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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 6E518C33CB7 for ; Sun, 19 Jan 2020 13:36:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3092220730 for ; Sun, 19 Jan 2020 13:36:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579440989; bh=SU11H1UmSR3TB45hrBy9iIiOWcaXljmQ3ldAW+zGMvA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=y44LTmss9ZrEWB1oVuJOnhOqmLOBZ0/fls8lUPvM++k9KnkhxGTOGz34vh30UEAch fwQ7dgmsqlj5Bs5jEYWilj9Fktn5sjgxkTWyQnHFpI8osp5GYC169/QmOg6+PrAcu3 03Czw2JfStahLEwyEkSXbZxcYGOCOxGc/mhWoXNc= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727243AbgASNg2 (ORCPT ); Sun, 19 Jan 2020 08:36:28 -0500 Received: from mail.kernel.org ([198.145.29.99]:54026 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726903AbgASNg2 (ORCPT ); Sun, 19 Jan 2020 08:36:28 -0500 Received: from devnote2 (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D984320663; Sun, 19 Jan 2020 13:36:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579440986; bh=SU11H1UmSR3TB45hrBy9iIiOWcaXljmQ3ldAW+zGMvA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=fGgq1Wa32ISLwK7SovTBzxsCeHBQRpgDCwwdM9WN2/6c7BBAPL/Q5U+mJzFd/67Hd ZRInT39DUOKoIUkwM7MHDjI+a9PQoySLCpTgAn/lVuAae/dhi/8GI64AQF4ZE1V6/e MToGP2bE4dQlxObW8AyLqgc9L0jTfGxd0P6klDgk= Date: Sun, 19 Jan 2020 22:36:20 +0900 From: Masami Hiramatsu To: Randy Dunlap Cc: Steven Rostedt , Ingo Molnar , Frank Rowand , Namhyung Kim , Tim Bird , Jiri Olsa , Arnaldo Carvalho de Melo , Tom Zanussi , Rob Herring , Andrew Morton , Thomas Gleixner , Greg Kroah-Hartman , Alexey Dobriyan , Jonathan Corbet , Linus Torvalds , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 09/22] Documentation: bootconfig: Add a doc for extended boot config Message-Id: <20200119223620.059338427abadec036adc3fa@kernel.org> In-Reply-To: <7823298a-88e6-4625-ff10-94b00f7963cb@infradead.org> References: <157867220019.17873.13377985653744804396.stgit@devnote2> <157867230658.17873.9309879174829924324.stgit@devnote2> <7823298a-88e6-4625-ff10-94b00f7963cb@infradead.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Randy, On Sat, 18 Jan 2020 10:28:40 -0800 Randy Dunlap wrote: > Hi, > > Editorial comments/corrections below... Thank you for your comments! This is very helpful for me. > > On 1/10/20 8:05 AM, Masami Hiramatsu wrote: > > Add a documentation for extended boot config under > > admin-guide, since it is including the syntax of boot config. > > > > Signed-off-by: Masami Hiramatsu > > --- > > Changes in v6: > > - Add a note about comment after value. > > Changes in v5: > > - Fix to insert bootconfig to TOC list alphabetically. > > - Add notes about avaliable characters in values. > > - Fix to use correct quotes (``) for .rst. > > Changes in v4: > > - Rename suppremental kernel command line to boot config. > > supplemental > > > - Update document according to the recent changes. > > - Add How to load it on boot. > > - Style bugfix. > > --- > > Documentation/admin-guide/bootconfig.rst | 184 ++++++++++++++++++++++++++++++ > > Documentation/admin-guide/index.rst | 1 > > MAINTAINERS | 1 > > 3 files changed, 186 insertions(+) > > create mode 100644 Documentation/admin-guide/bootconfig.rst > > > > > diff --git a/Documentation/admin-guide/bootconfig.rst b/Documentation/admin-guide/bootconfig.rst > > new file mode 100644 > > index 000000000000..f7475df2a718 > > --- /dev/null > > +++ b/Documentation/admin-guide/bootconfig.rst > > @@ -0,0 +1,184 @@ > > +.. SPDX-License-Identifier: GPL-2.0 > > + > > +================== > > +Boot Configuration > > +================== > > + > > +:Author: Masami Hiramatsu > > + > > +Overview > > +======== > > + > > +The boot configuration is expanding current kernel cmdline to support > > expands the current kernel command line to support OK. > > > +additional key-value data when boot the kernel in an efficient way. > > booting OK. > > > +This allows adoministrators to pass a structured-Key config file. > > administrators Oops. OK. > > > + > > +Config File Syntax > > +================== > > + > > +The boot config syntax is a simple structured key-value. Each key consists > > +of dot-connected-words, and key and value are connected by "=". The value > > +has to be terminated by semi-colon (``;``) or newline (``\n``). > > +For array value, array entries are separated by comma (``,``). :: > > + > > +KEY[.WORD[...]] = VALUE[, VALUE2[...]][;] > > (just a note: spaces are OK here, unlike in kernel command line syntax [unless quoted].) Yes. > > + > > +Each key word must contain only alphabets, numbers, dash (``-``) or underscore > > +(``_``). And each value only contains printable characters or spaces except > > +for delimiters such as semi-colon (``;``), new-line (``\n``), comma (``,``), > > +hash (``#``) and closing brace (``}``). > > what about opening brace '{'? Good question! Since the bootconfig doesn't support anonymous key-word block, opening brace doesn't become a delimiter. (So, the above explanation might better use "except for *some* delimiters"...) For example, following data should be wrong. key = value { key2 = value } > > > + > > +If you want to use those delimiters in a value, you can use either double- > > +quotes (``"VALUE"``) or single-quotes (``'VALUE'``) to quote it. Note that > > +you can not escape these quotes. > > + > > +There can be a key which doesn't have value or has an empty value. Those keys > > +are used for checking the key exists or not (like a boolean). > > I would say: checking if the key exists or not OK. > > > + > > +Key-Value Syntax > > +---------------- > > + > > +The boot config file syntax allows user to merge partially same word keys > > +by brace. For example:: > > + > > + foo.bar.baz = value1 > > + foo.bar.qux.quux = value2 > > + > > +These can be written also in:: > > + > > + foo.bar { > > + baz = value1 > > + qux.quux = value2 > > + } > > + > > +Or more shorter, written as following:: > > + > > + foo.bar { baz = value1; qux.quux = value2 } > > + > > +In both styles, same key words are automatically merged when parsing it > > +at boot time. So you can append similar trees or key-values. > > + > > +Comments > > +-------- > > + > > +The config syntax accepts shell-script style comments. The comments start > > s/start/starting/ OK. > > > +with hash ("#") until newline ("\n") will be ignored. > > + > > +:: > > + > > + # comment line > > + foo = value # value is set to foo. > > + bar = 1, # 1st element > > + 2, # 2nd element > > + 3 # 3rd element > > + > > +This is parsed as below:: > > + > > + foo = value > > + bar = 1, 2, 3 > > + > > +Note that you can not put a comment between value and delimiter(``,`` or > > +``;``). This means following config has a syntax error :: > > + > > + key = 1 # comment > > + ,2 > > + > > + > > +/proc/bootconfig > > +================ > > + > > +/proc/bootconfig is a user-space interface of the boot config. > > +Unlike /proc/cmdline, this file shows the key-value style list. > > +Each key-value pair is shown in each line with following style:: > > + > > + KEY[.WORDS...] = "[VALUE]"[,"VALUE2"...] > > + > > + > > +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. The Linux kernel decodes > > +the last part of the initrd image in memory to get the boot configuration > > +data. > > +Because of this "piggyback" method, there is no need to change or > > +update the boot loader and the kernel image itself. > > + > > +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 follwoing command:: > > by the following Oops, a typo... > > > + > > + # make -C tools/bootconfig > > + > > +To add your boot config file to initrd image, run bootconfig as below > > +(Old data is removed automatically if exists):: > > + > > + # tools/bootconfig/bootconfig -a your-config /boot/initrd.img-X.Y.Z > > + > > +To remove the config from the image, you can use -d option as below:: > > + > > + # tools/bootconfig/bootconfig -d /boot/initrd.img-X.Y.Z > > + > > + > > +C onfig File Limitation > > Config Oops > > > +====================== > > + > > +Currently the maximum config size size is 32KB and the total key-words (not > > +key-value entries) must be under 1024 nodes. > > +Note: this is not the number of entries but nodes, an entry must consume > > +more than 2 nodes (a key-word and a value). So theoretically, it will be > > +up to 512 key-value pairs. If keys contains 3 words in average, it can > > +contain 256 key-value pairs. In most cases, the number of config items > > +will be under 100 entries and smaller than 8KB, so it would be enough. > > +If the node number exceeds 1024, parser returns an error even if the file > > +size is smaller than 32KB. > > +Anyway, since bootconfig command verifies it when appending a boot config > > +to initrd image, user can notice it before boot. > > + > > + > > +Bootconfig APIs > > +=============== > > + > > +User can query or loop on key-value pairs, also it is possible to find > > +a root (prefix) key node and find key-values under that node. > > + > > +If you have a key string, you can query the value directly with the key > > +using xbc_find_value(). If you want to know what keys exist in the SKC > > +tree, you can use xbc_for_each_key_value() to iterate key-value pairs. > > +Note that you need to use xbc_array_for_each_value() for accessing > > +each arraies value, e.g.:: > > array's > (I think) Yes, OK. > > > + > > + vnode = NULL; > > + xbc_find_value("key.word", &vnode); > > + if (vnode && xbc_node_is_array(vnode)) > > + xbc_array_for_each_value(vnode, value) { > > + printk("%s ", value); > > + } > > + > > +If you want to focus on keys which has a prefix string, you can use > > have OK. > > > +xbc_find_node() to find a node which prefix key words, and iterate > > [confusing above] Ah, it should be "to find a node by the prefix string," > > > +keys under the prefix node with xbc_node_for_each_key_value(). > > + > > +But the most typical usage is to get the named value under prefix > > +or get the named array under prefix as below:: > > + > > + root = xbc_find_node("key.prefix"); > > + value = xbc_node_find_value(root, "option", &vnode); > > + ... > > + xbc_node_for_each_array_value(root, "array-option", value, anode) { > > + ... > > + } > > + > > +This accesses a value of "key.prefix.option" and an array of > > +"key.prefix.array-option". > > + > > +Locking is not needed, since after initialized, the config becomes readonly. > > after initialization, OK. > > > +All data and keys must be copied if you need to modify it. > > + > > + > > +Functions and structures > > +======================== > > + > > +.. kernel-doc:: include/linux/bootconfig.h > > +.. kernel-doc:: lib/bootconfig.c > > + > > HTH. Thank you very much! > -- > ~Randy -- Masami Hiramatsu