1054 lines
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HTML
1054 lines
46 KiB
HTML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<title>Buildroot - Usage and documentation</title>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
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<link rel="stylesheet" type="text/css" href="stylesheet.css" />
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</head>
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<body>
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<div class="main">
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<div class="titre">
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<h1>Buildroot</h1>
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</div>
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<p><a href="http://buildroot.uclibc.org/">Buildroot</a>
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usage and documentation by Thomas Petazzoni. Contributions from
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Karsten Kruse, Ned Ludd, Martin Herren and others. </p>
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<p><small>$LastChangedDate$</small></p>
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<ul>
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<li><a href="#about">About Buildroot</a></li>
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<li><a href="#download">Obtaining Buildroot</a></li>
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<li><a href="#using">Using Buildroot</a></li>
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<li><a href="#custom_targetfs">Customizing the target filesystem</a></li>
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<li><a href="#custom_busybox">Customizing the Busybox
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configuration</a></li>
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<li><a href="#custom_uclibc">Customizing the uClibc
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configuration</a></li>
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<li><a href="#buildroot_innards">How Buildroot works</a></li>
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<li><a href="#using_toolchain">Using the uClibc toolchain</a></li>
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<li><a href="#toolchain_standalone">Using the uClibc toolchain
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outside of Buildroot</a></li>
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<li><a href="#downloaded_packages">Location of downloaded packages</a>
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</li>
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<li><a href="#add_software">Extending Buildroot with more
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Software</a></li>
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<li><a href="#links">Resources</a></li>
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</ul>
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<h2><a name="about" id="about"></a>About Buildroot</h2>
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<p>Buildroot is a set of Makefiles and patches that allow to easily
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generate both a cross-compilation toolchain and a root filesystem for your
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target. The cross-compilation toolchain uses uClibc (<a href=
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"http://www.uclibc.org/">http://www.uclibc.org/</a>), a tiny C standard
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library. </p>
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<p>Buildroot is useful mainly for people working with embedded systems.
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Embedded systems often use processors that are not the regular x86
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processors everyone is used to have on his PC. It can be PowerPC
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processors, MIPS processors, ARM processors, etc. </p>
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<p>A compilation toolchain is the set of tools that allows to
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compile code for your system. It consists of a compiler (in our
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case, <code>gcc</code>), binary utils like assembler and linker
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(in our case, <code>binutils</code>) and a C standard library (for
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example <a href="http://www.gnu.org/software/libc/libc.html">GNU
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Libc</a>, <a href="http://www.uclibc.org/">uClibc</a> or <a
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href="http://www.fefe.de/dietlibc/">dietlibc</a>). The system
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installed on your development station certainly already has a
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compilation toolchain that you can use to compile application that
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runs on your system. If you're using a PC, your compilation
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toolchain runs on an x86 processor and generates code for a x86
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processor. Under most Linux systems, the compilation toolchain
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uses the GNU libc as C standard library. This compilation
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toolchain is called the "host compilation toolchain", and more
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generally, the machine on which it is running, and on which you're
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working is called the "host system". The compilation toolchain
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is provided by your distribution, and Buildroot has nothing to do
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with it. </p>
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<p>As said above, the compilation toolchain that comes with your system
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runs and generates code for the processor of your host system. As your
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embedded system has a different processor, you need a cross-compilation
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toolchain: it's a compilation toolchain that runs on your host system but
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that generates code for your target system (and target processor). For
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example, if your host system uses x86 and your target system uses ARM, the
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regular compilation toolchain of your host runs on x86 and generates code
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for x86, while the cross-compilation toolchain runs on x86 and generates
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code for ARM. </p>
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<p>Even if your embedded system uses a x86 processor, you might interested
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in Buildroot, for two reasons:</p>
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<ul>
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<li>The compilation toolchain of your host certainly uses the GNU Libc
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which is a complete but huge C standard library. Instead of using GNU
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Libc on your target system, you can use uClibc which is a tiny C standard
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library. If you want to use this C library, then you need a compilation
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toolchain to generate binaries linked with it. Buildroot can do it for
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you. </li>
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<li>Buildroot automates the building of a root filesystem with all needed
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tools like busybox. It makes it much easier than doing it by hand. </li>
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</ul>
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<p>You might wonder why such a tool is needed when you can compile
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<code>gcc</code>, <code>binutils</code>, uClibc and all the tools by hand.
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Of course, doing so is possible. But dealing with all configure options,
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with all problems of every <code>gcc</code> or <code>binutils</code>
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version it very time-consuming and uninteresting. Buildroot automates this
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process through the use of Makefiles, and has a collection of patches for
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each <code>gcc</code> and <code>binutils</code> version to make them work
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on most architectures. </p>
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<h2><a name="download" id="download"></a>Obtaining Buildroot</h2>
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<p>Buildroot is available as daily SVN snapshots or directly using
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SVN. </p>
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<p>The latest snapshot is always available at <a
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href="http://buildroot.uclibc.org/downloads/snapshots/buildroot-snapshot.tar.bz2">http://buildroot.uclibc.org/downloads/snapshots/buildroot-snapshot.tar.bz2</a>,
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and previous snapshots are also available at <a
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href="http://buildroot.uclibc.org/downloads/snapshots/">http://buildroot.uclibc.org/downloads/snapshots/</a>. </p>
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<p>To download Buildroot using SVN, you can simply follow
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the rules described on the "Accessing SVN"-page (<a href=
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"http://buildroot.uclibc.org/subversion.html">http://buildroot.uclibc.org/subversion.html</a>)
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of the uClibc buildroot website (<a href=
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"http://buildroot.uclibc.org">http://buildroot.uclibc.org</a>), and download the
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<code>buildroot</code> SVN module. For the impatient, here's a quick
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recipe:</p>
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<pre>
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$ svn co svn://uclibc.org/trunk/buildroot
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</pre>
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<h2><a name="using" id="using"></a>Using Buildroot</h2>
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<p>Buildroot has a nice configuration tool similar to the one you can find
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in the Linux Kernel (<a href=
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"http://www.kernel.org/">http://www.kernel.org/</a>) or in Busybox
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(<a href="http://www.busybox.org/">http://www.busybox.org/</a>). Note that
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you can build everything as a normal user. There is no need to be root to
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configure and use Buildroot. The first step is to run the configuration
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assistant:</p>
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<pre>
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$ make menuconfig
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</pre>
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<p>For each entry of the configuration tool, you can find associated help
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that describes the purpose of the entry. </p>
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<p>One of the key configuration items is the <code>PROJECT</code> which
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determines where some board specific packages are built and where the
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results are stored. </p>
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<p>Once everything is configured, the configuration tool has generated a
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<code>.config</code> file that contains the description of your
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configuration. It will be used by the Makefiles to do what's needed. </p>
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<p>Let's go:</p>
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<pre>
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$ make
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</pre>
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<p>This command will download, configure and compile all the selected
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tools, and finally generate a target filesystem. The target filesystem will
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be named <code>root_fs_ARCH.EXT</code> where <code>ARCH</code> is your
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architecture and <code>EXT</code> depends on the type of target filesystem
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selected in the <code>Target options</code> section of the configuration
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tool.
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The file is stored in the "binaries/<code>$(PROJECT)</code>/" directory</p>
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<p>If you intend to do an offline-build and just want to download all
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sources that you previously selected in "make menuconfig" then
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issue:</p>
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<pre>
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$ make source
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</pre>
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<p>You can now disconnect or copy the content of your <code>dl</code>
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directory to the build-host. </p>
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<h3><a name="environment_variables" id="environment_variables"></a>
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Environment variables</h3>
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<p>Buildroot optionally honors some environment variables that are passed
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to <code>make</code> :</p>
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<ul>
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<li>HOSTCXX</li>
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<li>HOSTCC</li>
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<li>UCLIBC_CONFIG_FILE=<path/to/.config></li>
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<li>BUSYBOX_CONFIG_FILE=<path/to/.config></li>
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</ul>
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<p>An example that uses config files located in the toplevel directory and
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in your $HOME:</p>
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<pre>
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$ make UCLIBC_CONFIG_FILE=uClibc.config BUSYBOX_CONFIG_FILE=$HOME/bb.config
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</pre>
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<p>If you want to use a compiler other than the default <code>gcc</code>
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or <code>g++</code> for building helper-binaries on your host, then do</p>
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<pre>
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$ make HOSTCXX=g++-4.3-HEAD HOSTCC=gcc-4.3-HEAD
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</pre>
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<h3><a name="helper_completion" id="helper_completion"></a>
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Using auto-completion</h3>
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<p>If you are lazy enough that you don't want to type the entire <i>make
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menuconfig</i> command line, you can enable auto-completion in your shell.
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Here is how you can do that using <i>bash</i>:</p>
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<pre>
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$ complete -W menuconfig make
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</pre>
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<p>Then just enter the beginning of the line, and ask <i>bash</i> to
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complete it for you by pressing the <i>TAB</i> key:</p>
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<pre>
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$ make me<TAB>
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</pre>
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<p>will result in <i>bash</i> to append <i>nuconfig</i> for you!</p>
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<p>Alternatively, some distributions (of which Debian and Mandriva are but
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an example) have more powerful make completion. Depending on you
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distribution, you may have to install a package to enable completion. Under
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Mandriva, this is <i>bash-completion</i>, while Debian ships it as part of
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the <i>bash</i> package.</p>
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<p>Other shells, such as <i>zsh</i>, also have completion facilities. See
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the documentation for your shell.</p>
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<h2><a name="custom_targetfs" id="custom_targetfs"></a>Customizing the
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target filesystem</h2>
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<p>There are a few ways to customize the resulting target filesystem:</p>
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<ul>
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<li>Customize the target filesystem directly, and rebuild the image. The
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target filesystem is available under <code>project_build_ARCH/root/</code>
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where <code>ARCH</code> is the chosen target architecture.
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You can simply make your changes here, and run make afterwards, which will
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rebuild the target filesystem image. This method allows to do everything
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on the target filesystem, but if you decide to completely rebuild your
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toolchain and tools, these changes will be lost. </li>
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<li>Customize the target filesystem skeleton, available under
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<code>target/generic/target_skeleton/</code>. You can customize
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configuration files or other stuff here. However, the full file hierarchy
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is not yet present, because it's created during the compilation process.
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So you can't do everything on this target filesystem skeleton, but
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changes to it remain even if you completely rebuild the cross-compilation
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toolchain and the tools. <br />
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You can also customize the <code>target/generic/device_table.txt</code>
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file which is used by the tools that generate the target filesystem image
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to properly set permissions and create device nodes. The
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<code>target/generic/skel.tar.gz</code> file contains the main
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directories of a root filesystem and there is no obvious reason for which
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it should be changed. These main directories are in an tarball inside of
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inside the skeleton because it contains symlinks that would be broken
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otherwise. <br />
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These customizations are deployed into
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<code>project_build_ARCH/root/</code> just before the actual image
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is made. So simply rebuilding the image by running
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make should propagate any new changes to the image. </li>
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<li>When configuring the build system, using <code>make menuconfig</code>,
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you can specify the contents of the /etc/hostname and /etc/issue
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(the welcome banner) in the <code>PROJECT</code> section</li>
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</ul>
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<h2><a name="custom_busybox" id="custom_busybox"></a>Customizing the
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Busybox configuration</h2>
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<p><a href="http://www.busybox.net/">Busybox</a> is very configurable, and
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you may want to customize it. You can
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follow these simple steps to do it. It's not an optimal way, but it's
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simple and it works. </p>
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<ol>
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<li>Make a first compilation of buildroot with busybox without trying to
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customize it. </li>
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<li>Invoke <code>make busybox-menuconfig</code>.
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The nice configuration tool appears and you can
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customize everything. </li>
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<li>Run the compilation of buildroot again. </li>
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</ol>
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<p>Otherwise, you can simply change the
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<code>package/busybox/busybox-<version>.config</code> file if you
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know the options you want to change without using the configuration tool.
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</p>
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<p>If you want to use an existing config file for busybox, then see
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section <a href="#environment_variables">environment variables</a>. </p>
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<h2><a name="custom_uclibc" id="custom_uclibc"></a>Customizing the uClibc
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configuration</h2>
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<p>Just like <a href="#custom_busybox">BusyBox</a>, <a
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href="http://www.uclibc.org/">uClibc</a> offers a lot of
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configuration options. They allow to select various
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functionalities, depending on your needs and limitations. </p>
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<p>The easiest way to modify the configuration of uClibc is to
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follow these steps :</p>
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<ol>
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<li>Make a first compilation of buildroot without trying to
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customize uClibc. </li>
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<li>Invoke <code>make uclibc-menuconfig</code>.
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The nice configuration assistant, similar to
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the one used in the Linux Kernel or in Buildroot appears. Make
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your configuration as appropriate. </li>
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<li>Copy the <code>.config</code> file to
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<code>toolchain/uClibc/uClibc.config</code> or
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<code>toolchain/uClibc/uClibc.config-locale</code>. The former
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is used if you haven't selected locale support in Buildroot
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configuration, and the latter is used if you have selected
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locale support. </li>
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<li>Run the compilation of Buildroot again</li>
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</ol>
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<p>Otherwise, you can simply change
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<code>toolchain/uClibc/uClibc.config</code> or
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<code>toolchain/uClibc/uClibc.config-locale</code> without running
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the configuration assistant. </p>
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<p>If you want to use an existing config file for uclibc, then see
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section <a href="#environment_variables">environment variables</a>. </p>
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<h2><a name="buildroot_innards" id="buildroot_innards"></a>How Buildroot
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works</h2>
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<p>As said above, Buildroot is basically a set of Makefiles that download,
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configure and compiles software with the correct options. It also includes
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some patches for various software, mainly the ones involved in the
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cross-compilation tool chain (<code>gcc</code>, <code>binutils</code> and
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uClibc). </p>
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<p>There is basically one Makefile per software, and they are named with
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the <code>.mk</code> extension. Makefiles are split into four
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sections:</p>
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<ul>
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<li><b>project</b> (in the <code>project/</code> directory) contains
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the Makefiles and associated files for all software related to the
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building several root file systems in the same buildroot tree. </li>
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<li><b>toolchain</b> (in the <code>toolchain/</code> directory) contains
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the Makefiles and associated files for all software related to the
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cross-compilation toolchain : <code>binutils</code>, <code>ccache</code>,
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<code>gcc</code>, <code>gdb</code>, <code>kernel-headers</code> and
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<code>uClibc</code>. </li>
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<li><b>package</b> (in the <code>package/</code> directory) contains the
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Makefiles and associated files for all user-space tools that Buildroot
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can compile and add to the target root filesystem. There is one
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sub-directory per tool. </li>
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<li><b>target</b> (in the <code>target</code> directory) contains the
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Makefiles and associated files for software related to the generation of
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the target root filesystem image. Four types of filesystems are supported
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: ext2, jffs2, cramfs and squashfs. For each of them, there's a
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sub-directory with the required files. There is also a
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<code>default/</code> directory that contains the target filesystem
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skeleton. </li>
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</ul>
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<p>Each directory contains at least 2 files :</p>
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<ul>
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<li><code>something.mk</code> is the Makefile that downloads, configures,
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compiles and installs the software <code>something</code>. </li>
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<li><code>Config.in</code> is a part of the configuration tool
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description file. It describes the option related to the current
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software. </li>
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</ul>
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<p>The main Makefile do the job through the following steps (once the
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configuration is done):</p>
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<ol>
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<li>Create the download directory (<code>dl/</code> by default). This is
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where the tarballs will be downloaded. It is interesting to know that the
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tarballs are in this directory because it may be useful to save them
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somewhere to avoid further downloads. </li>
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<li>Create the shared build directory (<code>build_ARCH/</code> by
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default, where <code>ARCH</code> is your architecture). This is where all
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non configurable user-space tools will be compiled.When building two or
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more targets using the same architecture, the first build will go through
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the full download, configure, make process, but the second and later
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builds will only copy the result from the first build to its project
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specific target directory significantly speeding up the build process</li>
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<li>Create the project specific build directory
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(<code>project_build_ARCH/$(PROJECT)</code> by default, where
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<code>ARCH</code> is your architecture). This is where all configurable
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user-space tools will be compiled. The project specific build directory
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is neccessary, if two different targets needs to use a specific package,
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but the packages have different configuration for both targets. Some
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examples of packages built in this directory are busybox and linux.
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</li>
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<li>Create the project specific result directory
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(<code>binaries/$(PROJECT)</code> by default, where <code>ARCH</code>
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is your architecture). This is where the root filesystem images are
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stored, It is also used to store the linux kernel image and any
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utilities, boot-loaders etc. needed for a target.
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</li>
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<li>Create the toolchain build directory
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(<code>toolchain_build_ARCH/</code> by default, where <code>ARCH</code>
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is your architecture). This is where the cross compilation toolchain will
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be compiled. </li>
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<li>Setup the staging directory (<code>build_ARCH/staging_dir/</code> by
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default). This is where the cross-compilation toolchain will be
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installed. If you want to use the same cross-compilation toolchain for
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other purposes, such as compiling third-party applications, you can add
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<code>build_ARCH/staging_dir/usr/bin</code> to your PATH, and then use
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<code>arch-linux-gcc</code> to compile your application. In order to
|
|
setup this staging directory, it first removes it, and then it creates
|
|
various subdirectories and symlinks inside it. </li>
|
|
|
|
<li>Create the target directory (<code>project_build_ARCH/root/</code> by
|
|
default) and the target filesystem skeleton. This directory will contain
|
|
the final root filesystem. To setup it up, it first deletes it, then it
|
|
uncompress the <code>target/generic/skel.tar.gz</code> file to create the
|
|
main subdirectories and symlinks, copies the skeleton available in
|
|
<code>target/generic/target_skeleton</code> and then removes useless
|
|
<code>.svn/</code> directories. </li>
|
|
|
|
<li>Add the <code>TARGETS</code> dependency. This should generally check
|
|
if the configuration option for this package is enabled, and if so then
|
|
"subscribe" this package to be compiled by adding it to the
|
|
TARGETS global variable. </li>
|
|
</ol>
|
|
|
|
<h2><a name="multi_project" id="multi_project"></a>Building several
|
|
projects in the same buildroot source tree</h2>
|
|
|
|
<p><b>BACKGROUND</b></p>
|
|
|
|
<p>Buildroot has always supported building several projects in the same
|
|
tree if each project was for a different architecture. </p>
|
|
|
|
<p>The root file system has been created in the
|
|
<code>"build_<ARCH>/root"</code>
|
|
directory which is unique for each architecture.
|
|
Toolchains have been built in
|
|
<code>"toolchain_build_<ARCH>"</code>. </p>
|
|
|
|
<p> It the user wanted to build several root file systems for the same
|
|
architecture, a prefix or suffix could be added in the configuration file
|
|
so the root file system would be built in
|
|
<code>"<PREFIX>_build_<ARCH>_<SUFFIX>/root"</code>
|
|
By supplying <u>unique</u> combinations of
|
|
<code>"<PREFIX>"</code> and
|
|
<code>"<SUFFIX>"</code>
|
|
each project would get a <u>unique</u> root file system tree. </p>
|
|
|
|
<p>The disadvantage of this approach is that a new toolchain was
|
|
built for each project, adding considerable time to the build
|
|
process, even if it was two projects for the same chip. </p>
|
|
|
|
<p>This drawback has been somewhat lessened with
|
|
<code>gcc-4.x.y</code> which allows buildroot to use an external
|
|
toolchain. Certain packages requires special
|
|
features in the toolchain, and if an external toolchain is selected,
|
|
this may lack the neccessary features to complete the build of the root
|
|
file system.</p>
|
|
|
|
<p>A bigger problem was that the
|
|
<code>"build_<ARCH>"</code> tree
|
|
was also duplicated, so each </code>package</code> would also
|
|
be rebuilt once per project, resulting in even longer build times.</p>
|
|
|
|
|
|
<p><b>PROJECT TO SHARE TOOLCHAIN AND PACKAGE BUILDS</b></p>
|
|
|
|
<p>Work has started on a project which will allow the user to build
|
|
multiple root file systems for the same architecture in the same tree.
|
|
The toolchain and the package build directory will be shared, but each
|
|
project will have a dedicated directory tree for project specific
|
|
builds. </p>
|
|
|
|
<p>With this approach, most, if not all packages will be compiled
|
|
when the first project is built.
|
|
The process is almost identical to the original process.
|
|
Packages are downloaded and extracted to the shared
|
|
<code>"build_<ARCH>/<package>"</code>
|
|
directory. They are configured and compiled. </p>
|
|
|
|
<p>Package libraries and headers are installed in the shared $(STAGING_DIR),
|
|
and then the project specific root file system "$(TARGET_DIR)"
|
|
is populated. </p>
|
|
|
|
<p>At the end of the build, the root file system will be used
|
|
to generate the resulting root file system binaries. </p>
|
|
|
|
<p>Once the first project has been built, building other projects will
|
|
typically involve populating the new project's root file system directory
|
|
from the existing binaries generated in the shared
|
|
<code>"build_<ARCH>/<>"</code> directory. </p>
|
|
|
|
<p>Only packages, not used by the first project, will have to go
|
|
through the normal extract-configure-compile flow. </p>
|
|
|
|
<p><b>IMPLEMENTATION</b></p>
|
|
|
|
<p>The core of the solution is the introduction
|
|
of two new directories: </p>
|
|
|
|
<ul>
|
|
<li><code>project_build_<ARCH></code></li>
|
|
|
|
<li><code>binaries;</code></li>
|
|
</ul>
|
|
|
|
<p>Each of the directories contain one subdirectory per project.
|
|
The name of the subdirectory is configured by the user in the
|
|
normal buildroot configuration, using the value of: </p>
|
|
|
|
<p><code>Project Options ---> Project name</code></p>
|
|
|
|
<p>The configuration defines the $(PROJECT) variable.</p>
|
|
|
|
<p>The default project name is <code>"uclibc"</code>.</p>
|
|
|
|
<p><code>"package/Makefile.in"</code> defines:
|
|
<pre>
|
|
<code>PROJECT_BUILD_DIR:=project_build_$(ARCH)/$(PROJECT)</code>
|
|
<code>BINARIES_DIR:=binaries/$(PROJECT)</code>
|
|
</pre>
|
|
</p>
|
|
|
|
<p>It also defines the location for the target root file system:
|
|
<pre>
|
|
<code>TARGET_DIR:=$(PROJECT_BUILD_DIR)/$(PROJECT)/root</code>
|
|
</pre>
|
|
</p>
|
|
|
|
<p>I.E: If the user has choosen
|
|
<code>"myproject"</code>
|
|
as the $(PROJECT) name:
|
|
|
|
<ul>
|
|
<li><code>"project_build_<ARCH>/myproject"</code></li>
|
|
<li><code>"binaries/myproject"</code></li>
|
|
</ul>
|
|
|
|
<p>will be created. </p>
|
|
|
|
<p>Currently, the <u>root file system</u>, <u>busybox</u> and an Atmel
|
|
customized version of
|
|
<u><code>U-Boot</code></u>, as well as some Atmel specific
|
|
bootloaders like <u>at91-bootstrap</u> and <u>dataflashboot.bin</u>
|
|
are built in
|
|
<code>"$(PROJECT_BUILD_DIR)"</code>
|
|
|
|
<p>The resulting binaries for all architectures are stored in the
|
|
<code>"$(BINARIES_DIR)"</code> directory. <p>
|
|
|
|
<p><b>SUMMARY</b></p>
|
|
|
|
<p>The project will share directories which can be share without
|
|
conflicts, but will use unique build directories, where the user
|
|
can configure the build. </p>
|
|
|
|
<p><b>THINGS TO DO</b></p>
|
|
|
|
<ol>
|
|
|
|
<li>Linux</li>
|
|
|
|
<p>The current Linux implementation is flawed. It only works
|
|
if the user chooses to use one of the few kernels selected
|
|
as base for the kernel-headers. While the Makefile seems to have
|
|
hooks, allowing the developer to specify whatever version he/she
|
|
wants in the target/device/*/* Makefiles, the build will fail
|
|
if another kernel version is choosen.</p>
|
|
|
|
<p>The reason for this is that the kernel patches are not
|
|
applied by the <code>"target/linux/linux.mk"</code>
|
|
build script fragment. They are only applied by the
|
|
<code>"toolchain/kernel-headers/*.makefile"</code>
|
|
build script fragments</p>
|
|
|
|
<p>If the kernel-header version and the linux version differs,
|
|
there will be two <code>"linux-2.6.X.Y"</code>
|
|
directories in
|
|
<code>"build_<ARCH>/<>"</code>,
|
|
each with its own set of patches. </p>
|
|
|
|
<p>The solution in the works, is to move the build of Linux to
|
|
<code>"project_build_<ARCH>/<project name>/linux-2.6.X.Y"</code> combined with method to configure
|
|
which patches can be applied. Possibly, the linux source tree
|
|
used to generate the kernel headers will be moved to the
|
|
<code>"toolchain_build_<ARCH>"</code>
|
|
directory
|
|
</p>
|
|
|
|
<p>The user will be able to select from three different
|
|
Linux strategies:
|
|
|
|
<ul>
|
|
<li>Conservative Strategy: Only use version ssupported by the kernel headers</li>
|
|
<li>Stable Linux Strategy: Allow any 2.6.X.Y combination.
|
|
(Minimum 2.6.19)</li>
|
|
<li>Power-User Strategy: Allow
|
|
<code>"-git"</code>, or
|
|
<code>"-mm"</code>, or user downloadable kernels</li>
|
|
</ul>
|
|
|
|
<p>The current kernel patches can be configured to be applied to the
|
|
linux source tree even if the version differs from the
|
|
kernel header version. </p>
|
|
|
|
<p>Since the user can select any kernel-patch
|
|
he/she will be able to select a non-working combination.
|
|
If the patch fails, the user will have to generate a new
|
|
proprietary kernel-patch or decide to not apply the kernel
|
|
patches</p>
|
|
|
|
<p>Other optional patches will be <u>board specific</u> or
|
|
<u>architecture specific</u> patches. </p>
|
|
|
|
<p>There will also be a way for the user to supply absolute
|
|
or relative paths to patches, possibly outside the main tree.
|
|
This can be used to apply custom kernel-header-patches, if
|
|
the versions available in buildroot cannot be applied to the
|
|
specific linux version used</p>
|
|
|
|
<p>Maybe, there will also be a possibility to supply an
|
|
<code>"URL"</code> to a patch available on Internet. </p>
|
|
|
|
<li>Configurable packages</li>
|
|
|
|
<p>Many packages can, on top of the simple
|
|
"enable/disable build",
|
|
be further configured using Kconfig.
|
|
Currently these packages will be compiled using the
|
|
configuration specified in the
|
|
<code>".config"</code> file of the <u>first</u>
|
|
project demanding the build of the package.</p>
|
|
|
|
<p>If <u>another</u> project uses the same packages, but with
|
|
a different configuration,these packages will <u>not</u> be rebuilt,
|
|
and the root file system for the new project will be populated
|
|
with files from the build of the <u>first</u> project</p>
|
|
|
|
<p>If multiple project are built, and a specific package
|
|
needs two different configuration, then the user must
|
|
delete the package from the
|
|
<code>"build_<ARCH>"</code> directory
|
|
before rebuilding the new project.<p>
|
|
|
|
<p>A long term solution is to edit the package makefile and move
|
|
the build of the configurable packages from
|
|
<code>"build_<ARCH>"</code> to
|
|
<code>"project_build_<ARCH>/<project name>"</code>
|
|
and send a patch to the buildroot mailing list.
|
|
|
|
<li>Naming conventions</li>
|
|
|
|
<p>Names of resulting binaries should reflect the
|
|
"project name"
|
|
|
|
<li>Generating File System binaries</li>
|
|
<p>
|
|
Packages which needs to be installed with the "root"
|
|
as owner, will generate a
|
|
<code>".fakeroot.<package>"</code> file
|
|
which will be used for the final build of the root file system binary. </p>
|
|
|
|
<p>This was previously located in the
|
|
<code>"$(STAGING_DIR)"</code> directory, but was
|
|
recently moved to the
|
|
<code>"$(PROJECT_BUILD_DIR)"</code> directory. </p>
|
|
|
|
<p>Currently only three packages:
|
|
<code>"at"</code>,
|
|
<code>"ltp-testsuite"</code> and
|
|
<code>"nfs-utils"</code>
|
|
requests fakeroot. <p>
|
|
|
|
<p>The makefile fragments for each file system type like
|
|
<code>"ext2"</code>,
|
|
<code>"jffs2"</code> or
|
|
<code>"squashfs"</code>
|
|
will, when the file system binary is generated,
|
|
collect all present
|
|
<code>".fakeroot.<package>"</code> files
|
|
to a single <code>"_fakeroot.<file system>"</code>
|
|
file and call fakeroot.</p>
|
|
<code>".fakeroot.<package>"</code>
|
|
files are deleted as the last action of the Buildroot Makefile. </p>
|
|
|
|
<p>It needs to be evaluated if any further action for the
|
|
file system binary build is needed. </p>
|
|
|
|
</ol>
|
|
|
|
<h2><a name="using_toolchain" id="using_toolchain"></a>Using the
|
|
uClibc toolchain</h2>
|
|
|
|
<p>You may want to compile your own programs or other software
|
|
that are not packaged in Buildroot. In order to do this, you can
|
|
use the toolchain that was generated by Buildroot. </p>
|
|
|
|
<p>The toolchain generated by Buildroot by default is located in
|
|
<code>build_ARCH/staging_dir/</code>. The simplest way to use it
|
|
is to add <code>build_ARCH/staging_dir/usr/bin/</code> to your PATH
|
|
environnement variable, and then to use
|
|
<code>arch-linux-gcc</code>, <code>arch-linux-objdump</code>,
|
|
<code>arch-linux-ld</code>, etc. </p>
|
|
|
|
<p>For example, you may add the following to your
|
|
<code>.bashrc</code> (considering you're building for the MIPS
|
|
architecture and that Buildroot is located in
|
|
<code>~/buildroot/</code>) :</p>
|
|
|
|
<pre>
|
|
export PATH="$PATH:~/buildroot/build_mips/staging_dir/usr/bin/"
|
|
</pre>
|
|
|
|
<p>Then you can simply do :</p>
|
|
|
|
<pre>
|
|
mips-linux-gcc -o foo foo.c
|
|
</pre>
|
|
|
|
<p><b>Important</b> : do not try to move a gcc-3.x toolchain to an other
|
|
directory, it won't work. There are some hardcoded paths in the
|
|
<i>gcc</i> configuration. If the default toolchain directory
|
|
doesn't suit your needs, please refer to the <a
|
|
href="#toolchain_standalone">Using the uClibc toolchain outside of
|
|
buildroot</a> section. </p>
|
|
<p>If you are using a current gcc-4.x, then use --sysroot and -isysroot
|
|
since these toolchains have fully functional sysroot support. No
|
|
hardcoded paths do exist in these configurations. </p>
|
|
|
|
<h2><a name="toolchain_standalone" id="toolchain_standalone"></a>Using the
|
|
uClibc toolchain outside of buildroot</h2>
|
|
|
|
<p>By default, the cross-compilation toolchain is generated inside
|
|
<code>build_ARCH/staging_dir/</code>. But sometimes, it may be useful to
|
|
install it somewhere else, so that it can be used to compile other programs
|
|
or by other users. Moving the <code>build_ARCH/staging_dir/</code>
|
|
directory elsewhere is <b>not possible if using gcc-3.x</b>, because there
|
|
are some hardcoded paths in the toolchain configuration. This works, thanks
|
|
to sysroot support, with current, stable gcc-4.x toolchains, of course. </p>
|
|
|
|
<p>If you want to use the generated gcc-3.x toolchain for other purposes,
|
|
you can configure Buildroot to generate it elsewhere using the
|
|
option of the configuration tool : <code>Build options ->
|
|
Toolchain and header file location</code>, which defaults to
|
|
<code>$(BUILD_DIR)/staging_dir/</code>. </p>
|
|
|
|
<h2><a name="downloaded_packages"
|
|
id="downloaded_packages"></a>Location of downloaded packages</h2>
|
|
|
|
<p>It might be useful to know that the various tarballs that are
|
|
downloaded by the <i>Makefiles</i> are all stored in the
|
|
<code>DL_DIR</code> which by default is the <code>dl</code>
|
|
directory. It's useful for example if you want to keep a complete
|
|
version of Buildroot which is know to be working with the
|
|
associated tarballs. This will allow you to regenerate the
|
|
toolchain and the target filesystem with exactly the same
|
|
versions. </p>
|
|
|
|
<p>If you maintain several buildroot trees, it might be better to have
|
|
a shared download location. This can be accessed by creating a symbolic link
|
|
from the <code>dl</code> directory to the shared download location. </p>
|
|
|
|
<p>I.E:</p>
|
|
|
|
<pre>
|
|
ln -s <shared download location> dl
|
|
</pre>
|
|
|
|
<p>Another way of accessing a shared download location is to
|
|
create the <code>BUILDROOT_DL_DIR</code> environment variable.
|
|
If this is set, then the value of DL_DIR in the project is
|
|
overridden. The following line should be added to
|
|
<code>"~/.bashrc"</code>. <p>
|
|
|
|
<pre>
|
|
export BUILDROOT_DL_DIR <shared download location>
|
|
</pre>
|
|
|
|
|
|
|
|
<h2><a name="add_software" id="add_software"></a>Extending Buildroot with
|
|
more software</h2>
|
|
|
|
<p>This section will only consider the case in which you want to
|
|
add user-space software. </p>
|
|
|
|
<h3>Package directory</h3>
|
|
|
|
<p>First of all, create a directory under the <code>package</code>
|
|
directory for your software, for example <code>foo</code>. </p>
|
|
|
|
<h3><code>Config.in</code> file</h3>
|
|
|
|
<p>Then, create a file named <code>Config.in</code>. This file
|
|
will contain the portion of options description related to our
|
|
<code>foo</code> software that will be used and displayed in the
|
|
configuration tool. It should basically contain :</p>
|
|
|
|
<pre>
|
|
config BR2_PACKAGE_FOO
|
|
bool "foo"
|
|
default n
|
|
help
|
|
This is a comment that explains what foo is.
|
|
|
|
http://foosoftware.org/foo/
|
|
</pre>
|
|
|
|
<p>Of course, you can add other options to configure particular
|
|
things in your software. </p>
|
|
|
|
<h3>The real <i>Makefile</i></h3>
|
|
|
|
<p>Finally, here's the hardest part. Create a file named
|
|
<code>foo.mk</code>. It will contain the <i>Makefile</i> rules that
|
|
are in charge of downloading, configuring, compiling and installing
|
|
the software. Below is an example that we will comment
|
|
afterwards. </p>
|
|
|
|
<pre>
|
|
<a name="line1" id="line1">1</a> #############################################################
|
|
<a name="line2" id="line2">2</a> #
|
|
<a name="line3" id="line3">3</a> # foo
|
|
<a name="line4" id="line4">4</a> #
|
|
<a name="line5" id="line5">5</a> #############################################################
|
|
<a name="line6" id="line6">6</a> FOO_VERSION:=1.0
|
|
<a name="line7" id="line7">7</a> FOO_SOURCE:=foo-$(FOO_VERSION).tar.gz
|
|
<a name="line8" id="line8">8</a> FOO_SITE:=http://www.foosoftware.org/downloads
|
|
<a name="line9" id="line9">9</a> FOO_DIR:=$(BUILD_DIR)/foo-$(FOO_VERSION)
|
|
<a name="line10" id="line10">10</a> FOO_BINARY:=foo
|
|
<a name="line11" id="line11">11</a> FOO_TARGET_BINARY:=usr/bin/foo
|
|
<a name="line12" id="line12">12</a>
|
|
<a name="line13" id="line13">13</a> $(DL_DIR)/$(FOO_SOURCE):
|
|
<a name="line14" id="line14">14</a> $(WGET) -P $(DL_DIR) $(FOO_SITE)/$(FOO_SOURCE)
|
|
<a name="line15" id="line15">15</a>
|
|
<a name="line16" id="line16">16</a> $(FOO_DIR)/.source: $(DL_DIR)/$(FOO_SOURCE)
|
|
<a name="line17" id="line17">17</a> $(ZCAT) $(DL_DIR)/$(FOO_SOURCE) | tar -C $(BUILD_DIR) $(TAR_OPTIONS) -
|
|
<a name="line18" id="line18">18</a> touch $@
|
|
<a name="line19" id="line19">19</a>
|
|
<a name="line20" id="line20">20</a> $(FOO_DIR)/.configured: $(FOO_DIR)/.source
|
|
<a name="line21" id="line21">21</a> (cd $(FOO_DIR); rm -rf config.cache ; \
|
|
<a name="line22" id="line22">22</a> $(TARGET_CONFIGURE_OPTS) \
|
|
<a name="line23" id="line23">23</a> CFLAGS="$(TARGET_CFLAGS)" \
|
|
<a name="line24" id="line24">24</a> ./configure \
|
|
<a name="line25" id="line25">25</a> --target=$(GNU_TARGET_NAME) \
|
|
<a name="line26" id="line26">26</a> --host=$(GNU_TARGET_NAME) \
|
|
<a name="line27" id="line27">27</a> --build=$(GNU_HOST_NAME) \
|
|
<a name="line28" id="line28">28</a> --prefix=/usr \
|
|
<a name="line29" id="line29">29</a> --sysconfdir=/etc \
|
|
<a name="line30" id="line30">30</a> );
|
|
<a name="line31" id="line31">31</a> touch $@
|
|
<a name="line32" id="line32">32</a>
|
|
<a name="line33" id="line33">33</a> $(FOO_DIR)/$(FOO_BINARY): $(FOO_DIR)/.configured
|
|
<a name="line34" id="line34">34</a> $(MAKE) CC=$(TARGET_CC) -C $(FOO_DIR)
|
|
<a name="line35" id="line35">35</a>
|
|
<a name="line36" id="line36">36</a> $(TARGET_DIR)/$(FOO_TARGET_BINARY): $(FOO_DIR)/$(FOO_BINARY)
|
|
<a name="line37" id="line37">37</a> $(MAKE) prefix=$(TARGET_DIR)/usr -C $(FOO_DIR) install
|
|
<a name="line38" id="line38">38</a> rm -Rf $(TARGET_DIR)/usr/man
|
|
<a name="line39" id="line39">39</a>
|
|
<a name="line40" id="line40">40</a> foo: uclibc ncurses $(TARGET_DIR)/$(FOO_TARGET_BINARY)
|
|
<a name="line41" id="line41">41</a>
|
|
<a name="line42" id="line42">42</a> foo-source: $(DL_DIR)/$(FOO_SOURCE)
|
|
<a name="line43" id="line43">43</a>
|
|
<a name="line44" id="line44">44</a> foo-clean:
|
|
<a name="line45" id="line45">45</a> $(MAKE) prefix=$(TARGET_DIR)/usr -C $(FOO_DIR) uninstall
|
|
<a name="line46" id="line46">46</a> -$(MAKE) -C $(FOO_DIR) clean
|
|
<a name="line47" id="line47">47</a>
|
|
<a name="line48" id="line48">48</a> foo-dirclean:
|
|
<a name="line49" id="line49">49</a> rm -rf $(FOO_DIR)
|
|
<a name="line50" id="line50">50</a>
|
|
<a name="line51" id="line51">51</a> #############################################################
|
|
<a name="line52" id="line52">52</a> #
|
|
<a name="line53" id="line53">53</a> # Toplevel Makefile options
|
|
<a name="line54" id="line54">54</a> #
|
|
<a name="line55" id="line55">55</a> #############################################################
|
|
<a name="line56" id="line56">56</a> ifeq ($(strip $(BR2_PACKAGE_FOO)),y)
|
|
<a name="line57" id="line57">57</a> TARGETS+=foo
|
|
<a name="line58" id="line58">58</a> endif
|
|
|
|
</pre>
|
|
|
|
<p>First of all, this <i>Makefile</i> example works for a single
|
|
binary software. For other software such as libraries or more
|
|
complex stuff with multiple binaries, it should be adapted. Look at
|
|
the other <code>*.mk</code> files in the <code>package</code>
|
|
directory. </p>
|
|
|
|
<p>At lines <a href="#line6">6-11</a>, a couple of useful variables are
|
|
defined :</p>
|
|
|
|
<ul>
|
|
|
|
<li><code>FOO_VERSION</code> : The version of <i>foo</i> that
|
|
should be downloaded. </li>
|
|
|
|
<li><code>FOO_SOURCE</code> : The name of the tarball of
|
|
<i>foo</i> on the download website of FTP site. As you can see
|
|
<code>FOO_VERSION</code> is used. </li>
|
|
|
|
<li><code>FOO_SITE</code> : The HTTP or FTP site from which
|
|
<i>foo</i> archive is downloaded. It must include the complete
|
|
path to the directory where <code>FOO_SOURCE</code> can be
|
|
found. </li>
|
|
|
|
<li><code>FOO_DIR</code> : The directory into which the software
|
|
will be configured and compiled. Basically, it's a subdirectory
|
|
of <code>BUILD_DIR</code> which is created upon decompression of
|
|
the tarball. </li>
|
|
|
|
<li><code>FOO_BINARY</code> : Software binary name. As said
|
|
previously, this is an example for a single binary software. </li>
|
|
|
|
<li><code>FOO_TARGET_BINARY</code> : The full path of the binary
|
|
inside the target filesystem. </li>
|
|
|
|
</ul>
|
|
|
|
<p>Lines <a href="#line13">13-14</a> defines a target that downloads the
|
|
tarball from the remote site to the download directory
|
|
(<code>DL_DIR</code>). </p>
|
|
|
|
<p>Lines <a href="#line16">16-18</a> defines a target and associated rules
|
|
that uncompress the downloaded tarball. As you can see, this target
|
|
depends on the tarball file, so that the previous target (line
|
|
<a href="#line13">13-14</a>) is called before executing the rules of the
|
|
current target. Uncompressing is followed by <i>touching</i> a hidden file
|
|
to mark the software has having been uncompressed. This trick is
|
|
used everywhere in Buildroot <i>Makefile</i> to split steps
|
|
(download, uncompress, configure, compile, install) while still
|
|
having correct dependencies. </p>
|
|
|
|
<p>Lines <a href="#line20">20-31</a> defines a target and associated rules
|
|
that configures the software. It depends on the previous target (the
|
|
hidden <code>.source</code> file) so that we are sure the software has
|
|
been uncompressed. In order to configure it, it basically runs the
|
|
well-known <code>./configure</code> script. As we may be doing
|
|
cross-compilation, <code>target</code>, <code>host</code> and
|
|
<code>build</code> arguments are given. The prefix is also set to
|
|
<code>/usr</code>, not because the software will be installed in
|
|
<code>/usr</code> on your host system, but in the target
|
|
filesystem. Finally it creates a <code>.configured</code> file to
|
|
mark the software as configured. </p>
|
|
|
|
<p>Lines <a href="#line33">33-34</a> defines a target and a rule that
|
|
compiles the software. This target will create the binary file in the
|
|
compilation directory, and depends on the software being already
|
|
configured (hence the reference to the <code>.configured</code>
|
|
file). It basically runs <code>make</code> inside the source
|
|
directory. </p>
|
|
|
|
<p>Lines <a href="#line36">36-38</a> defines a target and associated rules
|
|
that install the software inside the target filesystem. It depends on the
|
|
binary file in the source directory, to make sure the software has
|
|
been compiled. It uses the <code>install</code> target of the
|
|
software <code>Makefile</code> by passing a <code>prefix</code>
|
|
argument, so that the <code>Makefile</code> doesn't try to install
|
|
the software inside host <code>/usr</code> but inside target
|
|
<code>/usr</code>. After the installation, the
|
|
<code>/usr/man</code> directory inside the target filesystem is
|
|
removed to save space. </p>
|
|
|
|
<p>Line <a href="#line40">40</a> defines the main target of the software,
|
|
the one that will be eventually be used by the top level
|
|
<code>Makefile</code> to download, compile, and then install
|
|
this package. This target should first of all depends on all
|
|
needed dependecies of the software (in our example,
|
|
<i>uclibc</i> and <i>ncurses</i>), and also depend on the
|
|
final binary. This last dependency will call all previous
|
|
dependencies in the correct order. </p>
|
|
|
|
<p>Line <a href="#line42">42</a> defines a simple target that only
|
|
downloads the code source. This is not used during normal operation of
|
|
Buildroot, but is needed if you intend to download all required sources at
|
|
once for later offline build. Note that if you add a new package providing
|
|
a <code>foo-source</code> target is <i>mandatory</i> to support
|
|
users that wish to do offline-builds. Furthermore it eases checking
|
|
if all package-sources are downloadable. </p>
|
|
|
|
<p>Lines <a href="#line44">44-46</a> define a simple target to clean the
|
|
software build by calling the <i>Makefiles</i> with the appropriate option.
|
|
The <code>-clean</code> target should run <code>make clean</code>
|
|
on $(BUILD_DIR)/package-version and MUST uninstall all files of the
|
|
package from $(STAGING_DIR) and from $(TARGET_DIR). </p>
|
|
|
|
<p>Lines <a href="#line48">48-49</a> define a simple target to completely
|
|
remove the directory in which the software was uncompressed, configured and
|
|
compiled. The <code>-dirclean</code> target MUST completely rm $(BUILD_DIR)/
|
|
package-version. </p>
|
|
|
|
<p>Lines <a href="#line51">51-58</a> adds the target <code>foo</code> to
|
|
the list of targets to be compiled by Buildroot by first checking if
|
|
the configuration option for this package has been enabled
|
|
using the configuration tool, and if so then "subscribes"
|
|
this package to be compiled by adding it to the TARGETS
|
|
global variable. The name added to the TARGETS global
|
|
variable is the name of this package's target, as defined on
|
|
line <a href="#line40">40</a>, which is used by Buildroot to download,
|
|
compile, and then install this package. </p>
|
|
|
|
|
|
<h3>Conclusion</h3>
|
|
|
|
<p>As you can see, adding a software to buildroot is simply a
|
|
matter of writing a <i>Makefile</i> using an already existing
|
|
example and to modify it according to the compilation process of
|
|
the software. </p>
|
|
|
|
<p>If you package software that might be useful for other persons,
|
|
don't forget to send a patch to Buildroot developers !</p>
|
|
|
|
<h2><a name="links" id="links"></a>Resources</h2>
|
|
|
|
<p>To learn more about Buildroot you can visit these
|
|
websites:</p>
|
|
|
|
<ul>
|
|
<li><a href="http://www.uclibc.org/">http://www.uclibc.org/</a></li>
|
|
<li><a href="http://www.busybox.net/">http://www.busybox.net/</a></li>
|
|
</ul>
|
|
|
|
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|
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