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 86173C433F5 for ; Sun, 13 Mar 2022 13:56:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234299AbiCMN5y (ORCPT ); Sun, 13 Mar 2022 09:57:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42526 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234071AbiCMN5v (ORCPT ); Sun, 13 Mar 2022 09:57:51 -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 3DC245F270; Sun, 13 Mar 2022 06:56:43 -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 E4C3EB80CAA; Sun, 13 Mar 2022 13:56:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9019BC340E8; Sun, 13 Mar 2022 13:56:39 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1647179800; bh=73rd6F+wRPyuWn2PJNKyBIpSAN5NcV1wb/fm3qTL78Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=peVZnn05PjSL2hwSxpz5p92QIVWGRZOLkqotSVgZlb1A+/Bg9V/kLVPhWN7FNZpOU VrQy98bFfmAWUAT3VJ0UCKMMP9DY0i3i3LO9RNKjEqHYcd9wnZt7ct7ETfCH+mK8Vx bw1bng52fFQaK2KUkhpnQXFvIBYhATajRm+e9MXeHpIsHyRNmTvwSWeBVz0mGT/FBT BzOnJ1auXxo0NJrx/EnHNeePv4kESHbEXVYzS4fHCx80lcFimDC78cc1aYI4PVHbT5 ta+6xJn6udE5CUjezBjYG/5hlQbBXK0NKxreq6Ahj03R9rfPgYEvuhGc6e1NzkGJVd +pyAYagnI5CiQ== From: Masami Hiramatsu To: Steven Rostedt Cc: Masami Hiramatsu , Padmanabha Srinivasaiah , LKML , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [PATCH 3/3] docs: bootconfig: Add how to embed the bootconfig into kernel Date: Sun, 13 Mar 2022 22:56:37 +0900 Message-Id: <164717979739.656425.17945326639021989871.stgit@devnote2> X-Mailer: git-send-email 2.25.1 In-Reply-To: <164717976871.656425.6189991392886085524.stgit@devnote2> References: <164717976871.656425.6189991392886085524.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 description how to embed the bootconfig file into kernel. Signed-off-by: Masami Hiramatsu --- 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..a172c669997a 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 2 options to boot the kernel with bootconfig, one is attaching +bootconfig to initrd image, and embedding 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 to the +kernel by Kconfig options. In This case, you need to recompile the kernel +with the following configs:: + + COFNIG_EMBED_BOOT_CONFIG=y + CONFIG_EMBED_BOOT_CONFIG_FILE="/PATH/TO/BOOTCONFIG/FILE" + +You need to set the correct path (relative path from kernel build directory +or absolute path) to the ``CONFIG_EMBED_BOOT_CONFIG_FILE`` option. +Then the kernel will embed the bootconfig file as a default bootconfig. + +As same as attaching to initrd, you need ``bootconfig`` option to 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 =================================