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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0FF04C433FE for ; Mon, 14 Mar 2022 09:09:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237850AbiCNJKO (ORCPT ); Mon, 14 Mar 2022 05:10:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237855AbiCNJKI (ORCPT ); Mon, 14 Mar 2022 05:10:08 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22B833D4AA; Mon, 14 Mar 2022 02:08:55 -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 97FF9612BB; Mon, 14 Mar 2022 09:08:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id B682DC340E9; Mon, 14 Mar 2022 09:08:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1647248934; bh=FwRy95YaoTK2BNBsAgnwyFkUwJ1K6hC1h5SRyvWqEcc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eFv4qW0zk+Q4ROflZLHSfSc7/GdW/JJTymTEGHG4ab37a+OEHGBLg6hucLF/BEMOc 4u0LS/E0OoHkXaX+D8c7tDe1zzKlffiRv5Dt9Z8tOjDYB4GXpNCucxNpR3ZiUSVj7t VJ1qVYGrCNXO/jBw/wTqbRch/pPViqesEmFf81yRHcwS59I0WDiJ1+3STDgXa5wRhM eRul9IN2FQz/yHS5TWfuMBIJHSZM+9ncVf/aenPo8/ir4/UOr4lHiF+83iehh07SRa +YDGzpYqSRJm1+RFwCkK3CRM4rONeSjSoQP55KOSznp0HYSZithsyrc8ZVoDTHptPd 8x/5rlYGRYYlg== From: Masami Hiramatsu To: Steven Rostedt Cc: Masami Hiramatsu , Padmanabha Srinivasaiah , LKML , Jonathan Corbet , linux-doc@vger.kernel.org, Randy Dunlap Subject: [PATCH v2 3/3] docs: bootconfig: Add how to embed the bootconfig into kernel Date: Mon, 14 Mar 2022 18:08:50 +0900 Message-Id: <164724893057.731226.7051999254450413648.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <164724890153.731226.1478494969800777757.stgit@devnote2> References: <164724890153.731226.1478494969800777757.stgit@devnote2> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Add a description how to embed the bootconfig file into kernel. Signed-off-by: Masami Hiramatsu --- 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 | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index a1860fc0ca88..9028e0f1307b 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 +202,24 @@ 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_EMBED_BOOT_CONFIG=y + CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE" + +``CONFIG_EMBED_BOOT_CONFIG_FILE`` requires a correct absolute path to +the bootconfig file. 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 =================================