From patchwork Thu Mar 31 08:25:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 12796849 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 6BB55C433EF for ; Thu, 31 Mar 2022 08:25:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232764AbiCaI1U (ORCPT ); Thu, 31 Mar 2022 04:27:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56634 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232785AbiCaI07 (ORCPT ); Thu, 31 Mar 2022 04:26:59 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 999E81BB794; Thu, 31 Mar 2022 01:25:11 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 4B01DB82005; Thu, 31 Mar 2022 08:25:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6C1E4C340ED; Thu, 31 Mar 2022 08:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1648715109; bh=2MxGsdREcZcC5dPhVe4pegMYaaOwE0pzgrqWpuXtrGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=A1lgvRIuimSfgiCzSsPqrqzPyqJ/Ts6QNUpz89s8ANThoeoFMFD3+ixQA727+HWOq REuBOInQOtfZoLxQGzi1HT1fAoN63Fcit+so0ojLvQ3R/HUlvNitTG8lnnYQ8h2VG4 EVguk8Nk4AnfSV4RKvcwqVp0qg56pDWvHDwKSIT3eIDgeMUjmC5fCwLuZEc4gc6MgE Lt/ifHthtHVcalu9xui4rO+kozd/ZER98FqzuTcfHNdUWqxMtGAc7FeE8lOeakOegP /N2iVe/5PHy066XlyX+NS5o2NF2W9CsvPYLQpvsCKCMdKTcKDTxgdT4v5D0pm0YP/V /8ayKrr16WUaw== From: Masami Hiramatsu To: Steven Rostedt Cc: Masami Hiramatsu , Padmanabha Srinivasaiah , LKML , Jonathan Corbet , linux-doc@vger.kernel.org, Randy Dunlap , Nick Desaulniers , Sami Tolvanen , Nathan Chancellor , llvm@lists.linux.dev, Masahiro Yamada , Linux Kbuild mailing list Subject: [PATCH v7 4/4] docs: bootconfig: Add how to embed the bootconfig into kernel Date: Thu, 31 Mar 2022 17:25:03 +0900 Message-Id: <164871510350.178991.10848731777317835399.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <164871505771.178991.7870442736805590948.stgit@devnote2> References: <164871505771.178991.7870442736805590948.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@vger.kernel.org Add a description how to embed the bootconfig file into kernel. Signed-off-by: Masami Hiramatsu --- Changes in v7: - Rename CONFIG_EMBED_BOOT_CONFIG* to CONFIG_BOOT_CONFIG_EMBED*. Changes in v5: - Update CONFIG_EMBED_BOOT_CONFIG_FILE which can accept relative path. Changes in v3: - Fix typos. Changes in v2: - Corrected the text accoding to Randy's suggestion. - Do not reccomend to use relative path for CONFIG_EMBED_BOOT_CONFIG_FILE. --- Documentation/admin-guide/bootconfig.rst | 31 +++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index a1860fc0ca88..d99994345d41 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -158,9 +158,15 @@ Each key-value pair is shown in each line with following style:: Boot Kernel With a Boot Config ============================== -Since the boot configuration file is loaded with initrd, it will be added -to the end of the initrd (initramfs) image file with padding, size, -checksum and 12-byte magic word as below. +There are two options to boot the kernel with bootconfig: attaching the +bootconfig to the initrd image or embedding it in the kernel itself. + +Attaching a Boot Config to Initrd +--------------------------------- + +Since the boot configuration file is loaded with initrd by default, +it will be added to the end of the initrd (initramfs) image file with +padding, size, checksum and 12-byte magic word as below. [initrd][bootconfig][padding][size(le32)][checksum(le32)][#BOOTCONFIG\n] @@ -196,6 +202,25 @@ To remove the config from the image, you can use -d option as below:: Then add "bootconfig" on the normal kernel command line to tell the kernel to look for the bootconfig at the end of the initrd file. +Embedding a Boot Config into Kernel +----------------------------------- + +If you can not use initrd, you can also embed the bootconfig file in the +kernel by Kconfig options. In this case, you need to recompile the kernel +with the following configs:: + + CONFIG_BOOT_CONFIG_EMBED=y + CONFIG_BOOT_CONFIG_EMBED_FILE="/PATH/TO/BOOTCONFIG/FILE" + +``CONFIG_BOOT_CONFIG_EMBED_FILE`` requires an absolute path or a relative +path to the bootconfig file from source tree or object tree. +The kernel will embed it as the default bootconfig. + +Just as when attaching the bootconfig to the initrd, you need ``bootconfig`` +option on the kernel command line to enable the embedded bootconfig. + +Note that even if you set this option, you can override the embedded +bootconfig by another bootconfig which attached to the initrd. Kernel parameters via Boot Config =================================