The kernel's allocators sometimes provide a higher alignment than the
end-user requested, so add a new constant on the Allocator trait to let
the allocator specify what its minimum guaranteed alignment is.
This allows the ForeignOwnable trait to provide a more accurate value of
FOREIGN_ALIGN when using a pointer type such as Box, which will be
useful with certain collections such as XArray that store its own data
in the low bits of pointers.
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250811-align-min-allocator-v2-1-3386cc94f4fc@google.com
[ Add helper for ARCH_KMALLOC_MINALIGN; remove cast to usize. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
aligned_size() dates back to when Rust did support kmalloc() only, but
is now used in ReallocFunc::call() and hence for all allocators.
However, the additional padding applied by aligned_size() is only
required by the kmalloc() allocator backend.
Hence, replace aligned_size() with Kmalloc::aligned_layout() and use it
for the affected allocators, i.e. kmalloc() and kvmalloc(), only.
While at it, make Kmalloc::aligned_layout() public, such that Rust
abstractions, which have to call subsystem specific kmalloc() based
allocation primitives directly, can make use of it.
Fixes: 8a799831fc ("rust: alloc: implement `ReallocFunc`")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250731154919.4132-2-dakr@kernel.org
[ Remove `const` from Kmalloc::aligned_layout(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Pull alloc and DMA updates from Danilo Krummrich:
Box:
- Implement Borrow / BorrowMut for Box<T, A>.
Vec:
- Implement Default for Vec<T, A>.
- Implement Borrow / BorrowMut for Vec<T, A>.
DMA:
- Clarify wording and be consistent in 'coherent' nomenclature.
- Convert the read!() / write!() macros to return a Result.
- Add as_slice() / write() methods in CoherentAllocation.
- Fix doc-comment of dma_handle().
- Expose count() and size() in CoherentAllocation and add the
corresponding type invariants.
- Implement CoherentAllocation::dma_handle_with_offset().
- Require mutable reference for as_slice_mut() and write().
MAINTAINERS:
- Add Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki and Lorenzo
Stoakes as reviewers (thanks everyone).
* tag 'alloc-next-v6.17-2025-07-15' of https://github.com/Rust-for-Linux/linux:
MAINTAINERS: add mm folks as reviewers to rust alloc
rust: dma: require mutable reference for as_slice_mut() and write()
rust: dma: add dma_handle_with_offset method to CoherentAllocation
rust: dma: expose the count and size of CoherentAllocation
rust: dma: fix doc-comment of dma_handle()
rust: dma: add as_slice/write functions for CoherentAllocation
rust: dma: convert the read/write macros to return Result
rust: dma: clarify wording and be consistent in `coherent` nomenclature
rust: alloc: implement `Borrow` and `BorrowMut` for `KBox`
rust: alloc: implement `Borrow` and `BorrowMut` for `Vec`
rust: vec: impl Default for Vec with any allocator
In Rust 1.51.0, Clippy introduced the `ptr_as_ptr` lint [1]:
> Though `as` casts between raw pointers are not terrible,
> `pointer::cast` is safer because it cannot accidentally change the
> pointer's mutability, nor cast the pointer to other types like `usize`.
There are a few classes of changes required:
- Modules generated by bindgen are marked
`#[allow(clippy::ptr_as_ptr)]`.
- Inferred casts (` as _`) are replaced with `.cast()`.
- Ascribed casts (` as *... T`) are replaced with `.cast::<T>()`.
- Multistep casts from references (` as *const _ as *const T`) are
replaced with `core::ptr::from_ref(&x).cast()` with or without `::<T>`
according to the previous rules. The `core::ptr::from_ref` call is
required because `(x as *const _).cast::<T>()` results in inference
failure.
- Native literal C strings are replaced with `c_str!().as_char_ptr()`.
- `*mut *mut T as _` is replaced with `let *mut *const T = (*mut *mut
T)`.cast();` since pointer to pointer can be confusing.
Apply these changes and enable the lint -- no functional change
intended.
Link: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_as_ptr [1]
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Tejun Heo <tj@kernel.org>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250615-ptr-as-ptr-v12-1-f43b024581e8@gmail.com
[ Added `.cast()` for `opp`. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Implement `Borrow<[T]>` and `BorrowMut<[T]>` for `Vec<T>`. This allows
`Vec<T>` to be used in generic APIs asking for types implementing those
traits. `[T; N]` and `&mut [T]` also implement those traits allowing
users to use either owned, borrowed and heap-owned values.
The implementation leverages `as_slice` and `as_mut_slice`.
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250616-borrow_impls-v4-1-36f9beb3fe6a@nvidia.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
The implementation of Default is restricted to only work with kmalloc
vectors for no good reason. This means I have to use
mem::replace(&mut my_vec, KVVec::new())
in Rust Binder instead of `mem::take(&mut my_vec)`. Thus, expand the
impl of Default to work with any allocator including kvmalloc.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250610-vec-default-v1-1-7bb2c97d75a0@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
For the Rust 1.87.0 release, Clippy was expected to warn with:
error: use `core::ptr::eq` when comparing raw pointers
--> rust/kernel/list.rs:438:12
|
438 | if self.first == item {
| ^^^^^^^^^^^^^^^^^^ help: try: `core::ptr::eq(self.first, item)`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq
= note: `-D clippy::ptr-eq` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(clippy::ptr_eq)]`
However, a backport to relax a bit the `clippy::ptr_eq` finally landed,
and thus Clippy did not warn by the time the release happened.
Thus remove the `allow`s added back then, which were added just in case
the backport did not land in time.
See commit a39f308709 ("rust: allow Rust 1.87.0's `clippy::ptr_eq`
lint") for details.
Link: https://github.com/rust-lang/rust/pull/140859 [1]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250520182125.806758-1-ojeda@kernel.org
[ Reworded for clarity. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Pull XArray updates from Andreas Hindborg:
"Introduce Rust support for the 'xarray' data structure:
- Add a Rust abstraction for the 'xarray' data structure. This
abstraction allows Rust code to leverage the 'xarray' to store
types that implement 'ForeignOwnable'. This support is a dependency
for memory backing feature of the Rust null block driver, which is
waiting to be merged.
- Set up an entry in MAINTAINERS for the XArray Rust support. Patches
will go to the new Rust XArray tree and then via the Rust subsystem
tree for now.
'kernel' crate:
- Allow 'ForeignOwnable' to carry information about the pointed-to
type. This helps asserting alignment requirements for the pointer
passed to the foreign language."
* tag 'rust-xarray-for-v6.16' of https://github.com/Rust-for-Linux/linux:
MAINTAINERS: add entry for Rust XArray API
rust: xarray: Add an abstraction for XArray
rust: types: add `ForeignOwnable::PointedTo`
This is needed by Rust Binder in the range allocator, and by upcoming
GPU drivers during firmware initialization.
Panics in the kernel are best avoided when possible, so an error is
returned if the index is out of bounds. An error type is used rather
than just returning Option<T> to let callers handle errors with ?.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-6-06d20ad9366f@google.com
[ Remove `# Panics` section; `Vec::remove() handles the error properly.`
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This adds a common Vec method called `retain` that removes all elements
that don't match a certain condition. Rust Binder uses it to find all
processes that match a given pid.
The stdlib retain method takes &T rather than &mut T and has a separate
retain_mut for the &mut T case. However, this is considered an API
mistake that can't be fixed now due to backwards compatibility. There's
no reason for us to repeat that mistake.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-5-06d20ad9366f@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This is like the stdlib method drain, except that it's hard-coded to use
the entire vector's range. Rust Binder uses it in the range allocator to
take ownership of everything in a vector in a case where reusing the
vector is desirable.
Implementing `DrainAll` in terms of `slice::IterMut` lets us reuse some
nice optimizations in core for the case where T is a ZST.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-4-06d20ad9366f@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This introduces a new method called `push_within_capacity` for appending
to a vector without attempting to allocate if the capacity is full. Rust
Binder will use this in various places to safely push to a vector while
holding a spinlock.
The implementation is moved to a push_within_capacity_unchecked method.
This is preferred over having push() call push_within_capacity()
followed by an unwrap_unchecked() for simpler unsafe.
Panics in the kernel are best avoided when possible, so an error is
returned if the vector does not have sufficient capacity. An error type
is used rather than just returning Result<(),T> to make it more
convenient for callers (i.e. they can use ? or unwrap).
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Link: https://lore.kernel.org/r/20250502-vec-methods-v5-3-06d20ad9366f@google.com
[ Remove public visibility from `Vec::push_within_capacity_unchecked()`.
- Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
