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=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT 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 2CE34C43219 for ; Wed, 1 May 2019 17:01:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0397420835 for ; Wed, 1 May 2019 17:01:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726771AbfEARA6 (ORCPT ); Wed, 1 May 2019 13:00:58 -0400 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:34088 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726452AbfEARA6 (ORCPT ); Wed, 1 May 2019 13:00:58 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9102C80D; Wed, 1 May 2019 10:00:57 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2C2023F719; Wed, 1 May 2019 10:00:56 -0700 (PDT) Date: Wed, 1 May 2019 18:00:53 +0100 From: Mark Rutland To: Atish Patra Cc: Palmer Dabbelt , "aou@eecs.berkeley.edu" , "anup@brainfault.org" , "linux-kernel@vger.kernel.org" , "zong@andestech.com" , "linux-riscv@lists.infradead.org" Subject: Re: [PATCH] RISC-V: Add an Image header that boot loader can parse. Message-ID: <20190501170053.GG11740@lakrids.cambridge.arm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 29, 2019 at 10:42:40PM -0700, Atish Patra wrote: > On 4/29/19 4:40 PM, Palmer Dabbelt wrote: > > On Tue, 23 Apr 2019 16:25:06 PDT (-0700), atish.patra@wdc.com wrote: > > > Currently, last stage boot loaders such as U-Boot can accept only > > > uImage which is an unnecessary additional step in automating boot flows. > > > > > > Add a simple image header that boot loaders can parse and directly > > > load kernel flat Image. The existing booting methods will continue to > > > work as it is. > > > > > > Tested on both QEMU and HiFive Unleashed using OpenSBI + U-Boot + Linux. > > > > > > Signed-off-by: Atish Patra > > > --- > > > arch/riscv/include/asm/image.h | 32 ++++++++++++++++++++++++++++++++ > > > arch/riscv/kernel/head.S | 28 ++++++++++++++++++++++++++++ > > > 2 files changed, 60 insertions(+) > > > create mode 100644 arch/riscv/include/asm/image.h > > > > > > diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h > > > new file mode 100644 > > > index 000000000000..76a7e0d4068a > > > --- /dev/null > > > +++ b/arch/riscv/include/asm/image.h > > > @@ -0,0 +1,32 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > + > > > +#ifndef __ASM_IMAGE_H > > > +#define __ASM_IMAGE_H > > > + > > > +#define RISCV_IMAGE_MAGIC "RISCV" > > > + > > > +#ifndef __ASSEMBLY__ > > > +/* > > > + * struct riscv_image_header - riscv kernel image header > > > + * > > > + * @code0: Executable code > > > + * @code1: Executable code > > > + * @text_offset: Image load offset > > > + * @image_size: Effective Image size > > > + * @reserved: reserved > > > + * @magic: Magic number > > > + * @reserved: reserved > > > + */ > > > + > > > +struct riscv_image_header { > > > + u32 code0; > > > + u32 code1; > > > + u64 text_offset; > > > + u64 image_size; > > > + u64 res1; > > > + u64 magic; > > > + u32 res2; > > > + u32 res3; > > > +}; > > > > I don't want to invent our own file format. Is there a reason we can't just > > use something standard? Off the top of my head I can think of ELF files and > > multiboot. > > Additional header is required to accommodate PE header format. Currently, > this is only used for booti command but it will be reused for EFI headers as > well. Linux kernel Image can pretend as an EFI application if PE/COFF header > is present. This removes the need of an explicit EFI boot loader and EFI > firmware can directly load Linux (obviously after EFI stub implementation > for RISC-V). Adding the EFI stub on arm64 required very careful consideration of our Image header and the EFI spec, along with the PE/COFF spec. For example, to be a compliant PE/COFF header, the first two bytes of your kernel image need to be "MZ" in ASCII. On arm64 we happened to find a valid instruction that we could rely upon that met this requirement... > > > __INIT > > > ENTRY(_start) > > > + /* > > > + * Image header expected by Linux boot-loaders. The image header data > > > + * structure is described in asm/image.h. > > > + * Do not modify it without modifying the structure and all bootloaders > > > + * that expects this header format!! > > > + */ > > > + /* jump to start kernel */ > > > + j _start_kernel ... but it's not clear to me if this instruction meets that requriement. I would strongly encourage you to consider what you actually need for a compliant EFI header before you set the rest of this ABI in stone. On arm64 we also had issues with endianness, and I would strongly recommend that you define how big/little endian will work ahead of time. e.g. whether fields are always in a fixed endianness. Thanks, Mark. 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=-8.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 AD9C4C04AA8 for ; Wed, 1 May 2019 17:01:04 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7C18820835 for ; Wed, 1 May 2019 17:01:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="d6za/p8c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7C18820835 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.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=Q+AHZlS45rDt+k8KDP9e/OXQNRW6TBvkRBnFlcuc1Wg=; b=d6za/p8cTIlN3Y OX52hM47sb8xBZHMys7ifCYxiQ/ghLKlcRdMUgSKh7J+RJ21KtjttfSfvz8GAxFpwa63r4sPOlQ+2 rD4G3cJ9j9FXekH98H89EeBTh3i8TMJbB3SDCFY10tDXnK+4X9E00k9JZyRyoCaWjI0wj0D9DtUnI hXOkHX3HDr2u9p4dy4XvAIzrRKaXfk7xRbnxhyTqXCUaxi835rmGkkd0vpo3G8PGzv92BgNsQ27Ew hBljRSTZjmiDmVL2Iw240JKS+e9QVpKgZj9b7IQTwGMiWfNIO5I+SAN91kekn/WDv6zi1ogGvvwbw smiTO08dACZYNF/YDq2w==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hLsbM-0000iU-Oy; Wed, 01 May 2019 17:01:00 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hLsbJ-0000hX-PQ for linux-riscv@lists.infradead.org; Wed, 01 May 2019 17:00:59 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 9102C80D; Wed, 1 May 2019 10:00:57 -0700 (PDT) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2C2023F719; Wed, 1 May 2019 10:00:56 -0700 (PDT) Date: Wed, 1 May 2019 18:00:53 +0100 From: Mark Rutland To: Atish Patra Subject: Re: [PATCH] RISC-V: Add an Image header that boot loader can parse. Message-ID: <20190501170053.GG11740@lakrids.cambridge.arm.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190501_100057_829404_6C233B4C X-CRM114-Status: GOOD ( 21.17 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "aou@eecs.berkeley.edu" , "anup@brainfault.org" , Palmer Dabbelt , "linux-kernel@vger.kernel.org" , "zong@andestech.com" , "linux-riscv@lists.infradead.org" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Mon, Apr 29, 2019 at 10:42:40PM -0700, Atish Patra wrote: > On 4/29/19 4:40 PM, Palmer Dabbelt wrote: > > On Tue, 23 Apr 2019 16:25:06 PDT (-0700), atish.patra@wdc.com wrote: > > > Currently, last stage boot loaders such as U-Boot can accept only > > > uImage which is an unnecessary additional step in automating boot flows. > > > > > > Add a simple image header that boot loaders can parse and directly > > > load kernel flat Image. The existing booting methods will continue to > > > work as it is. > > > > > > Tested on both QEMU and HiFive Unleashed using OpenSBI + U-Boot + Linux. > > > > > > Signed-off-by: Atish Patra > > > --- > > > arch/riscv/include/asm/image.h | 32 ++++++++++++++++++++++++++++++++ > > > arch/riscv/kernel/head.S | 28 ++++++++++++++++++++++++++++ > > > 2 files changed, 60 insertions(+) > > > create mode 100644 arch/riscv/include/asm/image.h > > > > > > diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h > > > new file mode 100644 > > > index 000000000000..76a7e0d4068a > > > --- /dev/null > > > +++ b/arch/riscv/include/asm/image.h > > > @@ -0,0 +1,32 @@ > > > +/* SPDX-License-Identifier: GPL-2.0 */ > > > + > > > +#ifndef __ASM_IMAGE_H > > > +#define __ASM_IMAGE_H > > > + > > > +#define RISCV_IMAGE_MAGIC "RISCV" > > > + > > > +#ifndef __ASSEMBLY__ > > > +/* > > > + * struct riscv_image_header - riscv kernel image header > > > + * > > > + * @code0: Executable code > > > + * @code1: Executable code > > > + * @text_offset: Image load offset > > > + * @image_size: Effective Image size > > > + * @reserved: reserved > > > + * @magic: Magic number > > > + * @reserved: reserved > > > + */ > > > + > > > +struct riscv_image_header { > > > + u32 code0; > > > + u32 code1; > > > + u64 text_offset; > > > + u64 image_size; > > > + u64 res1; > > > + u64 magic; > > > + u32 res2; > > > + u32 res3; > > > +}; > > > > I don't want to invent our own file format. Is there a reason we can't just > > use something standard? Off the top of my head I can think of ELF files and > > multiboot. > > Additional header is required to accommodate PE header format. Currently, > this is only used for booti command but it will be reused for EFI headers as > well. Linux kernel Image can pretend as an EFI application if PE/COFF header > is present. This removes the need of an explicit EFI boot loader and EFI > firmware can directly load Linux (obviously after EFI stub implementation > for RISC-V). Adding the EFI stub on arm64 required very careful consideration of our Image header and the EFI spec, along with the PE/COFF spec. For example, to be a compliant PE/COFF header, the first two bytes of your kernel image need to be "MZ" in ASCII. On arm64 we happened to find a valid instruction that we could rely upon that met this requirement... > > > __INIT > > > ENTRY(_start) > > > + /* > > > + * Image header expected by Linux boot-loaders. The image header data > > > + * structure is described in asm/image.h. > > > + * Do not modify it without modifying the structure and all bootloaders > > > + * that expects this header format!! > > > + */ > > > + /* jump to start kernel */ > > > + j _start_kernel ... but it's not clear to me if this instruction meets that requriement. I would strongly encourage you to consider what you actually need for a compliant EFI header before you set the rest of this ABI in stone. On arm64 we also had issues with endianness, and I would strongly recommend that you define how big/little endian will work ahead of time. e.g. whether fields are always in a fixed endianness. Thanks, Mark. _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv