Cross compiling aarch64(arm64) rust for linux from x86_64 machine

In October 6, Rust for linux is under the linux-next, not stable
Thus this article would be out-of-date before Linux 6.1 stable comes.

Current linux 6.1 rc1 doesn’t contain rust for linux with ARM64. Thus this article play with https://github.com/Rust-for-Linux/linux/tree/for-next/rust

Introduction #

This article describes cross-compiling rust for linux on x86_64 debian. There is still not enough computing power to build arm64 native kernel except for Apple Silicon.

Btw, this article is in reference to these links

• https://github.com/Rust-for-Linux/linux/blob/rust/Documentation/rust/quick-start.rst
• https://docs.kernel.org/kbuild/llvm.html#cross-compiling

Debian / Ubuntu Package Requirements #

# Install build-requirements for kernel compile with LLVM.
# Biggest difference to native build is
# crossbuild-essential-arm64 needed to build` for arm64
apt install clang git llvm-dev libclang-dev build-essential \
bc kmod cpio flex libncurses5-dev libelf-dev libssl-dev \
dwarves bison lld curl crossbuild-essential-arm64

Before build kernel, we need to install some packages.

curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
rustup default 1.62
rustup component add rust-src
# rustfmt and clippy is need for later developing and debugging.
rustup component add rustfmt 
rustup component add clippy

Install rust with curl. You can select just default options. Also current rust for linux working with 1.62. Some native compile is working well with recent version (1.64 tested, but cross compile not working).

Arch Package Requirements #

• TBD

Clone linux from Rust-For-Linux #

# In my case use `Develop` as worksapce, you can replace this word. 
mkdir -p ~/Develop
cd ~/Develop
git clone https://github.com/Rust-for-Linux/linux.git -b rust

clone like this.

Necessary some rust scripts in Rust-For-Linux #

In cloned linux directory.

git clone --recurse-submodules \
        --branch $(scripts/min-tool-version.sh rustc) \
        https://github.com/rust-lang/rust \
        $(rustc --print sysroot)/lib/rustlib/src/rust

This work clone rustlib repository in your rust toolchain directory.

cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen

This work need to bind existing c code to rust code. s

Check RUST_AVAILABLE #

cd ~/Develop/linux
make LLVM=1 rustavailable

$ make LLVM=1 rustavailable
***
*** Rust compiler 'rustc' is too new. This may or may not work.
***   Your version:     1.62.1
***   Expected version: 1.62.0
***
Rust is available!

Than if you get result like this it’s good to go (1.62.1 was fine to cross compile, but if you consider best fit, run rustup default 1.62.0.)

Configure linux source code with menuconfig #

make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

General setup -> Rust support #

Kernel hacking -> Sample kernel code #

For easy to develop rust kernel code we need some examples. You can get them with following menus.

In Kernel hacking -> Sample kernel code , enable it (not all of them..) when you interest. I don’t recommend you enable them when you write own driver. Because there’s some possibility make system slow or make unwanted log in dmesg.
In particular, the netflitter example outputs too many dmesg, so it is recommended that you disable it unless you are studying the netfilter example.

Kernel hacking -> Rust hacking #

For debug rust kernel code or driver, need to enable some debug options.

In Kernel hacking -> Rust hacking , enables it and inside menus.

Cross compile #

# -j4 for 4 core virtual machine, -j2 for 2 core, -j1 for single core.
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- LLVM=1 -j32

Build with following command. You need to set number of job considering assigned number of cores for virtual machine. (-j#)

Also while you build it, it will ask some flag. I just select default in my case.

Simple compile speed comparation. #

Install cross compiled kernel to arm64 virtual machine #

• TBD, will update asap.

Install cross compiled kernel to raspberry pi #

• TBD, will update asap.