From patchwork Wed Apr 6 02:31:30 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: 12803762 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 43D3BC433EF for ; Wed, 6 Apr 2022 16:21:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237182AbiDFQXc (ORCPT ); Wed, 6 Apr 2022 12:23:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52966 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238312AbiDFQXD (ORCPT ); Wed, 6 Apr 2022 12:23:03 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 202FA1DE6CA; Tue, 5 Apr 2022 19:31:37 -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 dfw.source.kernel.org (Postfix) with ESMTPS id B0645616CA; Wed, 6 Apr 2022 02:31:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 48457C385A1; Wed, 6 Apr 2022 02:31:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649212296; bh=2MxGsdREcZcC5dPhVe4pegMYaaOwE0pzgrqWpuXtrGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GXwGW062YdKL8+Jg+FwAV0W7WDkdIVsTVXDAEN7aXQNujZ35ZW3r/eAzX8retscRF R9mIWL8TtQRblz9fugeEJb203dMObcn5oNScGIeR3sTZoFengiBixG5/iVNGpYi/dU YhfsDDCZNrWTtqSUw78W6s1gQ9MH/u+xK5aE2Yiw/E+8AKSdcDiG/GAPzXuSu1RhLK lZ3q7+NR6Mvqb45MbN5emzUF4tUofgGHUgTqXZNN1GqMSi3+iIeRHrwmvyY3osNY8n KCqwT+BFAEC12NbbDkLtWy4gB1UYTjQ8Pj/h6lX4HUnT5sKKAgmF5yeqtbSj64VBMZ jf7B1pxWVkXmg== 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 v8 4/4] docs: bootconfig: Add how to embed the bootconfig into kernel Date: Wed, 6 Apr 2022 11:31:30 +0900 Message-Id: <164921228987.1090670.16843569536974147213.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <164921224829.1090670.9700650651725930602.stgit@devnote2> References: <164921224829.1090670.9700650651725930602.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 =================================