[PATCH v8 00/31] Rust support

[PATCH v8 00/31] Rust support

[Miguel Ojeda]

Rust support

This is the patch series (v8) to add support for Rust as a second
language to the Linux kernel.

If you are interested in following this effort, please join us in
the mailing list at:

    rust-for-linux@vger.kernel.org

and take a look at the project itself at:

    https://github.com/Rust-for-Linux

As usual, special thanks go to ISRG (Internet Security Research
Group) and Google for their financial support on this endeavor.

Cheers,
Miguel

--

# Rust support

This cover letter explains the major changes and updates done since
the previous ones. For those, please see:

    RFC: https://lore.kernel.org/lkml/20210414184604.23473-1-ojeda@kernel.org/
    v1:  https://lore.kernel.org/lkml/20210704202756.29107-1-ojeda@kernel.org/
    v2:  https://lore.kernel.org/lkml/20211206140313.5653-1-ojeda@kernel.org/
    v3:  https://lore.kernel.org/lkml/20220117053349.6804-1-ojeda@kernel.org/
    v4:  https://lore.kernel.org/lkml/20220212130410.6901-1-ojeda@kernel.org/
    v5:  https://lore.kernel.org/lkml/20220317181032.15436-1-ojeda@kernel.org/
    v6:  https://lore.kernel.org/lkml/20220507052451.12890-1-ojeda@kernel.org/
    v7:  https://lore.kernel.org/lkml/20220523020209.11810-1-ojeda@kernel.org/


## Infrastructure updates

There have been several improvements to the overall Rust support:

  - Upgraded toolchain and `alloc` to Rust 1.62.0 from 1.60.0.
    Rust 1.61.0 stabilized `feature(const_fn_trait_bound)` that
    we are using.

  - Moved bindings into their own crate, `bindings`. This greatly
    improves build time when only the `kernel` crate changes (which
    previously contained the bindings).

  - Disabled unused `bindgen`'s layout test generation, which makes
    rust-analyzer significantly faster to run.

  - `bindgen` can now be detected via the `__BINDGEN__` macro, which
    we currently use to workaround an issue with the `btf_type_tag`
    attribute.

  - Reimplemented `concat_idents!` (an unstable standard library
    macro) as a proc macro, which means we no longer rely on
    `feature(concat_idents)`. Furthermore, the proc macro allows
    to refer to local variables.

  - Reimplemented `static_assert!` in a more idiomatic way, now that
    `core::assert!()` is supported in const contexts.

  - Made `build_error!`' work under `RUST_BUILD_ASSERT_{WARN,ALLOW}`
    for modules.

  - Removed `__mulodi4` panicking stub.

  - Added `kernel/configs/rust.config`.

  - Added a (temporary) self-test module for "pure" Rust tests.

  - Changed `.i` macro expanded files to the `.rsi` extension and
    clarified that they are not intended to be compilable.

  - Dropped support for compiling the Rust side with a different
    optimization level than the C side.

  - The Linux/Tux SVG logo (recently upstreamed) is used for
    the generated Rust documentation, instead of the GIF one.
    The `COPYING-logo` file is bundled too.

  - Other cleanups, fixes and improvements.


## Abstractions and driver updates

Some of the improvements to the abstractions and example drivers are:

  - Filesystem support (`fs` module), including:

      + `INode` type (which wraps `struct inode`).
      + `DEntry` type (which wraps `struct dentry`).
      + `Filename` type (which wraps `struct filename`).
      + `Registration` type.
      + `Type` and `Context` traits.
      + `SuperBlock` type (which wraps `struct super_block` and takes
        advantage of typestates for its initialization).
      + File system parameters support (with a `Value` enum; `Spec*`
        and `Constant*` types, `define_fs_params!` macro...).
      + File system flags.
      + `module_fs!` macro to simplify registering kernel modules that
        only implement a single file system.
      + A file system sample.

  - Workqueues support (`workqueue` module), including a `Work` type
    (which wraps `struct work_struct`), a `Queue` type (which wraps
    `struct workqueue_struct`), access to different system queues as
    well as macros to simplify usage, e.g.:

        spawn_work_item!(workqueue::system(), || pr_info!("Hi!\n"))?;

  - More asynchronous support (`kasync` module), including:

      + Executor support (including `Task` and `Executor` traits, a
        `AutoStopHandle` type that automatically stops the executor on
        drop, a `spawn_task!` macro that automatically defines a new
        lockdep lock class...).

      + A workqueue-based executor, which allows to run tasks on
        dedicated or shared thread pools that are managed by existing
        C kernel infrastructure, e.g.:

            let mut handle = Executor::try_new(workqueue::system())?;

            spawn_task!(handle.executor(), async {
                pr_info!("First workqueue task\n");
            })?;

            spawn_task!(handle.executor(), async {
                pr_info!("Second workqueue task\n");
            })?;

            handle.detach();

      + A `yield_now()` function that yields execution of the current
        task so that other ones may execute (but keeps it runnable so
        that it will run again as soon as the executor is available
        again), e.g.:

            async fn example() {
                pr_info!("Before yield\n");
                yield_now().await;
                pr_info!("After yield\n");
            }

      + `AsyncRevocable` type (in the `revocable` module), which
        allows access to objects to be revoked without having to wait
        for existing users to complete. This is useful to drop futures
        in tasks when executors are being torn down.

      + An asynchronous TCP echo server sample.

  - Introduced support for handling interrupts: `[Threaded]Handler`
    traits, `[Threaded]Registration` types, a `Return` enum (as the
    return value from handlers) and flags:

        struct Example;

        impl irq::Handler for Example {
            type Data = Box<u32>;

            fn handle_irq(_data: &u32) -> irq::Return {
                irq::Return::None
            }
        }

        fn request_irq(irq: u32, data: Box<u32>)
          -> Result<irq::Registration<Example>> {
            irq::Registration::try_new(
                irq, data, irq::flags::SHARED,
                fmt!("example_{irq}")
            )
        }

  - Introduced the `#[vtable]` proc macro attribute to simplify how
    function pointer tables like `struct file_operations` are used
    by Rust kernel modules.

    Previously, users had to call a `declare_*_operations!` macro
    which required passing the defined operations:

        impl file::Operations for SomeFile {
            ...
            declare_file_operations!(read, write, ioctl, ...);
            ...
        }

    Instead, now it is only required that they annotate the `impl`
    block with the attribute:

        #[vtable]
        impl file::Operations for SomeFile {
            ...
        }

    The proc macro will generate a boolean `HAS_*` associated constant
    for each method in the trait, indicating if the implementer has
    overridden a method.

  - Added `unsafe_list::List`, an intrusive circular doubly-linked
    list, meant to be used as the basis for other linked lists.

    It is also used in the workqueue-based executor to keep track of
    all tasks since it is cheaper than other options.

  - Initial RCU support: a `Guard` type that represents evidence that
    the RCU read side lock is held on the current thread/CPU.

    In addition, `Revocable` now uses this new abstraction so that
    users can provide evidence of the RCU read side lock being held
    when accessing the protected object, e.g.:

        fn add_pair(value: &Revocable<(u32, u32)>) -> Option<u32> {
            let guard = rcu::read_lock();
            let pair = value.try_access_with_guard(&guard)?;
            Some(pair.0 + pair.1)
        }

  - Added `StaticRef` which allows the creation of "reference-counted"
    globals; i.e. allows to define static variables that can be used
    when `Ref<T>` or `RefBorrow<'_, T>` are expected.

    This, in turn, allows to have functions that return shared
    resources (e.g. a global workqueue) without allocations (the
    shared object is statically allocated).

  - Added `Task::spawn()` function to create and automatically run
    kernel threads easily, e.g.:

        for i in 0..10 {
            Task::spawn(fmt!("test{i}"), threadfn).unwrap();
        }

  - Added `Task::wake_up()` method.

  - Converted `Task` to use `ARef` to unify the usage of all
    ref-counted C structures.

  - Initial support for delays/sleeps (`delay` module) with a basic
    `coarse_sleep()` function that wraps the C side `msleep()` and
    takes advantage of the `Duration` standard library type:

        coarse_sleep(Duration::from_millis(20));

  - Added file flags (to further reduce `bindings::*` usage), e.g.:

        let blocking = (file.flags() & file::flags::O_NONBLOCK) == 0;

  - Added `gpio_chip_register!` and `gpio_irq_chip_register!` macros
    which automatically define the required lock classes.

  - Removal of `bindings::lock_class_key` from drivers. This gets us
    closer to eventually make bindings private to the `kernel` crate.

  - Moved usage of `ManuallyDrop` to `MaybeUninit` in `Revocable`,
    which was unsound.

  - Other cleanups, fixes and improvements.


## Patch series updates

The patch series has been reorganized a bit since last time:

  - The `include/linux/` changes for the C helpers have been moved
    into their own small patches, which can be taken independently
    as prerequisite patches if needed.

  - Now that the bindings are in their own `bindings` crate,
    they also get their own patch.

  - There is a new patch that adds the `kernel/configs/rust.config`.

  - One of the `kallsyms` patches has been split into three smaller
    ones.

  - Cleaned up some "exceeds 100 columns" `checkpatch.pl` warnings.
    With this final cleanup, the remaining warnings (of all kinds)
    are either false positives, or cannot be changed without diverging
    with upstream `alloc` or would make things look worse.


## Patch series status

The Rust support is still to be considered experimental. However,
support is good enough that kernel developers can start working on the
Rust abstractions for subsystems and write drivers and other modules.

The current series will appear in the next `linux-next`, as usual.
Similarly, the preview docs for this series can be seen at:

    https://rust-for-linux.github.io/docs/kernel/

As usual, please see the following link for the live list of unstable
Rust features we are using:

    https://github.com/Rust-for-Linux/linux/issues/2


## Conferences, meetings and liaisons

Join us in LPC 2022 (Linux Plumbers Conference) for the Rust MC
(microconference)! The schedule is available at:

    https://lpc.events/event/16/sessions/150/

We will be talking about GCC Rust (the Rust frontend for GCC),
`rustc_codegen_gcc` (the GCC backend for `rustc`), Rust for Linux,
the Rust NVMe driver, the integration of Rust with the Kernel Testing
Service and Rust in the Kernel (via eBPF).

In addition, I would like to personally thank Google and ISRG
(Internet Security Research Group) for sponsoring Kangrejos,
the Rust for Linux workshop:

    https://kangrejos.com

Furthermore, we would like to thank the venues we were invited to:

  - Linux Foundation Live Mentorship Series
  - Open Source Summit North America
  - Huawei Global Software Technology Summit


## Related news

The GCC Steering Committee accepted the contribution of the Rust
frontend (GCC Rust). Its first released version (experimental,
disabled by default) should appear in GCC 13. The first round of
patches has been posted to the gcc-patches mailing list.

`rustc_codegen_gcc` (the GCC backend for `rustc`) has seen enough
progress on SIMD support to compile `stdarch`. In addition, more
prerequisite patches are making their way into GCC.


## Acknowledgements

The signatures in the main commits correspond to the people that
wrote code that has ended up in them at the present time. For details
on contributions to code and discussions, please see our repository:

    https://github.com/Rust-for-Linux/linux

However, we would like to give credit to everyone that has contributed
in one way or another to the Rust for Linux project. Since the
previous cover letter:

  - Nick Desaulniers, Joe Perches, Masahiro Yamada and Jarkko Sakkinen
    for their reviews of some of the v7 patches.

  - Daniel Latypov, Brendan Higgins and Shuah Khan for picking up
    the KUnit prerequisite patch.

  - As usual, Björn Roy Baron (bjorn3) and Gary Guo for all the input
    on Rust compiler details, reviews and suggestions.

  - Andreas Hindborg for working on the NVMe driver, as well as
    adding atomic allocations for `Box` and allowing to use GFP flags
    for `KernelAllocator`.

  - Li Hongyu for working on a virtio abstraction.

  - Boqun Feng for working on adding an alloc alignment test.

  - Andreas Reindl for working on adding missing `SAFETY` comments.

  - Anhad Singh for working on adding the `new_with_flags` method
    to `Pages`.

  - Finn Behrens for working on making it possible to compile
    the kernel on macOS with Rust enabled.

  - Roel Kluin for working on code refactorings.

  - Wei Liu for taking the time to answer questions from newcomers
    in Zulip.

  - Philip Li, Yujie Liu et al. for continuing their work on adding
    Rust support to the Intel 0DAY/LKP kernel test robot.

  - Philip Herron and Arthur Cohen (and his supporters Open Source
    Security and Embecosm) et al. for their ongoing work on GCC Rust.

  - Antoni Boucher (and his supporters) et al. for their ongoing
    work on `rustc_codegen_gcc`.

  - Emilio Cobos Álvarez et. al. for their work on `bindgen`,
    including on issues that affect the kernel.

  - Mats Larsen, Marc Poulhiès et al. for their ongoing work on
    improving Rust support in Compiler Explorer.

  - Many folks that have reported issues, tested the project,
    helped spread the word, joined discussions and contributed in
    other ways!

Please see also the acknowledgements on the previous cover letters.


Boqun Feng (2):
  kallsyms: use `sizeof` instead of hardcoded size
  kallsyms: avoid hardcoding buffer size

Gary Guo (2):
  rust: add `build_error` crate
  vsprintf: add new `%pA` format specifier

Miguel Ojeda (19):
  kallsyms: add static relationship between `KSYM_NAME_LEN{,_BUFFER}`
  kallsyms: support "big" kernel symbols
  kallsyms: increase maximum kernel symbol length to 512
  rust: add C helpers
  rust: add `compiler_builtins` crate
  rust: import upstream `alloc` crate
  rust: adapt `alloc` crate to the kernel
  rust: add `macros` crate
  rust: add `bindings` crate
  rust: export generated symbols
  scripts: checkpatch: diagnose uses of `%pA` in the C side as errors
  scripts: checkpatch: enable language-independent checks for Rust
  scripts: add `rustdoc_test_{builder,gen}.py` scripts
  scripts: add `generate_rust_analyzer.py` scripts
  scripts: decode_stacktrace: demangle Rust symbols
  docs: add Rust documentation
  Kbuild: add Rust support
  samples: add Rust examples
  MAINTAINERS: Rust

Wedson Almeida Filho (8):
  workqueue: introduce `__INIT_WORK_WITH_KEY`
  locking/spinlock: introduce `__spin_lock_init`
  locking/spinlock: introduce `_raw_spin_lock_init`
  rust: add `kernel` crate's `sync` module
  rust: add `kernel` crate
  configs: add `rust` config
  [RFC] drivers: gpio: PrimeCell PL061 in Rust
  [RFC] drivers: android: Binder IPC in Rust

 .gitignore                                   |    6 +
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 Documentation/process/changes.rst            |   41 +
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 Documentation/rust/coding-guidelines.rst     |  216 ++
 Documentation/rust/general-information.rst   |   79 +
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 drivers/android/context.rs                   |   80 +
 drivers/android/defs.rs                      |   99 +
 drivers/android/node.rs                      |  476 +++
 drivers/android/process.rs                   |  961 +++++
 drivers/android/range_alloc.rs               |  189 +
 drivers/android/rust_binder.rs               |  106 +
 drivers/android/thread.rs                    |  871 +++++
 drivers/android/transaction.rs               |  326 ++
 drivers/gpio/Kconfig                         |    8 +
 drivers/gpio/Makefile                        |    1 +
 drivers/gpio/gpio_pl061_rust.rs              |  367 ++
 include/linux/compiler_types.h               |    6 +-
 include/linux/kallsyms.h                     |    2 +-
 include/linux/spinlock.h                     |   17 +-
 include/linux/workqueue.h                    |   21 +-
 include/uapi/linux/android/binder.h          |   30 +-
 init/Kconfig                                 |   46 +-
 kernel/configs/rust.config                   |    1 +
 kernel/kallsyms.c                            |   26 +-
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 rust/.gitignore                              |   10 +
 rust/Makefile                                |  415 +++
 rust/alloc/README.md                         |   33 +
 rust/alloc/alloc.rs                          |  440 +++
 rust/alloc/borrow.rs                         |  498 +++
 rust/alloc/boxed.rs                          | 2026 +++++++++++
 rust/alloc/boxed/thin.rs                     |  219 ++
 rust/alloc/collections/mod.rs                |  156 +
 rust/alloc/ffi/c_str.rs                      | 1203 ++++++
 rust/alloc/ffi/mod.rs                        |   93 +
 rust/alloc/fmt.rs                            |  614 ++++
 rust/alloc/lib.rs                            |  239 ++
 rust/alloc/macros.rs                         |  128 +
 rust/alloc/raw_vec.rs                        |  567 +++
 rust/alloc/slice.rs                          | 1295 +++++++
 rust/alloc/str.rs                            |  641 ++++
 rust/alloc/string.rs                         | 2944 +++++++++++++++
 rust/alloc/vec/drain.rs                      |  186 +
 rust/alloc/vec/drain_filter.rs               |  145 +
 rust/alloc/vec/into_iter.rs                  |  365 ++
 rust/alloc/vec/is_zero.rs                    |  120 +
 rust/alloc/vec/mod.rs                        | 3420 ++++++++++++++++++
 rust/alloc/vec/partial_eq.rs                 |   49 +
 rust/alloc/vec/set_len_on_drop.rs            |   30 +
 rust/alloc/vec/spec_extend.rs                |  174 +
 rust/bindgen_parameters                      |   21 +
 rust/bindings/bindings_helper.h              |   49 +
 rust/bindings/lib.rs                         |   57 +
 rust/build_error.rs                          |   29 +
 rust/compiler_builtins.rs                    |   79 +
 rust/exports.c                               |   21 +
 rust/helpers.c                               |  679 ++++
 rust/kernel/allocator.rs                     |   64 +
 rust/kernel/amba.rs                          |  261 ++
 rust/kernel/build_assert.rs                  |   83 +
 rust/kernel/chrdev.rs                        |  206 ++
 rust/kernel/clk.rs                           |   79 +
 rust/kernel/cred.rs                          |   46 +
 rust/kernel/delay.rs                         |  104 +
 rust/kernel/device.rs                        |  527 +++
 rust/kernel/driver.rs                        |  442 +++
 rust/kernel/error.rs                         |  564 +++
 rust/kernel/file.rs                          |  887 +++++
 rust/kernel/fs.rs                            |  846 +++++
 rust/kernel/fs/param.rs                      |  553 +++
 rust/kernel/gpio.rs                          |  505 +++
 rust/kernel/hwrng.rs                         |  210 ++
 rust/kernel/io_buffer.rs                     |  153 +
 rust/kernel/io_mem.rs                        |  278 ++
 rust/kernel/iov_iter.rs                      |   81 +
 rust/kernel/irq.rs                           |  681 ++++
 rust/kernel/kasync.rs                        |   50 +
 rust/kernel/kasync/executor.rs               |  154 +
 rust/kernel/kasync/executor/workqueue.rs     |  291 ++
 rust/kernel/kasync/net.rs                    |  322 ++
 rust/kernel/kunit.rs                         |   91 +
 rust/kernel/lib.rs                           |  267 ++
 rust/kernel/linked_list.rs                   |  247 ++
 rust/kernel/miscdev.rs                       |  290 ++
 rust/kernel/mm.rs                            |  149 +
 rust/kernel/module_param.rs                  |  499 +++
 rust/kernel/net.rs                           |  392 ++
 rust/kernel/net/filter.rs                    |  447 +++
 rust/kernel/of.rs                            |   63 +
 rust/kernel/pages.rs                         |  144 +
 rust/kernel/platform.rs                      |  223 ++
 rust/kernel/power.rs                         |  118 +
 rust/kernel/prelude.rs                       |   36 +
 rust/kernel/print.rs                         |  406 +++
 rust/kernel/random.rs                        |   42 +
 rust/kernel/raw_list.rs                      |  361 ++
 rust/kernel/rbtree.rs                        |  563 +++
 rust/kernel/revocable.rs                     |  425 +++
 rust/kernel/security.rs                      |   38 +
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 rust/kernel/sysctl.rs                        |  199 +
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 rust/kernel/types.rs                         |  705 ++++
 rust/kernel/unsafe_list.rs                   |  680 ++++
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 samples/rust/rust_echo_server.rs             |   60 +
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 198 files changed, 43688 insertions(+), 75 deletions(-)
 create mode 100644 .rustfmt.toml
 create mode 100644 Documentation/rust/arch-support.rst
 create mode 100644 Documentation/rust/coding-guidelines.rst
 create mode 100644 Documentation/rust/general-information.rst
 create mode 100644 Documentation/rust/index.rst
 create mode 100644 Documentation/rust/quick-start.rst
 create mode 100644 drivers/android/allocation.rs
 create mode 100644 drivers/android/context.rs
 create mode 100644 drivers/android/defs.rs
 create mode 100644 drivers/android/node.rs
 create mode 100644 drivers/android/process.rs
 create mode 100644 drivers/android/range_alloc.rs
 create mode 100644 drivers/android/rust_binder.rs
 create mode 100644 drivers/android/thread.rs
 create mode 100644 drivers/android/transaction.rs
 create mode 100644 drivers/gpio/gpio_pl061_rust.rs
 create mode 100644 kernel/configs/rust.config
 create mode 100644 rust/.gitignore
 create mode 100644 rust/Makefile
 create mode 100644 rust/alloc/README.md
 create mode 100644 rust/alloc/alloc.rs
 create mode 100644 rust/alloc/borrow.rs
 create mode 100644 rust/alloc/boxed.rs
 create mode 100644 rust/alloc/boxed/thin.rs
 create mode 100644 rust/alloc/collections/mod.rs
 create mode 100644 rust/alloc/ffi/c_str.rs
 create mode 100644 rust/alloc/ffi/mod.rs
 create mode 100644 rust/alloc/fmt.rs
 create mode 100644 rust/alloc/lib.rs
 create mode 100644 rust/alloc/macros.rs
 create mode 100644 rust/alloc/raw_vec.rs
 create mode 100644 rust/alloc/slice.rs
 create mode 100644 rust/alloc/str.rs
 create mode 100644 rust/alloc/string.rs
 create mode 100644 rust/alloc/vec/drain.rs
 create mode 100644 rust/alloc/vec/drain_filter.rs
 create mode 100644 rust/alloc/vec/into_iter.rs
 create mode 100644 rust/alloc/vec/is_zero.rs
 create mode 100644 rust/alloc/vec/mod.rs
 create mode 100644 rust/alloc/vec/partial_eq.rs
 create mode 100644 rust/alloc/vec/set_len_on_drop.rs
 create mode 100644 rust/alloc/vec/spec_extend.rs
 create mode 100644 rust/bindgen_parameters
 create mode 100644 rust/bindings/bindings_helper.h
 create mode 100644 rust/bindings/lib.rs
 create mode 100644 rust/build_error.rs
 create mode 100644 rust/compiler_builtins.rs
 create mode 100644 rust/exports.c
 create mode 100644 rust/helpers.c
 create mode 100644 rust/kernel/allocator.rs
 create mode 100644 rust/kernel/amba.rs
 create mode 100644 rust/kernel/build_assert.rs
 create mode 100644 rust/kernel/chrdev.rs
 create mode 100644 rust/kernel/clk.rs
 create mode 100644 rust/kernel/cred.rs
 create mode 100644 rust/kernel/delay.rs
 create mode 100644 rust/kernel/device.rs
 create mode 100644 rust/kernel/driver.rs
 create mode 100644 rust/kernel/error.rs
 create mode 100644 rust/kernel/file.rs
 create mode 100644 rust/kernel/fs.rs
 create mode 100644 rust/kernel/fs/param.rs
 create mode 100644 rust/kernel/gpio.rs
 create mode 100644 rust/kernel/hwrng.rs
 create mode 100644 rust/kernel/io_buffer.rs
 create mode 100644 rust/kernel/io_mem.rs
 create mode 100644 rust/kernel/iov_iter.rs
 create mode 100644 rust/kernel/irq.rs
 create mode 100644 rust/kernel/kasync.rs
 create mode 100644 rust/kernel/kasync/executor.rs
 create mode 100644 rust/kernel/kasync/executor/workqueue.rs
 create mode 100644 rust/kernel/kasync/net.rs
 create mode 100644 rust/kernel/kunit.rs
 create mode 100644 rust/kernel/lib.rs
 create mode 100644 rust/kernel/linked_list.rs
 create mode 100644 rust/kernel/miscdev.rs
 create mode 100644 rust/kernel/mm.rs
 create mode 100644 rust/kernel/module_param.rs
 create mode 100644 rust/kernel/net.rs
 create mode 100644 rust/kernel/net/filter.rs
 create mode 100644 rust/kernel/of.rs
 create mode 100644 rust/kernel/pages.rs
 create mode 100644 rust/kernel/platform.rs
 create mode 100644 rust/kernel/power.rs
 create mode 100644 rust/kernel/prelude.rs
 create mode 100644 rust/kernel/print.rs
 create mode 100644 rust/kernel/random.rs
 create mode 100644 rust/kernel/raw_list.rs
 create mode 100644 rust/kernel/rbtree.rs
 create mode 100644 rust/kernel/revocable.rs
 create mode 100644 rust/kernel/security.rs
 create mode 100644 rust/kernel/static_assert.rs
 create mode 100644 rust/kernel/std_vendor.rs
 create mode 100644 rust/kernel/str.rs
 create mode 100644 rust/kernel/sync.rs
 create mode 100644 rust/kernel/sync/arc.rs
 create mode 100644 rust/kernel/sync/condvar.rs
 create mode 100644 rust/kernel/sync/guard.rs
 create mode 100644 rust/kernel/sync/locked_by.rs
 create mode 100644 rust/kernel/sync/mutex.rs
 create mode 100644 rust/kernel/sync/nowait.rs
 create mode 100644 rust/kernel/sync/rcu.rs
 create mode 100644 rust/kernel/sync/revocable.rs
 create mode 100644 rust/kernel/sync/rwsem.rs
 create mode 100644 rust/kernel/sync/seqlock.rs
 create mode 100644 rust/kernel/sync/smutex.rs
 create mode 100644 rust/kernel/sync/spinlock.rs
 create mode 100644 rust/kernel/sysctl.rs
 create mode 100644 rust/kernel/task.rs
 create mode 100644 rust/kernel/types.rs
 create mode 100644 rust/kernel/unsafe_list.rs
 create mode 100644 rust/kernel/user_ptr.rs
 create mode 100644 rust/kernel/workqueue.rs
 create mode 100644 rust/macros/concat_idents.rs
 create mode 100644 rust/macros/helpers.rs
 create mode 100644 rust/macros/lib.rs
 create mode 100644 rust/macros/module.rs
 create mode 100644 rust/macros/vtable.rs
 create mode 100644 samples/rust/Kconfig
 create mode 100644 samples/rust/Makefile
 create mode 100644 samples/rust/hostprogs/.gitignore
 create mode 100644 samples/rust/hostprogs/Makefile
 create mode 100644 samples/rust/hostprogs/a.rs
 create mode 100644 samples/rust/hostprogs/b.rs
 create mode 100644 samples/rust/hostprogs/single.rs
 create mode 100644 samples/rust/rust_chrdev.rs
 create mode 100644 samples/rust/rust_echo_server.rs
 create mode 100644 samples/rust/rust_fs.rs
 create mode 100644 samples/rust/rust_minimal.rs
 create mode 100644 samples/rust/rust_miscdev.rs
 create mode 100644 samples/rust/rust_module_parameters.rs
 create mode 100644 samples/rust/rust_netfilter.rs
 create mode 100644 samples/rust/rust_platform.rs
 create mode 100644 samples/rust/rust_print.rs
 create mode 100644 samples/rust/rust_random.rs
 create mode 100644 samples/rust/rust_selftests.rs
 create mode 100644 samples/rust/rust_semaphore.rs
 create mode 100644 samples/rust/rust_semaphore_c.c
 create mode 100644 samples/rust/rust_stack_probing.rs
 create mode 100644 samples/rust/rust_sync.rs
 create mode 100755 scripts/generate_rust_analyzer.py
 create mode 100644 scripts/generate_rust_target.rs
 create mode 100755 scripts/is_rust_module.sh
 create mode 100644 scripts/rust-is-available-bindgen-libclang.h
 create mode 100755 scripts/rust-is-available.sh
 create mode 100755 scripts/rustdoc_test_builder.py
 create mode 100755 scripts/rustdoc_test_gen.py


base-commit: 3d7cb6b04c3f3115719235cc6866b10326de34cd
-- 
2.37.1

[PATCH v8 19/31] vsprintf: add new `%pA` format specifier

[Miguel Ojeda]

From: Gary Guo <gary@garyguo.net>

This patch adds a format specifier `%pA` to `vsprintf` which formats
a pointer as `core::fmt::Arguments`. Doing so allows us to directly
format to the internal buffer of `printf`, so we do not have to use
a temporary buffer on the stack to pre-assemble the message on
the Rust side.

This specifier is intended only to be used from Rust and not for C, so
`checkpatch.pl` is intentionally unchanged to catch any misuse.

Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Petr Mladek <pmladek@suse.com>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 Documentation/core-api/printk-formats.rst | 10 ++++++++++
 lib/vsprintf.c                            | 13 +++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 5e89497ba314..dbe1aacc79d0 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -625,6 +625,16 @@ Examples::
 	%p4cc	Y10  little-endian (0x20303159)
 	%p4cc	NV12 big-endian (0xb231564e)
 
+Rust
+----
+
+::
+
+	%pA
+
+Only intended to be used from Rust code to format ``core::fmt::Arguments``.
+Do *not* use it from C.
+
 Thanks
 ======
 
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3c1853a9d1c0..c414a8d9f1ea 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -2246,6 +2246,9 @@ int __init no_hash_pointers_enable(char *str)
 }
 early_param("no_hash_pointers", no_hash_pointers_enable);
 
+/* Used for Rust formatting ('%pA'). */
+char *rust_fmt_argument(char *buf, char *end, void *ptr);
+
 /*
  * Show a '%p' thing.  A kernel extension is that the '%p' is followed
  * by an extra set of alphanumeric characters that are extended format
@@ -2372,6 +2375,10 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
  *
  * Note: The default behaviour (unadorned %p) is to hash the address,
  * rendering it useful as a unique identifier.
+ *
+ * There is also a '%pA' format specifier, but it is only intended to be used
+ * from Rust code to format core::fmt::Arguments. Do *not* use it from C.
+ * See rust/kernel/print.rs for details.
  */
 static noinline_for_stack
 char *pointer(const char *fmt, char *buf, char *end, void *ptr,
@@ -2444,6 +2451,12 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 		return device_node_string(buf, end, ptr, spec, fmt + 1);
 	case 'f':
 		return fwnode_string(buf, end, ptr, spec, fmt + 1);
+	case 'A':
+		if (!IS_ENABLED(CONFIG_RUST)) {
+			WARN_ONCE(1, "Please remove %%pA from non-Rust code\n");
+			return error_string(buf, end, "(%pA?)", spec);
+		}
+		return rust_fmt_argument(buf, end, ptr);
 	case 'x':
 		return pointer_string(buf, end, ptr, spec);
 	case 'e':
-- 
2.37.1

[PATCH v8 26/31] docs: add Rust documentation

[Miguel Ojeda]

Most of the documentation for Rust is written within the source code
itself, as it is idiomatic for Rust projects. This applies to both
the shared infrastructure at `rust/` as well as any other Rust module
(e.g. drivers) written across the kernel.

However, these documents contain general information that does not
fit particularly well in the source code, like the Quick Start guide.

It also contains a few other small changes elsewhere in the
documentation folder.

Reviewed-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Finn Behrens <me@kloenk.de>
Signed-off-by: Finn Behrens <me@kloenk.de>
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Co-developed-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Co-developed-by: Wu XiangCheng <bobwxc@email.cn>
Signed-off-by: Wu XiangCheng <bobwxc@email.cn>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Signed-off-by: Boris-Chengbiao Zhou <bobo1239@web.de>
Co-developed-by: Yuki Okushi <jtitor@2k36.org>
Signed-off-by: Yuki Okushi <jtitor@2k36.org>
Co-developed-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Co-developed-by: Daniel Xu <dxu@dxuuu.xyz>
Signed-off-by: Daniel Xu <dxu@dxuuu.xyz>
Co-developed-by: Julian Merkle <me@jvmerkle.de>
Signed-off-by: Julian Merkle <me@jvmerkle.de>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 Documentation/doc-guide/kernel-doc.rst     |   3 +
 Documentation/index.rst                    |   1 +
 Documentation/kbuild/kbuild.rst            |  17 ++
 Documentation/kbuild/makefiles.rst         |  50 ++++-
 Documentation/process/changes.rst          |  41 ++++
 Documentation/rust/arch-support.rst        |  23 ++
 Documentation/rust/coding-guidelines.rst   | 216 +++++++++++++++++++
 Documentation/rust/general-information.rst |  79 +++++++
 Documentation/rust/index.rst               |  22 ++
 Documentation/rust/quick-start.rst         | 232 +++++++++++++++++++++
 10 files changed, 680 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/rust/arch-support.rst
 create mode 100644 Documentation/rust/coding-guidelines.rst
 create mode 100644 Documentation/rust/general-information.rst
 create mode 100644 Documentation/rust/index.rst
 create mode 100644 Documentation/rust/quick-start.rst

diff --git a/Documentation/doc-guide/kernel-doc.rst b/Documentation/doc-guide/kernel-doc.rst
index a7cb2afd7990..9b868d9eb20f 100644
--- a/Documentation/doc-guide/kernel-doc.rst
+++ b/Documentation/doc-guide/kernel-doc.rst
@@ -12,6 +12,9 @@ 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 67036a05b771..35d90903242a 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..bcc92cae11d9
--- /dev/null
+++ b/Documentation/rust/arch-support.rst
@@ -0,0 +1,23 @@
+.. 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
+============  ================  ==============================================
+``arm``       Maintained        ``armv6`` and compatible only.
+``arm64``     Maintained        None.
+``powerpc``   Maintained        ``ppc64le`` only.
+``riscv``     Maintained        ``riscv64`` only.
+``x86``       Maintained        ``x86_64`` only.
+============  ================  ==============================================
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``).
-- 
2.37.1

Re: [PATCH v8 00/31] Rust support

[Matthew Wilcox]

On Tue, Aug 02, 2022 at 03:49:47AM +0200, Miguel Ojeda wrote:
> Some of the improvements to the abstractions and example drivers are:
> 
>   - Filesystem support (`fs` module), including:
> 
>       + `INode` type (which wraps `struct inode`).
>       + `DEntry` type (which wraps `struct dentry`).
>       + `Filename` type (which wraps `struct filename`).
>       + `Registration` type.
>       + `Type` and `Context` traits.
>       + `SuperBlock` type (which wraps `struct super_block` and takes
>         advantage of typestates for its initialization).
>       + File system parameters support (with a `Value` enum; `Spec*`
>         and `Constant*` types, `define_fs_params!` macro...).
>       + File system flags.
>       + `module_fs!` macro to simplify registering kernel modules that
>         only implement a single file system.
>       + A file system sample.

None of this (afaict) has been discussed on linux-fsdevel.  And I may
have missed somethiing, but I don't see the fs module in this series
of patches.  Could linux-fsdevel be cc'd on the development of Rust
support for filesystems in the future?

Re: [PATCH v8 00/31] Rust support

[Miguel Ojeda]

Hi Willy,

On Tue, Aug 2, 2022 at 2:26 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> None of this (afaict) has been discussed on linux-fsdevel.  And I may
> have missed somethiing, but I don't see the fs module in this series
> of patches.  Could linux-fsdevel be cc'd on the development of Rust
> support for filesystems in the future?

In order to provide example drivers and kernel modules, we need to
have some safe abstractions for them, thus we are adding some as we
need them.

More importantly, the abstractions also serve as a showcase of how
they may be written in the future if Rust support is merged.

This does not mean these abstractions are a final design or that we
plan to develop them independently of subsystem maintainers. In fact,
we would prefer the opposite: in the future, when the support is
merged and more people start having more experience with Rust, we hope
that the respective kernel maintainers start developing and
maintaining the abstractions themselves.

But we have to start somewhere, and at least provide enough examples
to serve as guidance and to show that it is actually possible to write
abstractions that restrict the amount of unsafe code.

And, of course, if you are already interested in developing them, that
would be actually great and we would love your input and/or that you
join us.

As for the `fs` module, I see in lore 2 patches didn't make it
through, but I didn't get a bounce (I do get bounces for the
rust-for-linux ML, but I was told that was fine as long as LKML got
them). Sorry about that... I will ask what to do.

Meanwhile, you can see the patches in this branch:

    https://github.com/Rust-for-Linux/linux.git rust-next

Cheers,
Miguel

Re: [PATCH v8 00/31] Rust support

[Christoph Hellwig]

Miguel,

handwaiving and pointing to git trees is not how Linux development
works.  Please make sure all the patches go to the relevant lists
and maintainers first, and actually do have ACKs.

Re: [PATCH v8 00/31] Rust support

[Miguel Ojeda]

On Tue, Aug 2, 2022 at 3:48 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> handwaiving and pointing to git trees is not how Linux development
> works.  Please make sure all the patches go to the relevant lists
> and maintainers first, and actually do have ACKs.

Which hand-waving? In fact, we were requested to do it like this.

As for the Cc's, if any ML wants to be Cc'd for an abstraction we
create, even if no C code is modified on their side, I am more than
happy to Cc them. I can even do that by default, but not everyone may
want to hear about the Rust side just yet, so I have not been doing it
so far.

Cheers,
Miguel

Re: [PATCH v8 00/31] Rust support

[Matthew Wilcox]

On Tue, Aug 02, 2022 at 03:45:50PM +0200, Miguel Ojeda wrote:
> Hi Willy,
> 
> On Tue, Aug 2, 2022 at 2:26 PM Matthew Wilcox <willy@infradead.org> wrote:
> >
> > None of this (afaict) has been discussed on linux-fsdevel.  And I may
> > have missed somethiing, but I don't see the fs module in this series
> > of patches.  Could linux-fsdevel be cc'd on the development of Rust
> > support for filesystems in the future?
> 
> In order to provide example drivers and kernel modules, we need to
> have some safe abstractions for them, thus we are adding some as we
> need them.
> 
> More importantly, the abstractions also serve as a showcase of how
> they may be written in the future if Rust support is merged.
> 
> This does not mean these abstractions are a final design or that we
> plan to develop them independently of subsystem maintainers. In fact,
> we would prefer the opposite: in the future, when the support is
> merged and more people start having more experience with Rust, we hope
> that the respective kernel maintainers start developing and
> maintaining the abstractions themselves.
> 
> But we have to start somewhere, and at least provide enough examples
> to serve as guidance and to show that it is actually possible to write
> abstractions that restrict the amount of unsafe code.
> 
> And, of course, if you are already interested in developing them, that
> would be actually great and we would love your input and/or that you
> join us.

No objections to any of this.  I love the idea of being able to write
filesystems in Rust.  I just think it would go more smoothly if
linux-fsdevel were involved more closely so people at least have the
option of being able to follow design decisions, and hopefully influence
them.  That goes both ways, of course; I hardly think our current
operations structures are the optimum way to implement a filesystem,
and having fresh eyes say things like "But that shouldn't be part of the
address_space_operations" can impel better abstractions.

> As for the `fs` module, I see in lore 2 patches didn't make it
> through, but I didn't get a bounce (I do get bounces for the
> rust-for-linux ML, but I was told that was fine as long as LKML got
> them). Sorry about that... I will ask what to do.

The obvious answer is to split out the 'fs module' into its own patch
;-)  I presume it was part of the kernel crate which would have been
either patch 17 or 11 in that series?

> Meanwhile, you can see the patches in this branch:
> 
>     https://github.com/Rust-for-Linux/linux.git rust-next
> 
> Cheers,
> Miguel

Re: [PATCH v8 00/31] Rust support

[Miguel Ojeda]

On Tue, Aug 2, 2022 at 4:01 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> No objections to any of this.  I love the idea of being able to write
> filesystems in Rust.  I just think it would go more smoothly if
> linux-fsdevel were involved more closely so people at least have the
> option of being able to follow design decisions, and hopefully influence
> them.  That goes both ways, of course; I hardly think our current
> operations structures are the optimum way to implement a filesystem,
> and having fresh eyes say things like "But that shouldn't be part of the
> address_space_operations" can impel better abstractions.

I will send the patches to fsdevel then!

As for following development closely and design decisions, we have
been doing it in GitHub so far pre-merge, so the easiest until the
merge (for us) would be to ping you there. We can also send you copies
of the `fs` related patches too if you would like that. I would highly
recommend joining the monthly informal calls too.

(I appreciate the kind answer, by the way!)

> The obvious answer is to split out the 'fs module' into its own patch
> ;-)  I presume it was part of the kernel crate which would have been
> either patch 17 or 11 in that series?

Yeah, patch 17, exactly (patch 11 is the `alloc` import). I have asked
Konstantin privately about them.

In any case, I will split the patches further for v9 which should help.

Meanwhile, you can also see the `fs` module here, if you are curious:

    https://github.com/Rust-for-Linux/linux/blob/rust-next/rust/kernel/fs.rs
    https://github.com/Rust-for-Linux/linux/blob/rust-next/rust/kernel/fs/param.rs

Cheers,
Miguel

Re: [PATCH v8 00/31] Rust support

[Miguel Ojeda]

On Tue, Aug 2, 2022 at 5:09 PM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> Yeah, patch 17, exactly (patch 11 is the `alloc` import). I have asked
> Konstantin privately about them.

The patches are showing up now in lore -- not sure if it was just a
delay (which would be consistent with the lack of bounce) or somebody
did something (thank you if so!).

Cheers,
Miguel