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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>
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>
This commit is contained in:
Benno Lossin 2023-06-30 15:03:23 +00:00 committed by Miguel Ojeda
parent 35cad617df
commit 0b4e3b6f6b
1 changed files with 14 additions and 5 deletions
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19
rust/kernel/types.rs
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@ -6,7 +6,7 @@
use alloc::boxed::Box; use alloc::boxed::Box;
use core::{ use core::{
cell::UnsafeCell, cell::UnsafeCell,
marker::PhantomData, marker::{PhantomData, PhantomPinned},
mem::MaybeUninit, mem::MaybeUninit,
ops::{Deref, DerefMut}, ops::{Deref, DerefMut},
ptr::NonNull, 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. /// This is meant to be used with FFI objects that are never interpreted by Rust code.
#[repr(transparent)] #[repr(transparent)]
pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>); pub struct Opaque<T> {
value: UnsafeCell<MaybeUninit<T>>,
_pin: PhantomPinned,
}
impl<T> Opaque<T> { impl<T> Opaque<T> {
/// Creates a new opaque value. /// Creates a new opaque value.
pub const fn new(value: T) -> Self { 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. /// Creates an uninitialised value.
pub const fn uninit() -> Self { 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. /// 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. /// Returns a raw pointer to the opaque data.
pub fn get(&self) -> *mut T { pub fn get(&self) -> *mut T {
UnsafeCell::get(&self.0).cast::<T>() UnsafeCell::get(&self.value).cast::<T>()
} }
/// Gets the value behind `this`. /// Gets the value behind `this`.