Building with GCC

Dependencies

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.

Debian based

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 libguestfs-tools libncurses-dev libpython3-dev libsdl2-dev \
  libssl-dev lz4 lzma lzma-alone openssl pkg-config python3 \
  python3-coverage python3-pkg-resources python3-pycryptodome \
  python3-pyelftools python3-pytest python3-sphinxcontrib.apidoc \
  python3-sphinx-rtd-theme python3-virtualenv swig

SUSE based

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

Alpine Linux

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

Prerequisites

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.

Configuration

Directory configs/ contains the template configuration files for the maintained boards following the naming scheme:

<board name>_defconfig

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

make odroid-c2_defconfig

You can adjust the configuration using

make menuconfig

Building

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.

CROSS_COMPILE=<compiler-prefix> make

Assuming cross compiling on Debian for ARMv8 this would be

CROSS_COMPILE=aarch64-linux-gnu- make

Build parameters

A list of available parameters for the make command can be obtained via

make help

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

Devicetree compiler

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

DTC=/usr/bin/dtc make

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.

Other build targets

A list of all make targets can be obtained via

make help

Important ones are

  • clean - remove most generated files but keep the configuration

  • mrproper - remove all generated files + config + various backup files

Installation

The process for installing U-Boot on the target device is device specific. Please, refer to the board specific documentation Board-specific doc.