rust: kernel: change `ForeignOwnable` pointer to mut

It is slightly more convenient to operate on mut pointers, and this also
properly conveys the desired ownership semantics of the trait.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20241120-borrow-mut-v6-4-80dbadd00951@gmail.com
[ Reworded title slightly. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index 05dd45c4b604742fff859bec75eb45ebbb96c733..d811edbf9b3bbc595d9f8da77a1a5b77a46ca5a8 100644 (file)
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -355,17 +355,17 @@ where
 {
     type Borrowed<'a> = &'a T;
 
-    fn into_foreign(self) -> *const crate::ffi::c_void {
+    fn into_foreign(self) -> *mut crate::ffi::c_void {
         Box::into_raw(self).cast()
     }
 
-    unsafe fn from_foreign(ptr: *const crate::ffi::c_void) -> Self {
+    unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self {
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
-        unsafe { Box::from_raw(ptr.cast_mut().cast()) }
+        unsafe { Box::from_raw(ptr.cast()) }
     }
 
-    unsafe fn borrow<'a>(ptr: *const crate::ffi::c_void) -> &'a T {
+    unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> &'a T {
         // SAFETY: The safety requirements of this method ensure that the object remains alive and
         // immutable for the duration of 'a.
         unsafe { &*ptr.cast() }
@@ -378,18 +378,18 @@ where
 {
     type Borrowed<'a> = Pin<&'a T>;
 
-    fn into_foreign(self) -> *const crate::ffi::c_void {
+    fn into_foreign(self) -> *mut crate::ffi::c_void {
         // SAFETY: We are still treating the box as pinned.
         Box::into_raw(unsafe { Pin::into_inner_unchecked(self) }).cast()
     }
 
-    unsafe fn from_foreign(ptr: *const crate::ffi::c_void) -> Self {
+    unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self {
         // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous
         // call to `Self::into_foreign`.
-        unsafe { Pin::new_unchecked(Box::from_raw(ptr.cast_mut().cast())) }
+        unsafe { Pin::new_unchecked(Box::from_raw(ptr.cast())) }
     }
 
-    unsafe fn borrow<'a>(ptr: *const crate::ffi::c_void) -> Pin<&'a T> {
+    unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> Pin<&'a T> {
         // SAFETY: The safety requirements for this function ensure that the object is still alive,
         // so it is safe to dereference the raw pointer.
         // The safety requirements of `from_foreign` also ensure that the object remains alive for

diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs
index 9e1b9c0fae9d123f780f5541f42158a1889f1da1..b3a6cc50b240e9373a7d4e9959fabb42235a794f 100644 (file)
--- a/rust/kernel/miscdevice.rs
+++ b/rust/kernel/miscdevice.rs
@@ -189,7 +189,7 @@ unsafe extern "C" fn fops_open<T: MiscDevice>(
     };
 
     // SAFETY: The open call of a file owns the private data.
-    unsafe { (*file).private_data = ptr.into_foreign().cast_mut() };
+    unsafe { (*file).private_data = ptr.into_foreign() };
 
     0
 }

diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 93eac650146abb8f9b2420f80dbadf81d1f95437..fe334394c328e0ba65a984f52cc075e056b4f8a8 100644 (file)
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -345,24 +345,24 @@ impl<T: ?Sized> Arc<T> {
 impl<T: 'static> ForeignOwnable for Arc<T> {
     type Borrowed<'a> = ArcBorrow<'a, T>;
 
-    fn into_foreign(self) -> *const crate::ffi::c_void {
+    fn into_foreign(self) -> *mut crate::ffi::c_void {
         ManuallyDrop::new(self).ptr.as_ptr().cast()
     }
 
-    unsafe fn borrow<'a>(ptr: *const crate::ffi::c_void) -> ArcBorrow<'a, T> {
+    unsafe fn borrow<'a>(ptr: *mut crate::ffi::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.cast_mut().cast::<ArcInner<T>>()) };
+        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 from_foreign(ptr: *const crate::ffi::c_void) -> Self {
+    unsafe fn from_foreign(ptr: *mut crate::ffi::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.cast_mut().cast::<ArcInner<T>>()) };
+        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

diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 318d2140470a90568100f86fd8c6d8084031f556..f9b398ee31fd5303f0224995f51d314a0c4ecbf2 100644 (file)
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -29,7 +29,7 @@ pub trait ForeignOwnable: Sized {
     /// For example, it might be invalid, dangling or pointing to uninitialized memory. Using it in
     /// any way except for [`ForeignOwnable::from_foreign`], [`ForeignOwnable::borrow`],
     /// [`ForeignOwnable::try_from_foreign`] can result in undefined behavior.
-    fn into_foreign(self) -> *const crate::ffi::c_void;
+    fn into_foreign(self) -> *mut crate::ffi::c_void;
 
     /// Borrows a foreign-owned object.
     ///
@@ -37,7 +37,7 @@ pub trait ForeignOwnable: Sized {
     ///
     /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for
     /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
-    unsafe fn borrow<'a>(ptr: *const crate::ffi::c_void) -> Self::Borrowed<'a>;
+    unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> Self::Borrowed<'a>;
 
     /// Converts a foreign-owned object back to a Rust-owned one.
     ///
@@ -47,7 +47,7 @@ pub trait ForeignOwnable: Sized {
     /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet.
     /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] for
     /// this object must have been dropped.
-    unsafe fn from_foreign(ptr: *const crate::ffi::c_void) -> Self;
+    unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self;
 
     /// Tries to convert a foreign-owned object back to a Rust-owned one.
     ///
@@ -58,7 +58,7 @@ pub trait ForeignOwnable: Sized {
     ///
     /// `ptr` must either be null or satisfy the safety requirements for
     /// [`ForeignOwnable::from_foreign`].
-    unsafe fn try_from_foreign(ptr: *const crate::ffi::c_void) -> Option<Self> {
+    unsafe fn try_from_foreign(ptr: *mut crate::ffi::c_void) -> Option<Self> {
         if ptr.is_null() {
             None
         } else {
@@ -72,13 +72,13 @@ pub trait ForeignOwnable: Sized {
 impl ForeignOwnable for () {
     type Borrowed<'a> = ();
 
-    fn into_foreign(self) -> *const crate::ffi::c_void {
+    fn into_foreign(self) -> *mut crate::ffi::c_void {
         core::ptr::NonNull::dangling().as_ptr()
     }
 
-    unsafe fn borrow<'a>(_: *const crate::ffi::c_void) -> Self::Borrowed<'a> {}
+    unsafe fn borrow<'a>(_: *mut crate::ffi::c_void) -> Self::Borrowed<'a> {}
 
-    unsafe fn from_foreign(_: *const crate::ffi::c_void) -> Self {}
+    unsafe fn from_foreign(_: *mut crate::ffi::c_void) -> Self {}
 }
 
 /// Runs a cleanup function/closure when dropped.