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-rw-r--r--rust/kernel/init.rs111
-rw-r--r--rust/kernel/init/__internal.rs15
-rw-r--r--rust/kernel/init/macros.rs264
3 files changed, 390 insertions, 0 deletions
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 6499cf5c9c20..37e8159df24d 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -104,6 +104,78 @@
//! }
//! ```
//!
+//! ## Manual creation of an initializer
+//!
+//! Often when working with primitives the previous approaches are not sufficient. That is where
+//! [`pin_init_from_closure()`] comes in. This `unsafe` function allows you to create a
+//! [`impl PinInit<T, E>`] directly from a closure. Of course you have to ensure that the closure
+//! actually does the initialization in the correct way. Here are the things to look out for
+//! (we are calling the parameter to the closure `slot`):
+//! - when the closure returns `Ok(())`, then it has completed the initialization successfully, so
+//! `slot` now contains a valid bit pattern for the type `T`,
+//! - when the closure returns `Err(e)`, then the caller may deallocate the memory at `slot`, so
+//! you need to take care to clean up anything if your initialization fails mid-way,
+//! - you may assume that `slot` will stay pinned even after the closure returns until `drop` of
+//! `slot` gets called.
+//!
+//! ```rust
+//! use kernel::{prelude::*, init};
+//! use core::{ptr::addr_of_mut, marker::PhantomPinned, pin::Pin};
+//! # mod bindings {
+//! # pub struct foo;
+//! # pub unsafe fn init_foo(_ptr: *mut foo) {}
+//! # pub unsafe fn destroy_foo(_ptr: *mut foo) {}
+//! # pub unsafe fn enable_foo(_ptr: *mut foo, _flags: u32) -> i32 { 0 }
+//! # }
+//! /// # Invariants
+//! ///
+//! /// `foo` is always initialized
+//! #[pin_data(PinnedDrop)]
+//! pub struct RawFoo {
+//! #[pin]
+//! foo: Opaque<bindings::foo>,
+//! #[pin]
+//! _p: PhantomPinned,
+//! }
+//!
+//! impl RawFoo {
+//! pub fn new(flags: u32) -> impl PinInit<Self, Error> {
+//! // SAFETY:
+//! // - when the closure returns `Ok(())`, then it has successfully initialized and
+//! // enabled `foo`,
+//! // - when it returns `Err(e)`, then it has cleaned up before
+//! unsafe {
+//! init::pin_init_from_closure(move |slot: *mut Self| {
+//! // `slot` contains uninit memory, avoid creating a reference.
+//! let foo = addr_of_mut!((*slot).foo);
+//!
+//! // Initialize the `foo`
+//! bindings::init_foo(Opaque::raw_get(foo));
+//!
+//! // Try to enable it.
+//! let err = bindings::enable_foo(Opaque::raw_get(foo), flags);
+//! if err != 0 {
+//! // Enabling has failed, first clean up the foo and then return the error.
+//! bindings::destroy_foo(Opaque::raw_get(foo));
+//! return Err(Error::from_kernel_errno(err));
+//! }
+//!
+//! // All fields of `RawFoo` have been initialized, since `_p` is a ZST.
+//! Ok(())
+//! })
+//! }
+//! }
+//! }
+//!
+//! #[pinned_drop]
+//! impl PinnedDrop for RawFoo {
+//! fn drop(self: Pin<&mut Self>) {
+//! // SAFETY: Since `foo` is initialized, destroying is safe.
+//! unsafe { bindings::destroy_foo(self.foo.get()) };
+//! }
+//! }
+//! ```
+//!
//! [`sync`]: kernel::sync
//! [pinning]: https://doc.rust-lang.org/std/pin/index.html
//! [structurally pinned fields]:
@@ -1084,3 +1156,42 @@ impl<T> InPlaceInit<T> for UniqueArc<T> {
Ok(unsafe { this.assume_init() })
}
}
+
+/// Trait facilitating pinned destruction.
+///
+/// Use [`pinned_drop`] to implement this trait safely:
+///
+/// ```rust
+/// # use kernel::sync::Mutex;
+/// use kernel::macros::pinned_drop;
+/// use core::pin::Pin;
+/// #[pin_data(PinnedDrop)]
+/// struct Foo {
+/// #[pin]
+/// mtx: Mutex<usize>,
+/// }
+///
+/// #[pinned_drop]
+/// impl PinnedDrop for Foo {
+/// fn drop(self: Pin<&mut Self>) {
+/// pr_info!("Foo is being dropped!");
+/// }
+/// }
+/// ```
+///
+/// # Safety
+///
+/// This trait must be implemented via the [`pinned_drop`] proc-macro attribute on the impl.
+///
+/// [`pinned_drop`]: kernel::macros::pinned_drop
+pub unsafe trait PinnedDrop: __internal::HasPinData {
+ /// Executes the pinned destructor of this type.
+ ///
+ /// While this function is marked safe, it is actually unsafe to call it manually. For this
+ /// reason it takes an additional parameter. This type can only be constructed by `unsafe` code
+ /// and thus prevents this function from being called where it should not.
+ ///
+ /// This extra parameter will be generated by the `#[pinned_drop]` proc-macro attribute
+ /// automatically.
+ fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop);
+}
diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs
index a3389a684296..774cb620afa7 100644
--- a/rust/kernel/init/__internal.rs
+++ b/rust/kernel/init/__internal.rs
@@ -161,3 +161,18 @@ impl<T: ?Sized> Drop for DropGuard<T> {
}
}
}
+
+/// Token used by `PinnedDrop` to prevent calling the function without creating this unsafely
+/// created struct. This is needed, because the `drop` function is safe, but should not be called
+/// manually.
+pub struct OnlyCallFromDrop(());
+
+impl OnlyCallFromDrop {
+ /// # Safety
+ ///
+ /// This function should only be called from the [`Drop::drop`] function and only be used to
+ /// delegate the destruction to the pinned destructor [`PinnedDrop::drop`] of the same type.
+ pub unsafe fn new() -> Self {
+ Self(())
+ }
+}
diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs
index 9ef02f5411a6..541cfad1d8be 100644
--- a/rust/kernel/init/macros.rs
+++ b/rust/kernel/init/macros.rs
@@ -31,6 +31,26 @@
//! pin_init!(Self { t, x: 0 })
//! }
//! }
+//!
+//! #[pin_data(PinnedDrop)]
+//! struct Foo {
+//! a: usize,
+//! #[pin]
+//! b: Bar<u32>,
+//! }
+//!
+//! #[pinned_drop]
+//! impl PinnedDrop for Foo {
+//! fn drop(self: Pin<&mut Self>) {
+//! println!("{self:p} is getting dropped.");
+//! }
+//! }
+//!
+//! let a = 42;
+//! let initializer = pin_init!(Foo {
+//! a,
+//! b <- Bar::new(36),
+//! });
//! ```
//!
//! This example includes the most common and important features of the pin-init API.
@@ -155,6 +175,14 @@
//! #[allow(drop_bounds)]
//! impl<T: ::core::ops::Drop> MustNotImplDrop for T {}
//! impl<T> MustNotImplDrop for Bar<T> {}
+//! // Here comes a convenience check, if one implemented `PinnedDrop`, but forgot to add it to
+//! // `#[pin_data]`, then this will error with the same mechanic as above, this is not needed
+//! // for safety, but a good sanity check, since no normal code calls `PinnedDrop::drop`.
+//! #[allow(non_camel_case_types)]
+//! trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {}
+//! impl<T: ::kernel::init::PinnedDrop>
+//! UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {}
+//! impl<T> UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for Bar<T> {}
//! };
//! ```
//!
@@ -265,6 +293,210 @@
//! }
//! }
//! ```
+//!
+//! ## `#[pin_data]` on `Foo`
+//!
+//! Since we already took a look at `#[pin_data]` on `Bar`, this section will only explain the
+//! differences/new things in the expansion of the `Foo` definition:
+//!
+//! ```rust
+//! #[pin_data(PinnedDrop)]
+//! struct Foo {
+//! a: usize,
+//! #[pin]
+//! b: Bar<u32>,
+//! }
+//! ```
+//!
+//! This expands to the following code:
+//!
+//! ```rust
+//! struct Foo {
+//! a: usize,
+//! b: Bar<u32>,
+//! }
+//! const _: () = {
+//! struct __ThePinData {
+//! __phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>,
+//! }
+//! impl ::core::clone::Clone for __ThePinData {
+//! fn clone(&self) -> Self {
+//! *self
+//! }
+//! }
+//! impl ::core::marker::Copy for __ThePinData {}
+//! #[allow(dead_code)]
+//! impl __ThePinData {
+//! unsafe fn b<E>(
+//! self,
+//! slot: *mut Bar<u32>,
+//! // Note that this is `PinInit` instead of `Init`, this is because `b` is
+//! // structurally pinned, as marked by the `#[pin]` attribute.
+//! init: impl ::kernel::init::PinInit<Bar<u32>, E>,
+//! ) -> ::core::result::Result<(), E> {
+//! unsafe { ::kernel::init::PinInit::__pinned_init(init, slot) }
+//! }
+//! unsafe fn a<E>(
+//! self,
+//! slot: *mut usize,
+//! init: impl ::kernel::init::Init<usize, E>,
+//! ) -> ::core::result::Result<(), E> {
+//! unsafe { ::kernel::init::Init::__init(init, slot) }
+//! }
+//! }
+//! unsafe impl ::kernel::init::__internal::HasPinData for Foo {
+//! type PinData = __ThePinData;
+//! unsafe fn __pin_data() -> Self::PinData {
+//! __ThePinData {
+//! __phantom: ::core::marker::PhantomData,
+//! }
+//! }
+//! }
+//! unsafe impl ::kernel::init::__internal::PinData for __ThePinData {
+//! type Datee = Foo;
+//! }
+//! #[allow(dead_code)]
+//! struct __Unpin<'__pin> {
+//! __phantom_pin: ::core::marker::PhantomData<fn(&'__pin ()) -> &'__pin ()>,
+//! __phantom: ::core::marker::PhantomData<fn(Foo) -> Foo>,
+//! // Since this field is `#[pin]`, it is listed here.
+//! b: Bar<u32>,
+//! }
+//! #[doc(hidden)]
+//! impl<'__pin> ::core::marker::Unpin for Foo where __Unpin<'__pin>: ::core::marker::Unpin {}
+//! // Since we specified `PinnedDrop` as the argument to `#[pin_data]`, we expect `Foo` to
+//! // implement `PinnedDrop`. Thus we do not need to prevent `Drop` implementations like
+//! // before, instead we implement it here and delegate to `PinnedDrop`.
+//! impl ::core::ops::Drop for Foo {
+//! fn drop(&mut self) {
+//! // Since we are getting dropped, no one else has a reference to `self` and thus we
+//! // can assume that we never move.
+//! let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) };
+//! // Create the unsafe token that proves that we are inside of a destructor, this
+//! // type is only allowed to be created in a destructor.
+//! let token = unsafe { ::kernel::init::__internal::OnlyCallFromDrop::new() };
+//! ::kernel::init::PinnedDrop::drop(pinned, token);
+//! }
+//! }
+//! };
+//! ```
+//!
+//! ## `#[pinned_drop]` on `impl PinnedDrop for Foo`
+//!
+//! This macro is used to implement the `PinnedDrop` trait, since that trait is `unsafe` and has an
+//! extra parameter that should not be used at all. The macro hides that parameter.
+//!
+//! Here is the `PinnedDrop` impl for `Foo`:
+//!
+//! ```rust
+//! #[pinned_drop]
+//! impl PinnedDrop for Foo {
+//! fn drop(self: Pin<&mut Self>) {
+//! println!("{self:p} is getting dropped.");
+//! }
+//! }
+//! ```
+//!
+//! This expands to the following code:
+//!
+//! ```rust
+//! // `unsafe`, full path and the token parameter are added, everything else stays the same.
+//! unsafe impl ::kernel::init::PinnedDrop for Foo {
+//! fn drop(self: Pin<&mut Self>, _: ::kernel::init::__internal::OnlyCallFromDrop) {
+//! println!("{self:p} is getting dropped.");
+//! }
+//! }
+//! ```
+//!
+//! ## `pin_init!` on `Foo`
+//!
+//! Since we already took a look at `pin_init!` on `Bar`, this section will only explain the
+//! differences/new things in the expansion of `pin_init!` on `Foo`:
+//!
+//! ```rust
+//! let a = 42;
+//! let initializer = pin_init!(Foo {
+//! a,
+//! b <- Bar::new(36),
+//! });
+//! ```
+//!
+//! This expands to the following code:
+//!
+//! ```rust
+//! let a = 42;
+//! let initializer = {
+//! struct __InitOk;
+//! let data = unsafe {
+//! use ::kernel::init::__internal::HasPinData;
+//! Foo::__pin_data()
+//! };
+//! let init = ::kernel::init::__internal::PinData::make_closure::<
+//! _,
+//! __InitOk,
+//! ::core::convert::Infallible,
+//! >(data, move |slot| {
+//! {
+//! struct __InitOk;
+//! unsafe { ::core::ptr::write(&raw mut (*slot).a, a) };
+//! let a = &unsafe { ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).a) };
+//! let b = Bar::new(36);
+//! // Here we use `data` to access the correct field and require that `b` is of type
+//! // `PinInit<Bar<u32>, Infallible>`.
+//! unsafe { data.b(&raw mut (*slot).b, b)? };
+//! let b = &unsafe { ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).b) };
+//!
+//! #[allow(unreachable_code, clippy::diverging_sub_expression)]
+//! if false {
+//! unsafe {
+//! ::core::ptr::write(
+//! slot,
+//! Foo {
+//! a: ::core::panic!(),
+//! b: ::core::panic!(),
+//! },
+//! );
+//! };
+//! }
+//! unsafe { ::kernel::init::__internal::DropGuard::forget(a) };
+//! unsafe { ::kernel::init::__internal::DropGuard::forget(b) };
+//! }
+//! Ok(__InitOk)
+//! });
+//! let init = move |slot| -> ::core::result::Result<(), ::core::convert::Infallible> {
+//! init(slot).map(|__InitOk| ())
+//! };
+//! let init = unsafe {
+//! ::kernel::init::pin_init_from_closure::<_, ::core::convert::Infallible>(init)
+//! };
+//! init
+//! };
+//! ```
+
+/// Creates a `unsafe impl<...> PinnedDrop for $type` block.
+///
+/// See [`PinnedDrop`] for more information.
+#[doc(hidden)]
+#[macro_export]
+macro_rules! __pinned_drop {
+ (
+ @impl_sig($($impl_sig:tt)*),
+ @impl_body(
+ $(#[$($attr:tt)*])*
+ fn drop($($sig:tt)*) {
+ $($inner:tt)*
+ }
+ ),
+ ) => {
+ unsafe $($impl_sig)* {
+ // Inherit all attributes and the type/ident tokens for the signature.
+ $(#[$($attr)*])*
+ fn drop($($sig)*, _: $crate::init::__internal::OnlyCallFromDrop) {
+ $($inner)*
+ }
+ }
+ }
+}
/// This macro first parses the struct definition such that it separates pinned and not pinned
/// fields. Afterwards it declares the struct and implement the `PinData` trait safely.
@@ -653,6 +885,38 @@ macro_rules! __pin_data {
impl<T: ::core::ops::Drop> MustNotImplDrop for T {}
impl<$($impl_generics)*> MustNotImplDrop for $name<$($ty_generics)*>
where $($whr)* {}
+ // We also take care to prevent users from writing a useless `PinnedDrop` implementation.
+ // They might implement `PinnedDrop` correctly for the struct, but forget to give
+ // `PinnedDrop` as the parameter to `#[pin_data]`.
+ #[allow(non_camel_case_types)]
+ trait UselessPinnedDropImpl_you_need_to_specify_PinnedDrop {}
+ impl<T: $crate::init::PinnedDrop>
+ UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for T {}
+ impl<$($impl_generics)*>
+ UselessPinnedDropImpl_you_need_to_specify_PinnedDrop for $name<$($ty_generics)*>
+ where $($whr)* {}
+ };
+ // When `PinnedDrop` was specified we just implement `Drop` and delegate.
+ (drop_prevention:
+ @name($name:ident),
+ @impl_generics($($impl_generics:tt)*),
+ @ty_generics($($ty_generics:tt)*),
+ @where($($whr:tt)*),
+ @pinned_drop(PinnedDrop),
+ ) => {
+ impl<$($impl_generics)*> ::core::ops::Drop for $name<$($ty_generics)*>
+ where $($whr)*
+ {
+ fn drop(&mut self) {
+ // SAFETY: Since this is a destructor, `self` will not move after this function
+ // terminates, since it is inaccessible.
+ let pinned = unsafe { ::core::pin::Pin::new_unchecked(self) };
+ // SAFETY: Since this is a drop function, we can create this token to call the
+ // pinned destructor of this type.
+ let token = unsafe { $crate::init::__internal::OnlyCallFromDrop::new() };
+ $crate::init::PinnedDrop::drop(pinned, token);
+ }
+ }
};
// If some other parameter was specified, we emit a readable error.
(drop_prevention: