diff options
| -rw-r--r-- | Documentation/doc-guide/kernel-doc.rst | 3 | ||||
| -rw-r--r-- | Documentation/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/kbuild/kbuild.rst | 17 | ||||
| -rw-r--r-- | Documentation/kbuild/makefiles.rst | 50 | ||||
| -rw-r--r-- | Documentation/process/changes.rst | 41 | ||||
| -rw-r--r-- | Documentation/rust/arch-support.rst | 18 | ||||
| -rw-r--r-- | Documentation/rust/coding-guidelines.rst | 216 | ||||
| -rw-r--r-- | Documentation/rust/general-information.rst | 79 | ||||
| -rw-r--r-- | Documentation/rust/index.rst | 22 | ||||
| -rw-r--r-- | Documentation/rust/quick-start.rst | 232 |
10 files changed, 675 insertions, 4 deletions
diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst index 9c779bd7a751..1dcbd7332476 100644 --- a/Documentation/doc-guide/kernel-doc.rst +++ b/Documentation/doc-guide/kernel-doc.rst @@ -14,6 +14,9 @@ when it is embedded in source files. reasons. The kernel source contains tens of thousands of kernel-doc comments. Please stick to the style described here. +.. note:: kernel-doc does not cover Rust code: please see + Documentation/rust/general-information.rst instead. + The kernel-doc structure is extracted from the comments, and proper `Sphinx C Domain`_ function and type descriptions with anchors are generated from them. The descriptions are filtered for special kernel-doc diff --git a/Documentation/index.rst b/Documentation/index.rst index 4737c18c97ff..00722aa20cd7 100644 --- a/Documentation/index.rst +++ b/Documentation/index.rst @@ -82,6 +82,7 @@ merged much easier. maintainer/index fault-injection/index livepatch/index + rust/index Kernel API documentation diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst index ef19b9c13523..08f575e6236c 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -48,6 +48,10 @@ KCFLAGS ------- Additional options to the C compiler (for built-in and modules). +KRUSTFLAGS +---------- +Additional options to the Rust compiler (for built-in and modules). + CFLAGS_KERNEL ------------- Additional options for $(CC) when used to compile @@ -57,6 +61,15 @@ CFLAGS_MODULE ------------- Additional module specific options to use for $(CC). +RUSTFLAGS_KERNEL +---------------- +Additional options for $(RUSTC) when used to compile +code that is compiled as built-in. + +RUSTFLAGS_MODULE +---------------- +Additional module specific options to use for $(RUSTC). + LDFLAGS_MODULE -------------- Additional options used for $(LD) when linking modules. @@ -69,6 +82,10 @@ HOSTCXXFLAGS ------------ Additional flags to be passed to $(HOSTCXX) when building host programs. +HOSTRUSTFLAGS +------------- +Additional flags to be passed to $(HOSTRUSTC) when building host programs. + HOSTLDFLAGS ----------- Additional flags to be passed when linking host programs. diff --git a/Documentation/kbuild/makefiles.rst b/Documentation/kbuild/makefiles.rst index 11a296e52d68..5ea1e72d89c8 100644 --- a/Documentation/kbuild/makefiles.rst +++ b/Documentation/kbuild/makefiles.rst @@ -29,8 +29,9 @@ This document describes the Linux kernel Makefiles. --- 4.1 Simple Host Program --- 4.2 Composite Host Programs --- 4.3 Using C++ for host programs - --- 4.4 Controlling compiler options for host programs - --- 4.5 When host programs are actually built + --- 4.4 Using Rust for host programs + --- 4.5 Controlling compiler options for host programs + --- 4.6 When host programs are actually built === 5 Userspace Program support --- 5.1 Simple Userspace Program @@ -835,7 +836,24 @@ Both possibilities are described in the following. qconf-cxxobjs := qconf.o qconf-objs := check.o -4.4 Controlling compiler options for host programs +4.4 Using Rust for host programs +-------------------------------- + + Kbuild offers support for host programs written in Rust. However, + since a Rust toolchain is not mandatory for kernel compilation, + it may only be used in scenarios where Rust is required to be + available (e.g. when ``CONFIG_RUST`` is enabled). + + Example:: + + hostprogs := target + target-rust := y + + Kbuild will compile ``target`` using ``target.rs`` as the crate root, + located in the same directory as the ``Makefile``. The crate may + consist of several source files (see ``samples/rust/hostprogs``). + +4.5 Controlling compiler options for host programs -------------------------------------------------- When compiling host programs, it is possible to set specific flags. @@ -867,7 +885,7 @@ Both possibilities are described in the following. When linking qconf, it will be passed the extra option "-L$(QTDIR)/lib". -4.5 When host programs are actually built +4.6 When host programs are actually built ----------------------------------------- Kbuild will only build host-programs when they are referenced @@ -1181,6 +1199,17 @@ When kbuild executes, the following steps are followed (roughly): The first example utilises the trick that a config option expands to 'y' when selected. + KBUILD_RUSTFLAGS + $(RUSTC) compiler flags + + Default value - see top level Makefile + Append or modify as required per architecture. + + Often, the KBUILD_RUSTFLAGS variable depends on the configuration. + + Note that target specification file generation (for ``--target``) + is handled in ``scripts/generate_rust_target.rs``. + KBUILD_AFLAGS_KERNEL Assembler options specific for built-in @@ -1208,6 +1237,19 @@ When kbuild executes, the following steps are followed (roughly): are used for $(CC). From commandline CFLAGS_MODULE shall be used (see kbuild.rst). + KBUILD_RUSTFLAGS_KERNEL + $(RUSTC) options specific for built-in + + $(KBUILD_RUSTFLAGS_KERNEL) contains extra Rust compiler flags used to + compile resident kernel code. + + KBUILD_RUSTFLAGS_MODULE + Options for $(RUSTC) when building modules + + $(KBUILD_RUSTFLAGS_MODULE) is used to add arch-specific options that + are used for $(RUSTC). + From commandline RUSTFLAGS_MODULE shall be used (see kbuild.rst). + KBUILD_LDFLAGS_MODULE Options for $(LD) when linking modules diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst index 19c286c23786..9a90197989dd 100644 --- a/Documentation/process/changes.rst +++ b/Documentation/process/changes.rst @@ -31,6 +31,8 @@ you probably needn't concern yourself with pcmciautils. ====================== =============== ======================================== GNU C 5.1 gcc --version Clang/LLVM (optional) 11.0.0 clang --version +Rust (optional) 1.62.0 rustc --version +bindgen (optional) 0.56.0 bindgen --version GNU make 3.81 make --version bash 4.2 bash --version binutils 2.23 ld -v @@ -80,6 +82,29 @@ kernels. Older releases aren't guaranteed to work, and we may drop workarounds from the kernel that were used to support older versions. Please see additional docs on :ref:`Building Linux with Clang/LLVM <kbuild_llvm>`. +Rust (optional) +--------------- + +A particular version of the Rust toolchain is required. Newer versions may or +may not work because the kernel depends on some unstable Rust features, for +the moment. + +Each Rust toolchain comes with several "components", some of which are required +(like ``rustc``) and some that are optional. The ``rust-src`` component (which +is optional) needs to be installed to build the kernel. Other components are +useful for developing. + +Please see Documentation/rust/quick-start.rst for instructions on how to +satisfy the build requirements of Rust support. In particular, the ``Makefile`` +target ``rustavailable`` is useful to check why the Rust toolchain may not +be detected. + +bindgen (optional) +------------------ + +``bindgen`` is used to generate the Rust bindings to the C side of the kernel. +It depends on ``libclang``. + Make ---- @@ -348,6 +373,12 @@ Sphinx Please see :ref:`sphinx_install` in :ref:`Documentation/doc-guide/sphinx.rst <sphinxdoc>` for details about Sphinx requirements. +rustdoc +------- + +``rustdoc`` is used to generate the documentation for Rust code. Please see +Documentation/rust/general-information.rst for more information. + Getting updated software ======================== @@ -364,6 +395,16 @@ Clang/LLVM - :ref:`Getting LLVM <getting_llvm>`. +Rust +---- + +- Documentation/rust/quick-start.rst. + +bindgen +------- + +- Documentation/rust/quick-start.rst. + Make ---- diff --git a/Documentation/rust/arch-support.rst b/Documentation/rust/arch-support.rst new file mode 100644 index 000000000000..1152e0fbdad0 --- /dev/null +++ b/Documentation/rust/arch-support.rst @@ -0,0 +1,18 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Arch Support +============ + +Currently, the Rust compiler (``rustc``) uses LLVM for code generation, +which limits the supported architectures that can be targeted. In addition, +support for building the kernel with LLVM/Clang varies (please see +Documentation/kbuild/llvm.rst). This support is needed for ``bindgen`` +which uses ``libclang``. + +Below is a general summary of architectures that currently work. Level of +support corresponds to ``S`` values in the ``MAINTAINERS`` file. + +============ ================ ============================================== +Architecture Level of support Constraints +============ ================ ============================================== +============ ================ ============================================== diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst new file mode 100644 index 000000000000..aa8ed082613e --- /dev/null +++ b/Documentation/rust/coding-guidelines.rst @@ -0,0 +1,216 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Coding Guidelines +================= + +This document describes how to write Rust code in the kernel. + + +Style & formatting +------------------ + +The code should be formatted using ``rustfmt``. In this way, a person +contributing from time to time to the kernel does not need to learn and +remember one more style guide. More importantly, reviewers and maintainers +do not need to spend time pointing out style issues anymore, and thus +less patch roundtrips may be needed to land a change. + +.. note:: Conventions on comments and documentation are not checked by + ``rustfmt``. Thus those are still needed to be taken care of. + +The default settings of ``rustfmt`` are used. This means the idiomatic Rust +style is followed. For instance, 4 spaces are used for indentation rather +than tabs. + +It is convenient to instruct editors/IDEs to format while typing, +when saving or at commit time. However, if for some reason reformatting +the entire kernel Rust sources is needed at some point, the following can be +run:: + + make LLVM=1 rustfmt + +It is also possible to check if everything is formatted (printing a diff +otherwise), for instance for a CI, with:: + + make LLVM=1 rustfmtcheck + +Like ``clang-format`` for the rest of the kernel, ``rustfmt`` works on +individual files, and does not require a kernel configuration. Sometimes it may +even work with broken code. + + +Comments +-------- + +"Normal" comments (i.e. ``//``, rather than code documentation which starts +with ``///`` or ``//!``) are written in Markdown the same way as documentation +comments are, even though they will not be rendered. This improves consistency, +simplifies the rules and allows to move content between the two kinds of +comments more easily. For instance: + +.. code-block:: rust + + // `object` is ready to be handled now. + f(object); + +Furthermore, just like documentation, comments are capitalized at the beginning +of a sentence and ended with a period (even if it is a single sentence). This +includes ``// SAFETY:``, ``// TODO:`` and other "tagged" comments, e.g.: + +.. code-block:: rust + + // FIXME: The error should be handled properly. + +Comments should not be used for documentation purposes: comments are intended +for implementation details, not users. This distinction is useful even if the +reader of the source file is both an implementor and a user of an API. In fact, +sometimes it is useful to use both comments and documentation at the same time. +For instance, for a ``TODO`` list or to comment on the documentation itself. +For the latter case, comments can be inserted in the middle; that is, closer to +the line of documentation to be commented. For any other case, comments are +written after the documentation, e.g.: + +.. code-block:: rust + + /// Returns a new [`Foo`]. + /// + /// # Examples + /// + // TODO: Find a better example. + /// ``` + /// let foo = f(42); + /// ``` + // FIXME: Use fallible approach. + pub fn f(x: i32) -> Foo { + // ... + } + +One special kind of comments are the ``// SAFETY:`` comments. These must appear +before every ``unsafe`` block, and they explain why the code inside the block is +correct/sound, i.e. why it cannot trigger undefined behavior in any case, e.g.: + +.. code-block:: rust + + // SAFETY: `p` is valid by the safety requirements. + unsafe { *p = 0; } + +``// SAFETY:`` comments are not to be confused with the ``# Safety`` sections +in code documentation. ``# Safety`` sections specify the contract that callers +(for functions) or implementors (for traits) need to abide by. ``// SAFETY:`` +comments show why a call (for functions) or implementation (for traits) actually +respects the preconditions stated in a ``# Safety`` section or the language +reference. + + +Code documentation +------------------ + +Rust kernel code is not documented like C kernel code (i.e. via kernel-doc). +Instead, the usual system for documenting Rust code is used: the ``rustdoc`` +tool, which uses Markdown (a lightweight markup language). + +To learn Markdown, there are many guides available out there. For instance, +the one at: + + https://commonmark.org/help/ + +This is how a well-documented Rust function may look like: + +.. code-block:: rust + + /// Returns the contained [`Some`] value, consuming the `self` value, + /// without checking that the value is not [`None`]. + /// + /// # Safety + /// + /// Calling this method on [`None`] is *[undefined behavior]*. + /// + /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html + /// + /// # Examples + /// + /// ``` + /// let x = Some("air"); + /// assert_eq!(unsafe { x.unwrap_unchecked() }, "air"); + /// ``` + pub unsafe fn unwrap_unchecked(self) -> T { + match self { + Some(val) => val, + + // SAFETY: The safety contract must be upheld by the caller. + None => unsafe { hint::unreachable_unchecked() }, + } + } + +This example showcases a few ``rustdoc`` features and some conventions followed +in the kernel: + + - The first paragraph must be a single sentence briefly describing what + the documented item does. Further explanations must go in extra paragraphs. + + - Unsafe functions must document their safety preconditions under + a ``# Safety`` section. + + - While not shown here, if a function may panic, the conditions under which + that happens must be described under a ``# Panics`` section. + + Please note that panicking should be very rare and used only with a good + reason. In almost all cases, a fallible approach should be used, typically + returning a ``Result``. + + - If providing examples of usage would help readers, they must be written in + a section called ``# Examples``. + + - Rust items (functions, types, constants...) must be linked appropriately + (``rustdoc`` will create a link automatically). + + - Any ``unsafe`` block must be preceded by a ``// SAFETY:`` comment + describing why the code inside is sound. + + While sometimes the reason might look trivial and therefore unneeded, + writing these comments is not just a good way of documenting what has been + taken into account, but most importantly, it provides a way to know that + there are no *extra* implicit constraints. + +To learn more about how to write documentation for Rust and extra features, +please take a look at the ``rustdoc`` book at: + + https://doc.rust-lang.org/rustdoc/how-to-write-documentation.html + + +Naming +------ + +Rust kernel code follows the usual Rust naming conventions: + + https://rust-lang.github.io/api-guidelines/naming.html + +When existing C concepts (e.g. macros, functions, objects...) are wrapped into +a Rust abstraction, a name as close as reasonably possible to the C side should +be used in order to avoid confusion and to improve readability when switching +back and forth between the C and Rust sides. For instance, macros such as +``pr_info`` from C are named the same in the Rust side. + +Having said that, casing should be adjusted to follow the Rust naming +conventions, and namespacing introduced by modules and types should not be +repeated in the item names. For instance, when wrapping constants like: + +.. code-block:: c + + #define GPIO_LINE_DIRECTION_IN 0 + #define GPIO_LINE_DIRECTION_OUT 1 + +The equivalent in Rust may look like (ignoring documentation): + +.. code-block:: rust + + pub mod gpio { + pub enum LineDirection { + In = bindings::GPIO_LINE_DIRECTION_IN as _, + Out = bindings::GPIO_LINE_DIRECTION_OUT as _, + } + } + +That is, the equivalent of ``GPIO_LINE_DIRECTION_IN`` would be referred to as +``gpio::LineDirection::In``. In particular, it should not be named +``gpio::gpio_line_direction::GPIO_LINE_DIRECTION_IN``. diff --git a/Documentation/rust/general-information.rst b/Documentation/rust/general-information.rst new file mode 100644 index 000000000000..49029ee82e55 --- /dev/null +++ b/Documentation/rust/general-information.rst @@ -0,0 +1,79 @@ +.. SPDX-License-Identifier: GPL-2.0 + +General Information +=================== + +This document contains useful information to know when working with +the Rust support in the kernel. + + +Code documentation +------------------ + +Rust kernel code is documented using ``rustdoc``, its built-in documentation +generator. + +The generated HTML docs include integrated search, linked items (e.g. types, +functions, constants), source code, etc. They may be read at (TODO: link when +in mainline and generated alongside the rest of the documentation): + + http://kernel.org/ + +The docs can also be easily generated and read locally. This is quite fast +(same order as compiling the code itself) and no special tools or environment +are needed. This has the added advantage that they will be tailored to +the particular kernel configuration used. To generate them, use the ``rustdoc`` +target with the same invocation used for compilation, e.g.:: + + make LLVM=1 rustdoc + +To read the docs locally in your web browser, run e.g.:: + + xdg-open rust/doc/kernel/index.html + +To learn about how to write the documentation, please see coding-guidelines.rst. + + +Extra lints +----------- + +While ``rustc`` is a very helpful compiler, some extra lints and analyses are +available via ``clippy``, a Rust linter. To enable it, pass ``CLIPPY=1`` to +the same invocation used for compilation, e.g.:: + + make LLVM=1 CLIPPY=1 + +Please note that Clippy may change code generation, thus it should not be +enabled while building a production kernel. + + +Abstractions vs. bindings +------------------------- + +Abstractions are Rust code wrapping kernel functionality from the C side. + +In order to use functions and types from the C side, bindings are created. +Bindings are the declarations for Rust of those functions and types from +the C side. + +For instance, one may write a ``Mutex`` abstraction in Rust which wraps +a ``struct mutex`` from the C side and calls its functions through the bindings. + +Abstractions are not available for all the kernel internal APIs and concepts, +but it is intended that coverage is expanded as time goes on. "Leaf" modules +(e.g. drivers) should not use the C bindings directly. Instead, subsystems +should provide as-safe-as-possible abstractions as needed. + + +Conditional compilation +----------------------- + +Rust code has access to conditional compilation based on the kernel +configuration: + +.. code-block:: rust + + #[cfg(CONFIG_X)] // Enabled (`y` or `m`) + #[cfg(CONFIG_X="y")] // Enabled as a built-in (`y`) + #[cfg(CONFIG_X="m")] // Enabled as a module (`m`) + #[cfg(not(CONFIG_X))] // Disabled diff --git a/Documentation/rust/index.rst b/Documentation/rust/index.rst new file mode 100644 index 000000000000..4ae8c66b94fa --- /dev/null +++ b/Documentation/rust/index.rst @@ -0,0 +1,22 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Rust +==== + +Documentation related to Rust within the kernel. To start using Rust +in the kernel, please read the quick-start.rst guide. + +.. toctree:: + :maxdepth: 1 + + quick-start + general-information + coding-guidelines + arch-support + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst new file mode 100644 index 000000000000..13b7744b1e27 --- /dev/null +++ b/Documentation/rust/quick-start.rst @@ -0,0 +1,232 @@ +.. SPDX-License-Identifier: GPL-2.0 + +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) + +Otherwise, fetch a standalone installer or install ``rustup`` from: + + https://www.rust-lang.org + + +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 repository may be cloned +into the installation folder of the toolchain:: + + git clone --recurse-submodules \ + --branch $(scripts/min-tool-version.sh rustc) \ + https://github.com/rust-lang/rust \ + $(rustc --print sysroot)/lib/rustlib/src/rust + +In this case, upgrading the Rust compiler version later on requires manually +updating this clone. + + +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: + + https://releases.llvm.org/download.html + +Otherwise, building LLVM takes quite a while, but it is not a complex process: + + https://llvm.org/docs/GettingStarted.html#getting-the-source-code-and-building-llvm + +Please see Documentation/kbuild/llvm.rst 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 + + +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.rst). + +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.rst). + +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.rst). + +``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 <https://rust-analyzer.github.io/>`_ 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. + + +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``). |