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 (<link linkend='ref-images'>see
            the images section</link>) build tarballs that contain toolchains and 
            libraries suitable for application development outside of Poky. 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>, which
            you can source to initialize a suitable environment. Sourcing these 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 set 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 as in the following 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 supports 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). 
                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 http://yocto./download (real link needed).
            </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) 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>
                <para>
                    NOTE: Due to the Java Virtual Machine's garbage collection (GC) process the 
                    permanent generation space (PermGen) is not cleaned up.  This space is used 
                    to store 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>
                <para>
                    To fix this issue you can use the <command>-vmargs</command>
                    option when you start Eclipse to increase the size of the permenant 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 configure 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:
                    <itemizedlist>
                        <listitem>Select the "Help -> Install New Software" item.</listitem>
                        <listitem>In the "Work with:" area click "Add..." and enter the URL for 
                            the Yocto plug-in (we need to supply this URL).</listitem>
                        <listitem>Finish out the installation of the update similar to any other
                            Eclipse plug-in.</listitem>
                    </itemizedlist>
                    </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 then the
                    architecture with which you will be working.  Start by selecting "Preferences" 
                    from the "Window" menu and then selecting "Yocto SDK".
                </para>
                <para>
                    If you normally will use an installed Yocto 
                    SDK (under /opt/poky) 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 will need to provide your poky tree path, for
                    example, $&lt;Poky_tree&gt;/build/. 
                </para>
                <para>
                    Now 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 HW.  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, Please refer to QEMU
                    section for how to set it up. (Section TBD)
                </para>
                <para>
                    Save all your settings and they become your defaults for every new Yocto project
                    created using the Eclipse IDE.
                </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 autotools
                    based project, deploy it into QEMU, and then run the debugger against it.
                    You need to configure the project, trigger <command> autogen.sh</command>, build 
                    the image, start QEMU, and then debug.
                </para>
                <orderedlist>
                    <listitem>Creating a Yocto Autotools Based Project Using a Template:  
                        Get to the Wizard selection by selecting the File -> New -> Project 
                        menu.  Expand "C/C++" and select "C Project".  Click "Next" and select a template 
                        to start with, for example "Hello World ANSI C Project".  Complete the steps
                        to create a new Yocto autotools based project using this template.</listitem>
                    <listitem>Specify Specific Toolchain Configurations:  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
                        Project -> Invoke Yocto Tools -> Reconfigure Yocto.  Use this dialogue
                        to specify specific toolchain and QEMU setups for the project.</listitem>
                    <listitem>Building the Project:  Trigger <command>autogen.sh</command> through 
                        Project -> Reconfigure Project.  Then build the project using 
                        Project -> Build.</listitem>
                    <listitem>Starting QEMU:  Use the Run -> External Tools menu and see if there is 
                        a QEMU instance for the desired target.  If there is click on the instance
                        to start QEMU.  If your target is not there then click "External Tools
                        Configuration".  You should find an instance of QEMU for your architecture
                        under the entry under "Program".  After the boot completes you are ready to 
                        deploy the image into QEMU.</listitem>
                    <listitem>Debugging:  To bring up your remote debugging configuration in the 
                        right-hand window highlight your project in “Project Explorer”, select 
                        the Run -> Debug Configurations menu item and expand “C/C++ Remote Application”.
                        Next, select projectname_ gdb_target-poky-linux.  
                        You need to be sure that there is an
                        entry for the remote target you want to deploy and cross debug with.  If there
                        is no entry then click "New..." to bring up the wizard.  Using the wizard
                        select TCF and enter the IP address of you remote target in the 
                        “Host name:” field.  Back in the remote debug configure window, 
                        you need to specify the absolute path for the program on the remote target 
                        in the “Remote Absolute File Path for C/C++ Application” field.  By default, 
                        the program deploys into the remote target.  If you don't want this then check
                        “Skip download to target path”.  Finally, click "Debug” to start the remote
                        debugging session.</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 let you do things like 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 have to select an existing TCF-based
                    RSE connection to the remote target.  If one does not exist you need to create one
                    by clicking "New"
                </para>
                <para>
                    Here are some specifics about the remote tools:
                <itemizedlist>
                    <listitem>Oprofile:  Selecting this tool causes the oprofile-server on the remote
                        target to launch on the local host machine.  To use the oprofile the oprofile-viewer
                        must be installed on the local host machine and the oprofile-server must be
                        installed on the remote target.</listitem>
                    <listitem>lttng:  Selecting this tool runs ustrace on the remote target, transfers
                        the output data back to the local host machine and uses lttv-gui to graphically
                        display the output.  To use this tool the lttv-gui must be installed on the 
                        local host machine.  See <ulink url="http://lttng.org/files/ust/manual/ust.html">
                        </ulink> for information on how to use <command>lttng</command> to trace an 
                        application.
                        <para>
                            For "Application" you must supply the absolute path name to the application to 
                            be traced by user mode lttng.  For example, typing <command>/path/to/foo"
                            </command> triggers <command>usttrace /path/to/foo</command> on the 
                            remote target to trace the program <command>/path/to/foo</command>.
                        </para>
                        <para>
                            "Argument" is passed to "usttrace" running on the remote target.
                        </para>
                    </listitem>  
                    <listitem>powertop:  Selecting this tool runs <command>powertop</command> on the 
                        remote target machine and displays the result 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 <command>-p</command>
                            argument passed to <command>powertop</command>
                        </para>
                    </listitem>
                    <listitem>latencytop and perf:  The <command>latencytop</command> identifies 
                        system latency, while <command>perf</command> monitors the system's performance 
                        counter registers.  Selecting either of these tools causes an RSE
                        terminal view to appear in which you can run the tools.  Both tools refresh the 
                        entire screen to display results while they run.</listitem>
                </itemizedlist>
                </para>
                </section>
            </section>

            <section id="the-anjuta-plug-in">
            <title>The Anjuta Plug-in</title>
            <para>
                <emphasis>Note:</emphasis>  We will stop Anjuta plug-in support after 
                Yocto project 0.9 release.  Its source 
                code can be downloaded from git respository listed below, and free for the community to 
                continue supporting it moving forward.
            </para>
            <para>
                An Anjuta IDE plugin exists to make developing software within the Poky framework
                easier for the application developer. 
                It presents a graphical IDE with which you can cross compile an application 
                then deploy and execute the output in a 
                QEMU emulation session. 
                It also supports cross debugging and profiling.
            </para>
            <para>
                To use the plugin, a toolchain and SDK built by Poky is required,  
                Anjuta, it's development headers and the Anjuta plugin. 
                The Poky Anjuta plugin 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 plugin. 
                If you want to disable remote gdb debugging,
                please pass the <command>--diable-gdb-integration</command> switch when doing 
                configure.
            </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>Extract the tarball for the toolchain into / as root. 
                        The toolchain will be installed into <command>/opt/poky</command>.</listitem>
                        <listitem>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 uses glade for the UI.</listitem>
                        <listitem>To activate the plug-in go to Edit -> Preferences, then choose
                        General from the left hand side. 
                        Choose the Installed plug-ins tab, scroll down to Poky SDK and 
                        check the box.</listitem>
                    </orderedlist>
                    The plug-in is now activated but not configured.  
                    See the next section to learn how to configure it.
                </para>
                </section>
                <section id="configuring-the-anjuta-plugin">
                <title>Configuring the Anjuta Plugin</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 set the following options:
                    <itemizedlist>
                        <listitem>SDK root: If you use an external toolchain you need to set 
                        SDK root. This is the root directory of the
                        SDK's sysroot. 
                        For an i586 SDK this will be <command>/opt/poky/</command>. 
                        This directory will contain <command>bin</command>, <command>include
                        </command>, <command>var</command> and so forth under your 
                        selected target architecture subdirectory 
                        <command>/opt/poky/sysroot/i586-poky-linux/</command>. 
                        The cross comple tools you need are in 
                        <command>/opt/poky/sysroot/i586-pokysdk-linux/</command>.</listitem>
                        <listitem>Poky root: If you have a local poky build tree, you need to 
                        set the Poky root. 
                        This is the root directory of the poky build tree.
                        If you build your i586 target architecture under the subdirectory of 
                        <command>build_x86</command> within your poky tree, the Poky root directory
                        should be <command>$&lt;poky_tree&gt;/build_x86/</command>.</listitem>
                        <listitem>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 
                        name. 
                        For example, "i586-poky-linux" is extracted from the
                        set up script file 
                        <command>/opt/poky/environment-setup-i586-poky-linux</command>.</listitem>
                        <listitem>Kernel: Use the file chooser to select the kernel to use 
                        with QEMU.</listitem>
                        <listitem>Root filesystem: Use the file chooser to select the root 
                        filesystem directory.  This directory is where you use the 
                        <command>poky-extract-sdk</command> to extract the poky-image-sdk 
                        tarball.</listitem>
                     </itemizedlist>
                </para>
                </section>
                <section id="using-the-anjuta-plug-in">
                <title>Using the Anjuta Plug-in</title>
                <para>
                    This section uses an example that cross-compiles a project, deploys it into
                    QEMU, runs a debugger against it and then does a system wide profile.
                <orderedlist>
                    <listitem>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.</listitem>
                    <listitem>Select 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.</listitem>
                    <listitem>Start QEMU by selecting Tools -> Start QEMU.  This menu selection
                    starts QEMU and will show any error messages in the message view. 
                    Once Poky has fully booted within QEMU you can now deploy the project 
                    into it.</listitem>
                    <listitem>Once the project is built and you have QEMU running choose 
                    Tools -> Deploy.  
                    This selection installs the package into a temporary
                    directory and then copies using rsync over SSH into the target. 
                    Progress and messages appear in the message view.</listitem>
                    <listitem>To debug a program installed onto the target choose 
                    Tools -> Debug remote. 
                    This selection prompts you for the local binary to debug and also the 
                    command line to run on the target. 
                    The command line to run should include the full path to the to binary 
                    installed in the target. 
                    This will start a gdbserver over SSH on the target and also an instance 
                    of a cross-gdb in a local terminal. 
                    This will be preloaded to connect to the server and use the SDK root to 
                    find symbols. 
                    This gdb will connect to the target and load in various libraries and the 
                    target program. 
                    You should setup any breakpoints or watchpoints now since you might not 
                    be able to interrupt the execution later. 
                    You can stop the debugger on the target using Tools -> Stop debugger.</listitem>
                    <listitem>It is also possible to execute a command in the target over SSH, 
                    the appropriate environment will be be set for the execution. 
                    Choose Tools -> Run remote to do this. 
                    This selection opens a terminal with the SSH command inside.</listitem>
                    <listitem>To do a system wide profile against the system running in QEMU choose 
                    Tools -> Profile remote. 
                    This selection starts up OProfileUI with the appropriate parameters to 
                    connect to the server running inside QEMU and also supplies the path 
                    to the debug information necessary to get a useful profile.</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 
            that applications can be developed within QEMU in the same was as a 
            normal system. Using qemux86 on an x86 machine is fast since the 
            guest and host architectures match, qemuarm is 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 too. If <command>runqemu</command> was used to start
            QEMU, and distccd is present on the host system, any bitbake cross 
            compiling toolchain available from the build system will automatically
            be used from within qemu simply by calling distcc 
            (<command>export CC="distcc"</command> can be set in the enviroment).
            Alterntatively, if a suitable SDK/toolchain is present in 
            <filename class="directory">/opt/poky</filename> it will also
            automatically be used.
        </para>

        <para>
            There are several options for connecting into the emulated system. 
            QEMU provides a framebuffer interface which has standard consoles 
            available. There is also a serial connection available which has a 
            console to the system running on it and IP networking as standard. 
            The images have a dropbear ssh server running with the root password 
            disabled allowing standard ssh and scp commands to work. The images
            also contain an NFS server exporting the guest's root filesystem 
            allowing that 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>
            Here, we build the package, change into the work directory for the package,
            change a file, then recompile the package. Instead of using sh like this,
            you can also use two different terminals. The risk with working like this 
            is that a command like unpack could wipe out the changes you've made to the
            work directory so 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. The resulting patches can be copied 
            into the recipe directory and used 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 Sections <link
            linkend="usingpoky-components-bitbake">2.1.1</link> and <link 
            linkend="usingpoky-debugging-taskrunning">2.4.2</link>.
        </para>
        </section>

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

        <para>
            When debugging certain commands or even to just edit packages, the
            'devshell' can be a useful tool. To start it you run a command like:
        </para>

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

        <para>
            which will open a terminal with a shell prompt within the Poky 
            environment. This means PATH is setup to include the cross toolchain, 
            the pkgconfig variables are setup to find the right .pc files, 
            configure will be able to find the Poky site files etc. Within this 
            environment, you can run configure or compile command as if they 
            were being run by Poky itself. You are also changed into the 
            source (<glossterm><link linkend='var-S'>S</link></glossterm>) 
            directory automatically. When finished with the shell just exit it
            or close the terminal window.
        </para>

        <para>
            The default shell used by devshell is the gnome-terminal. Other 
            forms of terminal can also be used by setting the <glossterm>
            <link linkend='var-TERMCMD'>TERMCMD</link></glossterm> and <glossterm>
            <link linkend='var-TERMCMDRUN'>TERMCMDRUN</link></glossterm> variables 
            in local.conf. For examples of the other options available, see 
            <filename>meta/conf/bitbake.conf</filename>. An external shell is 
            launched rather than opening directly into the original terminal 
            window to make interaction with bitbakes multiple threads easier 
            and also allow a client/server split of bitbake in the future 
            (devshell will still work over X11 forwarding or similar).
        </para>

        <para>
            It is worth remembering that inside devshell you need to use the full
            compiler name such as <command>arm-poky-linux-gnueabi-gcc</command> 
            instead of just <command>gcc</command> and the same applies to other 
            applications from gcc, bintuils, libtool etc. 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 which pulls from an external SCM it 
            is possible to have Poky notice new changes added to the 
            SCM and then build the latest version. This only works for SCMs
            where its possible to get a sensible revision number for changes.
            Currently it works for svn, git and bzr repositories.
        </para>

        <para>
            To enable this behaviour it is simply a case of adding <glossterm>
            <link linkend='var-SRCREV'>SRCREV</link></glossterm>_pn-<glossterm>
            <link linkend='var-PN'>PN</link></glossterm> = "${AUTOREV}" to 
            local.conf 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>
        <ulink url="http://sourceware.org/gdb/">GDB</ulink> (The GNU Project Debugger)
        allows you to examine running programs to understand and fix problems and
        also to perform postmortem style analsys of program crashes. It is available
        as a package within poky and installed by default in sdk images. It works best
        when -dbg packages for the application being debugged are installed as the 
        extra symbols give more meaningful output from GDB. 
    </para>

    <para>
        Sometimes, due to memory or disk space constraints, it is not possible
        to use GDB directly on the remote target to debug applications. This is 
        due to the fact that
        GDB needs to load the debugging information and the binaries of the
        process being debugged. GDB then needs to perform many
        computations to locate information such as function names, variable
        names and values, stack traces, etc. even before starting the debugging
        process. This places load on the target system and can alter the
        characteristics of the program being debugged.
    </para>
    <para>
        This is where GDBSERVER comes into play as it runs on the remote target
        and does not load any debugging information from the debugged process.
        Instead, the debugging information processing is done by a GDB instance
        running on a distant 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 some memory regions of that debugged
        program. All the debugging information loading and processing as well
        as the heavy debugging duty is done by the host GDB, giving the 
        GDBSERVER running on the target a chance to remain small and fast.
    </para>
    <para>
        As the host GDB is responsible for loading the debugging information and 
        doing the necessary processing to make actual debugging happen, the 
        user has to make sure it can access the unstripped binaries complete
        with their debugging information and compiled with no optimisations. The
        host GDB must also have local access to all the libraries used by the 
        debugged program. On the remote target the binaries can remain stripped
        as GDBSERVER does not need any debugging information there. However they 
        must also be compiled without optimisation matching the host's binaries.
    </para>

    <para>
        The binary being debugged on the remote target machine is hence referred
        to as the 'inferior' in keeping with GDB documentation and terminology.
        Further documentation on GDB, is available on 
        <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 gdbserver package (which needs the libthread-db1
            package).
        </para>
        <para>
            To launch GDBSERVER on the target and make it ready to "debug" a 
            program located at <emphasis>/path/to/inferior</emphasis>, connect
            to the target and launch:
            <programlisting>$ gdbserver localhost:2345 /path/to/inferior</programlisting>
            After that, gdbserver should be listening on port 2345 for debugging
            commands coming from a remote GDB process running on the host computer.
            Communication between the GDBSERVER and the host GDB will be 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, described in the
            following sections.
        </para>

        <section id="platdev-gdb-remotedebug-launch-gdb-buildcross">
            <title>Build the cross GDB package</title>
            <para>
                A suitable gdb cross binary is required which runs on your host computer but
                knows about the the ABI of the remote target. This can be obtained from
                the the Poky toolchain, e.g. 
                <filename>/usr/local/poky/eabi-glibc/arm/bin/arm-poky-linux-gnueabi-gdb</filename> 
                which "arm" is the target architecture and "linux-gnueabi" the target ABI.
            </para>

            <para>
                Alternatively this can be built directly by Poky. To do this you would build 
                the gdb-cross package so for example you would run:
                <programlisting>bitbake gdb-cross</programlisting>
                Once built, the cross gdb binary can be found at
                <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 needs to be available to GDB complete with all debugging 
                symbols in order to get the best possible results along with any libraries
                the inferior depends on and their debugging symbols. There are a number of
                ways this can be done.
            </para>

            <para>
                Perhaps the easiest is to have an 'sdk' image corresponding to the plain
                image installed on the device. In the case of 'pky-image-sato', 
                'poky-image-sdk' would contain suitable symbols. The sdk images already 
                have the debugging symbols installed so its just a question expanding the 
                archive to some location and telling GDB where this is. 
            </para>

            <para>
                Alternatively, poky can build a custom directory of files for a specific 
                debugging purpose by reusing its tmp/rootfs directory, on the host computer
                in a slightly different way to normal. This directory contains the contents 
                of the last built image. This process assumes the image running on the
                target was the last image to be built by Poky, the package <emphasis>foo</emphasis>
                contains the inferior binary to be debugged has been built without without 
                optimisation and has debugging information available.
            </para>
            <para>
                Firstly you want to install the <emphasis>foo</emphasis> package to tmp/rootfs 
                by doing:
                </para>
                <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>
                then,
                </para>
                <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>
                which installs the debugging information too.
            </para>

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

            <title>Launch the host GDB</title>
            <para>
                To launch the host GDB, run the cross gdb binary identified above with
                the inferior binary specified on the commandline:
                <programlisting>&lt;target-abi&gt;-gdb rootfs/usr/bin/foo</programlisting>
                This loads the binary of program <emphasis>foo</emphasis>
                as well as its debugging information. Once the gdb prompt
                appears, you must instruct GDB to load all the libraries
                of the inferior from tmp/rootfs:
                <programlisting>set solib-absolute-prefix /path/to/tmp/rootfs</programlisting>
                where <filename>/path/to/tmp/rootfs</filename> must be 
                the absolute path to <filename>tmp/rootfs</filename> or wherever the 
                binaries with debugging information are located.
            </para>
            <para>
                Now, tell GDB to connect to the GDBSERVER running on the remote target:
                <programlisting>target remote remote-target-ip-address:2345</programlisting>
                Where remote-target-ip-address is the IP address of the
                remote target where the GDBSERVER is running. 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>
                Debugging can now proceed as normal, as if the debugging were being done on the 
                local machine, for example to tell GDB to break in the <emphasis>main</emphasis> 
                function, for instance:
                <programlisting>break main</programlisting>
                and then to tell GDB to "continue" the inferior execution,
                <programlisting>continue</programlisting>
            </para>
            <para>
                For more information about using GDB please 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 to finding performance 
        bottlenecks in both userspace software and the kernel. It provides 
        answers to questions like "Which functions does my application spend 
        the most time in when doing X?". Poky is well integrated with OProfile
        to make profiling applications on target hardware straightforward.
    </para>

    <para>
        To use OProfile you need an image with 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 
        will take place. This can be achieved with "dbg-pkgs" in <glossterm><link 
        linkend='var-IMAGE_FEATURES'>IMAGE_FEATURES</link></glossterm> or by
        installing the appropriate -dbg packages. For 
        successful call graph analysis the binaries must preserve the frame 
        pointer register and hence should be compiled with the 
        "-fno-omit-framepointer" flag. In Poky this can be achieved with 
        <glossterm><link linkend='var-SELECTED_OPTIMIZATION'>SELECTED_OPTIMIZATION
        </link></glossterm> = "-fexpensive-optimizations -fno-omit-framepointer 
        -frename-registers -O2" or by setting <glossterm><link 
        linkend='var-DEBUG_BUILD'>DEBUG_BUILD</link></glossterm> = "1" in 
        local.conf (the latter will also add extra debug information making the
        debug packages large).
    </para>

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

        <para>
            All the profiling work can be performed on the target device. A 
            simple OProfile session might look like:
        </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>
            Here, the reset command clears any previously profiled data, 
            OProfile is then started. The options used to start OProfile mean
            dynamic library data is kept separately per application, kernel 
            profiling is disabled and callgraphing is enabled up to 5 levels 
            deep. 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). The profile is 
            then stopped and the results viewed with opreport with options
            to see the separate library symbols and callgraph information.
        </para>
        <para>
            Callgraphing means OProfile not only logs infomation about which 
            functions time is being spent in but also which functions
            called those functions (their parents) and which functions that 
            function calls (its children). The higher the callgraphing depth, 
            the more accurate the results but this also increased the loging 
            overhead so it should be used with caution. On ARM, binaries need 
            to have the frame pointer enabled for callgraphing to work (compile
            with the gcc option -fno-omit-framepointer).
        </para>
        <para>
            For more information on using OProfile please 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>

<!-- DISBALED, Need a more 'contexual' 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 the <filename>opimport</filename> program is needed. 
            This is not included in standard Debian OProfile packages but an 
            OProfile package with this addition is also available from the <ulink
                url='http://debian.o-hand.com/'>OpenedHand repository</ulink>.
            We recommend using OProfile 0.9.3 or greater. Other patches to
            OProfile may be needed for recent OProfileUI features, but Poky 
            usually includes all needed patches on the target device.  Please 
            see the <ulink
                url='http://svn.o-hand.com/repos/oprofileui/trunk/README'>
                OProfileUI README</ulink> for up to date information, and the 
            <ulink url="http://labs.o-hand.com/oprofileui">OProfileUI website
            </ulink> for more information on the OProfileUI project. 
        </para>

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

            <para>
                This assumes a working network connection with the target 
                hardware. In this case you just need to run <command>
                "oprofile-server"</command> on the device. By default it listens 
                on port 4224. This can be changed with the <parameter>--port</parameter> command line 
                option.

            </para>

            <para>
                The client program is called <command>oprofile-viewer</command>. The  
                UI is relatively straightforward, the key functionality is accessed
                through the buttons on the toolbar (which are duplicated in the 
                menus.) These buttons are:
            </para>

            <itemizedlist>
                <listitem>
                    <para>
                        Connect - connect to the remote host, the IP address or hostname for the
                        target can be supplied here.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Disconnect - disconnect from the target.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Start - start the profiling on the device.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Stop - stop the profiling on the device and download the data to the local
                        host. This will generate the profile and show it in the viewer.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Download - download the data from the target, generate the profile and show it
                        in the viewer.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Reset - reset the sample data on the device. This will remove the sample
                        information that was collected on a previous sampling run. Ensure you do this
                        if you do not want to include old sample information.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Save - save the data downloaded from the target to another directory for later
                        examination.
                    </para>
                </listitem>
                <listitem>
                    <para>
                        Open - load data that was previously saved.
                    </para>
                </listitem>
            </itemizedlist>

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

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

            <para>
                If you wish to profile into the kernel, this is possible, you just need to ensure
                a vmlinux file matching the running kernel is available. In Poky this is usually 
                located in /boot/vmlinux-KERNELVERSION, 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 ensuring a matching package is 
                installed (<command> opkg install kernel-vmlinux</command>. These are automatically 
                installed into development and profiling images alongside OProfile. There is a 
                configuration option within the OProfileUI settings page where the location of 
                the vmlinux file can be entered. 
            </para>

            <para>
                Waiting for debug symbols to transfer from the device can be slow and it's not     
                always necessary to actually have them on 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'>GDB remote debug
                section</link> covers how to create such a directory with Poky and the location 
                of this directory can again be specified in the OProfileUI settings dialog. If
                specified, it will be used where the file checksums match those on the system 
                being profiled.
            </para>
        </section>
        <section id="platdev-oprofile-oprofileui-offline">
            <title>Offline mode</title>

            <para>
                If no network access to the target is available an archive for processing in
                'oprofile-viewer' can be generated with the following set of command.
            </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>
                Where my_archive is the name of the archive directory where you would like the
                profile archive to be kept. The directory will be created for you. This can
                then be copied to another host and loaded using 'oprofile-viewer''s open
                functionality. The archive will be converted if necessary.
            </para>
        </section>
    </section>
</section>



</chapter> 
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