1.. SPDX-License-Identifier: GPL-2.0 2 3Quick Start 4=========== 5 6This document describes how to get started with kernel development in Rust. 7 8 9Requirements: Building 10---------------------- 11 12This section explains how to fetch the tools needed for building. 13 14Some of these requirements might be available from Linux distributions 15under names like ``rustc``, ``rust-src``, ``rust-bindgen``, etc. However, 16at the time of writing, they are likely not to be recent enough unless 17the distribution tracks the latest releases. 18 19To easily check whether the requirements are met, the following target 20can be used:: 21 22 make LLVM=1 rustavailable 23 24This triggers the same logic used by Kconfig to determine whether 25``RUST_IS_AVAILABLE`` should be enabled; but it also explains why not 26if that is the case. 27 28 29rustc 30***** 31 32A particular version of the Rust compiler is required. Newer versions may or 33may not work because, for the moment, the kernel depends on some unstable 34Rust features. 35 36If ``rustup`` is being used, enter the checked out source code directory 37and run:: 38 39 rustup override set $(scripts/min-tool-version.sh rustc) 40 41Otherwise, fetch a standalone installer from: 42 43 https://forge.rust-lang.org/infra/other-installation-methods.html#standalone 44 45 46Rust standard library source 47**************************** 48 49The Rust standard library source is required because the build system will 50cross-compile ``core`` and ``alloc``. 51 52If ``rustup`` is being used, run:: 53 54 rustup component add rust-src 55 56The components are installed per toolchain, thus upgrading the Rust compiler 57version later on requires re-adding the component. 58 59Otherwise, if a standalone installer is used, the Rust repository may be cloned 60into the installation folder of the toolchain:: 61 62 git clone --recurse-submodules \ 63 --branch $(scripts/min-tool-version.sh rustc) \ 64 https://github.com/rust-lang/rust \ 65 $(rustc --print sysroot)/lib/rustlib/src/rust 66 67In this case, upgrading the Rust compiler version later on requires manually 68updating this clone. 69 70 71libclang 72******** 73 74``libclang`` (part of LLVM) is used by ``bindgen`` to understand the C code 75in the kernel, which means LLVM needs to be installed; like when the kernel 76is compiled with ``CC=clang`` or ``LLVM=1``. 77 78Linux distributions are likely to have a suitable one available, so it is 79best to check that first. 80 81There are also some binaries for several systems and architectures uploaded at: 82 83 https://releases.llvm.org/download.html 84 85Otherwise, building LLVM takes quite a while, but it is not a complex process: 86 87 https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm 88 89Please see Documentation/kbuild/llvm.rst for more information and further ways 90to fetch pre-built releases and distribution packages. 91 92 93bindgen 94******* 95 96The bindings to the C side of the kernel are generated at build time using 97the ``bindgen`` tool. A particular version is required. 98 99Install it via (note that this will download and build the tool from source):: 100 101 cargo install --locked --version $(scripts/min-tool-version.sh bindgen) bindgen 102 103 104Requirements: Developing 105------------------------ 106 107This section explains how to fetch the tools needed for developing. That is, 108they are not needed when just building the kernel. 109 110 111rustfmt 112******* 113 114The ``rustfmt`` tool is used to automatically format all the Rust kernel code, 115including the generated C bindings (for details, please see 116coding-guidelines.rst). 117 118If ``rustup`` is being used, its ``default`` profile already installs the tool, 119thus nothing needs to be done. If another profile is being used, the component 120can be installed manually:: 121 122 rustup component add rustfmt 123 124The standalone installers also come with ``rustfmt``. 125 126 127clippy 128****** 129 130``clippy`` is a Rust linter. Running it provides extra warnings for Rust code. 131It can be run by passing ``CLIPPY=1`` to ``make`` (for details, please see 132general-information.rst). 133 134If ``rustup`` is being used, its ``default`` profile already installs the tool, 135thus nothing needs to be done. If another profile is being used, the component 136can be installed manually:: 137 138 rustup component add clippy 139 140The standalone installers also come with ``clippy``. 141 142 143cargo 144***** 145 146``cargo`` is the Rust native build system. It is currently required to run 147the tests since it is used to build a custom standard library that contains 148the facilities provided by the custom ``alloc`` in the kernel. The tests can 149be run using the ``rusttest`` Make target. 150 151If ``rustup`` is being used, all the profiles already install the tool, 152thus nothing needs to be done. 153 154The standalone installers also come with ``cargo``. 155 156 157rustdoc 158******* 159 160``rustdoc`` is the documentation tool for Rust. It generates pretty HTML 161documentation for Rust code (for details, please see 162general-information.rst). 163 164``rustdoc`` is also used to test the examples provided in documented Rust code 165(called doctests or documentation tests). The ``rusttest`` Make target uses 166this feature. 167 168If ``rustup`` is being used, all the profiles already install the tool, 169thus nothing needs to be done. 170 171The standalone installers also come with ``rustdoc``. 172 173 174rust-analyzer 175************* 176 177The `rust-analyzer <https://rust-analyzer.github.io/>`_ language server can 178be used with many editors to enable syntax highlighting, completion, go to 179definition, and other features. 180 181``rust-analyzer`` needs a configuration file, ``rust-project.json``, which 182can be generated by the ``rust-analyzer`` Make target. 183 184 185Configuration 186------------- 187 188``Rust support`` (``CONFIG_RUST``) needs to be enabled in the ``General setup`` 189menu. The option is only shown if a suitable Rust toolchain is found (see 190above), as long as the other requirements are met. In turn, this will make 191visible the rest of options that depend on Rust. 192 193Afterwards, go to:: 194 195 Kernel hacking 196 -> Sample kernel code 197 -> Rust samples 198 199And enable some sample modules either as built-in or as loadable. 200 201 202Building 203-------- 204 205Building a kernel with a complete LLVM toolchain is the best supported setup 206at the moment. That is:: 207 208 make LLVM=1 209 210For architectures that do not support a full LLVM toolchain, use:: 211 212 make CC=clang 213 214Using GCC also works for some configurations, but it is very experimental at 215the moment. 216 217 218Hacking 219------- 220 221To dive deeper, take a look at the source code of the samples 222at ``samples/rust/``, the Rust support code under ``rust/`` and 223the ``Rust hacking`` menu under ``Kernel hacking``. 224 225If GDB/Binutils is used and Rust symbols are not getting demangled, the reason 226is the toolchain does not support Rust's new v0 mangling scheme yet. 227There are a few ways out: 228 229 - Install a newer release (GDB >= 10.2, Binutils >= 2.36). 230 231 - Some versions of GDB (e.g. vanilla GDB 10.1) are able to use 232 the pre-demangled names embedded in the debug info (``CONFIG_DEBUG_INFO``). 233