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Message-Id: <20230130064404.744600-3-wedsonaf@gmail.com>
Date: Mon, 30 Jan 2023 03:44:02 -0300
From: Wedson Almeida Filho <wedsonaf@...il.com>
To: rust-for-linux@...r.kernel.org
Cc: Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
linux-kernel@...r.kernel.org,
Wedson Almeida Filho <wedsonaf@...il.com>,
Vincenzo Palazzo <vincenzopalazzodev@...il.com>,
Alice Ferrazzi <alice.ferrazzi@...aclelinux.com>
Subject: [PATCH v2 3/5] rust: types: implement `ForeignOwnable` for `Box<T>`
This allows us to hand ownership of Rust dynamically allocated
objects to the C side of the kernel.
Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>
Reviewed-by: Gary Guo <gary@...yguo.net>
Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@...il.com>
Reviewed-by: Alice Ferrazzi <alice.ferrazzi@...aclelinux.com>
---
v1 -> v2: Add `use alloc::boxed::Box`, which wasn't needed before
rust/kernel/types.rs | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 72710b7442a3..411655eca3e9 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -2,6 +2,7 @@
//! Kernel types.
+use alloc::boxed::Box;
use core::{
cell::UnsafeCell,
mem::MaybeUninit,
@@ -62,6 +63,28 @@ pub trait ForeignOwnable: Sized {
unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self;
}
+impl<T: 'static> ForeignOwnable for Box<T> {
+ type Borrowed<'a> = &'a T;
+
+ fn into_foreign(self) -> *const core::ffi::c_void {
+ Box::into_raw(self) as _
+ }
+
+ unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> &'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
+ // the lifetime of the returned value.
+ unsafe { &*ptr.cast() }
+ }
+
+ unsafe fn from_foreign(ptr: *const core::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 as _) }
+ }
+}
+
/// Runs a cleanup function/closure when dropped.
///
/// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.
--
2.34.1
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