Quick Start¶
This document describes how to get started with kernel development in Rust.
Requirements: Building¶
This section explains how to fetch the tools needed for building.
Some of these requirements might be available from Linux distributions
under names like rustc, rust-src, rust-bindgen, etc. However,
at the time of writing, they are likely not to be recent enough unless
the distribution tracks the latest releases.
To easily check whether the requirements are met, the following target can be used:
make LLVM=1 rustavailable
This triggers the same logic used by Kconfig to determine whether
RUST_IS_AVAILABLE should be enabled; but it also explains why not
if that is the case.
rustc¶
A particular version of the Rust compiler is required. Newer versions may or may not work because, for the moment, the kernel depends on some unstable Rust features.
If rustup is being used, enter the checked out source code directory
and run:
rustup override set $(scripts/min-tool-version.sh rustc)
This will configure your working directory to use the correct version of
rustc without affecting your default toolchain. If you are not using
rustup, fetch a standalone installer from:
Rust standard library source¶
The Rust standard library source is required because the build system will
cross-compile core and alloc.
If rustup is being used, run:
rustup component add rust-src
The components are installed per toolchain, thus upgrading the Rust compiler version later on requires re-adding the component.
Otherwise, if a standalone installer is used, the Rust source tree may be downloaded into the toolchain’s installation folder:
curl -L "https://static.rust-lang.org/dist/rust-src-$(scripts/min-tool-version.sh rustc).tar.gz" |
tar -xzf - -C "$(rustc --print sysroot)/lib" \
"rust-src-$(scripts/min-tool-version.sh rustc)/rust-src/lib/" \
--strip-components=3
In this case, upgrading the Rust compiler version later on requires manually
updating the source tree (this can be done by removing $(rustc --print
sysroot)/lib/rustlib/src/rust then rerunning the above command).
libclang¶
libclang (part of LLVM) is used by bindgen to understand the C code
in the kernel, which means LLVM needs to be installed; like when the kernel
is compiled with CC=clang or LLVM=1.
Linux distributions are likely to have a suitable one available, so it is best to check that first.
There are also some binaries for several systems and architectures uploaded at:
Otherwise, building LLVM takes quite a while, but it is not a complex process:
Please see Building Linux with Clang/LLVM for more information and further ways to fetch pre-built releases and distribution packages.
bindgen¶
The bindings to the C side of the kernel are generated at build time using
the bindgen tool. A particular version is required.
Install it via (note that this will download and build the tool from source):
cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen-cli
bindgen needs to find a suitable libclang in order to work. If it is
not found (or a different libclang than the one found should be used),
the process can be tweaked using the environment variables understood by
clang-sys (the Rust bindings crate that bindgen uses to access
libclang):
LLVM_CONFIG_PATHcan be pointed to anllvm-configexecutable.Or
LIBCLANG_PATHcan be pointed to alibclangshared library or to the directory containing it.Or
CLANG_PATHcan be pointed to aclangexecutable.
For details, please see clang-sys’s documentation at:
Requirements: Developing¶
This section explains how to fetch the tools needed for developing. That is, they are not needed when just building the kernel.
rustfmt¶
The rustfmt tool is used to automatically format all the Rust kernel code,
including the generated C bindings (for details, please see
Coding Guidelines).
If rustup is being used, its default profile already installs the tool,
thus nothing needs to be done. If another profile is being used, the component
can be installed manually:
rustup component add rustfmt
The standalone installers also come with rustfmt.
clippy¶
clippy is a Rust linter. Running it provides extra warnings for Rust code.
It can be run by passing CLIPPY=1 to make (for details, please see
General Information).
If rustup is being used, its default profile already installs the tool,
thus nothing needs to be done. If another profile is being used, the component
can be installed manually:
rustup component add clippy
The standalone installers also come with clippy.
cargo¶
cargo is the Rust native build system. It is currently required to run
the tests since it is used to build a custom standard library that contains
the facilities provided by the custom alloc in the kernel. The tests can
be run using the rusttest Make target.
If rustup is being used, all the profiles already install the tool,
thus nothing needs to be done.
The standalone installers also come with cargo.
rustdoc¶
rustdoc is the documentation tool for Rust. It generates pretty HTML
documentation for Rust code (for details, please see
General Information).
rustdoc is also used to test the examples provided in documented Rust code
(called doctests or documentation tests). The rusttest Make target uses
this feature.
If rustup is being used, all the profiles already install the tool,
thus nothing needs to be done.
The standalone installers also come with rustdoc.
rust-analyzer¶
The rust-analyzer language server can be used with many editors to enable syntax highlighting, completion, go to definition, and other features.
rust-analyzer needs a configuration file, rust-project.json, which
can be generated by the rust-analyzer Make target:
make LLVM=1 rust-analyzer
Configuration¶
Rust support (CONFIG_RUST) needs to be enabled in the General setup
menu. The option is only shown if a suitable Rust toolchain is found (see
above), as long as the other requirements are met. In turn, this will make
visible the rest of options that depend on Rust.
Afterwards, go to:
Kernel hacking
-> Sample kernel code
-> Rust samples
And enable some sample modules either as built-in or as loadable.
Building¶
Building a kernel with a complete LLVM toolchain is the best supported setup at the moment. That is:
make LLVM=1
For architectures that do not support a full LLVM toolchain, use:
make CC=clang
Using GCC also works for some configurations, but it is very experimental at the moment.
Hacking¶
To dive deeper, take a look at the source code of the samples
at samples/rust/, the Rust support code under rust/ and
the Rust hacking menu under Kernel hacking.
If GDB/Binutils is used and Rust symbols are not getting demangled, the reason is the toolchain does not support Rust’s new v0 mangling scheme yet. There are a few ways out:
Install a newer release (GDB >= 10.2, Binutils >= 2.36).
Some versions of GDB (e.g. vanilla GDB 10.1) are able to use the pre-demangled names embedded in the debug info (
CONFIG_DEBUG_INFO).