rust/kernel/time/hrtimer/tbox.rs

Source file repositories/reference/linux-study-clean/rust/kernel/time/hrtimer/tbox.rs

File Facts

System
Linux kernel
Corpus path
rust/kernel/time/hrtimer/tbox.rs
Extension
.rs
Size
4411 bytes
Lines
132
Domain
Rust Kernel Layer
Bucket
Rust API Membrane
Inferred role
Rust Kernel Layer: implementation source
Status
source implementation candidate

Why This File Exists

Rust-side wrappers and abstractions around kernel C APIs, ownership contracts, allocation, synchronization, and module integration.

Dependency Surface

Detected Declarations

Annotated Snippet

fn drop(&mut self) {
        self.cancel();
        // SAFETY: By type invariant, `self.inner` came from a `Box::into_raw`
        // call.
        drop(unsafe { Box::<T, A>::from_raw(self.inner.as_ptr()) })
    }
}

impl<T, A> HrTimerPointer for Pin<Box<T, A>>
where
    T: 'static,
    T: Send + Sync,
    T: HasHrTimer<T>,
    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
    A: crate::alloc::Allocator,
{
    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
    type TimerHandle = BoxHrTimerHandle<T, A>;

    fn start(
        self,
        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
    ) -> Self::TimerHandle {
        // SAFETY:
        //  - We will not move out of this box during timer callback (we pass an
        //    immutable reference to the callback).
        //  - `Box::into_raw` is guaranteed to return a valid pointer.
        let inner =
            unsafe { NonNull::new_unchecked(Box::into_raw(Pin::into_inner_unchecked(self))) };

        // SAFETY:
        //  - We keep `self` alive by wrapping it in a handle below.
        //  - Since we generate the pointer passed to `start` from a valid
        //    reference, it is a valid pointer.
        unsafe { T::start(inner.as_ptr(), expires) };

        // INVARIANT: `inner` came from `Box::into_raw` above.
        BoxHrTimerHandle {
            inner,
            _p: core::marker::PhantomData,
        }
    }
}

impl<T, A> RawHrTimerCallback for Pin<Box<T, A>>
where
    T: 'static,
    T: HasHrTimer<T>,
    T: for<'a> HrTimerCallback<Pointer<'a> = Pin<Box<T, A>>>,
    A: crate::alloc::Allocator,
{
    type CallbackTarget<'a> = Pin<&'a mut T>;

    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
        // `HrTimer` is `repr(C)`
        let timer_ptr = ptr.cast::<super::HrTimer<T>>();

        // SAFETY: By C API contract `ptr` is the pointer we passed when
        // queuing the timer, so it is a `HrTimer<T>` embedded in a `T`.
        let data_ptr = unsafe { T::timer_container_of(timer_ptr) };

        // SAFETY:
        //  - As per the safety requirements of the trait `HrTimerHandle`, the
        //   `BoxHrTimerHandle` associated with this timer is guaranteed to
        //   be alive until this method returns. That handle owns the `T`
        //   behind `data_ptr` thus guaranteeing the validity of
        //   the reference created below.
        // - As `data_ptr` comes from a `Pin<Box<T>>`, only pinned references to
        //   `data_ptr` exist.
        let data_mut_ref = unsafe { Pin::new_unchecked(&mut *data_ptr) };

        // SAFETY:
        // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
        //   it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
        // - We are within `RawHrTimerCallback::run`
        let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };

        T::run(data_mut_ref, context).into_c()
    }
}

Annotation

Implementation Notes