projects/linux·blob v6.11 · refs

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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::sync::{new_mutex, 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::sync::{new_mutex, 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, GFP_KERNEL);
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::sync::{new_mutex, Arc, Mutex};
83//! let mtx: Result<Arc<Mutex<usize>>> =
84//! Arc::pin_init(new_mutex!(42, "example::mtx"), GFP_KERNEL);
85//! ```
86//!
87//! To declare an init macro/function you just return an [`impl PinInit<T, E>`]:
88//!
89//! ```rust
90//! # #![allow(clippy::disallowed_names)]
91//! # use kernel::{sync::Mutex, new_mutex, init::PinInit, try_pin_init};
92//! #[pin_data]
93//! struct DriverData {
94//! #[pin]
95//! status: Mutex<i32>,
96//! buffer: Box<[u8; 1_000_000]>,
97//! }
98//!
99//! impl DriverData {
100//! fn new() -> impl PinInit<Self, Error> {
101//! try_pin_init!(Self {
102//! status <- new_mutex!(0, "DriverData::status"),
103//! buffer: Box::init(kernel::init::zeroed(), GFP_KERNEL)?,
104//! })
105//! }
106//! }
107//! ```
108//!
109//! ## Manual creation of an initializer
110//!
111//! Often when working with primitives the previous approaches are not sufficient. That is where
112//! [`pin_init_from_closure()`] comes in. This `unsafe` function allows you to create a
113//! [`impl PinInit<T, E>`] directly from a closure. Of course you have to ensure that the closure
114//! actually does the initialization in the correct way. Here are the things to look out for
115//! (we are calling the parameter to the closure `slot`):
116//! - when the closure returns `Ok(())`, then it has completed the initialization successfully, so
117//! `slot` now contains a valid bit pattern for the type `T`,
118//! - when the closure returns `Err(e)`, then the caller may deallocate the memory at `slot`, so
119//! you need to take care to clean up anything if your initialization fails mid-way,
120//! - you may assume that `slot` will stay pinned even after the closure returns until `drop` of
121//! `slot` gets called.
122//!
123//! ```rust
124//! # #![allow(unreachable_pub, clippy::disallowed_names)]
125//! use kernel::{init, types::Opaque};
126//! use core::{ptr::addr_of_mut, marker::PhantomPinned, pin::Pin};
127//! # mod bindings {
128//! # #![allow(non_camel_case_types)]
129//! # pub struct foo;
130//! # pub unsafe fn init_foo(_ptr: *mut foo) {}
131//! # pub unsafe fn destroy_foo(_ptr: *mut foo) {}
132//! # pub unsafe fn enable_foo(_ptr: *mut foo, _flags: u32) -> i32 { 0 }
133//! # }
134//! # // `Error::from_errno` is `pub(crate)` in the `kernel` crate, thus provide a workaround.
135//! # trait FromErrno {
136//! # fn from_errno(errno: core::ffi::c_int) -> Error {
137//! # // Dummy error that can be constructed outside the `kernel` crate.
138//! # Error::from(core::fmt::Error)
139//! # }
140//! # }
141//! # impl FromErrno for Error {}
142//! /// # Invariants
143//! ///
144//! /// `foo` is always initialized
145//! #[pin_data(PinnedDrop)]
146//! pub struct RawFoo {
147//! #[pin]
148//! foo: Opaque<bindings::foo>,
149//! #[pin]
150//! _p: PhantomPinned,
151//! }
152//!
153//! impl RawFoo {
154//! pub fn new(flags: u32) -> impl PinInit<Self, Error> {
155//! // SAFETY:
156//! // - when the closure returns `Ok(())`, then it has successfully initialized and
157//! // enabled `foo`,
158//! // - when it returns `Err(e)`, then it has cleaned up before
159//! unsafe {
160//! init::pin_init_from_closure(move |slot: *mut Self| {
161//! // `slot` contains uninit memory, avoid creating a reference.
162//! let foo = addr_of_mut!((*slot).foo);
163//!
164//! // Initialize the `foo`
165//! bindings::init_foo(Opaque::raw_get(foo));
166//!
167//! // Try to enable it.
168//! let err = bindings::enable_foo(Opaque::raw_get(foo), flags);
169//! if err != 0 {
170//! // Enabling has failed, first clean up the foo and then return the error.
171//! bindings::destroy_foo(Opaque::raw_get(foo));
172//! return Err(Error::from_errno(err));
173//! }
174//!
175//! // All fields of `RawFoo` have been initialized, since `_p` is a ZST.
176//! Ok(())
177//! })
178//! }
179//! }
180//! }
181//!
182//! #[pinned_drop]
183//! impl PinnedDrop for RawFoo {
184//! fn drop(self: Pin<&mut Self>) {
185//! // SAFETY: Since `foo` is initialized, destroying is safe.
186//! unsafe { bindings::destroy_foo(self.foo.get()) };
187//! }
188//! }
189//! ```
190//!
191//! For the special case where initializing a field is a single FFI-function call that cannot fail,
192//! there exist the helper function [`Opaque::ffi_init`]. This function initialize a single
193//! [`Opaque`] field by just delegating to the supplied closure. You can use these in combination
194//! with [`pin_init!`].
195//!
196//! For more information on how to use [`pin_init_from_closure()`], take a look at the uses inside
197//! the `kernel` crate. The [`sync`] module is a good starting point.
198//!
199//! [`sync`]: kernel::sync
200//! [pinning]: https://doc.rust-lang.org/std/pin/index.html
201//! [structurally pinned fields]:
202//! https://doc.rust-lang.org/std/pin/index.html#pinning-is-structural-for-field
203//! [stack]: crate::stack_pin_init
204//! [`Arc<T>`]: crate::sync::Arc
205//! [`impl PinInit<Foo>`]: PinInit
206//! [`impl PinInit<T, E>`]: PinInit
207//! [`impl Init<T, E>`]: Init
208//! [`Opaque`]: kernel::types::Opaque
209//! [`Opaque::ffi_init`]: kernel::types::Opaque::ffi_init
210//! [`pin_data`]: ::macros::pin_data
211//! [`pin_init!`]: crate::pin_init!
212
213use crate::{
214 alloc::{box_ext::BoxExt, AllocError, Flags},
215 error::{self, Error},
216 sync::UniqueArc,
217 types::{Opaque, ScopeGuard},
218};
219use alloc::boxed::Box;
220use core::{
221 cell::UnsafeCell,
222 convert::Infallible,
223 marker::PhantomData,
224 mem::MaybeUninit,
225 num::*,
226 pin::Pin,
227 ptr::{self, NonNull},
228};
229
230#[doc(hidden)]
231pub mod __internal;
232#[doc(hidden)]
233pub mod macros;
234
235/// Initialize and pin a type directly on the stack.
236///
237/// # Examples
238///
239/// ```rust
240/// # #![allow(clippy::disallowed_names)]
241/// # use kernel::{init, macros::pin_data, pin_init, stack_pin_init, init::*, sync::Mutex, new_mutex};
242/// # use core::pin::Pin;
243/// #[pin_data]
244/// struct Foo {
245/// #[pin]
246/// a: Mutex<usize>,
247/// b: Bar,
248/// }
249///
250/// #[pin_data]
251/// struct Bar {
252/// x: u32,
253/// }
254///
255/// stack_pin_init!(let foo = pin_init!(Foo {
256/// a <- new_mutex!(42),
257/// b: Bar {
258/// x: 64,
259/// },
260/// }));
261/// let foo: Pin<&mut Foo> = foo;
262/// pr_info!("a: {}", &*foo.a.lock());
263/// ```
264///
265/// # Syntax
266///
267/// A normal `let` binding with optional type annotation. The expression is expected to implement
268/// [`PinInit`]/[`Init`] with the error type [`Infallible`]. If you want to use a different error
269/// type, then use [`stack_try_pin_init!`].
270///
271/// [`stack_try_pin_init!`]: crate::stack_try_pin_init!
272#[macro_export]
273macro_rules! stack_pin_init {
274 (let $var:ident $(: $t:ty)? = $val:expr) => {
275 let val = $val;
276 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
277 let mut $var = match $crate::init::__internal::StackInit::init($var, val) {
278 Ok(res) => res,
279 Err(x) => {
280 let x: ::core::convert::Infallible = x;
281 match x {}
282 }
283 };
284 };
285}
286
287/// Initialize and pin a type directly on the stack.
288///
289/// # Examples
290///
291/// ```rust,ignore
292/// # #![allow(clippy::disallowed_names)]
293/// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
294/// # use macros::pin_data;
295/// # use core::{alloc::AllocError, pin::Pin};
296/// #[pin_data]
297/// struct Foo {
298/// #[pin]
299/// a: Mutex<usize>,
300/// b: Box<Bar>,
301/// }
302///
303/// struct Bar {
304/// x: u32,
305/// }
306///
307/// stack_try_pin_init!(let foo: Result<Pin<&mut Foo>, AllocError> = pin_init!(Foo {
308/// a <- new_mutex!(42),
309/// b: Box::new(Bar {
310/// x: 64,
311/// }, GFP_KERNEL)?,
312/// }));
313/// let foo = foo.unwrap();
314/// pr_info!("a: {}", &*foo.a.lock());
315/// ```
316///
317/// ```rust,ignore
318/// # #![allow(clippy::disallowed_names)]
319/// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
320/// # use macros::pin_data;
321/// # use core::{alloc::AllocError, pin::Pin};
322/// #[pin_data]
323/// struct Foo {
324/// #[pin]
325/// a: Mutex<usize>,
326/// b: Box<Bar>,
327/// }
328///
329/// struct Bar {
330/// x: u32,
331/// }
332///
333/// stack_try_pin_init!(let foo: Pin<&mut Foo> =? pin_init!(Foo {
334/// a <- new_mutex!(42),
335/// b: Box::new(Bar {
336/// x: 64,
337/// }, GFP_KERNEL)?,
338/// }));
339/// pr_info!("a: {}", &*foo.a.lock());
340/// # Ok::<_, AllocError>(())
341/// ```
342///
343/// # Syntax
344///
345/// A normal `let` binding with optional type annotation. The expression is expected to implement
346/// [`PinInit`]/[`Init`]. This macro assigns a result to the given variable, adding a `?` after the
347/// `=` will propagate this error.
348#[macro_export]
349macro_rules! stack_try_pin_init {
350 (let $var:ident $(: $t:ty)? = $val:expr) => {
351 let val = $val;
352 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
353 let mut $var = $crate::init::__internal::StackInit::init($var, val);
354 };
355 (let $var:ident $(: $t:ty)? =? $val:expr) => {
356 let val = $val;
357 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
358 let mut $var = $crate::init::__internal::StackInit::init($var, val)?;
359 };
360}
361
362/// Construct an in-place, pinned initializer for `struct`s.
363///
364/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
365/// [`try_pin_init!`].
366///
367/// The syntax is almost identical to that of a normal `struct` initializer:
368///
369/// ```rust
370/// # #![allow(clippy::disallowed_names)]
371/// # use kernel::{init, pin_init, macros::pin_data, init::*};
372/// # use core::pin::Pin;
373/// #[pin_data]
374/// struct Foo {
375/// a: usize,
376/// b: Bar,
377/// }
378///
379/// #[pin_data]
380/// struct Bar {
381/// x: u32,
382/// }
383///
384/// # fn demo() -> impl PinInit<Foo> {
385/// let a = 42;
386///
387/// let initializer = pin_init!(Foo {
388/// a,
389/// b: Bar {
390/// x: 64,
391/// },
392/// });
393/// # initializer }
394/// # Box::pin_init(demo(), GFP_KERNEL).unwrap();
395/// ```
396///
397/// Arbitrary Rust expressions can be used to set the value of a variable.
398///
399/// The fields are initialized in the order that they appear in the initializer. So it is possible
400/// to read already initialized fields using raw pointers.
401///
402/// IMPORTANT: You are not allowed to create references to fields of the struct inside of the
403/// initializer.
404///
405/// # Init-functions
406///
407/// When working with this API it is often desired to let others construct your types without
408/// giving access to all fields. This is where you would normally write a plain function `new`
409/// that would return a new instance of your type. With this API that is also possible.
410/// However, there are a few extra things to keep in mind.
411///
412/// To create an initializer function, simply declare it like this:
413///
414/// ```rust
415/// # #![allow(clippy::disallowed_names)]
416/// # use kernel::{init, pin_init, init::*};
417/// # use core::pin::Pin;
418/// # #[pin_data]
419/// # struct Foo {
420/// # a: usize,
421/// # b: Bar,
422/// # }
423/// # #[pin_data]
424/// # struct Bar {
425/// # x: u32,
426/// # }
427/// impl Foo {
428/// fn new() -> impl PinInit<Self> {
429/// pin_init!(Self {
430/// a: 42,
431/// b: Bar {
432/// x: 64,
433/// },
434/// })
435/// }
436/// }
437/// ```
438///
439/// Users of `Foo` can now create it like this:
440///
441/// ```rust
442/// # #![allow(clippy::disallowed_names)]
443/// # use kernel::{init, pin_init, macros::pin_data, init::*};
444/// # use core::pin::Pin;
445/// # #[pin_data]
446/// # struct Foo {
447/// # a: usize,
448/// # b: Bar,
449/// # }
450/// # #[pin_data]
451/// # struct Bar {
452/// # x: u32,
453/// # }
454/// # impl Foo {
455/// # fn new() -> impl PinInit<Self> {
456/// # pin_init!(Self {
457/// # a: 42,
458/// # b: Bar {
459/// # x: 64,
460/// # },
461/// # })
462/// # }
463/// # }
464/// let foo = Box::pin_init(Foo::new(), GFP_KERNEL);
465/// ```
466///
467/// They can also easily embed it into their own `struct`s:
468///
469/// ```rust
470/// # #![allow(clippy::disallowed_names)]
471/// # use kernel::{init, pin_init, macros::pin_data, init::*};
472/// # use core::pin::Pin;
473/// # #[pin_data]
474/// # struct Foo {
475/// # a: usize,
476/// # b: Bar,
477/// # }
478/// # #[pin_data]
479/// # struct Bar {
480/// # x: u32,
481/// # }
482/// # impl Foo {
483/// # fn new() -> impl PinInit<Self> {
484/// # pin_init!(Self {
485/// # a: 42,
486/// # b: Bar {
487/// # x: 64,
488/// # },
489/// # })
490/// # }
491/// # }
492/// #[pin_data]
493/// struct FooContainer {
494/// #[pin]
495/// foo1: Foo,
496/// #[pin]
497/// foo2: Foo,
498/// other: u32,
499/// }
500///
501/// impl FooContainer {
502/// fn new(other: u32) -> impl PinInit<Self> {
503/// pin_init!(Self {
504/// foo1 <- Foo::new(),
505/// foo2 <- Foo::new(),
506/// other,
507/// })
508/// }
509/// }
510/// ```
511///
512/// Here we see that when using `pin_init!` with `PinInit`, one needs to write `<-` instead of `:`.
513/// This signifies that the given field is initialized in-place. As with `struct` initializers, just
514/// writing the field (in this case `other`) without `:` or `<-` means `other: other,`.
515///
516/// # Syntax
517///
518/// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with
519/// the following modifications is expected:
520/// - Fields that you want to initialize in-place have to use `<-` instead of `:`.
521/// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`]
522/// pointer named `this` inside of the initializer.
523/// - Using struct update syntax one can place `..Zeroable::zeroed()` at the very end of the
524/// struct, this initializes every field with 0 and then runs all initializers specified in the
525/// body. This can only be done if [`Zeroable`] is implemented for the struct.
526///
527/// For instance:
528///
529/// ```rust
530/// # use kernel::{macros::{Zeroable, pin_data}, pin_init};
531/// # use core::{ptr::addr_of_mut, marker::PhantomPinned};
532/// #[pin_data]
533/// #[derive(Zeroable)]
534/// struct Buf {
535/// // `ptr` points into `buf`.
536/// ptr: *mut u8,
537/// buf: [u8; 64],
538/// #[pin]
539/// pin: PhantomPinned,
540/// }
541/// pin_init!(&this in Buf {
542/// buf: [0; 64],
543/// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() },
544/// pin: PhantomPinned,
545/// });
546/// pin_init!(Buf {
547/// buf: [1; 64],
548/// ..Zeroable::zeroed()
549/// });
550/// ```
551///
552/// [`try_pin_init!`]: kernel::try_pin_init
553/// [`NonNull<Self>`]: core::ptr::NonNull
554// For a detailed example of how this macro works, see the module documentation of the hidden
555// module `__internal` inside of `init/__internal.rs`.
556#[macro_export]
557macro_rules! pin_init {
558 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
559 $($fields:tt)*
560 }) => {
561 $crate::__init_internal!(
562 @this($($this)?),
563 @typ($t $(::<$($generics),*>)?),
564 @fields($($fields)*),
565 @error(::core::convert::Infallible),
566 @data(PinData, use_data),
567 @has_data(HasPinData, __pin_data),
568 @construct_closure(pin_init_from_closure),
569 @munch_fields($($fields)*),
570 )
571 };
572}
573
574/// Construct an in-place, fallible pinned initializer for `struct`s.
575///
576/// If the initialization can complete without error (or [`Infallible`]), then use [`pin_init!`].
577///
578/// You can use the `?` operator or use `return Err(err)` inside the initializer to stop
579/// initialization and return the error.
580///
581/// IMPORTANT: if you have `unsafe` code inside of the initializer you have to ensure that when
582/// initialization fails, the memory can be safely deallocated without any further modifications.
583///
584/// This macro defaults the error to [`Error`].
585///
586/// The syntax is identical to [`pin_init!`] with the following exception: you can append `? $type`
587/// after the `struct` initializer to specify the error type you want to use.
588///
589/// # Examples
590///
591/// ```rust
592/// # #![feature(new_uninit)]
593/// use kernel::{init::{self, PinInit}, error::Error};
594/// #[pin_data]
595/// struct BigBuf {
596/// big: Box<[u8; 1024 * 1024 * 1024]>,
597/// small: [u8; 1024 * 1024],
598/// ptr: *mut u8,
599/// }
600///
601/// impl BigBuf {
602/// fn new() -> impl PinInit<Self, Error> {
603/// try_pin_init!(Self {
604/// big: Box::init(init::zeroed(), GFP_KERNEL)?,
605/// small: [0; 1024 * 1024],
606/// ptr: core::ptr::null_mut(),
607/// }? Error)
608/// }
609/// }
610/// ```
611// For a detailed example of how this macro works, see the module documentation of the hidden
612// module `__internal` inside of `init/__internal.rs`.
613#[macro_export]
614macro_rules! try_pin_init {
615 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
616 $($fields:tt)*
617 }) => {
618 $crate::__init_internal!(
619 @this($($this)?),
620 @typ($t $(::<$($generics),*>)? ),
621 @fields($($fields)*),
622 @error($crate::error::Error),
623 @data(PinData, use_data),
624 @has_data(HasPinData, __pin_data),
625 @construct_closure(pin_init_from_closure),
626 @munch_fields($($fields)*),
627 )
628 };
629 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
630 $($fields:tt)*
631 }? $err:ty) => {
632 $crate::__init_internal!(
633 @this($($this)?),
634 @typ($t $(::<$($generics),*>)? ),
635 @fields($($fields)*),
636 @error($err),
637 @data(PinData, use_data),
638 @has_data(HasPinData, __pin_data),
639 @construct_closure(pin_init_from_closure),
640 @munch_fields($($fields)*),
641 )
642 };
643}
644
645/// Construct an in-place initializer for `struct`s.
646///
647/// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
648/// [`try_init!`].
649///
650/// The syntax is identical to [`pin_init!`] and its safety caveats also apply:
651/// - `unsafe` code must guarantee either full initialization or return an error and allow
652/// deallocation of the memory.
653/// - the fields are initialized in the order given in the initializer.
654/// - no references to fields are allowed to be created inside of the initializer.
655///
656/// This initializer is for initializing data in-place that might later be moved. If you want to
657/// pin-initialize, use [`pin_init!`].
658///
659/// [`try_init!`]: crate::try_init!
660// For a detailed example of how this macro works, see the module documentation of the hidden
661// module `__internal` inside of `init/__internal.rs`.
662#[macro_export]
663macro_rules! init {
664 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
665 $($fields:tt)*
666 }) => {
667 $crate::__init_internal!(
668 @this($($this)?),
669 @typ($t $(::<$($generics),*>)?),
670 @fields($($fields)*),
671 @error(::core::convert::Infallible),
672 @data(InitData, /*no use_data*/),
673 @has_data(HasInitData, __init_data),
674 @construct_closure(init_from_closure),
675 @munch_fields($($fields)*),
676 )
677 }
678}
679
680/// Construct an in-place fallible initializer for `struct`s.
681///
682/// This macro defaults the error to [`Error`]. If you need [`Infallible`], then use
683/// [`init!`].
684///
685/// The syntax is identical to [`try_pin_init!`]. If you want to specify a custom error,
686/// append `? $type` after the `struct` initializer.
687/// The safety caveats from [`try_pin_init!`] also apply:
688/// - `unsafe` code must guarantee either full initialization or return an error and allow
689/// deallocation of the memory.
690/// - the fields are initialized in the order given in the initializer.
691/// - no references to fields are allowed to be created inside of the initializer.
692///
693/// # Examples
694///
695/// ```rust
696/// use kernel::{init::{PinInit, zeroed}, error::Error};
697/// struct BigBuf {
698/// big: Box<[u8; 1024 * 1024 * 1024]>,
699/// small: [u8; 1024 * 1024],
700/// }
701///
702/// impl BigBuf {
703/// fn new() -> impl Init<Self, Error> {
704/// try_init!(Self {
705/// big: Box::init(zeroed(), GFP_KERNEL)?,
706/// small: [0; 1024 * 1024],
707/// }? Error)
708/// }
709/// }
710/// ```
711// For a detailed example of how this macro works, see the module documentation of the hidden
712// module `__internal` inside of `init/__internal.rs`.
713#[macro_export]
714macro_rules! try_init {
715 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
716 $($fields:tt)*
717 }) => {
718 $crate::__init_internal!(
719 @this($($this)?),
720 @typ($t $(::<$($generics),*>)?),
721 @fields($($fields)*),
722 @error($crate::error::Error),
723 @data(InitData, /*no use_data*/),
724 @has_data(HasInitData, __init_data),
725 @construct_closure(init_from_closure),
726 @munch_fields($($fields)*),
727 )
728 };
729 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
730 $($fields:tt)*
731 }? $err:ty) => {
732 $crate::__init_internal!(
733 @this($($this)?),
734 @typ($t $(::<$($generics),*>)?),
735 @fields($($fields)*),
736 @error($err),
737 @data(InitData, /*no use_data*/),
738 @has_data(HasInitData, __init_data),
739 @construct_closure(init_from_closure),
740 @munch_fields($($fields)*),
741 )
742 };
743}
744
745/// A pin-initializer for the type `T`.
746///
747/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
748/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
749/// [`InPlaceInit::pin_init`] function of a smart pointer like [`Arc<T>`] on this.
750///
751/// Also see the [module description](self).
752///
753/// # Safety
754///
755/// When implementing this trait you will need to take great care. Also there are probably very few
756/// cases where a manual implementation is necessary. Use [`pin_init_from_closure`] where possible.
757///
758/// The [`PinInit::__pinned_init`] function:
759/// - returns `Ok(())` if it initialized every field of `slot`,
760/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
761/// - `slot` can be deallocated without UB occurring,
762/// - `slot` does not need to be dropped,
763/// - `slot` is not partially initialized.
764/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
765///
766/// [`Arc<T>`]: crate::sync::Arc
767/// [`Arc::pin_init`]: crate::sync::Arc::pin_init
768#[must_use = "An initializer must be used in order to create its value."]
769pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
770 /// Initializes `slot`.
771 ///
772 /// # Safety
773 ///
774 /// - `slot` is a valid pointer to uninitialized memory.
775 /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
776 /// deallocate.
777 /// - `slot` will not move until it is dropped, i.e. it will be pinned.
778 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E>;
779
780 /// First initializes the value using `self` then calls the function `f` with the initialized
781 /// value.
782 ///
783 /// If `f` returns an error the value is dropped and the initializer will forward the error.
784 ///
785 /// # Examples
786 ///
787 /// ```rust
788 /// # #![allow(clippy::disallowed_names)]
789 /// use kernel::{types::Opaque, init::pin_init_from_closure};
790 /// #[repr(C)]
791 /// struct RawFoo([u8; 16]);
792 /// extern {
793 /// fn init_foo(_: *mut RawFoo);
794 /// }
795 ///
796 /// #[pin_data]
797 /// struct Foo {
798 /// #[pin]
799 /// raw: Opaque<RawFoo>,
800 /// }
801 ///
802 /// impl Foo {
803 /// fn setup(self: Pin<&mut Self>) {
804 /// pr_info!("Setting up foo");
805 /// }
806 /// }
807 ///
808 /// let foo = pin_init!(Foo {
809 /// raw <- unsafe {
810 /// Opaque::ffi_init(|s| {
811 /// init_foo(s);
812 /// })
813 /// },
814 /// }).pin_chain(|foo| {
815 /// foo.setup();
816 /// Ok(())
817 /// });
818 /// ```
819 fn pin_chain<F>(self, f: F) -> ChainPinInit<Self, F, T, E>
820 where
821 F: FnOnce(Pin<&mut T>) -> Result<(), E>,
822 {
823 ChainPinInit(self, f, PhantomData)
824 }
825}
826
827/// An initializer returned by [`PinInit::pin_chain`].
828pub struct ChainPinInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
829
830// SAFETY: The `__pinned_init` function is implemented such that it
831// - returns `Ok(())` on successful initialization,
832// - returns `Err(err)` on error and in this case `slot` will be dropped.
833// - considers `slot` pinned.
834unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainPinInit<I, F, T, E>
835where
836 I: PinInit<T, E>,
837 F: FnOnce(Pin<&mut T>) -> Result<(), E>,
838{
839 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
840 // SAFETY: All requirements fulfilled since this function is `__pinned_init`.
841 unsafe { self.0.__pinned_init(slot)? };
842 // SAFETY: The above call initialized `slot` and we still have unique access.
843 let val = unsafe { &mut *slot };
844 // SAFETY: `slot` is considered pinned.
845 let val = unsafe { Pin::new_unchecked(val) };
846 // SAFETY: `slot` was initialized above.
847 (self.1)(val).inspect_err(|_| unsafe { core::ptr::drop_in_place(slot) })
848 }
849}
850
851/// An initializer for `T`.
852///
853/// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
854/// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
855/// [`InPlaceInit::init`] function of a smart pointer like [`Arc<T>`] on this. Because
856/// [`PinInit<T, E>`] is a super trait, you can use every function that takes it as well.
857///
858/// Also see the [module description](self).
859///
860/// # Safety
861///
862/// When implementing this trait you will need to take great care. Also there are probably very few
863/// cases where a manual implementation is necessary. Use [`init_from_closure`] where possible.
864///
865/// The [`Init::__init`] function:
866/// - returns `Ok(())` if it initialized every field of `slot`,
867/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
868/// - `slot` can be deallocated without UB occurring,
869/// - `slot` does not need to be dropped,
870/// - `slot` is not partially initialized.
871/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
872///
873/// The `__pinned_init` function from the supertrait [`PinInit`] needs to execute the exact same
874/// code as `__init`.
875///
876/// Contrary to its supertype [`PinInit<T, E>`] the caller is allowed to
877/// move the pointee after initialization.
878///
879/// [`Arc<T>`]: crate::sync::Arc
880#[must_use = "An initializer must be used in order to create its value."]
881pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
882 /// Initializes `slot`.
883 ///
884 /// # Safety
885 ///
886 /// - `slot` is a valid pointer to uninitialized memory.
887 /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
888 /// deallocate.
889 unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
890
891 /// First initializes the value using `self` then calls the function `f` with the initialized
892 /// value.
893 ///
894 /// If `f` returns an error the value is dropped and the initializer will forward the error.
895 ///
896 /// # Examples
897 ///
898 /// ```rust
899 /// # #![allow(clippy::disallowed_names)]
900 /// use kernel::{types::Opaque, init::{self, init_from_closure}};
901 /// struct Foo {
902 /// buf: [u8; 1_000_000],
903 /// }
904 ///
905 /// impl Foo {
906 /// fn setup(&mut self) {
907 /// pr_info!("Setting up foo");
908 /// }
909 /// }
910 ///
911 /// let foo = init!(Foo {
912 /// buf <- init::zeroed()
913 /// }).chain(|foo| {
914 /// foo.setup();
915 /// Ok(())
916 /// });
917 /// ```
918 fn chain<F>(self, f: F) -> ChainInit<Self, F, T, E>
919 where
920 F: FnOnce(&mut T) -> Result<(), E>,
921 {
922 ChainInit(self, f, PhantomData)
923 }
924}
925
926/// An initializer returned by [`Init::chain`].
927pub struct ChainInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
928
929// SAFETY: The `__init` function is implemented such that it
930// - returns `Ok(())` on successful initialization,
931// - returns `Err(err)` on error and in this case `slot` will be dropped.
932unsafe impl<T: ?Sized, E, I, F> Init<T, E> for ChainInit<I, F, T, E>
933where
934 I: Init<T, E>,
935 F: FnOnce(&mut T) -> Result<(), E>,
936{
937 unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
938 // SAFETY: All requirements fulfilled since this function is `__init`.
939 unsafe { self.0.__pinned_init(slot)? };
940 // SAFETY: The above call initialized `slot` and we still have unique access.
941 (self.1)(unsafe { &mut *slot }).inspect_err(|_|
942 // SAFETY: `slot` was initialized above.
943 unsafe { core::ptr::drop_in_place(slot) })
944 }
945}
946
947// SAFETY: `__pinned_init` behaves exactly the same as `__init`.
948unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainInit<I, F, T, E>
949where
950 I: Init<T, E>,
951 F: FnOnce(&mut T) -> Result<(), E>,
952{
953 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
954 // SAFETY: `__init` has less strict requirements compared to `__pinned_init`.
955 unsafe { self.__init(slot) }
956 }
957}
958
959/// Creates a new [`PinInit<T, E>`] from the given closure.
960///
961/// # Safety
962///
963/// The closure:
964/// - returns `Ok(())` if it initialized every field of `slot`,
965/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
966/// - `slot` can be deallocated without UB occurring,
967/// - `slot` does not need to be dropped,
968/// - `slot` is not partially initialized.
969/// - may assume that the `slot` does not move if `T: !Unpin`,
970/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
971#[inline]
972pub const unsafe fn pin_init_from_closure<T: ?Sized, E>(
973 f: impl FnOnce(*mut T) -> Result<(), E>,
974) -> impl PinInit<T, E> {
975 __internal::InitClosure(f, PhantomData)
976}
977
978/// Creates a new [`Init<T, E>`] from the given closure.
979///
980/// # Safety
981///
982/// The closure:
983/// - returns `Ok(())` if it initialized every field of `slot`,
984/// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
985/// - `slot` can be deallocated without UB occurring,
986/// - `slot` does not need to be dropped,
987/// - `slot` is not partially initialized.
988/// - the `slot` may move after initialization.
989/// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
990#[inline]
991pub const unsafe fn init_from_closure<T: ?Sized, E>(
992 f: impl FnOnce(*mut T) -> Result<(), E>,
993) -> impl Init<T, E> {
994 __internal::InitClosure(f, PhantomData)
995}
996
997/// An initializer that leaves the memory uninitialized.
998///
999/// The initializer is a no-op. The `slot` memory is not changed.
1000#[inline]
1001pub fn uninit<T, E>() -> impl Init<MaybeUninit<T>, E> {
1002 // SAFETY: The memory is allowed to be uninitialized.
1003 unsafe { init_from_closure(|_| Ok(())) }
1004}
1005
1006/// Initializes an array by initializing each element via the provided initializer.
1007///
1008/// # Examples
1009///
1010/// ```rust
1011/// use kernel::{error::Error, init::init_array_from_fn};
1012/// let array: Box<[usize; 1_000]> = Box::init::<Error>(init_array_from_fn(|i| i), GFP_KERNEL).unwrap();
1013/// assert_eq!(array.len(), 1_000);
1014/// ```
1015pub fn init_array_from_fn<I, const N: usize, T, E>(
1016 mut make_init: impl FnMut(usize) -> I,
1017) -> impl Init<[T; N], E>
1018where
1019 I: Init<T, E>,
1020{
1021 let init = move |slot: *mut [T; N]| {
1022 let slot = slot.cast::<T>();
1023 // Counts the number of initialized elements and when dropped drops that many elements from
1024 // `slot`.
1025 let mut init_count = ScopeGuard::new_with_data(0, |i| {
1026 // We now free every element that has been initialized before.
1027 // SAFETY: The loop initialized exactly the values from 0..i and since we
1028 // return `Err` below, the caller will consider the memory at `slot` as
1029 // uninitialized.
1030 unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1031 });
1032 for i in 0..N {
1033 let init = make_init(i);
1034 // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1035 let ptr = unsafe { slot.add(i) };
1036 // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1037 // requirements.
1038 unsafe { init.__init(ptr) }?;
1039 *init_count += 1;
1040 }
1041 init_count.dismiss();
1042 Ok(())
1043 };
1044 // SAFETY: The initializer above initializes every element of the array. On failure it drops
1045 // any initialized elements and returns `Err`.
1046 unsafe { init_from_closure(init) }
1047}
1048
1049/// Initializes an array by initializing each element via the provided initializer.
1050///
1051/// # Examples
1052///
1053/// ```rust
1054/// use kernel::{sync::{Arc, Mutex}, init::pin_init_array_from_fn, new_mutex};
1055/// let array: Arc<[Mutex<usize>; 1_000]> =
1056/// Arc::pin_init(pin_init_array_from_fn(|i| new_mutex!(i)), GFP_KERNEL).unwrap();
1057/// assert_eq!(array.len(), 1_000);
1058/// ```
1059pub fn pin_init_array_from_fn<I, const N: usize, T, E>(
1060 mut make_init: impl FnMut(usize) -> I,
1061) -> impl PinInit<[T; N], E>
1062where
1063 I: PinInit<T, E>,
1064{
1065 let init = move |slot: *mut [T; N]| {
1066 let slot = slot.cast::<T>();
1067 // Counts the number of initialized elements and when dropped drops that many elements from
1068 // `slot`.
1069 let mut init_count = ScopeGuard::new_with_data(0, |i| {
1070 // We now free every element that has been initialized before.
1071 // SAFETY: The loop initialized exactly the values from 0..i and since we
1072 // return `Err` below, the caller will consider the memory at `slot` as
1073 // uninitialized.
1074 unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1075 });
1076 for i in 0..N {
1077 let init = make_init(i);
1078 // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1079 let ptr = unsafe { slot.add(i) };
1080 // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1081 // requirements.
1082 unsafe { init.__pinned_init(ptr) }?;
1083 *init_count += 1;
1084 }
1085 init_count.dismiss();
1086 Ok(())
1087 };
1088 // SAFETY: The initializer above initializes every element of the array. On failure it drops
1089 // any initialized elements and returns `Err`.
1090 unsafe { pin_init_from_closure(init) }
1091}
1092
1093// SAFETY: Every type can be initialized by-value.
1094unsafe impl<T, E> Init<T, E> for T {
1095 unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
1096 unsafe { slot.write(self) };
1097 Ok(())
1098 }
1099}
1100
1101// SAFETY: Every type can be initialized by-value. `__pinned_init` calls `__init`.
1102unsafe impl<T, E> PinInit<T, E> for T {
1103 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
1104 unsafe { self.__init(slot) }
1105 }
1106}
1107
1108/// Smart pointer that can initialize memory in-place.
1109pub trait InPlaceInit<T>: Sized {
1110 /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1111 /// type.
1112 ///
1113 /// If `T: !Unpin` it will not be able to move afterwards.
1114 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Pin<Self>, E>
1115 where
1116 E: From<AllocError>;
1117
1118 /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1119 /// type.
1120 ///
1121 /// If `T: !Unpin` it will not be able to move afterwards.
1122 fn pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> error::Result<Pin<Self>>
1123 where
1124 Error: From<E>,
1125 {
1126 // SAFETY: We delegate to `init` and only change the error type.
1127 let init = unsafe {
1128 pin_init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1129 };
1130 Self::try_pin_init(init, flags)
1131 }
1132
1133 /// Use the given initializer to in-place initialize a `T`.
1134 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1135 where
1136 E: From<AllocError>;
1137
1138 /// Use the given initializer to in-place initialize a `T`.
1139 fn init<E>(init: impl Init<T, E>, flags: Flags) -> error::Result<Self>
1140 where
1141 Error: From<E>,
1142 {
1143 // SAFETY: We delegate to `init` and only change the error type.
1144 let init = unsafe {
1145 init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1146 };
1147 Self::try_init(init, flags)
1148 }
1149}
1150
1151impl<T> InPlaceInit<T> for Box<T> {
1152 #[inline]
1153 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Pin<Self>, E>
1154 where
1155 E: From<AllocError>,
1156 {
1157 let mut this = <Box<_> as BoxExt<_>>::new_uninit(flags)?;
1158 let slot = this.as_mut_ptr();
1159 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1160 // slot is valid and will not be moved, because we pin it later.
1161 unsafe { init.__pinned_init(slot)? };
1162 // SAFETY: All fields have been initialized.
1163 Ok(unsafe { this.assume_init() }.into())
1164 }
1165
1166 #[inline]
1167 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1168 where
1169 E: From<AllocError>,
1170 {
1171 let mut this = <Box<_> as BoxExt<_>>::new_uninit(flags)?;
1172 let slot = this.as_mut_ptr();
1173 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1174 // slot is valid.
1175 unsafe { init.__init(slot)? };
1176 // SAFETY: All fields have been initialized.
1177 Ok(unsafe { this.assume_init() })
1178 }
1179}
1180
1181impl<T> InPlaceInit<T> for UniqueArc<T> {
1182 #[inline]
1183 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Pin<Self>, E>
1184 where
1185 E: From<AllocError>,
1186 {
1187 let mut this = UniqueArc::new_uninit(flags)?;
1188 let slot = this.as_mut_ptr();
1189 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1190 // slot is valid and will not be moved, because we pin it later.
1191 unsafe { init.__pinned_init(slot)? };
1192 // SAFETY: All fields have been initialized.
1193 Ok(unsafe { this.assume_init() }.into())
1194 }
1195
1196 #[inline]
1197 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1198 where
1199 E: From<AllocError>,
1200 {
1201 let mut this = UniqueArc::new_uninit(flags)?;
1202 let slot = this.as_mut_ptr();
1203 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1204 // slot is valid.
1205 unsafe { init.__init(slot)? };
1206 // SAFETY: All fields have been initialized.
1207 Ok(unsafe { this.assume_init() })
1208 }
1209}
1210
1211/// Trait facilitating pinned destruction.
1212///
1213/// Use [`pinned_drop`] to implement this trait safely:
1214///
1215/// ```rust
1216/// # use kernel::sync::Mutex;
1217/// use kernel::macros::pinned_drop;
1218/// use core::pin::Pin;
1219/// #[pin_data(PinnedDrop)]
1220/// struct Foo {
1221/// #[pin]
1222/// mtx: Mutex<usize>,
1223/// }
1224///
1225/// #[pinned_drop]
1226/// impl PinnedDrop for Foo {
1227/// fn drop(self: Pin<&mut Self>) {
1228/// pr_info!("Foo is being dropped!");
1229/// }
1230/// }
1231/// ```
1232///
1233/// # Safety
1234///
1235/// This trait must be implemented via the [`pinned_drop`] proc-macro attribute on the impl.
1236///
1237/// [`pinned_drop`]: kernel::macros::pinned_drop
1238pub unsafe trait PinnedDrop: __internal::HasPinData {
1239 /// Executes the pinned destructor of this type.
1240 ///
1241 /// While this function is marked safe, it is actually unsafe to call it manually. For this
1242 /// reason it takes an additional parameter. This type can only be constructed by `unsafe` code
1243 /// and thus prevents this function from being called where it should not.
1244 ///
1245 /// This extra parameter will be generated by the `#[pinned_drop]` proc-macro attribute
1246 /// automatically.
1247 fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop);
1248}
1249
1250/// Marker trait for types that can be initialized by writing just zeroes.
1251///
1252/// # Safety
1253///
1254/// The bit pattern consisting of only zeroes is a valid bit pattern for this type. In other words,
1255/// this is not UB:
1256///
1257/// ```rust,ignore
1258/// let val: Self = unsafe { core::mem::zeroed() };
1259/// ```
1260pub unsafe trait Zeroable {}
1261
1262/// Create a new zeroed T.
1263///
1264/// The returned initializer will write `0x00` to every byte of the given `slot`.
1265#[inline]
1266pub fn zeroed<T: Zeroable>() -> impl Init<T> {
1267 // SAFETY: Because `T: Zeroable`, all bytes zero is a valid bit pattern for `T`
1268 // and because we write all zeroes, the memory is initialized.
1269 unsafe {
1270 init_from_closure(|slot: *mut T| {
1271 slot.write_bytes(0, 1);
1272 Ok(())
1273 })
1274 }
1275}
1276
1277macro_rules! impl_zeroable {
1278 ($($({$($generics:tt)*})? $t:ty, )*) => {
1279 $(unsafe impl$($($generics)*)? Zeroable for $t {})*
1280 };
1281}
1282
1283impl_zeroable! {
1284 // SAFETY: All primitives that are allowed to be zero.
1285 bool,
1286 char,
1287 u8, u16, u32, u64, u128, usize,
1288 i8, i16, i32, i64, i128, isize,
1289 f32, f64,
1290
1291 // Note: do not add uninhabited types (such as `!` or `core::convert::Infallible`) to this list;
1292 // creating an instance of an uninhabited type is immediate undefined behavior. For more on
1293 // uninhabited/empty types, consult The Rustonomicon:
1294 // <https://doc.rust-lang.org/stable/nomicon/exotic-sizes.html#empty-types>. The Rust Reference
1295 // also has information on undefined behavior:
1296 // <https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html>.
1297 //
1298 // SAFETY: These are inhabited ZSTs; there is nothing to zero and a valid value exists.
1299 {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, (),
1300
1301 // SAFETY: Type is allowed to take any value, including all zeros.
1302 {<T>} MaybeUninit<T>,
1303 // SAFETY: Type is allowed to take any value, including all zeros.
1304 {<T>} Opaque<T>,
1305
1306 // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.
1307 {<T: ?Sized + Zeroable>} UnsafeCell<T>,
1308
1309 // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1310 Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
1311 Option<NonZeroU128>, Option<NonZeroUsize>,
1312 Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,
1313 Option<NonZeroI128>, Option<NonZeroIsize>,
1314
1315 // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1316 //
1317 // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant.
1318 {<T: ?Sized>} Option<NonNull<T>>,
1319 {<T: ?Sized>} Option<Box<T>>,
1320
1321 // SAFETY: `null` pointer is valid.
1322 //
1323 // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be
1324 // null.
1325 //
1326 // When `Pointee` gets stabilized, we could use
1327 // `T: ?Sized where <T as Pointee>::Metadata: Zeroable`
1328 {<T>} *mut T, {<T>} *const T,
1329
1330 // SAFETY: `null` pointer is valid and the metadata part of these fat pointers is allowed to be
1331 // zero.
1332 {<T>} *mut [T], {<T>} *const [T], *mut str, *const str,
1333
1334 // SAFETY: `T` is `Zeroable`.
1335 {<const N: usize, T: Zeroable>} [T; N], {<T: Zeroable>} Wrapping<T>,
1336}
1337
1338macro_rules! impl_tuple_zeroable {
1339 ($(,)?) => {};
1340 ($first:ident, $($t:ident),* $(,)?) => {
1341 // SAFETY: All elements are zeroable and padding can be zero.
1342 unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {}
1343 impl_tuple_zeroable!($($t),* ,);
1344 }
1345}
1346
1347impl_tuple_zeroable!(A, B, C, D, E, F, G, H, I, J);