Merge tag 'vfs-6.13.rust.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs rust file abstractions from Christian Brauner:
 "This contains the file abstractions needed by the Rust implementation
  of the Binder driver and other parts of the kernel.

  Let's treat this as a first attempt at getting something working but I
  do expect the actual interfaces to change significantly over time.
  Simply because we are still figuring out what actually works. But
  there's no point in further theorizing. Let's see how it holds up with
  actual users"

* tag 'vfs-6.13.rust.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  rust: task: adjust safety comments in Task methods
  rust: add seqfile abstraction
  rust: file: add abstraction for `poll_table`
  rust: file: add `Kuid` wrapper
  rust: file: add `FileDescriptorReservation`
  rust: security: add abstraction for secctx
  rust: cred: add Rust abstraction for `struct cred`
  rust: file: add Rust abstraction for `struct file`
  rust: task: add `Task::current_raw`
  rust: types: add `NotThreadSafe`

1 files changed, 21 insertions, 0 deletions

diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 9e7ca066355c..3238ffaab031 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -532,3 +532,24 @@ unsafe impl AsBytes for str {}
 // does not have any uninitialized portions either.
 unsafe impl<T: AsBytes> AsBytes for [T] {}
 unsafe impl<T: AsBytes, const N: usize> AsBytes for [T; N] {}
+
+/// Zero-sized type to mark types not [`Send`].
+///
+/// Add this type as a field to your struct if your type should not be sent to a different task.
+/// Since [`Send`] is an auto trait, adding a single field that is `!Send` will ensure that the
+/// whole type is `!Send`.
+///
+/// If a type is `!Send` it is impossible to give control over an instance of the type to another
+/// task. This is useful to include in types that store or reference task-local information. A file
+/// descriptor is an example of such task-local information.
+///
+/// This type also makes the type `!Sync`, which prevents immutable access to the value from
+/// several threads in parallel.
+pub type NotThreadSafe = PhantomData<*mut ()>;
+
+/// Used to construct instances of type [`NotThreadSafe`] similar to how `PhantomData` is
+/// constructed.
+///
+/// [`NotThreadSafe`]: type@NotThreadSafe
+#[allow(non_upper_case_globals)]
+pub const NotThreadSafe: NotThreadSafe = PhantomData;