6.5-stable review patch. If anyone has any objections, please let me know.
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From: Benno Lossin benno.lossin@proton.me
[ Upstream commit 0b4e3b6f6b79b1add04008a6ceaaf661107e8902 ]
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 Reviewed-by: Gary Guo gary@garyguo.net Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Andreas Hindborg a.hindborg@samsung.com Link: https://lore.kernel.org/r/20230630150216.109789-1-benno.lossin@proton.me Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 c0b8bb1a75393..50cbd767ea9dd 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, @@ -206,17 +206,26 @@ 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. @@ -240,7 +249,7 @@ 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`.