1// SPDX-License-Identifier: Apache-2.0 OR MIT
   2
   3//! API to safely and fallibly initialize pinned `struct`s using in-place constructors.
   4//!
   5//! It also allows in-place initialization of big `struct`s that would otherwise produce a stack
   6//! overflow.
   7//!
   8//! Most `struct`s from the [`sync`] module need to be pinned, because they contain self-referential
   9//! `struct`s from C. [Pinning][pinning] is Rust's way of ensuring data does not move.
  10//!
  11//! # Overview
  12//!
  13//! To initialize a `struct` with an in-place constructor you will need two things:
  14//! - an in-place constructor,
  15//! - a memory location that can hold your `struct` (this can be the [stack], an [`Arc<T>`],
  16//!   [`UniqueArc<T>`], [`Box<T>`] or any other smart pointer that implements [`InPlaceInit`]).
  17//!
  18//! To get an in-place constructor there are generally three options:
  19//! - directly creating an in-place constructor using the [`pin_init!`] macro,
  20//! - a custom function/macro returning an in-place constructor provided by someone else,
  21//! - using the unsafe function [`pin_init_from_closure()`] to manually create an initializer.
  22//!
  23//! Aside from pinned initialization, this API also supports in-place construction without pinning,
  24//! the macros/types/functions are generally named like the pinned variants without the `pin`
  25//! prefix.
  26//!
  27//! # Examples
  28//!
  29//! ## Using the [`pin_init!`] macro
  30//!
  31//! If you want to use [`PinInit`], then you will have to annotate your `struct` with
  32//! `#[`[`pin_data`]`]`. It is a macro that uses `#[pin]` as a marker for
  33//! [structurally pinned fields]. After doing this, you can then create an in-place constructor via
  34//! [`pin_init!`]. The syntax is almost the same as normal `struct` initializers. The difference is
  35//! that you need to write `<-` instead of `:` for fields that you want to initialize in-place.
  36//!
  37//! ```rust
  38//! # #![allow(clippy::disallowed_names)]
  39//! use kernel::{prelude::*, sync::Mutex, new_mutex};
  40//! # use core::pin::Pin;
  41//! #[pin_data]
  42//! struct Foo {
  43//!     #[pin]
  44//!     a: Mutex<usize>,
  45//!     b: u32,
  46//! }
  47//!
  48//! let foo = pin_init!(Foo {
  49//!     a <- new_mutex!(42, "Foo::a"),
  50//!     b: 24,
  51//! });
  52//! ```
  53//!
  54//! `foo` now is of the type [`impl PinInit<Foo>`]. We can now use any smart pointer that we like
  55//! (or just the stack) to actually initialize a `Foo`:
  56//!
  57//! ```rust
  58//! # #![allow(clippy::disallowed_names)]
  59//! # use kernel::{prelude::*, sync::Mutex, new_mutex};
  60//! # use core::pin::Pin;
  61//! # #[pin_data]
  62//! # struct Foo {
  63//! #     #[pin]
  64//! #     a: Mutex<usize>,
  65//! #     b: u32,
  66//! # }
  67//! # let foo = pin_init!(Foo {
  68//! #     a <- new_mutex!(42, "Foo::a"),
  69//! #     b: 24,
  70//! # });
  71//! let foo: Result<Pin<Box<Foo>>> = Box::pin_init(foo);
  72//! ```
  73//!
  74//! For more information see the [`pin_init!`] macro.
  75//!
  76//! ## Using a custom function/macro that returns an initializer
  77//!
  78//! Many types from the kernel supply a function/macro that returns an initializer, because the
  79//! above method only works for types where you can access the fields.
  80//!
  81//! ```rust
  82//! # use kernel::{new_mutex, sync::{Arc, Mutex}};
  83//! let mtx: Result<Arc<Mutex<usize>>> = Arc::pin_init(new_mutex!(42, "example::mtx"));
 
  84//! ```
  85//!
  86//! To declare an init macro/function you just return an [`impl PinInit<T, E>`]:
  87//!
  88//! ```rust
  89//! # #![allow(clippy::disallowed_names)]
  90//! # use kernel::{sync::Mutex, prelude::*, new_mutex, init::PinInit, try_pin_init};
  91//! #[pin_data]
  92//! struct DriverData {
  93//!     #[pin]
  94//!     status: Mutex<i32>,
  95//!     buffer: Box<[u8; 1_000_000]>,
  96//! }
  97//!
  98//! impl DriverData {
  99//!     fn new() -> impl PinInit<Self, Error> {
 100//!         try_pin_init!(Self {
 101//!             status <- new_mutex!(0, "DriverData::status"),
 102//!             buffer: Box::init(kernel::init::zeroed())?,
 103//!         })
 104//!     }
 105//! }
 106//! ```
 107//!
 108//! ## Manual creation of an initializer
 109//!
 110//! Often when working with primitives the previous approaches are not sufficient. That is where
 111//! [`pin_init_from_closure()`] comes in. This `unsafe` function allows you to create a
 112//! [`impl PinInit<T, E>`] directly from a closure. Of course you have to ensure that the closure
 113//! actually does the initialization in the correct way. Here are the things to look out for
 114//! (we are calling the parameter to the closure `slot`):
 115//! - when the closure returns `Ok(())`, then it has completed the initialization successfully, so
 116//!   `slot` now contains a valid bit pattern for the type `T`,
 117//! - when the closure returns `Err(e)`, then the caller may deallocate the memory at `slot`, so
 118//!   you need to take care to clean up anything if your initialization fails mid-way,
 119//! - you may assume that `slot` will stay pinned even after the closure returns until `drop` of
 120//!   `slot` gets called.
 121//!
 122//! ```rust
 123//! # #![allow(unreachable_pub, clippy::disallowed_names)]
 124//! use kernel::{prelude::*, init, types::Opaque};
 125//! use core::{ptr::addr_of_mut, marker::PhantomPinned, pin::Pin};
 126//! # mod bindings {
 127//! #     #![allow(non_camel_case_types)]
 
 128//! #     pub struct foo;
 129//! #     pub unsafe fn init_foo(_ptr: *mut foo) {}
 130//! #     pub unsafe fn destroy_foo(_ptr: *mut foo) {}
 131//! #     pub unsafe fn enable_foo(_ptr: *mut foo, _flags: u32) -> i32 { 0 }
 132//! # }
 133//! # // `Error::from_errno` is `pub(crate)` in the `kernel` crate, thus provide a workaround.
 134//! # trait FromErrno {
 135//! #     fn from_errno(errno: core::ffi::c_int) -> Error {
 136//! #         // Dummy error that can be constructed outside the `kernel` crate.
 137//! #         Error::from(core::fmt::Error)
 138//! #     }
 139//! # }
 140//! # impl FromErrno for Error {}
 141//! /// # Invariants
 142//! ///
 143//! /// `foo` is always initialized
 144//! #[pin_data(PinnedDrop)]
 145//! pub struct RawFoo {
 146//!     #[pin]
 147//!     foo: Opaque<bindings::foo>,
 148//!     #[pin]
 149//!     _p: PhantomPinned,
 150//! }
 151//!
 152//! impl RawFoo {
 153//!     pub fn new(flags: u32) -> impl PinInit<Self, Error> {
 154//!         // SAFETY:
 155//!         // - when the closure returns `Ok(())`, then it has successfully initialized and
 156//!         //   enabled `foo`,
 157//!         // - when it returns `Err(e)`, then it has cleaned up before
 158//!         unsafe {
 159//!             init::pin_init_from_closure(move |slot: *mut Self| {
 160//!                 // `slot` contains uninit memory, avoid creating a reference.
 161//!                 let foo = addr_of_mut!((*slot).foo);
 162//!
 163//!                 // Initialize the `foo`
 164//!                 bindings::init_foo(Opaque::raw_get(foo));
 165//!
 166//!                 // Try to enable it.
 167//!                 let err = bindings::enable_foo(Opaque::raw_get(foo), flags);
 168//!                 if err != 0 {
 169//!                     // Enabling has failed, first clean up the foo and then return the error.
 170//!                     bindings::destroy_foo(Opaque::raw_get(foo));
 171//!                     return Err(Error::from_errno(err));
 172//!                 }
 173//!
 174//!                 // All fields of `RawFoo` have been initialized, since `_p` is a ZST.
 175//!                 Ok(())
 176//!             })
 177//!         }
 178//!     }
 179//! }
 180//!
 181//! #[pinned_drop]
 182//! impl PinnedDrop for RawFoo {
 183//!     fn drop(self: Pin<&mut Self>) {
 184//!         // SAFETY: Since `foo` is initialized, destroying is safe.
 185//!         unsafe { bindings::destroy_foo(self.foo.get()) };
 186//!     }
 187//! }
 188//! ```
 189//!
 190//! For the special case where initializing a field is a single FFI-function call that cannot fail,
 191//! there exist the helper function [`Opaque::ffi_init`]. This function initialize a single
 192//! [`Opaque`] field by just delegating to the supplied closure. You can use these in combination
 193//! with [`pin_init!`].
 194//!
 195//! For more information on how to use [`pin_init_from_closure()`], take a look at the uses inside
 196//! the `kernel` crate. The [`sync`] module is a good starting point.
 197//!
 198//! [`sync`]: kernel::sync
 199//! [pinning]: https://doc.rust-lang.org/std/pin/index.html
 200//! [structurally pinned fields]:
 201//!     https://doc.rust-lang.org/std/pin/index.html#pinning-is-structural-for-field
 202//! [stack]: crate::stack_pin_init
 203//! [`Arc<T>`]: crate::sync::Arc
 204//! [`impl PinInit<Foo>`]: PinInit
 205//! [`impl PinInit<T, E>`]: PinInit
 206//! [`impl Init<T, E>`]: Init
 207//! [`Opaque`]: kernel::types::Opaque
 208//! [`Opaque::ffi_init`]: kernel::types::Opaque::ffi_init
 209//! [`pin_data`]: ::macros::pin_data
 210//! [`pin_init!`]: crate::pin_init!
 211
 212use crate::{
 
 213    error::{self, Error},
 
 214    sync::UniqueArc,
 215    types::{Opaque, ScopeGuard},
 216};
 217use alloc::boxed::Box;
 218use core::{
 219    alloc::AllocError,
 220    cell::UnsafeCell,
 221    convert::Infallible,
 222    marker::PhantomData,
 223    mem::MaybeUninit,
 224    num::*,
 225    pin::Pin,
 226    ptr::{self, NonNull},
 227};
 228
 229#[doc(hidden)]
 230pub mod __internal;
 231#[doc(hidden)]
 232pub mod macros;
 233
 234/// Initialize and pin a type directly on the stack.
 235///
 236/// # Examples
 237///
 238/// ```rust
 239/// # #![allow(clippy::disallowed_names)]
 240/// # use kernel::{init, macros::pin_data, pin_init, stack_pin_init, init::*, sync::Mutex, new_mutex};
 241/// # use core::pin::Pin;
 242/// #[pin_data]
 243/// struct Foo {
 244///     #[pin]
 245///     a: Mutex<usize>,
 246///     b: Bar,
 247/// }
 248///
 249/// #[pin_data]
 250/// struct Bar {
 251///     x: u32,
 252/// }
 253///
 254/// stack_pin_init!(let foo = pin_init!(Foo {
 255///     a <- new_mutex!(42),
 256///     b: Bar {
 257///         x: 64,
 258///     },
 259/// }));
 260/// let foo: Pin<&mut Foo> = foo;
 261/// pr_info!("a: {}", &*foo.a.lock());
 262/// ```
 263///
 264/// # Syntax
 265///
 266/// A normal `let` binding with optional type annotation. The expression is expected to implement
 267/// [`PinInit`]/[`Init`] with the error type [`Infallible`]. If you want to use a different error
 268/// type, then use [`stack_try_pin_init!`].
 269///
 270/// [`stack_try_pin_init!`]: crate::stack_try_pin_init!
 271#[macro_export]
 272macro_rules! stack_pin_init {
 273    (let $var:ident $(: $t:ty)? = $val:expr) => {
 274        let val = $val;
 275        let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
 276        let mut $var = match $crate::init::__internal::StackInit::init($var, val) {
 277            Ok(res) => res,
 278            Err(x) => {
 279                let x: ::core::convert::Infallible = x;
 280                match x {}
 281            }
 282        };
 283    };
 284}
 285
 286/// Initialize and pin a type directly on the stack.
 287///
 288/// # Examples
 289///
 290/// ```rust,ignore
 291/// # #![allow(clippy::disallowed_names)]
 292/// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
 293/// # use macros::pin_data;
 294/// # use core::{alloc::AllocError, pin::Pin};
 295/// #[pin_data]
 296/// struct Foo {
 297///     #[pin]
 298///     a: Mutex<usize>,
 299///     b: Box<Bar>,
 300/// }
 301///
 302/// struct Bar {
 303///     x: u32,
 304/// }
 305///
 306/// stack_try_pin_init!(let foo: Result<Pin<&mut Foo>, AllocError> = pin_init!(Foo {
 307///     a <- new_mutex!(42),
 308///     b: Box::try_new(Bar {
 309///         x: 64,
 310///     })?,
 311/// }));
 312/// let foo = foo.unwrap();
 313/// pr_info!("a: {}", &*foo.a.lock());
 314/// ```
 315///
 316/// ```rust,ignore
 317/// # #![allow(clippy::disallowed_names)]
 318/// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
 319/// # use macros::pin_data;
 320/// # use core::{alloc::AllocError, pin::Pin};
 321/// #[pin_data]
 322/// struct Foo {
 323///     #[pin]
 324///     a: Mutex<usize>,
 325///     b: Box<Bar>,
 326/// }
 327///
 328/// struct Bar {
 329///     x: u32,
 330/// }
 331///
 332/// stack_try_pin_init!(let foo: Pin<&mut Foo> =? pin_init!(Foo {
 333///     a <- new_mutex!(42),
 334///     b: Box::try_new(Bar {
 335///         x: 64,
 336///     })?,
 337/// }));
 338/// pr_info!("a: {}", &*foo.a.lock());
 339/// # Ok::<_, AllocError>(())
 340/// ```
 341///
 342/// # Syntax
 343///
 344/// A normal `let` binding with optional type annotation. The expression is expected to implement
 345/// [`PinInit`]/[`Init`]. This macro assigns a result to the given variable, adding a `?` after the
 346/// `=` will propagate this error.
 347#[macro_export]
 348macro_rules! stack_try_pin_init {
 349    (let $var:ident $(: $t:ty)? = $val:expr) => {
 350        let val = $val;
 351        let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
 352        let mut $var = $crate::init::__internal::StackInit::init($var, val);
 353    };
 354    (let $var:ident $(: $t:ty)? =? $val:expr) => {
 355        let val = $val;
 356        let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
 357        let mut $var = $crate::init::__internal::StackInit::init($var, val)?;
 358    };
 359}
 360
 361/// Construct an in-place, pinned initializer for `struct`s.
 362///
 363/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
 364/// [`try_pin_init!`].
 365///
 366/// The syntax is almost identical to that of a normal `struct` initializer:
 367///
 368/// ```rust
 369/// # #![allow(clippy::disallowed_names)]
 370/// # use kernel::{init, pin_init, macros::pin_data, init::*};
 371/// # use core::pin::Pin;
 372/// #[pin_data]
 373/// struct Foo {
 374///     a: usize,
 375///     b: Bar,
 376/// }
 377///
 378/// #[pin_data]
 379/// struct Bar {
 380///     x: u32,
 381/// }
 382///
 383/// # fn demo() -> impl PinInit<Foo> {
 384/// let a = 42;
 385///
 386/// let initializer = pin_init!(Foo {
 387///     a,
 388///     b: Bar {
 389///         x: 64,
 390///     },
 391/// });
 392/// # initializer }
 393/// # Box::pin_init(demo()).unwrap();
 394/// ```
 395///
 396/// Arbitrary Rust expressions can be used to set the value of a variable.
 397///
 398/// The fields are initialized in the order that they appear in the initializer. So it is possible
 399/// to read already initialized fields using raw pointers.
 400///
 401/// IMPORTANT: You are not allowed to create references to fields of the struct inside of the
 402/// initializer.
 403///
 404/// # Init-functions
 405///
 406/// When working with this API it is often desired to let others construct your types without
 407/// giving access to all fields. This is where you would normally write a plain function `new`
 408/// that would return a new instance of your type. With this API that is also possible.
 409/// However, there are a few extra things to keep in mind.
 410///
 411/// To create an initializer function, simply declare it like this:
 412///
 413/// ```rust
 414/// # #![allow(clippy::disallowed_names)]
 415/// # use kernel::{init, pin_init, prelude::*, init::*};
 416/// # use core::pin::Pin;
 417/// # #[pin_data]
 418/// # struct Foo {
 419/// #     a: usize,
 420/// #     b: Bar,
 421/// # }
 422/// # #[pin_data]
 423/// # struct Bar {
 424/// #     x: u32,
 425/// # }
 426/// impl Foo {
 427///     fn new() -> impl PinInit<Self> {
 428///         pin_init!(Self {
 429///             a: 42,
 430///             b: Bar {
 431///                 x: 64,
 432///             },
 433///         })
 434///     }
 435/// }
 436/// ```
 437///
 438/// Users of `Foo` can now create it like this:
 439///
 440/// ```rust
 441/// # #![allow(clippy::disallowed_names)]
 442/// # use kernel::{init, pin_init, macros::pin_data, init::*};
 443/// # use core::pin::Pin;
 444/// # #[pin_data]
 445/// # struct Foo {
 446/// #     a: usize,
 447/// #     b: Bar,
 448/// # }
 449/// # #[pin_data]
 450/// # struct Bar {
 451/// #     x: u32,
 452/// # }
 453/// # impl Foo {
 454/// #     fn new() -> impl PinInit<Self> {
 455/// #         pin_init!(Self {
 456/// #             a: 42,
 457/// #             b: Bar {
 458/// #                 x: 64,
 459/// #             },
 460/// #         })
 461/// #     }
 462/// # }
 463/// let foo = Box::pin_init(Foo::new());
 464/// ```
 465///
 466/// They can also easily embed it into their own `struct`s:
 467///
 468/// ```rust
 469/// # #![allow(clippy::disallowed_names)]
 470/// # use kernel::{init, pin_init, macros::pin_data, init::*};
 471/// # use core::pin::Pin;
 472/// # #[pin_data]
 473/// # struct Foo {
 474/// #     a: usize,
 475/// #     b: Bar,
 476/// # }
 477/// # #[pin_data]
 478/// # struct Bar {
 479/// #     x: u32,
 480/// # }
 481/// # impl Foo {
 482/// #     fn new() -> impl PinInit<Self> {
 483/// #         pin_init!(Self {
 484/// #             a: 42,
 485/// #             b: Bar {
 486/// #                 x: 64,
 487/// #             },
 488/// #         })
 489/// #     }
 490/// # }
 491/// #[pin_data]
 492/// struct FooContainer {
 493///     #[pin]
 494///     foo1: Foo,
 495///     #[pin]
 496///     foo2: Foo,
 497///     other: u32,
 498/// }
 499///
 500/// impl FooContainer {
 501///     fn new(other: u32) -> impl PinInit<Self> {
 502///         pin_init!(Self {
 503///             foo1 <- Foo::new(),
 504///             foo2 <- Foo::new(),
 505///             other,
 506///         })
 507///     }
 508/// }
 509/// ```
 510///
 511/// Here we see that when using `pin_init!` with `PinInit`, one needs to write `<-` instead of `:`.
 512/// This signifies that the given field is initialized in-place. As with `struct` initializers, just
 513/// writing the field (in this case `other`) without `:` or `<-` means `other: other,`.
 514///
 515/// # Syntax
 516///
 517/// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with
 518/// the following modifications is expected:
 519/// - Fields that you want to initialize in-place have to use `<-` instead of `:`.
 520/// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`]
 521///   pointer named `this` inside of the initializer.
 522/// - Using struct update syntax one can place `..Zeroable::zeroed()` at the very end of the
 523///   struct, this initializes every field with 0 and then runs all initializers specified in the
 524///   body. This can only be done if [`Zeroable`] is implemented for the struct.
 525///
 526/// For instance:
 527///
 528/// ```rust
 529/// # use kernel::{macros::{Zeroable, pin_data}, pin_init};
 530/// # use core::{ptr::addr_of_mut, marker::PhantomPinned};
 531/// #[pin_data]
 532/// #[derive(Zeroable)]
 533/// struct Buf {
 534///     // `ptr` points into `buf`.
 535///     ptr: *mut u8,
 536///     buf: [u8; 64],
 537///     #[pin]
 538///     pin: PhantomPinned,
 539/// }
 540/// pin_init!(&this in Buf {
 541///     buf: [0; 64],
 
 542///     ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() },
 543///     pin: PhantomPinned,
 544/// });
 545/// pin_init!(Buf {
 546///     buf: [1; 64],
 547///     ..Zeroable::zeroed()
 548/// });
 549/// ```
 550///
 551/// [`try_pin_init!`]: kernel::try_pin_init
 552/// [`NonNull<Self>`]: core::ptr::NonNull
 553// For a detailed example of how this macro works, see the module documentation of the hidden
 554// module `__internal` inside of `init/__internal.rs`.
 555#[macro_export]
 556macro_rules! pin_init {
 557    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 558        $($fields:tt)*
 559    }) => {
 560        $crate::__init_internal!(
 561            @this($($this)?),
 562            @typ($t $(::<$($generics),*>)?),
 563            @fields($($fields)*),
 564            @error(::core::convert::Infallible),
 565            @data(PinData, use_data),
 566            @has_data(HasPinData, __pin_data),
 567            @construct_closure(pin_init_from_closure),
 568            @munch_fields($($fields)*),
 569        )
 570    };
 571}
 572
 573/// Construct an in-place, fallible pinned initializer for `struct`s.
 574///
 575/// If the initialization can complete without error (or [`Infallible`]), then use [`pin_init!`].
 576///
 577/// You can use the `?` operator or use `return Err(err)` inside the initializer to stop
 578/// initialization and return the error.
 579///
 580/// IMPORTANT: if you have `unsafe` code inside of the initializer you have to ensure that when
 581/// initialization fails, the memory can be safely deallocated without any further modifications.
 582///
 583/// This macro defaults the error to [`Error`].
 584///
 585/// The syntax is identical to [`pin_init!`] with the following exception: you can append `? $type`
 586/// after the `struct` initializer to specify the error type you want to use.
 587///
 588/// # Examples
 589///
 590/// ```rust
 591/// # #![feature(new_uninit)]
 592/// use kernel::{init::{self, PinInit}, error::Error};
 593/// #[pin_data]
 594/// struct BigBuf {
 595///     big: Box<[u8; 1024 * 1024 * 1024]>,
 596///     small: [u8; 1024 * 1024],
 597///     ptr: *mut u8,
 598/// }
 599///
 600/// impl BigBuf {
 601///     fn new() -> impl PinInit<Self, Error> {
 602///         try_pin_init!(Self {
 603///             big: Box::init(init::zeroed())?,
 604///             small: [0; 1024 * 1024],
 605///             ptr: core::ptr::null_mut(),
 606///         }? Error)
 607///     }
 608/// }
 609/// ```
 610// For a detailed example of how this macro works, see the module documentation of the hidden
 611// module `__internal` inside of `init/__internal.rs`.
 612#[macro_export]
 613macro_rules! try_pin_init {
 614    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 615        $($fields:tt)*
 616    }) => {
 617        $crate::__init_internal!(
 618            @this($($this)?),
 619            @typ($t $(::<$($generics),*>)? ),
 620            @fields($($fields)*),
 621            @error($crate::error::Error),
 622            @data(PinData, use_data),
 623            @has_data(HasPinData, __pin_data),
 624            @construct_closure(pin_init_from_closure),
 625            @munch_fields($($fields)*),
 626        )
 627    };
 628    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 629        $($fields:tt)*
 630    }? $err:ty) => {
 631        $crate::__init_internal!(
 632            @this($($this)?),
 633            @typ($t $(::<$($generics),*>)? ),
 634            @fields($($fields)*),
 635            @error($err),
 636            @data(PinData, use_data),
 637            @has_data(HasPinData, __pin_data),
 638            @construct_closure(pin_init_from_closure),
 639            @munch_fields($($fields)*),
 640        )
 641    };
 642}
 643
 644/// Construct an in-place initializer for `struct`s.
 645///
 646/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
 647/// [`try_init!`].
 648///
 649/// The syntax is identical to [`pin_init!`] and its safety caveats also apply:
 650/// - `unsafe` code must guarantee either full initialization or return an error and allow
 651///   deallocation of the memory.
 652/// - the fields are initialized in the order given in the initializer.
 653/// - no references to fields are allowed to be created inside of the initializer.
 654///
 655/// This initializer is for initializing data in-place that might later be moved. If you want to
 656/// pin-initialize, use [`pin_init!`].
 657///
 658/// [`try_init!`]: crate::try_init!
 659// For a detailed example of how this macro works, see the module documentation of the hidden
 660// module `__internal` inside of `init/__internal.rs`.
 661#[macro_export]
 662macro_rules! init {
 663    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 664        $($fields:tt)*
 665    }) => {
 666        $crate::__init_internal!(
 667            @this($($this)?),
 668            @typ($t $(::<$($generics),*>)?),
 669            @fields($($fields)*),
 670            @error(::core::convert::Infallible),
 671            @data(InitData, /*no use_data*/),
 672            @has_data(HasInitData, __init_data),
 673            @construct_closure(init_from_closure),
 674            @munch_fields($($fields)*),
 675        )
 676    }
 677}
 678
 679/// Construct an in-place fallible initializer for `struct`s.
 680///
 681/// This macro defaults the error to [`Error`]. If you need [`Infallible`], then use
 682/// [`init!`].
 683///
 684/// The syntax is identical to [`try_pin_init!`]. If you want to specify a custom error,
 685/// append `? $type` after the `struct` initializer.
 686/// The safety caveats from [`try_pin_init!`] also apply:
 687/// - `unsafe` code must guarantee either full initialization or return an error and allow
 688///   deallocation of the memory.
 689/// - the fields are initialized in the order given in the initializer.
 690/// - no references to fields are allowed to be created inside of the initializer.
 691///
 692/// # Examples
 693///
 694/// ```rust
 695/// use kernel::{init::{PinInit, zeroed}, error::Error};
 696/// struct BigBuf {
 697///     big: Box<[u8; 1024 * 1024 * 1024]>,
 698///     small: [u8; 1024 * 1024],
 699/// }
 700///
 701/// impl BigBuf {
 702///     fn new() -> impl Init<Self, Error> {
 703///         try_init!(Self {
 704///             big: Box::init(zeroed())?,
 705///             small: [0; 1024 * 1024],
 706///         }? Error)
 707///     }
 708/// }
 709/// ```
 710// For a detailed example of how this macro works, see the module documentation of the hidden
 711// module `__internal` inside of `init/__internal.rs`.
 712#[macro_export]
 713macro_rules! try_init {
 714    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 715        $($fields:tt)*
 716    }) => {
 717        $crate::__init_internal!(
 718            @this($($this)?),
 719            @typ($t $(::<$($generics),*>)?),
 720            @fields($($fields)*),
 721            @error($crate::error::Error),
 722            @data(InitData, /*no use_data*/),
 723            @has_data(HasInitData, __init_data),
 724            @construct_closure(init_from_closure),
 725            @munch_fields($($fields)*),
 726        )
 727    };
 728    ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
 729        $($fields:tt)*
 730    }? $err:ty) => {
 731        $crate::__init_internal!(
 732            @this($($this)?),
 733            @typ($t $(::<$($generics),*>)?),
 734            @fields($($fields)*),
 735            @error($err),
 736            @data(InitData, /*no use_data*/),
 737            @has_data(HasInitData, __init_data),
 738            @construct_closure(init_from_closure),
 739            @munch_fields($($fields)*),
 740        )
 741    };
 742}
 743
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 744/// A pin-initializer for the type `T`.
 745///
 746/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
 747/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
 748/// [`InPlaceInit::pin_init`] function of a smart pointer like [`Arc<T>`] on this.
 749///
 750/// Also see the [module description](self).
 751///
 752/// # Safety
 753///
 754/// When implementing this type you will need to take great care. Also there are probably very few
 755/// cases where a manual implementation is necessary. Use [`pin_init_from_closure`] where possible.
 756///
 757/// The [`PinInit::__pinned_init`] function
 758/// - returns `Ok(())` if it initialized every field of `slot`,
 759/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
 760///     - `slot` can be deallocated without UB occurring,
 761///     - `slot` does not need to be dropped,
 762///     - `slot` is not partially initialized.
 763/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
 764///
 765/// [`Arc<T>`]: crate::sync::Arc
 766/// [`Arc::pin_init`]: crate::sync::Arc::pin_init
 767#[must_use = "An initializer must be used in order to create its value."]
 768pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
 769    /// Initializes `slot`.
 770    ///
 771    /// # Safety
 772    ///
 773    /// - `slot` is a valid pointer to uninitialized memory.
 774    /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
 775    ///   deallocate.
 776    /// - `slot` will not move until it is dropped, i.e. it will be pinned.
 777    unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E>;
 778
 779    /// First initializes the value using `self` then calls the function `f` with the initialized
 780    /// value.
 781    ///
 782    /// If `f` returns an error the value is dropped and the initializer will forward the error.
 783    ///
 784    /// # Examples
 785    ///
 786    /// ```rust
 787    /// # #![allow(clippy::disallowed_names)]
 788    /// use kernel::{types::Opaque, init::pin_init_from_closure};
 789    /// #[repr(C)]
 790    /// struct RawFoo([u8; 16]);
 791    /// extern {
 792    ///     fn init_foo(_: *mut RawFoo);
 793    /// }
 794    ///
 795    /// #[pin_data]
 796    /// struct Foo {
 797    ///     #[pin]
 798    ///     raw: Opaque<RawFoo>,
 799    /// }
 800    ///
 801    /// impl Foo {
 802    ///     fn setup(self: Pin<&mut Self>) {
 803    ///         pr_info!("Setting up foo");
 804    ///     }
 805    /// }
 806    ///
 807    /// let foo = pin_init!(Foo {
 
 808    ///     raw <- unsafe {
 809    ///         Opaque::ffi_init(|s| {
 810    ///             init_foo(s);
 811    ///         })
 812    ///     },
 813    /// }).pin_chain(|foo| {
 814    ///     foo.setup();
 815    ///     Ok(())
 816    /// });
 817    /// ```
 818    fn pin_chain<F>(self, f: F) -> ChainPinInit<Self, F, T, E>
 819    where
 820        F: FnOnce(Pin<&mut T>) -> Result<(), E>,
 821    {
 822        ChainPinInit(self, f, PhantomData)
 823    }
 824}
 825
 826/// An initializer returned by [`PinInit::pin_chain`].
 827pub struct ChainPinInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
 828
 829// SAFETY: The `__pinned_init` function is implemented such that it
 830// - returns `Ok(())` on successful initialization,
 831// - returns `Err(err)` on error and in this case `slot` will be dropped.
 832// - considers `slot` pinned.
 833unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainPinInit<I, F, T, E>
 834where
 835    I: PinInit<T, E>,
 836    F: FnOnce(Pin<&mut T>) -> Result<(), E>,
 837{
 838    unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
 839        // SAFETY: All requirements fulfilled since this function is `__pinned_init`.
 840        unsafe { self.0.__pinned_init(slot)? };
 841        // SAFETY: The above call initialized `slot` and we still have unique access.
 842        let val = unsafe { &mut *slot };
 843        // SAFETY: `slot` is considered pinned.
 844        let val = unsafe { Pin::new_unchecked(val) };
 845        (self.1)(val).map_err(|e| {
 846            // SAFETY: `slot` was initialized above.
 847            unsafe { core::ptr::drop_in_place(slot) };
 848            e
 849        })
 850    }
 851}
 852
 853/// An initializer for `T`.
 854///
 855/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
 856/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
 857/// [`InPlaceInit::init`] function of a smart pointer like [`Arc<T>`] on this. Because
 858/// [`PinInit<T, E>`] is a super trait, you can use every function that takes it as well.
 859///
 860/// Also see the [module description](self).
 861///
 862/// # Safety
 863///
 864/// When implementing this type you will need to take great care. Also there are probably very few
 865/// cases where a manual implementation is necessary. Use [`init_from_closure`] where possible.
 866///
 867/// The [`Init::__init`] function
 868/// - returns `Ok(())` if it initialized every field of `slot`,
 869/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
 870///     - `slot` can be deallocated without UB occurring,
 871///     - `slot` does not need to be dropped,
 872///     - `slot` is not partially initialized.
 873/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
 874///
 875/// The `__pinned_init` function from the supertrait [`PinInit`] needs to execute the exact same
 876/// code as `__init`.
 877///
 878/// Contrary to its supertype [`PinInit<T, E>`] the caller is allowed to
 879/// move the pointee after initialization.
 880///
 881/// [`Arc<T>`]: crate::sync::Arc
 882#[must_use = "An initializer must be used in order to create its value."]
 883pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
 884    /// Initializes `slot`.
 885    ///
 886    /// # Safety
 887    ///
 888    /// - `slot` is a valid pointer to uninitialized memory.
 889    /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
 890    ///   deallocate.
 891    unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
 892
 893    /// First initializes the value using `self` then calls the function `f` with the initialized
 894    /// value.
 895    ///
 896    /// If `f` returns an error the value is dropped and the initializer will forward the error.
 897    ///
 898    /// # Examples
 899    ///
 900    /// ```rust
 901    /// # #![allow(clippy::disallowed_names)]
 902    /// use kernel::{types::Opaque, init::{self, init_from_closure}};
 903    /// struct Foo {
 904    ///     buf: [u8; 1_000_000],
 905    /// }
 906    ///
 907    /// impl Foo {
 908    ///     fn setup(&mut self) {
 909    ///         pr_info!("Setting up foo");
 910    ///     }
 911    /// }
 912    ///
 913    /// let foo = init!(Foo {
 914    ///     buf <- init::zeroed()
 915    /// }).chain(|foo| {
 916    ///     foo.setup();
 917    ///     Ok(())
 918    /// });
 919    /// ```
 920    fn chain<F>(self, f: F) -> ChainInit<Self, F, T, E>
 921    where
 922        F: FnOnce(&mut T) -> Result<(), E>,
 923    {
 924        ChainInit(self, f, PhantomData)
 925    }
 926}
 927
 928/// An initializer returned by [`Init::chain`].
 929pub struct ChainInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
 930
 931// SAFETY: The `__init` function is implemented such that it
 932// - returns `Ok(())` on successful initialization,
 933// - returns `Err(err)` on error and in this case `slot` will be dropped.
 934unsafe impl<T: ?Sized, E, I, F> Init<T, E> for ChainInit<I, F, T, E>
 935where
 936    I: Init<T, E>,
 937    F: FnOnce(&mut T) -> Result<(), E>,
 938{
 939    unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
 940        // SAFETY: All requirements fulfilled since this function is `__init`.
 941        unsafe { self.0.__pinned_init(slot)? };
 942        // SAFETY: The above call initialized `slot` and we still have unique access.
 943        (self.1)(unsafe { &mut *slot }).map_err(|e| {
 944            // SAFETY: `slot` was initialized above.
 945            unsafe { core::ptr::drop_in_place(slot) };
 946            e
 947        })
 948    }
 949}
 950
 951// SAFETY: `__pinned_init` behaves exactly the same as `__init`.
 952unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainInit<I, F, T, E>
 953where
 954    I: Init<T, E>,
 955    F: FnOnce(&mut T) -> Result<(), E>,
 956{
 957    unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
 958        // SAFETY: `__init` has less strict requirements compared to `__pinned_init`.
 959        unsafe { self.__init(slot) }
 960    }
 961}
 962
 963/// Creates a new [`PinInit<T, E>`] from the given closure.
 964///
 965/// # Safety
 966///
 967/// The closure:
 968/// - returns `Ok(())` if it initialized every field of `slot`,
 969/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
 970///     - `slot` can be deallocated without UB occurring,
 971///     - `slot` does not need to be dropped,
 972///     - `slot` is not partially initialized.
 973/// - may assume that the `slot` does not move if `T: !Unpin`,
 974/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
 975#[inline]
 976pub const unsafe fn pin_init_from_closure<T: ?Sized, E>(
 977    f: impl FnOnce(*mut T) -> Result<(), E>,
 978) -> impl PinInit<T, E> {
 979    __internal::InitClosure(f, PhantomData)
 980}
 981
 982/// Creates a new [`Init<T, E>`] from the given closure.
 983///
 984/// # Safety
 985///
 986/// The closure:
 987/// - returns `Ok(())` if it initialized every field of `slot`,
 988/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
 989///     - `slot` can be deallocated without UB occurring,
 990///     - `slot` does not need to be dropped,
 991///     - `slot` is not partially initialized.
 992/// - the `slot` may move after initialization.
 993/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
 994#[inline]
 995pub const unsafe fn init_from_closure<T: ?Sized, E>(
 996    f: impl FnOnce(*mut T) -> Result<(), E>,
 997) -> impl Init<T, E> {
 998    __internal::InitClosure(f, PhantomData)
 999}
1000
1001/// An initializer that leaves the memory uninitialized.
1002///
1003/// The initializer is a no-op. The `slot` memory is not changed.
1004#[inline]
1005pub fn uninit<T, E>() -> impl Init<MaybeUninit<T>, E> {
1006    // SAFETY: The memory is allowed to be uninitialized.
1007    unsafe { init_from_closure(|_| Ok(())) }
1008}
1009
1010/// Initializes an array by initializing each element via the provided initializer.
1011///
1012/// # Examples
1013///
1014/// ```rust
1015/// use kernel::{error::Error, init::init_array_from_fn};
1016/// let array: Box<[usize; 1_000]>= Box::init::<Error>(init_array_from_fn(|i| i)).unwrap();
 
1017/// assert_eq!(array.len(), 1_000);
1018/// ```
1019pub fn init_array_from_fn<I, const N: usize, T, E>(
1020    mut make_init: impl FnMut(usize) -> I,
1021) -> impl Init<[T; N], E>
1022where
1023    I: Init<T, E>,
1024{
1025    let init = move |slot: *mut [T; N]| {
1026        let slot = slot.cast::<T>();
1027        // Counts the number of initialized elements and when dropped drops that many elements from
1028        // `slot`.
1029        let mut init_count = ScopeGuard::new_with_data(0, |i| {
1030            // We now free every element that has been initialized before:
1031            // SAFETY: The loop initialized exactly the values from 0..i and since we
1032            // return `Err` below, the caller will consider the memory at `slot` as
1033            // uninitialized.
1034            unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1035        });
1036        for i in 0..N {
1037            let init = make_init(i);
1038            // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1039            let ptr = unsafe { slot.add(i) };
1040            // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1041            // requirements.
1042            unsafe { init.__init(ptr) }?;
1043            *init_count += 1;
1044        }
1045        init_count.dismiss();
1046        Ok(())
1047    };
1048    // SAFETY: The initializer above initializes every element of the array. On failure it drops
1049    // any initialized elements and returns `Err`.
1050    unsafe { init_from_closure(init) }
1051}
1052
1053/// Initializes an array by initializing each element via the provided initializer.
1054///
1055/// # Examples
1056///
1057/// ```rust
1058/// use kernel::{sync::{Arc, Mutex}, init::pin_init_array_from_fn, new_mutex};
1059/// let array: Arc<[Mutex<usize>; 1_000]>=
1060///     Arc::pin_init(pin_init_array_from_fn(|i| new_mutex!(i))).unwrap();
1061/// assert_eq!(array.len(), 1_000);
1062/// ```
1063pub fn pin_init_array_from_fn<I, const N: usize, T, E>(
1064    mut make_init: impl FnMut(usize) -> I,
1065) -> impl PinInit<[T; N], E>
1066where
1067    I: PinInit<T, E>,
1068{
1069    let init = move |slot: *mut [T; N]| {
1070        let slot = slot.cast::<T>();
1071        // Counts the number of initialized elements and when dropped drops that many elements from
1072        // `slot`.
1073        let mut init_count = ScopeGuard::new_with_data(0, |i| {
1074            // We now free every element that has been initialized before:
1075            // SAFETY: The loop initialized exactly the values from 0..i and since we
1076            // return `Err` below, the caller will consider the memory at `slot` as
1077            // uninitialized.
1078            unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1079        });
1080        for i in 0..N {
1081            let init = make_init(i);
1082            // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1083            let ptr = unsafe { slot.add(i) };
1084            // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1085            // requirements.
1086            unsafe { init.__pinned_init(ptr) }?;
1087            *init_count += 1;
1088        }
1089        init_count.dismiss();
1090        Ok(())
1091    };
1092    // SAFETY: The initializer above initializes every element of the array. On failure it drops
1093    // any initialized elements and returns `Err`.
1094    unsafe { pin_init_from_closure(init) }
1095}
1096
1097// SAFETY: Every type can be initialized by-value.
1098unsafe impl<T, E> Init<T, E> for T {
1099    unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
 
1100        unsafe { slot.write(self) };
1101        Ok(())
1102    }
1103}
1104
1105// SAFETY: Every type can be initialized by-value. `__pinned_init` calls `__init`.
1106unsafe impl<T, E> PinInit<T, E> for T {
1107    unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
 
1108        unsafe { self.__init(slot) }
1109    }
1110}
1111
1112/// Smart pointer that can initialize memory in-place.
1113pub trait InPlaceInit<T>: Sized {
 
 
 
 
 
 
1114    /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1115    /// type.
1116    ///
1117    /// If `T: !Unpin` it will not be able to move afterwards.
1118    fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
1119    where
1120        E: From<AllocError>;
1121
1122    /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1123    /// type.
1124    ///
1125    /// If `T: !Unpin` it will not be able to move afterwards.
1126    fn pin_init<E>(init: impl PinInit<T, E>) -> error::Result<Pin<Self>>
1127    where
1128        Error: From<E>,
1129    {
1130        // SAFETY: We delegate to `init` and only change the error type.
1131        let init = unsafe {
1132            pin_init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1133        };
1134        Self::try_pin_init(init)
1135    }
1136
1137    /// Use the given initializer to in-place initialize a `T`.
1138    fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
1139    where
1140        E: From<AllocError>;
1141
1142    /// Use the given initializer to in-place initialize a `T`.
1143    fn init<E>(init: impl Init<T, E>) -> error::Result<Self>
1144    where
1145        Error: From<E>,
1146    {
1147        // SAFETY: We delegate to `init` and only change the error type.
1148        let init = unsafe {
1149            init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1150        };
1151        Self::try_init(init)
1152    }
1153}
1154
1155impl<T> InPlaceInit<T> for Box<T> {
 
 
1156    #[inline]
1157    fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
1158    where
1159        E: From<AllocError>,
1160    {
1161        let mut this = Box::try_new_uninit()?;
1162        let slot = this.as_mut_ptr();
1163        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1164        // slot is valid and will not be moved, because we pin it later.
1165        unsafe { init.__pinned_init(slot)? };
1166        // SAFETY: All fields have been initialized.
1167        Ok(unsafe { this.assume_init() }.into())
1168    }
1169
1170    #[inline]
1171    fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
1172    where
1173        E: From<AllocError>,
1174    {
1175        let mut this = Box::try_new_uninit()?;
1176        let slot = this.as_mut_ptr();
1177        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1178        // slot is valid.
1179        unsafe { init.__init(slot)? };
1180        // SAFETY: All fields have been initialized.
1181        Ok(unsafe { this.assume_init() })
1182    }
1183}
1184
1185impl<T> InPlaceInit<T> for UniqueArc<T> {
 
 
1186    #[inline]
1187    fn try_pin_init<E>(init: impl PinInit<T, E>) -> Result<Pin<Self>, E>
1188    where
1189        E: From<AllocError>,
1190    {
1191        let mut this = UniqueArc::try_new_uninit()?;
1192        let slot = this.as_mut_ptr();
1193        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1194        // slot is valid and will not be moved, because we pin it later.
1195        unsafe { init.__pinned_init(slot)? };
1196        // SAFETY: All fields have been initialized.
1197        Ok(unsafe { this.assume_init() }.into())
1198    }
1199
1200    #[inline]
1201    fn try_init<E>(init: impl Init<T, E>) -> Result<Self, E>
1202    where
1203        E: From<AllocError>,
1204    {
1205        let mut this = UniqueArc::try_new_uninit()?;
1206        let slot = this.as_mut_ptr();
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1207        // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1208        // slot is valid.
1209        unsafe { init.__init(slot)? };
1210        // SAFETY: All fields have been initialized.
1211        Ok(unsafe { this.assume_init() })
 
 
 
 
 
 
 
 
 
1212    }
1213}
1214
1215/// Trait facilitating pinned destruction.
1216///
1217/// Use [`pinned_drop`] to implement this trait safely:
1218///
1219/// ```rust
1220/// # use kernel::sync::Mutex;
1221/// use kernel::macros::pinned_drop;
1222/// use core::pin::Pin;
1223/// #[pin_data(PinnedDrop)]
1224/// struct Foo {
1225///     #[pin]
1226///     mtx: Mutex<usize>,
1227/// }
1228///
1229/// #[pinned_drop]
1230/// impl PinnedDrop for Foo {
1231///     fn drop(self: Pin<&mut Self>) {
1232///         pr_info!("Foo is being dropped!");
1233///     }
1234/// }
1235/// ```
1236///
1237/// # Safety
1238///
1239/// This trait must be implemented via the [`pinned_drop`] proc-macro attribute on the impl.
1240///
1241/// [`pinned_drop`]: kernel::macros::pinned_drop
1242pub unsafe trait PinnedDrop: __internal::HasPinData {
1243    /// Executes the pinned destructor of this type.
1244    ///
1245    /// While this function is marked safe, it is actually unsafe to call it manually. For this
1246    /// reason it takes an additional parameter. This type can only be constructed by `unsafe` code
1247    /// and thus prevents this function from being called where it should not.
1248    ///
1249    /// This extra parameter will be generated by the `#[pinned_drop]` proc-macro attribute
1250    /// automatically.
1251    fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop);
1252}
1253
1254/// Marker trait for types that can be initialized by writing just zeroes.
1255///
1256/// # Safety
1257///
1258/// The bit pattern consisting of only zeroes is a valid bit pattern for this type. In other words,
1259/// this is not UB:
1260///
1261/// ```rust,ignore
1262/// let val: Self = unsafe { core::mem::zeroed() };
1263/// ```
1264pub unsafe trait Zeroable {}
1265
1266/// Create a new zeroed T.
1267///
1268/// The returned initializer will write `0x00` to every byte of the given `slot`.
1269#[inline]
1270pub fn zeroed<T: Zeroable>() -> impl Init<T> {
1271    // SAFETY: Because `T: Zeroable`, all bytes zero is a valid bit pattern for `T`
1272    // and because we write all zeroes, the memory is initialized.
1273    unsafe {
1274        init_from_closure(|slot: *mut T| {
1275            slot.write_bytes(0, 1);
1276            Ok(())
1277        })
1278    }
1279}
1280
1281macro_rules! impl_zeroable {
1282    ($($({$($generics:tt)*})? $t:ty, )*) => {
 
1283        $(unsafe impl$($($generics)*)? Zeroable for $t {})*
1284    };
1285}
1286
1287impl_zeroable! {
1288    // SAFETY: All primitives that are allowed to be zero.
1289    bool,
1290    char,
1291    u8, u16, u32, u64, u128, usize,
1292    i8, i16, i32, i64, i128, isize,
1293    f32, f64,
1294
1295    // SAFETY: These are ZSTs, there is nothing to zero.
1296    {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, Infallible, (),
 
 
 
 
 
 
 
1297
1298    // SAFETY: Type is allowed to take any value, including all zeros.
1299    {<T>} MaybeUninit<T>,
1300    // SAFETY: Type is allowed to take any value, including all zeros.
1301    {<T>} Opaque<T>,
1302
1303    // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.
1304    {<T: ?Sized + Zeroable>} UnsafeCell<T>,
1305
1306    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1307    Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
1308    Option<NonZeroU128>, Option<NonZeroUsize>,
1309    Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,
1310    Option<NonZeroI128>, Option<NonZeroIsize>,
1311
1312    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1313    //
1314    // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant.
1315    {<T: ?Sized>} Option<NonNull<T>>,
1316    {<T: ?Sized>} Option<Box<T>>,
1317
1318    // SAFETY: `null` pointer is valid.
1319    //
1320    // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be
1321    // null.
1322    //
1323    // When `Pointee` gets stabilized, we could use
1324    // `T: ?Sized where <T as Pointee>::Metadata: Zeroable`
1325    {<T>} *mut T, {<T>} *const T,
1326
1327    // SAFETY: `null` pointer is valid and the metadata part of these fat pointers is allowed to be
1328    // zero.
1329    {<T>} *mut [T], {<T>} *const [T], *mut str, *const str,
1330
1331    // SAFETY: `T` is `Zeroable`.
1332    {<const N: usize, T: Zeroable>} [T; N], {<T: Zeroable>} Wrapping<T>,
1333}
1334
1335macro_rules! impl_tuple_zeroable {
1336    ($(,)?) => {};
1337    ($first:ident, $($t:ident),* $(,)?) => {
1338        // SAFETY: All elements are zeroable and padding can be zero.
1339        unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {}
1340        impl_tuple_zeroable!($($t),* ,);
1341    }
1342}
1343
1344impl_tuple_zeroable!(A, B, C, D, E, F, G, H, I, J);