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This allows use of `Owned` = in > places such as the `XArray`. > > Note that `T` does not need to implement `ForeignOwnable` for `Owned` = to > implement `ForeignOwnable`. > > Signed-off-by: Andreas Hindborg > --- > rust/kernel/owned.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++= ++++++ > 1 file changed, 53 insertions(+) > > diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs > index 7fe9ec3e55126..9c92d4a83cc1b 100644 > --- a/rust/kernel/owned.rs > +++ b/rust/kernel/owned.rs > @@ -15,6 +15,8 @@ > ptr::NonNull, // > }; > =20 > +use kernel::types::ForeignOwnable; > + > /// Types that specify their own way of performing allocation and destru= ction. Typically, this trait > /// is implemented on types from the C side. > /// > @@ -186,3 +188,54 @@ fn drop(&mut self) { > unsafe { T::release(self.ptr) }; > } > } > + > +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returne= d > +// pointer satisfy alignment requirements of `T`. > +unsafe impl ForeignOwnable for Owned { > + const FOREIGN_ALIGN: usize =3D core::mem::align_of::(); > + > + type Borrowed<'a> > + =3D &'a T > + where > + Self: 'a; > + type BorrowedMut<'a> > + =3D Pin<&'a mut T> > + where > + Self: 'a; > + > + #[inline] > + fn into_foreign(self) -> *mut kernel::ffi::c_void { > + let ptr =3D self.ptr.as_ptr().cast(); > + core::mem::forget(self); > + ptr I think the pattern in `into_raw` is better: ManuallyDrop::new(self).ptr.as_ptr().cast() Or perhaps this can just use `Self::into_raw(self).as_ptr().cast()`. > + } > + > + #[inline] > + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self { > + // INVARIANT: By the function safety contract, `ptr` was returne= d by `into_foreign`, which > + // gave up exclusive ownership of a valid, pinned `T`; we retake= that ownership here. > + Self { > + // SAFETY: By function safety contract, `ptr` came from > + // `into_foreign` and cannot be null. > + ptr: unsafe { NonNull::new_unchecked(ptr.cast()) }, > + } > + } Same here, could be using `Self::from_raw`. However, the current code looks correct to me regardless, so: Reviewed-by: Gary Guo Best, Gary > + > + #[inline] > + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowe= d<'a> { > + // SAFETY: By function safety requirements, `ptr` is valid for u= se as a > + // reference for `'a`. > + unsafe { &*ptr.cast() } > + } > + > + #[inline] > + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Bor= rowedMut<'a> { > + // SAFETY: By function safety requirements, `ptr` is valid for u= se as a > + // unique reference for `'a`. > + let inner =3D unsafe { &mut *ptr.cast() }; > + > + // SAFETY: We never move out of inner, and we do not hand out mu= table > + // references when `T: !Unpin`. > + unsafe { Pin::new_unchecked(inner) } > + } > +}