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rust: types: implement ForeignOwnable for Box<T>

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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@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>
This commit is contained in:
Wedson Almeida Filho 2023-01-30 03:44:02 -03:00 committed by Miguel Ojeda
parent 0fc4424d24
commit 26949bac1e
1 changed files with 23 additions and 0 deletions
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23
rust/kernel/types.rs
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@ -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.