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

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
  ...

1 files changed, 143 insertions, 7 deletions

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index 1966bd407017..f2f7f3a53d29 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -1,23 +1,41 @@
 // SPDX-License-Identifier: GPL-2.0
 
-//! Extensions to the [`alloc`] crate.
+//! Implementation of the kernel's memory allocation infrastructure.
 
-#[cfg(not(test))]
-#[cfg(not(testlib))]
-mod allocator;
-pub mod box_ext;
-pub mod vec_ext;
+#[cfg(not(any(test, testlib)))]
+pub mod allocator;
+pub mod kbox;
+pub mod kvec;
+pub mod layout;
+
+#[cfg(any(test, testlib))]
+pub mod allocator_test;
+
+#[cfg(any(test, testlib))]
+pub use self::allocator_test as allocator;
+
+pub use self::kbox::Box;
+pub use self::kbox::KBox;
+pub use self::kbox::KVBox;
+pub use self::kbox::VBox;
+
+pub use self::kvec::IntoIter;
+pub use self::kvec::KVVec;
+pub use self::kvec::KVec;
+pub use self::kvec::VVec;
+pub use self::kvec::Vec;
 
 /// Indicates an allocation error.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct AllocError;
+use core::{alloc::Layout, ptr::NonNull};
 
 /// Flags to be used when allocating memory.
 ///
 /// They can be combined with the operators `|`, `&`, and `!`.
 ///
 /// Values can be used from the [`flags`] module.
-#[derive(Clone, Copy)]
+#[derive(Clone, Copy, PartialEq)]
 pub struct Flags(u32);
 
 impl Flags {
@@ -25,6 +43,11 @@ impl Flags {
     pub(crate) fn as_raw(self) -> u32 {
         self.0
     }
+
+    /// Check whether `flags` is contained in `self`.
+    pub fn contains(self, flags: Flags) -> bool {
+        (self & flags) == flags
+    }
 }
 
 impl core::ops::BitOr for Flags {
@@ -85,4 +108,117 @@ pub mod flags {
     /// use any filesystem callback.  It is very likely to fail to allocate memory, even for very
     /// small allocations.
     pub const GFP_NOWAIT: Flags = Flags(bindings::GFP_NOWAIT);
+
+    /// Suppresses allocation failure reports.
+    ///
+    /// This is normally or'd with other flags.
+    pub const __GFP_NOWARN: Flags = Flags(bindings::__GFP_NOWARN);
+}
+
+/// The kernel's [`Allocator`] trait.
+///
+/// An implementation of [`Allocator`] can allocate, re-allocate and free memory buffers described
+/// via [`Layout`].
+///
+/// [`Allocator`] is designed to be implemented as a ZST; [`Allocator`] functions do not operate on
+/// an object instance.
+///
+/// In order to be able to support `#[derive(SmartPointer)]` later on, we need to avoid a design
+/// that requires an `Allocator` to be instantiated, hence its functions must not contain any kind
+/// of `self` parameter.
+///
+/// # Safety
+///
+/// - A memory allocation returned from an allocator must remain valid until it is explicitly freed.
+///
+/// - Any pointer to a valid memory allocation must be valid to be passed to any other [`Allocator`]
+///   function of the same type.
+///
+/// - Implementers must ensure that all trait functions abide by the guarantees documented in the
+///   `# Guarantees` sections.
+pub unsafe trait Allocator {
+    /// Allocate memory based on `layout` and `flags`.
+    ///
+    /// On success, returns a buffer represented as `NonNull<[u8]>` that satisfies the layout
+    /// constraints (i.e. minimum size and alignment as specified by `layout`).
+    ///
+    /// This function is equivalent to `realloc` when called with `None`.
+    ///
+    /// # Guarantees
+    ///
+    /// When the return value is `Ok(ptr)`, then `ptr` is
+    /// - valid for reads and writes for `layout.size()` bytes, until it is passed to
+    ///   [`Allocator::free`] or [`Allocator::realloc`],
+    /// - aligned to `layout.align()`,
+    ///
+    /// Additionally, `Flags` are honored as documented in
+    /// <https://docs.kernel.org/core-api/mm-api.html#mm-api-gfp-flags>.
+    fn alloc(layout: Layout, flags: Flags) -> Result<NonNull<[u8]>, AllocError> {
+        // SAFETY: Passing `None` to `realloc` is valid by its safety requirements and asks for a
+        // new memory allocation.
+        unsafe { Self::realloc(None, layout, Layout::new::<()>(), flags) }
+    }
+
+    /// Re-allocate an existing memory allocation to satisfy the requested `layout`.
+    ///
+    /// If the requested size is zero, `realloc` behaves equivalent to `free`.
+    ///
+    /// If the requested size is larger than the size of the existing allocation, a successful call
+    /// to `realloc` guarantees that the new or grown buffer has at least `Layout::size` bytes, but
+    /// may also be larger.
+    ///
+    /// If the requested size is smaller than the size of the existing allocation, `realloc` may or
+    /// may not shrink the buffer; this is implementation specific to the allocator.
+    ///
+    /// On allocation failure, the existing buffer, if any, remains valid.
+    ///
+    /// The buffer is represented as `NonNull<[u8]>`.
+    ///
+    /// # Safety
+    ///
+    /// - If `ptr == Some(p)`, then `p` must point to an existing and valid memory allocation
+    ///   created by this [`Allocator`]; if `old_layout` is zero-sized `p` does not need to be a
+    ///   pointer returned by this [`Allocator`].
+    /// - `ptr` is allowed to be `None`; in this case a new memory allocation is created and
+    ///   `old_layout` is ignored.
+    /// - `old_layout` must match the `Layout` the allocation has been created with.
+    ///
+    /// # Guarantees
+    ///
+    /// This function has the same guarantees as [`Allocator::alloc`]. When `ptr == Some(p)`, then
+    /// it additionally guarantees that:
+    /// - the contents of the memory pointed to by `p` are preserved up to the lesser of the new
+    ///   and old size, i.e. `ret_ptr[0..min(layout.size(), old_layout.size())] ==
+    ///   p[0..min(layout.size(), old_layout.size())]`.
+    /// - when the return value is `Err(AllocError)`, then `ptr` is still valid.
+    unsafe fn realloc(
+        ptr: Option<NonNull<u8>>,
+        layout: Layout,
+        old_layout: Layout,
+        flags: Flags,
+    ) -> Result<NonNull<[u8]>, AllocError>;
+
+    /// Free an existing memory allocation.
+    ///
+    /// # Safety
+    ///
+    /// - `ptr` must point to an existing and valid memory allocation created by this [`Allocator`];
+    ///   if `old_layout` is zero-sized `p` does not need to be a pointer returned by this
+    ///   [`Allocator`].
+    /// - `layout` must match the `Layout` the allocation has been created with.
+    /// - The memory allocation at `ptr` must never again be read from or written to.
+    unsafe fn free(ptr: NonNull<u8>, layout: Layout) {
+        // SAFETY: The caller guarantees that `ptr` points at a valid allocation created by this
+        // allocator. We are passing a `Layout` with the smallest possible alignment, so it is
+        // smaller than or equal to the alignment previously used with this allocation.
+        let _ = unsafe { Self::realloc(Some(ptr), Layout::new::<()>(), layout, Flags(0)) };
+    }
+}
+
+/// Returns a properly aligned dangling pointer from the given `layout`.
+pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull<u8> {
+    let ptr = layout.align() as *mut u8;
+
+    // SAFETY: `layout.align()` (and hence `ptr`) is guaranteed to be non-zero.
+    unsafe { NonNull::new_unchecked(ptr) }
 }