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
213 use crate::{
214 alloc::{box_ext::BoxExt, AllocError, Flags},
215 error::{self, Error},
216 sync::Arc,
217 sync::UniqueArc,
218 types::{Opaque, ScopeGuard},
219 };
220 use alloc::boxed::Box;
221 use core::{
222 cell::UnsafeCell,
223 convert::Infallible,
224 marker::PhantomData,
225 mem::MaybeUninit,
226 num::*,
227 pin::Pin,
228 ptr::{self, NonNull},
229 };
230
231 #[doc(hidden)]
232 pub mod __internal;
233 #[doc(hidden)]
234 pub mod macros;
235
236 /// Initialize and pin a type directly on the stack.
237 ///
238 /// # Examples
239 ///
240 /// ```rust
241 /// # #![allow(clippy::disallowed_names)]
242 /// # use kernel::{init, macros::pin_data, pin_init, stack_pin_init, init::*, sync::Mutex, new_mutex};
243 /// # use core::pin::Pin;
244 /// #[pin_data]
245 /// struct Foo {
246 /// #[pin]
247 /// a: Mutex<usize>,
248 /// b: Bar,
249 /// }
250 ///
251 /// #[pin_data]
252 /// struct Bar {
253 /// x: u32,
254 /// }
255 ///
256 /// stack_pin_init!(let foo = pin_init!(Foo {
257 /// a <- new_mutex!(42),
258 /// b: Bar {
259 /// x: 64,
260 /// },
261 /// }));
262 /// let foo: Pin<&mut Foo> = foo;
263 /// pr_info!("a: {}", &*foo.a.lock());
264 /// ```
265 ///
266 /// # Syntax
267 ///
268 /// A normal `let` binding with optional type annotation. The expression is expected to implement
269 /// [`PinInit`]/[`Init`] with the error type [`Infallible`]. If you want to use a different error
270 /// type, then use [`stack_try_pin_init!`].
271 ///
272 /// [`stack_try_pin_init!`]: crate::stack_try_pin_init!
273 #[macro_export]
274 macro_rules! stack_pin_init {
275 (let $var:ident $(: $t:ty)? = $val:expr) => {
276 let val = $val;
277 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
278 let mut $var = match $crate::init::__internal::StackInit::init($var, val) {
279 Ok(res) => res,
280 Err(x) => {
281 let x: ::core::convert::Infallible = x;
282 match x {}
283 }
284 };
285 };
286 }
287
288 /// Initialize and pin a type directly on the stack.
289 ///
290 /// # Examples
291 ///
292 /// ```rust,ignore
293 /// # #![allow(clippy::disallowed_names)]
294 /// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
295 /// # use macros::pin_data;
296 /// # use core::{alloc::AllocError, pin::Pin};
297 /// #[pin_data]
298 /// struct Foo {
299 /// #[pin]
300 /// a: Mutex<usize>,
301 /// b: Box<Bar>,
302 /// }
303 ///
304 /// struct Bar {
305 /// x: u32,
306 /// }
307 ///
308 /// stack_try_pin_init!(let foo: Result<Pin<&mut Foo>, AllocError> = pin_init!(Foo {
309 /// a <- new_mutex!(42),
310 /// b: Box::new(Bar {
311 /// x: 64,
312 /// }, GFP_KERNEL)?,
313 /// }));
314 /// let foo = foo.unwrap();
315 /// pr_info!("a: {}", &*foo.a.lock());
316 /// ```
317 ///
318 /// ```rust,ignore
319 /// # #![allow(clippy::disallowed_names)]
320 /// # use kernel::{init, pin_init, stack_try_pin_init, init::*, sync::Mutex, new_mutex};
321 /// # use macros::pin_data;
322 /// # use core::{alloc::AllocError, pin::Pin};
323 /// #[pin_data]
324 /// struct Foo {
325 /// #[pin]
326 /// a: Mutex<usize>,
327 /// b: Box<Bar>,
328 /// }
329 ///
330 /// struct Bar {
331 /// x: u32,
332 /// }
333 ///
334 /// stack_try_pin_init!(let foo: Pin<&mut Foo> =? pin_init!(Foo {
335 /// a <- new_mutex!(42),
336 /// b: Box::new(Bar {
337 /// x: 64,
338 /// }, GFP_KERNEL)?,
339 /// }));
340 /// pr_info!("a: {}", &*foo.a.lock());
341 /// # Ok::<_, AllocError>(())
342 /// ```
343 ///
344 /// # Syntax
345 ///
346 /// A normal `let` binding with optional type annotation. The expression is expected to implement
347 /// [`PinInit`]/[`Init`]. This macro assigns a result to the given variable, adding a `?` after the
348 /// `=` will propagate this error.
349 #[macro_export]
350 macro_rules! stack_try_pin_init {
351 (let $var:ident $(: $t:ty)? = $val:expr) => {
352 let val = $val;
353 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
354 let mut $var = $crate::init::__internal::StackInit::init($var, val);
355 };
356 (let $var:ident $(: $t:ty)? =? $val:expr) => {
357 let val = $val;
358 let mut $var = ::core::pin::pin!($crate::init::__internal::StackInit$(::<$t>)?::uninit());
359 let mut $var = $crate::init::__internal::StackInit::init($var, val)?;
360 };
361 }
362
363 /// Construct an in-place, pinned initializer for `struct`s.
364 ///
365 /// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
366 /// [`try_pin_init!`].
367 ///
368 /// The syntax is almost identical to that of a normal `struct` initializer:
369 ///
370 /// ```rust
371 /// # #![allow(clippy::disallowed_names)]
372 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
373 /// # use core::pin::Pin;
374 /// #[pin_data]
375 /// struct Foo {
376 /// a: usize,
377 /// b: Bar,
378 /// }
379 ///
380 /// #[pin_data]
381 /// struct Bar {
382 /// x: u32,
383 /// }
384 ///
385 /// # fn demo() -> impl PinInit<Foo> {
386 /// let a = 42;
387 ///
388 /// let initializer = pin_init!(Foo {
389 /// a,
390 /// b: Bar {
391 /// x: 64,
392 /// },
393 /// });
394 /// # initializer }
395 /// # Box::pin_init(demo(), GFP_KERNEL).unwrap();
396 /// ```
397 ///
398 /// Arbitrary Rust expressions can be used to set the value of a variable.
399 ///
400 /// The fields are initialized in the order that they appear in the initializer. So it is possible
401 /// to read already initialized fields using raw pointers.
402 ///
403 /// IMPORTANT: You are not allowed to create references to fields of the struct inside of the
404 /// initializer.
405 ///
406 /// # Init-functions
407 ///
408 /// When working with this API it is often desired to let others construct your types without
409 /// giving access to all fields. This is where you would normally write a plain function `new`
410 /// that would return a new instance of your type. With this API that is also possible.
411 /// However, there are a few extra things to keep in mind.
412 ///
413 /// To create an initializer function, simply declare it like this:
414 ///
415 /// ```rust
416 /// # #![allow(clippy::disallowed_names)]
417 /// # use kernel::{init, pin_init, init::*};
418 /// # use core::pin::Pin;
419 /// # #[pin_data]
420 /// # struct Foo {
421 /// # a: usize,
422 /// # b: Bar,
423 /// # }
424 /// # #[pin_data]
425 /// # struct Bar {
426 /// # x: u32,
427 /// # }
428 /// impl Foo {
429 /// fn new() -> impl PinInit<Self> {
430 /// pin_init!(Self {
431 /// a: 42,
432 /// b: Bar {
433 /// x: 64,
434 /// },
435 /// })
436 /// }
437 /// }
438 /// ```
439 ///
440 /// Users of `Foo` can now create it like this:
441 ///
442 /// ```rust
443 /// # #![allow(clippy::disallowed_names)]
444 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
445 /// # use core::pin::Pin;
446 /// # #[pin_data]
447 /// # struct Foo {
448 /// # a: usize,
449 /// # b: Bar,
450 /// # }
451 /// # #[pin_data]
452 /// # struct Bar {
453 /// # x: u32,
454 /// # }
455 /// # impl Foo {
456 /// # fn new() -> impl PinInit<Self> {
457 /// # pin_init!(Self {
458 /// # a: 42,
459 /// # b: Bar {
460 /// # x: 64,
461 /// # },
462 /// # })
463 /// # }
464 /// # }
465 /// let foo = Box::pin_init(Foo::new(), GFP_KERNEL);
466 /// ```
467 ///
468 /// They can also easily embed it into their own `struct`s:
469 ///
470 /// ```rust
471 /// # #![allow(clippy::disallowed_names)]
472 /// # use kernel::{init, pin_init, macros::pin_data, init::*};
473 /// # use core::pin::Pin;
474 /// # #[pin_data]
475 /// # struct Foo {
476 /// # a: usize,
477 /// # b: Bar,
478 /// # }
479 /// # #[pin_data]
480 /// # struct Bar {
481 /// # x: u32,
482 /// # }
483 /// # impl Foo {
484 /// # fn new() -> impl PinInit<Self> {
485 /// # pin_init!(Self {
486 /// # a: 42,
487 /// # b: Bar {
488 /// # x: 64,
489 /// # },
490 /// # })
491 /// # }
492 /// # }
493 /// #[pin_data]
494 /// struct FooContainer {
495 /// #[pin]
496 /// foo1: Foo,
497 /// #[pin]
498 /// foo2: Foo,
499 /// other: u32,
500 /// }
501 ///
502 /// impl FooContainer {
503 /// fn new(other: u32) -> impl PinInit<Self> {
504 /// pin_init!(Self {
505 /// foo1 <- Foo::new(),
506 /// foo2 <- Foo::new(),
507 /// other,
508 /// })
509 /// }
510 /// }
511 /// ```
512 ///
513 /// Here we see that when using `pin_init!` with `PinInit`, one needs to write `<-` instead of `:`.
514 /// This signifies that the given field is initialized in-place. As with `struct` initializers, just
515 /// writing the field (in this case `other`) without `:` or `<-` means `other: other,`.
516 ///
517 /// # Syntax
518 ///
519 /// As already mentioned in the examples above, inside of `pin_init!` a `struct` initializer with
520 /// the following modifications is expected:
521 /// - Fields that you want to initialize in-place have to use `<-` instead of `:`.
522 /// - In front of the initializer you can write `&this in` to have access to a [`NonNull<Self>`]
523 /// pointer named `this` inside of the initializer.
524 /// - Using struct update syntax one can place `..Zeroable::zeroed()` at the very end of the
525 /// struct, this initializes every field with 0 and then runs all initializers specified in the
526 /// body. This can only be done if [`Zeroable`] is implemented for the struct.
527 ///
528 /// For instance:
529 ///
530 /// ```rust
531 /// # use kernel::{macros::{Zeroable, pin_data}, pin_init};
532 /// # use core::{ptr::addr_of_mut, marker::PhantomPinned};
533 /// #[pin_data]
534 /// #[derive(Zeroable)]
535 /// struct Buf {
536 /// // `ptr` points into `buf`.
537 /// ptr: *mut u8,
538 /// buf: [u8; 64],
539 /// #[pin]
540 /// pin: PhantomPinned,
541 /// }
542 /// pin_init!(&this in Buf {
543 /// buf: [0; 64],
544 /// ptr: unsafe { addr_of_mut!((*this.as_ptr()).buf).cast() },
545 /// pin: PhantomPinned,
546 /// });
547 /// pin_init!(Buf {
548 /// buf: [1; 64],
549 /// ..Zeroable::zeroed()
550 /// });
551 /// ```
552 ///
553 /// [`try_pin_init!`]: kernel::try_pin_init
554 /// [`NonNull<Self>`]: core::ptr::NonNull
555 // For a detailed example of how this macro works, see the module documentation of the hidden
556 // module `__internal` inside of `init/__internal.rs`.
557 #[macro_export]
558 macro_rules! pin_init {
559 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
560 $($fields:tt)*
561 }) => {
562 $crate::__init_internal!(
563 @this($($this)?),
564 @typ($t $(::<$($generics),*>)?),
565 @fields($($fields)*),
566 @error(::core::convert::Infallible),
567 @data(PinData, use_data),
568 @has_data(HasPinData, __pin_data),
569 @construct_closure(pin_init_from_closure),
570 @munch_fields($($fields)*),
571 )
572 };
573 }
574
575 /// Construct an in-place, fallible pinned initializer for `struct`s.
576 ///
577 /// If the initialization can complete without error (or [`Infallible`]), then use [`pin_init!`].
578 ///
579 /// You can use the `?` operator or use `return Err(err)` inside the initializer to stop
580 /// initialization and return the error.
581 ///
582 /// IMPORTANT: if you have `unsafe` code inside of the initializer you have to ensure that when
583 /// initialization fails, the memory can be safely deallocated without any further modifications.
584 ///
585 /// This macro defaults the error to [`Error`].
586 ///
587 /// The syntax is identical to [`pin_init!`] with the following exception: you can append `? $type`
588 /// after the `struct` initializer to specify the error type you want to use.
589 ///
590 /// # Examples
591 ///
592 /// ```rust
593 /// # #![feature(new_uninit)]
594 /// use kernel::{init::{self, PinInit}, error::Error};
595 /// #[pin_data]
596 /// struct BigBuf {
597 /// big: Box<[u8; 1024 * 1024 * 1024]>,
598 /// small: [u8; 1024 * 1024],
599 /// ptr: *mut u8,
600 /// }
601 ///
602 /// impl BigBuf {
603 /// fn new() -> impl PinInit<Self, Error> {
604 /// try_pin_init!(Self {
605 /// big: Box::init(init::zeroed(), GFP_KERNEL)?,
606 /// small: [0; 1024 * 1024],
607 /// ptr: core::ptr::null_mut(),
608 /// }? Error)
609 /// }
610 /// }
611 /// ```
612 // For a detailed example of how this macro works, see the module documentation of the hidden
613 // module `__internal` inside of `init/__internal.rs`.
614 #[macro_export]
615 macro_rules! try_pin_init {
616 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
617 $($fields:tt)*
618 }) => {
619 $crate::__init_internal!(
620 @this($($this)?),
621 @typ($t $(::<$($generics),*>)? ),
622 @fields($($fields)*),
623 @error($crate::error::Error),
624 @data(PinData, use_data),
625 @has_data(HasPinData, __pin_data),
626 @construct_closure(pin_init_from_closure),
627 @munch_fields($($fields)*),
628 )
629 };
630 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
631 $($fields:tt)*
632 }? $err:ty) => {
633 $crate::__init_internal!(
634 @this($($this)?),
635 @typ($t $(::<$($generics),*>)? ),
636 @fields($($fields)*),
637 @error($err),
638 @data(PinData, use_data),
639 @has_data(HasPinData, __pin_data),
640 @construct_closure(pin_init_from_closure),
641 @munch_fields($($fields)*),
642 )
643 };
644 }
645
646 /// Construct an in-place initializer for `struct`s.
647 ///
648 /// This macro defaults the error to [`Infallible`]. If you need [`Error`], then use
649 /// [`try_init!`].
650 ///
651 /// The syntax is identical to [`pin_init!`] and its safety caveats also apply:
652 /// - `unsafe` code must guarantee either full initialization or return an error and allow
653 /// deallocation of the memory.
654 /// - the fields are initialized in the order given in the initializer.
655 /// - no references to fields are allowed to be created inside of the initializer.
656 ///
657 /// This initializer is for initializing data in-place that might later be moved. If you want to
658 /// pin-initialize, use [`pin_init!`].
659 ///
660 /// [`try_init!`]: crate::try_init!
661 // For a detailed example of how this macro works, see the module documentation of the hidden
662 // module `__internal` inside of `init/__internal.rs`.
663 #[macro_export]
664 macro_rules! init {
665 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
666 $($fields:tt)*
667 }) => {
668 $crate::__init_internal!(
669 @this($($this)?),
670 @typ($t $(::<$($generics),*>)?),
671 @fields($($fields)*),
672 @error(::core::convert::Infallible),
673 @data(InitData, /*no use_data*/),
674 @has_data(HasInitData, __init_data),
675 @construct_closure(init_from_closure),
676 @munch_fields($($fields)*),
677 )
678 }
679 }
680
681 /// Construct an in-place fallible initializer for `struct`s.
682 ///
683 /// This macro defaults the error to [`Error`]. If you need [`Infallible`], then use
684 /// [`init!`].
685 ///
686 /// The syntax is identical to [`try_pin_init!`]. If you want to specify a custom error,
687 /// append `? $type` after the `struct` initializer.
688 /// The safety caveats from [`try_pin_init!`] also apply:
689 /// - `unsafe` code must guarantee either full initialization or return an error and allow
690 /// deallocation of the memory.
691 /// - the fields are initialized in the order given in the initializer.
692 /// - no references to fields are allowed to be created inside of the initializer.
693 ///
694 /// # Examples
695 ///
696 /// ```rust
697 /// use kernel::{init::{PinInit, zeroed}, error::Error};
698 /// struct BigBuf {
699 /// big: Box<[u8; 1024 * 1024 * 1024]>,
700 /// small: [u8; 1024 * 1024],
701 /// }
702 ///
703 /// impl BigBuf {
704 /// fn new() -> impl Init<Self, Error> {
705 /// try_init!(Self {
706 /// big: Box::init(zeroed(), GFP_KERNEL)?,
707 /// small: [0; 1024 * 1024],
708 /// }? Error)
709 /// }
710 /// }
711 /// ```
712 // For a detailed example of how this macro works, see the module documentation of the hidden
713 // module `__internal` inside of `init/__internal.rs`.
714 #[macro_export]
715 macro_rules! try_init {
716 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
717 $($fields:tt)*
718 }) => {
719 $crate::__init_internal!(
720 @this($($this)?),
721 @typ($t $(::<$($generics),*>)?),
722 @fields($($fields)*),
723 @error($crate::error::Error),
724 @data(InitData, /*no use_data*/),
725 @has_data(HasInitData, __init_data),
726 @construct_closure(init_from_closure),
727 @munch_fields($($fields)*),
728 )
729 };
730 ($(&$this:ident in)? $t:ident $(::<$($generics:ty),* $(,)?>)? {
731 $($fields:tt)*
732 }? $err:ty) => {
733 $crate::__init_internal!(
734 @this($($this)?),
735 @typ($t $(::<$($generics),*>)?),
736 @fields($($fields)*),
737 @error($err),
738 @data(InitData, /*no use_data*/),
739 @has_data(HasInitData, __init_data),
740 @construct_closure(init_from_closure),
741 @munch_fields($($fields)*),
742 )
743 };
744 }
745
746 /// Asserts that a field on a struct using `#[pin_data]` is marked with `#[pin]` ie. that it is
747 /// structurally pinned.
748 ///
749 /// # Example
750 ///
751 /// This will succeed:
752 /// ```
753 /// use kernel::assert_pinned;
754 /// #[pin_data]
755 /// struct MyStruct {
756 /// #[pin]
757 /// some_field: u64,
758 /// }
759 ///
760 /// assert_pinned!(MyStruct, some_field, u64);
761 /// ```
762 ///
763 /// This will fail:
764 // TODO: replace with `compile_fail` when supported.
765 /// ```ignore
766 /// use kernel::assert_pinned;
767 /// #[pin_data]
768 /// struct MyStruct {
769 /// some_field: u64,
770 /// }
771 ///
772 /// assert_pinned!(MyStruct, some_field, u64);
773 /// ```
774 ///
775 /// Some uses of the macro may trigger the `can't use generic parameters from outer item` error. To
776 /// work around this, you may pass the `inline` parameter to the macro. The `inline` parameter can
777 /// only be used when the macro is invoked from a function body.
778 /// ```
779 /// use kernel::assert_pinned;
780 /// #[pin_data]
781 /// struct Foo<T> {
782 /// #[pin]
783 /// elem: T,
784 /// }
785 ///
786 /// impl<T> Foo<T> {
787 /// fn project(self: Pin<&mut Self>) -> Pin<&mut T> {
788 /// assert_pinned!(Foo<T>, elem, T, inline);
789 ///
790 /// // SAFETY: The field is structurally pinned.
791 /// unsafe { self.map_unchecked_mut(|me| &mut me.elem) }
792 /// }
793 /// }
794 /// ```
795 #[macro_export]
796 macro_rules! assert_pinned {
797 ($ty:ty, $field:ident, $field_ty:ty, inline) => {
798 let _ = move |ptr: *mut $field_ty| {
799 // SAFETY: This code is unreachable.
800 let data = unsafe { <$ty as $crate::init::__internal::HasPinData>::__pin_data() };
801 let init = $crate::init::__internal::AlwaysFail::<$field_ty>::new();
802 // SAFETY: This code is unreachable.
803 unsafe { data.$field(ptr, init) }.ok();
804 };
805 };
806
807 ($ty:ty, $field:ident, $field_ty:ty) => {
808 const _: () = {
809 $crate::assert_pinned!($ty, $field, $field_ty, inline);
810 };
811 };
812 }
813
814 /// A pin-initializer for the type `T`.
815 ///
816 /// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
817 /// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
818 /// [`InPlaceInit::pin_init`] function of a smart pointer like [`Arc<T>`] on this.
819 ///
820 /// Also see the [module description](self).
821 ///
822 /// # Safety
823 ///
824 /// When implementing this trait you will need to take great care. Also there are probably very few
825 /// cases where a manual implementation is necessary. Use [`pin_init_from_closure`] where possible.
826 ///
827 /// The [`PinInit::__pinned_init`] function:
828 /// - returns `Ok(())` if it initialized every field of `slot`,
829 /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
830 /// - `slot` can be deallocated without UB occurring,
831 /// - `slot` does not need to be dropped,
832 /// - `slot` is not partially initialized.
833 /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
834 ///
835 /// [`Arc<T>`]: crate::sync::Arc
836 /// [`Arc::pin_init`]: crate::sync::Arc::pin_init
837 #[must_use = "An initializer must be used in order to create its value."]
838 pub unsafe trait PinInit<T: ?Sized, E = Infallible>: Sized {
839 /// Initializes `slot`.
840 ///
841 /// # Safety
842 ///
843 /// - `slot` is a valid pointer to uninitialized memory.
844 /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
845 /// deallocate.
846 /// - `slot` will not move until it is dropped, i.e. it will be pinned.
847 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E>;
848
849 /// First initializes the value using `self` then calls the function `f` with the initialized
850 /// value.
851 ///
852 /// If `f` returns an error the value is dropped and the initializer will forward the error.
853 ///
854 /// # Examples
855 ///
856 /// ```rust
857 /// # #![allow(clippy::disallowed_names)]
858 /// use kernel::{types::Opaque, init::pin_init_from_closure};
859 /// #[repr(C)]
860 /// struct RawFoo([u8; 16]);
861 /// extern {
862 /// fn init_foo(_: *mut RawFoo);
863 /// }
864 ///
865 /// #[pin_data]
866 /// struct Foo {
867 /// #[pin]
868 /// raw: Opaque<RawFoo>,
869 /// }
870 ///
871 /// impl Foo {
872 /// fn setup(self: Pin<&mut Self>) {
873 /// pr_info!("Setting up foo");
874 /// }
875 /// }
876 ///
877 /// let foo = pin_init!(Foo {
878 /// raw <- unsafe {
879 /// Opaque::ffi_init(|s| {
880 /// init_foo(s);
881 /// })
882 /// },
883 /// }).pin_chain(|foo| {
884 /// foo.setup();
885 /// Ok(())
886 /// });
887 /// ```
888 fn pin_chain<F>(self, f: F) -> ChainPinInit<Self, F, T, E>
889 where
890 F: FnOnce(Pin<&mut T>) -> Result<(), E>,
891 {
892 ChainPinInit(self, f, PhantomData)
893 }
894 }
895
896 /// An initializer returned by [`PinInit::pin_chain`].
897 pub struct ChainPinInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
898
899 // SAFETY: The `__pinned_init` function is implemented such that it
900 // - returns `Ok(())` on successful initialization,
901 // - returns `Err(err)` on error and in this case `slot` will be dropped.
902 // - considers `slot` pinned.
903 unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainPinInit<I, F, T, E>
904 where
905 I: PinInit<T, E>,
906 F: FnOnce(Pin<&mut T>) -> Result<(), E>,
907 {
908 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
909 // SAFETY: All requirements fulfilled since this function is `__pinned_init`.
910 unsafe { self.0.__pinned_init(slot)? };
911 // SAFETY: The above call initialized `slot` and we still have unique access.
912 let val = unsafe { &mut *slot };
913 // SAFETY: `slot` is considered pinned.
914 let val = unsafe { Pin::new_unchecked(val) };
915 // SAFETY: `slot` was initialized above.
916 (self.1)(val).inspect_err(|_| unsafe { core::ptr::drop_in_place(slot) })
917 }
918 }
919
920 /// An initializer for `T`.
921 ///
922 /// To use this initializer, you will need a suitable memory location that can hold a `T`. This can
923 /// be [`Box<T>`], [`Arc<T>`], [`UniqueArc<T>`] or even the stack (see [`stack_pin_init!`]). Use the
924 /// [`InPlaceInit::init`] function of a smart pointer like [`Arc<T>`] on this. Because
925 /// [`PinInit<T, E>`] is a super trait, you can use every function that takes it as well.
926 ///
927 /// Also see the [module description](self).
928 ///
929 /// # Safety
930 ///
931 /// When implementing this trait you will need to take great care. Also there are probably very few
932 /// cases where a manual implementation is necessary. Use [`init_from_closure`] where possible.
933 ///
934 /// The [`Init::__init`] function:
935 /// - returns `Ok(())` if it initialized every field of `slot`,
936 /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
937 /// - `slot` can be deallocated without UB occurring,
938 /// - `slot` does not need to be dropped,
939 /// - `slot` is not partially initialized.
940 /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
941 ///
942 /// The `__pinned_init` function from the supertrait [`PinInit`] needs to execute the exact same
943 /// code as `__init`.
944 ///
945 /// Contrary to its supertype [`PinInit<T, E>`] the caller is allowed to
946 /// move the pointee after initialization.
947 ///
948 /// [`Arc<T>`]: crate::sync::Arc
949 #[must_use = "An initializer must be used in order to create its value."]
950 pub unsafe trait Init<T: ?Sized, E = Infallible>: PinInit<T, E> {
951 /// Initializes `slot`.
952 ///
953 /// # Safety
954 ///
955 /// - `slot` is a valid pointer to uninitialized memory.
956 /// - the caller does not touch `slot` when `Err` is returned, they are only permitted to
957 /// deallocate.
958 unsafe fn __init(self, slot: *mut T) -> Result<(), E>;
959
960 /// First initializes the value using `self` then calls the function `f` with the initialized
961 /// value.
962 ///
963 /// If `f` returns an error the value is dropped and the initializer will forward the error.
964 ///
965 /// # Examples
966 ///
967 /// ```rust
968 /// # #![allow(clippy::disallowed_names)]
969 /// use kernel::{types::Opaque, init::{self, init_from_closure}};
970 /// struct Foo {
971 /// buf: [u8; 1_000_000],
972 /// }
973 ///
974 /// impl Foo {
975 /// fn setup(&mut self) {
976 /// pr_info!("Setting up foo");
977 /// }
978 /// }
979 ///
980 /// let foo = init!(Foo {
981 /// buf <- init::zeroed()
982 /// }).chain(|foo| {
983 /// foo.setup();
984 /// Ok(())
985 /// });
986 /// ```
987 fn chain<F>(self, f: F) -> ChainInit<Self, F, T, E>
988 where
989 F: FnOnce(&mut T) -> Result<(), E>,
990 {
991 ChainInit(self, f, PhantomData)
992 }
993 }
994
995 /// An initializer returned by [`Init::chain`].
996 pub struct ChainInit<I, F, T: ?Sized, E>(I, F, __internal::Invariant<(E, Box<T>)>);
997
998 // SAFETY: The `__init` function is implemented such that it
999 // - returns `Ok(())` on successful initialization,
1000 // - returns `Err(err)` on error and in this case `slot` will be dropped.
1001 unsafe impl<T: ?Sized, E, I, F> Init<T, E> for ChainInit<I, F, T, E>
1002 where
1003 I: Init<T, E>,
1004 F: FnOnce(&mut T) -> Result<(), E>,
1005 {
1006 unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
1007 // SAFETY: All requirements fulfilled since this function is `__init`.
1008 unsafe { self.0.__pinned_init(slot)? };
1009 // SAFETY: The above call initialized `slot` and we still have unique access.
1010 (self.1)(unsafe { &mut *slot }).inspect_err(|_|
1011 // SAFETY: `slot` was initialized above.
1012 unsafe { core::ptr::drop_in_place(slot) })
1013 }
1014 }
1015
1016 // SAFETY: `__pinned_init` behaves exactly the same as `__init`.
1017 unsafe impl<T: ?Sized, E, I, F> PinInit<T, E> for ChainInit<I, F, T, E>
1018 where
1019 I: Init<T, E>,
1020 F: FnOnce(&mut T) -> Result<(), E>,
1021 {
1022 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
1023 // SAFETY: `__init` has less strict requirements compared to `__pinned_init`.
1024 unsafe { self.__init(slot) }
1025 }
1026 }
1027
1028 /// Creates a new [`PinInit<T, E>`] from the given closure.
1029 ///
1030 /// # Safety
1031 ///
1032 /// The closure:
1033 /// - returns `Ok(())` if it initialized every field of `slot`,
1034 /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
1035 /// - `slot` can be deallocated without UB occurring,
1036 /// - `slot` does not need to be dropped,
1037 /// - `slot` is not partially initialized.
1038 /// - may assume that the `slot` does not move if `T: !Unpin`,
1039 /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
1040 #[inline]
1041 pub const unsafe fn pin_init_from_closure<T: ?Sized, E>(
1042 f: impl FnOnce(*mut T) -> Result<(), E>,
1043 ) -> impl PinInit<T, E> {
1044 __internal::InitClosure(f, PhantomData)
1045 }
1046
1047 /// Creates a new [`Init<T, E>`] from the given closure.
1048 ///
1049 /// # Safety
1050 ///
1051 /// The closure:
1052 /// - returns `Ok(())` if it initialized every field of `slot`,
1053 /// - returns `Err(err)` if it encountered an error and then cleaned `slot`, this means:
1054 /// - `slot` can be deallocated without UB occurring,
1055 /// - `slot` does not need to be dropped,
1056 /// - `slot` is not partially initialized.
1057 /// - the `slot` may move after initialization.
1058 /// - while constructing the `T` at `slot` it upholds the pinning invariants of `T`.
1059 #[inline]
1060 pub const unsafe fn init_from_closure<T: ?Sized, E>(
1061 f: impl FnOnce(*mut T) -> Result<(), E>,
1062 ) -> impl Init<T, E> {
1063 __internal::InitClosure(f, PhantomData)
1064 }
1065
1066 /// An initializer that leaves the memory uninitialized.
1067 ///
1068 /// The initializer is a no-op. The `slot` memory is not changed.
1069 #[inline]
1070 pub fn uninit<T, E>() -> impl Init<MaybeUninit<T>, E> {
1071 // SAFETY: The memory is allowed to be uninitialized.
1072 unsafe { init_from_closure(|_| Ok(())) }
1073 }
1074
1075 /// Initializes an array by initializing each element via the provided initializer.
1076 ///
1077 /// # Examples
1078 ///
1079 /// ```rust
1080 /// use kernel::{error::Error, init::init_array_from_fn};
1081 /// let array: Box<[usize; 1_000]> = Box::init::<Error>(init_array_from_fn(|i| i), GFP_KERNEL).unwrap();
1082 /// assert_eq!(array.len(), 1_000);
1083 /// ```
1084 pub fn init_array_from_fn<I, const N: usize, T, E>(
1085 mut make_init: impl FnMut(usize) -> I,
1086 ) -> impl Init<[T; N], E>
1087 where
1088 I: Init<T, E>,
1089 {
1090 let init = move |slot: *mut [T; N]| {
1091 let slot = slot.cast::<T>();
1092 // Counts the number of initialized elements and when dropped drops that many elements from
1093 // `slot`.
1094 let mut init_count = ScopeGuard::new_with_data(0, |i| {
1095 // We now free every element that has been initialized before.
1096 // SAFETY: The loop initialized exactly the values from 0..i and since we
1097 // return `Err` below, the caller will consider the memory at `slot` as
1098 // uninitialized.
1099 unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1100 });
1101 for i in 0..N {
1102 let init = make_init(i);
1103 // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1104 let ptr = unsafe { slot.add(i) };
1105 // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1106 // requirements.
1107 unsafe { init.__init(ptr) }?;
1108 *init_count += 1;
1109 }
1110 init_count.dismiss();
1111 Ok(())
1112 };
1113 // SAFETY: The initializer above initializes every element of the array. On failure it drops
1114 // any initialized elements and returns `Err`.
1115 unsafe { init_from_closure(init) }
1116 }
1117
1118 /// Initializes an array by initializing each element via the provided initializer.
1119 ///
1120 /// # Examples
1121 ///
1122 /// ```rust
1123 /// use kernel::{sync::{Arc, Mutex}, init::pin_init_array_from_fn, new_mutex};
1124 /// let array: Arc<[Mutex<usize>; 1_000]> =
1125 /// Arc::pin_init(pin_init_array_from_fn(|i| new_mutex!(i)), GFP_KERNEL).unwrap();
1126 /// assert_eq!(array.len(), 1_000);
1127 /// ```
1128 pub fn pin_init_array_from_fn<I, const N: usize, T, E>(
1129 mut make_init: impl FnMut(usize) -> I,
1130 ) -> impl PinInit<[T; N], E>
1131 where
1132 I: PinInit<T, E>,
1133 {
1134 let init = move |slot: *mut [T; N]| {
1135 let slot = slot.cast::<T>();
1136 // Counts the number of initialized elements and when dropped drops that many elements from
1137 // `slot`.
1138 let mut init_count = ScopeGuard::new_with_data(0, |i| {
1139 // We now free every element that has been initialized before.
1140 // SAFETY: The loop initialized exactly the values from 0..i and since we
1141 // return `Err` below, the caller will consider the memory at `slot` as
1142 // uninitialized.
1143 unsafe { ptr::drop_in_place(ptr::slice_from_raw_parts_mut(slot, i)) };
1144 });
1145 for i in 0..N {
1146 let init = make_init(i);
1147 // SAFETY: Since 0 <= `i` < N, it is still in bounds of `[T; N]`.
1148 let ptr = unsafe { slot.add(i) };
1149 // SAFETY: The pointer is derived from `slot` and thus satisfies the `__init`
1150 // requirements.
1151 unsafe { init.__pinned_init(ptr) }?;
1152 *init_count += 1;
1153 }
1154 init_count.dismiss();
1155 Ok(())
1156 };
1157 // SAFETY: The initializer above initializes every element of the array. On failure it drops
1158 // any initialized elements and returns `Err`.
1159 unsafe { pin_init_from_closure(init) }
1160 }
1161
1162 // SAFETY: Every type can be initialized by-value.
1163 unsafe impl<T, E> Init<T, E> for T {
1164 unsafe fn __init(self, slot: *mut T) -> Result<(), E> {
1165 unsafe { slot.write(self) };
1166 Ok(())
1167 }
1168 }
1169
1170 // SAFETY: Every type can be initialized by-value. `__pinned_init` calls `__init`.
1171 unsafe impl<T, E> PinInit<T, E> for T {
1172 unsafe fn __pinned_init(self, slot: *mut T) -> Result<(), E> {
1173 unsafe { self.__init(slot) }
1174 }
1175 }
1176
1177 /// Smart pointer that can initialize memory in-place.
1178 pub trait InPlaceInit<T>: Sized {
1179 /// Pinned version of `Self`.
1180 ///
1181 /// If a type already implicitly pins its pointee, `Pin<Self>` is unnecessary. In this case use
1182 /// `Self`, otherwise just use `Pin<Self>`.
1183 type PinnedSelf;
1184
1185 /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1186 /// type.
1187 ///
1188 /// If `T: !Unpin` it will not be able to move afterwards.
1189 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
1190 where
1191 E: From<AllocError>;
1192
1193 /// Use the given pin-initializer to pin-initialize a `T` inside of a new smart pointer of this
1194 /// type.
1195 ///
1196 /// If `T: !Unpin` it will not be able to move afterwards.
1197 fn pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> error::Result<Self::PinnedSelf>
1198 where
1199 Error: From<E>,
1200 {
1201 // SAFETY: We delegate to `init` and only change the error type.
1202 let init = unsafe {
1203 pin_init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1204 };
1205 Self::try_pin_init(init, flags)
1206 }
1207
1208 /// Use the given initializer to in-place initialize a `T`.
1209 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1210 where
1211 E: From<AllocError>;
1212
1213 /// Use the given initializer to in-place initialize a `T`.
1214 fn init<E>(init: impl Init<T, E>, flags: Flags) -> error::Result<Self>
1215 where
1216 Error: From<E>,
1217 {
1218 // SAFETY: We delegate to `init` and only change the error type.
1219 let init = unsafe {
1220 init_from_closure(|slot| init.__pinned_init(slot).map_err(|e| Error::from(e)))
1221 };
1222 Self::try_init(init, flags)
1223 }
1224 }
1225
1226 impl<T> InPlaceInit<T> for Arc<T> {
1227 type PinnedSelf = Self;
1228
1229 #[inline]
1230 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
1231 where
1232 E: From<AllocError>,
1233 {
1234 UniqueArc::try_pin_init(init, flags).map(|u| u.into())
1235 }
1236
1237 #[inline]
1238 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1239 where
1240 E: From<AllocError>,
1241 {
1242 UniqueArc::try_init(init, flags).map(|u| u.into())
1243 }
1244 }
1245
1246 impl<T> InPlaceInit<T> for Box<T> {
1247 type PinnedSelf = Pin<Self>;
1248
1249 #[inline]
1250 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
1251 where
1252 E: From<AllocError>,
1253 {
1254 <Box<_> as BoxExt<_>>::new_uninit(flags)?.write_pin_init(init)
1255 }
1256
1257 #[inline]
1258 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1259 where
1260 E: From<AllocError>,
1261 {
1262 <Box<_> as BoxExt<_>>::new_uninit(flags)?.write_init(init)
1263 }
1264 }
1265
1266 impl<T> InPlaceInit<T> for UniqueArc<T> {
1267 type PinnedSelf = Pin<Self>;
1268
1269 #[inline]
1270 fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
1271 where
1272 E: From<AllocError>,
1273 {
1274 UniqueArc::new_uninit(flags)?.write_pin_init(init)
1275 }
1276
1277 #[inline]
1278 fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
1279 where
1280 E: From<AllocError>,
1281 {
1282 UniqueArc::new_uninit(flags)?.write_init(init)
1283 }
1284 }
1285
1286 /// Smart pointer containing uninitialized memory and that can write a value.
1287 pub trait InPlaceWrite<T> {
1288 /// The type `Self` turns into when the contents are initialized.
1289 type Initialized;
1290
1291 /// Use the given initializer to write a value into `self`.
1292 ///
1293 /// Does not drop the current value and considers it as uninitialized memory.
1294 fn write_init<E>(self, init: impl Init<T, E>) -> Result<Self::Initialized, E>;
1295
1296 /// Use the given pin-initializer to write a value into `self`.
1297 ///
1298 /// Does not drop the current value and considers it as uninitialized memory.
1299 fn write_pin_init<E>(self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E>;
1300 }
1301
1302 impl<T> InPlaceWrite<T> for Box<MaybeUninit<T>> {
1303 type Initialized = Box<T>;
1304
1305 fn write_init<E>(mut self, init: impl Init<T, E>) -> Result<Self::Initialized, E> {
1306 let slot = self.as_mut_ptr();
1307 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1308 // slot is valid.
1309 unsafe { init.__init(slot)? };
1310 // SAFETY: All fields have been initialized.
1311 Ok(unsafe { self.assume_init() })
1312 }
1313
1314 fn write_pin_init<E>(mut self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E> {
1315 let slot = self.as_mut_ptr();
1316 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1317 // slot is valid and will not be moved, because we pin it later.
1318 unsafe { init.__pinned_init(slot)? };
1319 // SAFETY: All fields have been initialized.
1320 Ok(unsafe { self.assume_init() }.into())
1321 }
1322 }
1323
1324 impl<T> InPlaceWrite<T> for UniqueArc<MaybeUninit<T>> {
1325 type Initialized = UniqueArc<T>;
1326
1327 fn write_init<E>(mut self, init: impl Init<T, E>) -> Result<Self::Initialized, E> {
1328 let slot = self.as_mut_ptr();
1329 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1330 // slot is valid.
1331 unsafe { init.__init(slot)? };
1332 // SAFETY: All fields have been initialized.
1333 Ok(unsafe { self.assume_init() })
1334 }
1335
1336 fn write_pin_init<E>(mut self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E> {
1337 let slot = self.as_mut_ptr();
1338 // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
1339 // slot is valid and will not be moved, because we pin it later.
1340 unsafe { init.__pinned_init(slot)? };
1341 // SAFETY: All fields have been initialized.
1342 Ok(unsafe { self.assume_init() }.into())
1343 }
1344 }
1345
1346 /// Trait facilitating pinned destruction.
1347 ///
1348 /// Use [`pinned_drop`] to implement this trait safely:
1349 ///
1350 /// ```rust
1351 /// # use kernel::sync::Mutex;
1352 /// use kernel::macros::pinned_drop;
1353 /// use core::pin::Pin;
1354 /// #[pin_data(PinnedDrop)]
1355 /// struct Foo {
1356 /// #[pin]
1357 /// mtx: Mutex<usize>,
1358 /// }
1359 ///
1360 /// #[pinned_drop]
1361 /// impl PinnedDrop for Foo {
1362 /// fn drop(self: Pin<&mut Self>) {
1363 /// pr_info!("Foo is being dropped!");
1364 /// }
1365 /// }
1366 /// ```
1367 ///
1368 /// # Safety
1369 ///
1370 /// This trait must be implemented via the [`pinned_drop`] proc-macro attribute on the impl.
1371 ///
1372 /// [`pinned_drop`]: kernel::macros::pinned_drop
1373 pub unsafe trait PinnedDrop: __internal::HasPinData {
1374 /// Executes the pinned destructor of this type.
1375 ///
1376 /// While this function is marked safe, it is actually unsafe to call it manually. For this
1377 /// reason it takes an additional parameter. This type can only be constructed by `unsafe` code
1378 /// and thus prevents this function from being called where it should not.
1379 ///
1380 /// This extra parameter will be generated by the `#[pinned_drop]` proc-macro attribute
1381 /// automatically.
1382 fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop);
1383 }
1384
1385 /// Marker trait for types that can be initialized by writing just zeroes.
1386 ///
1387 /// # Safety
1388 ///
1389 /// The bit pattern consisting of only zeroes is a valid bit pattern for this type. In other words,
1390 /// this is not UB:
1391 ///
1392 /// ```rust,ignore
1393 /// let val: Self = unsafe { core::mem::zeroed() };
1394 /// ```
1395 pub unsafe trait Zeroable {}
1396
1397 /// Create a new zeroed T.
1398 ///
1399 /// The returned initializer will write `0x00` to every byte of the given `slot`.
1400 #[inline]
1401 pub fn zeroed<T: Zeroable>() -> impl Init<T> {
1402 // SAFETY: Because `T: Zeroable`, all bytes zero is a valid bit pattern for `T`
1403 // and because we write all zeroes, the memory is initialized.
1404 unsafe {
1405 init_from_closure(|slot: *mut T| {
1406 slot.write_bytes(0, 1);
1407 Ok(())
1408 })
1409 }
1410 }
1411
1412 macro_rules! impl_zeroable {
1413 ($($({$($generics:tt)*})? $t:ty, )*) => {
1414 $(unsafe impl$($($generics)*)? Zeroable for $t {})*
1415 };
1416 }
1417
1418 impl_zeroable! {
1419 // SAFETY: All primitives that are allowed to be zero.
1420 bool,
1421 char,
1422 u8, u16, u32, u64, u128, usize,
1423 i8, i16, i32, i64, i128, isize,
1424 f32, f64,
1425
1426 // Note: do not add uninhabited types (such as `!` or `core::convert::Infallible`) to this list;
1427 // creating an instance of an uninhabited type is immediate undefined behavior. For more on
1428 // uninhabited/empty types, consult The Rustonomicon:
1429 // <https://doc.rust-lang.org/stable/nomicon/exotic-sizes.html#empty-types>. The Rust Reference
1430 // also has information on undefined behavior:
1431 // <https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html>.
1432 //
1433 // SAFETY: These are inhabited ZSTs; there is nothing to zero and a valid value exists.
1434 {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, (),
1435
1436 // SAFETY: Type is allowed to take any value, including all zeros.
1437 {<T>} MaybeUninit<T>,
1438 // SAFETY: Type is allowed to take any value, including all zeros.
1439 {<T>} Opaque<T>,
1440
1441 // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.
1442 {<T: ?Sized + Zeroable>} UnsafeCell<T>,
1443
1444 // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1445 Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
1446 Option<NonZeroU128>, Option<NonZeroUsize>,
1447 Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,
1448 Option<NonZeroI128>, Option<NonZeroIsize>,
1449
1450 // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).
1451 //
1452 // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant.
1453 {<T: ?Sized>} Option<NonNull<T>>,
1454 {<T: ?Sized>} Option<Box<T>>,
1455
1456 // SAFETY: `null` pointer is valid.
1457 //
1458 // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be
1459 // null.
1460 //
1461 // When `Pointee` gets stabilized, we could use
1462 // `T: ?Sized where <T as Pointee>::Metadata: Zeroable`
1463 {<T>} *mut T, {<T>} *const T,
1464
1465 // SAFETY: `null` pointer is valid and the metadata part of these fat pointers is allowed to be
1466 // zero.
1467 {<T>} *mut [T], {<T>} *const [T], *mut str, *const str,
1468
1469 // SAFETY: `T` is `Zeroable`.
1470 {<const N: usize, T: Zeroable>} [T; N], {<T: Zeroable>} Wrapping<T>,
1471 }
1472
1473 macro_rules! impl_tuple_zeroable {
1474 ($(,)?) => {};
1475 ($first:ident, $($t:ident),* $(,)?) => {
1476 // SAFETY: All elements are zeroable and padding can be zero.
1477 unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {}
1478 impl_tuple_zeroable!($($t),* ,);
1479 }
1480 }
1481
1482 impl_tuple_zeroable!(A, B, C, D, E, F, G, H, I, J);
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