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rust: types: make Opaque
be !Unpin
[ Upstream commit 0b4e3b6f6b
]
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>
This commit is contained in:
parent
7fba72536e
commit
a58f5fabca
@ -6,7 +6,7 @@ use crate::init::{self, PinInit};
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use alloc::boxed::Box;
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use core::{
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cell::UnsafeCell,
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marker::PhantomData,
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marker::{PhantomData, PhantomPinned},
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mem::MaybeUninit,
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ops::{Deref, DerefMut},
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ptr::NonNull,
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@ -206,17 +206,26 @@ impl<T, F: FnOnce(T)> Drop for ScopeGuard<T, F> {
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///
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/// This is meant to be used with FFI objects that are never interpreted by Rust code.
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#[repr(transparent)]
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pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>);
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pub struct Opaque<T> {
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value: UnsafeCell<MaybeUninit<T>>,
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_pin: PhantomPinned,
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}
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impl<T> Opaque<T> {
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/// Creates a new opaque value.
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pub const fn new(value: T) -> Self {
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Self(UnsafeCell::new(MaybeUninit::new(value)))
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Self {
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value: UnsafeCell::new(MaybeUninit::new(value)),
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_pin: PhantomPinned,
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}
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}
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/// Creates an uninitialised value.
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pub const fn uninit() -> Self {
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Self(UnsafeCell::new(MaybeUninit::uninit()))
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Self {
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value: UnsafeCell::new(MaybeUninit::uninit()),
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_pin: PhantomPinned,
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}
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}
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/// Creates a pin-initializer from the given initializer closure.
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@ -240,7 +249,7 @@ impl<T> Opaque<T> {
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/// Returns a raw pointer to the opaque data.
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pub fn get(&self) -> *mut T {
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UnsafeCell::get(&self.0).cast::<T>()
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UnsafeCell::get(&self.value).cast::<T>()
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}
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/// Gets the value behind `this`.
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