path: root/documentation/poky-ref-manual/development.xml

<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">

<chapter id="platdev">
<title>Platform Development with Poky</title>

    <section id="platdev-appdev">
    <title>Software development</title>
    <para>
        Poky supports several methods of software development. You can use the method that is 
        best for you.  This chapter describes each development method.
    </para>

        <section id="platdev-appdev-external-sdk">
        <title>External Development Using the Poky SDK</title>
        <para>
            The meta-toolchain and meta-toolchain-sdk targets build tarballs that contain toolchains and 
            libraries suitable for application development outside of Poky. 
            For information on these targets see the <ulink linkend='ref-images'>Reference: Images</ulink>
            appendix.
        </para>
        <para>
            These tarballs unpack into the 
            <filename class="directory">/opt/poky</filename> directory and contain
            a setup script (e.g. 
            <filename>/opt/poky/environment-setup-i586-poky-linux</filename>), from which 
            you can source to initialize a suitable environment. Sourcing these files adds the 
            compiler, QEMU scripts, QEMU binary, a special version of pkgconfig and other 
            useful utilities to the PATH variable. Variables to assist pkgconfig and 
            autotools are also defined so that, for example, configure can find pre-generated test 
            results for tests that need target hardware on which to run.
        </para>
        <para>
            Using the toolchain with autotool-enabled packages is straightforward - just pass the 
            appropriate host option to configure. 
            Following is an example:
            <literallayout class='monospaced'>
     $ ./configure --host=arm-poky-linux-gnueabi
            </literallayout>
            For other projects it is usually a case of ensuring the cross tools are used:
            <literallayout class='monospaced'>
     CC=arm-poky-linux-gnueabi-gcc and LD=arm-poky-linux-gnueabi-ld
            </literallayout>
        </para>
        </section>

        <section id="using-the-eclipse-and-anjuta-plug-ins">
        <title>Using the Eclipse and Anjuta Plug-ins</title>
        <para>
            Yocto Project supports both Anjuta and Eclipse IDE plug-ins to make developing software
            easier for the application developer. The plug-ins provide capability
            extensions to the graphical IDE allowing for cross compilation, 
            deployment and execution of the output in a QEMU emulation session. 
            Support of these plug-ins also allows for cross debugging and
            profiling.  Additionally, the Eclipse plug-in provides a suite of tools 
            that allows the developer to perform remote profiling, tracing, collection of 
            power data, collection of latency data and collection of performance data.
        </para>

            <section id="the-eclipse-plug-in">
            <title>The Eclipse Plug-in</title>
            <para>
                To use the Eclipse plug-in, a toolchain and SDK built by Poky is required along with 
                the Eclipse Framework (Helios 3.6.1). 
                To install the plug-in you need to be in the Eclipse IDE and select 
                the following menu:
                <literallayout class='monospaced'>
     Help -> Install New Software
                </literallayout>
                Specify the target URL as <ulink url='http://www.yoctoproject.org/downloads/eclipse-plug-in/'></ulink>.
            </para>
            <para>
                If you want to download the source code for the plug-in you can find it in the Poky 
                git repository, which has a web interface, and is located at
                <ulink url="http://git.pokylinux.org/cgit.cgi/eclipse-poky"></ulink>.
            </para>
  
                <section id="installing-and-setting-up-the-eclipse-ide">
                <title>Installing and Setting up the Eclipse IDE</title>
                <para>
                    If you don't have the Eclipse IDE (Helios 3.6.1) on your system you need to 
                    download and install it from <ulink url="http://www.eclipse.org/downloads"></ulink>.
                    Choose the Eclipse Classic, which contains the Eclipse Platform, Java Development 
                    Tools (JDT), and the Plug-in Development Environment.
                </para>
                <note>
                   <para>
                    Due to the Java Virtual Machine's garbage collection (GC) process the 
                    permanent generation space (PermGen) is not cleaned up.  This space stores
                    meta-data descriptions of classes.  The default value is set too small
                    and it could trigger an out-of-memory error like the following:
                    <literallayout class='monospaced'>
     Java.lang.OutOfMemoryError: PermGen space
                    </literallayout>
                    This error causes the applications to hang.  
                   </para>
                </note>
                <para>
                    To fix this issue you can use the <filename>-vmargs</filename>
                    option when you start Eclipse to increase the size of the permanent generation space:
                    <literallayout class='monospaced'>
     Eclipse -vmargs -XX:PermSize=256M
                    </literallayout>
                </para>
                </section>

                <section id="installing-the-yocto-plug-in">
                <title>Installing the Yocto Plug-in</title>
                    <para>
                        Once you have the Eclipse IDE installed and configured you need to install the 
                        Yocto plug-in.  You do this similar to installing the Eclipse plug-ins in the 
                        previous section.
                    </para>
                    <para>
                        Do the following to install the Yocto plug-in into the Eclipse IDE:
                    <orderedlist>
                        <listitem><para>Select the "Help -> Install New Software" item.</para></listitem>
                        <listitem><para>In the "Work with:" area click "Add..." and enter the URL for 
                            the Yocto plug-in, which is 
                            <ulink url='http://www.yoctoproject.org/downloads/eclipse-plugin/'></ulink></para></listitem>
                        <listitem><para>Finish out the installation of the update similar to any other
                            Eclipse plug-in.</para></listitem>
                    </orderedlist>
                    </para>
                </section>
         
                <section id="configuring-yocto-eclipse-plug-in">
                <title>Configuring Yocto Eclipse plug-in</title>
                <para>
                    To configure the Yocto Eclipse plug-in you need to select the mode and the
                    architecture with which you will be working.  Start by selecting "Preferences" 
                    from the "Window" menu and then select "Yocto SDK".
                </para>
                <para>
                    If you normally will use an installed Yocto 
                    SDK (under <filename>/opt/poky</filename>) select “SDK Root Mode”.  Otherwise, if your crosstool chain 
                    and sysroot are within your poky tree, select “Poky Tree Mode”.  
                    If you are in SDK Root Mode you need to provide your poky tree path, for
                    example, <filename>$&lt;Poky_tree&gt;/build/</filename>. 
                </para>
                <para>
                    Next, you need to select the architecture. 
                    Use the drop down list and select the architecture that you’ll be primarily 
                    working against.
                    For target option, select your typical target QEMU vs External hardware.  If you 
                    choose QEMU, you’ll need to specify your QEMU kernel file with full path and the 
                    rootfs mount point.  Yocto QEMU boots off user mode NFS.
                    See the <link linkend='platdev-appdev-qemu'>Developing Externally in QEMU</link> section for 
                    how to set it up.
                </para>
                <para>
                    To make your settings the defaults for every new Yocto project created using 
                    the Eclipse IDE, simply save the settings. 
                </para>
                </section>

                <section id="using-the-yocto-eclipse-plug-in">
                <title>Using the Yocto Eclipse Plug-in</title>
                <para>
                    As an example, this section shows you how to cross-compile a Yocto C project that 
                    is autotools-based, deploy the project into QEMU, and then run the debugger against it.
                    You need to configure the project, trigger the <filename> autogen.sh</filename>, build 
                    the image, start QEMU, and then debug.
                </para>
                <para>
                    The following steps show how to create a Yocto autotools-based project using a given template:
                </para>
                <orderedlist>
                    <listitem><para>Select "File -> New -> Project" to start the wizard.</para></listitem>
                    <listitem><para>Expand "C/C++" and select "C Project".</para></listitem>
                    <listitem><para>Click "Next" and select a template (e.g. "Hello World ANSI C Project").</para></listitem>
                    <listitem><para>Complete the steps to create the new Yocto autotools-based project using 
                        your chosen template.</para></listitem>
                </orderedlist>
                <para>
                    By default, the project uses the Yocto preferences settings as defined using the procedure in 
                    <link linkend="configuring-yocto-eclipse-plug-in">the previous section</link>.
                    If there are any specific setup requirements for the newly created project
                    you need to reconfigure the Yocto plug-in through the menu selection by doing the following:
                </para>
                <orderedlist>
                    <listitem><para>Select the "Project -> Invoke Yocto Tools -> Reconfigure Yocto" menu item.</para></listitem>
                    <listitem><para>Complete the dialogue to specify the specific toolchain and QEMU setup information.</para></listitem>
                </orderedlist>
                <para>
                    To build the project follow these steps:
                </para>
                <orderedlist>
                    <listitem><para>Select "Project -> Reconfigure Project" to trigger the 
                        <filename>autogen.sh</filename> command.</para></listitem>
                    <listitem><para>Select "Project -> Build" to build the project.</para></listitem>
                </orderedlist>
                <para>
                    To start QEMU follow these steps:
                </para>
                <orderedlist>
                    <listitem><para>Select "Run -> External Tools" and see if there is 
                        a QEMU instance for the desired target.  
                        If one exists, click on the instance to start QEMU.  
                        If your target does not exist, click "External Tools Configuration" and   
                        you should find an instance of QEMU for your architecture
                        under the entry under "Program".</para></listitem>
                    <listitem><para>Wait for the boot to complete.</para></listitem>
                </orderedlist>
                <para>
                    To deploy your project and start debugging follow these steps:
                </para>
                <orderedlist>
                    <listitem><para>Highlight your project in the project explorer.</para></listitem>
                    <listitem><para>Select "Run -> Debug Configurations" to bring up your remote debugging configuration 
                        in the right-hand window.</para></listitem>
                    <listitem><para>Expand “C/C++ Remote Application”.</para></listitem>
                    <listitem><para>Select "projectname_ gdb_target-poky-linux".  
                        You need to be sure there is an entry for the remote target.  
                        If no entry exists, click "New..." to bring up the wizard.  
                        Use the wizard to select TCF and enter the IP address of you remote target in the 
                        “Host name:” field.  
                        Back in the Remote Debug Configure window, specify in the 
                        “Remote Absolute File Path for C/C++ Application” field the absolute path for the program on 
                        the remote target. 
                        By default, the program deploys into the remote target.  
                        If you don't want this behavior then check “Skip download to target path”.</para></listitem>
                    <listitem><para>Click "Debug” to start the remote debugging session.</para></listitem>
                </orderedlist>
                </section>

                <section id="using-yocto-eclipse-plug-in-remote-tools-suite">
                <title>Using Yocto Eclipse plug-in Remote Tools Suite</title>
                <para>
                    Remote tools allow you to perform system profiling, kernel tracing, 
                    examine power consumption, and so forth.  To see and access the remote tools use the 
                    "Window -> YoctoTools" menu.
                </para>
                <para>
                    Once you pick a tool you need to configure it for the remote target.  Every tool 
                    needs to have the connection configured.  You must select an existing TCF-based
                    RSE connection to the remote target.  If one does not exist, click "New" to create one.
                </para>
                <para>
                    Here are some specifics about the remote tools:
                <itemizedlist>
                    <listitem><para>OProfile:  Selecting this tool causes the oprofile-server on the remote
                        target to launch on the local host machine.  The oprofile-viewer
                        must be installed on the local host machine and the oprofile-server must be
                        installed on the remote target, respectively, in order to use .</para></listitem>
                    <listitem><para>lttng:  Selecting this tool runs "usttrace" on the remote target, transfers
                        the output data back to the local host machine and uses "lttv-gui" to graphically
                        display the output.  The "lttv-gui" must be installed on the 
                        local host machine to use this tool.  
                        For information on how to use "lttng" to trace an 
                        application, see <ulink url="http://lttng.org/files/ust/manual/ust.html"></ulink>.
                        <para>
                            For "Application" you must supply the absolute path name of the application to 
                            be traced by user mode lttng.  For example, typing <filename>/path/to/foo"
                            </filename> triggers "usttrace /path/to/foo" on the 
                            remote target to trace the program <filename>/path/to/foo</filename>.
                        </para>
                        <para>
                            "Argument" is passed to "usttrace" running on the remote target.
                        </para></para>
                    </listitem>  
                    <listitem><para>powertop:  Selecting this tool runs "powertop" on the 
                        remote target machine and displays the results in a new view called "powertop".
                        <para>
                            "Time to gather data(sec):" is the time passed in seconds before data is 
                            gathered from the remote target for analysis.
                        </para>
                        <para>
                            "show pids in wakeups list:" corresponds to the <filename>-p</filename>
                            argument passed to "powertop".
                        </para></para>
                    </listitem>
                    <listitem><para>latencytop and perf:  "latencytop" identifies 
                        system latency, while "perf" monitors the system's performance 
                        counter registers.  Selecting either of these tools causes an RSE
                        terminal view to appear from which you can run the tools.  Both tools refresh the 
                        entire screen to display results while they run.</para></listitem>
                </itemizedlist>
                </para>
                </section>
            </section>

            <section id="the-anjuta-plug-in">
            <title>The Anjuta Plug-in</title>
            <note>
                <para>
                    Support for the Anjuta plug-in ends after Yocto project 0.9 Release.  
                    However, the source code can be downloaded from the git repository listed later in 
                    this section.
                    The community is free to continue supporting it post 0.9 Release.
                </para>
            </note>
            <para>
                An Anjuta IDE plug-in exists to make developing software within the Poky framework
                easier for the application developer familiar with that environment. 
                The plug-in presents a graphical IDE that allows you to cross-compile, cross-debug, 
                profile, deploy, and execute an application.
            </para>
            <para>
                To use the plug-in, a toolchain and SDK built by Poky, Anjuta, its development headers and the Anjuta
                Plug-in are all required. 
                The Poky Anjuta Plug-in is available to download as a tarball at the OpenedHand 
                labs <ulink url="http://labs.o-hand.com/anjuta-poky-sdk-plugin/"></ulink> page or 
                directly from the Poky Git repository located at 
                <ulink url="git://git.pokylinux.org/anjuta-poky"></ulink>.
                You can also access a web interface to the repository at
                <ulink url="http://git.pokylinux.org/?p=anjuta-poky.git;a=summary"></ulink>.
             </para>
             <para>
                See the README file contained in the project for more information on 
                Anjuta dependencies and building the plug-in. 
                If you want to disable remote gdb debugging, pass the "--disable-gdb-integration" switch when 
                you configure the plug-in.
            </para>
                <section id="setting-up-the-anjuta-plugin">
                <title>Setting Up the Anjuta Plug-in</title>
                <para>
                    Follow these steps to set up the plug-in:
                    <orderedlist>
                        <listitem><para>Extract the tarball for the toolchain into / as root. 
                        The toolchain will be installed into <filename>/opt/poky</filename>.</para></listitem>
                        <listitem><para>To use the plug-in, first open or create an existing project. 
                        If you are creating a new project, the "C GTK+"
                        project type will allow itself to be cross-compiled. 
                        However, you should be aware that this type uses "glade" for the UI.</para></listitem>
                        <listitem><para>To activate the plug-in, select "Edit -> Preferences" and then choose
                        "General" from the left hand side. 
                        Choose the "Installed plug-ins" tab, scroll down to "Poky SDK" and 
                        check the box.</para></listitem>
                    </orderedlist>
                    The plug-in is now activated but not configured.  
                </para>
                </section>
                <section id="configuring-the-anjuta-plugin">
                <title>Configuring the Anjuta Plug-in</title>
                <para>
                    You can find the configuration options for the SDK by choosing the Poky 
                    SDK icon from the left hand side. 
                    You need to define the following options:
                    <itemizedlist>
                        <listitem><para>SDK root: If you use an external toolchain you need to set 
                        SDK root, which is the root directory of the SDK's sysroot. 
                        For an i586 SDK directory is <filename>/opt/poky/</filename>. 
                        This directory will contain "bin", "include", "var" and so forth under your 
                        selected target architecture subdirectory 
                        <filename>/opt/poky/sysroot/i586-poky-linux/</filename>. 
                        The cross-compile tools you need are in 
                        <filename>/opt/poky/sysroot/i586-pokysdk-linux/</filename>.</para></listitem>
                        <listitem><para>Poky root: If you have a local Poky build tree, you need to 
                        set the Poky root, which is the root directory of the poky build tree.
                        If you build your i586 target architecture under the subdirectory of 
                        <filename>build_x86</filename> within your Poky tree, the Poky root directory
                        should be <filename>$&lt;poky_tree&gt;/build_x86/</filename>.</para></listitem>
                        <listitem><para>Target Architecture: This is the cross compile triplet, 
                        for example, "i586-poky-linux". 
                        This target triplet is the prefix extracted from the set up script file's name. 
                        For example, if the script file name is 
                        <filename>/opt/poky/environment-setup-i586-poky-linux</filename> then the extracted target 
                        triplet is "i586-poky-linux".</para></listitem>
                        <listitem><para>Kernel: Use the file chooser to select the kernel used with QEMU.</para></listitem>
                        <listitem><para>Root filesystem: Use the file chooser to select the root 
                        filesystem directory.  This directory is where you use "poky-extract-sdk" to extract the 
                        poky-image-sdk tarball.</para></listitem>
                     </itemizedlist>
                </para>
                </section>
                <section id="using-the-anjuta-plug-in">
                <title>Using the Anjuta Plug-in</title>
                <para>
                    The steps in this section show how to cross-compile a project, deploy it into
                    QEMU, run a debugger against it and then perform a system-wide profile.
                <orderedlist>
                    <listitem><para>Choose "Build -> Run Configure" or "Build -> Run Autogenerate" to run
                    "configure" or "autogen", respectively for the project. 
                    Either command passes command-line arguments to instruct the 
                    cross-compile.</para></listitem>
                    <listitem><para>Choose "Build -> Build Project" to build and compile the project. 
                    If you have previously built the project in the same tree without using 
                    the cross-compiler you might find that your project fails to link. 
                    If this is the case, simply select "Build -> Clean Project" to remove the 
                    old binaries. 
                    After you clean the project you can then try building it again.</para></listitem>
                    <listitem><para>Choose "Tools -> Start QEMU" to start QEMU.  
                    After QEMU starts any error messages will appear in the message view. 
                    Once Poky has fully booted within QEMU you can deploy the project 
                    into it.</para></listitem>
                    <listitem><para>Once the project is built and you have QEMU running choose 
                    "Tools -> Deploy" to install the package into a temporary
                    directory and then copy it using "rsync" over SSH into the target. 
                    A progress bar and appropriate messages appear in the message view.</para></listitem>
                    <listitem><para>To debug a program installed onto the target choose 
                    "Tools -> Debug remote". 
                    Choosing this menu item causes prompts to appear to define the local binary 
                    for debugging and also for the command line used to run on the target. 
                    When you provide the command line be sure to include the full path to the to binary 
                    installed in the target. 
                    When the command line runs a "gdbserver" over SSH is started on the target and 
                    an instance of "cross-gdb" starts in a local terminal. 
                    The instance of "cross-gdb" will be preloaded to connect to the server and use the SDK root to 
                    find symbols. 
                    It also connects to the target and loads in various libraries as well as the 
                    target program. 
                    You should define any breakpoints or watchpoints at this point in the process since you might not 
                    be able to interrupt the execution later. 
                    To stop the debugger on the target choose "Tools -> Stop debugger".</para></listitem>
                    <listitem><para>It is also possible to execute a command in the target over SSH.
                    Doing so causes the appropriate environment to be established for execution. 
                    To execute a command choose "Choose Tools -> Run remote". 
                    This selection opens a terminal with the SSH command inside.</para></listitem>
                    <listitem><para>To perform a system-wide profile against the system running in QEMU choose 
                    "Tools -> Profile remote". 
                    This choice starts up "OProfileUI" with the appropriate parameters to 
                    connect to the server running inside QEMU and also supplies the path 
                    for debug information necessary to get a useful profile.</para></listitem>
                </orderedlist>
                </para>
                </section>
            </section>
        </section>

        <section id="platdev-appdev-qemu">
        <title>Developing Externally in QEMU</title>
        <para>
            Running Poky QEMU images is covered in the 
            <ulink url="http://www.yoctoproject.org/docs/yocto-quick-start/yocto-project-qs.html">
            Yocto Project Quick Start</ulink> in the "A Quick Test Run" section.
        </para>
        <para>
            Poky's QEMU images contain a complete native toolchain. This means 
            you can develop applications within QEMU similar to the way you would in a normal system. 
            Using qemux86 on an x86 machine is fast since the 
            guest and host architectures match.
            On the other hand, using qemuarm can be slower but gives 
            faithful emulation of ARM-specific issues. To speed things up, these 
            images support using "distcc" to call a cross-compiler outside the 
            emulated system. If "runqemu" was used to start
            QEMU, and "distccd" is present on the host system, any Bitbake cross-compiling 
            toolchain available from the build system is automatically
            used from within QEMU simply by calling "distcc".  You can accomplish this by defining the 
            cross-compiler variable (e.g. <filename>export CC="distcc"</filename>).
            Alternatively, if a suitable SDK/toolchain is present in 
            <filename>/opt/poky</filename> it is also
            automatically be used.
        </para>

        <para>
            There are several options for connecting into the emulated system. 
            QEMU provides a framebuffer interface that has standard consoles 
            available. There is also a serial connection available that has a 
            console to the system running on it and uses standard IP networking. 
            The images have a dropbear ssh server running with the root password 
            disabled to allow standard ssh and scp commands to work. The images
            also contain an NFS server that exports the guest's root filesystem, which 
            allows it to be made available to the host.
        </para>
        </section>              

        <section id="platdev-appdev-insitu">
        <title>Developing in Poky Directly</title>
        <para>
            Working directly in Poky is a fast and effective development technique.
            The idea is that you can directly edit files in 
            <glossterm><link linkend='var-WORKDIR'>WORKDIR</link></glossterm> 
            or the source directory <glossterm><link linkend='var-S'>S</link></glossterm> 
            and then force specific tasks to rerun in order to test the changes. 
            An example session working on the matchbox-desktop package might 
            look like this:
        </para>

        <para>
            <literallayout class='monospaced'>
     $ bitbake matchbox-desktop
     $ sh
     $ cd tmp/work/armv5te-poky-linux-gnueabi/matchbox-desktop-2.0+svnr1708-r0/
     $ cd matchbox-desktop-2
     $ vi src/main.c
     $ exit
     $ bitbake matchbox-desktop -c compile -f
     $ bitbake matchbox-desktop
            </literallayout>
        </para>

        <para>
            This example builds the package, changes into the work directory for the package,
            changes a file, then recompiles the package. Instead of using "sh" as it is in the example,
            you can also use two different terminals. However, the risk of using two terminals 
            is that a command like "unpack" could destroy the changes you've made to the
            work directory.  Consequently, you need to work carefully.
        </para>

        <para>
            It is useful when making changes directly to the work directory files to do
            so using "quilt" as detailed in the <link linkend='usingpoky-modifying-packages-quilt'> 
            modifying packages with quilt</link> section. You can copy the resulting patches  
            into the recipe directory and use them directly in the <glossterm><link 
            linkend='var-SRC_URI'>SRC_URI</link></glossterm>.
        </para>
        <para>
            For a review of the skills used in this section see the <link
            linkend="usingpoky-components-bitbake">Bitbake</link> and <link 
            linkend="usingpoky-debugging-taskrunning">Running Specific Tasks</link> Sections.
        </para>
        </section>

        <section id="platdev-appdev-devshell">
        <title>Developing with 'devshell'</title>

        <para>
            When debugging certain commands or even when just editing packages, the
            'devshell' can be a useful tool. 
            Use a command like the following to start this tool.
        </para>

        <para>
            <literallayout class='monospaced'>
     $ bitbake matchbox-desktop -c devshell
            </literallayout>
        </para>

        <para>
            This command opens a terminal with a shell prompt within the Poky 
            environment. Consequently, the following occurs:
            <itemizedlist>
                <listitem><para>The PATH variable includes the cross toolchain.</para></listitem>
                <listitem><para>The pkgconfig variables find the correct <filename>.pc</filename> files.</para></listitem>
                <listitem><para>"configure" finds the Poky site files as well as any other necessary files.</para></listitem>
            </itemizedlist>
            Within this environment, you can run "configure" or "compile" commands as if they 
            were being run by Poky itself. 
            The working directory also automatically changes to the (<glossterm><link linkend='var-S'>S</link></glossterm>) 
            directory. 
            When you are finished, you just exit the shell or close the terminal window.
        </para>

        <para>
            The default shell used by "devshell" is the gnome-terminal. 
            You can use other forms of terminal can by setting the <glossterm>
            <link linkend='var-TERMCMD'>TERMCMD</link></glossterm> and <glossterm>
            <link linkend='var-TERMCMDRUN'>TERMCMDRUN</link></glossterm> variables 
            in <filename>local.conf</filename>. 
            For examples of the other options available, see 
            <filename>meta/conf/bitbake.conf</filename>. 
        </para>
        <para>
            An external shell is launched rather than opening directly into the original terminal 
            window.
            This allows easier interaction with Bitbake's multiple threads as well as 
            for a future client/server split.
            Note that "devshell" will still work over X11 forwarding or similar situations.
        </para>

        <para>
            It is worth remembering that inside "devshell" you need to use the full
            compiler name such as <filename>arm-poky-linux-gnueabi-gcc</filename> 
            instead of just <filename>gcc</filename>.
            The same applies to other applications such as gcc, bintuils, libtool and so forth.
            Poky will have setup environmental variables such as CC to assist applications, such as make,
            find the correct tools.
        </para>
        </section>

        <section id="platdev-appdev-srcrev">
        <title>Developing within Poky with an External SCM-based Package</title>

        <para>
            If you're working on a recipe that pulls from an external SCM it 
            is possible to have Poky notice new changes added to the 
            SCM and then build the latest version using them. 
            This only works for SCMs from which it is possible to get a sensible revision number for changes.
            Currently it works for svn, git and bzr repositories.
        </para>

        <para>
            To enable this behavior simply add <glossterm>
            <link linkend='var-SRCREV'>SRCREV</link></glossterm>_pn-<glossterm>
            <link linkend='var-PN'>PN</link></glossterm> = "${AUTOREV}" to 
            <filename>local.conf</filename>, where <glossterm><link linkend='var-PN'>PN</link></glossterm> 
            is the name of the package for which you want to enable automatic source 
            revision updating.
        </para>
        </section>
    </section>

<section id="platdev-gdb-remotedebug">
    <title>Debugging with GDB Remotely</title>

    <para>
        GNU Project Debugger (GDB)
        allows you to examine running programs to understand and fix problems and
        also to perform post-mortem style analysis of program crashes. 
        GDB is available as a package within Poky and by default is installed in sdk images. 
        See <ulink url="http://sourceware.org/gdb/"/> for the GDB source.
    </para>
    <tip><para>
        For best results install <filename>-dbg</filename> packages for the applications 
        you are going to debug.
        Doing so makes available extra debug symbols that will give you more meaningful output.
    </para></tip>

    <para>
        Sometimes, due to memory or disk space constraints, it is not possible
        to use GDB directly on the remote target to debug applications. 
        These constraints arise because GDB needs to load the debugging information and the 
        binaries of the process being debugged. 
        Additionally, GDB needs to perform many computations to locate information such as function 
        names, variable names and values, stack traces and so forth - even before starting the 
        debugging process. 
        These extra computations place more load on the target system and can alter the
        characteristics of the program being debugged.
    </para>
    <para>
        To help get past these constraints you can use GDBSERVER.
        It runs on the remote target and does not load any debugging information 
        from the debugged process.
        Instead, a GDB instance processes the debugging information that is run on a 
        remote computer - the host GDB. 
        The host GDB then sends control commands to GDBSERVER to make it stop or start the debugged 
        program, as well as read or write memory regions of that debugged
        program. 
        All the debugging information loaded and processed as well
        as all the heavy debugging is done by the host GDB.
        Offloading these processes gives the GDBSERVER running on the target a chance to remain 
        small and fast.
    </para>
    <para>
        Because the host GDB is responsible for loading the debugging information and 
        for doing the necessary processing to make actual debugging happen, the 
        user has to make sure the host can access the unstripped binaries complete
        with their debugging information and also compiled with no optimizations. 
        The host GDB must also have local access to all the libraries used by the 
        debugged program. 
        Because GDBSERVER does not need any local debugging information the binaries on
        the remote target can remain stripped. 
        However, the binaries must also be compiled without optimization 
        so they match the host's binaries.
    </para>

    <para>
        To remain consistent with GDB documentation and terminology the binary being debugged 
        on the remote target machine is referred to as the 'inferior' binary.
        For documentation on GDB see the GDB site at 
        <ulink url="http://sourceware.org/gdb/documentation/">on their site</ulink>.
    </para>

    <section id="platdev-gdb-remotedebug-launch-gdbserver">
        <title>Launching GDBSERVER on the Target</title>
        <para>
            First, make sure GDBSERVER is installed on the target. If not, 
            install the package <filename>gdbserver</filename>, which needs the 
            <filename>libthread-db1</filename> package.
        </para>
        <para>
            As an example, to launch GDBSERVER on the target and make it ready to "debug" a 
            program located at <filename>/path/to/inferior</filename>, connect
            to the target and launch:
            <literallayout class='monospaced'>
     $ gdbserver localhost:2345 /path/to/inferior
            </literallayout>
            GDBSERVER should now be listening on port 2345 for debugging
            commands coming from a remote GDB process that is running on the host computer.
            Communication between GDBSERVER and the host GDB are done using TCP. 
            To use other communication protocols please refer to the GDBSERVER documentation.
        </para>
    </section>

    <section id="platdev-gdb-remotedebug-launch-gdb">
        <title>Launching GDB on the Host Computer</title>

        <para>
            Running GDB on the host computer takes a number of stages.
            This section describes those stages.
        </para>

        <section id="platdev-gdb-remotedebug-launch-gdb-buildcross">
            <title>Building the Cross-GDB Package</title>
            <para>
                A suitable GDB cross-binary is required that runs on your host computer but
                also knows about the the ABI of the remote target. 
                You can get this binary from the the Poky toolchain  - for example:
                <programlisting> 
/usr/local/poky/eabi-glibc/arm/bin/arm-poky-linux-gnueabi-gdb
                </programlisting> 
                where "arm" is the target architecture and "linux-gnueabi" the target ABI.
            </para>

            <para>
                Alternatively, Poky can build the <filename>gdb-cross</filename> binary. 
                For example, the following command builds it:
                <literallayout class='monospaced'>
     $ bitbake gdb-cross
                </literallayout>
                Once the binary is built you can find it here: 
                <programlisting>
tmp/sysroots/&lt;host-arch&lt;/usr/bin/&lt;target-abi&gt;-gdb 
                </programlisting>
            </para>

        </section>
        <section id="platdev-gdb-remotedebug-launch-gdb-inferiorbins">

            <title>Making the Inferior Binaries Available</title>

            <para>
                The inferior binary (complete with all debugging symbols) as well as any
                libraries (and their debugging symbols) on which the inferior binary depends
                need to be available.
                There are a number of ways you can make these available.
            </para>

            <para>
                Perhaps the easiest is to have an 'sdk' image that corresponds to the plain
                image installed on the device. 
                In the case of 'poky-image-sato', 'poky-image-sdk' would contain suitable symbols. 
                Because the sdk images already have the debugging symbols installed it is just a 
                question of expanding the archive to some location and then informing GDB. 
            </para>

            <para>
                Alternatively, Poky can build a custom directory of files for a specific 
                debugging purpose by reusing its <filename>tmp/rootfs</filename> directory.
                This directory contains the contents of the last built image. 
                This process assumes two things:
                <itemizedlist>
                    <listitem><para>The image running on the target was the last image to 
                    be built by Poky.</para></listitem>
                    <listitem><para>The package (<filename>foo</filename> in the following 
                    example) that contains the inferior binary to be debugged has been built 
                    without optimization and has debugging information available.</para></listitem>
                </itemizedlist>
            </para>
            <para>
                These steps show how to build the custom directory of files:
            </para>
            <orderedlist>
                <listitem><para>Install the package (<filename>foo</filename> in this case) to 
                <filename>tmp/rootfs</filename>:
                <programlisting>
tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/poky-image-sato-1.0-r0/temp/opkg.conf -o \
tmp/rootfs/ update
                </programlisting></para></listitem>
                <listitem><para>Install the debugging information:
                <programlisting>
tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/poky-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo

tmp/sysroots/i686-linux/usr/bin/opkg-cl -f \
tmp/work/&lt;target-abi&gt;/poky-image-sato-1.0-r0/temp/opkg.conf \
-o tmp/rootfs install foo-dbg
                </programlisting></para></listitem>
            </orderedlist>

        </section>
        <section id="platdev-gdb-remotedebug-launch-gdb-launchhost">

            <title>Launch the Host GDB</title>
            <para>
                To launch the host GDB, you run the cross-gdb binary and provide the inferior
                binary as part of the command line.  
                For example, the following command form continues with the example used in 
                the previous section.  
                This command form loads the <filename>foo</filename> binary
                as well as the debugging information:
                <literallayout class='monospaced'>
     $ &lt;target-abi&gt;-gdb rootfs/usr/bin/foo
                </literallayout>
                Once the GDB prompt appears, you must instruct GDB to load all the libraries
                of the inferior binary from <filename>tmp/rootfs</filename> as follows:
                <literallayout class='monospaced'>
     $ set solib-absolute-prefix /path/to/tmp/rootfs
                </literallayout>
                The pathname <filename>/path/to/tmp/rootfs</filename> must either be
                the absolute path to <filename>tmp/rootfs</filename> or the location at which 
                binaries with debugging information reside.
            </para>
            <para>
                At this point you can have GDB connect to the GDBSERVER that is running 
                on the remote target by using the following command form:
                <literallayout class='monospaced'>
     $ target remote remote-target-ip-address:2345
                </literallayout>
                The <filename>remote-target-ip-address</filename> is the IP address of the
                remote target where the GDBSERVER is running. 
                Port 2345 is the port on which the GDBSERVER is running.
            </para>

        </section>
        <section id="platdev-gdb-remotedebug-launch-gdb-using">

            <title>Using the Debugger</title>
            <para>
                You can now proceed with debugging as normal - as if you were debugging
                on the local machine.
                For example, to instruct GDB to break in the "main" function and then 
                continue with execution of the inferior binary use the following commands
                from within GDB:
                <literallayout class='monospaced'>
     (gdb) break main
     (gdb) continue
                </literallayout>
            </para>
            <para>
                For more information about using GDB, see the project's online documentation at 
                <ulink url="http://sourceware.org/gdb/download/onlinedocs/"/>.
            </para>
        </section>
    </section>

</section>

<section id="platdev-oprofile">
    <title>Profiling with OProfile</title>

    <para>
        <ulink url="http://oprofile.sourceforge.net/">OProfile</ulink> is a 
        statistical profiler well suited for finding performance 
        bottlenecks in both userspace software and in the kernel. 
        This profiler provides answers to questions like "Which functions does my application spend 
        the most time in when doing X?" 
        Because Poky is well integrated with OProfile it makes profiling applications on target 
        hardware straightforward.
    </para>

    <para>
        To use OProfile you need an image that has OProfile installed. 
        The easiest way to do this is with "tools-profile" in 
        <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm>. 
        You also need debugging symbols to be available on the system where the analysis 
        takes place. 
        You can gain access to the symbols by using "dbg-pkgs" in 
        <glossterm><link linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm> or by
        installing the appropriate <filename>-dbg</filename> packages. 
    </para>
    <para>
        For successful call graph analysis the binaries must preserve the frame 
        pointer register and should also be compiled with the 
        "-fno-omit-framepointer" flag. 
        In Poky you can achieve this by setting  
        <glossterm><link linkend='var-SELECTED_OPTIMIZATION'>SELECTED_OPTIMIZATION
        </link></glossterm> to "-fexpensive-optimizations -fno-omit-framepointer 
        -frename-registers -O2". 
        You can also achieve it by setting 
        <glossterm><link linkend='var-DEBUG_BUILD'>DEBUG_BUILD</link></glossterm> to "1" in 
        <filename>local.conf</filename>.
        If you use the DEBUG_BUILD variable you will also add extra debug information 
        that can make the debug packages large.
    </para>

    <section id="platdev-oprofile-target">
        <title>Profiling on the Target</title>

        <para>
            Using OProfile you can perform all the profiling work on the target device. 
            A simple OProfile session might look like the following:
        </para>

        <para>
            <literallayout class='monospaced'>
# opcontrol --reset
# opcontrol --start --separate=lib --no-vmlinux -c 5
[do whatever is being profiled]
# opcontrol --stop
$ opreport -cl
            </literallayout>
        </para>

        <para>
            In this example, the reset command clears any previously profiled data.
            The next command starts OProfile.
            The options used when starting the profiler separate dynamic library data 
            within applications, disable kernel profiling, and enable callgraphing up to
            five levels deep.
        </para>
        <note><para>
            To profile the kernel, you would specify the 
            <parameter>--vmlinux=/path/to/vmlinux</parameter> option.
            The vmlinux file is usually in <filename class="directory">/boot/</filename> 
            in Poky and must match the running kernel.
        </para></note>
        <para> 
            After you perform your profiling tasks, the next command stops the profiler. 
            After that you can view results with the "opreport" command with options
            to see the separate library symbols and callgraph information.
        </para>
        <para>
            Callgraphing logs information about time spent in functions and about a function's
            calling function (parent) and called functions (children).
            The higher the callgraphing depth, 
            the more accurate the results.  
            However, higher depths also increase the logging 
            overhead.
            Consequently, you should take care when setting the callgraphing depth. 
        </para>
        <note><para>
            On ARM, binaries need to have the frame pointer enabled for callgraphing to work.
            To accomplish this use the <filename>-fno-omit-framepointer</filename> option 
            with <filename>gcc</filename>.
        </para></note>
        <para>
            For more information on using OProfile, see the OProfile 
            online documentation at 
            <ulink url="http://oprofile.sourceforge.net/docs/"/>.
        </para>
    </section>

    <section id="platdev-oprofile-oprofileui">
        <title>Using OProfileUI</title>

        <para>
            A graphical user interface for OProfile is also available. 
            You can download and build it from svn at
            <ulink url="http://svn.o-hand.com/repos/oprofileui/trunk/"></ulink>. 
            If the "tools-profile" image feature is selected, all necessary binaries
            are installed onto the target device for OProfileUI interaction.
        </para>

<!-- DISABLED, Need a more 'contextual' shot?
        <screenshot>
        <mediaobject>
            <imageobject>
                <imagedata fileref="screenshots/ss-oprofile-viewer.png" format="PNG"/>
            </imageobject>
            <caption>
                <para>OProfileUI Viewer showing an application being profiled on a remote device</para>
            </caption>
         </mediaobject>
         </screenshot>
-->
        <para>
            In order to convert the data in the sample format from the target
            to the host you need the <filename>opimport</filename> program. 
            This program is not included in standard Debian OProfile packages.
            However, an OProfile package with this addition is available from the 
            <ulink url='http://debian.o-hand.com/'>OpenedHand repository</ulink>.
            We recommend using OProfile 0.9.3 or greater. 
        </para>
        <para>
            Even though Poky usually includes all needed patches on the target device, you 
            might find you need other OProfile patches for recent OProfileUI features.
            If so, see the <ulink url='http://svn.o-hand.com/repos/oprofileui/trunk/README'>
            OProfileUI README</ulink> for the most recent information.
            You can also see <ulink url="http://labs.o-hand.com/oprofileui">OProfileUI website
            </ulink> for general information on the OProfileUI project. 
        </para>

        <section id="platdev-oprofile-oprofileui-online">
            <title>Online Mode</title>

            <para>
                Using OProfile in online mode assumes a working network connection with the target 
                hardware. 
                With this connection, you just need to run "oprofile-server" on the device. 
                By default OProfile listens on port 4224. 
            </para>
            <note><para>
                You can change the port using the <filename>--port</filename> command-line 
                option.
            </para></note>

            <para>
                The client program is called "oprofile-viewer" and its UI is relatively 
                straightforward.
                You access key functionality through the buttons on the toolbar, which
                are duplicated in the menus.
                The buttons are:
            </para>

            <itemizedlist>
                <listitem>
                    <para>
                        Connect - Connects to the remote host.
                        You can also supply the IP address or hostname.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Disconnect - Disconnects from the target.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Start - Starts profiling on the device.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Stop - Stops profiling on the device and downloads the data to the local
                        host. 
                        Stopping the profiler generates the profile and displays it in the viewer.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Download - Downloads the data from the target and generates the profile, 
                        which appears in the viewer.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Reset - Resets the sample data on the device. 
                        Resetting the data removes sample information collected from previous
                        sampling runs. 
                        Be sure you reset the data if you do not want to include old sample information.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Save - Saves the data downloaded from the target to another directory for later
                        examination.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Open - Loads previously saved data.
                    </para>
                </listitem>
            </itemizedlist>

            <para>
                The client downloads the complete 'profile archive' from
                the target to the host for processing. 
                This archive is a directory that contains the sample data, the object files 
                and the debug information for the object files. 
                The archive is then converted using the "oparchconv" script, which is 
                included in this distribution.
                The script uses "opimport" to convert the archive from
                the target to something that can be processed on the host.
            </para>

            <para>
                Downloaded archives reside in <filename>/tmp</filename> and are cleared up 
                when they are no longer in use.
            </para>

            <para>
                If you wish to perform kernel profiling you need to be sure 
                a "vmlinux" file that matches the running kernel is available. 
                In Poky, that file is usually located in 
                <filename>/boot/vmlinux-KERNELVERSION</filename>, where KERNEL-version is the 
                version of the kernel (e.g. 2.6.23). 
                Poky generates separate vmlinux packages for each kernel
                it builds so it should be a question of just making sure a matching package is 
                installed - for example: <filename>opkg install kernel-vmlinux</filename>. 
                The files are automatically installed into development and profiling images 
                alongside OProfile. 
                There is a configuration option within the OProfileUI settings page where 
                you can enter the location of the vmlinux file. 
            </para>

            <para>
                Waiting for debug symbols to transfer from the device can be slow, and it
                is not always necessary to actually have them on the device for OProfile use. 
                All that is needed is a copy of the filesystem with the debug symbols present 
                on the viewer system. 
                The "<link linkend='platdev-gdb-remotedebug-launch-gdb'>Launching GDB
                on the Host Computer</link>" section covers how to create such a directory with Poky and 
                how to use the OProfileUI Settings dialog to specify the location.
                If you specify the directory, it will be used when the file checksums 
                match those on the system you are profiling.
            </para>
        </section>

        <section id="platdev-oprofile-oprofileui-offline">
            <title>Offline Mode</title>

            <para>
                If network access to the target is unavailable, you can generate
                an archive for processing in "oprofile-viewer" as follows:
            </para>

            <para>
                <literallayout class='monospaced'>
     # opcontrol --reset
     # opcontrol --start --separate=lib --no-vmlinux -c 5
     [do whatever is being profiled]
     # opcontrol --stop
     # oparchive -o my_archive
                </literallayout>
            </para>

            <para>
                In the above example <filename>my_archive</filename> is the name of the 
                archive directory where you would like the profile archive to be kept. 
                After the directory is created, you can copy it to another host and load it
                using "oprofile-viewer" open functionality.
                If necessary, the archive is converted.
            </para>
        </section>
    </section>
</section>



</chapter> 
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