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=-19.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 2B6C2C4320A for ; Thu, 26 Aug 2021 09:12:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 13D52610A1 for ; Thu, 26 Aug 2021 09:12:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240896AbhHZJNL (ORCPT ); Thu, 26 Aug 2021 05:13:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:56458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240568AbhHZJNK (ORCPT ); Thu, 26 Aug 2021 05:13:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 1E6E1610C9; Thu, 26 Aug 2021 09:12:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629969143; bh=uDYKss5H51+qlIxfwS1FoAJZats7oowU7sDnItkFnkM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g+Dd0uchzkhttjR2fUYqF873FDaPGvREczo8WfLlhIj9+AMkkYd59L9t5sqNKUllR Z+opvWlq5I8niffvM4jJSCYpkPS7BDFULoSYJsIwOzsjLm6eUgJdDnrrJjSfLOCbpR IuYfFSeYYS2ye33ZK9BY8LOYB1aq6wAKxUpYH6zPmS9jltgXEE5DnAJSHDtjdW23iO urlf5VXah4PJsqzjlSAYyrs2KoQCM1chOl/z1TDeEwW4bWrcdKlW40auTe8i+H8c0E ueCXJLC55xEuHdUqmsUKgEtXt99ET+LgEt6iCpuXDx/QaWf1kQRcrVm6/fAeJCjjWV fP6k6YD4NXd9A== From: Masami Hiramatsu To: Steven Rostedt Cc: Masami Hiramatsu , LKML , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [PATCH 3/3] docs: bootconfig: Add how to use bootconfig for kernel parameters Date: Thu, 26 Aug 2021 18:12:21 +0900 Message-Id: <162996914170.236535.439632993302650531.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <162996911932.236535.7533708592332223449.stgit@devnote2> References: <162996911932.236535.7533708592332223449.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-kernel@vger.kernel.org Add a section to describe how to use the bootconfig for specifying kernel and init parameters. This is an important section because it is the reason why this document is under the admin-guide. Signed-off-by: Masami Hiramatsu Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org --- Documentation/admin-guide/bootconfig.rst | 39 +++++++++++++++++++++++++++++- 1 file changed, 38 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst index 6a79f2e59396..a1860fc0ca88 100644 --- a/Documentation/admin-guide/bootconfig.rst +++ b/Documentation/admin-guide/bootconfig.rst @@ -178,7 +178,7 @@ update the boot loader and the kernel image itself as long as the boot loader passes the correct initrd file size. If by any chance, the boot loader passes a longer size, the kernel fails to find the bootconfig data. -To do this operation, Linux kernel provides "bootconfig" command under +To do this operation, Linux kernel provides ``bootconfig`` command under tools/bootconfig, which allows admin to apply or delete the config file to/from initrd image. You can build it by the following command:: @@ -196,6 +196,43 @@ 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. + +Kernel parameters via Boot Config +================================= + +In addition to the kernel command line, the boot config can be used for +passing the kernel parameters. All the key-value pairs under ``kernel`` +key will be passed to kernel cmdline directly. Moreover, the key-value +pairs under ``init`` will be passed to init process via the cmdline. +The parameters are concatinated with user-given kernel cmdline string +as the following order, so that the command line parameter can override +bootconfig parameters (this depends on how the subsystem handles parameters +but in general, earlier parameter will be overwritten by later one.):: + + [bootconfig params][cmdline params] -- [bootconfig init params][cmdline init params] + +Here is an example of the bootconfig file for kernel/init parameters.:: + + kernel { + root = 01234567-89ab-cdef-0123-456789abcd + } + init { + splash + } + +This will be copied into the kernel cmdline string as the following:: + + root="01234567-89ab-cdef-0123-456789abcd" -- splash + +If user gives some other command line like,:: + + ro bootconfig -- quiet + +The final kernel cmdline will be the following:: + + root="01234567-89ab-cdef-0123-456789abcd" ro bootconfig -- splash quiet + + Config File Limitation ======================