mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 13:55:32 +00:00
![Miguel Ojeda](/assets/img/avatar_default.png)
This is the first upgrade to the Rust toolchain since the initial Rust
merge, from 1.62.0 to 1.68.2 (i.e. the latest).
# Context
The kernel currently supports only a single Rust version [1] (rather
than a minimum) given our usage of some "unstable" Rust features [2]
which do not promise backwards compatibility.
The goal is to reach a point where we can declare a minimum version for
the toolchain. For instance, by waiting for some of the features to be
stabilized. Therefore, the first minimum Rust version that the kernel
will support is "in the future".
# Upgrade policy
Given we will eventually need to reach that minimum version, it would be
ideal to upgrade the compiler from time to time to be as close as
possible to that goal and find any issues sooner. In the extreme, we
could upgrade as soon as a new Rust release is out. Of course, upgrading
so often is in stark contrast to what one normally would need for GCC
and LLVM, especially given the release schedule: 6 weeks for Rust vs.
half a year for LLVM and a year for GCC.
Having said that, there is no particular advantage to updating slowly
either: kernel developers in "stable" distributions are unlikely to be
able to use their distribution-provided Rust toolchain for the kernel
anyway [3]. Instead, by routinely upgrading to the latest instead,
kernel developers using Linux distributions that track the latest Rust
release may be able to use those rather than Rust-provided ones,
especially if their package manager allows to pin / hold back /
downgrade the version for some days during windows where the version may
not match. For instance, Arch, Fedora, Gentoo and openSUSE all provide
and track the latest version of Rust as they get released every 6 weeks.
Then, when the minimum version is reached, we will stop upgrading and
decide how wide the window of support will be. For instance, a year of
Rust versions. We will probably want to start small, and then widen it
over time, just like the kernel did originally for LLVM, see commit
3519c4d6e0
("Documentation: add minimum clang/llvm version").
# Unstable features stabilized
This upgrade allows us to remove the following unstable features since
they were stabilized:
- `feature(explicit_generic_args_with_impl_trait)` (1.63).
- `feature(core_ffi_c)` (1.64).
- `feature(generic_associated_types)` (1.65).
- `feature(const_ptr_offset_from)` (1.65, *).
- `feature(bench_black_box)` (1.66, *).
- `feature(pin_macro)` (1.68).
The ones marked with `*` apply only to our old `rust` branch, not
mainline yet, i.e. only for code that we may potentially upstream.
With this patch applied, the only unstable feature allowed to be used
outside the `kernel` crate is `new_uninit`, though other code to be
upstreamed may increase the list.
Please see [2] for details.
# Other required changes
Since 1.63, `rustdoc` triggers the `broken_intra_doc_links` lint for
links pointing to exported (`#[macro_export]`) `macro_rules`. An issue
was opened upstream [4], but it turns out it is intended behavior. For
the moment, just add an explicit reference for each link. Later we can
revisit this if `rustdoc` removes the compatibility measure.
Nevertheless, this was helpful to discover a link that was pointing to
the wrong place unintentionally. Since that one was actually wrong, it
is fixed in a previous commit independently.
Another change was the addition of `cfg(no_rc)` and `cfg(no_sync)` in
upstream [5], thus remove our original changes for that.
Similarly, upstream now tests that it compiles successfully with
`#[cfg(not(no_global_oom_handling))]` [6], which allow us to get rid
of some changes, such as an `#[allow(dead_code)]`.
In addition, remove another `#[allow(dead_code)]` due to new uses
within the standard library.
Finally, add `try_extend_trusted` and move the code in `spec_extend.rs`
since upstream moved it for the infallible version.
# `alloc` upgrade and reviewing
There are a large amount of changes, but the vast majority of them are
due to our `alloc` fork being upgraded at once.
There are two kinds of changes to be aware of: the ones coming from
upstream, which we should follow as closely as possible, and the updates
needed in our added fallible APIs to keep them matching the newer
infallible APIs coming from upstream.
Instead of taking a look at the diff of this patch, an alternative
approach is reviewing a diff of the changes between upstream `alloc` and
the kernel's. This allows to easily inspect the kernel additions only,
especially to check if the fallible methods we already have still match
the infallible ones in the new version coming from upstream.
Another approach is reviewing the changes introduced in the additions in
the kernel fork between the two versions. This is useful to spot
potentially unintended changes to our additions.
To apply these approaches, one may follow steps similar to the following
to generate a pair of patches that show the differences between upstream
Rust and the kernel (for the subset of `alloc` we use) before and after
applying this patch:
# Get the difference with respect to the old version.
git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
cut -d/ -f3- |
grep -Fv README.md |
xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
git -C linux diff --patch-with-stat --summary -R > old.patch
git -C linux restore rust/alloc
# Apply this patch.
git -C linux am rust-upgrade.patch
# Get the difference with respect to the new version.
git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
cut -d/ -f3- |
grep -Fv README.md |
xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
git -C linux diff --patch-with-stat --summary -R > new.patch
git -C linux restore rust/alloc
Now one may check the `new.patch` to take a look at the additions (first
approach) or at the difference between those two patches (second
approach). For the latter, a side-by-side tool is recommended.
Link: https://rust-for-linux.com/rust-version-policy [1]
Link: https://github.com/Rust-for-Linux/linux/issues/2 [2]
Link: https://lore.kernel.org/rust-for-linux/CANiq72mT3bVDKdHgaea-6WiZazd8Mvurqmqegbe5JZxVyLR8Yg@mail.gmail.com/ [3]
Link: https://github.com/rust-lang/rust/issues/106142 [4]
Link: https://github.com/rust-lang/rust/pull/89891 [5]
Link: https://github.com/rust-lang/rust/pull/98652 [6]
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-By: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Tested-by: Ariel Miculas <amiculas@cisco.com>
Tested-by: David Gow <davidgow@google.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20230418214347.324156-4-ojeda@kernel.org
[ Removed `feature(core_ffi_c)` from `uapi` ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
435 lines
15 KiB
Rust
435 lines
15 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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#[cfg(not(no_global_oom_handling))]
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use super::AsVecIntoIter;
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use crate::alloc::{Allocator, Global};
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#[cfg(not(no_global_oom_handling))]
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use crate::collections::VecDeque;
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use crate::raw_vec::RawVec;
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use core::array;
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use core::fmt;
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use core::iter::{
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FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
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};
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use core::marker::PhantomData;
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use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
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#[cfg(not(no_global_oom_handling))]
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use core::ops::Deref;
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use core::ptr::{self, NonNull};
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use core::slice::{self};
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/// An iterator that moves out of a vector.
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///
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/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
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/// (provided by the [`IntoIterator`] trait).
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///
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/// # Example
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///
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/// ```
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/// let v = vec![0, 1, 2];
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/// let iter: std::vec::IntoIter<_> = v.into_iter();
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[rustc_insignificant_dtor]
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pub struct IntoIter<
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T,
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#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
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> {
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pub(super) buf: NonNull<T>,
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pub(super) phantom: PhantomData<T>,
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pub(super) cap: usize,
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// the drop impl reconstructs a RawVec from buf, cap and alloc
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// to avoid dropping the allocator twice we need to wrap it into ManuallyDrop
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pub(super) alloc: ManuallyDrop<A>,
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pub(super) ptr: *const T,
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pub(super) end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
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// ptr == end is a quick test for the Iterator being empty, that works
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// for both ZST and non-ZST.
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}
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#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
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impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
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}
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}
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impl<T, A: Allocator> IntoIter<T, A> {
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/// Returns the remaining items of this iterator as a slice.
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///
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/// # Examples
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///
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/// ```
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/// let vec = vec!['a', 'b', 'c'];
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/// let mut into_iter = vec.into_iter();
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/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
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/// let _ = into_iter.next().unwrap();
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/// assert_eq!(into_iter.as_slice(), &['b', 'c']);
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/// ```
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#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
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pub fn as_slice(&self) -> &[T] {
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unsafe { slice::from_raw_parts(self.ptr, self.len()) }
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}
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/// Returns the remaining items of this iterator as a mutable slice.
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///
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/// # Examples
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///
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/// ```
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/// let vec = vec!['a', 'b', 'c'];
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/// let mut into_iter = vec.into_iter();
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/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
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/// into_iter.as_mut_slice()[2] = 'z';
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/// assert_eq!(into_iter.next().unwrap(), 'a');
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/// assert_eq!(into_iter.next().unwrap(), 'b');
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/// assert_eq!(into_iter.next().unwrap(), 'z');
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/// ```
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#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
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pub fn as_mut_slice(&mut self) -> &mut [T] {
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unsafe { &mut *self.as_raw_mut_slice() }
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}
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/// Returns a reference to the underlying allocator.
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[inline]
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pub fn allocator(&self) -> &A {
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&self.alloc
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}
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fn as_raw_mut_slice(&mut self) -> *mut [T] {
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ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
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}
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/// Drops remaining elements and relinquishes the backing allocation.
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/// This method guarantees it won't panic before relinquishing
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/// the backing allocation.
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///
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/// This is roughly equivalent to the following, but more efficient
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///
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/// ```
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/// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
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/// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter());
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/// (&mut into_iter).for_each(core::mem::drop);
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/// std::mem::forget(into_iter);
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/// ```
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///
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/// This method is used by in-place iteration, refer to the vec::in_place_collect
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/// documentation for an overview.
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#[cfg(not(no_global_oom_handling))]
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pub(super) fn forget_allocation_drop_remaining(&mut self) {
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let remaining = self.as_raw_mut_slice();
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// overwrite the individual fields instead of creating a new
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// struct and then overwriting &mut self.
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// this creates less assembly
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self.cap = 0;
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self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
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self.ptr = self.buf.as_ptr();
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self.end = self.buf.as_ptr();
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// Dropping the remaining elements can panic, so this needs to be
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// done only after updating the other fields.
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unsafe {
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ptr::drop_in_place(remaining);
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}
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}
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/// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
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pub(crate) fn forget_remaining_elements(&mut self) {
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// For th ZST case, it is crucial that we mutate `end` here, not `ptr`.
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// `ptr` must stay aligned, while `end` may be unaligned.
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self.end = self.ptr;
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}
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#[cfg(not(no_global_oom_handling))]
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#[inline]
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pub(crate) fn into_vecdeque(self) -> VecDeque<T, A> {
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// Keep our `Drop` impl from dropping the elements and the allocator
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let mut this = ManuallyDrop::new(self);
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// SAFETY: This allocation originally came from a `Vec`, so it passes
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// all those checks. We have `this.buf` ≤ `this.ptr` ≤ `this.end`,
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// so the `sub_ptr`s below cannot wrap, and will produce a well-formed
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// range. `end` ≤ `buf + cap`, so the range will be in-bounds.
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// Taking `alloc` is ok because nothing else is going to look at it,
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// since our `Drop` impl isn't going to run so there's no more code.
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unsafe {
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let buf = this.buf.as_ptr();
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let initialized = if T::IS_ZST {
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// All the pointers are the same for ZSTs, so it's fine to
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// say that they're all at the beginning of the "allocation".
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0..this.len()
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} else {
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this.ptr.sub_ptr(buf)..this.end.sub_ptr(buf)
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};
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let cap = this.cap;
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let alloc = ManuallyDrop::take(&mut this.alloc);
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VecDeque::from_contiguous_raw_parts_in(buf, initialized, cap, alloc)
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}
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}
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}
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#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
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impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
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fn as_ref(&self) -> &[T] {
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self.as_slice()
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
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#[stable(feature = "rust1", since = "1.0.0")]
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unsafe impl<T: Sync, A: Allocator + Sync> Sync for IntoIter<T, A> {}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, A: Allocator> Iterator for IntoIter<T, A> {
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type Item = T;
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#[inline]
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fn next(&mut self) -> Option<T> {
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if self.ptr == self.end {
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None
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} else if T::IS_ZST {
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// `ptr` has to stay where it is to remain aligned, so we reduce the length by 1 by
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// reducing the `end`.
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self.end = self.end.wrapping_byte_sub(1);
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// Make up a value of this ZST.
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Some(unsafe { mem::zeroed() })
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} else {
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let old = self.ptr;
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self.ptr = unsafe { self.ptr.add(1) };
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Some(unsafe { ptr::read(old) })
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}
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}
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#[inline]
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fn size_hint(&self) -> (usize, Option<usize>) {
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let exact = if T::IS_ZST {
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self.end.addr().wrapping_sub(self.ptr.addr())
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} else {
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unsafe { self.end.sub_ptr(self.ptr) }
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};
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(exact, Some(exact))
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}
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#[inline]
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fn advance_by(&mut self, n: usize) -> Result<(), usize> {
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let step_size = self.len().min(n);
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let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
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if T::IS_ZST {
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// See `next` for why we sub `end` here.
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self.end = self.end.wrapping_byte_sub(step_size);
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} else {
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// SAFETY: the min() above ensures that step_size is in bounds
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self.ptr = unsafe { self.ptr.add(step_size) };
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}
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// SAFETY: the min() above ensures that step_size is in bounds
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unsafe {
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ptr::drop_in_place(to_drop);
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}
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if step_size < n {
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return Err(step_size);
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}
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Ok(())
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}
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#[inline]
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fn count(self) -> usize {
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self.len()
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}
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#[inline]
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fn next_chunk<const N: usize>(&mut self) -> Result<[T; N], core::array::IntoIter<T, N>> {
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let mut raw_ary = MaybeUninit::uninit_array();
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let len = self.len();
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if T::IS_ZST {
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if len < N {
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self.forget_remaining_elements();
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// Safety: ZSTs can be conjured ex nihilo, only the amount has to be correct
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return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
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}
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self.end = self.end.wrapping_byte_sub(N);
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// Safety: ditto
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return Ok(unsafe { raw_ary.transpose().assume_init() });
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}
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if len < N {
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// Safety: `len` indicates that this many elements are available and we just checked that
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// it fits into the array.
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unsafe {
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ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, len);
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self.forget_remaining_elements();
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return Err(array::IntoIter::new_unchecked(raw_ary, 0..len));
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}
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}
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// Safety: `len` is larger than the array size. Copy a fixed amount here to fully initialize
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// the array.
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return unsafe {
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ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, N);
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self.ptr = self.ptr.add(N);
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Ok(raw_ary.transpose().assume_init())
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};
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}
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unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
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where
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Self: TrustedRandomAccessNoCoerce,
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{
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// SAFETY: the caller must guarantee that `i` is in bounds of the
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// `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
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// is guaranteed to pointer to an element of the `Vec<T>` and
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// thus guaranteed to be valid to dereference.
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//
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// Also note the implementation of `Self: TrustedRandomAccess` requires
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// that `T: Copy` so reading elements from the buffer doesn't invalidate
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// them for `Drop`.
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unsafe {
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if T::IS_ZST { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
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}
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
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#[inline]
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fn next_back(&mut self) -> Option<T> {
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if self.end == self.ptr {
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None
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} else if T::IS_ZST {
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// See above for why 'ptr.offset' isn't used
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self.end = self.end.wrapping_byte_sub(1);
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// Make up a value of this ZST.
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Some(unsafe { mem::zeroed() })
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} else {
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self.end = unsafe { self.end.sub(1) };
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Some(unsafe { ptr::read(self.end) })
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}
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}
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#[inline]
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fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
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let step_size = self.len().min(n);
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if T::IS_ZST {
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// SAFETY: same as for advance_by()
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self.end = self.end.wrapping_byte_sub(step_size);
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} else {
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// SAFETY: same as for advance_by()
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self.end = unsafe { self.end.sub(step_size) };
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}
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let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
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// SAFETY: same as for advance_by()
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unsafe {
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ptr::drop_in_place(to_drop);
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}
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if step_size < n {
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return Err(step_size);
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}
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Ok(())
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
|
|
fn is_empty(&self) -> bool {
|
|
self.ptr == self.end
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "fused", since = "1.26.0")]
|
|
impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
|
|
|
|
#[unstable(feature = "trusted_len", issue = "37572")]
|
|
unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
|
|
|
|
#[doc(hidden)]
|
|
#[unstable(issue = "none", feature = "std_internals")]
|
|
#[rustc_unsafe_specialization_marker]
|
|
pub trait NonDrop {}
|
|
|
|
// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
|
|
// and thus we can't implement drop-handling
|
|
#[unstable(issue = "none", feature = "std_internals")]
|
|
impl<T: Copy> NonDrop for T {}
|
|
|
|
#[doc(hidden)]
|
|
#[unstable(issue = "none", feature = "std_internals")]
|
|
// TrustedRandomAccess (without NoCoerce) must not be implemented because
|
|
// subtypes/supertypes of `T` might not be `NonDrop`
|
|
unsafe impl<T, A: Allocator> TrustedRandomAccessNoCoerce for IntoIter<T, A>
|
|
where
|
|
T: NonDrop,
|
|
{
|
|
const MAY_HAVE_SIDE_EFFECT: bool = false;
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
|
|
impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
|
|
#[cfg(not(test))]
|
|
fn clone(&self) -> Self {
|
|
self.as_slice().to_vec_in(self.alloc.deref().clone()).into_iter()
|
|
}
|
|
#[cfg(test)]
|
|
fn clone(&self) -> Self {
|
|
crate::slice::to_vec(self.as_slice(), self.alloc.deref().clone()).into_iter()
|
|
}
|
|
}
|
|
|
|
#[stable(feature = "rust1", since = "1.0.0")]
|
|
unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
|
|
fn drop(&mut self) {
|
|
struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
|
|
|
|
impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
|
|
fn drop(&mut self) {
|
|
unsafe {
|
|
// `IntoIter::alloc` is not used anymore after this and will be dropped by RawVec
|
|
let alloc = ManuallyDrop::take(&mut self.0.alloc);
|
|
// RawVec handles deallocation
|
|
let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
|
|
}
|
|
}
|
|
}
|
|
|
|
let guard = DropGuard(self);
|
|
// destroy the remaining elements
|
|
unsafe {
|
|
ptr::drop_in_place(guard.0.as_raw_mut_slice());
|
|
}
|
|
// now `guard` will be dropped and do the rest
|
|
}
|
|
}
|
|
|
|
// In addition to the SAFETY invariants of the following three unsafe traits
|
|
// also refer to the vec::in_place_collect module documentation to get an overview
|
|
#[unstable(issue = "none", feature = "inplace_iteration")]
|
|
#[doc(hidden)]
|
|
unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
|
|
|
|
#[unstable(issue = "none", feature = "inplace_iteration")]
|
|
#[doc(hidden)]
|
|
unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
|
|
type Source = Self;
|
|
|
|
#[inline]
|
|
unsafe fn as_inner(&mut self) -> &mut Self::Source {
|
|
self
|
|
}
|
|
}
|
|
|
|
#[cfg(not(no_global_oom_handling))]
|
|
unsafe impl<T> AsVecIntoIter for IntoIter<T> {
|
|
type Item = T;
|
|
|
|
fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
|
|
self
|
|
}
|
|
}
|