// SPDX-License-Identifier: GPL-2.0 //! Kernel types. use crate::ffi::c_void;use core::{    cell::UnsafeCell,    marker::{PhantomData, PhantomPinned},    mem::MaybeUninit,    ops::{Deref, DerefMut},};use pin_init::{PinInit, Wrapper, Zeroable}; /// Used to transfer ownership to and from foreign (non-Rust) languages.////// Ownership is transferred from Rust to a foreign language by calling [`Self::into_foreign`] and/// later may be transferred back to Rust by calling [`Self::from_foreign`].////// This trait is meant to be used in cases when Rust objects are stored in C objects and/// eventually "freed" back to Rust.////// # Safety////// - Implementations must satisfy the guarantees of [`Self::into_foreign`].pub unsafe trait ForeignOwnable: Sized {    /// The alignment of pointers returned by `into_foreign`.    const FOREIGN_ALIGN: usize;     /// Type used to immutably borrow a value that is currently foreign-owned.    type Borrowed<'a>;     /// Type used to mutably borrow a value that is currently foreign-owned.    type BorrowedMut<'a>;     /// Converts a Rust-owned object to a foreign-owned one.    ///    /// The foreign representation is a pointer to void. Aside from the guarantees listed below,    /// there are no other guarantees for this pointer. For example, it might be invalid, dangling    /// or pointing to uninitialized memory. Using it in any way except for [`from_foreign`],    /// [`try_from_foreign`], [`borrow`], or [`borrow_mut`] can result in undefined behavior.    ///    /// # Guarantees    ///    /// - Minimum alignment of returned pointer is [`Self::FOREIGN_ALIGN`].    /// - The returned pointer is not null.    ///    /// [`from_foreign`]: Self::from_foreign    /// [`try_from_foreign`]: Self::try_from_foreign    /// [`borrow`]: Self::borrow    /// [`borrow_mut`]: Self::borrow_mut    fn into_foreign(self) -> *mut c_void;     /// Converts a foreign-owned object back to a Rust-owned one.    ///    /// # Safety    ///    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and it    /// must not be passed to `from_foreign` more than once.    ///    /// [`into_foreign`]: Self::into_foreign    unsafe fn from_foreign(ptr: *mut c_void) -> Self;     /// Tries to convert a foreign-owned object back to a Rust-owned one.    ///    /// A convenience wrapper over [`ForeignOwnable::from_foreign`] that returns [`None`] if `ptr`    /// is null.    ///    /// # Safety    ///    /// `ptr` must either be null or satisfy the safety requirements for [`from_foreign`].    ///    /// [`from_foreign`]: Self::from_foreign    unsafe fn try_from_foreign(ptr: *mut c_void) -> Option<Self> {        if ptr.is_null() {            None        } else {            // SAFETY: Since `ptr` is not null here, then `ptr` satisfies the safety requirements            // of `from_foreign` given the safety requirements of this function.            unsafe { Some(Self::from_foreign(ptr)) }        }    }     /// Borrows a foreign-owned object immutably.    ///    /// This method provides a way to access a foreign-owned value from Rust immutably. It provides    /// you with exactly the same abilities as an `&Self` when the value is Rust-owned.    ///    /// # Safety    ///    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and if    /// the pointer is ever passed to [`from_foreign`], then that call must happen after the end of    /// the lifetime `'a`.    ///    /// [`into_foreign`]: Self::into_foreign    /// [`from_foreign`]: Self::from_foreign    unsafe fn borrow<'a>(ptr: *mut c_void) -> Self::Borrowed<'a>;     /// Borrows a foreign-owned object mutably.    ///    /// This method provides a way to access a foreign-owned value from Rust mutably. It provides    /// you with exactly the same abilities as an `&mut Self` when the value is Rust-owned, except    /// that the address of the object must not be changed.    ///    /// Note that for types like [`Arc`], an `&mut Arc<T>` only gives you immutable access to the    /// inner value, so this method also only provides immutable access in that case.    ///    /// In the case of `Box<T>`, this method gives you the ability to modify the inner `T`, but it    /// does not let you change the box itself. That is, you cannot change which allocation the box    /// points at.    ///    /// # Safety    ///    /// The provided pointer must have been returned by a previous call to [`into_foreign`], and if    /// the pointer is ever passed to [`from_foreign`], then that call must happen after the end of    /// the lifetime `'a`.    ///    /// The lifetime `'a` must not overlap with the lifetime of any other call to [`borrow`] or    /// `borrow_mut` on the same object.    ///    /// [`into_foreign`]: Self::into_foreign    /// [`from_foreign`]: Self::from_foreign    /// [`borrow`]: Self::borrow    /// [`Arc`]: crate::sync::Arc    unsafe fn borrow_mut<'a>(ptr: *mut c_void) -> Self::BorrowedMut<'a>;} // SAFETY: The pointer returned by `into_foreign` comes from a well aligned// pointer to `()`.unsafe impl ForeignOwnable for () {    const FOREIGN_ALIGN: usize = core::mem::align_of::<()>();    type Borrowed<'a> = ();    type BorrowedMut<'a> = ();     fn into_foreign(self) -> *mut c_void {        core::ptr::NonNull::dangling().as_ptr()    }     unsafe fn from_foreign(_: *mut c_void) -> Self {}     unsafe fn borrow<'a>(_: *mut c_void) -> Self::Borrowed<'a> {}    unsafe fn borrow_mut<'a>(_: *mut c_void) -> Self::BorrowedMut<'a> {}} /// Runs a cleanup function/closure when dropped.////// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.////// # Examples////// In the example below, we have multiple exit paths and we want to log regardless of which one is/// taken:////// ```/// # use kernel::types::ScopeGuard;/// fn example1(arg: bool) {///     let _log = ScopeGuard::new(|| pr_info!("example1 completed\n"));//////     if arg {///         return;///     }//////     pr_info!("Do something...\n");/// }////// # example1(false);/// # example1(true);/// ```////// In the example below, we want to log the same message on all early exits but a different one on/// the main exit path:////// ```/// # use kernel::types::ScopeGuard;/// fn example2(arg: bool) {///     let log = ScopeGuard::new(|| pr_info!("example2 returned early\n"));//////     if arg {///         return;///     }//////     // (Other early returns...)//////     log.dismiss();///     pr_info!("example2 no early return\n");/// }////// # example2(false);/// # example2(true);/// ```////// In the example below, we need a mutable object (the vector) to be accessible within the log/// function, so we wrap it in the [`ScopeGuard`]:////// ```/// # use kernel::types::ScopeGuard;/// fn example3(arg: bool) -> Result {///     let mut vec =///         ScopeGuard::new_with_data(KVec::new(), |v| pr_info!("vec had {} elements\n", v.len()));//////     vec.push(10u8, GFP_KERNEL)?;///     if arg {///         return Ok(());///     }///     vec.push(20u8, GFP_KERNEL)?;///     Ok(())/// }////// # assert_eq!(example3(false), Ok(()));/// # assert_eq!(example3(true), Ok(()));/// ```////// # Invariants////// The value stored in the struct is nearly always `Some(_)`, except between/// [`ScopeGuard::dismiss`] and [`ScopeGuard::drop`]: in this case, it will be `None` as the value/// will have been returned to the caller. Since  [`ScopeGuard::dismiss`] consumes the guard,/// callers won't be able to use it anymore.pub struct ScopeGuard<T, F: FnOnce(T)>(Option<(T, F)>); impl<T, F: FnOnce(T)> ScopeGuard<T, F> {    /// Creates a new guarded object wrapping the given data and with the given cleanup function.    pub fn new_with_data(data: T, cleanup_func: F) -> Self {        // INVARIANT: The struct is being initialised with `Some(_)`.        Self(Some((data, cleanup_func)))    }     /// Prevents the cleanup function from running and returns the guarded data.    pub fn dismiss(mut self) -> T {        // INVARIANT: This is the exception case in the invariant; it is not visible to callers        // because this function consumes `self`.        self.0.take().unwrap().0    }} impl ScopeGuard<(), fn(())> {    /// Creates a new guarded object with the given cleanup function.    pub fn new(cleanup: impl FnOnce()) -> ScopeGuard<(), impl FnOnce(())> {        ScopeGuard::new_with_data((), move |()| cleanup())    }} impl<T, F: FnOnce(T)> Deref for ScopeGuard<T, F> {    type Target = T;     fn deref(&self) -> &T {        // The type invariants guarantee that `unwrap` will succeed.        &self.0.as_ref().unwrap().0    }} impl<T, F: FnOnce(T)> DerefMut for ScopeGuard<T, F> {    fn deref_mut(&mut self) -> &mut T {        // The type invariants guarantee that `unwrap` will succeed.        &mut self.0.as_mut().unwrap().0    }} impl<T, F: FnOnce(T)> Drop for ScopeGuard<T, F> {    fn drop(&mut self) {        // Run the cleanup function if one is still present.        if let Some((data, cleanup)) = self.0.take() {            cleanup(data)        }    }} /// Stores an opaque value.////// [`Opaque<T>`] is meant to be used with FFI objects that are never interpreted by Rust code.////// It is used to wrap structs from the C side, like for example `Opaque<bindings::mutex>`./// It gets rid of all the usual assumptions that Rust has for a value:////// * The value is allowed to be uninitialized (for example have invalid bit patterns: `3` for a///   [`bool`])./// * The value is allowed to be mutated, when a `&Opaque<T>` exists on the Rust side./// * No uniqueness for mutable references: it is fine to have multiple `&mut Opaque<T>` point to///   the same value./// * The value is not allowed to be shared with other threads (i.e. it is `!Sync`).////// This has to be used for all values that the C side has access to, because it can't be ensured/// that the C side is adhering to the usual constraints that Rust needs.////// Using [`Opaque<T>`] allows to continue to use references on the Rust side even for values shared/// with C.////// # Examples////// ```/// use kernel::types::Opaque;/// # // Emulate a C struct binding which is from C, maybe uninitialized or not, only the C side/// # // knows./// # mod bindings {/// #     pub struct Foo {/// #         pub val: u8,/// #     }/// # }////// // `foo.val` is assumed to be handled on the C side, so we use `Opaque` to wrap it./// pub struct Foo {///     foo: Opaque<bindings::Foo>,/// }////// impl Foo {///     pub fn get_val(&self) -> u8 {///         let ptr = Opaque::get(&self.foo);//////         // SAFETY: `Self` is valid from C side.///         unsafe { (*ptr).val }///     }/// }////// // Create an instance of `Foo` with the `Opaque` wrapper./// let foo = Foo {///     foo: Opaque::new(bindings::Foo { val: 0xdb }),/// };////// assert_eq!(foo.get_val(), 0xdb);/// ```#[repr(transparent)]pub struct Opaque<T> {    value: UnsafeCell<MaybeUninit<T>>,    _pin: PhantomPinned,} // SAFETY: `Opaque<T>` allows the inner value to be any bit pattern, including all zeros.unsafe impl<T> Zeroable for Opaque<T> {} impl<T> Opaque<T> {    /// Creates a new opaque value.    pub const fn new(value: T) -> Self {        Self {            value: UnsafeCell::new(MaybeUninit::new(value)),            _pin: PhantomPinned,        }    }     /// Creates an uninitialised value.    pub const fn uninit() -> Self {        Self {            value: UnsafeCell::new(MaybeUninit::uninit()),            _pin: PhantomPinned,        }    }     /// Creates a new zeroed opaque value.    pub const fn zeroed() -> Self {        Self {            value: UnsafeCell::new(MaybeUninit::zeroed()),            _pin: PhantomPinned,        }    }     /// Creates a pin-initializer from the given initializer closure.    ///    /// The returned initializer calls the given closure with the pointer to the inner `T` of this    /// `Opaque`. Since this memory is uninitialized, the closure is not allowed to read from it.    ///    /// This function is safe, because the `T` inside of an `Opaque` is allowed to be    /// uninitialized. Additionally, access to the inner `T` requires `unsafe`, so the caller needs    /// to verify at that point that the inner value is valid.    pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> {        // SAFETY: We contain a `MaybeUninit`, so it is OK for the `init_func` to not fully        // initialize the `T`.        unsafe {            pin_init::pin_init_from_closure::<_, ::core::convert::Infallible>(move |slot| {                init_func(Self::cast_into(slot));                Ok(())            })        }    }     /// Creates a fallible pin-initializer from the given initializer closure.    ///    /// The returned initializer calls the given closure with the pointer to the inner `T` of this    /// `Opaque`. Since this memory is uninitialized, the closure is not allowed to read from it.    ///    /// This function is safe, because the `T` inside of an `Opaque` is allowed to be    /// uninitialized. Additionally, access to the inner `T` requires `unsafe`, so the caller needs    /// to verify at that point that the inner value is valid.    pub fn try_ffi_init<E>(        init_func: impl FnOnce(*mut T) -> Result<(), E>,    ) -> impl PinInit<Self, E> {        // SAFETY: We contain a `MaybeUninit`, so it is OK for the `init_func` to not fully        // initialize the `T`.        unsafe {            pin_init::pin_init_from_closure::<_, E>(move |slot| init_func(Self::cast_into(slot)))        }    }     /// Returns a raw pointer to the opaque data.    pub const fn get(&self) -> *mut T {        UnsafeCell::get(&self.value).cast::<T>()    }     /// Gets the value behind `this`.    ///    /// This function is useful to get access to the value without creating intermediate    /// references.    pub const fn cast_into(this: *const Self) -> *mut T {        UnsafeCell::raw_get(this.cast::<UnsafeCell<MaybeUninit<T>>>()).cast::<T>()    }     /// The opposite operation of [`Opaque::cast_into`].    pub const fn cast_from(this: *const T) -> *const Self {        this.cast()    }} impl<T> Wrapper<T> for Opaque<T> {    /// Create an opaque pin-initializer from the given pin-initializer.    fn pin_init<E>(slot: impl PinInit<T, E>) -> impl PinInit<Self, E> {        Self::try_ffi_init(|ptr: *mut T| {            // SAFETY:            //   - `ptr` is a valid pointer to uninitialized memory,            //   - `slot` is not accessed on error,            //   - `slot` is pinned in memory.            unsafe { PinInit::<T, E>::__pinned_init(slot, ptr) }        })    }} /// Zero-sized type to mark types not [`Send`].////// Add this type as a field to your struct if your type should not be sent to a different task./// Since [`Send`] is an auto trait, adding a single field that is `!Send` will ensure that the/// whole type is `!Send`.////// If a type is `!Send` it is impossible to give control over an instance of the type to another/// task. This is useful to include in types that store or reference task-local information. A file/// descriptor is an example of such task-local information.////// This type also makes the type `!Sync`, which prevents immutable access to the value from/// several threads in parallel.pub type NotThreadSafe = PhantomData<*mut ()>; /// Used to construct instances of type [`NotThreadSafe`] similar to how `PhantomData` is/// constructed.////// [`NotThreadSafe`]: type@NotThreadSafe#[allow(non_upper_case_globals)]pub const NotThreadSafe: NotThreadSafe = PhantomData;