling the caches. This removes the requirement to perform any by-VA cache maintenance on the original PE/COFF executable, but it does require that the relocated zImage is cleaned to the PoC, which is currently not the case. This will be addressed in a subsequent patch. Signed-off-by: Ard Biesheuvel --- arch/arm/boot/compressed/head.S | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S index 088b0a060876..6c98d3d2de2f 100644 --- a/arch/arm/boot/compressed/head.S +++ b/arch/arm/boot/compressed/head.S @@ -1461,6 +1461,19 @@ ENTRY(efi_stub_entry) @ Preserve return value of efi_entry() in r4 mov r4, r0 bl cache_clean_flush + + @ The PE/COFF loader might not have cleaned the code we are + @ running beyond the PoU, and so calling cache_off below from + @ inside the PE/COFF loader allocated region is unsafe. Let's + @ assume our own zImage relocation code did a better job, and + @ jump into its version of this routine before proceeding. + ldr r0, [sp] @ relocated zImage + ldr r1, 0f + sub r1, r0, r1 + mov pc, r1 @ no mode switch + .align 2 +0: .long start - (. + 4) + bl cache_off @ Set parameters for booting zImage according to boot protocol @@ -1469,12 +1482,7 @@ ENTRY(efi_stub_entry) mov r0, #0 mov r1, #0xFFFFFFFF mov r2, r4 - - @ Branch to (possibly) relocated zImage that is in [sp] - ldr lr, [sp] - ldr ip, =start_offset - add lr, lr, ip - mov pc, lr @ no mode switch + b __efi_start efi_load_fail: @ Return EFI_LOAD_ERROR to EFI firmware on error.