Copyright © 2010-2013 Linux Foundation
Permission is granted to copy, distribute and/or modify this document under the terms of the Creative Commons Attribution-Share Alike 2.0 UK: England & Wales as published by Creative Commons.
| Revision History | |
|---|---|
| Revision 1.0 | 6 April 2011 |
| Released with the Yocto Project 1.0 Release. | |
| Revision 1.0.1 | 23 May 2011 |
| Released with the Yocto Project 1.0.1 Release. | |
| Revision 1.1 | 6 October 2011 |
| Released with the Yocto Project 1.1 Release. | |
| Revision 1.2 | April 2012 |
| Released with the Yocto Project 1.2 Release. | |
| Revision 1.3 | October 2012 |
| Released with the Yocto Project 1.3 Release. | |
| Revision 1.3.1 | April 2013 |
| Released with the Yocto Project 1.3.1 Release. | |
Table of Contents
Table of Contents
Welcome to the Yocto Project Application Developer's Guide. This manual provides information that lets you begin developing applications using the Yocto Project.
The Yocto Project provides an application development environment based on an Application Development Toolkit (ADT) and the availability of stand-alone cross-development toolchains and other tools. This manual describes the ADT and how you can configure and install it, how to access and use the cross-development toolchains, how to customize the development packages installation, how to use command line development for both Autotools-based and Makefile-based projects, and an introduction to the Eclipse Yocto Plug-in.
Part of the Yocto Project development solution is an Application Development Toolkit (ADT). The ADT provides you with a custom-built, cross-development platform suited for developing a user-targeted product application.
Fundamentally, the ADT consists of the following:
An architecture-specific cross-toolchain and matching sysroot both built by the OpenEmbedded build system, which uses Poky. The toolchain and sysroot are based on a metadata configuration and extensions, which allows you to cross-develop on the host machine for the target hardware.
The Eclipse IDE Yocto Plug-in.
The Quick EMUlator (QEMU), which lets you simulate target hardware.
Various user-space tools that greatly enhance your application development experience.
The cross-toolchain consists of a cross-compiler, cross-linker, and cross-debugger that are used to develop user-space applications for targeted hardware. This toolchain is created either by running the ADT Installer script, a toolchain installer script, or through a Build Directory that is based on your metadata configuration or extension for your targeted device. The cross-toolchain works with a matching target sysroot.
The matching target sysroot contains needed headers and libraries for generating binaries that run on the target architecture. The sysroot is based on the target root filesystem image that is built by the OpenEmbedded build system Poky and uses the same metadata configuration used to build the cross-toolchain.
The Eclipse IDE is a popular development environment and it fully supports development using the Yocto Project. When you install and configure the Eclipse Yocto Project Plug-in into the Eclipse IDE, you maximize your Yocto Project experience. Installing and configuring the Plug-in results in an environment that has extensions specifically designed to let you more easily develop software. These extensions allow for cross-compilation, deployment, and execution of your output into a QEMU emulation session. You can also perform cross-debugging and profiling. The environment also supports a suite of tools that allows you to perform remote profiling, tracing, collection of power data, collection of latency data, and collection of performance data.
For information about the application development workflow that uses the Eclipse IDE and for a detailed example of how to install and configure the Eclipse Yocto Project Plug-in, see the "Working Within Eclipse" section of the Yocto Project Development Manual.
The QEMU emulator allows you to simulate your hardware while running your application or image. QEMU is made available a number of ways:
If you use the ADT Installer script to install ADT, you can specify whether or not to install QEMU.
If you have downloaded a Yocto Project release and unpacked it to create a Source Directory and you have sourced the environment setup script, QEMU is installed and automatically available.
If you have installed the cross-toolchain tarball and you have sourcing the toolchain's setup environment script, QEMU is also installed and automatically available.
User-space tools are included as part of the distribution. You will find these tools helpful during development. The tools include LatencyTOP, PowerTOP, OProfile, Perf, SystemTap, and Lttng-ust. These tools are common development tools for the Linux platform.
LatencyTOP: LatencyTOP focuses on latency that causes skips in audio, stutters in your desktop experience, or situations that overload your server even when you have plenty of CPU power left. You can find out more about LatencyTOP at http://www.latencytop.org/.
PowerTOP: Helps you determine what software is using the most power. You can find out more about PowerTOP at https://01.org/powertop/.
OProfile: A system-wide profiler for Linux systems that is capable of profiling all running code at low overhead. You can find out more about OProfile at http://oprofile.sourceforge.net/about/.
Perf: Performance counters for Linux used to keep track of certain types of hardware and software events. For more information on these types of counters see https://perf.wiki.kernel.org/ and click on “Perf tools.”
SystemTap: A free software infrastructure that simplifies information gathering about a running Linux system. This information helps you diagnose performance or functional problems. SystemTap is not available as a user-space tool through the Eclipse IDE Yocto Plug-in. See http://sourceware.org/systemtap for more information on SystemTap.
Lttng-ust: A User-space Tracer designed to provide detailed information on user-space activity. See http://lttng.org/ust for more information on Lttng-ust.
Table of Contents
In order to develop applications, you need set up your host development system. Several ways exist that allow you to install cross-development tools, QEMU, the Eclipse Yocto Plug-in, and other tools. This chapter describes how to prepare for application development.
The following list describes installation methods that set up varying degrees of tool
availabiltiy on your system.
Regardless of the installation method you choose,
you must source the cross-toolchain
environment setup script before you use a toolchain.
See the "Setting Up the
Cross-Development Environment" section for more information.
Avoid mixing installation methods when installing toolchains for different architectures. For example, avoid using the ADT Installer to install some toolchains and then hand-installing cross-development toolchains by running the toolchain installer for different architectures. Mixing installation methods can result in situations where the ADT Installer becomes unreliable and might not install the toolchain.
If you must mix installation methods, you might avoid problems by deleting
/var/lib/opkg, thus purging the opkg package
metadata
Use the ADT Installer Script: This method is the recommended way to install the ADT because it automates much of the process for you. For example, you can configure the installation to install the QEMU emulator and the user-space NFS, specify which root filesystem profiles to download, and define the target sysroot location.
Use an Existing Toolchain: Using this method, you select and download an architecture-specific toolchain installer and then run the script to hand-install the toolchain. If you use this method, you just get the cross-toolchain and QEMU - you do not get any of the other mentioned benefits had you run the ADT Installer script.
Use the Toolchain from within the Build Directory: If you already have a Build Directory, you can build the cross-toolchain within the directory. However, like the previous method mentioned, you only get the cross-toolchain and QEMU - you do not get any of the other benefits without taking separate steps.
To run the ADT Installer, you need to get the ADT Installer tarball, be sure you have the necessary host development packages that support the ADT Installer, and then run the ADT Installer Script.
For a list of the host packages needed to support ADT installation and use, see the "ADT Installer Extras" lists in the "Required Packages for the Host Development System" section of the Yocto Project Reference Manual.
The ADT Installer is contained in the ADT Installer tarball. You can download the tarball into any directory from the Index of Releases, specifically at http://downloads.yoctoproject.org/releases/yocto/yocto-1.3.1/adt_installer. Or, you can use BitBake to generate the tarball inside the existing Build Directory.
If you use BitBake to generate the ADT Installer tarball, you must
source the environment setup script
(oe-init-build-env) located
in the Source Directory before running the bitbake
command that creates the tarball.
The following example commands download the Poky tarball, set up the
Source Directory,
set up the environment while also creating the default Build Directory,
and run the bitbake command that results in the tarball
~/yocto-project/build/tmp/deploy/sdk/adt_installer.tar.bz2:
$ cd ~
$ mkdir yocto-project
$ cd yocto-project
$ wget http://downloads.yoctoproject.org/releases/yocto/yocto-1.3.1/poky-danny-8.0.1.tar.bz2
$ tar xjf poky-danny-8.0.1.tar.bz2
$ source poky-danny-8.0.1/oe-init-build-env
$ bitbake adt-installer
Before running the ADT Installer script, you need to unpack the tarball.
You can unpack the tarball in any directory you wish.
For example, this command copies the ADT Installer tarball from where
it was built into the home directory and then unpacks the tarball into
a top-level directory named adt-installer:
$ cd ~
$ cp ~/poky/build/tmp/deploy/sdk/adt_installer.tar.bz2 $HOME
$ tar -xjf adt_installer.tar.bz2
Unpacking the tarball creates the directory adt-installer,
which contains the ADT Installer script (adt_installer),
its configuration file (adt_installer.conf), a
scripts directory, and an opkg
directory.
Before you run the ADT Installer script, however, you should examine the ADT Installer configuration file and be sure you are going to get what you want. Your configurations determine which kernel and filesystem image are downloaded.
The following list describes the configurations you can define for the ADT Installer.
For configuration values and restrictions, see the comments in
the adt-installer.conf file:
YOCTOADT_REPO: This area
includes the IPKG-based packages and the root filesystem upon which
the installation is based.
If you want to set up your own IPKG repository pointed to by
YOCTOADT_REPO, you need to be sure that the
directory structure follows the same layout as the reference directory
set up at http://adtrepo.yoctoproject.org.
Also, your repository needs to be accessible through HTTP.
Additionally, you will need to edit a second configuration file
located in the adt-installer/opkg directory.
The configuration file you edit depends on your host development
system.
For 64-bit systems, edit the opkg-sdk-x86_64.conf
file.
If your host development system is 32-bit, edit the
opkg-sdk-i686.conf file.
For both cases, you need to make sure you are pointing to
the IPKG-based packages specified by the
YOCTOADT_REPO.
Here is an example for a 64-bit development system:
src yp-x86_64-nativesdk http://my_repo/yp-1.3.1/adt-ipk/x86_64-nativesdk
YOCTOADT_TARGETS: The machine
target architectures for which you want to set up cross-development
environments.
YOCTOADT_QEMU: Indicates whether
or not to install the emulator QEMU.
YOCTOADT_NFS_UTIL: Indicates whether
or not to install user-mode NFS.
If you plan to use the Eclipse IDE Yocto plug-in against QEMU,
you should install NFS.
portmap or rpcbind.
If you are running rpcbind, you will also need to add the
-i option when rpcbind starts up.
Please make sure you understand the security implications of doing this.
You might also have to modify your firewall settings to allow
NFS booting to work.YOCTOADT_ROOTFS_<arch>: The root
filesystem images you want to download from the
YOCTOADT_IPKG_REPO repository.
YOCTOADT_TARGET_SYSROOT_IMAGE_<arch>: The
particular root filesystem used to extract and create the target sysroot.
The value of this variable must have been specified with
YOCTOADT_ROOTFS_<arch>.
For example, if you downloaded both minimal and
sato-sdk images by setting
YOCTOADT_ROOTFS_<arch>
to "minimal sato-sdk", then YOCTOADT_ROOTFS_<arch>
must be set to either minimal or
sato-sdk.
YOCTOADT_TARGET_SYSROOT_LOC_<arch>: The
location on the development host where the target sysroot is created.
After you have configured the adt_installer.conf file,
run the installer using the following command.
Be sure that you are not trying to use cross-compilation tools.
When you run the installer, the environment must use a
host gcc:
$ cd ~/adt-installer
$ ./adt_installer
Once the installer begins to run, you are asked to enter the location for
cross-toolchain installation.
The default location is /opt/poky/<release>.
After selecting the location, you are prompted to run in
interactive or silent mode.
If you want to closely monitor the installation, choose “I” for interactive
mode rather than “S” for silent mode.
Follow the prompts from the script to complete the installation.
Once the installation completes, the ADT, which includes the cross-toolchain, is installed.
You will notice environment setup files for the cross-toolchain in
/opt/poky/1.3.1,
and image tarballs in the adt-installer
directory according to your installer configurations, and the target sysroot located
according to the YOCTOADT_TARGET_SYSROOT_LOC_<arch> variable
also in your configuration file.
If you want to simply install the cross-toolchain by hand, you can do so by running the toolchain installer. If you use this method to install the cross-toolchain and you still need to install the target sysroot, you will have to extract and install sysroot separately. For information on how to do this, see the "Extracting the Root Filesystem" section.
Follow these steps:
Go to
http://downloads.yoctoproject.org/releases/yocto/yocto-1.3.1/toolchain/
and find the folder that matches your host development system
(i.e. i686 for 32-bit machines or
x86-64 for 64-bit machines).
Go into that folder and download the toolchain installer whose name
includes the appropriate target architecture.
For example, if your host development system is an Intel-based 64-bit system and
you are going to use your cross-toolchain for an Intel-based 32-bit target, go into the
x86_64 folder and download the following installer:
poky-eglibc-x86_64-i586-toolchain-gmae-1.3.1.sh
As an alternative to steps one and two, you can build the toolchain installer
if you have a Build Directory.
If you need GMAE, you should use the bitbake meta-toolchain-gmae
command.
The resulting installation script when run will support such development.
However, if you are not concerned with GMAE,
you can generate the toolchain installer using
bitbake meta-toolchain.
Use the appropriate bitbake command only after you have
sourced the poky-danny-8.0.1/oe-init-build-env script located in the Source
Directory.
When the bitbake command completes, the toolchain installer will
be in tmp/deploy/sdk in the Build Directory.
Once you have the installer, run it to install the toolchain. You must change the permissions on the toolchain installer script so that it is executable.
The following command shows how to run the installer given a toolchain tarball
for a 64-bit development host system and a 32-bit target architecture.
The example assumes the toolchain installer is located in ~/Downloads/.
$ ~/Downloads/poky-eglibc-x86_64-i586-toolchain-gmae-1.3.1.sh
Once the tarball is expanded, the cross-toolchain is installed. You will notice environment setup files for the cross-toolchain in the directory.
A final way of making the cross-toolchain available is to use BitBake
to generate the toolchain within an existing
Build Directory.
This method does not install the toolchain into the
/opt directory.
As with the previous method, if you need to install the target sysroot, you must
do that separately as well.
Follow these steps to generate the toolchain into the Build Directory:
Source the environment setup script
oe-init-build-env located in the
Source Directory.
At this point, you should be sure that the
MACHINE variable
in the local.conf file found in the
conf directory of the Build Directory
is set for the target architecture.
Comments within the local.conf file list the values you
can use for the MACHINE variable.
MACHINE variable in the
local.conf file and re-run the BitBake
command.Run bitbake meta-ide-support to complete the
cross-toolchain generation.
source the environment setup script and before you run
the bitbake command, the command might not work.
Be sure to run the bitbake command immediately
after checking or editing the local.conf but without
changing out of your working directory.
Once the bitbake command finishes,
the cross-toolchain is generated and populated within the Build Directory.
You will notice environment setup files for the cross-toolchain in the
Build Directory in the tmp directory.
Setup script filenames contain the strings environment-setup.
Be aware that when you use this method to install the toolchain you still need to separately extract and install the sysroot filesystem. For information on how to do this, see the "Extracting the Root Filesystem" section.
Before you can develop using the cross-toolchain, you need to set up the
cross-development environment by sourcing the toolchain's environment setup script.
If you used the ADT Installer or hand-installed cross-toolchain,
then you can find this script in the /opt/poky/1.3.1
directory.
If you installed the toolchain in the
Build Directory,
you can find the environment setup
script for the toolchain in the Build Directory's tmp directory.
Be sure to run the environment setup script that matches the architecture for
which you are developing.
Environment setup scripts begin with the string “environment-setup”
and include as part of their name the architecture.
For example, the toolchain environment setup script for a 64-bit IA-based architecture would
be the following:
/opt/poky/1.3.1/environment-setup-x86_64-poky-linux
You will need to have a kernel and filesystem image to boot using your hardware or the QEMU emulator. Furthermore, if you plan on booting your image using NFS or you want to use the root filesystem as the target sysroot, you need to extract the root filesystem.
To get the kernel and filesystem images, you either have to build them or download pre-built versions. You can find examples for both these situations in the "A Quick Test Run" section of the Yocto Project Quick Start.
The Yocto Project ships basic kernel and filesystem images for several
architectures (x86, x86-64,
mips, powerpc, and arm)
that you can use unaltered in the QEMU emulator.
These kernel images reside in the release
area - http://downloads.yoctoproject.org/releases/yocto/yocto-1.3.1/machines
and are ideal for experimentation using Yocto Project.
For information on the image types you can build using the OpenEmbedded build system,
see the
"Images" chapter in
the Yocto Project Reference Manual.
If you are planning on developing against your image and you are not building or using one of the Yocto Project development images (e.g. core-image-*-dev), you must be sure to include the development packages as part of your image recipe.
Furthermore, if you plan on remotely deploying and debugging your
application from within the
Eclipse IDE, you must have an image that contains the Yocto Target Communication
Framework (TCF) agent (tcf-agent).
By default, the Yocto Project provides only one type pre-built image that contains the
tcf-agent.
And, those images are SDK (e.g.core-image-sato-sdk).
If you want to use a different image type that contains the tcf-agent,
you can do so one of two ways:
Modify the conf/local.conf configuration in
the Build Directory
and then rebuild the image.
With this method, you need to modify the
EXTRA_IMAGE_FEATURES
variable to have the value of "tools-debug" before rebuilding the image.
Once the image is rebuilt, the tcf-agent will be included
in the image and is launched automatically after the boot.
Manually build the tcf-agent.
To build the agent, follow these steps:
Be sure the ADT is installed as described in the "Installing the ADT and Toolchains" section.
Set up the cross-development environment as described in the "Setting Up the Cross-Development Environment" section.
Get the tcf-agent source code using
the following commands:
$ git clone http://git.eclipse.org/gitroot/tcf/org.eclipse.tcf.agent.git
$ cd agent
Modify the Makefile.inc file
for the cross-compilation environment by setting the
OPSYS and
MACHINE
variables according to your target.
Use the cross-development tools to build the
tcf-agent.
Before you "Make" the file, be sure your cross-tools are set up first.
See the "Makefile-Based Projects"
section for information on how to make sure the cross-tools are set up
correctly.
If the build is successful, the tcf-agent output will
be obj/$(OPSYS)/$(MACHINE)/Debug/agent.
Deploy the agent into the image's root filesystem.
You must extract the root filesystem if you want to boot the image using NFS or you want to use the root filesystem as the target sysroot. For example, the Eclipse IDE environment with the Eclipse Yocto Plug-in installed allows you to use QEMU to boot under NFS. Another example is if you want to develop your target application using the root filesystem as the target sysroot.
To extract the root filesystem, first source
the cross-development environment setup script and then
use the runqemu-extract-sdk command on the
filesystem image.
For example, the following commands set up the environment and then extract
the root filesystem from a previously built filesystem image tarball named
core-image-sato-sdk-qemux86-2011091411831.rootfs.tar.bz2.
The example extracts the root filesystem into the $HOME/qemux86-sato
directory:
$ source $HOME/poky/build/tmp/environment-setup-i586-poky-linux
$ runqemu-extract-sdk \
tmp/deploy/images/core-image-sato-sdk-qemux86-2011091411831.rootfs.tar.bz2 \
$HOME/qemux86-sato
In this case, you could now point to the target sysroot at
$HOME/qemux86-sato.
Table of Contents
Because the Yocto Project is suited for embedded Linux development, it is likely that you will need to customize your development packages installation. For example, if you are developing a minimal image, then you might not need certain packages (e.g. graphics support packages). Thus, you would like to be able to remove those packages from your target sysroot.
The OpenEmbedded build system supports the generation of sysroot files using three different Package Management Systems (PMS):
OPKG: A less well known PMS whose use
originated in the OpenEmbedded and OpenWrt embedded Linux projects.
This PMS works with files packaged in an .ipk format.
See http://en.wikipedia.org/wiki/Opkg for more
information about OPKG.
RPM: A more widely known PMS intended for GNU/Linux
distributions.
This PMS works with files packaged in an .rms format.
The build system currently installs through this PMS by default.
See http://en.wikipedia.org/wiki/RPM_Package_Manager
for more information about RPM.
Debian: The PMS for Debian-based systems
is built on many PMS tools.
The lower-level PMS tool dpkg forms the base of the Debian PMS.
For information on dpkg see
http://en.wikipedia.org/wiki/Dpkg.
Whichever PMS you are using, you need to be sure that the
PACKAGE_CLASSES
variable in the conf/local.conf
file is set to reflect that system.
The first value you choose for the variable specifies the package file format for the root
filesystem at sysroot.
Additional values specify additional formats for convenience or testing.
See the configuration file for details.
package*.bbclass
in the Yocto Project Reference Manual.
As an example, consider a scenario where you are using OPKG and you want to add
the libglade package to the target sysroot.
First, you should generate the ipk file for the
libglade package and add it
into a working opkg repository.
Use these commands:
$ bitbake libglade
$ bitbake package-index
Next, source the environment setup script found in the
Source Directory.
Follow that by setting up the installation destination to point to your
sysroot as <sysroot_dir>.
Finally, have an OPKG configuration file <conf_file>
that corresponds to the opkg repository you have just created.
The following command forms should now work:
$ opkg-cl –f <conf_file> -o <sysroot_dir> update
$ opkg-cl –f <cconf_file> -o <sysroot_dir> \
--force-overwrite install libglade
$ opkg-cl –f <cconf_file> -o <sysroot_dir> \
--force-overwrite install libglade-dbg
$ opkg-cl –f <conf_file> -o <sysroot_dir> \
--force-overwrite install libglade-dev
Table of Contents
Recall that earlier the manual discussed how to use an existing toolchain
tarball that had been installed into /opt/poky,
which is outside of the
Build Directory
(see the section "Using a Cross-Toolchain Tarball)".
And, that sourcing your architecture-specific environment setup script
initializes a suitable cross-toolchain development environment.
During the setup, locations for the compiler, QEMU scripts, QEMU binary,
a special version of pkgconfig and other useful
utilities are added to the PATH variable.
Variables to assist pkgconfig and autotools
are also defined so that,
for example, configure.sh can find pre-generated
test results for tests that need target hardware on which to run.
These conditions allow you to easily use the toolchain outside of the
OpenEmbedded build environment on both autotools-based projects and
Makefile-based projects.
For an Autotools-based project, you can use the cross-toolchain by just
passing the appropriate host option to configure.sh.
The host option you use is derived from the name of the environment setup
script in /opt/poky resulting from installation of the
cross-toolchain tarball.
For example, the host option for an ARM-based target that uses the GNU EABI
is armv5te-poky-linux-gnueabi.
Note that the name of the script is
environment-setup-armv5te-poky-linux-gnueabi.
Thus, the following command works:
$ configure --host=armv5te-poky-linux-gnueabi \
--with-libtool-sysroot=<sysroot-dir>
This single command updates your project and rebuilds it using the appropriate cross-toolchain tools.
configure script results in problems recognizing the
--with-libtool-sysroot=<sysroot-dir> option,
regenerate the script to enable the support by doing the following and then
re-running the script:
$ libtoolize --automake
$ aclocal -I ${OECORE_NATIVE_SYSROOT}/usr/share/aclocal \
[-I <dir_containing_your_project-specific_m4_macros>]
$ autoconf
$ autoheader
$ automake -a