rust: alloc: use `spare_capacity_mut` to reduce unsafe

Use `spare_capacity_mut` in the implementation of `push` to reduce the
use of `unsafe`. Both methods were added in commit 2aac4cd7dae3 ("rust:

rust: alloc: use `spare_capacity_mut` to reduce unsafe

Use `spare_capacity_mut` in the implementation of `push` to reduce the
use of `unsafe`. Both methods were added in commit 2aac4cd7dae3 ("rust:
alloc: implement kernel `Vec` type").

Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20250318-vec-push-use-spare-v3-1-68741671d1af@gmail.com
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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rust: alloc: add Vec::resize method

Implement the equivalent of the rust std's Vec::resize on the kernel's
Vec type.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Tamir Duberstein

rust: alloc: add Vec::resize method

Implement the equivalent of the rust std's Vec::resize on the kernel's
Vec type.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Tamir Duberstein <tamird@gmail.com>
Link: https://lore.kernel.org/r/20250316111644.154602-3-andrewjballance@gmail.com
Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
[ Use checked_sub(), as suggested by Tamir. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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rust: alloc: add Vec::truncate method

Implement the equivalent to the std's Vec::truncate on the kernel's Vec
type.

Link: https://lore.kernel.org/r/20250316111644.154602-2-andrewjballance@gmail.com

rust: alloc: add Vec::truncate method

Implement the equivalent to the std's Vec::truncate on the kernel's Vec
type.

Link: https://lore.kernel.org/r/20250316111644.154602-2-andrewjballance@gmail.com
Signed-off-by: Andrew Ballance <andrewjballance@gmail.com>
[ Rewrote safety comment of set_len(). - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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rust: alloc: add missing invariant in Vec::set_len()

When setting a new length, we have to justify that the set length
represents the exact number of elements stored in the vector.

Reviewed-by: Ben

rust: alloc: add missing invariant in Vec::set_len()

When setting a new length, we have to justify that the set length
represents the exact number of elements stored in the vector.

Reviewed-by: Benno Lossin <benno.lossin@proton.me>
Reported-by: Alice Ryhl <aliceryhl@google.com>
Closes: https://lore.kernel.org/rust-for-linux/20250311-iov-iter-v1-4-f6c9134ea824@google.com
Fixes: 2aac4cd7dae3 ("rust: alloc: implement kernel `Vec` type")
Link: https://lore.kernel.org/r/20250315154436.65065-2-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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Merge tag 'rust-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull Rust updates from Miguel Ojeda:
"Toolchain and infrastructure:

- Extract the 'pin-init' API from the 'ker

Merge tag 'rust-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux

Pull Rust updates from Miguel Ojeda:
"Toolchain and infrastructure:

- Extract the 'pin-init' API from the 'kernel' crate and make it into
a standalone crate.

In order to do this, the contents are rearranged so that they can
easily be kept in sync with the version maintained out-of-tree that
other projects have started to use too (or plan to, like QEMU).

This will reduce the maintenance burden for Benno, who will now
have his own sub-tree, and will simplify future expected changes
like the move to use 'syn' to simplify the implementation.

- Add '#[test]'-like support based on KUnit.

We already had doctests support based on KUnit, which takes the
examples in our Rust documentation and runs them under KUnit.

Now, we are adding the beginning of the support for "normal" tests,
similar to those the '#[test]' tests in userspace Rust. For
instance:

#[kunit_tests(my_suite)]
mod tests {
#[test]
fn my_test() {
assert_eq!(1 + 1, 2);
}
}

Unlike with doctests, the 'assert*!'s do not map to the KUnit
assertion APIs yet.

- Check Rust signatures at compile time for functions called from C
by name.

In particular, introduce a new '#[export]' macro that can be placed
in the Rust function definition. It will ensure that the function
declaration on the C side matches the signature on the Rust
function:

#[export]
pub unsafe extern "C" fn my_function(a: u8, b: i32) -> usize {
// ...
}

The macro essentially forces the compiler to compare the types of
the actual Rust function and the 'bindgen'-processed C signature.

These cases are rare so far. In the future, we may consider
introducing another tool, 'cbindgen', to generate C headers
automatically. Even then, having these functions explicitly marked
may be a good idea anyway.

- Enable the 'raw_ref_op' Rust feature: it is already stable, and
allows us to use the new '&raw' syntax, avoiding a couple macros.
After everyone has migrated, we will disallow the macros.

- Pass the correct target to 'bindgen' on Usermode Linux.

- Fix 'rusttest' build in macOS.

'kernel' crate:

- New 'hrtimer' module: add support for setting up intrusive timers
without allocating when starting the timer. Add support for
'Pin<Box<_>>', 'Arc<_>', 'Pin<&_>' and 'Pin<&mut _>' as pointer
types for use with timer callbacks. Add support for setting clock
source and timer mode.

- New 'dma' module: add a simple DMA coherent allocator abstraction
and a test sample driver.

- 'list' module: make the linked list 'Cursor' point between
elements, rather than at an element, which is more convenient to us
and allows for cursors to empty lists; and document it with
examples of how to perform common operations with the provided
methods.

- 'str' module: implement a few traits for 'BStr' as well as the
'strip_prefix()' method.

- 'sync' module: add 'Arc::as_ptr'.

- 'alloc' module: add 'Box::into_pin'.

- 'error' module: extend the 'Result' documentation, including a few
examples on different ways of handling errors, a warning about
using methods that may panic, and links to external documentation.

'macros' crate:

- 'module' macro: add the 'authors' key to support multiple authors.
The original key will be kept until everyone has migrated.

Documentation:

- Add error handling sections.

MAINTAINERS:

- Add Danilo Krummrich as reviewer of the Rust "subsystem".

- Add 'RUST [PIN-INIT]' entry with Benno Lossin as maintainer. It has
its own sub-tree.

- Add sub-tree for 'RUST [ALLOC]'.

- Add 'DMA MAPPING HELPERS DEVICE DRIVER API [RUST]' entry with
Abdiel Janulgue as primary maintainer. It will go through the
sub-tree of the 'RUST [ALLOC]' entry.

- Add 'HIGH-RESOLUTION TIMERS [RUST]' entry with Andreas Hindborg as
maintainer. It has its own sub-tree.

And a few other cleanups and improvements"

* tag 'rust-6.15' of git://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux: (71 commits)
rust: dma: add `Send` implementation for `CoherentAllocation`
rust: macros: fix `make rusttest` build on macOS
rust: block: refactor to use `&raw mut`
rust: enable `raw_ref_op` feature
rust: uaccess: name the correct function
rust: rbtree: fix comments referring to Box instead of KBox
rust: hrtimer: add maintainer entry
rust: hrtimer: add clocksource selection through `ClockId`
rust: hrtimer: add `HrTimerMode`
rust: hrtimer: implement `HrTimerPointer` for `Pin<Box<T>>`
rust: alloc: add `Box::into_pin`
rust: hrtimer: implement `UnsafeHrTimerPointer` for `Pin<&mut T>`
rust: hrtimer: implement `UnsafeHrTimerPointer` for `Pin<&T>`
rust: hrtimer: add `hrtimer::ScopedHrTimerPointer`
rust: hrtimer: add `UnsafeHrTimerPointer`
rust: hrtimer: allow timer restart from timer handler
rust: str: implement `strip_prefix` for `BStr`
rust: str: implement `AsRef<BStr>` for `[u8]` and `BStr`
rust: str: implement `Index` for `BStr`
rust: str: implement `PartialEq` for `BStr`
...

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