rust: alloc: remove our fork of the `alloc` crate (9d0441ba) · Commits · git / linux-net

rust/alloc/README.md

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		# `alloc`

		These source files come from the Rust standard library, hosted in
		the <https://github.com/rust-lang/rust> repository, licensed under
		"Apache-2.0 OR MIT" and adapted for kernel use. For copyright details,
		see <https://github.com/rust-lang/rust/blob/master/COPYRIGHT>.

		Please note that these files should be kept as close as possible to
		upstream. In general, only additions should be performed (e.g. new
		methods). Eventually, changes should make it into upstream so that,
		at some point, this fork can be dropped from the kernel tree.

		The Rust upstream version on top of which these files are based matches
		the output of `scripts/min-tool-version.sh rustc`.


		## Rationale

		On one hand, kernel folks wanted to keep `alloc` in-tree to have more
		freedom in both workflow and actual features if actually needed
		(e.g. receiver types if we ended up using them), which is reasonable.

		On the other hand, Rust folks wanted to keep `alloc` as close as
		upstream as possible and avoid as much divergence as possible, which
		is also reasonable.

		We agreed on a middle-ground: we would keep a subset of `alloc`
		in-tree that would be as small and as close as possible to upstream.
		Then, upstream can start adding the functions that we add to `alloc`
		etc., until we reach a point where the kernel already knows exactly
		what it needs in `alloc` and all the new methods are merged into
		upstream, so that we can drop `alloc` from the kernel tree and go back
		to using the upstream one.

		By doing this, the kernel can go a bit faster now, and Rust can
		slowly incorporate and discuss the changes as needed.

rust/alloc/alloc.rs

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		// SPDX-License-Identifier: Apache-2.0 OR MIT

		//! Memory allocation APIs

		#![stable(feature = "alloc_module", since = "1.28.0")]

		#[cfg(not(test))]
		use core::hint;

		#[cfg(not(test))]
		use core::ptr::{self, NonNull};

		#[stable(feature = "alloc_module", since = "1.28.0")]
		#[doc(inline)]
		pub use core::alloc::*;

		#[cfg(test)]
		mod tests;

		extern "Rust" {
		// These are the magic symbols to call the global allocator. rustc generates
		// them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
		// (the code expanding that attribute macro generates those functions), or to call
		// the default implementations in std (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
		// otherwise.
		// The rustc fork of LLVM 14 and earlier also special-cases these function names to be able to optimize them
		// like `malloc`, `realloc`, and `free`, respectively.
		#[rustc_allocator]
		#[rustc_nounwind]
		fn __rust_alloc(size: usize, align: usize) -> *mut u8;
		#[rustc_deallocator]
		#[rustc_nounwind]
		fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
		#[rustc_reallocator]
		#[rustc_nounwind]
		fn __rust_realloc(ptr: mut u8, old_size: usize, align: usize, new_size: usize) -> mut u8;
		#[rustc_allocator_zeroed]
		#[rustc_nounwind]
		fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;

		static __rust_no_alloc_shim_is_unstable: u8;
		}

		/// The global memory allocator.
		///
		/// This type implements the [`Allocator`] trait by forwarding calls
		/// to the allocator registered with the `#[global_allocator]` attribute
		/// if there is one, or the `std` crate’s default.
		///
		/// Note: while this type is unstable, the functionality it provides can be
		/// accessed through the [free functions in `alloc`](self#functions).
		#[unstable(feature = "allocator_api", issue = "32838")]
		#[derive(Copy, Clone, Default, Debug)]
		#[cfg(not(test))]
		pub struct Global;

		#[cfg(test)]
		pub use std::alloc::Global;

		/// Allocate memory with the global allocator.
		///
		/// This function forwards calls to the [`GlobalAlloc::alloc`] method
		/// of the allocator registered with the `#[global_allocator]` attribute
		/// if there is one, or the `std` crate’s default.
		///
		/// This function is expected to be deprecated in favor of the `alloc` method
		/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
		///
		/// # Safety
		///
		/// See [`GlobalAlloc::alloc`].
		///
		/// # Examples
		///
		/// ```
		/// use std::alloc::{alloc, dealloc, handle_alloc_error, Layout};
		///
		/// unsafe {
		/// let layout = Layout::new::<u16>();
		/// let ptr = alloc(layout);
		/// if ptr.is_null() {
		/// handle_alloc_error(layout);
		/// }
		///
		/// (ptr as mut u16) = 42;
		/// assert_eq!((ptr as mut u16), 42);
		///
		/// dealloc(ptr, layout);
		/// }
		/// ```
		#[stable(feature = "global_alloc", since = "1.28.0")]
		#[must_use = "losing the pointer will leak memory"]
		#[inline]
		pub unsafe fn alloc(layout: Layout) -> *mut u8 {
		unsafe {
		// Make sure we don't accidentally allow omitting the allocator shim in
		// stable code until it is actually stabilized.
		core::ptr::read_volatile(&__rust_no_alloc_shim_is_unstable);

		__rust_alloc(layout.size(), layout.align())
		}
		}

		/// Deallocate memory with the global allocator.
		///
		/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
		/// of the allocator registered with the `#[global_allocator]` attribute
		/// if there is one, or the `std` crate’s default.
		///
		/// This function is expected to be deprecated in favor of the `dealloc` method
		/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
		///
		/// # Safety
		///
		/// See [`GlobalAlloc::dealloc`].
		#[stable(feature = "global_alloc", since = "1.28.0")]
		#[inline]
		pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
		unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
		}

		/// Reallocate memory with the global allocator.
		///
		/// This function forwards calls to the [`GlobalAlloc::realloc`] method
		/// of the allocator registered with the `#[global_allocator]` attribute
		/// if there is one, or the `std` crate’s default.
		///
		/// This function is expected to be deprecated in favor of the `realloc` method
		/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
		///
		/// # Safety
		///
		/// See [`GlobalAlloc::realloc`].
		#[stable(feature = "global_alloc", since = "1.28.0")]
		#[must_use = "losing the pointer will leak memory"]
		#[inline]
		pub unsafe fn realloc(ptr: mut u8, layout: Layout, new_size: usize) -> mut u8 {
		unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
		}

		/// Allocate zero-initialized memory with the global allocator.
		///
		/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
		/// of the allocator registered with the `#[global_allocator]` attribute
		/// if there is one, or the `std` crate’s default.
		///
		/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
		/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
		///
		/// # Safety
		///
		/// See [`GlobalAlloc::alloc_zeroed`].
		///
		/// # Examples
		///
		/// ```
		/// use std::alloc::{alloc_zeroed, dealloc, Layout};
		///
		/// unsafe {
		/// let layout = Layout::new::<u16>();
		/// let ptr = alloc_zeroed(layout);
		///
		/// assert_eq!((ptr as mut u16), 0);
		///
		/// dealloc(ptr, layout);
		/// }
		/// ```
		#[stable(feature = "global_alloc", since = "1.28.0")]
		#[must_use = "losing the pointer will leak memory"]
		#[inline]
		pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
		unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
		}

		#[cfg(not(test))]
		impl Global {
		#[inline]
		fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
		match layout.size() {
		0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
		// SAFETY: `layout` is non-zero in size,
		size => unsafe {
		let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
		let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
		Ok(NonNull::slice_from_raw_parts(ptr, size))
		},
		}
		}

		// SAFETY: Same as `Allocator::grow`
		#[inline]
		unsafe fn grow_impl(
		&self,
		ptr: NonNull<u8>,
		old_layout: Layout,
		new_layout: Layout,
		zeroed: bool,
		) -> Result<NonNull<[u8]>, AllocError> {
		debug_assert!(
		new_layout.size() >= old_layout.size(),
		"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
		);

		match old_layout.size() {
		0 => self.alloc_impl(new_layout, zeroed),

		// SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
		// as required by safety conditions. Other conditions must be upheld by the caller
		old_size if old_layout.align() == new_layout.align() => unsafe {
		let new_size = new_layout.size();

		// `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
		hint::assert_unchecked(new_size >= old_layout.size());

		let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
		let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
		if zeroed {
		raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
		}
		Ok(NonNull::slice_from_raw_parts(ptr, new_size))
		},

		// SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
		// both the old and new memory allocation are valid for reads and writes for `old_size`
		// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
		// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
		// for `dealloc` must be upheld by the caller.
		old_size => unsafe {
		let new_ptr = self.alloc_impl(new_layout, zeroed)?;
		ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
		self.deallocate(ptr, old_layout);
		Ok(new_ptr)
		},
		}
		}
		}

		#[unstable(feature = "allocator_api", issue = "32838")]
		#[cfg(not(test))]
		unsafe impl Allocator for Global {
		#[inline]
		fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
		self.alloc_impl(layout, false)
		}

		#[inline]
		fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
		self.alloc_impl(layout, true)
		}

		#[inline]
		unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
		if layout.size() != 0 {
		// SAFETY: `layout` is non-zero in size,
		// other conditions must be upheld by the caller
		unsafe { dealloc(ptr.as_ptr(), layout) }
		}
		}

		#[inline]
		unsafe fn grow(
		&self,
		ptr: NonNull<u8>,
		old_layout: Layout,
		new_layout: Layout,
		) -> Result<NonNull<[u8]>, AllocError> {
		// SAFETY: all conditions must be upheld by the caller
		unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
		}

		#[inline]
		unsafe fn grow_zeroed(
		&self,
		ptr: NonNull<u8>,
		old_layout: Layout,
		new_layout: Layout,
		) -> Result<NonNull<[u8]>, AllocError> {
		// SAFETY: all conditions must be upheld by the caller
		unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
		}

		#[inline]
		unsafe fn shrink(
		&self,
		ptr: NonNull<u8>,
		old_layout: Layout,
		new_layout: Layout,
		) -> Result<NonNull<[u8]>, AllocError> {
		debug_assert!(
		new_layout.size() <= old_layout.size(),
		"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
		);

		match new_layout.size() {
		// SAFETY: conditions must be upheld by the caller
		0 => unsafe {
		self.deallocate(ptr, old_layout);
		Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
		},

		// SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
		new_size if old_layout.align() == new_layout.align() => unsafe {
		// `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
		hint::assert_unchecked(new_size <= old_layout.size());

		let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
		let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
		Ok(NonNull::slice_from_raw_parts(ptr, new_size))
		},

		// SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
		// both the old and new memory allocation are valid for reads and writes for `new_size`
		// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
		// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
		// for `dealloc` must be upheld by the caller.
		new_size => unsafe {
		let new_ptr = self.allocate(new_layout)?;
		ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
		self.deallocate(ptr, old_layout);
		Ok(new_ptr)
		},
		}
		}
		}

		/// The allocator for unique pointers.
		#[cfg(all(not(no_global_oom_handling), not(test)))]
		#[lang = "exchange_malloc"]
		#[inline]
		unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
		let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
		match Global.allocate(layout) {
		Ok(ptr) => ptr.as_mut_ptr(),
		Err(_) => handle_alloc_error(layout),
		}
		}

		// # Allocation error handler

		#[cfg(not(no_global_oom_handling))]
		extern "Rust" {
		// This is the magic symbol to call the global alloc error handler. rustc generates
		// it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
		// default implementations below (`__rdl_oom`) otherwise.
		fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
		}

		/// Signal a memory allocation error.
		///
		/// Callers of memory allocation APIs wishing to cease execution
		/// in response to an allocation error are encouraged to call this function,
		/// rather than directly invoking [`panic!`] or similar.
		///
		/// This function is guaranteed to diverge (not return normally with a value), but depending on
		/// global configuration, it may either panic (resulting in unwinding or aborting as per
		/// configuration for all panics), or abort the process (with no unwinding).
		///
		/// The default behavior is:
		///
		/// * If the binary links against `std` (typically the case), then
		/// print a message to standard error and abort the process.
		/// This behavior can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
		/// Future versions of Rust may panic by default instead.
		///
		/// * If the binary does not link against `std` (all of its crates are marked
		/// [`#![no_std]`][no_std]), then call [`panic!`] with a message.
		/// [The panic handler] applies as to any panic.
		///
		/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
		/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
		/// [The panic handler]: https://doc.rust-lang.org/reference/runtime.html#the-panic_handler-attribute
		/// [no_std]: https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute
		#[stable(feature = "global_alloc", since = "1.28.0")]
		#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
		#[cfg(all(not(no_global_oom_handling), not(test)))]
		#[cold]
		pub const fn handle_alloc_error(layout: Layout) -> ! {
		const fn ct_error(_: Layout) -> ! {
		panic!("allocation failed");
		}

		#[inline]
		fn rt_error(layout: Layout) -> ! {
		unsafe {
		__rust_alloc_error_handler(layout.size(), layout.align());
		}
		}

		#[cfg(not(feature = "panic_immediate_abort"))]
		unsafe {
		core::intrinsics::const_eval_select((layout,), ct_error, rt_error)
		}

		#[cfg(feature = "panic_immediate_abort")]
		ct_error(layout)
		}

		// For alloc test `std::alloc::handle_alloc_error` can be used directly.
		#[cfg(all(not(no_global_oom_handling), test))]
		pub use std::alloc::handle_alloc_error;

		#[cfg(all(not(no_global_oom_handling), not(test)))]
		#[doc(hidden)]
		#[allow(unused_attributes)]
		#[unstable(feature = "alloc_internals", issue = "none")]
		pub mod __alloc_error_handler {
		// called via generated `__rust_alloc_error_handler` if there is no
		// `#[alloc_error_handler]`.
		#[rustc_std_internal_symbol]
		pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {
		extern "Rust" {
		// This symbol is emitted by rustc next to __rust_alloc_error_handler.
		// Its value depends on the -Zoom={panic,abort} compiler option.
		static __rust_alloc_error_handler_should_panic: u8;
		}

		if unsafe { __rust_alloc_error_handler_should_panic != 0 } {
		panic!("memory allocation of {size} bytes failed")
		} else {
		core::panicking::panic_nounwind_fmt(
		format_args!("memory allocation of {size} bytes failed"),
		/* force_no_backtrace */ false,
		)
		}
		}
		}

		#[cfg(not(no_global_oom_handling))]
		/// Specialize clones into pre-allocated, uninitialized memory.
		/// Used by `Box::clone` and `Rc`/`Arc::make_mut`.
		pub(crate) trait WriteCloneIntoRaw: Sized {
		unsafe fn write_clone_into_raw(&self, target: *mut Self);
		}

		#[cfg(not(no_global_oom_handling))]
		impl<T: Clone> WriteCloneIntoRaw for T {
		#[inline]
		default unsafe fn write_clone_into_raw(&self, target: *mut Self) {
		// Having allocated first may allow the optimizer to create
		// the cloned value in-place, skipping the local and move.
		unsafe { target.write(self.clone()) };
		}
		}

		#[cfg(not(no_global_oom_handling))]
		impl<T: Copy> WriteCloneIntoRaw for T {
		#[inline]
		unsafe fn write_clone_into_raw(&self, target: *mut Self) {
		// We can always copy in-place, without ever involving a local value.
		unsafe { target.copy_from_nonoverlapping(self, 1) };
		}
		}

rust/alloc/boxed.rs

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rust/alloc/collections/mod.rs

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		// SPDX-License-Identifier: Apache-2.0 OR MIT

		//! Collection types.

		#![stable(feature = "rust1", since = "1.0.0")]

		#[cfg(not(no_global_oom_handling))]
		pub mod binary_heap;
		#[cfg(not(no_global_oom_handling))]
		mod btree;
		#[cfg(not(no_global_oom_handling))]
		pub mod linked_list;
		#[cfg(not(no_global_oom_handling))]
		pub mod vec_deque;

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		pub mod btree_map {
		//! An ordered map based on a B-Tree.
		#[stable(feature = "rust1", since = "1.0.0")]
		pub use super::btree::map::*;
		}

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		pub mod btree_set {
		//! An ordered set based on a B-Tree.
		#[stable(feature = "rust1", since = "1.0.0")]
		pub use super::btree::set::*;
		}

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		#[doc(no_inline)]
		pub use binary_heap::BinaryHeap;

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		#[doc(no_inline)]
		pub use btree_map::BTreeMap;

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		#[doc(no_inline)]
		pub use btree_set::BTreeSet;

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		#[doc(no_inline)]
		pub use linked_list::LinkedList;

		#[cfg(not(no_global_oom_handling))]
		#[stable(feature = "rust1", since = "1.0.0")]
		#[doc(no_inline)]
		pub use vec_deque::VecDeque;

		use crate::alloc::{Layout, LayoutError};
		use core::fmt::Display;

		/// The error type for `try_reserve` methods.
		#[derive(Clone, PartialEq, Eq, Debug)]
		#[stable(feature = "try_reserve", since = "1.57.0")]
		pub struct TryReserveError {
		kind: TryReserveErrorKind,
		}

		impl TryReserveError {
		/// Details about the allocation that caused the error
		#[inline]
		#[must_use]
		#[unstable(
		feature = "try_reserve_kind",
		reason = "Uncertain how much info should be exposed",
		issue = "48043"
		)]
		pub fn kind(&self) -> TryReserveErrorKind {
		self.kind.clone()
		}
		}

		/// Details of the allocation that caused a `TryReserveError`
		#[derive(Clone, PartialEq, Eq, Debug)]
		#[unstable(
		feature = "try_reserve_kind",
		reason = "Uncertain how much info should be exposed",
		issue = "48043"
		)]
		pub enum TryReserveErrorKind {
		/// Error due to the computed capacity exceeding the collection's maximum
		/// (usually `isize::MAX` bytes).
		CapacityOverflow,

		/// The memory allocator returned an error
		AllocError {
		/// The layout of allocation request that failed
		layout: Layout,

		#[doc(hidden)]
		#[unstable(
		feature = "container_error_extra",
		issue = "none",
		reason = "\
		Enable exposing the allocator’s custom error value \
		if an associated type is added in the future: \
		https://github.com/rust-lang/wg-allocators/issues/23"
		)]
		non_exhaustive: (),
		},
		}

		#[unstable(
		feature = "try_reserve_kind",
		reason = "Uncertain how much info should be exposed",
		issue = "48043"
		)]
		impl From<TryReserveErrorKind> for TryReserveError {
		#[inline]
		fn from(kind: TryReserveErrorKind) -> Self {
		Self { kind }
		}
		}

		#[unstable(feature = "try_reserve_kind", reason = "new API", issue = "48043")]
		impl From<LayoutError> for TryReserveErrorKind {
		/// Always evaluates to [`TryReserveErrorKind::CapacityOverflow`].
		#[inline]
		fn from(_: LayoutError) -> Self {
		TryReserveErrorKind::CapacityOverflow
		}
		}

		#[stable(feature = "try_reserve", since = "1.57.0")]
		impl Display for TryReserveError {
		fn fmt(
		&self,
		fmt: &mut core::fmt::Formatter<'_>,
		) -> core::result::Result<(), core::fmt::Error> {
		fmt.write_str("memory allocation failed")?;
		let reason = match self.kind {
		TryReserveErrorKind::CapacityOverflow => {
		" because the computed capacity exceeded the collection's maximum"
		}
		TryReserveErrorKind::AllocError { .. } => {
		" because the memory allocator returned an error"
		}
		};
		fmt.write_str(reason)
		}
		}

		/// An intermediate trait for specialization of `Extend`.
		#[doc(hidden)]
		#[cfg(not(no_global_oom_handling))]
		trait SpecExtend<I: IntoIterator> {
		/// Extends `self` with the contents of the given iterator.
		fn spec_extend(&mut self, iter: I);
		}

		#[stable(feature = "try_reserve", since = "1.57.0")]
		impl core::error::Error for TryReserveError {}

rust/alloc/lib.rs

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