Setup Buildroot

  1. Download the source
    git clone git://git.buildroot.net/buildroot buildroot.git
    cd buildroot.git
    
  2. Configure the buildroot for aarch64 and make menuconfig; make

For X86-64, change the following options, Target Options -> Target Architecture(X86_64)
Filesystem images -> cpio the root filesystem (for use as an initial RAM filesystem)

For AArch64, similar to X86
Target Options -> Target Architecture(AArch64 (little endian))
Toolchain -> Toolchain type (External toolchain)
Toolchain -> Toolchain (Linaro AArch64 2016.11)
System configuration -> Run a getty after boot -> TTY port console
Filesystem images -> cpio the root filesystem (for use as an initial RAM filesystem)

The output cpio will be in output/images/rootfs.cpio

Setup QEMU

For X86/X86_64, sudo apt-get install qemu-system-x86
For AArch64, need to build qemu-system-aarch64 locally.

  1. Download qemu git, check out the branch and check out the latest branch
    git clone git://git.qemu.org/qemu.git qemu.git
    git branch -a
    git checkout -b stable-2.6 origin/stable-2.6
    
  2. Install the build dependency and compile qemu for aarch64
    sudo apt-get build-dep qemu
    
  3. Start compile
    ./configure --target-list=aarch64-softmmu
    make -j4
    

    The compilation should be done in several minutes. The generated file should be aarch64-softmmu/qemu-system-aarch64

Compile Linux Kernel

Using GCC

# For X86_64
make defconfig
make -j16 2>&1 | tee build.log

# For AArch64
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j16 2>&1 | tee build.log

Using LLVM/Clang

# For X86_64
make CC=clang defconfig
make CC=clang -j16 2>&1 | tee build.log

# For AArch64
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- HOSTCC=clang CC=clang defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
	HOSTCC=clang CC=clang -j16 2>&1 | tee build.log

Run Kernel on QEMU

# For X86_64
qemu-system-x86_64 \
-nographic -smp 8 -m 2048 \
-kernel $KERNEL_DIR/arch/x86/boot/bzImage \
-initrd $ROOTFS_DIR/output/images/rootfs.cpio \
-append "console=ttyS0" 

# For AArch64
$QEMU_DIR/aarch64-softmmu/qemu-system-aarch64 \
-machine virt -cpu cortex-a57 \
-nographic -smp 8 -m 2048 \
-kernel $KERNEL_DIR/arch/arm64/boot/Image \
-initrd $ROOTFS_DIR/output/images/rootfs.cpio \
-append "console=ttyAMA0"