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FROMLIST: rust: task: add Task::current_raw

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Introduces a safe function for getting a raw pointer to the current
task.

When writing bindings that need to access the current task, it is often
more convenient to call a method that directly returns a raw pointer
than to use the existing `Task::current` method. However, the only way
to do that is `bindings::get_current()` which is unsafe since it calls
into C. By introducing `Task::current_raw()`, it becomes possible to
obtain a pointer to the current task without using unsafe.

Link: https://lore.kernel.org/all/CAH5fLgjT48X-zYtidv31mox3C4_Ogoo_2cBOCmX0Ang3tAgGHA@mail.gmail.com/
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

Bug: 324206405
Link: https://lore.kernel.org/all/20240209-alice-file-v5-2-a37886783025@google.com/
Change-Id: I7553f23ca973eeb13ee0b5ea92d55412393c8224
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
This commit is contained in:
Alice Ryhl 2024-01-11 16:44:15 +01:00 committed by Treehugger Robot
parent 6b4006d2d7
commit c8ae5646c9
1 changed files with 11 additions and 4 deletions
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15
rust/kernel/task.rs
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@ -97,6 +97,15 @@ unsafe impl Sync for Task {}
type Pid = bindings::pid_t; type Pid = bindings::pid_t;
impl Task { impl Task {
/// Returns a raw pointer to the current task.
///
/// It is up to the user to use the pointer correctly.
#[inline]
pub fn current_raw() -> *mut bindings::task_struct {
// SAFETY: Getting the current pointer is always safe.
unsafe { bindings::get_current() }
}
/// Returns a task reference for the currently executing task/thread. /// Returns a task reference for the currently executing task/thread.
/// ///
/// The recommended way to get the current task/thread is to use the /// The recommended way to get the current task/thread is to use the
@ -119,14 +128,12 @@ impl Task {
} }
} }
// SAFETY: Just an FFI call with no additional safety requirements. let current = Task::current_raw();
let ptr = unsafe { bindings::get_current() };
TaskRef { TaskRef {
// SAFETY: If the current thread is still running, the current task is valid. Given // SAFETY: If the current thread is still running, the current task is valid. Given
// that `TaskRef` is not `Send`, we know it cannot be transferred to another thread // that `TaskRef` is not `Send`, we know it cannot be transferred to another thread
// (where it could potentially outlive the caller). // (where it could potentially outlive the caller).
task: unsafe { &*ptr.cast() }, task: unsafe { &*current.cast() },
_not_send: NotThreadSafe, _not_send: NotThreadSafe,
} }
} }