| Message ID | 20240309235927.168915-3-mcanal@igalia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | rust: xarray: Add an abstraction for XArray | expand |
On 3/10/24 00:57, Maíra Canal wrote: > There are cases where we need to check the alignment of the pointers > returned by `into_foreign`. Currently, this is not possible to be done > at build time. Therefore, add a property to the trait ForeignOwnable, > which specifies the alignment of the pointers returned by > `into_foreign`. > > Suggested-by: Alice Ryhl <aliceryhl@google.com> > Signed-off-by: Maíra Canal <mcanal@igalia.com> > Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com> > Reviewed-by: Alice Ryhl <aliceryhl@google.com> > --- > rust/kernel/sync/arc.rs | 2 ++ > rust/kernel/types.rs | 7 +++++++ > 2 files changed, 9 insertions(+) > > diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs > index 7d4c4bf58388..da5c8cc325b6 100644 > --- a/rust/kernel/sync/arc.rs > +++ b/rust/kernel/sync/arc.rs > @@ -274,6 +274,8 @@ pub fn ptr_eq(this: &Self, other: &Self) -> bool { > } > > impl<T: 'static> ForeignOwnable for Arc<T> { > + const FOREIGN_ALIGN: usize = core::mem::align_of::<ArcInner<T>>(); > + > type Borrowed<'a> = ArcBorrow<'a, T>; > > fn into_foreign(self) -> *const core::ffi::c_void { > diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs > index aa77bad9bce4..76cd4226dd35 100644 > --- a/rust/kernel/types.rs > +++ b/rust/kernel/types.rs > @@ -20,6 +20,9 @@ > /// This trait is meant to be used in cases when Rust objects are stored in C objects and > /// eventually "freed" back to Rust. > pub trait ForeignOwnable: Sized { > + /// The alignment of pointers returned by `into_foreign`. > + const FOREIGN_ALIGN: usize; > + I think we need to make the trait `unsafe`, since we want `unsafe` code to be able to rely on this value being correct.
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index 7d4c4bf58388..da5c8cc325b6 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -274,6 +274,8 @@ pub fn ptr_eq(this: &Self, other: &Self) -> bool { } impl<T: 'static> ForeignOwnable for Arc<T> { + const FOREIGN_ALIGN: usize = core::mem::align_of::<ArcInner<T>>(); + type Borrowed<'a> = ArcBorrow<'a, T>; fn into_foreign(self) -> *const core::ffi::c_void { diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index aa77bad9bce4..76cd4226dd35 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -20,6 +20,9 @@ /// This trait is meant to be used in cases when Rust objects are stored in C objects and /// eventually "freed" back to Rust. pub trait ForeignOwnable: Sized { + /// The alignment of pointers returned by `into_foreign`. + const FOREIGN_ALIGN: usize; + /// Type of values borrowed between calls to [`ForeignOwnable::into_foreign`] and /// [`ForeignOwnable::from_foreign`]. type Borrowed<'a>; @@ -68,6 +71,8 @@ unsafe fn try_from_foreign(ptr: *const core::ffi::c_void) -> Option<Self> { } impl<T: 'static> ForeignOwnable for Box<T> { + const FOREIGN_ALIGN: usize = core::mem::align_of::<T>(); + type Borrowed<'a> = &'a T; fn into_foreign(self) -> *const core::ffi::c_void { @@ -90,6 +95,8 @@ unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self { } impl ForeignOwnable for () { + const FOREIGN_ALIGN: usize = core::mem::align_of::<()>(); + type Borrowed<'a> = (); fn into_foreign(self) -> *const core::ffi::c_void {