Prerequisites

Host System Dependencies

Ubuntu 22.04 / 24.04 / Debian 12

sudo apt-get update
sudo apt-get install -y \
    bc \
    bison \
    build-essential \
    coccinelle \
    device-tree-compiler \
    dfu-util \
    efitools \
    flex \
    gdisk \
    git \
    gpg \
    libgnutls28-dev \
    libncurses5-dev \
    libpython3-dev \
    libsdl2-dev \
    libssl-dev \
    lz4 \
    lzma \
    lzma-alone \
    make \
    openssl \
    pkg-config \
    python3 \
    python3-asteval \
    python3-cbor2 \
    python3-coverage \
    python3-filelock \
    python3-pkg-resources \
    python3-pycryptodome \
    python3-pyelftools \
    python3-pytest \
    python3-pytest-xdist \
    python3-setuptools \
    python3-sphinx \
    python3-sphinx-rtd-theme \
    python3-subunit \
    python3-tabulate \
    python3-testtools \
    swig \
    uuid-dev

Fedora / RHEL / Rocky Linux

sudo dnf install -y \
    bc bison dtc dfu-util flex gcc gcc-c++ git make \
    ncurses-devel openssl-devel swig python3-devel \
    python3-pyelftools python3-pytest python3-setuptools \
    libgnutls-devel lz4 lzma SDL2-devel

Arch Linux

sudo pacman -S base-devel bc bison dtc flex git \
    gnutls libssl ncurses openssl python python-pyelftools \
    python-pytest swig lz4 python-setuptools sdl2

---

Obtaining the Source Code (v2026.01)

Method 1: Clone and Checkout Tag (Recommended)

# Clone the official repository
git clone https://source.denx.de/u-boot/u-boot.git
cd u-boot

# Checkout the v2026.01 stable tag
git checkout v2026.01

# Verify the tag
git log --oneline -5
# Should show: "Merge tag 'v2026.01'" at top

Method 2: Clone with Specific Tag

git clone --branch v2026.01 --depth 1 \
    https://source.denx.de/u-boot/u-boot.git
cd u-boot

Method 3: GitHub Mirror

git clone --branch v2026.01 --depth 1 \
    https://github.com/u-boot/u-boot.git
cd u-boot

Verifying the Tag Signature (Optional but Recommended)

# Import Wolfgang Denk's GPG key (U-Boot maintainer)
gpg --keyserver keyserver.ubuntu.com --recv-keys 1A28909E
gpg --keyserver keyserver.ubuntu.com --recv-keys 87F9F635

# Verify the tag
git verify-tag v2026.01
# Expected: "Good signature from ..."

Creating a Working Branch

git checkout -b my-platform-bsp v2026.01

---

Cross-Compilation Toolchain Setup

U-Boot requires a cross-compiler matching the target architecture. The CROSS_COMPILE variable is a prefix for all compiler tools.

ARM 32-bit (Cortex-A/M)

# Download ARM GNU toolchain (GCC 13+)
# From: https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads

wget https://developer.arm.com/-/media/Files/downloads/gnu/13.3.rel1/binrel/\
arm-gnu-toolchain-13.3.rel1-x86_64-arm-none-eabi.tar.xz

tar xf arm-gnu-toolchain-13.3.rel1-x86_64-arm-none-eabi.tar.xz
export PATH=$PWD/arm-gnu-toolchain-13.3.rel1-x86_64-arm-none-eabi/bin:$PATH
export CROSS_COMPILE=arm-none-eabi-

# Verify
arm-none-eabi-gcc --version

ARM 64-bit (AArch64 / Cortex-A53/A55/A72/A76)

wget https://developer.arm.com/-/media/Files/downloads/gnu/13.3.rel1/binrel/\
arm-gnu-toolchain-13.3.rel1-x86_64-aarch64-none-linux-gnu.tar.xz

tar xf arm-gnu-toolchain-13.3.rel1-x86_64-aarch64-none-linux-gnu.tar.xz
export PATH=$PWD/arm-gnu-toolchain-13.3.rel1-x86_64-aarch64-none-linux-gnu/bin:$PATH
export CROSS_COMPILE=aarch64-none-linux-gnu-

RISC-V 64-bit

# Using riscv-gnu-toolchain
sudo apt-get install gcc-riscv64-linux-gnu
export CROSS_COMPILE=riscv64-linux-gnu-

# Or use the RISC-V toolchain from SiFive/riscv-collab:
# https://github.com/riscv-collab/riscv-gnu-toolchain

Using Yocto/OE SDK Toolchain

If you are using a Yocto-built toolchain:

source /opt/poky/5.0/environment-setup-aarch64-poky-linux
# CROSS_COMPILE is set automatically by the SDK environment

Setting CROSS_COMPILE Persistently

# Add to ~/.bashrc or use a wrapper script
export ARCH=arm64
export CROSS_COMPILE=aarch64-none-linux-gnu-

# U-Boot respects both ARCH and CROSS_COMPILE

---

First Build: QEMU ARM64 (Quick Verification)

This is the easiest way to verify your build environment is correct:

cd u-boot

# Set cross-compiler
export CROSS_COMPILE=aarch64-none-linux-gnu-

# Load qemu_arm64 defconfig
make qemu_arm64_defconfig

# Build (use all CPU cores)
make -j$(nproc)

# Verify output
ls -lh u-boot.bin u-boot

Expected output files:

u-boot           - ELF file (with debug symbols)
u-boot.bin       - Raw binary
u-boot-dtb.bin   - Binary with device tree appended
u-boot.map       - Symbol map
System.map       - Simplified symbol map

Testing with QEMU

sudo apt-get install qemu-system-arm

qemu-system-aarch64 \
    -machine virt \
    -cpu cortex-a57 \
    -nographic \
    -bios u-boot.bin

# Expected: U-Boot prompt "=>"

---

Build System Overview

U-Boot uses a GNU Make + Kconfig build system similar to the Linux kernel.

Build Flow

make <board>_defconfig     → .config
make menuconfig            → Interactive Kconfig editor
make -j$(nproc)            → Build all targets
make <specific_target>     → Build individual artifact

Important Make Targets

# Configuration
make <board>_defconfig     # Load board's default config
make menuconfig            # ncurses-based configuration editor
make nconfig               # Alternative ncurses UI
make xconfig               # Qt-based GUI (requires Qt)
make gconfig               # GTK-based GUI
make oldconfig             # Update .config from older defconfig
make savedefconfig         # Save minimal defconfig from .config
make defconfig             # Use default for current ARCH

# Building
make -j$(nproc)            # Build everything
make u-boot.bin            # Build just u-boot.bin
make spl/u-boot-spl.bin    # Build just SPL
make tpl/u-boot-tpl.bin    # Build just TPL
make u-boot.itb            # Build FIT image
make flash.bin             # Platform-specific combined image

# Cleaning
make clean                 # Remove build artifacts (keep .config)
make mrproper              # Remove everything including .config
make distclean             # Like mrproper + remove backups

# Information
make CROSS_COMPILE=... V=1 # Verbose build
make boards                # List all supported boards
make help                  # Show all available targets
make env                   # Show build environment variables

# Testing
make check                 # Run unit tests (sandbox)
make tcheck                # Parallel testing

Out-of-Tree Builds

You can build into a separate directory to keep the source clean:

mkdir /tmp/uboot-build
make O=/tmp/uboot-build qemu_arm64_defconfig
make O=/tmp/uboot-build -j$(nproc)

# All artifacts end up in /tmp/uboot-build/

Environment Variables Reference

Variable	Default	Description
ARCH	(from defconfig)	Target architecture: arm, arm64, riscv, x86
CROSS_COMPILE	(empty for native)	Toolchain prefix: aarch64-none-linux-gnu-
V	0	Verbose: V=1 shows full commands
O	.	Output directory for out-of-tree build
DTB	(from defconfig)	Override device tree blob filename
EXT_DTB	(empty)	Path to an external pre-compiled DTB
KBUILD_OUTPUT	(same as O)	Alternative to O
CONFIG_	—	Individual Kconfig overrides (not recommended)
BL31	(empty)	Path to ARM Trusted Firmware BL31 binary
TEE	(empty)	Path to OP-TEE binary for embedding
LOADADDR	(from config)	Override load address

---

Python Dependencies for Tools

Several tools (patman, binman, buildman) require Python 3.8+:

# Install Python dependencies
pip3 install --user \
    asteval \
    cbor2 \
    filelock \
    pycryptodome \
    pyelftools \
    pytest \
    tabulate \
    fdt

# Or using requirements file (if present in tools/patman/)
pip3 install -r tools/patman/requirements.txt

---

Using buildman for Multi-Board Builds

buildman is U-Boot's own multi-board build tool, useful for CI and testing patches across many boards:

# Build a single board
tools/buildman/buildman.py -o /tmp/build rpi_4

# Build all ARM64 boards
tools/buildman/buildman.py -o /tmp/build -a arm64

# Test a patch series for regressions
tools/buildman/buildman.py -o /tmp/build rpi_4 -P

# Show build errors only  
tools/buildman/buildman.py -o /tmp/build -a arm64 -sE

# Use custom toolchain
tools/buildman/buildman.py -o /tmp/build rpi_4 \
    --toolchain /opt/toolchains/aarch64-none-linux-gnu-

Configure buildman in ~/.buildman:

[toolchain]
# Add toolchain paths
root = /opt/linaro/

[toolchain-alias]
arm = arm-linux-gnueabihf-
aarch64 = aarch64-none-linux-gnu-
riscv64 = riscv64-linux-gnu-

Contributors: Vasu Grover

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