diff options
| -rw-r--r-- | MAINTAINERS | 1 | ||||
| -rw-r--r-- | Makefile | 2 | ||||
| -rw-r--r-- | rust/Makefile | 15 | ||||
| -rw-r--r-- | rust/alloc/borrow.rs | 498 | ||||
| -rw-r--r-- | rust/alloc/lib.rs | 3 | ||||
| -rw-r--r-- | rust/alloc/vec/mod.rs | 3 | ||||
| -rw-r--r-- | rust/bindings/bindings_helper.h | 1 | ||||
| -rw-r--r-- | rust/bindings/lib.rs | 1 | ||||
| -rw-r--r-- | rust/compiler_builtins.rs | 5 | ||||
| -rw-r--r-- | rust/helpers.c | 19 | ||||
| -rw-r--r-- | rust/kernel/lib.rs | 6 | ||||
| -rw-r--r-- | rust/kernel/prelude.rs | 8 | ||||
| -rw-r--r-- | rust/kernel/sync.rs | 10 | ||||
| -rw-r--r-- | rust/kernel/sync/arc.rs | 524 | ||||
| -rw-r--r-- | rust/kernel/types.rs | 215 |
15 files changed, 808 insertions, 503 deletions
diff --git a/MAINTAINERS b/MAINTAINERS index 135d93368d36..745101b1399f 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -18234,6 +18234,7 @@ L: rust-for-linux@vger.kernel.org S: Supported W: https://github.com/Rust-for-Linux/linux B: https://github.com/Rust-for-Linux/linux/issues +C: zulip://rust-for-linux.zulipchat.com T: git https://github.com/Rust-for-Linux/linux.git rust-next F: Documentation/rust/ F: rust/ @@ -1602,7 +1602,7 @@ endif # CONFIG_MODULES CLEAN_FILES += include/ksym vmlinux.symvers modules-only.symvers \ modules.builtin modules.builtin.modinfo modules.nsdeps \ compile_commands.json .thinlto-cache rust/test rust/doc \ - .vmlinux.objs .vmlinux.export.c + rust-project.json .vmlinux.objs .vmlinux.export.c # Directories & files removed with 'make mrproper' MRPROPER_FILES += include/config include/generated \ diff --git a/rust/Makefile b/rust/Makefile index ff70c4c916f8..8a521f2b6422 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -50,6 +50,7 @@ core-cfgs = \ --cfg no_fp_fmt_parse alloc-cfgs = \ + --cfg no_borrow \ --cfg no_fmt \ --cfg no_global_oom_handling \ --cfg no_macros \ @@ -359,8 +360,22 @@ rust-analyzer: $(Q)$(srctree)/scripts/generate_rust_analyzer.py $(srctree) $(objtree) \ $(RUST_LIB_SRC) > $(objtree)/rust-project.json +redirect-intrinsics = \ + __eqsf2 __gesf2 __lesf2 __nesf2 __unordsf2 \ + __unorddf2 \ + __muloti4 __multi3 \ + __udivmodti4 __udivti3 __umodti3 + +ifneq ($(or $(CONFIG_ARM64),$(and $(CONFIG_RISCV),$(CONFIG_64BIT))),) + # These intrinsics are defined for ARM64 and RISCV64 + redirect-intrinsics += \ + __ashrti3 \ + __ashlti3 __lshrti3 +endif + $(obj)/core.o: private skip_clippy = 1 $(obj)/core.o: private skip_flags = -Dunreachable_pub +$(obj)/core.o: private rustc_objcopy = $(foreach sym,$(redirect-intrinsics),--redefine-sym $(sym)=__rust$(sym)) $(obj)/core.o: private rustc_target_flags = $(core-cfgs) $(obj)/core.o: $(RUST_LIB_SRC)/core/src/lib.rs $(obj)/target.json FORCE $(call if_changed_dep,rustc_library) diff --git a/rust/alloc/borrow.rs b/rust/alloc/borrow.rs deleted file mode 100644 index dde4957200d4..000000000000 --- a/rust/alloc/borrow.rs +++ /dev/null @@ -1,498 +0,0 @@ -// SPDX-License-Identifier: Apache-2.0 OR MIT - -//! A module for working with borrowed data. - -#![stable(feature = "rust1", since = "1.0.0")] - -use core::cmp::Ordering; -use core::hash::{Hash, Hasher}; -use core::ops::Deref; -#[cfg(not(no_global_oom_handling))] -use core::ops::{Add, AddAssign}; - -#[stable(feature = "rust1", since = "1.0.0")] -pub use core::borrow::{Borrow, BorrowMut}; - -use core::fmt; -#[cfg(not(no_global_oom_handling))] -use crate::string::String; - -use Cow::*; - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B> -where - B: ToOwned, - <B as ToOwned>::Owned: 'a, -{ - fn borrow(&self) -> &B { - &**self - } -} - -/// A generalization of `Clone` to borrowed data. -/// -/// Some types make it possible to go from borrowed to owned, usually by -/// implementing the `Clone` trait. But `Clone` works only for going from `&T` -/// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data -/// from any borrow of a given type. -#[cfg_attr(not(test), rustc_diagnostic_item = "ToOwned")] -#[stable(feature = "rust1", since = "1.0.0")] -pub trait ToOwned { - /// The resulting type after obtaining ownership. - #[stable(feature = "rust1", since = "1.0.0")] - type Owned: Borrow<Self>; - - /// Creates owned data from borrowed data, usually by cloning. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// let s: &str = "a"; - /// let ss: String = s.to_owned(); - /// - /// let v: &[i32] = &[1, 2]; - /// let vv: Vec<i32> = v.to_owned(); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - #[must_use = "cloning is often expensive and is not expected to have side effects"] - fn to_owned(&self) -> Self::Owned; - - /// Uses borrowed data to replace owned data, usually by cloning. - /// - /// This is borrow-generalized version of `Clone::clone_from`. - /// - /// # Examples - /// - /// Basic usage: - /// - /// ``` - /// # #![feature(toowned_clone_into)] - /// let mut s: String = String::new(); - /// "hello".clone_into(&mut s); - /// - /// let mut v: Vec<i32> = Vec::new(); - /// [1, 2][..].clone_into(&mut v); - /// ``` - #[unstable(feature = "toowned_clone_into", reason = "recently added", issue = "41263")] - fn clone_into(&self, target: &mut Self::Owned) { - *target = self.to_owned(); - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T> ToOwned for T -where - T: Clone, -{ - type Owned = T; - fn to_owned(&self) -> T { - self.clone() - } - - fn clone_into(&self, target: &mut T) { - target.clone_from(self); - } -} - -/// A clone-on-write smart pointer. -/// -/// The type `Cow` is a smart pointer providing clone-on-write functionality: it -/// can enclose and provide immutable access to borrowed data, and clone the -/// data lazily when mutation or ownership is required. The type is designed to -/// work with general borrowed data via the `Borrow` trait. -/// -/// `Cow` implements `Deref`, which means that you can call -/// non-mutating methods directly on the data it encloses. If mutation -/// is desired, `to_mut` will obtain a mutable reference to an owned -/// value, cloning if necessary. -/// -/// If you need reference-counting pointers, note that -/// [`Rc::make_mut`][crate::rc::Rc::make_mut] and -/// [`Arc::make_mut`][crate::sync::Arc::make_mut] can provide clone-on-write -/// functionality as well. -/// -/// # Examples -/// -/// ``` -/// use std::borrow::Cow; -/// -/// fn abs_all(input: &mut Cow<[i32]>) { -/// for i in 0..input.len() { -/// let v = input[i]; -/// if v < 0 { -/// // Clones into a vector if not already owned. -/// input.to_mut()[i] = -v; -/// } -/// } -/// } -/// -/// // No clone occurs because `input` doesn't need to be mutated. -/// let slice = [0, 1, 2]; -/// let mut input = Cow::from(&slice[..]); -/// abs_all(&mut input); -/// -/// // Clone occurs because `input` needs to be mutated. -/// let slice = [-1, 0, 1]; -/// let mut input = Cow::from(&slice[..]); -/// abs_all(&mut input); -/// -/// // No clone occurs because `input` is already owned. -/// let mut input = Cow::from(vec![-1, 0, 1]); -/// abs_all(&mut input); -/// ``` -/// -/// Another example showing how to keep `Cow` in a struct: -/// -/// ``` -/// use std::borrow::Cow; -/// -/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> { -/// values: Cow<'a, [X]>, -/// } -/// -/// impl<'a, X: Clone + 'a> Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> { -/// fn new(v: Cow<'a, [X]>) -> Self { -/// Items { values: v } -/// } -/// } -/// -/// // Creates a container from borrowed values of a slice -/// let readonly = [1, 2]; -/// let borrowed = Items::new((&readonly[..]).into()); -/// match borrowed { -/// Items { values: Cow::Borrowed(b) } => println!("borrowed {b:?}"), -/// _ => panic!("expect borrowed value"), -/// } -/// -/// let mut clone_on_write = borrowed; -/// // Mutates the data from slice into owned vec and pushes a new value on top -/// clone_on_write.values.to_mut().push(3); -/// println!("clone_on_write = {:?}", clone_on_write.values); -/// -/// // The data was mutated. Let's check it out. -/// match clone_on_write { -/// Items { values: Cow::Owned(_) } => println!("clone_on_write contains owned data"), -/// _ => panic!("expect owned data"), -/// } -/// ``` -#[stable(feature = "rust1", since = "1.0.0")] -#[cfg_attr(not(test), rustc_diagnostic_item = "Cow")] -pub enum Cow<'a, B: ?Sized + 'a> -where - B: ToOwned, -{ - /// Borrowed data. - #[stable(feature = "rust1", since = "1.0.0")] - Borrowed(#[stable(feature = "rust1", since = "1.0.0")] &'a B), - - /// Owned data. - #[stable(feature = "rust1", since = "1.0.0")] - Owned(#[stable(feature = "rust1", since = "1.0.0")] <B as ToOwned>::Owned), -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> { - fn clone(&self) -> Self { - match *self { - Borrowed(b) => Borrowed(b), - Owned(ref o) => { - let b: &B = o.borrow(); - Owned(b.to_owned()) - } - } - } - - fn clone_from(&mut self, source: &Self) { - match (self, source) { - (&mut Owned(ref mut dest), &Owned(ref o)) => o.borrow().clone_into(dest), - (t, s) => *t = s.clone(), - } - } -} - -impl<B: ?Sized + ToOwned> Cow<'_, B> { - /// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work. - /// - /// # Examples - /// - /// ``` - /// #![feature(cow_is_borrowed)] - /// use std::borrow::Cow; - /// - /// let cow = Cow::Borrowed("moo"); - /// assert!(cow.is_borrowed()); - /// - /// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string()); - /// assert!(!bull.is_borrowed()); - /// ``` - #[unstable(feature = "cow_is_borrowed", issue = "65143")] - #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")] - pub const fn is_borrowed(&self) -> bool { - match *self { - Borrowed(_) => true, - Owned(_) => false, - } - } - - /// Returns true if the data is owned, i.e. if `to_mut` would be a no-op. - /// - /// # Examples - /// - /// ``` - /// #![feature(cow_is_borrowed)] - /// use std::borrow::Cow; - /// - /// let cow: Cow<'_, str> = Cow::Owned("moo".to_string()); - /// assert!(cow.is_owned()); - /// - /// let bull = Cow::Borrowed("...moo?"); - /// assert!(!bull.is_owned()); - /// ``` - #[unstable(feature = "cow_is_borrowed", issue = "65143")] - #[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")] - pub const fn is_owned(&self) -> bool { - !self.is_borrowed() - } - - /// Acquires a mutable reference to the owned form of the data. - /// - /// Clones the data if it is not already owned. - /// - /// # Examples - /// - /// ``` - /// use std::borrow::Cow; - /// - /// let mut cow = Cow::Borrowed("foo"); - /// cow.to_mut().make_ascii_uppercase(); - /// - /// assert_eq!( - /// cow, - /// Cow::Owned(String::from("FOO")) as Cow<str> - /// ); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned { - match *self { - Borrowed(borrowed) => { - *self = Owned(borrowed.to_owned()); - match *self { - Borrowed(..) => unreachable!(), - Owned(ref mut owned) => owned, - } - } - Owned(ref mut owned) => owned, - } - } - - /// Extracts the owned data. - /// - /// Clones the data if it is not already owned. - /// - /// # Examples - /// - /// Calling `into_owned` on a `Cow::Borrowed` returns a clone of the borrowed data: - /// - /// ``` - /// use std::borrow::Cow; - /// - /// let s = "Hello world!"; - /// let cow = Cow::Borrowed(s); - /// - /// assert_eq!( - /// cow.into_owned(), - /// String::from(s) - /// ); - /// ``` - /// - /// Calling `into_owned` on a `Cow::Owned` returns the owned data. The data is moved out of the - /// `Cow` without being cloned. - /// - /// ``` - /// use std::borrow::Cow; - /// - /// let s = "Hello world!"; - /// let cow: Cow<str> = Cow::Owned(String::from(s)); - /// - /// assert_eq!( - /// cow.into_owned(), - /// String::from(s) - /// ); - /// ``` - #[stable(feature = "rust1", since = "1.0.0")] - pub fn into_owned(self) -> <B as ToOwned>::Owned { - match self { - Borrowed(borrowed) => borrowed.to_owned(), - Owned(owned) => owned, - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -#[rustc_const_unstable(feature = "const_deref", issue = "88955")] -impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B> -where - B::Owned: ~const Borrow<B>, -{ - type Target = B; - - fn deref(&self) -> &B { - match *self { - Borrowed(borrowed) => borrowed, - Owned(ref owned) => owned.borrow(), - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized> Ord for Cow<'_, B> -where - B: Ord + ToOwned, -{ - #[inline] - fn cmp(&self, other: &Self) -> Ordering { - Ord::cmp(&**self, &**other) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, 'b, B: ?Sized, C: ?Sized> PartialEq<Cow<'b, C>> for Cow<'a, B> -where - B: PartialEq<C> + ToOwned, - C: ToOwned, -{ - #[inline] - fn eq(&self, other: &Cow<'b, C>) -> bool { - PartialEq::eq(&**self, &**other) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<'a, B: ?Sized> PartialOrd for Cow<'a, B> -where - B: PartialOrd + ToOwned, -{ - #[inline] - fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering> { - PartialOrd::partial_cmp(&**self, &**other) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized> fmt::Debug for Cow<'_, B> -where - B: fmt::Debug + ToOwned<Owned: fmt::Debug>, -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - match *self { - Borrowed(ref b) => fmt::Debug::fmt(b, f), - Owned(ref o) => fmt::Debug::fmt(o, f), - } - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized> fmt::Display for Cow<'_, B> -where - B: fmt::Display + ToOwned<Owned: fmt::Display>, -{ - fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - match *self { - Borrowed(ref b) => fmt::Display::fmt(b, f), - Owned(ref o) => fmt::Display::fmt(o, f), - } - } -} - -#[stable(feature = "default", since = "1.11.0")] -impl<B: ?Sized> Default for Cow<'_, B> -where - B: ToOwned<Owned: Default>, -{ - /// Creates an owned Cow<'a, B> with the default value for the contained owned value. - fn default() -> Self { - Owned(<B as ToOwned>::Owned::default()) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<B: ?Sized> Hash for Cow<'_, B> -where - B: Hash + ToOwned, -{ - #[inline] - fn hash<H: Hasher>(&self, state: &mut H) { - Hash::hash(&**self, state) - } -} - -#[stable(feature = "rust1", since = "1.0.0")] -impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> { - fn as_ref(&self) -> &T { - self - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_add", since = "1.14.0")] -impl<'a> Add<&'a str> for Cow<'a, str> { - type Output = Cow<'a, str>; - - #[inline] - fn add(mut self, rhs: &'a str) -> Self::Output { - self += rhs; - self - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_add", since = "1.14.0")] -impl<'a> Add<Cow<'a, str>> for Cow<'a, str> { - type Output = Cow<'a, str>; - - #[inline] - fn add(mut self, rhs: Cow<'a, str>) -> Self::Output { - self += rhs; - self - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_add", since = "1.14.0")] -impl<'a> AddAssign<&'a str> for Cow<'a, str> { - fn add_assign(&mut self, rhs: &'a str) { - if self.is_empty() { - *self = Cow::Borrowed(rhs) - } else if !rhs.is_empty() { - if let Cow::Borrowed(lhs) = *self { - let mut s = String::with_capacity(lhs.len() + rhs.len()); - s.push_str(lhs); - *self = Cow::Owned(s); - } - self.to_mut().push_str(rhs); - } - } -} - -#[cfg(not(no_global_oom_handling))] -#[stable(feature = "cow_add", since = "1.14.0")] -impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str> { - fn add_assign(&mut self, rhs: Cow<'a, str>) { - if self.is_empty() { - *self = rhs - } else if !rhs.is_empty() { - if let Cow::Borrowed(lhs) = *self { - let mut s = String::with_capacity(lhs.len() + rhs.len()); - s.push_str(lhs); - *self = Cow::Owned(s); - } - self.to_mut().push_str(&rhs); - } - } -} diff --git a/rust/alloc/lib.rs b/rust/alloc/lib.rs index 233bcd5e4654..3aebf83c9967 100644 --- a/rust/alloc/lib.rs +++ b/rust/alloc/lib.rs @@ -100,7 +100,7 @@ #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))] #![feature(const_box)] #![cfg_attr(not(no_global_oom_handling), feature(const_btree_new))] -#![feature(const_cow_is_borrowed)] +#![cfg_attr(not(no_borrow), feature(const_cow_is_borrowed))] #![feature(const_convert)] #![feature(const_size_of_val)] #![feature(const_align_of_val)] @@ -215,6 +215,7 @@ pub mod boxed; mod boxed { pub use std::boxed::Box; } +#[cfg(not(no_borrow))] pub mod borrow; pub mod collections; #[cfg(not(no_global_oom_handling))] diff --git a/rust/alloc/vec/mod.rs b/rust/alloc/vec/mod.rs index 8ac6c1e3b2a8..f77c7368d534 100644 --- a/rust/alloc/vec/mod.rs +++ b/rust/alloc/vec/mod.rs @@ -72,6 +72,7 @@ use core::ptr::{self, NonNull}; use core::slice::{self, SliceIndex}; use crate::alloc::{Allocator, Global}; +#[cfg(not(no_borrow))] use crate::borrow::{Cow, ToOwned}; use crate::boxed::Box; use crate::collections::TryReserveError; @@ -94,6 +95,7 @@ pub use self::drain::Drain; mod drain; +#[cfg(not(no_borrow))] #[cfg(not(no_global_oom_handling))] mod cow; @@ -3103,6 +3105,7 @@ impl<T, const N: usize> From<[T; N]> for Vec<T> { } } +#[cfg(not(no_borrow))] #[stable(feature = "vec_from_cow_slice", since = "1.14.0")] impl<'a, T> From<Cow<'a, [T]>> for Vec<T> where diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index c48bc284214a..75d85bd6c592 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -7,6 +7,7 @@ */ #include <linux/slab.h> +#include <linux/refcount.h> /* `bindgen` gets confused at certain things. */ const gfp_t BINDINGS_GFP_KERNEL = GFP_KERNEL; diff --git a/rust/bindings/lib.rs b/rust/bindings/lib.rs index 6c50ee62c56b..7b246454e009 100644 --- a/rust/bindings/lib.rs +++ b/rust/bindings/lib.rs @@ -41,6 +41,7 @@ mod bindings_raw { #[allow(dead_code)] mod bindings_helper { // Import the generated bindings for types. + use super::bindings_raw::*; include!(concat!( env!("OBJTREE"), "/rust/bindings/bindings_helpers_generated.rs" diff --git a/rust/compiler_builtins.rs b/rust/compiler_builtins.rs index f8f39a3e6855..43378357ece9 100644 --- a/rust/compiler_builtins.rs +++ b/rust/compiler_builtins.rs @@ -28,7 +28,7 @@ macro_rules! define_panicking_intrinsics( ($reason: tt, { $($ident: ident, )* }) => { $( #[doc(hidden)] - #[no_mangle] + #[export_name = concat!("__rust", stringify!($ident))] pub extern "C" fn $ident() { panic!($reason); } @@ -61,3 +61,6 @@ define_panicking_intrinsics!("`u128` should not be used", { __udivti3, __umodti3, }); + +// NOTE: if you are adding a new intrinsic here, you should also add it to +// `redirect-intrinsics` in `rust/Makefile`. diff --git a/rust/helpers.c b/rust/helpers.c index b4f15eee2ffd..09a4d93f9d62 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -20,6 +20,7 @@ #include <linux/bug.h> #include <linux/build_bug.h> +#include <linux/refcount.h> __noreturn void rust_helper_BUG(void) { @@ -27,6 +28,24 @@ __noreturn void rust_helper_BUG(void) } EXPORT_SYMBOL_GPL(rust_helper_BUG); +refcount_t rust_helper_REFCOUNT_INIT(int n) +{ + return (refcount_t)REFCOUNT_INIT(n); +} +EXPORT_SYMBOL_GPL(rust_helper_REFCOUNT_INIT); + +void rust_helper_refcount_inc(refcount_t *r) +{ + refcount_inc(r); +} +EXPORT_SYMBOL_GPL(rust_helper_refcount_inc); + +bool rust_helper_refcount_dec_and_test(refcount_t *r) +{ + return refcount_dec_and_test(r); +} +EXPORT_SYMBOL_GPL(rust_helper_refcount_dec_and_test); + /* * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type * as the Rust `usize` type, so we can use it in contexts where Rust diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 53040fa9e897..223564f9f0cc 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -13,7 +13,12 @@ #![no_std] #![feature(allocator_api)] +#![feature(coerce_unsized)] #![feature(core_ffi_c)] +#![feature(dispatch_from_dyn)] +#![feature(generic_associated_types)] +#![feature(receiver_trait)] +#![feature(unsize)] // Ensure conditional compilation based on the kernel configuration works; // otherwise we may silently break things like initcall handling. @@ -31,6 +36,7 @@ mod static_assert; #[doc(hidden)] pub mod std_vendor; pub mod str; +pub mod sync; pub mod types; #[doc(hidden)] diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs index 7a90249ee9b9..0bc1c97e5604 100644 --- a/rust/kernel/prelude.rs +++ b/rust/kernel/prelude.rs @@ -11,15 +11,21 @@ //! use kernel::prelude::*; //! ``` +#[doc(no_inline)] pub use core::pin::Pin; +#[doc(no_inline)] pub use alloc::{boxed::Box, vec::Vec}; +#[doc(no_inline)] pub use macros::{module, vtable}; pub use super::build_assert; -pub use super::{dbg, pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr_notice, pr_warn}; +// `super::std_vendor` is hidden, which makes the macro inline for some reason. +#[doc(no_inline)] +pub use super::dbg; +pub use super::{pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr_notice, pr_warn}; pub use super::static_assert; diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs new file mode 100644 index 000000000000..33da23e3076d --- /dev/null +++ b/rust/kernel/sync.rs @@ -0,0 +1,10 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Synchronisation primitives. +//! +//! This module contains the kernel APIs related to synchronisation that have been ported or +//! wrapped for usage by Rust code in the kernel. + +mod arc; + +pub use arc::{Arc, ArcBorrow, UniqueArc}; diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs new file mode 100644 index 000000000000..f2f1c83d72ba --- /dev/null +++ b/rust/kernel/sync/arc.rs @@ -0,0 +1,524 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! A reference-counted pointer. +//! +//! This module implements a way for users to create reference-counted objects and pointers to +//! them. Such a pointer automatically increments and decrements the count, and drops the +//! underlying object when it reaches zero. It is also safe to use concurrently from multiple +//! threads. +//! +//! It is different from the standard library's [`Arc`] in a few ways: +//! 1. It is backed by the kernel's `refcount_t` type. +//! 2. It does not support weak references, which allows it to be half the size. +//! 3. It saturates the reference count instead of aborting when it goes over a threshold. +//! 4. It does not provide a `get_mut` method, so the ref counted object is pinned. +//! +//! [`Arc`]: https://doc.rust-lang.org/std/sync/struct.Arc.html + +use crate::{ + bindings, + error::Result, + types::{ForeignOwnable, Opaque}, +}; +use alloc::boxed::Box; +use core::{ + marker::{PhantomData, Unsize}, + mem::{ManuallyDrop, MaybeUninit}, + ops::{Deref, DerefMut}, + pin::Pin, + ptr::NonNull, +}; + +/// A reference-counted pointer to an instance of `T`. +/// +/// The reference count is incremented when new instances of [`Arc`] are created, and decremented +/// when they are dropped. When the count reaches zero, the underlying `T` is also dropped. +/// +/// # Invariants +/// +/// The reference count on an instance of [`Arc`] is always non-zero. +/// The object pointed to by [`Arc`] is always pinned. +/// +/// # Examples +/// +/// ``` +/// use kernel::sync::Arc; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// // Create a ref-counted instance of `Example`. +/// let obj = Arc::try_new(Example { a: 10, b: 20 })?; +/// +/// // Get a new pointer to `obj` and increment the refcount. +/// let cloned = obj.clone(); +/// +/// // Assert that both `obj` and `cloned` point to the same underlying object. +/// assert!(core::ptr::eq(&*obj, &*cloned)); +/// +/// // Destroy `obj` and decrement its refcount. +/// drop(obj); +/// +/// // Check that the values are still accessible through `cloned`. +/// assert_eq!(cloned.a, 10); +/// assert_eq!(cloned.b, 20); +/// +/// // The refcount drops to zero when `cloned` goes out of scope, and the memory is freed. +/// ``` +/// +/// Using `Arc<T>` as the type of `self`: +/// +/// ``` +/// use kernel::sync::Arc; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// impl Example { +/// fn take_over(self: Arc<Self>) { +/// // ... +/// } +/// +/// fn use_reference(self: &Arc<Self>) { +/// // ... +/// } +/// } +/// +/// let obj = Arc::try_new(Example { a: 10, b: 20 })?; +/// obj.use_reference(); +/// obj.take_over(); +/// ``` +/// +/// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`: +/// +/// ``` +/// use kernel::sync::{Arc, ArcBorrow}; +/// +/// trait MyTrait { +/// // Trait has a function whose `self` type is `Arc<Self>`. +/// fn example1(self: Arc<Self>) {} +/// +/// // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`. +/// fn example2(self: ArcBorrow<'_, Self>) {} +/// } +/// +/// struct Example; +/// impl MyTrait for Example {} +/// +/// // `obj` has type `Arc<Example>`. +/// let obj: Arc<Example> = Arc::try_new(Example)?; +/// +/// // `coerced` has type `Arc<dyn MyTrait>`. +/// let coerced: Arc<dyn MyTrait> = obj; +/// ``` +pub struct Arc<T: ?Sized> { + ptr: NonNull<ArcInner<T>>, + _p: PhantomData<ArcInner<T>>, +} + +#[repr(C)] +struct ArcInner<T: ?Sized> { + refcount: Opaque<bindings::refcount_t>, + data: T, +} + +// This is to allow [`Arc`] (and variants) to be used as the type of `self`. +impl<T: ?Sized> core::ops::Receiver for Arc<T> {} + +// This is to allow coercion from `Arc<T>` to `Arc<U>` if `T` can be converted to the +// dynamically-sized type (DST) `U`. +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {} + +// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`. +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {} + +// SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because +// it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs +// `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for +// example, when the reference count reaches zero and `T` is dropped. +unsafe impl<T: ?Sized + Sync + Send> Send for Arc<T> {} + +// SAFETY: It is safe to send `&Arc<T>` to another thread when the underlying `T` is `Sync` for the +// same reason as above. `T` needs to be `Send` as well because a thread can clone an `&Arc<T>` +// into an `Arc<T>`, which may lead to `T` being accessed by the same reasoning as above. +unsafe impl<T: ?Sized + Sync + Send> Sync for Arc<T> {} + +impl<T> Arc<T> { + /// Constructs a new reference counted instance of `T`. + pub fn try_new(contents: T) -> Result<Self> { + // INVARIANT: The refcount is initialised to a non-zero value. + let value = ArcInner { + // SAFETY: There are no safety requirements for this FFI call. + refcount: Opaque::new(unsafe { bindings::REFCOUNT_INIT(1) }), + data: contents, + }; + + let inner = Box::try_new(value)?; + + // SAFETY: We just created `inner` with a reference count of 1, which is owned by the new + // `Arc` object. + Ok(unsafe { Self::from_inner(Box::leak(inner).into()) }) + } +} + +impl<T: ?Sized> Arc<T> { + /// Constructs a new [`Arc`] from an existing [`ArcInner`]. + /// + /// # Safety + /// + /// The caller must ensure that `inner` points to a valid location and has a non-zero reference + /// count, one of which will be owned by the new [`Arc`] instance. + unsafe fn from_inner(inner: NonNull<ArcInner<T>>) -> Self { + // INVARIANT: By the safety requirements, the invariants hold. + Arc { + ptr: inner, + _p: PhantomData, + } + } + + /// Returns an [`ArcBorrow`] from the given [`Arc`]. + /// + /// This is useful when the argument of a function call is an [`ArcBorrow`] (e.g., in a method + /// receiver), but we have an [`Arc`] instead. Getting an [`ArcBorrow`] is free when optimised. + #[inline] + pub fn as_arc_borrow(&self) -> ArcBorrow<'_, T> { + // SAFETY: The constraint that the lifetime of the shared reference must outlive that of + // the returned `ArcBorrow` ensures that the object remains alive and that no mutable + // reference can be created. + unsafe { ArcBorrow::new(self.ptr) } + } +} + +impl<T: 'static> ForeignOwnable for Arc<T> { + type Borrowed<'a> = ArcBorrow<'a, T>; + + fn into_foreign(self) -> *const core::ffi::c_void { + ManuallyDrop::new(self).ptr.as_ptr() as _ + } + + unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> ArcBorrow<'a, T> { + // SAFETY: By the safety requirement of this function, we know that `ptr` came from + // a previous call to `Arc::into_foreign`. + let inner = NonNull::new(ptr as *mut ArcInner<T>).unwrap(); + + // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive + // for the lifetime of the returned value. Additionally, the safety requirements of + // `ForeignOwnable::borrow_mut` ensure that no new mutable references are created. + unsafe { ArcBorrow::new(inner) } + } + + unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self { + // SAFETY: By the safety requirement of this function, we know that `ptr` came from + // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and + // holds a reference count increment that is transferrable to us. + unsafe { Self::from_inner(NonNull::new(ptr as _).unwrap()) } + } +} + +impl<T: ?Sized> Deref for Arc<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is + // safe to dereference it. + unsafe { &self.ptr.as_ref().data } + } +} + +impl<T: ?Sized> Clone for Arc<T> { + fn clone(&self) -> Self { + // INVARIANT: C `refcount_inc` saturates the refcount, so it cannot overflow to zero. + // SAFETY: By the type invariant, there is necessarily a reference to the object, so it is + // safe to increment the refcount. + unsafe { bindings::refcount_inc(self.ptr.as_ref().refcount.get()) }; + + // SAFETY: We just incremented the refcount. This increment is now owned by the new `Arc`. + unsafe { Self::from_inner(self.ptr) } + } +} + +impl<T: ?Sized> Drop for Arc<T> { + fn drop(&mut self) { + // SAFETY: By the type invariant, there is necessarily a reference to the object. We cannot + // touch `refcount` after it's decremented to a non-zero value because another thread/CPU + // may concurrently decrement it to zero and free it. It is ok to have a raw pointer to + // freed/invalid memory as long as it is never dereferenced. + let refcount = unsafe { self.ptr.as_ref() }.refcount.get(); + + // INVARIANT: If the refcount reaches zero, there are no other instances of `Arc`, and + // this instance is being dropped, so the broken invariant is not observable. + // SAFETY: Also by the type invariant, we are allowed to decrement the refcount. + let is_zero = unsafe { bindings::refcount_dec_and_test(refcount) }; + if is_zero { + // The count reached zero, we must free the memory. + // + // SAFETY: The pointer was initialised from the result of `Box::leak`. + unsafe { Box::from_raw(self.ptr.as_ptr()) }; + } + } +} + +impl<T: ?Sized> From<UniqueArc<T>> for Arc<T> { + fn from(item: UniqueArc<T>) -> Self { + item.inner + } +} + +impl<T: ?Sized> From<Pin<UniqueArc<T>>> for Arc<T> { + fn from(item: Pin<UniqueArc<T>>) -> Self { + // SAFETY: The type invariants of `Arc` guarantee that the data is pinned. + unsafe { Pin::into_inner_unchecked(item).inner } + } +} + +/// A borrowed reference to an [`Arc`] instance. +/// +/// For cases when one doesn't ever need to increment the refcount on the allocation, it is simpler +/// to use just `&T`, which we can trivially get from an `Arc<T>` instance. +/// +/// However, when one may need to increment the refcount, it is preferable to use an `ArcBorrow<T>` +/// over `&Arc<T>` because the latter results in a double-indirection: a pointer (shared reference) +/// to a pointer (`Arc<T>`) to the object (`T`). An [`ArcBorrow`] eliminates this double +/// indirection while still allowing one to increment the refcount and getting an `Arc<T>` when/if +/// needed. +/// +/// # Invariants +/// +/// There are no mutable references to the underlying [`Arc`], and it remains valid for the +/// lifetime of the [`ArcBorrow`] instance. +/// +/// # Example +/// +/// ``` +/// use crate::sync::{Arc, ArcBorrow}; +/// +/// struct Example; +/// +/// fn do_something(e: ArcBorrow<'_, Example>) -> Arc<Example> { +/// e.into() +/// } +/// +/// let obj = Arc::try_new(Example)?; +/// let cloned = do_something(obj.as_arc_borrow()); +/// +/// // Assert that both `obj` and `cloned` point to the same underlying object. +/// assert!(core::ptr::eq(&*obj, &*cloned)); +/// ``` +/// +/// Using `ArcBorrow<T>` as the type of `self`: +/// +/// ``` +/// use crate::sync::{Arc, ArcBorrow}; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// impl Example { +/// fn use_reference(self: ArcBorrow<'_, Self>) { +/// // ... +/// } +/// } +/// +/// let obj = Arc::try_new(Example { a: 10, b: 20 })?; +/// obj.as_arc_borrow().use_reference(); +/// ``` +pub struct ArcBorrow<'a, T: ?Sized + 'a> { + inner: NonNull<ArcInner<T>>, + _p: PhantomData<&'a ()>, +} + +// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`. +impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {} + +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into +// `ArcBorrow<U>`. +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>> + for ArcBorrow<'_, T> +{ +} + +impl<T: ?Sized> Clone for ArcBorrow<'_, T> { + fn clone(&self) -> Self { + *self + } +} + +impl<T: ?Sized> Copy for ArcBorrow<'_, T> {} + +impl<T: ?Sized> ArcBorrow<'_, T> { + /// Creates a new [`ArcBorrow`] instance. + /// + /// # Safety + /// + /// Callers must ensure the following for the lifetime of the returned [`ArcBorrow`] instance: + /// 1. That `inner` remains valid; + /// 2. That no mutable references to `inner` are created. + unsafe fn new(inner: NonNull<ArcInner<T>>) -> Self { + // INVARIANT: The safety requirements guarantee the invariants. + Self { + inner, + _p: PhantomData, + } + } +} + +impl<T: ?Sized> From<ArcBorrow<'_, T>> for Arc<T> { + fn from(b: ArcBorrow<'_, T>) -> Self { + // SAFETY: The existence of `b` guarantees that the refcount is non-zero. `ManuallyDrop` + // guarantees that `drop` isn't called, so it's ok that the temporary `Arc` doesn't own the + // increment. + ManuallyDrop::new(unsafe { Arc::from_inner(b.inner) }) + .deref() + .clone() + } +} + +impl<T: ?Sized> Deref for ArcBorrow<'_, T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + // SAFETY: By the type invariant, the underlying object is still alive with no mutable + // references to it, so it is safe to create a shared reference. + unsafe { &self.inner.as_ref().data } + } +} + +/// A refcounted object that is known to have a refcount of 1. +/// +/// It is mutable and can be converted to an [`Arc`] so that it can be shared. +/// +/// # Invariants +/// +/// `inner` always has a reference count of 1. +/// +/// # Examples +/// +/// In the following example, we make changes to the inner object before turning it into an +/// `Arc<Test>` object (after which point, it cannot be mutated directly). Note that `x.into()` +/// cannot fail. +/// +/// ``` +/// use kernel::sync::{Arc, UniqueArc}; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// fn test() -> Result<Arc<Example>> { +/// let mut x = UniqueArc::try_new(Example { a: 10, b: 20 })?; +/// x.a += 1; +/// x.b += 1; +/// Ok(x.into()) +/// } +/// +/// # test().unwrap(); +/// ``` +/// +/// In the following example we first allocate memory for a ref-counted `Example` but we don't +/// initialise it on allocation. We do initialise it later with a call to [`UniqueArc::write`], +/// followed by a conversion to `Arc<Example>`. This is particularly useful when allocation happens +/// in one context (e.g., sleepable) and initialisation in another (e.g., atomic): +/// +/// ``` +/// use kernel::sync::{Arc, UniqueArc}; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// fn test() -> Result<Arc<Example>> { +/// let x = UniqueArc::try_new_uninit()?; +/// Ok(x.write(Example { a: 10, b: 20 }).into()) +/// } +/// +/// # test().unwrap(); +/// ``` +/// +/// In the last example below, the caller gets a pinned instance of `Example` while converting to +/// `Arc<Example>`; this is useful in scenarios where one needs a pinned reference during +/// initialisation, for example, when initialising fields that are wrapped in locks. +/// +/// ``` +/// use kernel::sync::{Arc, UniqueArc}; +/// +/// struct Example { +/// a: u32, +/// b: u32, +/// } +/// +/// fn test() -> Result<Arc<Example>> { +/// let mut pinned = Pin::from(UniqueArc::try_new(Example { a: 10, b: 20 })?); +/// // We can modify `pinned` because it is `Unpin`. +/// pinned.as_mut().a += 1; +/// Ok(pinned.into()) +/// } +/// +/// # test().unwrap(); +/// ``` +pub struct UniqueArc<T: ?Sized> { + inner: Arc<T>, +} + +impl<T> UniqueArc<T> { + /// Tries to allocate a new [`UniqueArc`] instance. + pub fn try_new(value: T) -> Result<Self> { + Ok(Self { + // INVARIANT: The newly-created object has a ref-count of 1. + inner: Arc::try_new(value)?, + }) + } + + /// Tries to allocate a new [`UniqueArc`] instance whose contents are not initialised yet. + pub fn try_new_uninit() -> Result<UniqueArc<MaybeUninit<T>>> { + Ok(UniqueArc::<MaybeUninit<T>> { + // INVARIANT: The newly-created object has a ref-count of 1. + inner: Arc::try_new(MaybeUninit::uninit())?, + }) + } +} + +impl<T> UniqueArc<MaybeUninit<T>> { + /// Converts a `UniqueArc<MaybeUninit<T>>` into a `UniqueArc<T>` by writing a value into it. + pub fn write(mut self, value: T) -> UniqueArc<T> { + self.deref_mut().write(value); + let inner = ManuallyDrop::new(self).inner.ptr; + UniqueArc { + // SAFETY: The new `Arc` is taking over `ptr` from `self.inner` (which won't be + // dropped). The types are compatible because `MaybeUninit<T>` is compatible with `T`. + inner: unsafe { Arc::from_inner(inner.cast()) }, + } + } +} + +impl<T: ?Sized> From<UniqueArc<T>> for Pin<UniqueArc<T>> { + fn from(obj: UniqueArc<T>) -> Self { + // SAFETY: It is not possible to move/replace `T` inside a `Pin<UniqueArc<T>>` (unless `T` + // is `Unpin`), so it is ok to convert it to `Pin<UniqueArc<T>>`. + unsafe { Pin::new_unchecked(obj) } + } +} + +impl<T: ?Sized> Deref for UniqueArc<T> { + type Target = T; + + fn deref(&self) -> &Self::Target { + self.inner.deref() + } +} + +impl<T: ?Sized> DerefMut for UniqueArc<T> { + fn deref_mut(&mut self) -> &mut Self::Target { + // SAFETY: By the `Arc` type invariant, there is necessarily a reference to the object, so + // it is safe to dereference it. Additionally, we know there is only one reference when + // it's inside a `UniqueArc`, so it is safe to get a mutable reference. + unsafe { &mut self.inner.ptr.as_mut().data } + } +} diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index e84e51ec9716..9d0fdbc55843 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -2,7 +2,220 @@ //! Kernel types. -use core::{cell::UnsafeCell, mem::MaybeUninit}; +use alloc::boxed::Box; +use core::{ + cell::UnsafeCell, + mem::MaybeUninit, + ops::{Deref, DerefMut}, +}; + +/// Used to transfer ownership to and from foreign (non-Rust) languages. +/// +/// Ownership is transferred from Rust to a foreign language by calling [`Self::into_foreign`] and +/// later may be transferred back to Rust by calling [`Self::from_foreign`]. +/// +/// This trait is meant to be used in cases when Rust objects are stored in C objects and +/// eventually "freed" back to Rust. +pub trait ForeignOwnable: Sized { + /// Type of values borrowed between calls to [`ForeignOwnable::into_foreign`] and + /// [`ForeignOwnable::from_foreign`]. + type Borrowed<'a>; + + /// Converts a Rust-owned object to a foreign-owned one. + /// + /// The foreign representation is a pointer to void. + fn into_foreign(self) -> *const core::ffi::c_void; + + /// Borrows a foreign-owned object. + /// + /// # Safety + /// + /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for + /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. + /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow_mut`] + /// for this object must have been dropped. + unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Self::Borrowed<'a>; + + /// Mutably borrows a foreign-owned object. + /// + /// # Safety + /// + /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for + /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. + /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and + /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped. + unsafe fn borrow_mut(ptr: *const core::ffi::c_void) -> ScopeGuard<Self, fn(Self)> { + // SAFETY: The safety requirements ensure that `ptr` came from a previous call to + // `into_foreign`. + ScopeGuard::new_with_data(unsafe { Self::from_foreign(ptr) }, |d| { + d.into_foreign(); + }) + } + + /// Converts a foreign-owned object back to a Rust-owned one. + /// + /// # Safety + /// + /// `ptr` must have been returned by a previous call to [`ForeignOwnable::into_foreign`] for + /// which a previous matching [`ForeignOwnable::from_foreign`] hasn't been called yet. + /// Additionally, all instances (if any) of values returned by [`ForeignOwnable::borrow`] and + /// [`ForeignOwnable::borrow_mut`] for this object must have been dropped. + unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self; +} + +impl<T: 'static> ForeignOwnable for Box<T> { + type Borrowed<'a> = &'a T; + + fn into_foreign(self) -> *const core::ffi::c_void { + Box::into_raw(self) as _ + } + + unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> &'a T { + // SAFETY: The safety requirements for this function ensure that the object is still alive, + // so it is safe to dereference the raw pointer. + // The safety requirements of `from_foreign` also ensure that the object remains alive for + // the lifetime of the returned value. + unsafe { &*ptr.cast() } + } + + unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self { + // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous + // call to `Self::into_foreign`. + unsafe { Box::from_raw(ptr as _) } + } +} + +impl ForeignOwnable for () { + type Borrowed<'a> = (); + + fn into_foreign(self) -> *const core::ffi::c_void { + core::ptr::NonNull::dangling().as_ptr() + } + + unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {} + + unsafe fn from_foreign(_: *const core::ffi::c_void) -> Self {} +} + +/// Runs a cleanup function/closure when dropped. +/// +/// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running. +/// +/// # Examples +/// +/// In the example below, we have multiple exit paths and we want to log regardless of which one is +/// taken: +/// ``` +/// # use kernel::ScopeGuard; +/// fn example1(arg: bool) { +/// let _log = ScopeGuard::new(|| pr_info!("example1 completed\n")); +/// +/// if arg { +/// return; +/// } +/// +/// pr_info!("Do something...\n"); +/// } +/// +/// # example1(false); +/// # example1(true); +/// ``` +/// +/// In the example below, we want to log the same message on all early exits but a different one on +/// the main exit path: +/// ``` +/// # use kernel::ScopeGuard; +/// fn example2(arg: bool) { +/// let log = ScopeGuard::new(|| pr_info!("example2 returned early\n")); +/// +/// if arg { +/// return; +/// } +/// +/// // (Other early returns...) +/// +/// log.dismiss(); +/// pr_info!("example2 no early return\n"); +/// } +/// +/// # example2(false); +/// # example2(true); +/// ``` +/// +/// In the example below, we need a mutable object (the vector) to be accessible within the log +/// function, so we wrap it in the [`ScopeGuard`]: +/// ``` +/// # use kernel::ScopeGuard; +/// fn example3(arg: bool) -> Result { +/// let mut vec = +/// ScopeGuard::new_with_data(Vec::new(), |v| pr_info!("vec had {} elements\n", v.len())); +/// +/// vec.try_push(10u8)?; +/// if arg { +/// return Ok(()); +/// } +/// vec.try_push(20u8)?; +/// Ok(()) +/// } +/// +/// # assert_eq!(example3(false), Ok(())); +/// # assert_eq!(example3(true), Ok(())); +/// ``` +/// +/// # Invariants +/// +/// The value stored in the struct is nearly always `Some(_)`, except between +/// [`ScopeGuard::dismiss`] and [`ScopeGuard::drop`]: in this case, it will be `None` as the value +/// will have been returned to the caller. Since [`ScopeGuard::dismiss`] consumes the guard, +/// callers won't be able to use it anymore. +pub struct ScopeGuard<T, F: FnOnce(T)>(Option<(T, F)>); + +impl<T, F: FnOnce(T)> ScopeGuard<T, F> { + /// Creates a new guarded object wrapping the given data and with the given cleanup function. + pub fn new_with_data(data: T, cleanup_func: F) -> Self { + // INVARIANT: The struct is being initialised with `Some(_)`. + Self(Some((data, cleanup_func))) + } + + /// Prevents the cleanup function from running and returns the guarded data. + pub fn dismiss(mut self) -> T { + // INVARIANT: This is the exception case in the invariant; it is not visible to callers + // because this function consumes `self`. + self.0.take().unwrap().0 + } +} + +impl ScopeGuard<(), fn(())> { + /// Creates a new guarded object with the given cleanup function. + pub fn new(cleanup: impl FnOnce()) -> ScopeGuard<(), impl FnOnce(())> { + ScopeGuard::new_with_data((), move |_| cleanup()) + } +} + +impl<T, F: FnOnce(T)> Deref for ScopeGuard<T, F> { + type Target = T; + + fn deref(&self) -> &T { + // The type invariants guarantee that `unwrap` will succeed. + &self.0.as_ref().unwrap().0 + } +} + +impl<T, F: FnOnce(T)> DerefMut for ScopeGuard<T, F> { + fn deref_mut(&mut self) -> &mut T { + // The type invariants guarantee that `unwrap` will succeed. + &mut self.0.as_mut().unwrap().0 + } +} + +impl<T, F: FnOnce(T)> Drop for ScopeGuard<T, F> { + fn drop(&mut self) { + // Run the cleanup function if one is still present. + if let Some((data, cleanup)) = self.0.take() { + cleanup(data) + } + } +} /// Stores an opaque value. /// |