Build 64-bit kernel for Raspberry Pi 3, using native tools
Raspberry Pi 3 64-bit kernel using native tools
The SoC on the Raspberry Pi 3 supports 64-bit mode, unfortunately raspbian and the foundation does not provide 64-bit support (yet?) even if they are advertising the Pi 3 as a 64-bit platform.
There are 3 ways to get a 64-bit kernel compiled:
- Native build on another 64-bit ARM platform
- Cross-compilation on another platform
- Cross-compilation on the Pi 3 itself
This tutorial will explain how to do option number 3. (And will actually work just fine for option number 2 as they are pretty much the same)
As we need to build the tools we need, that is aarch64 binutils and gcc, we need to install the required build tools first. So start by first installing required dependencies:
sudo apt-get install build-essential libgmp-dev libmpfr-dev libmpc-dev bc git-core
Build the cross compilation tools
Download the latest binutils, (2.28.1 at time of writing)
Untar the binutils archive
tar xf binutils-2.28.1.tar.bz2
Configure build and install
cd binutils-2.28.1 ./configure --prefix=/opt/aarch64 --target=aarch64-linux-gnu make -j4 sudo make install
Binutils is now installed, to be able to use it add "/opt/aarch64/bin/" to your path:
Next up is gcc, the C compiler. We will build a minimal compiler for C only and no userland support. This is enough to get a aarch64 kernel compiled.
Download latest gcc (6.3.0 at time of writing):
Untar the gcc archive
tar xf gcc-6.3.0.tar.bz2
Configure gcc and build gcc
mkdir gcc-out cd gcc-out ../gcc-6.3.0/configure --prefix=/opt/aarch64 --target=aarch64-linux-gnu --with-newlib --without-headers --disable-shared --enable-languages=c make all-gcc -j4 sudo make install-gcc
Now you have a toolchain that is able to build 64-bit ARM kenrels. So the next step is to download the Raspberry Pi kernel
sources, configure them and build a kernel and modules.
Download Linux kernel sources
Get the most up to date kernel sources (4.9 branch at time of writing) directly from git with
git clone --depth=1 -b rpi-4.9.y https://github.com/raspberrypi/linux.git
Configure Linux kernel for 64-bit Raspberry Pi 3
We use output directory for kernel build so we can use the same source tree for other configuration (32-bit for example)
mkdir kernel-out cd linux make O=../kernel-out/ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcmrpi3_defconfig
The kernel is now configured with a default configuration for a 64-bit Raspberry Pi kernel. In case you need to customize the
configuration (Add support for some specific hardware, etc) run
make O=../kernel-out/ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig
and adjust the configuration for your needs.
Build the kernel and modules
Next build the kernel and modules with:
make -j4 O=../kernel-out/ ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu-
If all goes well, as it should, you should now have a 64-bit kernel, modules and device tree built.