Merge tag 'rust-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull Rust updates from Miguel Ojeda:
 "Toolchain and infrastructure:

   - Extract the 'pin-init' API from the 'kernel' crate and make it into
     a standalone crate.

     In order to do this, the contents are rearranged so that they can
     easily be kept in sync with the version maintained out-of-tree that
     other projects have started to use too (or plan to, like QEMU).

     This will reduce the maintenance burden for Benno, who will now
     have his own sub-tree, and will simplify future expected changes
     like the move to use 'syn' to simplify the implementation.

   - Add '#[test]'-like support based on KUnit.

     We already had doctests support based on KUnit, which takes the
     examples in our Rust documentation and runs them under KUnit.

     Now, we are adding the beginning of the support for "normal" tests,
     similar to those the '#[test]' tests in userspace Rust. For
     instance:

         #[kunit_tests(my_suite)]
         mod tests {
             #[test]
             fn my_test() {
                 assert_eq!(1 + 1, 2);
             }
         }

     Unlike with doctests, the 'assert*!'s do not map to the KUnit
     assertion APIs yet.

   - Check Rust signatures at compile time for functions called from C
     by name.

     In particular, introduce a new '#[export]' macro that can be placed
     in the Rust function definition. It will ensure that the function
     declaration on the C side matches the signature on the Rust
     function:

         #[export]
         pub unsafe extern "C" fn my_function(a: u8, b: i32) -> usize {
             // ...
         }

     The macro essentially forces the compiler to compare the types of
     the actual Rust function and the 'bindgen'-processed C signature.

     These cases are rare so far. In the future, we may consider
     introducing another tool, 'cbindgen', to generate C headers
     automatically. Even then, having these functions explicitly marked
     may be a good idea anyway.

   - Enable the 'raw_ref_op' Rust feature: it is already stable, and
     allows us to use the new '&raw' syntax, avoiding a couple macros.
     After everyone has migrated, we will disallow the macros.

   - Pass the correct target to 'bindgen' on Usermode Linux.

   - Fix 'rusttest' build in macOS.

  'kernel' crate:

   - New 'hrtimer' module: add support for setting up intrusive timers
     without allocating when starting the timer. Add support for
     'Pin<Box<_>>', 'Arc<_>', 'Pin<&_>' and 'Pin<&mut _>' as pointer
     types for use with timer callbacks. Add support for setting clock
     source and timer mode.

   - New 'dma' module: add a simple DMA coherent allocator abstraction
     and a test sample driver.

   - 'list' module: make the linked list 'Cursor' point between
     elements, rather than at an element, which is more convenient to us
     and allows for cursors to empty lists; and document it with
     examples of how to perform common operations with the provided
     methods.

   - 'str' module: implement a few traits for 'BStr' as well as the
     'strip_prefix()' method.

   - 'sync' module: add 'Arc::as_ptr'.

   - 'alloc' module: add 'Box::into_pin'.

   - 'error' module: extend the 'Result' documentation, including a few
     examples on different ways of handling errors, a warning about
     using methods that may panic, and links to external documentation.

  'macros' crate:

   - 'module' macro: add the 'authors' key to support multiple authors.
     The original key will be kept until everyone has migrated.

  Documentation:

   - Add error handling sections.

  MAINTAINERS:

   - Add Danilo Krummrich as reviewer of the Rust "subsystem".

   - Add 'RUST [PIN-INIT]' entry with Benno Lossin as maintainer. It has
     its own sub-tree.

   - Add sub-tree for 'RUST [ALLOC]'.

   - Add 'DMA MAPPING HELPERS DEVICE DRIVER API [RUST]' entry with
     Abdiel Janulgue as primary maintainer. It will go through the
     sub-tree of the 'RUST [ALLOC]' entry.

   - Add 'HIGH-RESOLUTION TIMERS [RUST]' entry with Andreas Hindborg as
     maintainer. It has its own sub-tree.

  And a few other cleanups and improvements"

* tag 'rust-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (71 commits)
  rust: dma: add `Send` implementation for `CoherentAllocation`
  rust: macros: fix `make rusttest` build on macOS
  rust: block: refactor to use `&raw mut`
  rust: enable `raw_ref_op` feature
  rust: uaccess: name the correct function
  rust: rbtree: fix comments referring to Box instead of KBox
  rust: hrtimer: add maintainer entry
  rust: hrtimer: add clocksource selection through `ClockId`
  rust: hrtimer: add `HrTimerMode`
  rust: hrtimer: implement `HrTimerPointer` for `Pin<Box<T>>`
  rust: alloc: add `Box::into_pin`
  rust: hrtimer: implement `UnsafeHrTimerPointer` for `Pin<&mut T>`
  rust: hrtimer: implement `UnsafeHrTimerPointer` for `Pin<&T>`
  rust: hrtimer: add `hrtimer::ScopedHrTimerPointer`
  rust: hrtimer: add `UnsafeHrTimerPointer`
  rust: hrtimer: allow timer restart from timer handler
  rust: str: implement `strip_prefix` for `BStr`
  rust: str: implement `AsRef<BStr>` for `[u8]` and `BStr`
  rust: str: implement `Index` for `BStr`
  rust: str: implement `PartialEq` for `BStr`
  ...

rust/kernel/sync/arc.rs

@@ -19,7 +19,7 @@
 use crate::{
     alloc::{AllocError, Flags, KBox},
     bindings,
-    init::{self, InPlaceInit, Init, PinInit},
+    init::InPlaceInit,
     try_init,
     types::{ForeignOwnable, Opaque},
 };
@@ -32,7 +32,7 @@ use core::{
     pin::Pin,
     ptr::NonNull,
 };
-use macros::pin_data;
+use pin_init::{self, pin_data, InPlaceWrite, Init, PinInit};
 
 mod std_vendor;
 
@@ -202,6 +202,26 @@ unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> {}
 // the reference count reaches zero and `T` is dropped.
 unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> {}
 
+impl<T> InPlaceInit<T> for Arc<T> {
+    type PinnedSelf = Self;
+
+    #[inline]
+    fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
+    where
+        E: From<AllocError>,
+    {
+        UniqueArc::try_pin_init(init, flags).map(|u| u.into())
+    }
+
+    #[inline]
+    fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
+    where
+        E: From<AllocError>,
+    {
+        UniqueArc::try_init(init, flags).map(|u| u.into())
+    }
+}
+
 impl<T> Arc<T> {
     /// Constructs a new reference counted instance of `T`.
     pub fn new(contents: T, flags: Flags) -> Result<Self, AllocError> {
@@ -246,6 +266,15 @@ impl<T: ?Sized> Arc<T> {
         unsafe { core::ptr::addr_of!((*ptr).data) }
     }
 
+    /// Return a raw pointer to the data in this arc.
+    pub fn as_ptr(this: &Self) -> *const T {
+        let ptr = this.ptr.as_ptr();
+
+        // SAFETY: As `ptr` points to a valid allocation of type `ArcInner`,
+        // field projection to `data`is within bounds of the allocation.
+        unsafe { core::ptr::addr_of!((*ptr).data) }
+    }
+
     /// Recreates an [`Arc`] instance previously deconstructed via [`Arc::into_raw`].
     ///
     /// # Safety
@@ -539,11 +568,11 @@ impl<T: ?Sized> ArcBorrow<'_, T> {
     }
 
     /// Creates an [`ArcBorrow`] to an [`Arc`] that has previously been deconstructed with
-    /// [`Arc::into_raw`].
+    /// [`Arc::into_raw`] or [`Arc::as_ptr`].
     ///
     /// # Safety
     ///
-    /// * The provided pointer must originate from a call to [`Arc::into_raw`].
+    /// * The provided pointer must originate from a call to [`Arc::into_raw`] or [`Arc::as_ptr`].
     /// * For the duration of the lifetime annotated on this `ArcBorrow`, the reference count must
     ///   not hit zero.
     /// * For the duration of the lifetime annotated on this `ArcBorrow`, there must not be a
@@ -659,6 +688,48 @@ pub struct UniqueArc<T: ?Sized> {
     inner: Arc<T>,
 }
 
+impl<T> InPlaceInit<T> for UniqueArc<T> {
+    type PinnedSelf = Pin<Self>;
+
+    #[inline]
+    fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
+    where
+        E: From<AllocError>,
+    {
+        UniqueArc::new_uninit(flags)?.write_pin_init(init)
+    }
+
+    #[inline]
+    fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
+    where
+        E: From<AllocError>,
+    {
+        UniqueArc::new_uninit(flags)?.write_init(init)
+    }
+}
+
+impl<T> InPlaceWrite<T> for UniqueArc<MaybeUninit<T>> {
+    type Initialized = UniqueArc<T>;
+
+    fn write_init<E>(mut self, init: impl Init<T, E>) -> Result<Self::Initialized, E> {
+        let slot = self.as_mut_ptr();
+        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+        // slot is valid.
+        unsafe { init.__init(slot)? };
+        // SAFETY: All fields have been initialized.
+        Ok(unsafe { self.assume_init() })
+    }
+
+    fn write_pin_init<E>(mut self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E> {
+        let slot = self.as_mut_ptr();
+        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
+        // slot is valid and will not be moved, because we pin it later.
+        unsafe { init.__pinned_init(slot)? };
+        // SAFETY: All fields have been initialized.
+        Ok(unsafe { self.assume_init() }.into())
+    }
+}
+
 impl<T> UniqueArc<T> {
     /// Tries to allocate a new [`UniqueArc`] instance.
     pub fn new(value: T, flags: Flags) -> Result<Self, AllocError> {
@@ -675,7 +746,7 @@ impl<T> UniqueArc<T> {
             try_init!(ArcInner {
                 // SAFETY: There are no safety requirements for this FFI call.
                 refcount: Opaque::new(unsafe { bindings::REFCOUNT_INIT(1) }),
-                data <- init::uninit::<T, AllocError>(),
+                data <- pin_init::uninit::<T, AllocError>(),
             }? AllocError),
             flags,
         )?;

rust/kernel/sync/condvar.rs

@@ -8,8 +8,6 @@
 use super::{lock::Backend, lock::Guard, LockClassKey};
 use crate::{
     ffi::{c_int, c_long},
-    init::PinInit,
-    pin_init,
     str::CStr,
     task::{
         MAX_SCHEDULE_TIMEOUT, TASK_FREEZABLE, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE,
@@ -18,7 +16,7 @@ use crate::{
     types::Opaque,
 };
 use core::{marker::PhantomPinned, pin::Pin, ptr};
-use macros::pin_data;
+use pin_init::{pin_data, pin_init, PinInit};
 
 /// Creates a [`CondVar`] initialiser with the given name and a newly-created lock class.
 #[macro_export]
@@ -38,7 +36,7 @@ pub use new_condvar;
 /// spuriously.
 ///
 /// Instances of [`CondVar`] need a lock class and to be pinned. The recommended way to create such
-/// instances is with the [`pin_init`](crate::pin_init) and [`new_condvar`] macros.
+/// instances is with the [`pin_init`](crate::pin_init!) and [`new_condvar`] macros.
 ///
 /// # Examples
 ///

rust/kernel/sync/lock.rs

@@ -7,13 +7,11 @@
 
 use super::LockClassKey;
 use crate::{
-    init::PinInit,
-    pin_init,
     str::CStr,
     types::{NotThreadSafe, Opaque, ScopeGuard},
 };
 use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
-use macros::pin_data;
+use pin_init::{pin_data, pin_init, PinInit};
 
 pub mod mutex;
 pub mod spinlock;
@@ -208,7 +206,8 @@ impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
     /// lock is held.
     ///
     /// ```
-    /// # use kernel::{new_spinlock, stack_pin_init, sync::lock::{Backend, Guard, Lock}};
+    /// # use kernel::{new_spinlock, sync::lock::{Backend, Guard, Lock}};
+    /// # use pin_init::stack_pin_init;
     ///
     /// fn assert_held<T, B: Backend>(guard: &Guard<'_, T, B>, lock: &Lock<T, B>) {
     ///     // Address-equal means the same lock.

rust/kernel/sync/lock/mutex.rs

@@ -26,7 +26,7 @@ pub use new_mutex;
 /// Since it may block, [`Mutex`] needs to be used with care in atomic contexts.
 ///
 /// Instances of [`Mutex`] need a lock class and to be pinned. The recommended way to create such
-/// instances is with the [`pin_init`](crate::pin_init) and [`new_mutex`] macros.
+/// instances is with the [`pin_init`](pin_init::pin_init) and [`new_mutex`] macros.
 ///
 /// # Examples
 ///

rust/kernel/sync/lock/spinlock.rs

@@ -24,7 +24,7 @@ pub use new_spinlock;
 /// unlocked, at which point another CPU will be allowed to make progress.
 ///
 /// Instances of [`SpinLock`] need a lock class and to be pinned. The recommended way to create such
-/// instances is with the [`pin_init`](crate::pin_init) and [`new_spinlock`] macros.
+/// instances is with the [`pin_init`](pin_init::pin_init) and [`new_spinlock`] macros.
 ///
 /// # Examples
 ///

rust/kernel/sync/poll.rs

@@ -43,11 +43,11 @@ impl PollTable {
     ///
     /// # Safety
     ///
-    /// The caller must ensure that for the duration of 'a, the pointer will point at a valid poll
+    /// The caller must ensure that for the duration of `'a`, the pointer will point at a valid poll
     /// table (as defined in the type invariants).
     ///
     /// The caller must also ensure that the `poll_table` is only accessed via the returned
-    /// reference for the duration of 'a.
+    /// reference for the duration of `'a`.
     pub unsafe fn from_ptr<'a>(ptr: *mut bindings::poll_table) -> &'a mut PollTable {
         // SAFETY: The safety requirements guarantee the validity of the dereference, while the
         // `PollTable` type being transparent makes the cast ok.