1 files changed, 13 insertions, 11 deletions

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 499175f637a7..63a66761d0c7 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -19,6 +19,7 @@
 use crate::{
     alloc::{AllocError, Flags, KBox},
     bindings,
+    ffi::c_void,
     init::InPlaceInit,
     try_init,
     types::{ForeignOwnable, Opaque},
@@ -141,10 +142,9 @@ pub struct Arc<T: ?Sized> {
     _p: PhantomData<ArcInner<T>>,
 }
 
-#[doc(hidden)]
 #[pin_data]
 #[repr(C)]
-pub struct ArcInner<T: ?Sized> {
+struct ArcInner<T: ?Sized> {
     refcount: Opaque<bindings::refcount_t>,
     data: T,
 }
@@ -373,20 +373,22 @@ impl<T: ?Sized> Arc<T> {
     }
 }
 
-// SAFETY: The `into_foreign` function returns a pointer that is well-aligned.
+// SAFETY: The pointer returned by `into_foreign` comes from a well aligned
+// pointer to `ArcInner<T>`.
 unsafe impl<T: 'static> ForeignOwnable for Arc<T> {
-    type PointedTo = ArcInner<T>;
+    const FOREIGN_ALIGN: usize = core::mem::align_of::<ArcInner<T>>();
+
     type Borrowed<'a> = ArcBorrow<'a, T>;
     type BorrowedMut<'a> = Self::Borrowed<'a>;
 
-    fn into_foreign(self) -> *mut Self::PointedTo {
-        ManuallyDrop::new(self).ptr.as_ptr()
+    fn into_foreign(self) -> *mut c_void {
+        ManuallyDrop::new(self).ptr.as_ptr().cast()
     }
 
-    unsafe fn from_foreign(ptr: *mut Self::PointedTo) -> Self {
+    unsafe fn from_foreign(ptr: *mut c_void) -> Self {
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
-        let inner = unsafe { NonNull::new_unchecked(ptr) };
+        let inner = unsafe { NonNull::new_unchecked(ptr.cast::<ArcInner<T>>()) };
 
         // SAFETY: By the safety requirement of this function, we know that `ptr` came from
         // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and
@@ -394,17 +396,17 @@ unsafe impl<T: 'static> ForeignOwnable for Arc<T> {
         unsafe { Self::from_inner(inner) }
     }
 
-    unsafe fn borrow<'a>(ptr: *mut Self::PointedTo) -> ArcBorrow<'a, T> {
+    unsafe fn borrow<'a>(ptr: *mut c_void) -> ArcBorrow<'a, T> {
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
-        let inner = unsafe { NonNull::new_unchecked(ptr) };
+        let inner = unsafe { NonNull::new_unchecked(ptr.cast::<ArcInner<T>>()) };
 
         // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
         // for the lifetime of the returned value.
         unsafe { ArcBorrow::new(inner) }
     }
 
-    unsafe fn borrow_mut<'a>(ptr: *mut Self::PointedTo) -> ArcBorrow<'a, T> {
+    unsafe fn borrow_mut<'a>(ptr: *mut c_void) -> ArcBorrow<'a, T> {
         // SAFETY: The safety requirements for `borrow_mut` are a superset of the safety
         // requirements for `borrow`.
         unsafe { <Self as ForeignOwnable>::borrow(ptr) }