Messages in this thread Patch in this message | | | Date | Fri, 30 Jun 2023 15:03:23 +0000 | From | Benno Lossin <> | Subject | [PATCH] rust: types: make `Opaque` be `!Unpin` |
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Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust guarantee: the assumption that the type `T` can be freely moved. This is not the case for many types from the C side (e.g. if they contain a `struct list_head`). This change removes the need to add a `PhantomPinned` field manually to Rust structs that contain C structs which must not be moved.
Signed-off-by: Benno Lossin <benno.lossin@proton.me> --- This patch depends on the patch that swaps `UnsafeCell` with `MaybeUninit` inside `Opaque` [1].
[1]: https://lore.kernel.org/rust-for-linux/20230614115328.2825961-1-aliceryhl@google.com/ --- rust/kernel/types.rs | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index fb41635f1e1f..e664a2beef30 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -6,7 +6,7 @@ use alloc::boxed::Box; use core::{ cell::UnsafeCell, - marker::PhantomData, + marker::{PhantomData, PhantomPinned}, mem::MaybeUninit, ops::{Deref, DerefMut}, ptr::NonNull, @@ -224,17 +224,26 @@ fn drop(&mut self) { /// /// This is meant to be used with FFI objects that are never interpreted by Rust code. #[repr(transparent)] -pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>); +pub struct Opaque<T> { + value: UnsafeCell<MaybeUninit<T>>, + _pin: PhantomPinned, +} impl<T> Opaque<T> { /// Creates a new opaque value. pub const fn new(value: T) -> Self { - Self(UnsafeCell::new(MaybeUninit::new(value))) + Self { + value: UnsafeCell::new(MaybeUninit::new(value)), + _pin: PhantomPinned, + } } /// Creates an uninitialised value. pub const fn uninit() -> Self { - Self(UnsafeCell::new(MaybeUninit::uninit())) + Self { + value: UnsafeCell::new(MaybeUninit::uninit()), + _pin: PhantomPinned, + } } /// Creates a pin-initializer from the given initializer closure. @@ -258,7 +267,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> { /// Returns a raw pointer to the opaque data. pub fn get(&self) -> *mut T { - UnsafeCell::get(&self.0).cast::<T>() + UnsafeCell::get(&self.value).cast::<T>() } /// Gets the value behind `this`. -- 2.41.0
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