Building with GCC¶
For building U-Boot you need a GCC compiler for your host platform. If you are not building on the target platform you further need a GCC cross compiler.
On Debian based systems the cross compiler packages are named gcc-<architecture>-linux-gnu.
You could install GCC and the GCC cross compiler for the ARMv8 architecture with
sudo apt-get install gcc gcc-aarch64-linux-gnu
Depending on the build targets further packages maybe needed
sudo apt-get install bc bison build-essential coccinelle \ device-tree-compiler dfu-util efitools flex gdisk graphviz imagemagick \ liblz4-tool libgnutls28-dev libguestfs-tools libncurses-dev \ libpython3-dev libsdl2-dev libssl-dev lz4 lzma lzma-alone openssl \ pkg-config python3 python3-asteval python3-coverage python3-filelock \ python3-pkg-resources python3-pycryptodome python3-pyelftools \ python3-pytest python3-pytest-xdist python3-sphinxcontrib.apidoc \ python3-sphinx-rtd-theme python3-subunit python3-testtools \ python3-virtualenv swig uuid-dev
On suse based systems the cross compiler packages are named cross-<architecture>-gcc<version>.
You could install GCC and the GCC 10 cross compiler for the ARMv8 architecture with
sudo zypper install gcc cross-aarch64-gcc10
Depending on the build targets further packages maybe needed.
zypper install bc bison flex gcc libopenssl-devel libSDL2-devel make \ ncurses-devel python3-devel python3-pytest swig
For building U-Boot on Alpine Linux at least the following packages are needed:
apk add alpine-sdk bc bison dtc flex linux-headers ncurses-dev \ openssl-dev perl python3 py3-setuptools python3-dev sdl2-dev
For some boards you have to build prerequisite files before you can build U-Boot, e.g. for the some boards you will need to build the ARM Trusted Firmware beforehand. Please, refer to the board specific documentation Board-specific doc.
Directory configs/ contains the template configuration files for the maintained boards following the naming scheme:
These files have been stripped of default settings. So you cannot use them directly. Instead their name serves as a make target to generate the actual configuration file .config. For instance the configuration template for the Odroid C2 board is called odroid-c2_defconfig. The corresponding .config file is generated by
You can adjust the configuration using
When cross compiling you will have to specify the prefix of the cross-compiler. You can either specify the value of the CROSS_COMPILE variable on the make command line or export it beforehand.
Assuming cross compiling on Debian for ARMv8 this would be
A list of available parameters for the make command can be obtained via
You can speed up compilation by parallelization using the -j parameter, e.g.
CROSS_COMPILE=aarch64-linux-gnu- make -j$(nproc)
Further important build parameters are
O=<dir> - generate all output files in directory <dir>, including .config
V=1 - verbose build
Boards that use CONFIG_OF_CONTROL (i.e. almost all of them) need the devicetree compiler (dtc). Those with CONFIG_PYLIBFDT need pylibfdt, a Python library for accessing devicetree data. Suitable versions of these are included in the U-Boot tree in scripts/dtc and built automatically as needed.
To use the system versions of these, use the DTC parameter, for example
In this case, dtc and pylibfdt are not built. The build checks that the version of dtc is new enough. It also makes sure that pylibfdt is present, if needed (see scripts_dtc in the Makefile).
Note that the Host tools are always built with the included version of libfdt so it is not possible to build U-Boot tools with a system libfdt, at present.
Link-time optimisation (LTO)¶
U-Boot supports link-time optimisation which can reduce the size of the final U-Boot binaries, particularly with SPL.
At present this can be enabled by ARM boards by adding CONFIG_LTO=y into the defconfig file. Other architectures are not supported. LTO is enabled by default for sandbox.
This does incur a link-time penalty of several seconds. For faster incremental builds during development, you can disable it by setting NO_LTO to 1.
Other build targets¶
A list of all make targets can be obtained via
Important ones are
clean - remove most generated files but keep the configuration
mrproper - remove all generated files + config + various backup files
The process for installing U-Boot on the target device is device specific. Please, refer to the board specific documentation Board-specific doc.