[PATCH v4 00/28] Generic `Allocator` support for Rust

Danilo Krummrich
2024-08-05T15:20:13Z

Hi,

This patch series adds generic kernel allocator support for Rust, which so far
is limited to `kmalloc` allocations.

In order to abstain from (re-)adding unstable Rust features to the kernel, this
patch series does not extend the `Allocator` trait from Rust's `alloc` crate,
nor does it extend the `BoxExt` and `VecExt` extensions.

Instead, this series introduces a kernel specific `Allocator` trait, which is
implemented by the `Kmalloc`, `Vmalloc` and `KVmalloc` allocators, also
implemented in the context of this series.

As a consequence we need our own kernel `Box<T, A>` and `Vec<T, A>` types.
Additionally, this series adds the following type aliases:

```
pub type KBox<T> = Box<T, Kmalloc>;
pub type VBox<T> = Box<T, Vmalloc>;
pub type KVBox<T> = Box<T, KVmalloc>;

pub type KVec<T> = Vec<T, Kmalloc>;
pub type VVec<T> = Vec<T, Vmalloc>;
pub type KVVec<T> = Vec<T, KVmalloc>;
```

With that, we can start using the kernel `Box` and `Vec` types throughout the
tree and remove the now obolete extensions `BoxExt` and `VecExt`.

For a final cleanup, this series removes the last minor dependencies to Rust's
`alloc` crate and removes it from the entire kernel build.

The series ensures not to break the `rusttest` make target by implementing the
`allocator_test` module providing a stub implementation for all kernel
`Allocator`s.

This patch series passes all KUnit tests, including the ones added by this
series. Additionally, the tests were run with `kmemleak` and `KASAN` enabled,
without any issues.

This series is based on [1], which hit -mm/mm-unstable, and is also available
in [2].

[1] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=mm/krealloc
[2] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/mm

Changes in v4:
- (safety) comment fixes suggested by Alice and Boqun
- remove `Box::from_raw_alloc` and `Box::into_raw_alloc`, we don't need them
- in `Box::drop` call `size_of_val` before `drop_in_place`
- implement ForeignOwnable for Pin<Box<T>> as suggested by Alice
- in `Vec::extend_with`, iterate over `n` instead of `spare.len()`
- for `Vmalloc` and `KVmalloc` fail allocation for alignments larger than
PAGE_SIZE for now (will add support for larger alignments in a separate
series)
- implement `Cmalloc` in `allocator_test` and type alias all kernel allocator
types to it, such that we can use the kernel's `Box` and `Vec` types in
userspace tests (rusttest)
- this makes patch "rust: str: test: replace `alloc::format`" rather trivial

Changes in v3:
- Box:
- minor documentation fixes
- removed unnecessary imports in doc tests
- dropeed `self` argument from some remaining `Box` methods
- implement `InPlaceInit` for Box<T, A> rather than specifically for `KBox<T>`
- Vec:
- minor documentation fixes
- removed useless `Vec::allocator` method
- in `Vec::extend_with` use `Vec::spare_capacity_mut` instead of raw pointer operations
- added a few missing safety comments
- pass GFP flags to `Vec::collect`
- fixed a rustdoc warning in alloc.rs
- fixed the allocator_test module to implement the `Allocator` trait correctly
- rebased to rust-next

Changes in v2:
- preserve `impl GlobalAlloc for Kmalloc` and remove it at the end (Benno)
- remove `&self` parameter from all `Allocator` functions (Benno)
- various documentation fixes for `Allocator` (Benno)
- use `NonNull<u8>` for `Allocator::free` and `Option<NonNull<u8>>` for
`Allocator::realloc` (Benno)
- fix leak of `IntoIter` in `Vec::collect` (Boqun)
- always realloc (try to shrink) in `Vec::collect`, it's up the the
`Allocator` to provide a heuristic whether it makes sense to actually shrink
- rename `KBox<T, A>` -> `Box<T, A>` and `KVec<T, A>` -> `Vec<T, A>` and
provide type aliases `KBox<T>`, `VBox<T>`, `KVBox<T>`, etc.
- This allows for much cleaner code and, in combination with removing
`&self` parameters from `Allocator`s, gets us rid of the need for
`Box::new` and `Box::new_alloc` and all other "_alloc" postfixed
functions.
- Before: `KBox::new_alloc(foo, Vmalloc)?`
- After: `VBox::new(foo)?`, which resolves to
`Box::<Foo, Vmalloc>::new(foo)?;

Danilo Krummrich (28):
rust: alloc: add `Allocator` trait
rust: alloc: separate `aligned_size` from `krealloc_aligned`
rust: alloc: rename `KernelAllocator` to `Kmalloc`
rust: alloc: implement `Allocator` for `Kmalloc`
rust: alloc: add module `allocator_test`
rust: alloc: implement `Vmalloc` allocator
rust: alloc: implement `KVmalloc` allocator
rust: types: implement `Unique<T>`
rust: alloc: implement kernel `Box`
rust: treewide: switch to our kernel `Box` type
rust: alloc: remove `BoxExt` extension
rust: alloc: add `Box` to prelude
rust: alloc: import kernel `Box` type in types.rs
rust: alloc: import kernel `Box` type in init.rs
rust: alloc: implement kernel `Vec` type
rust: alloc: implement `IntoIterator` for `Vec`
rust: alloc: implement `collect` for `IntoIter`
rust: treewide: switch to the kernel `Vec` type
rust: alloc: remove `VecExt` extension
rust: alloc: add `Vec` to prelude
rust: alloc: remove `GlobalAlloc` and `krealloc_aligned`
rust: error: use `core::alloc::LayoutError`
rust: error: check for config `test` in `Error::name`
rust: alloc: implement `contains` for `Flags`
rust: alloc: implement `Cmalloc` in module allocator_test
rust: str: test: replace `alloc::format`
rust: alloc: update module comment of alloc.rs
kbuild: rust: remove the `alloc` crate

rust/Makefile | 44 +-
rust/exports.c | 1 -
rust/helpers.c | 16 +-
rust/kernel/alloc.rs | 114 +++-
rust/kernel/alloc/allocator.rs | 167 ++++--
rust/kernel/alloc/allocator_test.rs | 98 ++++
rust/kernel/alloc/box_ext.rs | 56 --
rust/kernel/alloc/kbox.rs | 344 +++++++++++
rust/kernel/alloc/kvec.rs | 855 ++++++++++++++++++++++++++++
rust/kernel/alloc/vec_ext.rs | 185 ------
rust/kernel/error.rs | 6 +-
rust/kernel/init.rs | 56 +-
rust/kernel/init/__internal.rs | 2 +-
rust/kernel/lib.rs | 1 -
rust/kernel/prelude.rs | 5 +-
rust/kernel/str.rs | 35 +-
rust/kernel/sync/arc.rs | 17 +-
rust/kernel/sync/condvar.rs | 4 +-
rust/kernel/sync/lock/mutex.rs | 2 +-
rust/kernel/sync/lock/spinlock.rs | 2 +-
rust/kernel/sync/locked_by.rs | 2 +-
rust/kernel/types.rs | 222 +++++++-
rust/kernel/uaccess.rs | 15 +-
rust/kernel/workqueue.rs | 20 +-
samples/rust/rust_minimal.rs | 4 +-
scripts/Makefile.build | 7 +-
26 files changed, 1863 insertions(+), 417 deletions(-)
create mode 100644 rust/kernel/alloc/allocator_test.rs
delete mode 100644 rust/kernel/alloc/box_ext.rs
create mode 100644 rust/kernel/alloc/kbox.rs
create mode 100644 rust/kernel/alloc/kvec.rs
delete mode 100644 rust/kernel/alloc/vec_ext.rs

base-commit: c0d669a6bbe161a3afa26dea3d8491863e352e59
--
2.45.2