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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);