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=-11.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 59192C388F7 for ; Wed, 28 Oct 2020 14:18:01 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D7F2424734 for ; Wed, 28 Oct 2020 14:18:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="RSDgoxZ6"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="bovhRbfP" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D7F2424734 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=WZcok8D6jdxmfBpLO4KGy/StiZs1CNu7qvT08gkV2uI=; b=RSDgoxZ61p3E8cUswg9ZPJMz4 /bBz+SiFPLOcZVPFilAFJlsPl3NvbCpPerpoX2n4gMy7obqFd3LNGiBHjjMIsU1eI1b0Johy/6sJC KdrnVVK8Z8SLtG4QDr7KBKIVsmmhFX6BJytG5g7z5C8CZMwbFYGOWOT3ubPtewvdIAod1FjTmHBrZ su3v9dYoaCo5PrMecOR9SI6E5unACSqMee8M9OhjQtlTB7gxSmNdQVqgT0w5oEWN8pwu6DR1gTAN5 O19lj8rDvd5X3aDOk8cjw/2VysQGROx17ZFbxIGlJtri0AMHWjNYsRDKTQFcuUuJMfKrI2EO+Bmom lXDGkIS5Q==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXmGc-0002Fz-Vg; Wed, 28 Oct 2020 14:17:35 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXmGa-0002FM-5b for linux-arm-kernel@lists.infradead.org; Wed, 28 Oct 2020 14:17:32 +0000 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 38107246D0; Wed, 28 Oct 2020 14:17:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603894651; bh=xO4PPuqhDZmVDjSuwPtikBEi7ajcFTtBhYTJNKNMpHw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bovhRbfP2Sadu/1MiTo27xWusDe2f8O1IRslECojD1fUMjZFpLyk+1vulzsw0Eafp OWtOmBLYXYQK/TPqQ/w/pkWq9ehtruw3ZPHhdPeu/hc3a11PoFlmrZMfU0GSHst2dT QGV5Ozx9grLze9tnmcebI+9XXvbhQV8a9sjAieNc= Date: Wed, 28 Oct 2020 14:17:27 +0000 From: Will Deacon To: Ard Biesheuvel Subject: Re: [PATCH 4/4] arm64: head: tidy up the Image header definition Message-ID: <20201028141726.GE28554@willie-the-truck> References: <20201027073209.2897-1-ardb@kernel.org> <20201027073209.2897-5-ardb@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201027073209.2897-5-ardb@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201028_101732_326338_84A487E7 X-CRM114-Status: GOOD ( 21.47 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, catalin.marinas@arm.com, james.morse@arm.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, Oct 27, 2020 at 08:32:09AM +0100, Ard Biesheuvel wrote: > Even though support for EFI boot remains entirely optional for arm64, > it is unlikely that we will ever be able to repurpose the image header > fields that the EFI loader relies on, i.e., the magic NOP at offset > 0x0 and the PE header address at offset 0x3c. > > So let's factor out the differences into a 'magic_nop' macro and a local > symbol representing the PE header address, and move the conditional > definitions into efi-header.S, taking into account whether CONFIG_EFI is > enabled or not. How many architectures can claim to have both a "magic nop" and a "mysterious nop", hey? > Signed-off-by: Ard Biesheuvel > --- > arch/arm64/kernel/efi-header.S | 43 +++++++++++++++----- > arch/arm64/kernel/head.S | 19 +-------- > 2 files changed, 35 insertions(+), 27 deletions(-) > > diff --git a/arch/arm64/kernel/efi-header.S b/arch/arm64/kernel/efi-header.S > index ddaf57d825b5..7b7ac4316d95 100644 > --- a/arch/arm64/kernel/efi-header.S > +++ b/arch/arm64/kernel/efi-header.S > @@ -7,7 +7,27 @@ > #include > #include > > + .macro magic_nop > +#ifdef CONFIG_EFI > +.L_head: > + /* > + * This add instruction has no meaningful effect except that > + * its opcode forms the magic "MZ" signature required by UEFI. > + */ > + add x13, x18, #0x16 It's probably faster too ;) > +#else > + /* > + * Bootloaders may inspect the opcode at the start of the kernel > + * image to decide if the kernel is capable of booting via UEFI. > + * So put an ordinary NOP here, not the "MZ.." pseudo-nop above. > + */ > + nop Let's just hope nobody was decoding the branch instruction... Acked-by: Will Deacon >will@kernel.org> Will _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel