diff options
author | Alice Ryhl <aliceryhl@google.com> | 2024-02-15 10:46:01 +0000 |
---|---|---|
committer | Miguel Ojeda <ojeda@kernel.org> | 2024-02-18 21:22:27 +0100 |
commit | 44f2e626cbf777f3035aef7fa379ce34bf2f57e8 (patch) | |
tree | f207ff52b268c938a9ad559f30879001083da55b | |
parent | e283ee239220908118d66eea46dd8bb6175767b2 (diff) |
rust: kernel: stop using ptr_metadata feature
The `byte_sub` method was stabilized in Rust 1.75.0. By using that
method, we no longer need the unstable `ptr_metadata` feature for
implementing `Arc::from_raw`.
This brings us one step closer towards not using unstable compiler
features.
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Trevor Gross <tmgross@umich.edu>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20240215104601.1267763-1-aliceryhl@google.com
[ Reworded title. ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r-- | rust/kernel/lib.rs | 1 | ||||
-rw-r--r-- | rust/kernel/sync/arc.rs | 16 |
2 files changed, 7 insertions, 10 deletions
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 74581c958a6c..1e5f229b8263 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -17,7 +17,6 @@ #![feature(dispatch_from_dyn)] #![feature(new_uninit)] #![feature(offset_of)] -#![feature(ptr_metadata)] #![feature(receiver_trait)] #![feature(unsize)] diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index 936bc549a082..7d4c4bf58388 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -30,7 +30,7 @@ use core::{ mem::{ManuallyDrop, MaybeUninit}, ops::{Deref, DerefMut}, pin::Pin, - ptr::{NonNull, Pointee}, + ptr::NonNull, }; use macros::pin_data; @@ -239,22 +239,20 @@ impl<T: ?Sized> Arc<T> { // binary, so its layout is not so large that it can trigger arithmetic overflow. let val_offset = unsafe { refcount_layout.extend(val_layout).unwrap_unchecked().1 }; - let metadata: <T as Pointee>::Metadata = core::ptr::metadata(ptr); - // SAFETY: The metadata of `T` and `ArcInner<T>` is the same because `ArcInner` is a struct - // with `T` as its last field. + // Pointer casts leave the metadata unchanged. This is okay because the metadata of `T` and + // `ArcInner<T>` is the same since `ArcInner` is a struct with `T` as its last field. // // This is documented at: // <https://doc.rust-lang.org/std/ptr/trait.Pointee.html>. - let metadata: <ArcInner<T> as Pointee>::Metadata = - unsafe { core::mem::transmute_copy(&metadata) }; + let ptr = ptr as *const ArcInner<T>; + // SAFETY: The pointer is in-bounds of an allocation both before and after offsetting the // pointer, since it originates from a previous call to `Arc::into_raw` and is still valid. - let ptr = unsafe { (ptr as *mut u8).sub(val_offset) as *mut () }; - let ptr = core::ptr::from_raw_parts_mut(ptr, metadata); + let ptr = unsafe { ptr.byte_sub(val_offset) }; // SAFETY: By the safety requirements we know that `ptr` came from `Arc::into_raw`, so the // reference count held then will be owned by the new `Arc` object. - unsafe { Self::from_inner(NonNull::new_unchecked(ptr)) } + unsafe { Self::from_inner(NonNull::new_unchecked(ptr.cast_mut())) } } /// Returns an [`ArcBorrow`] from the given [`Arc`]. |