From fc6c6baa1f40ded13e539d0c1a17bcefc00abad9 Mon Sep 17 00:00:00 2001 From: Benno Lossin Date: Sat, 8 Apr 2023 12:25:51 +0000 Subject: rust: init: add initialization macros Add the following initializer macros: - `#[pin_data]` to annotate structurally pinned fields of structs, needed for `pin_init!` and `try_pin_init!` to select the correct initializer of fields. - `pin_init!` create a pin-initializer for a struct with the `Infallible` error type. - `try_pin_init!` create a pin-initializer for a struct with a custom error type (`kernel::error::Error` is the default). - `init!` create an in-place-initializer for a struct with the `Infallible` error type. - `try_init!` create an in-place-initializer for a struct with a custom error type (`kernel::error::Error` is the default). Also add their needed internal helper traits and structs. Co-developed-by: Gary Guo Signed-off-by: Gary Guo Signed-off-by: Benno Lossin Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Link: https://lore.kernel.org/r/20230408122429.1103522-8-y86-dev@protonmail.com [ Fixed three typos. ] Signed-off-by: Miguel Ojeda --- rust/kernel/init.rs | 807 ++++++++++++++++++++++++++++++++++++++++- rust/kernel/init/__internal.rs | 130 +++++++ rust/kernel/init/macros.rs | 707 ++++++++++++++++++++++++++++++++++++ rust/macros/lib.rs | 29 ++ rust/macros/pin_data.rs | 79 ++++ rust/macros/quote.rs | 2 - 6 files changed, 1747 insertions(+), 7 deletions(-) create mode 100644 rust/kernel/init/macros.rs create mode 100644 rust/macros/pin_data.rs (limited to 'rust') diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs index d041f0daf71e..ecef0376d726 100644 --- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -14,7 +14,8 @@ //! - an in-place constructor, //! - a memory location that can hold your `struct`. //! -//! To get an in-place constructor there are generally two options: +//! To get an in-place constructor there are generally three options: +//! - directly creating an in-place constructor using the [`pin_init!`] macro, //! - a custom function/macro returning an in-place constructor provided by someone else, //! - using the unsafe function [`pin_init_from_closure()`] to manually create an initializer. //! @@ -22,6 +23,87 @@ //! the macros/types/functions are generally named like the pinned variants without the `pin` //! prefix. //! +//! # Examples +//! +//! ## Using the [`pin_init!`] macro +//! +//! If you want to use [`PinInit`], then you will have to annotate your `struct` with +//! `#[`[`pin_data`]`]`. It is a macro that uses `#[pin]` as a marker for +//! [structurally pinned fields]. After doing this, you can then create an in-place constructor via +//! [`pin_init!`]. The syntax is almost the same as normal `struct` initializers. The difference is +//! that you need to write `<-` instead of `:` for fields that you want to initialize in-place. +//! +//! ```rust +//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +//! use kernel::{prelude::*, sync::Mutex, new_mutex}; +//! # use core::pin::Pin; +//! #[pin_data] +//! struct Foo { +//! #[pin] +//! a: Mutex, +//! b: u32, +//! } +//! +//! let foo = pin_init!(Foo { +//! a <- new_mutex!(42, "Foo::a"), +//! b: 24, +//! }); +//! ``` +//! +//! `foo` now is of the type [`impl PinInit`]. We can now use any smart pointer that we like +//! (or just the stack) to actually initialize a `Foo`: +//! +//! ```rust +//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +//! # use kernel::{prelude::*, sync::Mutex, new_mutex}; +//! # use core::pin::Pin; +//! # #[pin_data] +//! # struct Foo { +//! # #[pin] +//! # a: Mutex, +//! # b: u32, +//! # } +//! # let foo = pin_init!(Foo { +//! # a <- new_mutex!(42, "Foo::a"), +//! # b: 24, +//! # }); +//! let foo: Result>> = Box::pin_init(foo); +//! ``` +//! +//! For more information see the [`pin_init!`] macro. +//! +//! ## Using a custom function/macro that returns an initializer +//! +//! Many types from the kernel supply a function/macro that returns an initializer, because the +//! above method only works for types where you can access the fields. +//! +//! ```rust +//! # use kernel::{new_mutex, sync::{Arc, Mutex}}; +//! let mtx: Result>> = Arc::pin_init(new_mutex!(42, "example::mtx")); +//! ``` +//! +//! To declare an init macro/function you just return an [`impl PinInit`]: +//! +//! ```rust +//! # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +//! # use kernel::{sync::Mutex, prelude::*, new_mutex, init::PinInit, try_pin_init}; +//! #[pin_data] +//! struct DriverData { +//! #[pin] +//! status: Mutex, +//! buffer: Box<[u8; 1_000_000]>, +//! } +//! +//! impl DriverData { +//! fn new() -> impl PinInit { +//! try_pin_init!(Self { +//! status <- new_mutex!(0, "DriverData::status"), +//! buffer: Box::init(kernel::init::zeroed())?, +//! }) +//! } +//! } +//! ``` +//! //! [`sync`]: kernel::sync //! [pinning]: https://doc.rust-lang.org/std/pin/index.html //! [structurally pinned fields]: @@ -33,12 +115,729 @@ //! [`Opaque`]: kernel::types::Opaque //! [`pin_data`]: ::macros::pin_data //! [`UniqueArc`]: kernel::sync::UniqueArc -//! [`Box`]: alloc::boxed::Box -use core::{convert::Infallible, marker::PhantomData, mem::MaybeUninit}; +use alloc::boxed::Box; +use core::{cell::Cell, convert::Infallible, marker::PhantomData, mem::MaybeUninit, ptr}; #[doc(hidden)] pub mod __internal; +#[doc(hidden)] +pub mod macros; + +/// Construct an in-place, pinned initializer for `struct`s. +/// +/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use +/// [`try_pin_init!`]. +/// +/// The syntax is almost identical to that of a normal `struct` initializer: +/// +/// ```rust +/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +/// # use kernel::{init, pin_init, macros::pin_data, init::*}; +/// # use core::pin::Pin; +/// #[pin_data] +/// struct Foo { +/// a: usize, +/// b: Bar, +/// } +/// +/// #[pin_data] +/// struct Bar { +/// x: u32, +/// } +/// +/// # fn demo() -> impl PinInit { +/// let a = 42; +/// +/// let initializer = pin_init!(Foo { +/// a, +/// b: Bar { +/// x: 64, +/// }, +/// }); +/// # initializer } +/// # Box::pin_init(demo()).unwrap(); +/// ``` +/// +/// Arbitrary Rust expressions can be used to set the value of a variable. +/// +/// The fields are initialized in the order that they appear in the initializer. So it is possible +/// to read already initialized fields using raw pointers. +/// +/// IMPORTANT: You are not allowed to create references to fields of the struct inside of the +/// initializer. +/// +/// # Init-functions +/// +/// When working with this API it is often desired to let others construct your types without +/// giving access to all fields. This is where you would normally write a plain function `new` +/// that would return a new instance of your type. With this API that is also possible. +/// However, there are a few extra things to keep in mind. +/// +/// To create an initializer function, simply declare it like this: +/// +/// ```rust +/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +/// # use kernel::{init, pin_init, prelude::*, init::*}; +/// # use core::pin::Pin; +/// # #[pin_data] +/// # struct Foo { +/// # a: usize, +/// # b: Bar, +/// # } +/// # #[pin_data] +/// # struct Bar { +/// # x: u32, +/// # } +/// impl Foo { +/// fn new() -> impl PinInit { +/// pin_init!(Self { +/// a: 42, +/// b: Bar { +/// x: 64, +/// }, +/// }) +/// } +/// } +/// ``` +/// +/// Users of `Foo` can now create it like this: +/// +/// ```rust +/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +/// # use kernel::{init, pin_init, macros::pin_data, init::*}; +/// # use core::pin::Pin; +/// # #[pin_data] +/// # struct Foo { +/// # a: usize, +/// # b: Bar, +/// # } +/// # #[pin_data] +/// # struct Bar { +/// # x: u32, +/// # } +/// # impl Foo { +/// # fn new() -> impl PinInit { +/// # pin_init!(Self { +/// # a: 42, +/// # b: Bar { +/// # x: 64, +/// # }, +/// # }) +/// # } +/// # } +/// let foo = Box::pin_init(Foo::new()); +/// ``` +/// +/// They can also easily embed it into their own `struct`s: +/// +/// ```rust +/// # #![allow(clippy::disallowed_names, clippy::new_ret_no_self)] +/// # use kernel::{init, pin_init, macros::pin_data, init::*}; +/// # use core::pin::Pin; +/// # #[pin_data] +/// # struct Foo { +/// # a: usize, +/// # b: Bar, +/// # } +/// # #[pin_data] +/// # struct Bar { +/// # x: u32, +/// # } +/// # impl Foo { +/// # fn new() -> impl PinInit { +/// # pin_init!(Self { +/// # a: 42, +/// # b: Bar { +/// # x: 64, +/// # }, +/// # }) +/// # } +/// # } +/// #[pin_data] +/// struct FooContainer { +/// #[pin] +/// foo1: Foo, +/// #[pin] +/// foo2: Foo, +/// other: u32, +/// } +/// +/// impl FooContainer { +/// fn new(other: u32) -> impl PinInit { +/// pin_init!(Self { +/// foo1 <- Foo::new(), +/// foo2 <- Foo::new(), +/// other, +/// }) +/// } +/// } +/// ``` +/// +/// Here we see that when using `pin_init!` with `PinInit`, one needs to write `<-` instead of `:`. +/// This signifies that the given field is initialized in-place. As with `struct` initializers, just +/// writing the field (in this case `other`) without `:` or `<-` means `other: other,`. +/// +/// # Syntax +/// +/// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with +/// the following modifications is expected: +/// - Fields that you want to initialize in-place have to use `<-` instead of `:`. +/// - In front of the initializer you can write `&this in` to have access to a [`NonNull`] +/// pointer named `this` inside of the initializer. +/// +/// For instance: +/// +/// ```rust +/// # use kernel::pin_init; +/// # use macros::pin_data; +/// # use core::{ptr::addr_of_mut, marker::PhantomPinned}; +/// #[pin_data] +/// struct Buf { +/// // `ptr` points into `buf`. +/// ptr: *mut u8, +/// buf: [u8; 64], +/// #[pin] +/// pin: PhantomPinned, +/// } +/// pin_init!(&this in Buf { +/// buf: [0; 64], +/// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() }, +/// pin: PhantomPinned, +/// }); +/// ``` +/// +/// [`try_pin_init!`]: kernel::try_pin_init +/// [`NonNull`]: core::ptr::NonNull +/// [`Error`]: kernel::error::Error +// For a detailed example of how this macro works, see the module documentation of the hidden +// module `__internal` inside of `init/__internal.rs`. +#[macro_export] +macro_rules! pin_init { + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }) => { + $crate::try_pin_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)?), + @fields($($fields)*), + @error(::core::convert::Infallible), + ) + }; +} + +/// Construct an in-place, fallible pinned initializer for `struct`s. +/// +/// If the initialization can complete without error (or [`Infallible`]), then use [`pin_init!`]. +/// +/// You can use the `?` operator or use `return Err(err)` inside the initializer to stop +/// initialization and return the error. +/// +/// IMPORTANT: if you have `unsafe` code inside of the initializer you have to ensure that when +/// initialization fails, the memory can be safely deallocated without any further modifications. +/// +/// This macro defaults the error to [`Error`]. +/// +/// The syntax is identical to [`pin_init!`] with the following exception: you can append `? $type` +/// after the `struct` initializer to specify the error type you want to use. +/// +/// # Examples +/// +/// ```rust +/// # #![feature(new_uninit)] +/// use kernel::{init::{self, PinInit}, error::Error}; +/// #[pin_data] +/// struct BigBuf { +/// big: Box<[u8; 1024 * 1024 * 1024]>, +/// small: [u8; 1024 * 1024], +/// ptr: *mut u8, +/// } +/// +/// impl BigBuf { +/// fn new() -> impl PinInit { +/// try_pin_init!(Self { +/// big: Box::init(init::zeroed())?, +/// small: [0; 1024 * 1024], +/// ptr: core::ptr::null_mut(), +/// }? Error) +/// } +/// } +/// ``` +/// +/// [`Error`]: kernel::error::Error +// For a detailed example of how this macro works, see the module documentation of the hidden +// module `__internal` inside of `init/__internal.rs`. +#[macro_export] +macro_rules! try_pin_init { + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }) => { + $crate::try_pin_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)? ), + @fields($($fields)*), + @error($crate::error::Error), + ) + }; + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }? $err:ty) => { + $crate::try_pin_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)? ), + @fields($($fields)*), + @error($err), + ) + }; + ( + @this($($this:ident)?), + @typ($t:ident $(::<$($generics:ty),*>)?), + @fields($($fields:tt)*), + @error($err:ty), + ) => {{ + // We do not want to allow arbitrary returns, so we declare this type as the `Ok` return + // type and shadow it later when we insert the arbitrary user code. That way there will be + // no possibility of returning without `unsafe`. + struct __InitOk; + // Get the pin data from the supplied type. + let data = unsafe { + use $crate::init::__internal::HasPinData; + $t$(::<$($generics),*>)?::__pin_data() + }; + // Ensure that `data` really is of type `PinData` and help with type inference: + let init = $crate::init::__internal::PinData::make_closure::<_, __InitOk, $err>( + data, + move |slot| { + { + // Shadow the structure so it cannot be used to return early. + struct __InitOk; + // Create the `this` so it can be referenced by the user inside of the + // expressions creating the individual fields. + $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? + // Initialize every field. + $crate::try_pin_init!(init_slot: + @data(data), + @slot(slot), + @munch_fields($($fields)*,), + ); + // We use unreachable code to ensure that all fields have been mentioned exactly + // once, this struct initializer will still be type-checked and complain with a + // very natural error message if a field is forgotten/mentioned more than once. + #[allow(unreachable_code, clippy::diverging_sub_expression)] + if false { + $crate::try_pin_init!(make_initializer: + @slot(slot), + @type_name($t), + @munch_fields($($fields)*,), + @acc(), + ); + } + // Forget all guards, since initialization was a success. + $crate::try_pin_init!(forget_guards: + @munch_fields($($fields)*,), + ); + } + Ok(__InitOk) + } + ); + let init = move |slot| -> ::core::result::Result<(), $err> { + init(slot).map(|__InitOk| ()) + }; + let init = unsafe { $crate::init::pin_init_from_closure::<_, $err>(init) }; + init + }}; + (init_slot: + @data($data:ident), + @slot($slot:ident), + @munch_fields($(,)?), + ) => { + // Endpoint of munching, no fields are left. + }; + (init_slot: + @data($data:ident), + @slot($slot:ident), + // In-place initialization syntax. + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + let $field = $val; + // Call the initializer. + // + // SAFETY: `slot` is valid, because we are inside of an initializer closure, we + // return when an error/panic occurs. + // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`. + unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? }; + // Create the drop guard. + // + // We only give access to `&DropGuard`, so it cannot be forgotten via safe code. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::try_pin_init!(init_slot: + @data($data), + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (init_slot: + @data($data:ident), + @slot($slot:ident), + // Direct value init, this is safe for every field. + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + $(let $field = $val;)? + // Initialize the field. + // + // SAFETY: The memory at `slot` is uninitialized. + unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; + // Create the drop guard: + // + // We only give access to `&DropGuard`, so it cannot be accidentally forgotten. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::try_pin_init!(init_slot: + @data($data), + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($(,)?), + @acc($($acc:tt)*), + ) => { + // Endpoint, nothing more to munch, create the initializer. + // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to + // get the correct type inference here: + unsafe { + ::core::ptr::write($slot, $t { + $($acc)* + }); + } + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::try_pin_init!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)* $field: ::core::panic!(),), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::try_pin_init!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)* $field: ::core::panic!(),), + ); + }; + (forget_guards: + @munch_fields($(,)?), + ) => { + // Munching finished. + }; + (forget_guards: + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::try_pin_init!(forget_guards: + @munch_fields($($rest)*), + ); + }; + (forget_guards: + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::try_pin_init!(forget_guards: + @munch_fields($($rest)*), + ); + }; +} + +/// Construct an in-place initializer for `struct`s. +/// +/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use +/// [`try_init!`]. +/// +/// The syntax is identical to [`pin_init!`] and its safety caveats also apply: +/// - `unsafe` code must guarantee either full initialization or return an error and allow +/// deallocation of the memory. +/// - the fields are initialized in the order given in the initializer. +/// - no references to fields are allowed to be created inside of the initializer. +/// +/// This initializer is for initializing data in-place that might later be moved. If you want to +/// pin-initialize, use [`pin_init!`]. +/// +/// [`Error`]: kernel::error::Error +// For a detailed example of how this macro works, see the module documentation of the hidden +// module `__internal` inside of `init/__internal.rs`. +#[macro_export] +macro_rules! init { + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }) => { + $crate::try_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)?), + @fields($($fields)*), + @error(::core::convert::Infallible), + ) + } +} + +/// Construct an in-place fallible initializer for `struct`s. +/// +/// This macro defaults the error to [`Error`]. If you need [`Infallible`], then use +/// [`init!`]. +/// +/// The syntax is identical to [`try_pin_init!`]. If you want to specify a custom error, +/// append `? $type` after the `struct` initializer. +/// The safety caveats from [`try_pin_init!`] also apply: +/// - `unsafe` code must guarantee either full initialization or return an error and allow +/// deallocation of the memory. +/// - the fields are initialized in the order given in the initializer. +/// - no references to fields are allowed to be created inside of the initializer. +/// +/// # Examples +/// +/// ```rust +/// use kernel::{init::PinInit, error::Error, InPlaceInit}; +/// struct BigBuf { +/// big: Box<[u8; 1024 * 1024 * 1024]>, +/// small: [u8; 1024 * 1024], +/// } +/// +/// impl BigBuf { +/// fn new() -> impl Init { +/// try_init!(Self { +/// big: Box::init(zeroed())?, +/// small: [0; 1024 * 1024], +/// }? Error) +/// } +/// } +/// ``` +/// +/// [`Error`]: kernel::error::Error +// For a detailed example of how this macro works, see the module documentation of the hidden +// module `__internal` inside of `init/__internal.rs`. +#[macro_export] +macro_rules! try_init { + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }) => { + $crate::try_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)?), + @fields($($fields)*), + @error($crate::error::Error), + ) + }; + ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? { + $($fields:tt)* + }? $err:ty) => { + $crate::try_init!( + @this($($this)?), + @typ($t $(::<$($generics),*>)?), + @fields($($fields)*), + @error($err), + ) + }; + ( + @this($($this:ident)?), + @typ($t:ident $(::<$($generics:ty),*>)?), + @fields($($fields:tt)*), + @error($err:ty), + ) => {{ + // We do not want to allow arbitrary returns, so we declare this type as the `Ok` return + // type and shadow it later when we insert the arbitrary user code. That way there will be + // no possibility of returning without `unsafe`. + struct __InitOk; + // Get the init data from the supplied type. + let data = unsafe { + use $crate::init::__internal::HasInitData; + $t$(::<$($generics),*>)?::__init_data() + }; + // Ensure that `data` really is of type `InitData` and help with type inference: + let init = $crate::init::__internal::InitData::make_closure::<_, __InitOk, $err>( + data, + move |slot| { + { + // Shadow the structure so it cannot be used to return early. + struct __InitOk; + // Create the `this` so it can be referenced by the user inside of the + // expressions creating the individual fields. + $(let $this = unsafe { ::core::ptr::NonNull::new_unchecked(slot) };)? + // Initialize every field. + $crate::try_init!(init_slot: + @slot(slot), + @munch_fields($($fields)*,), + ); + // We use unreachable code to ensure that all fields have been mentioned exactly + // once, this struct initializer will still be type-checked and complain with a + // very natural error message if a field is forgotten/mentioned more than once. + #[allow(unreachable_code, clippy::diverging_sub_expression)] + if false { + $crate::try_init!(make_initializer: + @slot(slot), + @type_name($t), + @munch_fields($($fields)*,), + @acc(), + ); + } + // Forget all guards, since initialization was a success. + $crate::try_init!(forget_guards: + @munch_fields($($fields)*,), + ); + } + Ok(__InitOk) + } + ); + let init = move |slot| -> ::core::result::Result<(), $err> { + init(slot).map(|__InitOk| ()) + }; + let init = unsafe { $crate::init::init_from_closure::<_, $err>(init) }; + init + }}; + (init_slot: + @slot($slot:ident), + @munch_fields( $(,)?), + ) => { + // Endpoint of munching, no fields are left. + }; + (init_slot: + @slot($slot:ident), + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + let $field = $val; + // Call the initializer. + // + // SAFETY: `slot` is valid, because we are inside of an initializer closure, we + // return when an error/panic occurs. + unsafe { + $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))?; + } + // Create the drop guard. + // + // We only give access to `&DropGuard`, so it cannot be accidentally forgotten. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::try_init!(init_slot: + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (init_slot: + @slot($slot:ident), + // Direct value init. + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + $(let $field = $val;)? + // Call the initializer. + // + // SAFETY: The memory at `slot` is uninitialized. + unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) }; + // Create the drop guard. + // + // We only give access to `&DropGuard`, so it cannot be accidentally forgotten. + // + // SAFETY: We forget the guard later when initialization has succeeded. + let $field = &unsafe { + $crate::init::__internal::DropGuard::new(::core::ptr::addr_of_mut!((*$slot).$field)) + }; + + $crate::try_init!(init_slot: + @slot($slot), + @munch_fields($($rest)*), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields( $(,)?), + @acc($($acc:tt)*), + ) => { + // Endpoint, nothing more to munch, create the initializer. + // Since we are in the `if false` branch, this will never get executed. We abuse `slot` to + // get the correct type inference here: + unsafe { + ::core::ptr::write($slot, $t { + $($acc)* + }); + } + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::try_init!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)*$field: ::core::panic!(),), + ); + }; + (make_initializer: + @slot($slot:ident), + @type_name($t:ident), + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + @acc($($acc:tt)*), + ) => { + $crate::try_init!(make_initializer: + @slot($slot), + @type_name($t), + @munch_fields($($rest)*), + @acc($($acc)*$field: ::core::panic!(),), + ); + }; + (forget_guards: + @munch_fields($(,)?), + ) => { + // Munching finished. + }; + (forget_guards: + @munch_fields($field:ident <- $val:expr, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::try_init!(forget_guards: + @munch_fields($($rest)*), + ); + }; + (forget_guards: + @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*), + ) => { + unsafe { $crate::init::__internal::DropGuard::forget($field) }; + + $crate::try_init!(forget_guards: + @munch_fields($($rest)*), + ); + }; +} /// A pin-initializer for the type `T`. /// @@ -63,7 +862,6 @@ pub mod __internal; /// [`Arc`]: crate::sync::Arc /// [`Arc::pin_init`]: crate::sync::Arc::pin_init /// [`UniqueArc`]: kernel::sync::UniqueArc -/// [`Box`]: alloc::boxed::Box #[must_use = "An initializer must be used in order to create its value."] pub unsafe trait PinInit: Sized { /// Initializes `slot`. @@ -106,7 +904,6 @@ pub unsafe trait PinInit: Sized { /// /// [`Arc`]: crate::sync::Arc /// [`UniqueArc`]: kernel::sync::UniqueArc -/// [`Box`]: alloc::boxed::Box #[must_use = "An initializer must be used in order to create its value."] pub unsafe trait Init: Sized { /// Initializes `slot`. diff --git a/rust/kernel/init/__internal.rs b/rust/kernel/init/__internal.rs index 08cbb5333438..a3389a684296 100644 --- a/rust/kernel/init/__internal.rs +++ b/rust/kernel/init/__internal.rs @@ -31,3 +31,133 @@ where (self.0)(slot) } } + +/// This trait is only implemented via the `#[pin_data]` proc-macro. It is used to facilitate +/// the pin projections within the initializers. +/// +/// # Safety +/// +/// Only the `init` module is allowed to use this trait. +pub unsafe trait HasPinData { + type PinData: PinData; + + unsafe fn __pin_data() -> Self::PinData; +} + +/// Marker trait for pinning data of structs. +/// +/// # Safety +/// +/// Only the `init` module is allowed to use this trait. +pub unsafe trait PinData: Copy { + type Datee: ?Sized + HasPinData; + + /// Type inference helper function. + fn make_closure(self, f: F) -> F + where + F: FnOnce(*mut Self::Datee) -> Result, + { + f + } +} + +/// This trait is automatically implemented for every type. It aims to provide the same type +/// inference help as `HasPinData`. +/// +/// # Safety +/// +/// Only the `init` module is allowed to use this trait. +pub unsafe trait HasInitData { + type InitData: InitData; + + unsafe fn __init_data() -> Self::InitData; +} + +/// Same function as `PinData`, but for arbitrary data. +/// +/// # Safety +/// +/// Only the `init` module is allowed to use this trait. +pub unsafe trait InitData: Copy { + type Datee: ?Sized + HasInitData; + + /// Type inference helper function. + fn make_closure(self, f: F) -> F + where + F: FnOnce(*mut Self::Datee) -> Result, + { + f + } +} + +pub struct AllData(PhantomData) -> Box>); + +impl Clone for AllData { + fn clone(&self) -> Self { + *self + } +} + +impl Copy for AllData {} + +unsafe impl InitData for AllData { + type Datee = T; +} + +unsafe impl HasInitData for T { + type InitData = AllData; + + unsafe fn __init_data() -> Self::InitData { + AllData(PhantomData) + } +} + +/// When a value of this type is dropped, it drops a `T`. +/// +/// Can be forgotten to prevent the drop. +pub struct DropGuard { + ptr: *mut T, + do_drop: Cell, +} + +impl DropGuard { + /// Creates a new [`DropGuard`]. It will [`ptr::drop_in_place`] `ptr` when it gets dropped. + /// + /// # Safety + /// + /// `ptr` must be a valid pointer. + /// + /// It is the callers responsibility that `self` will only get dropped if the pointee of `ptr`: + /// - has not been dropped, + /// - is not accessible by any other means, + /// - will not be dropped by any other means. + #[inline] + pub unsafe fn new(ptr: *mut T) -> Self { + Self { + ptr, + do_drop: Cell::new(true), + } + } + + /// Prevents this guard from dropping the supplied pointer. + /// + /// # Safety + /// + /// This function is unsafe in order to prevent safe code from forgetting this guard. It should + /// only be called by the macros in this module. + #[inline] + pub unsafe fn forget(&self) { + self.do_drop.set(false); + } +} + +impl Drop for DropGuard { + #[inline] + fn drop(&mut self) { + if self.do_drop.get() { + // SAFETY: A `DropGuard` can only be constructed using the unsafe `new` function + // ensuring that this operation is safe. + unsafe { ptr::drop_in_place(self.ptr) } + } + } +} diff --git a/rust/kernel/init/macros.rs b/rust/kernel/init/macros.rs new file mode 100644 index 000000000000..9ef02f5411a6 --- /dev/null +++ b/rust/kernel/init/macros.rs @@ -0,0 +1,707 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +//! This module provides the macros that actually implement the proc-macros `pin_data` and +//! `pinned_drop`. +//! +//! These macros should never be called directly, since they expect their input to be +//! in a certain format which is internal. Use the proc-macros instead. +//! +//! This architecture has been chosen because the kernel does not yet have access to `syn` which +//! would make matters a lot easier for implementing these as proc-macros. +//! +//! # Macro expansion example +//! +//! This section is intended for readers trying to understand the macros in this module and the +//! `pin_init!` macros from `init.rs`. +//! +//! We will look at the following example: +//! +//! ```rust +//! # use kernel::init::*; +//! #[pin_data] +//! #[repr(C)] +//! struct Bar { +//! #[pin] +//! t: T, +//! pub x: usize, +//! } +//! +//! impl Bar { +//! fn new(t: T) -> impl PinInit { +//! pin_init!(Self { t, x: 0 }) +//! } +//! } +//! ``` +//! +//! This example includes the most common and important features of the pin-init API. +//! +//! Below you can find individual section about the different macro invocations. Here are some +//! general things we need to take into account when designing macros: +//! - use global paths, similarly to file paths, these start with the separator: `::core::panic!()` +//! this ensures that the correct item is used, since users could define their own `mod core {}` +//! and then their own `panic!` inside to execute arbitrary code inside of our macro. +//! - macro `unsafe` hygiene: we need to ensure that we do not expand arbitrary, user-supplied +//! expressions inside of an `unsafe` block in the macro, because this would allow users to do +//! `unsafe` operations without an associated `unsafe` block. +//! +//! ## `#[pin_data]` on `Bar` +//! +//! This macro is used to specify which fields are structurally pinned and which fields are not. It +//! is placed on the struct definition and allows `#[pin]` to be placed on the fields. +//! +//! Here is the definition of `Bar` from our example: +//! +//! ```rust +//! # use kernel::init::*; +//! #[pin_data] +//! #[repr(C)] +//! struct Bar { +//! t: T, +//! pub x: usize, +//! } +//! ``` +//! +//! This expands to the following code: +//! +//! ```rust +//! // Firstly the normal definition of the struct, attributes are preserved: +//! #[repr(C)] +//! struct Bar { +//! t: T, +//! pub x: usize, +//! } +//! // Then an anonymous constant is defined, this is because we do not want any code to access the +//! // types that we define inside: +//! const _: () = { +//! // We define the pin-data carrying struct, it is a ZST and needs to have the same generics, +//! // since we need to implement access functions for each field and thus need to know its +//! // type. +//! struct __ThePinData { +//! __phantom: ::core::marker::PhantomData) -> Bar>, +//! } +//! // We implement `Copy` for the pin-data struct, since all functions it defines will take +//! // `self` by value. +//! impl ::core::clone::Clone for __ThePinData { +//! fn clone(&self) -> Self { +//! *self +//! } +//! } +//! impl ::core::marker::Copy for __ThePinData {} +//! // For every field of `Bar`, the pin-data struct will define a function with the same name +//! // and accessor (`pub` or `pub(crate)` etc.). This function will take a pointer to the +//! // field (`slot`) and a `PinInit` or `Init` depending on the projection kind of the field +//! // (if pinning is structural for the field, then `PinInit` otherwise `Init`). +//! #[allow(dead_code)] +//! impl __ThePinData { +//! unsafe fn t( +//! self, +//! slot: *mut T, +//! init: impl ::kernel::init::Init, +//! ) -> ::core::result::Result<(), E> { +//! unsafe { ::kernel::init::Init::__init(init, slot) } +//! } +//! pub unsafe fn x( +//! self, +//! slot: *mut usize, +//! init: impl ::kernel::init::Init, +//! ) -> ::core::result::Result<(), E> { +//! unsafe { ::kernel::init::Init::__init(init, slot) } +//! } +//! } +//! // Implement the internal `HasPinData` trait that associates `Bar` with the pin-data struct +//! // that we constructed beforehand. +//! unsafe impl ::kernel::init::__internal::HasPinData for Bar { +//! type PinData = __ThePinData; +//! unsafe fn __pin_data() -> Self::PinData { +//! __ThePinData { +//! __phantom: ::core::marker::PhantomData, +//! } +//! } +//! } +//! // Implement the internal `PinData` trait that marks the pin-data struct as a pin-data +//! // struct. This is important to ensure that no user can implement a rouge `__pin_data` +//! // function without using `unsafe`. +//! unsafe impl ::kernel::init::__internal::PinData for __ThePinData { +//! type Datee = Bar; +//! } +//! // Now we only want to implement `Unpin` for `Bar` when every structurally pinned field is +//! // `Unpin`. In other words, whether `Bar` is `Unpin` only depends on structurally pinned +//! // fields (those marked with `#[pin]`). These fields will be listed in this struct, in our +//! // case no such fields exist, hence this is almost empty. The two phantomdata fields exist +//! // for two reasons: +//! // - `__phantom`: every generic must be used, since we cannot really know which generics +//! // are used, we declere all and then use everything here once. +//! // - `__phantom_pin`: uses the `'__pin` lifetime and ensures that this struct is invariant +//! // over it. The lifetime is needed to work around the limitation that trait bounds must +//! // not be trivial, e.g. the user has a `#[pin] PhantomPinned` field -- this is +//! // unconditionally `!Unpin` and results in an error. The lifetime tricks the compiler +//! // into accepting these bounds regardless. +//! #[allow(dead_code)] +//! struct __Unpin<'__pin, T> { +//! __phantom_pin: ::core::marker::PhantomData &'__pin ()>, +//! __phantom: ::core::marker::PhantomData) -> Bar>, +//! } +//! #[doc(hidden)] +//! impl<'__pin, T> +//! ::core::marker::Unpin for Bar where __Unpin<'__pin, T>: ::core::marker::Unpin {} +//! // Now we need to ensure that `Bar` does not implement `Drop`, since that would give users +//! // access to `&mut self` inside of `drop` even if the struct was pinned. This could lead to +//! // UB with only safe code, so we disallow this by giving a trait implementation error using +//! // a direct impl and a blanket implementation. +//! trait MustNotImplDrop {} +//! // Normally `Drop` bounds do not have the correct semantics, but for this purpose they do +//! // (normally people want to know if a type has any kind of drop glue at all, here we want +//! // to know if it has any kind of custom drop glue, which is exactly what this bound does). +//! #[allow(drop_bounds)] +//! impl MustNotImplDrop for T {} +//! impl MustNotImplDrop for Bar {} +//! }; +//! ``` +//! +//! ## `pin_init!` in `impl Bar` +//! +//! This macro creates an pin-initializer for the given struct. It requires that the struct is +//! annotated by `#[pin_data]`. +//! +//! Here is the impl on `Bar` defining the new function: +//! +//! ```rust +//! impl Bar { +//! fn new(t: T) -> impl PinInit { +//! pin_init!(Self { t, x: 0 }) +//! } +//! } +//! ``` +//! +//! This expands to the following code: +//! +//! ```rust +//! impl Bar { +//! fn new(t: T) -> impl PinInit { +//! { +//! // We do not want to allow arbitrary returns, so we declare this type as the `Ok` +//! // return type and shadow it later when we insert the arbitrary user code. That way +//! // there will be no possibility of returning without `unsafe`. +//! struct __InitOk; +//! // Get the pin-data type from the initialized type. +//! // - the function is unsafe, hence the unsafe block +//! // - we `use` the `HasPinData` trait in the block, it is only available in that +//! // scope. +//! let data = unsafe { +//! use ::kernel::init::__internal::HasPinData; +//! Self::__pin_data() +//! }; +//! // Use `data` to help with type inference, the closure supplied will have the type +//! // `FnOnce(*mut Self) -> Result<__InitOk, Infallible>`. +//! let init = ::kernel::init::__internal::PinData::make_closure::< +//! _, +//! __InitOk, +//! ::core::convert::Infallible, +//! >(data, move |slot| { +//! { +//! // Shadow the structure so it cannot be used to return early. If a user +//! // tries to write `return Ok(__InitOk)`, then they get a type error, since +//! // that will refer to this struct instead of the one defined above. +//! struct __InitOk; +//! // This is the expansion of `t,`, which is syntactic sugar for `t: t,`. +//! unsafe { ::core::ptr::write(&raw mut (*slot).t, t) }; +//! // Since initialization could fail later (not in this case, since the error +//! // type is `Infallible`) we will need to drop this field if it fails. This +//! // `DropGuard` will drop the field when it gets dropped and has not yet +//! // been forgotten. We make a reference to it, so users cannot `mem::forget` +//! // it from the initializer, since the name is the same as the field. +//! let t = &unsafe { +//! ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).t) +//! }; +//! // Expansion of `x: 0,`: +//! // Since this can be an arbitrary expression we cannot place it inside of +//! // the `unsafe` block, so we bind it here. +//! let x = 0; +//! unsafe { ::core::ptr::write(&raw mut (*slot).x, x) }; +//! let x = &unsafe { +//! ::kernel::init::__internal::DropGuard::new(&raw mut (*slot).x) +//! }; +//! +//! // Here we use the type checker to ensuer that every field has been +//! // initialized exactly once, since this is `if false` it will never get +//! // executed, but still type-checked. +//! // Additionally we abuse `slot` to automatically infer the correct type for +//! // the struct. This is also another check that every field is accessible +//! // from this scope. +//! #[allow(unreachable_code, clippy::diverging_sub_expression)] +//! if false { +//! unsafe { +//! ::core::ptr::write( +//! slot, +//! Self { +//! // We only care about typecheck finding every field here, +//! // the expression does not matter, just conjure one using +//! // `panic!()`: +//! t: ::core::panic!(), +//! x: ::core::panic!(), +//! }, +//! ); +//! }; +//! } +//! // Since initialization has successfully completed, we can now forget the +//! // guards. +//! unsafe { ::kernel::init::__internal::DropGuard::forget(t) }; +//! unsafe { ::kernel::init::__internal::DropGuard::forget(x) }; +//! } +//! // We leave the scope above and gain access to the previously shadowed +//! // `__InitOk` that we need to return. +//! Ok(__InitOk) +//! }); +//! // Change the return type of the closure. +//! let init = move |slot| -> ::core::result::Result<(), ::core::convert::Infallible> { +//! init(slot).map(|__InitOk| ()) +//! }; +//! // Construct the initializer. +//! let init = unsafe { +//! ::kernel::init::pin_init_from_closure::<_, ::core::convert::Infallible>(init) +//! }; +//! init +//! } +//! } +//! } +//! ``` + +/// 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. +#[doc(hidden)] +#[macro_export] +macro_rules! __pin_data { + // Proc-macro entry point, this is supplied by the proc-macro pre-parsing. + (parse_input: + @args($($pinned_drop:ident)?), + @sig( + $(#[$($struct_attr:tt)*])* + $vis:vis struct $name:ident + $(where $($whr:tt)*)? + ), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @body({ $($fields:tt)* }), + ) => { + // We now use token munching to iterate through all of the fields. While doing this we + // identify fields marked with `#[pin]`, these fields are the 'pinned fields'. The user + // wants these to be structurally pinned. The rest of the fields are the + // 'not pinned fields'. Additionally we collect all fields, since we need them in the right + // order to declare the struct. + // + // In this call we also put some explaining comments for the parameters. + $crate::__pin_data!(find_pinned_fields: + // Attributes on the struct itself, these will just be propagated to be put onto the + // struct definition. + @struct_attrs($(#[$($struct_attr)*])*), + // The visibility of the struct. + @vis($vis), + // The name of the struct. + @name($name), + // The 'impl generics', the generics that will need to be specified on the struct inside + // of an `impl<$ty_generics>` block. + @impl_generics($($impl_generics)*), + // The 'ty generics', the generics that will need to be specified on the impl blocks. + @ty_generics($($ty_generics)*), + // The where clause of any impl block and the declaration. + @where($($($whr)*)?), + // The remaining fields tokens that need to be processed. + // We add a `,` at the end to ensure correct parsing. + @fields_munch($($fields)* ,), + // The pinned fields. + @pinned(), + // The not pinned fields. + @not_pinned(), + // All fields. + @fields(), + // The accumulator containing all attributes already parsed. + @accum(), + // Contains `yes` or `` to indicate if `#[pin]` was found on the current field. + @is_pinned(), + // The proc-macro argument, this should be `PinnedDrop` or ``. + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We found a PhantomPinned field, this should generally be pinned! + @fields_munch($field:ident : $($($(::)?core::)?marker::)?PhantomPinned, $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + // This field is not pinned. + @is_pinned(), + @pinned_drop($($pinned_drop:ident)?), + ) => { + ::core::compile_error!(concat!( + "The field `", + stringify!($field), + "` of type `PhantomPinned` only has an effect, if it has the `#[pin]` attribute.", + )); + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($($rest)*), + @pinned($($pinned)* $($accum)* $field: ::core::marker::PhantomPinned,), + @not_pinned($($not_pinned)*), + @fields($($fields)* $($accum)* $field: ::core::marker::PhantomPinned,), + @accum(), + @is_pinned(), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We reached the field declaration. + @fields_munch($field:ident : $type:ty, $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + // This field is pinned. + @is_pinned(yes), + @pinned_drop($($pinned_drop:ident)?), + ) => { + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($($rest)*), + @pinned($($pinned)* $($accum)* $field: $type,), + @not_pinned($($not_pinned)*), + @fields($($fields)* $($accum)* $field: $type,), + @accum(), + @is_pinned(), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We reached the field declaration. + @fields_munch($field:ident : $type:ty, $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + // This field is not pinned. + @is_pinned(), + @pinned_drop($($pinned_drop:ident)?), + ) => { + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($($rest)*), + @pinned($($pinned)*), + @not_pinned($($not_pinned)* $($accum)* $field: $type,), + @fields($($fields)* $($accum)* $field: $type,), + @accum(), + @is_pinned(), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We found the `#[pin]` attr. + @fields_munch(#[pin] $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + @is_pinned($($is_pinned:ident)?), + @pinned_drop($($pinned_drop:ident)?), + ) => { + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($($rest)*), + // We do not include `#[pin]` in the list of attributes, since it is not actually an + // attribute that is defined somewhere. + @pinned($($pinned)*), + @not_pinned($($not_pinned)*), + @fields($($fields)*), + @accum($($accum)*), + // Set this to `yes`. + @is_pinned(yes), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We reached the field declaration with visibility, for simplicity we only munch the + // visibility and put it into `$accum`. + @fields_munch($fvis:vis $field:ident $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + @is_pinned($($is_pinned:ident)?), + @pinned_drop($($pinned_drop:ident)?), + ) => { + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($field $($rest)*), + @pinned($($pinned)*), + @not_pinned($($not_pinned)*), + @fields($($fields)*), + @accum($($accum)* $fvis), + @is_pinned($($is_pinned)?), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // Some other attribute, just put it into `$accum`. + @fields_munch(#[$($attr:tt)*] $($rest:tt)*), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum($($accum:tt)*), + @is_pinned($($is_pinned:ident)?), + @pinned_drop($($pinned_drop:ident)?), + ) => { + $crate::__pin_data!(find_pinned_fields: + @struct_attrs($($struct_attrs)*), + @vis($vis), + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @fields_munch($($rest)*), + @pinned($($pinned)*), + @not_pinned($($not_pinned)*), + @fields($($fields)*), + @accum($($accum)* #[$($attr)*]), + @is_pinned($($is_pinned)?), + @pinned_drop($($pinned_drop)?), + ); + }; + (find_pinned_fields: + @struct_attrs($($struct_attrs:tt)*), + @vis($vis:vis), + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + // We reached the end of the fields, plus an optional additional comma, since we added one + // before and the user is also allowed to put a trailing comma. + @fields_munch($(,)?), + @pinned($($pinned:tt)*), + @not_pinned($($not_pinned:tt)*), + @fields($($fields:tt)*), + @accum(), + @is_pinned(), + @pinned_drop($($pinned_drop:ident)?), + ) => { + // Declare the struct with all fields in the correct order. + $($struct_attrs)* + $vis struct $name <$($impl_generics)*> + where $($whr)* + { + $($fields)* + } + + // We put the rest into this const item, because it then will not be accessible to anything + // outside. + const _: () = { + // We declare this struct which will host all of the projection function for our type. + // it will be invariant over all generic parameters which are inherited from the + // struct. + $vis struct __ThePinData<$($impl_generics)*> + where $($whr)* + { + __phantom: ::core::marker::PhantomData< + fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> + >, + } + + impl<$($impl_generics)*> ::core::clone::Clone for __ThePinData<$($ty_generics)*> + where $($whr)* + { + fn clone(&self) -> Self { *self } + } + + impl<$($impl_generics)*> ::core::marker::Copy for __ThePinData<$($ty_generics)*> + where $($whr)* + {} + + // Make all projection functions. + $crate::__pin_data!(make_pin_data: + @pin_data(__ThePinData), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @pinned($($pinned)*), + @not_pinned($($not_pinned)*), + ); + + // SAFETY: We have added the correct projection functions above to `__ThePinData` and + // we also use the least restrictive generics possible. + unsafe impl<$($impl_generics)*> + $crate::init::__internal::HasPinData for $name<$($ty_generics)*> + where $($whr)* + { + type PinData = __ThePinData<$($ty_generics)*>; + + unsafe fn __pin_data() -> Self::PinData { + __ThePinData { __phantom: ::core::marker::PhantomData } + } + } + + unsafe impl<$($impl_generics)*> + $crate::init::__internal::PinData for __ThePinData<$($ty_generics)*> + where $($whr)* + { + type Datee = $name<$($ty_generics)*>; + } + + // This struct will be used for the unpin analysis. Since only structurally pinned + // fields are relevant whether the struct should implement `Unpin`. + #[allow(dead_code)] + struct __Unpin <'__pin, $($impl_generics)*> + where $($whr)* + { + __phantom_pin: ::core::marker::PhantomData &'__pin ()>, + __phantom: ::core::marker::PhantomData< + fn($name<$($ty_generics)*>) -> $name<$($ty_generics)*> + >, + // Only the pinned fields. + $($pinned)* + } + + #[doc(hidden)] + impl<'__pin, $($impl_generics)*> ::core::marker::Unpin for $name<$($ty_generics)*> + where + __Unpin<'__pin, $($ty_generics)*>: ::core::marker::Unpin, + $($whr)* + {} + + // We need to disallow normal `Drop` implementation, the exact behavior depends on + // whether `PinnedDrop` was specified as the parameter. + $crate::__pin_data!(drop_prevention: + @name($name), + @impl_generics($($impl_generics)*), + @ty_generics($($ty_generics)*), + @where($($whr)*), + @pinned_drop($($pinned_drop)?), + ); + }; + }; + // When no `PinnedDrop` was specified, then we have to prevent implementing drop. + (drop_prevention: + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + @pinned_drop(), + ) => { + // We prevent this by creating a trait that will be implemented for all types implementing + // `Drop`. Additionally we will implement this trait for the struct leading to a conflict, + // if it also implements `Drop` + trait MustNotImplDrop {} + #[allow(drop_bounds)] + impl MustNotImplDrop for T {} + impl<$($impl_generics)*> MustNotImplDrop for $name<$($ty_generics)*> + where $($whr)* {} + }; + // If some other parameter was specified, we emit a readable error. + (drop_prevention: + @name($name:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + @pinned_drop($($rest:tt)*), + ) => { + compile_error!( + "Wrong parameters to `#[pin_data]`, expected nothing or `PinnedDrop`, got '{}'.", + stringify!($($rest)*), + ); + }; + (make_pin_data: + @pin_data($pin_data:ident), + @impl_generics($($impl_generics:tt)*), + @ty_generics($($ty_generics:tt)*), + @where($($whr:tt)*), + @pinned($($(#[$($p_attr:tt)*])* $pvis:vis $p_field:ident : $p_type:ty),* $(,)?), + @not_pinned($($(#[$($attr:tt)*])* $fvis:vis $field:ident : $type:ty),* $(,)?), + ) => { + // For every field, we create a projection function according to its projection type. If a + // field is structurally pinned, then it must be initialized via `PinInit`, if it is not + // structurally pinned, then it can be initialized via `Init`. + // + // The functions are `unsafe` to prevent accidentally calling them. + #[allow(dead_code)] + impl<$($impl_generics)*> $pin_data<$($ty_generics)*> + where $($whr)* + { + $( + $pvis unsafe fn $p_field( + self, + slot: *mut $p_type, + init: impl $crate::init::PinInit<$p_type, E>, + ) -> ::core::result::Result<(), E> { + unsafe { $crate::init::PinInit::__pinned_init(init, slot) } + } + )* + $( + $fvis unsafe fn $field( + self, + slot: *mut $type, + init: impl $crate::init::Init<$type, E>, + ) -> ::core::result::Result<(), E> { + unsafe { $crate::init::Init::__init(init, slot) } + } + )* + } + }; +} diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index 82b520f024dd..6d84f2fd0d77 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -7,6 +7,7 @@ mod quote; mod concat_idents; mod helpers; mod module; +mod pin_data; mod vtable; use proc_macro::TokenStream; @@ -168,3 +169,31 @@ pub fn vtable(attr: TokenStream, ts: TokenStream) -> TokenStream { pub fn concat_idents(ts: TokenStream) -> TokenStream { concat_idents::concat_idents(ts) } + +/// Used to specify the pinning information of the fields of a struct. +/// +/// This is somewhat similar in purpose as +/// [pin-project-lite](https://crates.io/crates/pin-project-lite). +/// Place this macro on a struct definition and then `#[pin]` in front of the attributes of each +/// field you want to structurally pin. +/// +/// This macro enables the use of the [`pin_init!`] macro. When pin-initializing a `struct`, +/// then `#[pin]` directs the type of initializer that is required. +/// +/// # Examples +/// +/// ```rust,ignore +/// #[pin_data] +/// struct DriverData { +/// #[pin] +/// queue: Mutex>, +/// buf: Box<[u8; 1024 * 1024]>, +/// } +/// ``` +/// +/// [`pin_init!`]: ../kernel/macro.pin_init.html +// ^ cannot use direct link, since `kernel` is not a dependency of `macros`. +#[proc_macro_attribute] +pub fn pin_data(inner: TokenStream, item: TokenStream) -> TokenStream { + pin_data::pin_data(inner, item) +} diff --git a/rust/macros/pin_data.rs b/rust/macros/pin_data.rs new file mode 100644 index 000000000000..954149d77181 --- /dev/null +++ b/rust/macros/pin_data.rs @@ -0,0 +1,79 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +use proc_macro::{Punct, Spacing, TokenStream, TokenTree}; + +pub(crate) fn pin_data(args: TokenStream, input: TokenStream) -> TokenStream { + // This proc-macro only does some pre-parsing and then delegates the actual parsing to + // `kernel::__pin_data!`. + // + // In here we only collect the generics, since parsing them in declarative macros is very + // elaborate. We also do not need to analyse their structure, we only need to collect them. + + // `impl_generics`, the declared generics with their bounds. + let mut impl_generics = vec![]; + // Only the names of the generics, without any bounds. + let mut ty_generics = vec![]; + // Tokens not related to the generics e.g. the `impl` token. + let mut rest = vec![]; + // The current level of `<`. + let mut nesting = 0; + let mut toks = input.into_iter(); + // If we are at the beginning of a generic parameter. + let mut at_start = true; + for tt in &mut toks { + match tt.clone() { + TokenTree::Punct(p) if p.as_char() == '<' => { + if nesting >= 1 { + impl_generics.push(tt); + } + nesting += 1; + } + TokenTree::Punct(p) if p.as_char() == '>' => { + if nesting == 0 { + break; + } else { + nesting -= 1; + if nesting >= 1 { + impl_generics.push(tt); + } + if nesting == 0 { + break; + } + } + } + tt => { + if nesting == 1 { + match &tt { + TokenTree::Ident(i) if i.to_string() == "const" => {} + TokenTree::Ident(_) if at_start => { + ty_generics.push(tt.clone()); + ty_generics.push(TokenTree::Punct(Punct::new(',', Spacing::Alone))); + at_start = false; + } + TokenTree::Punct(p) if p.as_char() == ',' => at_start = true, + TokenTree::Punct(p) if p.as_char() == '\'' && at_start => { + ty_generics.push(tt.clone()); + } + _ => {} + } + } + if nesting >= 1 { + impl_generics.push(tt); + } else if nesting == 0 { + rest.push(tt); + } + } + } + } + rest.extend(toks); + // This should be the body of the struct `{...}`. + let last = rest.pop(); + quote!(::kernel::__pin_data! { + parse_input: + @args(#args), + @sig(#(#rest)*), + @impl_generics(#(#impl_generics)*), + @ty_generics(#(#ty_generics)*), + @body(#last), + }) +} diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs index 94a6277182ee..c8e08b3c1e4c 100644 --- a/rust/macros/quote.rs +++ b/rust/macros/quote.rs @@ -38,7 +38,6 @@ impl ToTokens for TokenStream { /// This is a similar to the /// [`quote_spanned!`](https://docs.rs/quote/latest/quote/macro.quote_spanned.html) macro from the /// `quote` crate but provides only just enough functionality needed by the current `macros` crate. -#[allow(unused_macros)] macro_rules! quote_spanned { ($span:expr => $($tt:tt)*) => { #[allow(clippy::vec_init_then_push)] @@ -137,7 +136,6 @@ macro_rules! quote_spanned { /// `macros` crate. /// /// [`Span::mixed_site()`]: https://doc.rust-lang.org/proc_macro/struct.Span.html#method.mixed_site -#[allow(unused_macros)] macro_rules! quote { ($($tt:tt)*) => { quote_spanned!(::proc_macro::Span::mixed_site() => $($tt)*) -- cgit v1.2.1