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 python3 python3-coverage \
  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

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

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.