diff options
Diffstat (limited to 'rust/kernel/init/__internal.rs')
-rw-r--r-- | rust/kernel/init/__internal.rs | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs index 774cb620afa7..44751fb62b51 100644 --- a/rust/kernel/init/__internal.rs +++ b/rust/kernel/init/__internal.rs @@ -112,6 +112,63 @@ unsafe impl<T: ?Sized> HasInitData for T { } } +/// Stack initializer helper type. Use [`stack_pin_init`] instead of this primitive. +/// +/// # Invariants +/// +/// If `self.is_init` is true, then `self.value` is initialized. +/// +/// [`stack_pin_init`]: kernel::stack_pin_init +pub struct StackInit<T> { + value: MaybeUninit<T>, + is_init: bool, +} + +impl<T> Drop for StackInit<T> { + #[inline] + fn drop(&mut self) { + if self.is_init { + // SAFETY: As we are being dropped, we only call this once. And since `self.is_init` is + // true, `self.value` is initialized. + unsafe { self.value.assume_init_drop() }; + } + } +} + +impl<T> StackInit<T> { + /// Creates a new [`StackInit<T>`] that is uninitialized. Use [`stack_pin_init`] instead of this + /// primitive. + /// + /// [`stack_pin_init`]: kernel::stack_pin_init + #[inline] + pub fn uninit() -> Self { + Self { + value: MaybeUninit::uninit(), + is_init: false, + } + } + + /// Initializes the contents and returns the result. + #[inline] + pub fn init<E>(self: Pin<&mut Self>, init: impl PinInit<T, E>) -> Result<Pin<&mut T>, E> { + // SAFETY: We never move out of `this`. + let this = unsafe { Pin::into_inner_unchecked(self) }; + // The value is currently initialized, so it needs to be dropped before we can reuse + // the memory (this is a safety guarantee of `Pin`). + if this.is_init { + this.is_init = false; + // SAFETY: `this.is_init` was true and therefore `this.value` is initialized. + unsafe { this.value.assume_init_drop() }; + } + // SAFETY: The memory slot is valid and this type ensures that it will stay pinned. + unsafe { init.__pinned_init(this.value.as_mut_ptr())? }; + // INVARIANT: `this.value` is initialized above. + this.is_init = true; + // SAFETY: The slot is now pinned, since we will never give access to `&mut T`. + Ok(unsafe { Pin::new_unchecked(this.value.assume_init_mut()) }) + } +} + /// When a value of this type is dropped, it drops a `T`. /// /// Can be forgotten to prevent the drop. |