Commit 0b4e3b6f authored by Benno Lossin's avatar Benno Lossin Committed by Miguel Ojeda
Browse files

rust: types: make `Opaque` be `!Unpin` 



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: default avatarBenno Lossin <benno.lossin@proton.me>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarAndreas Hindborg <a.hindborg@samsung.com>
Link: https://lore.kernel.org/r/20230630150216.109789-1-benno.lossin@proton.me


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 35cad617

rust/kernel/types.rs

+14 −5
Original line number Diff line number Diff line
@@ -6,7 +6,7 @@ use crate::init::{self, PinInit}; 
use alloc::boxed::Box;

use core::{

    cell::UnsafeCell,

    marker::PhantomData,

    marker::{PhantomData, PhantomPinned},

    mem::MaybeUninit,

    ops::{Deref, DerefMut},

    ptr::NonNull,
@@ -206,17 +206,26 @@ impl<T, F: FnOnce(T)> Drop for ScopeGuard<T, F> { 
///

/// 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 @@ impl<T> Opaque<T> { 


    /// 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`.