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authorWedson Almeida Filho <wedsonaf@gmail.com>2023-01-30 09:44:04 +0300
committerMiguel Ojeda <ojeda@kernel.org>2023-02-07 13:24:24 +0300
commit0c7ae432576100ce3609bca0508b9fbcb686a5fe (patch)
tree364a93329a09347c14ec055d46bf2452a63505ea /rust
parent7118594466b8ed7285adb1dc177f2c84bfa33265 (diff)
downloadlinux-0c7ae432576100ce3609bca0508b9fbcb686a5fe.tar.xz
rust: types: implement `ForeignOwnable` for `Arc<T>`
This allows us to hand ownership of Rust ref-counted objects to the C side of the kernel. Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Reviewed-by: Gary Guo <gary@garyguo.net> Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com> Reviewed-by: Alice Ferrazzi <alice.ferrazzi@miraclelinux.com> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
Diffstat (limited to 'rust')
-rw-r--r--rust/kernel/sync/arc.rs32
1 files changed, 31 insertions, 1 deletions
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index ff73f9240ca1..f2f1c83d72ba 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -15,7 +15,11 @@
//!
//! [`Arc`]: https://doc.rust-lang.org/std/sync/struct.Arc.html
-use crate::{bindings, error::Result, types::Opaque};
+use crate::{
+ bindings,
+ error::Result,
+ types::{ForeignOwnable, Opaque},
+};
use alloc::boxed::Box;
use core::{
marker::{PhantomData, Unsize},
@@ -189,6 +193,32 @@ impl<T: ?Sized> Arc<T> {
}
}
+impl<T: 'static> ForeignOwnable for Arc<T> {
+ type Borrowed<'a> = ArcBorrow<'a, T>;
+
+ fn into_foreign(self) -> *const core::ffi::c_void {
+ ManuallyDrop::new(self).ptr.as_ptr() as _
+ }
+
+ unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> {
+ // SAFETY: By the safety requirement of this function, we know that `ptr` came from
+ // a previous call to `Arc::into_foreign`.
+ let inner = NonNull::new(ptr as *mut ArcInner<T>).unwrap();
+
+ // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive
+ // for the lifetime of the returned value. Additionally, the safety requirements of
+ // `ForeignOwnable::borrow_mut` ensure that no new mutable references are created.
+ unsafe { ArcBorrow::new(inner) }
+ }
+
+ unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self {
+ // 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
+ // holds a reference count increment that is transferrable to us.
+ unsafe { Self::from_inner(NonNull::new(ptr as _).unwrap()) }
+ }
+}
+
impl<T: ?Sized> Deref for Arc<T> {
type Target = T;