pm24.git/rust/kernel/sync, branch rust-6.14

rust: kernel: add improved version of `ForeignOwnable::borrow_mut`

2025-01-13T22:46:07Z

Previously, the `ForeignOwnable` trait had a method called `borrow_mut` that was intended to provide mutable access to the inner value. However, the method accidentally made it possible to change the address of the object being modified, which usually isn't what we want. (And when we want that, it can be done by calling `from_foreign` and `into_foreign`, like how the old `borrow_mut` was implemented.) In this patch, we introduce an alternate definition of `borrow_mut` that solves the previous problem. Conceptually, given a pointer type `P` that implements `ForeignOwnable`, the `borrow_mut` method gives you the same kind of access as an `&mut P` would, except that it does not let you change the pointer `P` itself. This is analogous to how the existing `borrow` method provides the same kind of access to the inner value as an `&P`. Note that for types like `Arc`, having an `&mut Arc` only gives you immutable access to the inner `T`. This is because mutable references assume exclusive access, but there might be other handles to the same reference counted value, so the access isn't exclusive. The `Arc` type implements this by making `borrow_mut` return the same type as `borrow`. Signed-off-by: Alice Ryhl Reviewed-by: Boqun Feng Reviewed-by: Benno Lossin Reviewed-by: Martin Rodriguez Reboredo Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-6-80dbadd00951@gmail.com [ Updated to `crate::ffi::`. Reworded title slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kernel: reorder `ForeignOwnable` items

2025-01-13T22:45:54Z

`{into,from}_foreign` before `borrow` is slightly more logical. This removes an inconsistency with `kbox.rs` which already uses this ordering. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-5-80dbadd00951@gmail.com [ Reworded title slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: kernel: change `ForeignOwnable` pointer to mut

2025-01-13T22:45:31Z

It is slightly more convenient to operate on mut pointers, and this also properly conveys the desired ownership semantics of the trait. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-4-80dbadd00951@gmail.com [ Reworded title slightly. - Miguel ] Signed-off-by: Miguel Ojeda

rust: arc: split unsafe block, add missing comment

2025-01-13T22:45:31Z

The new SAFETY comment style is taken from existing comments in `deref` and `drop. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-3-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: types: avoid `as` casts

2025-01-13T22:45:30Z

Replace `as` casts with `cast{,_mut}` calls which are a bit safer. In one instance, remove an unnecessary `as` cast without replacement. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Acked-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-2-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: arc: use `NonNull::new_unchecked`

2025-01-13T22:45:30Z

There is no need to check (and panic on violations of) the safety requirements on `ForeignOwnable` functions. Avoiding the check is consistent with the implementation of `ForeignOwnable` for `Box`. Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-1-80dbadd00951@gmail.com Signed-off-by: Miguel Ojeda

rust: use derive(CoercePointee) on rustc >= 1.84.0

2025-01-13T22:45:30Z

The `kernel` crate relies on both `coerce_unsized` and `dispatch_from_dyn` unstable features. Alice Ryhl has proposed [1] the introduction of the unstable macro `SmartPointer` to reduce such dependence, along with a RFC patch [2]. Since Rust 1.81.0 this macro, later renamed to `CoercePointee` in Rust 1.84.0 [3], has been fully implemented with the naming discussion resolved. This feature is now on track to stabilization in the language. In order to do so, we shall start using this macro in the `kernel` crate to prove the functionality and utility of the macro as the justification of its stabilization. This patch makes this switch in such a way that the crate remains backward compatible with older Rust compiler versions, via the new Kconfig option `RUSTC_HAS_COERCE_POINTEE`. A minimal demonstration example is added to the `samples/rust/rust_print_main.rs` module. Link: https://rust-lang.github.io/rfcs/3621-derive-smart-pointer.html [1] Link: https://lore.kernel.org/all/20240823-derive-smart-pointer-v1-1-53769cd37239@google.com/ [2] Link: https://github.com/rust-lang/rust/pull/131284 [3] Signed-off-by: Xiangfei Ding Reviewed-by: Fiona Behrens Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20241203205050.679106-2-dingxiangfei2009@gmail.com [ Fixed version to 1.84. Renamed option to `RUSTC_HAS_COERCE_POINTEE` to match `CC_HAS_*` ones. Moved up new config option, closer to the `CC_HAS_*` ones. Simplified Kconfig line. Fixed typos and slightly reworded example and commit. Added Link to PR. - Miguel ] Signed-off-by: Miguel Ojeda

rust: sync: document `PhantomData` in `Arc`

2024-12-17T23:37:21Z

Add a comment explaining the relevant semantics of `PhantomData`. This should help future readers who may, as I did, assume that this field is redundant at first glance. Signed-off-by: Tamir Duberstein Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20241107-simplify-arc-v2-1-7256e638aac1@gmail.com Signed-off-by: Miguel Ojeda

Merge tag 'rust-6.13' of https://github.com/Rust-for-Linux/linux

2024-11-26T22:00:26Z

Pull rust updates from Miguel Ojeda: "Toolchain and infrastructure: - Enable a series of lints, including safety-related ones, e.g. the compiler will now warn about missing safety comments, as well as unnecessary ones. How safety documentation is organized is a frequent source of review comments, thus having the compiler guide new developers on where they are expected (and where not) is very nice. - Start using '#[expect]': an interesting feature in Rust (stabilized in 1.81.0) that makes the compiler warn if an expected warning was _not_ emitted. This is useful to avoid forgetting cleaning up locally ignored diagnostics ('#[allow]'s). - Introduce '.clippy.toml' configuration file for Clippy, the Rust linter, which will allow us to tweak its behaviour. For instance, our first use cases are declaring a disallowed macro and, more importantly, enabling the checking of private items. - Lints-related fixes and cleanups related to the items above. - Migrate from 'receiver_trait' to 'arbitrary_self_types': to get the kernel into stable Rust, one of the major pieces of the puzzle is the support to write custom types that can be used as 'self', i.e. as receivers, since the kernel needs to write types such as 'Arc' that common userspace Rust would not. 'arbitrary_self_types' has been accepted to become stable, and this is one of the steps required to get there. - Remove usage of the 'new_uninit' unstable feature. - Use custom C FFI types. Includes a new 'ffi' crate to contain our custom mapping, instead of using the standard library 'core::ffi' one. The actual remapping will be introduced in a later cycle. - Map '__kernel_{size_t,ssize_t,ptrdiff_t}' to 'usize'/'isize' instead of 32/64-bit integers. - Fix 'size_t' in bindgen generated prototypes of C builtins. - Warn on bindgen < 0.69.5 and libclang >= 19.1 due to a double issue in the projects, which we managed to trigger with the upcoming tracepoint support. It includes a build test since some distributions backported the fix (e.g. Debian -- thanks!). All major distributions we list should be now OK except Ubuntu non-LTS. 'macros' crate: - Adapt the build system to be able run the doctests there too; and clean up and enable the corresponding doctests. 'kernel' crate: - Add 'alloc' module with generic kernel allocator support and remove the dependency on the Rust standard library 'alloc' and the extension traits we used to provide fallible methods with flags. Add the 'Allocator' trait and its implementations '{K,V,KV}malloc'. Add the 'Box' type (a heap allocation for a single value of type 'T' that is also generic over an allocator and considers the kernel's GFP flags) and its shorthand aliases '{K,V,KV}Box'. Add 'ArrayLayout' type. Add 'Vec' (a contiguous growable array type) and its shorthand aliases '{K,V,KV}Vec', including iterator support. For instance, now we may write code such as: let mut v = KVec::new(); v.push(1, GFP_KERNEL)?; assert_eq!(&v, &[1]); Treewide, move as well old users to these new types. - 'sync' module: add global lock support, including the 'GlobalLockBackend' trait; the 'Global{Lock,Guard,LockedBy}' types and the 'global_lock!' macro. Add the 'Lock::try_lock' method. - 'error' module: optimize 'Error' type to use 'NonZeroI32' and make conversion functions public. - 'page' module: add 'page_align' function. - Add 'transmute' module with the existing 'FromBytes' and 'AsBytes' traits. - 'block::mq::request' module: improve rendered documentation. - 'types' module: extend 'Opaque' type documentation and add simple examples for the 'Either' types. drm/panic: - Clean up a series of Clippy warnings. Documentation: - Add coding guidelines for lints and the '#[expect]' feature. - Add Ubuntu to the list of distributions in the Quick Start guide. MAINTAINERS: - Add Danilo Krummrich as maintainer of the new 'alloc' module. And a few other small cleanups and fixes" * tag 'rust-6.13' of https://github.com/Rust-for-Linux/linux: (82 commits) rust: alloc: Fix `ArrayLayout` allocations docs: rust: remove spurious item in `expect` list rust: allow `clippy::needless_lifetimes` rust: warn on bindgen < 0.69.5 and libclang >= 19.1 rust: use custom FFI integer types rust: map `__kernel_size_t` and friends also to usize/isize rust: fix size_t in bindgen prototypes of C builtins rust: sync: add global lock support rust: macros: enable the rest of the tests rust: macros: enable paste! use from macro_rules! rust: enable macros::module! tests rust: kbuild: expand rusttest target for macros rust: types: extend `Opaque` documentation rust: block: fix formatting of `kernel::block::mq::request` module rust: macros: fix documentation of the paste! macro rust: kernel: fix THIS_MODULE header path in ThisModule doc comment rust: page: add Rust version of PAGE_ALIGN rust: helpers: remove unnecessary header includes rust: exports: improve grammar in commentary drm/panic: allow verbose version check ...

rust: use custom FFI integer types

2024-11-10T22:58:00Z

Currently FFI integer types are defined in libcore. This commit creates the `ffi` crate and asks bindgen to use that crate for FFI integer types instead of `core::ffi`. This commit is preparatory and no type changes are made in this commit yet. Signed-off-by: Gary Guo Link: https://lore.kernel.org/r/20240913213041.395655-4-gary@garyguo.net [ Added `rustdoc`, `rusttest` and KUnit tests support. Rebased on top of `rust-next` (e.g. migrated more `core::ffi` cases). Reworded crate docs slightly and formatted. - Miguel ] Signed-off-by: Miguel Ojeda