[PATCH v7 11/26] rust: alloc: remove extension of std's `Box`

Danilo Krummrich
2024-09-11T22:55:59Z

Now that all existing `Box` users were moved to the kernel `Box` type,
remove the `BoxExt` extension and all other related extensions.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
rust/kernel/alloc.rs | 1 -
rust/kernel/alloc/box_ext.rs | 87 ------------------------------------
rust/kernel/init.rs | 46 +------------------
rust/kernel/lib.rs | 1 -
rust/kernel/prelude.rs | 4 +-
rust/kernel/types.rs | 50 ---------------------
6 files changed, 3 insertions(+), 186 deletions(-)
delete mode 100644 rust/kernel/alloc/box_ext.rs

diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs
index b1f28334b27a..1d0cb6f12af9 100644
--- a/rust/kernel/alloc.rs
+++ b/rust/kernel/alloc.rs
@@ -4,7 +4,6 @@

#[cfg(not(any(test, testlib)))]
pub mod allocator;
-pub mod box_ext;
pub mod kbox;
pub mod vec_ext;

diff --git a/rust/kernel/alloc/box_ext.rs b/rust/kernel/alloc/box_ext.rs
deleted file mode 100644
index 5b1550d620fd..000000000000
--- a/rust/kernel/alloc/box_ext.rs
+++ /dev/null
@@ -1,87 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-
-//! Extensions to [`Box`] for fallible allocations.
-
-use super::{AllocError, Flags};
-use alloc::boxed::Box;
-use core::{mem::MaybeUninit, ptr, result::Result};
-
-/// Extensions to [`Box`].
-pub trait BoxExt<T>: Sized {
- /// Allocates a new box.
- ///
- /// The allocation may fail, in which case an error is returned.
- fn new(x: T, flags: Flags) -> Result<Self, AllocError>;
-
- /// Allocates a new uninitialised box.
- ///
- /// The allocation may fail, in which case an error is returned.
- fn new_uninit(flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError>;
-
- /// Drops the contents, but keeps the allocation.
- ///
- /// # Examples
- ///
- /// ```
- /// use kernel::alloc::{flags, box_ext::BoxExt};
- /// let value = Box::new([0; 32], flags::GFP_KERNEL)?;
- /// assert_eq!(*value, [0; 32]);
- /// let mut value = Box::drop_contents(value);
- /// // Now we can re-use `value`:
- /// value.write([1; 32]);
- /// // SAFETY: We just wrote to it.
- /// let value = unsafe { value.assume_init() };
- /// assert_eq!(*value, [1; 32]);
- /// # Ok::<(), Error>(())
- /// ```
- fn drop_contents(this: Self) -> Box<MaybeUninit<T>>;
-}
-
-impl<T> BoxExt<T> for Box<T> {
- fn new(x: T, flags: Flags) -> Result<Self, AllocError> {
- let b = <Self as BoxExt<_>>::new_uninit(flags)?;
- Ok(Box::write(b, x))
- }
-
- #[cfg(any(test, testlib))]
- fn new_uninit(_flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError> {
- Ok(Box::new_uninit())
- }
-
- #[cfg(not(any(test, testlib)))]
- fn new_uninit(flags: Flags) -> Result<Box<MaybeUninit<T>>, AllocError> {
- let ptr = if core::mem::size_of::<MaybeUninit<T>>() == 0 {
- core::ptr::NonNull::<_>::dangling().as_ptr()
- } else {
- let layout = core::alloc::Layout::new::<MaybeUninit<T>>();
-
- // SAFETY: Memory is being allocated (first arg is null). The only other source of
- // safety issues is sleeping on atomic context, which is addressed by klint. Lastly,
- // the type is not a SZT (checked above).
- let ptr =
- unsafe { super::allocator::krealloc_aligned(core::ptr::null_mut(), layout, flags) };
- if ptr.is_null() {
- return Err(AllocError);
- }
-
- ptr.cast::<MaybeUninit<T>>()
- };
-
- // SAFETY: For non-zero-sized types, we allocate above using the global allocator. For
- // zero-sized types, we use `NonNull::dangling`.
- Ok(unsafe { Box::from_raw(ptr) })
- }
-
- fn drop_contents(this: Self) -> Box<MaybeUninit<T>> {
- let ptr = Box::into_raw(this);
- // SAFETY: `ptr` is valid, because it came from `Box::into_raw`.
- unsafe { ptr::drop_in_place(ptr) };
-
- // CAST: `MaybeUninit<T>` is a transparent wrapper of `T`.
- let ptr = ptr.cast::<MaybeUninit<T>>();
-
- // SAFETY: `ptr` is valid for writes, because it came from `Box::into_raw` and it is valid for
- // reads, since the pointer came from `Box::into_raw` and the type is `MaybeUninit<T>`.
- unsafe { Box::from_raw(ptr) }
- }
-}
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index e057b374f255..2f562642e9a4 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -211,13 +211,12 @@
//! [`pin_init!`]: crate::pin_init!

use crate::{
- alloc::{box_ext::BoxExt, AllocError, Flags, KBox},
+ alloc::{AllocError, Flags, KBox},
error::{self, Error},
sync::Arc,
sync::UniqueArc,
types::{Opaque, ScopeGuard},
};
-use alloc::boxed::Box;
use core::{
cell::UnsafeCell,
convert::Infallible,
@@ -590,7 +589,6 @@ macro_rules! pin_init {
/// # Examples
///
/// ```rust
-/// # #![feature(new_uninit)]
/// use kernel::{init::{self, PinInit}, error::Error};
/// #[pin_data]
/// struct BigBuf {
@@ -1244,26 +1242,6 @@ fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
}
}

-impl<T> InPlaceInit<T> for Box<T> {
- type PinnedSelf = Pin<Self>;
-
- #[inline]
- fn try_pin_init<E>(init: impl PinInit<T, E>, flags: Flags) -> Result<Self::PinnedSelf, E>
- where
- E: From<AllocError>,
- {
- <Box<_> as BoxExt<_>>::new_uninit(flags)?.write_pin_init(init)
- }
-
- #[inline]
- fn try_init<E>(init: impl Init<T, E>, flags: Flags) -> Result<Self, E>
- where
- E: From<AllocError>,
- {
- <Box<_> as BoxExt<_>>::new_uninit(flags)?.write_init(init)
- }
-}
-
impl<T> InPlaceInit<T> for UniqueArc<T> {
type PinnedSelf = Pin<Self>;

@@ -1300,28 +1278,6 @@ pub trait InPlaceWrite<T> {
fn write_pin_init<E>(self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E>;
}

-impl<T> InPlaceWrite<T> for Box<MaybeUninit<T>> {
- type Initialized = Box<T>;
-
- fn write_init<E>(mut self, init: impl Init<T, E>) -> Result<Self::Initialized, E> {
- let slot = self.as_mut_ptr();
- // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
- // slot is valid.
- unsafe { init.__init(slot)? };
- // SAFETY: All fields have been initialized.
- Ok(unsafe { self.assume_init() })
- }
-
- fn write_pin_init<E>(mut self, init: impl PinInit<T, E>) -> Result<Pin<Self::Initialized>, E> {
- let slot = self.as_mut_ptr();
- // SAFETY: When init errors/panics, slot will get deallocated but not dropped,
- // slot is valid and will not be moved, because we pin it later.
- unsafe { init.__pinned_init(slot)? };
- // SAFETY: All fields have been initialized.
- Ok(unsafe { self.assume_init() }.into())
- }
-}
-
impl<T> InPlaceWrite<T> for UniqueArc<MaybeUninit<T>> {
type Initialized = UniqueArc<T>;

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index f10b06a78b9d..eb5c593acfc0 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -14,7 +14,6 @@
#![no_std]
#![feature(coerce_unsized)]
#![feature(dispatch_from_dyn)]
-#![feature(new_uninit)]
#![feature(receiver_trait)]
#![feature(unsize)]

diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index a9210634a8c3..c1f8e5c832e2 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -14,10 +14,10 @@
#[doc(no_inline)]
pub use core::pin::Pin;

-pub use crate::alloc::{box_ext::BoxExt, flags::*, vec_ext::VecExt, KBox, KVBox, VBox};
+pub use crate::alloc::{flags::*, vec_ext::VecExt, KBox, KVBox, VBox};

#[doc(no_inline)]
-pub use alloc::{boxed::Box, vec::Vec};
+pub use alloc::vec::Vec;

#[doc(no_inline)]
pub use macros::{module, pin_data, pinned_drop, vtable, Zeroable};
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 9e7ca066355c..53d3ddc0b98c 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -3,13 +3,11 @@
//! Kernel types.

use crate::init::{self, PinInit};
-use alloc::boxed::Box;
use core::{
cell::UnsafeCell,
marker::{PhantomData, PhantomPinned},
mem::{ManuallyDrop, MaybeUninit},
ops::{Deref, DerefMut},
- pin::Pin,
ptr::NonNull,
};

@@ -71,54 +69,6 @@ unsafe fn try_from_foreign(ptr: *const core::ffi::c_void) -> Option<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<T: 'static> ForeignOwnable for Pin<Box<T>> {
- type Borrowed<'a> = Pin<&'a T>;
-
- fn into_foreign(self) -> *const core::ffi::c_void {
- // SAFETY: We are still treating the box as pinned.
- Box::into_raw(unsafe { Pin::into_inner_unchecked(self) }) as _
- }
-
- unsafe fn borrow<'a>(ptr: *const core::ffi::c_void) -> Pin<&'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.
- let r = unsafe { &*ptr.cast() };
-
- // SAFETY: This pointer originates from a `Pin<Box<T>>`.
- unsafe { Pin::new_unchecked(r) }
- }
-
- 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 { Pin::new_unchecked(Box::from_raw(ptr as _)) }
- }
-}
-
impl ForeignOwnable for () {
type Borrowed<'a> = ();

--
2.46.0