* Re: [PATCH v6 01/10] rust: module: move module types into `module.rs`
From: Gary Guo @ 2026-06-25 14:37 UTC (permalink / raw)
To: Alvin Sun, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Luis Chamberlain, Petr Pavlu,
Daniel Gomez, Sami Tolvanen, Aaron Tomlin, Greg Kroah-Hartman,
Rafael J. Wysocki, David Airlie, Simona Vetter, Daniel Almeida,
Arnd Bergmann, Brendan Higgins, David Gow, Rae Moar, Breno Leitao,
Jens Axboe, Dave Ertman, Leon Romanovsky, Igor Korotin,
FUJITA Tomonori, Bjorn Helgaas, Krzysztof Wilczyński,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas
Cc: rust-for-linux, linux-modules, driver-core, dri-devel, nova-gpu,
linux-kselftest, kunit-dev, linux-block, linux-kernel, netdev,
linux-pci
In-Reply-To: <20260624-fix-fops-owner-v6-1-5295e333cb3e@linux.dev>
On Wed Jun 24, 2026 at 4:00 PM BST, Alvin Sun wrote:
> Move `Module`, `InPlaceModule`, `ModuleMetadata` and `ThisModule` from
> `lib.rs` into a new `rust/kernel/module.rs`. Re-export them from `lib.rs`
> to avoid tree-wide changes.
>
> Switch six bus driver registrations from `module.0` to the public
> `ThisModule::as_ptr()` accessor, since the field is no longer visible
> outside the new `module` submodule.
>
> No functional change.
>
> Assisted-by: opencode:glm-5.2
> Acked-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Alvin Sun <alvin.sun@linux.dev>
Suggested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/all/DJFIQPLOVO4T.1K8T0VZM30LDA@garyguo.net/
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> rust/kernel/auxiliary.rs | 2 +-
> rust/kernel/i2c.rs | 2 +-
> rust/kernel/lib.rs | 75 +++++-------------------------------------------
> rust/kernel/module.rs | 71 +++++++++++++++++++++++++++++++++++++++++++++
> rust/kernel/net/phy.rs | 6 +++-
> rust/kernel/pci.rs | 2 +-
> rust/kernel/platform.rs | 2 +-
> rust/kernel/usb.rs | 2 +-
> 8 files changed, 88 insertions(+), 74 deletions(-)
^ permalink raw reply
* Re: [PATCH v3 5/7] rust: devres: add DevresLt for ForLt-aware device resource access
From: Gary Guo @ 2026-06-25 14:31 UTC (permalink / raw)
To: Danilo Krummrich, gregkh, rafael, ojeda, boqun, gary, bjorn3_gh,
lossin, a.hindborg, aliceryhl, tmgross, acourbot, ecourtney,
m.wilczynski, david.m.ertman, ira.weiny, leon, daniel.almeida,
bhelgaas, kwilczynski
Cc: driver-core, linux-kernel, nova-gpu, dri-devel, linux-pwm,
rust-for-linux
In-Reply-To: <20260618230834.812007-6-dakr@kernel.org>
On Fri Jun 19, 2026 at 12:08 AM BST, Danilo Krummrich wrote:
> Devres<T> stores resources as T and returns &'a T from access(). For
> lifetime-parameterized types like Bar<'a, SIZE> that are transmuted to
> 'static for storage, this exposes the synthetic 'static lifetime to
> callers -- any method on the stored type that returns a reference with
> its lifetime parameter would yield a &'static reference, which is
> unsound.
>
> Add DevresLt<F: ForLt>, a thin wrapper around Devres<F::Of<'static>>
> that shortens the stored 'static lifetime to the caller's borrow
> lifetime in all access methods.
>
> DevresLt::new() is unsafe because the caller must guarantee that the
> data remains valid for the device's full bound scope; the internal
> transmute from F::Of<'a> to F::Of<'static> would otherwise allow
> use-after-free.
>
> Two access patterns are provided:
>
> - CovariantForLt types get direct-reference accessors (access,
> try_access) that return shortened references via
> CovariantForLt::cast_ref.
>
> - Plain ForLt types use closure-based accessors (access_with,
> try_access_with) whose universally quantified lifetime prevents
> callers from smuggling in concrete short-lived references.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
> rust/kernel/devres.rs | 100 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 100 insertions(+)
>
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index 11ce500e9b76..e11deff3e1be 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -24,6 +24,8 @@
> Arc, //
> },
> types::{
> + CovariantForLt,
> + ForLt,
> ForeignOwnable,
> Opaque, //
> },
> @@ -365,6 +367,104 @@ fn drop(&mut self) {
> }
> }
>
> +/// Guard returned by [`DevresLt::try_access`].
> +///
> +/// Dereferences to `F::Of<'a>`, shortening the lifetime of the stored data to the guard's borrow
> +/// lifetime.
> +pub struct DevresGuard<'a, F: CovariantForLt>(RevocableGuard<'a, F::Of<'static>>);
> +
> +impl<'a, F: CovariantForLt> core::ops::Deref for DevresGuard<'a, F> {
> + type Target = F::Of<'a>;
> +
> + fn deref(&self) -> &Self::Target {
> + F::cast_ref(&*self.0)
> + }
> +}
> +
> +/// Device-managed resource with [`ForLt`](trait@ForLt)-aware access.
> +///
> +/// `DevresLt` wraps [`Devres`] and shortens the stored `'static` lifetime to the caller's borrow
> +/// lifetime in all access methods.
> +///
> +/// Types that implement [`trait@CovariantForLt`] get direct-reference accessors ([`Self::access`],
> +/// [`Self::try_access`]). Plain [`ForLt`](trait@ForLt) types use closure-based accessors
> +/// ([`Self::access_with`], [`Self::try_access_with`]).
> +pub struct DevresLt<F: ForLt>(Devres<F::Of<'static>>)
> +where
> + F::Of<'static>: Send;
This bound looks weird. I know this is to satisfy `Devres`'s bound, but I think
this should actually read:
for<'a> F::Of<'a>: Send
Best,
Gary
> +
> +impl<F: ForLt> DevresLt<F>
> +where
> + F::Of<'static>: Send,
> +{
> + /// Creates a new [`DevresLt`] instance of the given `data`.
> + ///
> + /// # Safety
> + ///
> + /// The data must remain valid for the device's full bound scope. [`DevresLt`] allows
> + /// access until the device is unbound, which may outlast `'a`.
> + pub unsafe fn new<'a, E>(
> + dev: &'a Device<Bound>,
> + data: impl PinInit<F::Of<'a>, E>,
> + ) -> Result<Self>
> + where
> + Error: From<E>,
> + {
> + // SAFETY: The caller guarantees the data is valid for the device's full bound scope.
> + // Lifetimes do not affect layout, so F::Of<'a> and F::Of<'static> have identical
> + // representation; casting the slot pointer is sound.
> + let data = unsafe {
> + pin_init::pin_init_from_closure::<F::Of<'static>, E>(move |slot| {
> + data.__pinned_init(slot.cast())
> + })
> + };
> +
> + Ok(Self(Devres::new(dev, data)?))
> + }
> +
> + /// Return a reference of the [`Device`] this [`DevresLt`] instance has been created with.
> + pub fn device(&self) -> &Device {
> + self.0.device()
> + }
> +
> + /// Obtain `&F::Of<'_>`, bypassing the [`Revocable`], through a closure.
> + ///
> + /// This method works like [`DevresLt::access`](DevresLt::access) but accepts any
> + /// [`trait@ForLt`] type, not just [`trait@CovariantForLt`].
> + pub fn access_with<R, G>(&self, dev: &Device<Bound>, f: G) -> Result<R>
> + where
> + G: for<'a> FnOnce(&F::Of<'a>) -> R,
> + {
> + self.0.access(dev).map(f)
> + }
> +
> + /// [`DevresLt`] accessor for [`Revocable::try_access_with`].
> + pub fn try_access_with<R, G>(&self, f: G) -> Option<R>
> + where
> + G: for<'a> FnOnce(&F::Of<'a>) -> R,
> + {
> + self.0.data().try_access_with(f)
> + }
> +}
> +
> +impl<F: CovariantForLt> DevresLt<F>
> +where
> + F::Of<'static>: Send,
> +{
> + /// Obtain `&'a F::Of<'a>`, bypassing the [`Revocable`].
> + ///
> + /// This method works like [`Devres::access`], but shortens the returned reference's lifetime
> + /// from `'static` to `'a` via [`CovariantForLt::cast_ref`].
> + pub fn access<'a>(&'a self, dev: &'a Device<Bound>) -> Result<&'a F::Of<'a>> {
> + self.0.access(dev).map(F::cast_ref)
> + }
> +
> + /// [`DevresLt`] accessor for [`Revocable::try_access`].
> + pub fn try_access(&self) -> Option<DevresGuard<'_, F>> {
> + self.0.data().try_access().map(DevresGuard)
> + }
> +}
> +
> /// Consume `data` and [`Drop::drop`] `data` once `dev` is unbound.
> fn register_foreign<P>(dev: &Device<Bound>, data: P) -> Result
> where
^ permalink raw reply
* Re: [PATCH v3 4/7] rust: auxiliary: sample: demonstrate ForLt with invariant Mutex type
From: Gary Guo @ 2026-06-25 14:28 UTC (permalink / raw)
To: Danilo Krummrich, gregkh, rafael, ojeda, boqun, gary, bjorn3_gh,
lossin, a.hindborg, aliceryhl, tmgross, acourbot, ecourtney,
m.wilczynski, david.m.ertman, iweiny, leon, daniel.almeida,
bhelgaas, kwilczynski
Cc: driver-core, linux-kernel, nova-gpu, dri-devel, linux-pwm,
rust-for-linux
In-Reply-To: <20260618230834.812007-5-dakr@kernel.org>
On Fri Jun 19, 2026 at 12:08 AM BST, Danilo Krummrich wrote:
> Extend the auxiliary driver sample to demonstrate both access patterns:
>
> - registration_data() with CovariantForLt!(Data<'_>) for the covariant
> data type that holds a plain &'bound reference.
>
> - registration_data_with() with ForLt!(MutexData<'_>) for an invariant
> data type that wraps a Mutex<&'bound Device>. Since Mutex<T> is
> invariant over T, MutexData cannot implement CovariantForLt and must
> use the closure-based accessor.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> samples/rust/rust_driver_auxiliary.rs | 94 +++++++++++++++++++--------
> 1 file changed, 68 insertions(+), 26 deletions(-)
^ permalink raw reply
* Re: [PATCH v3 3/7] rust: auxiliary: add registration_data_with() for ForLt types
From: Gary Guo @ 2026-06-25 14:25 UTC (permalink / raw)
To: Danilo Krummrich, gregkh, rafael, ojeda, boqun, gary, bjorn3_gh,
lossin, a.hindborg, aliceryhl, tmgross, acourbot, ecourtney,
m.wilczynski, david.m.ertman, ira.weiny, leon, daniel.almeida,
bhelgaas, kwilczynski
Cc: driver-core, linux-kernel, nova-gpu, dri-devel, linux-pwm,
rust-for-linux
In-Reply-To: <20260618230834.812007-4-dakr@kernel.org>
On Fri Jun 19, 2026 at 12:08 AM BST, Danilo Krummrich wrote:
> Add registration_data_with() taking a for<'a> closure that receives
> Pin<&'a F::Of<'a>>, which works with any ForLt type. Taking a for<'a>
> closure rather than returning a direct reference prevents callers from
> choosing a concrete lifetime for the data, which is required for
> soundness with non-covariant ForLt types.
>
> Extract the common null-check, TypeId-check and KBox-borrow logic into a
> private registration_data_pinned() helper shared by both
> registration_data_with() and the existing registration_data().
>
> Relax Registration's bound from CovariantForLt to ForLt so that
> non-covariant types can be registered.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> rust/kernel/auxiliary.rs | 91 ++++++++++++++++++++++++++++------------
> 1 file changed, 65 insertions(+), 26 deletions(-)
^ permalink raw reply
* Re: [PATCH v18 4/8] rust: page: convert to `Ownable`
From: Gary Guo @ 2026-06-25 13:32 UTC (permalink / raw)
To: Andreas Hindborg, Danilo Krummrich, Lorenzo Stoakes,
Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda,
Boqun Feng, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Lyude Paul,
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Christian Brauner, Carlos Llamas, Rafael J. Wysocki, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
David Airlie, Simona Vetter, Alexander Viro, Jan Kara,
Igor Korotin, Viresh Kumar, Nishanth Menon, Stephen Boyd,
Bjorn Helgaas, Krzysztof Wilczyński, Pavel Tikhomirov,
Michal Wilczynski
Cc: Philipp Stanner, rust-for-linux, linux-kernel, linux-mm,
driver-core, linux-block, linux-security-module, dri-devel,
linux-fsdevel, linux-pm, linux-pci, linux-pwm, Asahi Lina
In-Reply-To: <20260625-unique-ref-v18-4-4e06b5896d47@kernel.org>
On Thu Jun 25, 2026 at 11:15 AM BST, Andreas Hindborg wrote:
> From: Asahi Lina <lina@asahilina.net>
>
> This allows Page references to be returned as borrowed references,
> without necessarily owning the struct page.
>
> Remove `BorrowedPage` and update users to use `Owned<Page>`.
>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> [ Andreas: Fix formatting and add a safety comment, update users. ]
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Nice to see `BorrowedPage` going away.
Reviewed-by: Gary Guo <gary@garyguo.net>
> ---
> drivers/android/binder/page_range.rs | 10 +--
> rust/kernel/alloc/allocator.rs | 19 +++---
> rust/kernel/alloc/allocator/iter.rs | 6 +-
> rust/kernel/page.rs | 122 +++++++++--------------------------
> 4 files changed, 46 insertions(+), 111 deletions(-)
^ permalink raw reply
* Re: [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned`
From: Gary Guo @ 2026-06-25 13:29 UTC (permalink / raw)
To: Andreas Hindborg, Danilo Krummrich, Lorenzo Stoakes,
Vlastimil Babka, Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda,
Boqun Feng, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, Lyude Paul,
Greg Kroah-Hartman, Arve Hjønnevåg, Todd Kjos,
Christian Brauner, Carlos Llamas, Rafael J. Wysocki, Dave Ertman,
Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
David Airlie, Simona Vetter, Alexander Viro, Jan Kara,
Igor Korotin, Viresh Kumar, Nishanth Menon, Stephen Boyd,
Bjorn Helgaas, Krzysztof Wilczyński, Pavel Tikhomirov,
Michal Wilczynski
Cc: Philipp Stanner, rust-for-linux, linux-kernel, linux-mm,
driver-core, linux-block, linux-security-module, dri-devel,
linux-fsdevel, linux-pm, linux-pci, linux-pwm
In-Reply-To: <20260625-unique-ref-v18-3-4e06b5896d47@kernel.org>
On Thu Jun 25, 2026 at 11:15 AM BST, Andreas Hindborg wrote:
> Implement `ForeignOwnable` for `Owned<T>`. This allows use of `Owned<T>` in
> places such as the `XArray`.
>
> Note that `T` does not need to implement `ForeignOwnable` for `Owned<T>` to
> implement `ForeignOwnable`.
>
> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
> ---
> rust/kernel/owned.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 53 insertions(+)
>
> diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
> index 7fe9ec3e55126..9c92d4a83cc1b 100644
> --- a/rust/kernel/owned.rs
> +++ b/rust/kernel/owned.rs
> @@ -15,6 +15,8 @@
> ptr::NonNull, //
> };
>
> +use kernel::types::ForeignOwnable;
> +
> /// Types that specify their own way of performing allocation and destruction. Typically, this trait
> /// is implemented on types from the C side.
> ///
> @@ -186,3 +188,54 @@ fn drop(&mut self) {
> unsafe { T::release(self.ptr) };
> }
> }
> +
> +// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned
> +// pointer satisfy alignment requirements of `T`.
> +unsafe impl<T: Ownable> ForeignOwnable for Owned<T> {
> + const FOREIGN_ALIGN: usize = core::mem::align_of::<T>();
> +
> + type Borrowed<'a>
> + = &'a T
> + where
> + Self: 'a;
> + type BorrowedMut<'a>
> + = Pin<&'a mut T>
> + where
> + Self: 'a;
> +
> + #[inline]
> + fn into_foreign(self) -> *mut kernel::ffi::c_void {
> + let ptr = self.ptr.as_ptr().cast();
> + core::mem::forget(self);
> + ptr
I think the pattern in `into_raw` is better:
ManuallyDrop::new(self).ptr.as_ptr().cast()
Or perhaps this can just use `Self::into_raw(self).as_ptr().cast()`.
> + }
> +
> + #[inline]
> + unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self {
> + // INVARIANT: By the function safety contract, `ptr` was returned by `into_foreign`, which
> + // gave up exclusive ownership of a valid, pinned `T`; we retake that ownership here.
> + Self {
> + // SAFETY: By function safety contract, `ptr` came from
> + // `into_foreign` and cannot be null.
> + ptr: unsafe { NonNull::new_unchecked(ptr.cast()) },
> + }
> + }
Same here, could be using `Self::from_raw`.
However, the current code looks correct to me regardless, so:
Reviewed-by: Gary Guo <gary@garyguo.net>
Best,
Gary
> +
> + #[inline]
> + unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> {
> + // SAFETY: By function safety requirements, `ptr` is valid for use as a
> + // reference for `'a`.
> + unsafe { &*ptr.cast() }
> + }
> +
> + #[inline]
> + unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> {
> + // SAFETY: By function safety requirements, `ptr` is valid for use as a
> + // unique reference for `'a`.
> + let inner = unsafe { &mut *ptr.cast() };
> +
> + // SAFETY: We never move out of inner, and we do not hand out mutable
> + // references when `T: !Unpin`.
> + unsafe { Pin::new_unchecked(inner) }
> + }
> +}
^ permalink raw reply
* Re: [PATCH v18 2/8] rust: types: Add Ownable/Owned types
From: Andreas Hindborg @ 2026-06-25 12:24 UTC (permalink / raw)
To: sashiko-reviews; +Cc: dri-devel, linux-pci, ojeda, rust-for-linux
In-Reply-To: <20260625102450.7611D1F000E9@smtp.kernel.org>
<sashiko-bot@kernel.org> writes:
> Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
> - [High] `Owned<T>` unconditionally structurally pins `T` by exposing `Pin<&mut T>`, but its API lacks the necessary documentation and safety bounds to enforce the pinning invariants. Specifically, `Owned::from_raw(ptr)` takes ownership without requiring the caller to promise the memory is or can be pinned; `Owned::into_raw(me)` safely extracts the pointer without documenting that the returned pointer's referent is still pinned; and `Ownable::release(this)` doesn't forbid the implementer from moving the pinned `Self` before dropping it. This omission allows an `Ownable` implementer or a user correctly following the explicit safety contracts to accidentally move a pinned `!Unpin` type, resulting in undefined behavior.
> --
>
> commit b7329ea2c0525ffa6a63171ede0921ad2e6a23e5
> Author: Asahi Lina <lina+kernel@asahilina.net>
>
> rust: types: Add Ownable/Owned types
>
> This commit introduces Ownable and Owned types for unique owned pointers
> with custom drop logic. These types allow C-allocated objects owned by Rust
> to be freed through the C API. It also updates documentation and adds usage
> examples.
>
> Link: https://lore.kernel.org/all/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/
>
>> diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
>> new file mode 100644
>> index 0000000000000..7fe9ec3e55126
>> --- /dev/null
>> +++ b/rust/kernel/owned.rs
> [ ... ]
>> +pub trait Ownable {
>> + /// Tear down this `Ownable`.
>> + ///
>> + /// Implementers of `Ownable` can use this function to clean up the use of `Self`. This can
>> + /// include freeing the underlying object.
>> + ///
>> + /// # Safety
>> + ///
>> + /// Callers must ensure that they have exclusive ownership of the `Self` pointed to by `this`,
>> + /// and that this ownership is transferred to the `release` method. `this` must not be used
>> + /// after calling this method, as the underlying object may have been freed.
>> + unsafe fn release(this: NonNull<Self>);
>
> [Severity: High]
> Since Owned<T> treats T as pinned (exposing Pin<&mut T> via as_pin_mut()),
> should the safety contract here also require that implementers treat `this`
> as pointing to pinned memory?
>
> If an implementer moves the value during cleanup (for example, by reading it
> onto the stack), it could violate the pinning guarantees for !Unpin types and
> cause memory corruption due to self-reference invalidation.
No. `this` is a pointer, and the value cannot be accessed or moved with
safe code. Moving out of `this` requires an unsafe block with proper
safety comments.
>
>> +}
> [ ... ]
>> +impl<T: Ownable> Owned<T> {
>> + /// Creates a new instance of [`Owned`].
>> + ///
>> + /// This function takes over ownership of the underlying object.
>> + ///
>> + /// # Safety
>> + ///
>> + /// Callers must ensure that:
>> + /// - `ptr` points to a valid instance of `T`.
>> + /// - Until `T::release` is called, the returned `Owned<T>` exclusively owns the underlying `T`.
>> + #[inline]
>> + pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
>
> [Severity: High]
> Does this safety contract need to require that the pointer is permanently
> pinned?
>
> Because Owned<T> can expose a pinned mutable reference, callers should be
> aware that they cannot assume the memory remains unpinned after calling this
> function.
No. The documentation clearly state that this function takes ownership
of the underlying object. The caller no longer has authority to access
the object.
>
>> + // INVARIANT: By function safety requirement we satisfy the first invariant of `Self`.
>> + // We treat `T` as pinned from now on.
>> + Self { ptr }
>> + }
>> +
>> + /// Consumes the [`Owned`], returning a raw pointer.
>> + ///
>> + /// This function does not drop the underlying `T`. When this function returns, ownership of the
>> + /// underlying `T` is with the caller.
>> + #[inline]
>> + pub fn into_raw(me: Self) -> NonNull<T> {
>
> [Severity: High]
> Since into_raw() safely strips the Owned wrapper, should there be
> documentation stating that the caller remains bound by the pin invariant
> established by Owned?
>
> Without this, a caller might extract the pointer and safely move the
> previously pinned object, resulting in undefined behavior.
>
No. the return value is a pointer, and the pointee cannot be accessed or
moved with safe code. Moving out of `this` requires an unsafe block with
proper safety comments.
Best regards,
Andreas Hindborg
^ permalink raw reply
* [PATCH v3] rust_binder: reject context manager self-transaction
From: Keshav Verma @ 2026-06-25 10:39 UTC (permalink / raw)
To: Alice Ryhl
Cc: Carlos Llamas, Greg Kroah-Hartman, Arve Hjønnevåg,
Todd Kjos, Christian Brauner, Miguel Ojeda, Boqun Feng, Gary Guo,
linux-kernel, rust-for-linux, Keshav Verma, stable
In-Reply-To: <20260621210134.441-1-iganschel@gmail.com>
Rust binder resolved handle 0 to the context manager node, but it does not
reject the case where the caller owns the same node.
The C binder driver rejects transactions from the context-manager process
to handle 0 after resolving the target node. Match that behavior in Rust
Binder by rejecting handle 0 transactions when the resolved context-manager
node is owned by the calling process.
This applies to both synchronous and oneway transactions because both paths
resolve the target through Process::get_transaction_node().
Cc: stable@kernel.org
Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Signed-off-by: Keshav Verma <iganschel@gmail.com>
---
Changes in v3:
- Keep the check scoped to the Binder Process object, allowing transactions
between different binder fds owned by the same OS process.
Changes in v2:
- Compare the underlying OS process task instead of Rust Binder Process object.
drivers/android/binder/process.rs | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index d09facebddf6..5befff9cf5b9 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -901,7 +901,11 @@ pub(crate) fn insert_or_update_handle(
pub(crate) fn get_transaction_node(&self, handle: u32) -> BinderResult<NodeRef> {
// When handle is zero, try to get the context manager.
if handle == 0 {
- Ok(self.ctx.get_manager_node(true)?)
+ let node_ref = self.ctx.get_manager_node(true)?;
+ if core::ptr::eq(self, &*node_ref.node.owner) {
+ return Err(EINVAL.into());
+ }
+ Ok(node_ref)
} else {
Ok(self.get_node_from_handle(handle, true)?)
}
--
2.39.5
^ permalink raw reply related
* [PATCH v18 5/8] rust: rename `AlwaysRefCounted` to `RefCounted`.
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold, Viresh Kumar, Igor Korotin
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
There are types where it may both be reference counted in some cases and
owned in others. In such cases, obtaining `ARef<T>` from `&T` would be
unsound as it allows creation of `ARef<T>` copy from `&Owned<T>`.
Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef<T>`
would require) and a marker trait to indicate that the type is always
reference counted (and not `Ownable`) so the `&T` -> `ARef<T>` conversion
is possible.
- Rename `AlwaysRefCounted` to `RefCounted`.
- Add a new unsafe trait `AlwaysRefCounted`.
- Implement the new trait `AlwaysRefCounted` for the newly renamed
`RefCounted` implementations. This leaves functionality of existing
implementers of `AlwaysRefCounted` intact.
Suggested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Updated commit message and rebase on rust-next (7.2) ]
Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/auxiliary.rs | 10 +++++++-
rust/kernel/block/mq/request.rs | 19 +++++++++-----
rust/kernel/cred.rs | 16 ++++++++++--
rust/kernel/device.rs | 12 +++++++--
rust/kernel/device/property.rs | 11 ++++++--
rust/kernel/drm/device.rs | 9 +++++--
rust/kernel/drm/gem/mod.rs | 16 +++++++++---
rust/kernel/fs/file.rs | 23 ++++++++++++++---
rust/kernel/i2c.rs | 13 +++++++---
rust/kernel/mm.rs | 22 +++++++++++++---
rust/kernel/mm/mmput_async.rs | 12 +++++++--
rust/kernel/opp.rs | 16 +++++++++---
rust/kernel/owned.rs | 2 +-
rust/kernel/pci.rs | 10 +++++++-
rust/kernel/pid_namespace.rs | 15 +++++++++--
rust/kernel/platform.rs | 10 +++++++-
rust/kernel/pwm.rs | 12 +++++++--
rust/kernel/sync/aref.rs | 57 +++++++++++++++++++++++++----------------
rust/kernel/task.rs | 13 ++++++++--
rust/kernel/types.rs | 12 ++++++---
rust/kernel/usb.rs | 17 +++++++++---
21 files changed, 255 insertions(+), 72 deletions(-)
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index c42928d5a2393..854525289c8b4 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -19,6 +19,10 @@
to_result, //
},
prelude::*,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::{
ForLt,
ForeignOwnable,
@@ -344,7 +348,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -363,6 +367,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index ce3e30c81cb5e..8dad15ae4cfb0 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs
@@ -9,7 +9,11 @@
block::mq::Operations,
error::Result,
sync::{
- aref::{ARef, AlwaysRefCounted},
+ aref::{
+ ARef,
+ AlwaysRefCounted,
+ RefCounted, //
+ },
atomic::Relaxed,
Refcount,
},
@@ -229,11 +233,10 @@ unsafe impl<T: Operations> Send for Request<T> {}
// mutate `self` are internally synchronized`
unsafe impl<T: Operations> Sync for Request<T> {}
-// SAFETY: All instances of `Request<T>` are reference counted. This
-// implementation of `AlwaysRefCounted` ensure that increments to the ref count
-// keeps the object alive in memory at least until a matching reference count
-// decrement is executed.
-unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {
+// SAFETY: All instances of `Request<T>` are reference counted. This implementation of `RefCounted`
+// ensure that increments to the ref count keeps the object alive in memory at least until a
+// matching reference count decrement is executed.
+unsafe impl<T: Operations> RefCounted for Request<T> {
fn inc_ref(&self) {
self.wrapper_ref().refcount().inc();
}
@@ -255,3 +258,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
}
}
}
+
+// SAFETY: We currently do not implement `Ownable`, thus it is okay to obtain an `ARef<Request>`
+// from a `&Request` (but this will change in the future).
+unsafe impl<T: Operations> AlwaysRefCounted for Request<T> {}
diff --git a/rust/kernel/cred.rs b/rust/kernel/cred.rs
index ffa156b9df377..b17736a9adcd5 100644
--- a/rust/kernel/cred.rs
+++ b/rust/kernel/cred.rs
@@ -8,7 +8,15 @@
//!
//! Reference: <https://www.kernel.org/doc/html/latest/security/credentials.html>
-use crate::{bindings, sync::aref::AlwaysRefCounted, task::Kuid, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ task::Kuid,
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
+};
/// Wraps the kernel's `struct cred`.
///
@@ -76,7 +84,7 @@ pub fn euid(&self) -> Kuid {
}
// SAFETY: The type invariants guarantee that `Credential` is always ref-counted.
-unsafe impl AlwaysRefCounted for Credential {
+unsafe impl RefCounted for Credential {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -90,3 +98,7 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Credential>) {
unsafe { bindings::put_cred(obj.cast().as_ptr()) };
}
}
+
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Credential>` from a
+// `&Credential`.
+unsafe impl AlwaysRefCounted for Credential {}
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 645afc49a27d6..2e90f6a06fd05 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -8,8 +8,12 @@
bindings,
fmt,
prelude::*,
- sync::aref::ARef,
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
types::{
+ AlwaysRefCounted,
ForeignOwnable,
Opaque, //
}, //
@@ -448,7 +452,7 @@ pub fn name(&self) -> &CStr {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_raw()) };
@@ -460,6 +464,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
// SAFETY: As by the type invariant `Device` can be sent to any thread.
unsafe impl Send for Device {}
diff --git a/rust/kernel/device/property.rs b/rust/kernel/device/property.rs
index 5aead835fbbc0..cee7e25013689 100644
--- a/rust/kernel/device/property.rs
+++ b/rust/kernel/device/property.rs
@@ -14,7 +14,10 @@
fmt,
prelude::*,
str::{CStr, CString},
- sync::aref::ARef,
+ sync::aref::{
+ ARef,
+ AlwaysRefCounted, //
+ },
types::Opaque,
};
@@ -360,7 +363,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
// SAFETY: Instances of `FwNode` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for FwNode {
+unsafe impl crate::sync::aref::RefCounted for FwNode {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the
// refcount is non-zero.
@@ -374,6 +377,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<FwNode>` from a
+// `&FwNode`.
+unsafe impl AlwaysRefCounted for FwNode {}
+
enum Node<'a> {
Borrowed(&'a FwNode),
Owned(ARef<FwNode>),
diff --git a/rust/kernel/drm/device.rs b/rust/kernel/drm/device.rs
index 403fc35353c74..368742a258376 100644
--- a/rust/kernel/drm/device.rs
+++ b/rust/kernel/drm/device.rs
@@ -15,7 +15,8 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ AlwaysRefCounted,
+ RefCounted, //
},
types::Opaque,
workqueue::{
@@ -227,7 +228,7 @@ fn deref(&self) -> &Self::Target {
// SAFETY: DRM device objects are always reference counted and the get/put functions
// satisfy the requirements.
-unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {
+unsafe impl<T: drm::Driver> RefCounted for Device<T> {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::drm_dev_get(self.as_raw()) };
@@ -242,6 +243,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl<T: drm::Driver> AlwaysRefCounted for Device<T> {}
+
impl<T: drm::Driver> AsRef<device::Device> for Device<T> {
fn as_ref(&self) -> &device::Device {
// SAFETY: `bindings::drm_device::dev` is valid as long as the DRM device itself is valid,
diff --git a/rust/kernel/drm/gem/mod.rs b/rust/kernel/drm/gem/mod.rs
index 01b5bd47a3332..30d3718578fe8 100644
--- a/rust/kernel/drm/gem/mod.rs
+++ b/rust/kernel/drm/gem/mod.rs
@@ -17,7 +17,7 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ RefCounted, //
},
types::Opaque,
};
@@ -29,7 +29,7 @@
#[cfg(CONFIG_RUST_DRM_GEM_SHMEM_HELPER)]
pub mod shmem;
-/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type.
+/// A macro for implementing [`RefCounted`] for any GEM object type.
///
/// Since all GEM objects use the same refcounting scheme.
#[macro_export]
@@ -42,7 +42,7 @@ impl $( <$( $tparam_id:ident ),+> )? for $type:ty
)?
) => {
// SAFETY: All GEM objects are refcounted.
- unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type
+ unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::RefCounted for $type
where
Self: IntoGEMObject,
$( $( $bind_param : $bind_trait ),+ )?
@@ -61,6 +61,14 @@ unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
unsafe { bindings::drm_gem_object_put(obj) };
}
}
+
+ // SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<$type>` from a
+ // `&$type`.
+ unsafe impl $( <$( $tparam_id ),+> )? $crate::sync::aref::AlwaysRefCounted for $type
+ where
+ Self: IntoGEMObject,
+ $( $( $bind_param : $bind_trait ),+ )?
+ {}
};
}
#[cfg_attr(not(CONFIG_RUST_DRM_GEM_SHMEM_HELPER), allow(unused))]
@@ -98,7 +106,7 @@ fn close(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>)
}
/// Trait that represents a GEM object subtype
-pub trait IntoGEMObject: Sized + super::private::Sealed + AlwaysRefCounted {
+pub trait IntoGEMObject: Sized + super::private::Sealed + RefCounted {
/// Returns a reference to the raw `drm_gem_object` structure, which must be valid as long as
/// this owning object is valid.
fn as_raw(&self) -> *mut bindings::drm_gem_object;
diff --git a/rust/kernel/fs/file.rs b/rust/kernel/fs/file.rs
index 23ee689bd2400..720e57418358d 100644
--- a/rust/kernel/fs/file.rs
+++ b/rust/kernel/fs/file.rs
@@ -12,8 +12,15 @@
cred::Credential,
error::{code::*, to_result, Error, Result},
fmt,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque, //
+ }, //
};
use core::ptr;
@@ -197,7 +204,7 @@ unsafe impl Sync for File {}
// SAFETY: The type invariants guarantee that `File` is always ref-counted. This implementation
// makes `ARef<File>` own a normal refcount.
-unsafe impl AlwaysRefCounted for File {
+unsafe impl RefCounted for File {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -212,6 +219,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<File>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<File>` from a
+// `&File`.
+unsafe impl AlwaysRefCounted for File {}
+
/// Wraps the kernel's `struct file`. Not thread safe.
///
/// This type represents a file that is not known to be safe to transfer across thread boundaries.
@@ -233,7 +244,7 @@ pub struct LocalFile {
// SAFETY: The type invariants guarantee that `LocalFile` is always ref-counted. This implementation
// makes `ARef<LocalFile>` own a normal refcount.
-unsafe impl AlwaysRefCounted for LocalFile {
+unsafe impl RefCounted for LocalFile {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -249,6 +260,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<LocalFile>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<LocalFile>` from a
+// `&LocalFile`.
+unsafe impl AlwaysRefCounted for LocalFile {}
+
impl LocalFile {
/// Constructs a new `struct file` wrapper from a file descriptor.
///
diff --git a/rust/kernel/i2c.rs b/rust/kernel/i2c.rs
index 624b971ca8b0b..02b2c9220eb11 100644
--- a/rust/kernel/i2c.rs
+++ b/rust/kernel/i2c.rs
@@ -18,7 +18,8 @@
prelude::*,
sync::aref::{
ARef,
- AlwaysRefCounted, //
+ AlwaysRefCounted,
+ RefCounted, //
},
types::Opaque, //
};
@@ -424,7 +425,7 @@ pub fn get(index: i32) -> Result<ARef<Self>> {
kernel::impl_device_context_into_aref!(I2cAdapter);
// SAFETY: Instances of `I2cAdapter` are always reference-counted.
-unsafe impl AlwaysRefCounted for I2cAdapter {
+unsafe impl RefCounted for I2cAdapter {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::i2c_get_adapter(self.index()) };
@@ -435,6 +436,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::i2c_put_adapter(obj.as_ref().as_raw()) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cAdapter`.
+unsafe impl AlwaysRefCounted for I2cAdapter {}
/// The i2c board info representation
///
@@ -500,7 +504,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for I2cClient<C
kernel::impl_device_context_into_aref!(I2cClient);
// SAFETY: Instances of `I2cClient` are always reference-counted.
-unsafe impl AlwaysRefCounted for I2cClient {
+unsafe impl RefCounted for I2cClient {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -511,6 +515,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
unsafe { bindings::put_device(&raw mut (*obj.as_ref().as_raw()).dev) }
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from an
+// `&I2cClient`.
+unsafe impl AlwaysRefCounted for I2cClient {}
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for I2cClient<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
diff --git a/rust/kernel/mm.rs b/rust/kernel/mm.rs
index 4764d7b68f2a7..83ed94fca14ca 100644
--- a/rust/kernel/mm.rs
+++ b/rust/kernel/mm.rs
@@ -13,8 +13,15 @@
use crate::{
bindings,
- sync::aref::{ARef, AlwaysRefCounted},
- types::{NotThreadSafe, Opaque},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque, //
+ }, //
};
use core::{ops::Deref, ptr::NonNull};
@@ -55,7 +62,7 @@ unsafe impl Send for Mm {}
unsafe impl Sync for Mm {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for Mm {
+unsafe impl RefCounted for Mm {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -69,6 +76,9 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Mm>` from a `&Mm`.
+unsafe impl AlwaysRefCounted for Mm {}
+
/// A wrapper for the kernel's `struct mm_struct`.
///
/// This type is like [`Mm`], but with non-zero `mm_users`. It can only be used when `mm_users` can
@@ -91,7 +101,7 @@ unsafe impl Send for MmWithUser {}
unsafe impl Sync for MmWithUser {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUser {
+unsafe impl RefCounted for MmWithUser {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -105,6 +115,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUser>` from a
+// `&MmWithUser`.
+unsafe impl AlwaysRefCounted for MmWithUser {}
+
// Make all `Mm` methods available on `MmWithUser`.
impl Deref for MmWithUser {
type Target = Mm;
diff --git a/rust/kernel/mm/mmput_async.rs b/rust/kernel/mm/mmput_async.rs
index b8d2f051225c7..8fbc396e46028 100644
--- a/rust/kernel/mm/mmput_async.rs
+++ b/rust/kernel/mm/mmput_async.rs
@@ -10,7 +10,11 @@
use crate::{
bindings,
mm::MmWithUser,
- sync::aref::{ARef, AlwaysRefCounted},
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::AlwaysRefCounted,
};
use core::{ops::Deref, ptr::NonNull};
@@ -34,7 +38,7 @@ unsafe impl Send for MmWithUserAsync {}
unsafe impl Sync for MmWithUserAsync {}
// SAFETY: By the type invariants, this type is always refcounted.
-unsafe impl AlwaysRefCounted for MmWithUserAsync {
+unsafe impl RefCounted for MmWithUserAsync {
#[inline]
fn inc_ref(&self) {
// SAFETY: The pointer is valid since self is a reference.
@@ -48,6 +52,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<MmWithUserAsync>`
+// from a `&MmWithUserAsync`.
+unsafe impl AlwaysRefCounted for MmWithUserAsync {}
+
// Make all `MmWithUser` methods available on `MmWithUserAsync`.
impl Deref for MmWithUserAsync {
type Target = MmWithUser;
diff --git a/rust/kernel/opp.rs b/rust/kernel/opp.rs
index 62e44676125d1..b8db6bdefd077 100644
--- a/rust/kernel/opp.rs
+++ b/rust/kernel/opp.rs
@@ -16,8 +16,14 @@
ffi::{c_char, c_ulong},
prelude::*,
str::CString,
- sync::aref::{ARef, AlwaysRefCounted},
- types::Opaque,
+ sync::aref::{
+ ARef,
+ RefCounted, //
+ },
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
};
#[cfg(CONFIG_CPU_FREQ)]
@@ -1041,7 +1047,7 @@ unsafe impl Send for OPP {}
unsafe impl Sync for OPP {}
/// SAFETY: The type invariants guarantee that [`OPP`] is always refcounted.
-unsafe impl AlwaysRefCounted for OPP {
+unsafe impl RefCounted for OPP {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -1055,6 +1061,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<OPP>` from an
+// `&OPP`.
+unsafe impl AlwaysRefCounted for OPP {}
+
impl OPP {
/// Creates an owned reference to a [`OPP`] from a valid pointer.
///
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index 9c92d4a83cc1b..e79936c00002c 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -27,7 +27,7 @@
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`AlwaysRefCounted`](crate::sync::aref::AlwaysRefCounted) should be implemented.
+/// [`RefCounted`](crate::types::RefCounted) should be implemented.
///
/// # Examples
///
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 5071cae6543fd..ea9ef99cecb07 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -19,6 +19,10 @@
},
prelude::*,
str::CStr,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -481,7 +485,7 @@ unsafe impl<Ctx: device::DeviceContext> device::AsBusDevice<Ctx> for Device<Ctx>
impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::pci_dev_get(self.as_raw()) };
@@ -493,6 +497,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/pid_namespace.rs b/rust/kernel/pid_namespace.rs
index 979a9718f153d..067f68b99e8c5 100644
--- a/rust/kernel/pid_namespace.rs
+++ b/rust/kernel/pid_namespace.rs
@@ -7,7 +7,14 @@
//! C header: [`include/linux/pid_namespace.h`](srctree/include/linux/pid_namespace.h) and
//! [`include/linux/pid.h`](srctree/include/linux/pid.h)
-use crate::{bindings, sync::aref::AlwaysRefCounted, types::Opaque};
+use crate::{
+ bindings,
+ sync::aref::RefCounted,
+ types::{
+ AlwaysRefCounted,
+ Opaque, //
+ }, //
+};
use core::ptr;
/// Wraps the kernel's `struct pid_namespace`. Thread safe.
@@ -41,7 +48,7 @@ pub unsafe fn from_ptr<'a>(ptr: *const bindings::pid_namespace) -> &'a Self {
}
// SAFETY: Instances of `PidNamespace` are always reference-counted.
-unsafe impl AlwaysRefCounted for PidNamespace {
+unsafe impl RefCounted for PidNamespace {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -55,6 +62,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<PidNamespace>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<PidNamespace>` from
+// a `&PidNamespace`.
+unsafe impl AlwaysRefCounted for PidNamespace {}
+
// SAFETY:
// - `PidNamespace::dec_ref` can be called from any thread.
// - It is okay to send ownership of `PidNamespace` across thread boundaries.
diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs
index 9b362e0495d32..0ba676445b06d 100644
--- a/rust/kernel/platform.rs
+++ b/rust/kernel/platform.rs
@@ -27,6 +27,10 @@
},
of,
prelude::*,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -518,7 +522,7 @@ pub fn optional_irq_by_name(&self, name: &CStr) -> Result<IrqRequest<'_>> {
impl<'a> crate::dma::Device<'a> for Device<device::Core<'a>> {}
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
unsafe { bindings::get_device(self.as_ref().as_raw()) };
@@ -530,6 +534,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
diff --git a/rust/kernel/pwm.rs b/rust/kernel/pwm.rs
index 6c9d667009ef7..2d1cd74dd98e1 100644
--- a/rust/kernel/pwm.rs
+++ b/rust/kernel/pwm.rs
@@ -13,7 +13,11 @@
devres,
error::{self, to_result},
prelude::*,
- sync::aref::{ARef, AlwaysRefCounted},
+ sync::aref::{
+ ARef,
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque, //
};
use core::{
@@ -629,7 +633,7 @@ pub fn new<'a>(
}
// SAFETY: Implements refcounting for `Chip` using the embedded `struct device`.
-unsafe impl<T: PwmOps> AlwaysRefCounted for Chip<T> {
+unsafe impl<T: PwmOps> RefCounted for Chip<T> {
#[inline]
fn inc_ref(&self) {
// SAFETY: `self.0.get()` points to a valid `pwm_chip` because `self` exists.
@@ -647,6 +651,10 @@ unsafe fn dec_ref(obj: NonNull<Chip<T>>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Chip<T>>` from a
+// `&Chip<T>`.
+unsafe impl<T: PwmOps> AlwaysRefCounted for Chip<T> {}
+
// SAFETY: `Chip` is a wrapper around `*mut bindings::pwm_chip`. The underlying C
// structure's state is managed and synchronized by the kernel's device model
// and PWM core locking mechanisms. Therefore, it is safe to move the `Chip`
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index 3bd5eb8a1a526..fb7466a362741 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -24,11 +24,9 @@
ptr::NonNull, //
};
-/// Types that are _always_ reference counted.
+/// Types that are internally reference counted.
///
/// It allows such types to define their own custom ref increment and decrement functions.
-/// Additionally, it allows users to convert from a shared reference `&T` to an owned reference
-/// [`ARef<T>`].
///
/// This is usually implemented by wrappers to existing structures on the C side of the code. For
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
@@ -45,9 +43,8 @@
/// at least until matching decrements are performed.
///
/// Implementers must also ensure that all instances are reference-counted. (Otherwise they
-/// won't be able to honour the requirement that [`AlwaysRefCounted::inc_ref`] keep the object
-/// alive.)
-pub unsafe trait AlwaysRefCounted {
+/// won't be able to honour the requirement that [`RefCounted::inc_ref`] keep the object alive.)
+pub unsafe trait RefCounted {
/// Increments the reference count on the object.
fn inc_ref(&self);
@@ -60,11 +57,27 @@ pub unsafe trait AlwaysRefCounted {
/// Callers must ensure that there was a previous matching increment to the reference count,
/// and that the object is no longer used after its reference count is decremented (as it may
/// result in the object being freed), unless the caller owns another increment on the refcount
- /// (e.g., it calls [`AlwaysRefCounted::inc_ref`] twice, then calls
- /// [`AlwaysRefCounted::dec_ref`] once).
+ /// (e.g., it calls [`RefCounted::inc_ref`] twice, then calls [`RefCounted::dec_ref`] once).
unsafe fn dec_ref(obj: NonNull<Self>);
}
+/// Always reference-counted type.
+///
+/// It allows deriving a counted reference [`ARef<T>`] from a `&T`.
+///
+/// This provides some convenience, but it allows "escaping" borrow checks on `&T`. As it
+/// complicates attempts to ensure that a reference to T is unique, it is optional to provide for
+/// [`RefCounted`] types. See *Safety* below.
+///
+/// # Safety
+///
+/// Implementers must ensure that no safety invariants are violated by upgrading an `&T` to an
+/// [`ARef<T>`]. In particular that implies [`AlwaysRefCounted`] and [`crate::types::Ownable`]
+/// cannot be implemented for the same type, as this would allow violating the uniqueness guarantee
+/// of [`crate::types::Owned<T>`] by dereferencing it into an `&T` and obtaining an [`ARef`] from
+/// that.
+pub unsafe trait AlwaysRefCounted: RefCounted {}
+
/// An owned reference to an always-reference-counted object.
///
/// The object's reference count is automatically decremented when an instance of [`ARef`] is
@@ -75,7 +88,7 @@ pub unsafe trait AlwaysRefCounted {
///
/// The pointer stored in `ptr` is non-null and valid for the lifetime of the [`ARef`] instance. In
/// particular, the [`ARef`] instance owns an increment on the underlying object's reference count.
-pub struct ARef<T: AlwaysRefCounted> {
+pub struct ARef<T: RefCounted> {
ptr: NonNull<T>,
_p: PhantomData<T>,
}
@@ -84,19 +97,19 @@ pub struct ARef<T: AlwaysRefCounted> {
// it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
// `T` to be `Send` because any thread that has an `ARef<T>` may ultimately access `T` using a
// mutable reference, for example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Send for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Send for ARef<T> {}
// SAFETY: It is safe to send `&ARef<T>` to another thread when the underlying `T` is `Sync`
// because it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally,
// it needs `T` to be `Send` because any thread that has a `&ARef<T>` may clone it and get an
// `ARef<T>` on that thread, so the thread may ultimately access `T` using a mutable reference, for
// example, when the reference count reaches zero and `T` is dropped.
-unsafe impl<T: AlwaysRefCounted + Sync + Send> Sync for ARef<T> {}
+unsafe impl<T: RefCounted + Sync + Send> Sync for ARef<T> {}
// Even if `T` is pinned, pointers to `T` can still move.
-impl<T: AlwaysRefCounted> Unpin for ARef<T> {}
+impl<T: RefCounted> Unpin for ARef<T> {}
-impl<T: AlwaysRefCounted> ARef<T> {
+impl<T: RefCounted> ARef<T> {
/// Creates a new instance of [`ARef`].
///
/// It takes over an increment of the reference count on the underlying object.
@@ -125,12 +138,12 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// ```
/// use core::ptr::NonNull;
- /// use kernel::sync::aref::{ARef, AlwaysRefCounted};
+ /// use kernel::sync::aref::{ARef, RefCounted};
///
/// struct Empty {}
///
/// # // SAFETY: TODO.
- /// unsafe impl AlwaysRefCounted for Empty {
+ /// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
/// }
@@ -148,7 +161,7 @@ pub fn into_raw(me: Self) -> NonNull<T> {
}
}
-impl<T: AlwaysRefCounted> Clone for ARef<T> {
+impl<T: RefCounted> Clone for ARef<T> {
fn clone(&self) -> Self {
self.inc_ref();
// SAFETY: We just incremented the refcount above.
@@ -156,7 +169,7 @@ fn clone(&self) -> Self {
}
}
-impl<T: AlwaysRefCounted> Deref for ARef<T> {
+impl<T: RefCounted> Deref for ARef<T> {
type Target = T;
fn deref(&self) -> &Self::Target {
@@ -173,7 +186,7 @@ fn from(b: &T) -> Self {
}
}
-impl<T: AlwaysRefCounted> Drop for ARef<T> {
+impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
// decrement.
@@ -183,19 +196,19 @@ fn drop(&mut self) {
impl<T, U> PartialEq<ARef<U>> for ARef<T>
where
- T: AlwaysRefCounted + PartialEq<U>,
- U: AlwaysRefCounted,
+ T: RefCounted + PartialEq<U>,
+ U: RefCounted,
{
#[inline]
fn eq(&self, other: &ARef<U>) -> bool {
T::eq(&**self, &**other)
}
}
-impl<T: AlwaysRefCounted + Eq> Eq for ARef<T> {}
+impl<T: RefCounted + Eq> Eq for ARef<T> {}
impl<T, U> PartialEq<&'_ U> for ARef<T>
where
- T: AlwaysRefCounted + PartialEq<U>,
+ T: RefCounted + PartialEq<U>,
{
#[inline]
fn eq(&self, other: &&U) -> bool {
diff --git a/rust/kernel/task.rs b/rust/kernel/task.rs
index 38273f4eedb51..6259430b0ca31 100644
--- a/rust/kernel/task.rs
+++ b/rust/kernel/task.rs
@@ -10,7 +10,12 @@
pid_namespace::PidNamespace,
prelude::*,
sync::aref::ARef,
- types::{NotThreadSafe, Opaque},
+ types::{
+ AlwaysRefCounted,
+ NotThreadSafe,
+ Opaque,
+ RefCounted, //
+ },
};
use core::{
ops::Deref,
@@ -347,7 +352,7 @@ pub fn group_leader(&self) -> &Task {
}
// SAFETY: The type invariants guarantee that `Task` is always refcounted.
-unsafe impl crate::sync::aref::AlwaysRefCounted for Task {
+unsafe impl RefCounted for Task {
#[inline]
fn inc_ref(&self) {
// SAFETY: The existence of a shared reference means that the refcount is nonzero.
@@ -361,6 +366,10 @@ unsafe fn dec_ref(obj: ptr::NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Task>` from a
+// `&Task`.
+unsafe impl AlwaysRefCounted for Task {}
+
impl PartialEq for Task {
#[inline]
fn eq(&self, other: &Self) -> bool {
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index c41eab0ec983c..5ef763717e59a 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -15,9 +15,15 @@
pub mod for_lt;
pub use for_lt::ForLt;
-pub use crate::owned::{
- Ownable,
- Owned, //
+pub use crate::{
+ owned::{
+ Ownable,
+ Owned, //
+ },
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ }, //
};
/// Used to transfer ownership to and from foreign (non-Rust) languages.
diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 7aff0c82d0afc..59350c6b0df2a 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -18,7 +18,10 @@
to_result, //
},
prelude::*,
- sync::aref::AlwaysRefCounted,
+ sync::aref::{
+ AlwaysRefCounted,
+ RefCounted, //
+ },
types::Opaque,
ThisModule, //
};
@@ -392,7 +395,7 @@ fn as_ref(&self) -> &Device {
}
// SAFETY: Instances of `Interface` are always reference-counted.
-unsafe impl AlwaysRefCounted for Interface {
+unsafe impl RefCounted for Interface {
fn inc_ref(&self) {
// SAFETY: The invariants of `Interface` guarantee that `self.as_raw()`
// returns a valid `struct usb_interface` pointer, for which we will
@@ -406,6 +409,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Interface>` from a
+// `&Interface`.
+unsafe impl AlwaysRefCounted for Interface {}
+
// SAFETY: A `Interface` is always reference-counted and can be released from any thread.
unsafe impl Send for Interface {}
@@ -443,7 +450,7 @@ fn as_raw(&self) -> *mut bindings::usb_device {
kernel::impl_device_context_into_aref!(Device);
// SAFETY: Instances of `Device` are always reference-counted.
-unsafe impl AlwaysRefCounted for Device {
+unsafe impl RefCounted for Device {
fn inc_ref(&self) {
// SAFETY: The invariants of `Device` guarantee that `self.as_raw()`
// returns a valid `struct usb_device` pointer, for which we will
@@ -457,6 +464,10 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
}
}
+// SAFETY: We do not implement `Ownable`, thus it is okay to obtain an `ARef<Device>` from a
+// `&Device`.
+unsafe impl AlwaysRefCounted for Device {}
+
impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
fn as_ref(&self) -> &device::Device<Ctx> {
// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
--
2.51.2
^ permalink raw reply related
* [PATCH v18 1/8] rust: alloc: add `KBox::into_non_null`
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
Add a method to consume a `Box<T, A>` and return a `NonNull<T>`. This
is a convenience wrapper around `Self::into_raw` for callers that need
a `NonNull` pointer rather than a raw pointer.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
---
rust/kernel/alloc/kbox.rs | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs
index 35d1e015848dd..d534e8adcf7b3 100644
--- a/rust/kernel/alloc/kbox.rs
+++ b/rust/kernel/alloc/kbox.rs
@@ -211,6 +211,15 @@ pub fn leak<'a>(b: Self) -> &'a mut T {
// which points to an initialized instance of `T`.
unsafe { &mut *Box::into_raw(b) }
}
+
+ /// Consumes the `Box<T,A>` and returns a `NonNull<T>`.
+ ///
+ /// Like [`Self::into_raw`], but returns a `NonNull`.
+ #[inline]
+ pub fn into_non_null(b: Self) -> NonNull<T> {
+ // SAFETY: `KBox::into_raw` returns a valid pointer.
+ unsafe { NonNull::new_unchecked(Self::into_raw(b)) }
+ }
}
impl<T, A> Box<MaybeUninit<T>, A>
--
2.51.2
^ permalink raw reply related
* [PATCH v18 3/8] rust: implement `ForeignOwnable` for `Owned`
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
Implement `ForeignOwnable` for `Owned<T>`. This allows use of `Owned<T>` in
places such as the `XArray`.
Note that `T` does not need to implement `ForeignOwnable` for `Owned<T>` to
implement `ForeignOwnable`.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index 7fe9ec3e55126..9c92d4a83cc1b 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -15,6 +15,8 @@
ptr::NonNull, //
};
+use kernel::types::ForeignOwnable;
+
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
/// is implemented on types from the C side.
///
@@ -186,3 +188,54 @@ fn drop(&mut self) {
unsafe { T::release(self.ptr) };
}
}
+
+// SAFETY: We derive the pointer to `T` from a valid `T`, so the returned
+// pointer satisfy alignment requirements of `T`.
+unsafe impl<T: Ownable> ForeignOwnable for Owned<T> {
+ const FOREIGN_ALIGN: usize = core::mem::align_of::<T>();
+
+ type Borrowed<'a>
+ = &'a T
+ where
+ Self: 'a;
+ type BorrowedMut<'a>
+ = Pin<&'a mut T>
+ where
+ Self: 'a;
+
+ #[inline]
+ fn into_foreign(self) -> *mut kernel::ffi::c_void {
+ let ptr = self.ptr.as_ptr().cast();
+ core::mem::forget(self);
+ ptr
+ }
+
+ #[inline]
+ unsafe fn from_foreign(ptr: *mut kernel::ffi::c_void) -> Self {
+ // INVARIANT: By the function safety contract, `ptr` was returned by `into_foreign`, which
+ // gave up exclusive ownership of a valid, pinned `T`; we retake that ownership here.
+ Self {
+ // SAFETY: By function safety contract, `ptr` came from
+ // `into_foreign` and cannot be null.
+ ptr: unsafe { NonNull::new_unchecked(ptr.cast()) },
+ }
+ }
+
+ #[inline]
+ unsafe fn borrow<'a>(ptr: *mut kernel::ffi::c_void) -> Self::Borrowed<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // reference for `'a`.
+ unsafe { &*ptr.cast() }
+ }
+
+ #[inline]
+ unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a> {
+ // SAFETY: By function safety requirements, `ptr` is valid for use as a
+ // unique reference for `'a`.
+ let inner = unsafe { &mut *ptr.cast() };
+
+ // SAFETY: We never move out of inner, and we do not hand out mutable
+ // references when `T: !Unpin`.
+ unsafe { Pin::new_unchecked(inner) }
+ }
+}
--
2.51.2
^ permalink raw reply related
* [PATCH v18 0/8] rust: add `Ownable` trait and `Owned` type
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Asahi Lina, Oliver Mangold, Viresh Kumar, Boqun Feng, Asahi Lina,
Igor Korotin, Andreas Hindborg
Add a new trait `Ownable` and type `Owned` for types that specify their
own way of performing allocation and destruction. This is useful for
types from the C side.
Implement `ForeignOwnable` for `Owned`.
Convert `Page` to be `Ownable` and add a `from_raw` method.
Add the trait `OwnableRefCounted` that allows conversion between
`ARef` and `Owned`. This is analogous to conversion between `Arc` and
`UniqueArc`.
Patches 1-4 implement `Ownable` and applies it to `Page`. These patches
can be merged on their own.
Patches 5-7 add `Ownable` -> `ARef` interop and can be merged later if
consensus on their shape cannot be reached.
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
Changes in v18:
- Rebase on `rust-next` (2026-06-24).
- Drop the `'static` bound on `ForeignOwnable for Owned` (Gary).
- Make `Ownable::release` take a raw pointer instead of `&mut self` (Alice, Sashiko).
- Drop `types::ARef` re-export (Alice).
- Drop unneeded `#[repr(transparent)]` on `Owned` (Gary).
- Fix `FOREIGN_ALIGN` for `Owned` to report the pointee alignment (Sashiko).
- Remove `BorrowedPage`; use `&Page` directly (Alice).
- Update Rust Binder for the `Owned<Page>` conversion (Alice).
- Update `pwm.rs` for the `RefCounted`/`AlwaysRefCounted` split (Sashiko).
- Fix documentation nits: missing `// INVARIANT:` comments, stale `Page` docs, and a stray `mut` (Sashiko).
- Expand the `use` statements touched by the rename patch to the multi-line style (Onur).
- Link to v17: https://msgid.link/20260604-unique-ref-v17-0-7b4c3d2930b9@kernel.org
Changes in v17:
- Rebase on v7.1-rc2.
- Reorder patches so that `Ownable` can merge without `OwnableRefCounted` (Alice).
- Add `#[inline]` directives to short functions added by the series (Gary).
- Link to v16: https://msgid.link/20260224-unique-ref-v16-0-c21afcb118d3@kernel.org
Changes in v16:
- Simplify pointer to reference cast in `Page::from_raw`.
- Use `NonNull<Page>` rather than `Owned<Page>` for `BorrowedPage` internals.
- Use "convertible to reference" wording when converting pointers to references.
- Fix formatting for `Page::from_raw` docs.
- Leave imports alone when adding safety comment to aref example.
- Use `KBox::into_nonnull` for examples.
- Add patch for `KBox::into_nonnull`.
- Change invariants and safety comments of `Ownable` and make the trait safe.
- Make `Ownable::release` take a mutable reference.
- Fix error handling in example for `Ownable`
- Link to v15: https://msgid.link/20260220-unique-ref-v15-0-893ed86b06cc@kernel.org
Changes in v15:
- Update series with original SoB's.
- Rename `AlwaysRefCounted` in `kernel::usb`.
- Rename `Owned::get_pin_mut` to `Owned::as_pin_mut`.
- Link to v14: https://msgid.link/20260204-unique-ref-v14-0-17cb29ebacbb@kernel.org
Changes in v14:
- Rebase on v6.19-rc7.
- Rewrite cover letter.
- Update documentation and safety comments based on v13 feedback.
- Update commit messages.
- Reorder implementation blocks in owned.rs.
- Update example in owned.rs to use try operator rather than `expect`.
- Reformat use statements.
- Add patch: rust: page: convert to `Ownable`.
- Add patch: rust: implement `ForeignOwnable` for `Owned`.
- Add patch: rust: page: add `from_raw()`.
- Link to v13: https://lore.kernel.org/r/20251117-unique-ref-v13-0-b5b243df1250@pm.me
Changes in v13:
- Rebase onto v6.18-rc1 (Andreas's work).
- Documentation and style fixes contributed by Andreas
- Link to v12: https://lore.kernel.org/r/20251001-unique-ref-v12-0-fa5c31f0c0c4@pm.me
Changes in v12:
-
- Rebase onto v6.17-rc1 (Andreas's work).
- moved kernel/types/ownable.rs to kernel/owned.rs
- Drop OwnableMut, make DerefMut depend on Unpin instead. I understood
ML discussion as that being okay, but probably needs further scrunity.
- Lots of more documentation changes suggested by reviewers.
- Usage example for Ownable/Owned.
- Link to v11: https://lore.kernel.org/r/20250618-unique-ref-v11-0-49eadcdc0aa6@pm.me
Changes in v11:
- Rework of documentation. I tried to honor all requests for changes "in
spirit" plus some clearifications and corrections of my own.
- Dropping `SimpleOwnedRefCounted` by request from Alice, as it creates a
potentially problematic blanket implementation (which a derive macro that
could be created later would not have).
- Dropping Miguel's "kbuild: provide `RUSTC_HAS_DO_NOT_RECOMMEND` symbol"
patch, as it is not needed anymore after dropping `SimpleOwnedRefCounted`.
(I can add it again, if it is considered useful anyway).
- Link to v10: https://lore.kernel.org/r/20250502-unique-ref-v10-0-25de64c0307f@pm.me
Changes in v10:
- Moved kernel/ownable.rs to kernel/types/ownable.rs
- Fixes in documentation / comments as suggested by Andreas Hindborg
- Added Reviewed-by comment for Andreas Hindborg
- Fix rustfmt of pid_namespace.rs
- Link to v9: https://lore.kernel.org/r/20250325-unique-ref-v9-0-e91618c1de26@pm.me
Changes in v9:
- Rebase onto v6.14-rc7
- Move Ownable/OwnedRefCounted/Ownable, etc., into separate module
- Documentation fixes to Ownable/OwnableMut/OwnableRefCounted
- Add missing SAFETY documentation to ARef example
- Link to v8: https://lore.kernel.org/r/20250313-unique-ref-v8-0-3082ffc67a31@pm.me
Changes in v8:
- Fix Co-developed-by and Suggested-by tags as suggested by Miguel and Boqun
- Some small documentation fixes in Owned/Ownable patch
- removing redundant trait constraint on DerefMut for Owned as suggested by Boqun Feng
- make SimpleOwnedRefCounted no longer implement RefCounted as suggested by Boqun Feng
- documentation for RefCounted as suggested by Boqun Feng
- Link to v7: https://lore.kernel.org/r/20250310-unique-ref-v7-0-4caddb78aa05@pm.me
Changes in v7:
- Squash patch to make Owned::from_raw/into_raw public into parent
- Added Signed-off-by to other people's commits
- Link to v6: https://lore.kernel.org/r/20250310-unique-ref-v6-0-1ff53558617e@pm.me
Changes in v6:
- Changed comments/formatting as suggested by Miguel Ojeda
- Included and used new config flag RUSTC_HAS_DO_NOT_RECOMMEND,
thus no changes to types.rs will be needed when the attribute
becomes available.
- Fixed commit message for Owned patch.
- Link to v5: https://lore.kernel.org/r/20250307-unique-ref-v5-0-bffeb633277e@pm.me
Changes in v5:
- Rebase the whole thing on top of the Ownable/Owned traits by Asahi Lina.
- Rename AlwaysRefCounted to RefCounted and make AlwaysRefCounted a
marker trait instead to allow to obtain an ARef<T> from an &T,
which (as Alice pointed out) is unsound when combined with UniqueRef/Owned.
- Change the Trait design and naming to implement this feature,
UniqueRef/UniqueRefCounted is dropped in favor of Ownable/Owned and
OwnableRefCounted is used to provide the functions to convert
between Owned and ARef.
- Link to v4: https://lore.kernel.org/r/20250305-unique-ref-v4-1-a8fdef7b1c2c@pm.me
Changes in v4:
- Just a minor change in naming by request from Andreas Hindborg,
try_shared_to_unique() -> try_from_shared(),
unique_to_shared() -> into_shared(),
which is more in line with standard Rust naming conventions.
- Link to v3: https://lore.kernel.org/r/Z8Wuud2UQX6Yukyr@mango
To: Danilo Krummrich <dakr@kernel.org>
To: Lorenzo Stoakes <ljs@kernel.org>
To: Vlastimil Babka <vbabka@kernel.org>
To: "Liam R. Howlett" <liam@infradead.org>
To: Uladzislau Rezki <urezki@gmail.com>
To: Miguel Ojeda <ojeda@kernel.org>
To: Boqun Feng <boqun@kernel.org>
To: Gary Guo <gary@garyguo.net>
To: Björn Roy Baron <bjorn3_gh@protonmail.com>
To: Benno Lossin <lossin@kernel.org>
To: Andreas Hindborg <a.hindborg@kernel.org>
To: Alice Ryhl <aliceryhl@google.com>
To: Trevor Gross <tmgross@umich.edu>
To: Daniel Almeida <daniel.almeida@collabora.com>
To: Tamir Duberstein <tamird@kernel.org>
To: Alexandre Courbot <acourbot@nvidia.com>
To: Onur Özkan <work@onurozkan.dev>
To: Lyude Paul <lyude@redhat.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Arve Hjønnevåg <arve@android.com>
To: Todd Kjos <tkjos@android.com>
To: Christian Brauner <brauner@kernel.org>
To: Carlos Llamas <cmllamas@google.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
To: Dave Ertman <david.m.ertman@intel.com>
To: Ira Weiny <ira.weiny@intel.com>
To: Leon Romanovsky <leon@kernel.org>
To: Paul Moore <paul@paul-moore.com>
To: Serge Hallyn <sergeh@kernel.org>
To: David Airlie <airlied@gmail.com>
To: Simona Vetter <simona@ffwll.ch>
To: Alexander Viro <viro@zeniv.linux.org.uk>
To: Jan Kara <jack@suse.cz>
To: Igor Korotin <igor.korotin@linux.dev>
To: Viresh Kumar <vireshk@kernel.org>
To: Nishanth Menon <nm@ti.com>
To: Stephen Boyd <sboyd@kernel.org>
To: Bjorn Helgaas <bhelgaas@google.com>
To: Krzysztof Wilczyński <kwilczynski@kernel.org>
To: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
To: Michal Wilczynski <m.wilczynski@samsung.com>
Cc: Philipp Stanner <phasta@kernel.org>
Cc: rust-for-linux@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: driver-core@lists.linux.dev
Cc: linux-block@vger.kernel.org
Cc: linux-security-module@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-pm@vger.kernel.org
Cc: linux-pci@vger.kernel.org
Cc: linux-pwm@vger.kernel.org
---
Andreas Hindborg (3):
rust: alloc: add `KBox::into_non_null`
rust: implement `ForeignOwnable` for `Owned`
rust: page: add `from_raw()`
Asahi Lina (2):
rust: types: Add Ownable/Owned types
rust: page: convert to `Ownable`
Oliver Mangold (3):
rust: rename `AlwaysRefCounted` to `RefCounted`.
rust: Add missing SAFETY documentation for `ARef` example
rust: Add `OwnableRefCounted`
drivers/android/binder/page_range.rs | 10 +-
rust/kernel/alloc/allocator.rs | 19 +-
rust/kernel/alloc/allocator/iter.rs | 6 +-
rust/kernel/alloc/kbox.rs | 9 +
rust/kernel/auxiliary.rs | 10 +-
rust/kernel/block/mq/request.rs | 19 +-
rust/kernel/cred.rs | 16 +-
rust/kernel/device.rs | 12 +-
rust/kernel/device/property.rs | 11 +-
rust/kernel/drm/device.rs | 9 +-
rust/kernel/drm/gem/mod.rs | 16 +-
rust/kernel/fs/file.rs | 23 ++-
rust/kernel/i2c.rs | 13 +-
rust/kernel/lib.rs | 1 +
rust/kernel/mm.rs | 22 ++-
rust/kernel/mm/mmput_async.rs | 12 +-
rust/kernel/opp.rs | 16 +-
rust/kernel/owned.rs | 371 +++++++++++++++++++++++++++++++++++
rust/kernel/page.rs | 136 +++++--------
rust/kernel/pci.rs | 10 +-
rust/kernel/pid_namespace.rs | 15 +-
rust/kernel/platform.rs | 10 +-
rust/kernel/pwm.rs | 12 +-
rust/kernel/sync/aref.rs | 82 +++++---
rust/kernel/task.rs | 13 +-
rust/kernel/types.rs | 12 ++
rust/kernel/usb.rs | 17 +-
27 files changed, 721 insertions(+), 181 deletions(-)
---
base-commit: 43a393185e33e573a374c1d4f7ddf6481484ef8d
change-id: 20250305-unique-ref-29fcd675f9e9
Best regards,
--
Andreas Hindborg <a.hindborg@kernel.org>
^ permalink raw reply
* [PATCH v18 6/8] rust: Add missing SAFETY documentation for `ARef` example
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
SAFETY comment in rustdoc example was just 'TODO'. Fixed.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/sync/aref.rs | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index fb7466a362741..d0865aeb9371b 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -142,7 +142,9 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// struct Empty {}
///
- /// # // SAFETY: TODO.
+ /// // SAFETY: The `RefCounted` implementation for `Empty` does not count references and never
+ /// // frees the underlying object. Thus we can act as owning an increment on the refcount for
+ /// // the object that we pass to the newly created `ARef`.
/// unsafe impl RefCounted for Empty {
/// fn inc_ref(&self) {}
/// unsafe fn dec_ref(_obj: NonNull<Self>) {}
@@ -150,7 +152,7 @@ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
///
/// let mut data = Empty {};
/// let ptr = NonNull::<Empty>::new(&mut data).unwrap();
- /// # // SAFETY: TODO.
+ /// // SAFETY: We keep `data` around longer than the `ARef`.
/// let data_ref: ARef<Empty> = unsafe { ARef::from_raw(ptr) };
/// let raw_ptr: NonNull<Empty> = ARef::into_raw(data_ref);
///
--
2.51.2
^ permalink raw reply related
* [PATCH v18 2/8] rust: types: Add Ownable/Owned types
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Asahi Lina, Oliver Mangold, Boqun Feng
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Asahi Lina <lina+kernel@asahilina.net>
By analogy to `AlwaysRefCounted` and `ARef`, an `Ownable` type is a
(typically C FFI) type that *may* be owned by Rust, but need not be. Unlike
`AlwaysRefCounted`, this mechanism expects the reference to be unique
within Rust, and does not allow cloning.
Conceptually, this is similar to a `KBox<T>`, except that it delegates
resource management to the `T` instead of using a generic allocator.
[ om:
- Split code into separate file and `pub use` it from types.rs.
- Make from_raw() and into_raw() public.
- Remove OwnableMut, and make DerefMut dependent on Unpin instead.
- Usage example/doctest for Ownable/Owned.
- Fixes to documentation and commit message.
]
Link: https://lore.kernel.org/all/20250202-rust-page-v1-1-e3170d7fe55e@asahilina.net/
Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Co-developed-by: Oliver Mangold <oliver.mangold@pm.me>
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
[ Andreas: Updated documentation, examples, and formatting. Change safety
requirements, safety comments. ]
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/lib.rs | 1 +
rust/kernel/owned.rs | 188 +++++++++++++++++++++++++++++++++++++++++++++++
rust/kernel/sync/aref.rs | 5 ++
rust/kernel/types.rs | 5 ++
4 files changed, 199 insertions(+)
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 9512af7156df2..eb5256204a174 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -101,6 +101,7 @@
pub mod of;
#[cfg(CONFIG_PM_OPP)]
pub mod opp;
+pub mod owned;
pub mod page;
#[cfg(CONFIG_PCI)]
pub mod pci;
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
new file mode 100644
index 0000000000000..7fe9ec3e55126
--- /dev/null
+++ b/rust/kernel/owned.rs
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Unique owned pointer types for objects with custom drop logic.
+//!
+//! These pointer types are useful for C-allocated objects which by API-contract
+//! are owned by Rust, but need to be freed through the C API.
+
+use core::{
+ mem::ManuallyDrop,
+ ops::{
+ Deref,
+ DerefMut, //
+ },
+ pin::Pin,
+ ptr::NonNull, //
+};
+
+/// Types that specify their own way of performing allocation and destruction. Typically, this trait
+/// is implemented on types from the C side.
+///
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
+/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
+/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
+/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+///
+/// Note: The underlying object is not required to provide internal reference counting, because it
+/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
+/// [`AlwaysRefCounted`](crate::sync::aref::AlwaysRefCounted) should be implemented.
+///
+/// # Examples
+///
+/// A minimal example implementation of [`Ownable`] and its usage with [`Owned`] looks like
+/// this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::sync::global_lock;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::types::{Owned, Ownable};
+///
+/// // Let's count the allocations to see if freeing works.
+/// kernel::sync::global_lock! {
+/// // SAFETY: we call `init()` right below, before doing anything else.
+/// unsafe(uninit) static FOO_ALLOC_COUNT: Mutex<usize> = 0;
+/// }
+/// // SAFETY: We call `init()` only once, here.
+/// unsafe { FOO_ALLOC_COUNT.init() };
+///
+/// struct Foo;
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// let result = KBox::new(
+/// Foo {},
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = KBox::into_non_null(result);
+/// // Count new allocation
+/// *FOO_ALLOC_COUNT.lock() += 1;
+/// // SAFETY:
+/// // - We just allocated the `Self`, thus it is valid and we own it.
+/// // - We can transfer this ownership to the `from_raw` method.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: The [`KBox<Self>`] is still alive. We can pass ownership to the [`KBox`], as
+/// // by requirement on calling this function.
+/// drop(unsafe { KBox::from_raw(this.as_ptr()) });
+/// // Count released allocation
+/// *FOO_ALLOC_COUNT.lock() -= 1;
+/// }
+/// }
+///
+/// {
+/// let foo = Foo::new()?;
+/// assert!(*FOO_ALLOC_COUNT.lock() == 1);
+/// }
+/// // `foo` is out of scope now, so we expect no live allocations.
+/// assert!(*FOO_ALLOC_COUNT.lock() == 0);
+/// # Ok::<(), Error>(())
+/// ```
+pub trait Ownable {
+ /// Tear down this `Ownable`.
+ ///
+ /// Implementers of `Ownable` can use this function to clean up the use of `Self`. This can
+ /// include freeing the underlying object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that they have exclusive ownership of the `Self` pointed to by `this`,
+ /// and that this ownership is transferred to the `release` method. `this` must not be used
+ /// after calling this method, as the underlying object may have been freed.
+ unsafe fn release(this: NonNull<Self>);
+}
+
+/// A mutable reference to an owned `T`.
+///
+/// The [`Ownable`] is automatically freed or released when an instance of [`Owned`] is
+/// dropped.
+///
+/// # Invariants
+///
+/// - Until `T::release` is called, this `Owned<T>` exclusively owns the underlying `T`.
+/// - The `T` value is pinned.
+pub struct Owned<T: Ownable> {
+ ptr: NonNull<T>,
+}
+
+impl<T: Ownable> Owned<T> {
+ /// Creates a new instance of [`Owned`].
+ ///
+ /// This function takes over ownership of the underlying object.
+ ///
+ /// # Safety
+ ///
+ /// Callers must ensure that:
+ /// - `ptr` points to a valid instance of `T`.
+ /// - Until `T::release` is called, the returned `Owned<T>` exclusively owns the underlying `T`.
+ #[inline]
+ pub unsafe fn from_raw(ptr: NonNull<T>) -> Self {
+ // INVARIANT: By function safety requirement we satisfy the first invariant of `Self`.
+ // We treat `T` as pinned from now on.
+ Self { ptr }
+ }
+
+ /// Consumes the [`Owned`], returning a raw pointer.
+ ///
+ /// This function does not drop the underlying `T`. When this function returns, ownership of the
+ /// underlying `T` is with the caller.
+ #[inline]
+ pub fn into_raw(me: Self) -> NonNull<T> {
+ ManuallyDrop::new(me).ptr
+ }
+
+ /// Get a pinned mutable reference to the data owned by this `Owned<T>`.
+ #[inline]
+ pub fn as_pin_mut(&mut self) -> Pin<&mut T> {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ let unpinned = unsafe { self.ptr.as_mut() };
+
+ // SAFETY: By type invariant `T` is pinned.
+ unsafe { Pin::new_unchecked(unpinned) }
+ }
+}
+
+// SAFETY: It is safe to send an [`Owned<T>`] to another thread when the underlying `T` is [`Send`],
+// because of the ownership invariant. Sending an [`Owned<T>`] is equivalent to sending the `T`.
+unsafe impl<T: Ownable + Send> Send for Owned<T> {}
+
+// SAFETY: It is safe to send [`&Owned<T>`] to another thread when the underlying `T` is [`Sync`],
+// because of the ownership invariant. Sending an [`&Owned<T>`] is equivalent to sending the `&T`.
+unsafe impl<T: Ownable + Sync> Sync for Owned<T> {}
+
+impl<T: Ownable> Deref for Owned<T> {
+ type Target = T;
+
+ #[inline]
+ fn deref(&self) -> &Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid.
+ unsafe { self.ptr.as_ref() }
+ }
+}
+
+impl<T: Ownable + Unpin> DerefMut for Owned<T> {
+ #[inline]
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ // SAFETY: The type invariants guarantee that the object is valid, and that we can safely
+ // return a mutable reference to it.
+ unsafe { self.ptr.as_mut() }
+ }
+}
+
+impl<T: Ownable> Drop for Owned<T> {
+ #[inline]
+ fn drop(&mut self) {
+ // SAFETY: By existence of `&mut self` we exclusively own `self` and the underlying `T`. As
+ // we are dropping `self`, we can transfer ownership of the `T` to the `release` method.
+ unsafe { T::release(self.ptr) };
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index b721b2e00b986..3bd5eb8a1a526 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -34,6 +34,11 @@
/// Rust code, the recommendation is to use [`Arc`](crate::sync::Arc) to create reference-counted
/// instances of a type.
///
+/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
+/// internal reference count and provides only shared references. If unique references are required
+/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
+/// [`Owned<Self>`](crate::types::Owned).
+///
/// # Safety
///
/// Implementers must ensure that increments to the reference count keep the object alive in memory
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index ac316fd7b538f..c41eab0ec983c 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -15,6 +15,11 @@
pub mod for_lt;
pub use for_lt::ForLt;
+pub use crate::owned::{
+ Ownable,
+ Owned, //
+};
+
/// Used to transfer ownership to and from foreign (non-Rust) languages.
///
/// Ownership is transferred from Rust to a foreign language by calling [`Self::into_foreign`] and
--
2.51.2
^ permalink raw reply related
* [PATCH v18 8/8] rust: page: add `from_raw()`
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Andreas Hindborg
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Andreas Hindborg <a.hindborg@samsung.com>
Add a method to `Page` that allows construction of an instance from `struct
page` pointer.
Signed-off-by: Andreas Hindborg <a.hindborg@samsung.com>
Reviewed-by: Onur Özkan <work@onurozkan.dev>
---
rust/kernel/page.rs | 14 ++++++++++++++
1 file changed, 14 insertions(+)
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 6dc1c2395acaf..c88fda09ead5a 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -143,6 +143,20 @@ pub fn nid(&self) -> i32 {
unsafe { bindings::page_to_nid(self.as_ptr()) }
}
+ /// Create a `&Page` from a raw `struct page` pointer.
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must be convertible to a shared reference with a lifetime of `'a`.
+ #[inline]
+ pub unsafe fn from_raw<'a>(ptr: *const bindings::page) -> &'a Self {
+ // INVARIANT: By the function safety requirements, `ptr` refers to a valid `struct page`, so
+ // the returned reference upholds the type invariant of `Page`.
+ // SAFETY: By function safety requirements, `ptr` is not null and is convertible to a shared
+ // reference.
+ unsafe { &*ptr.cast() }
+ }
+
/// Runs a piece of code with this page mapped to an address.
///
/// The page is unmapped when this call returns.
--
2.51.2
^ permalink raw reply related
* [PATCH v18 4/8] rust: page: convert to `Ownable`
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Asahi Lina
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Asahi Lina <lina@asahilina.net>
This allows Page references to be returned as borrowed references,
without necessarily owning the struct page.
Remove `BorrowedPage` and update users to use `Owned<Page>`.
Signed-off-by: Asahi Lina <lina@asahilina.net>
[ Andreas: Fix formatting and add a safety comment, update users. ]
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
drivers/android/binder/page_range.rs | 10 +--
rust/kernel/alloc/allocator.rs | 19 +++---
rust/kernel/alloc/allocator/iter.rs | 6 +-
rust/kernel/page.rs | 122 +++++++++--------------------------
4 files changed, 46 insertions(+), 111 deletions(-)
diff --git a/drivers/android/binder/page_range.rs b/drivers/android/binder/page_range.rs
index e54a90e62402a..7941eb85b4ef4 100644
--- a/drivers/android/binder/page_range.rs
+++ b/drivers/android/binder/page_range.rs
@@ -33,7 +33,7 @@
sync::{aref::ARef, Mutex, SpinLock},
task::Pid,
transmute::FromBytes,
- types::Opaque,
+ types::{Opaque, Owned},
uaccess::UserSliceReader,
};
@@ -198,7 +198,7 @@ unsafe impl Send for Inner {}
#[repr(C)]
struct PageInfo {
lru: bindings::list_head,
- page: Option<Page>,
+ page: Option<Owned<Page>>,
range: *const ShrinkablePageRange,
}
@@ -206,7 +206,7 @@ impl PageInfo {
/// # Safety
///
/// The caller ensures that writing to `me.page` is ok, and that the page is not currently set.
- unsafe fn set_page(me: *mut PageInfo, page: Page) {
+ unsafe fn set_page(me: *mut PageInfo, page: Owned<Page>) {
// SAFETY: This pointer offset is in bounds.
let ptr = unsafe { &raw mut (*me).page };
@@ -229,13 +229,13 @@ unsafe fn get_page<'a>(me: *const PageInfo) -> Option<&'a Page> {
let ptr = unsafe { &raw const (*me).page };
// SAFETY: The pointer is valid for reading.
- unsafe { (*ptr).as_ref() }
+ unsafe { (*ptr).as_deref() }
}
/// # Safety
///
/// The caller ensures that writing to `me.page` is ok for the duration of 'a.
- unsafe fn take_page(me: *mut PageInfo) -> Option<Page> {
+ unsafe fn take_page(me: *mut PageInfo) -> Option<Owned<Page>> {
// SAFETY: This pointer offset is in bounds.
let ptr = unsafe { &raw mut (*me).page };
diff --git a/rust/kernel/alloc/allocator.rs b/rust/kernel/alloc/allocator.rs
index cd4203f27aed0..c7b9b069cf75d 100644
--- a/rust/kernel/alloc/allocator.rs
+++ b/rust/kernel/alloc/allocator.rs
@@ -169,7 +169,7 @@ unsafe fn realloc(
}
impl Vmalloc {
- /// Convert a pointer to a [`Vmalloc`] allocation to a [`page::BorrowedPage`].
+ /// Convert a pointer to a [`Vmalloc`] allocation to a [`Page`](page::Page) reference.
///
/// # Examples
///
@@ -202,20 +202,17 @@ impl Vmalloc {
///
/// - `ptr` must be a valid pointer to a [`Vmalloc`] allocation.
/// - `ptr` must remain valid for the entire duration of `'a`.
- pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> page::BorrowedPage<'a> {
+ pub unsafe fn to_page<'a>(ptr: NonNull<u8>) -> &'a page::Page {
// SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
let page = unsafe { bindings::vmalloc_to_page(ptr.as_ptr().cast()) };
- // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid pointer
- // to `Vmalloc` memory.
- let page = unsafe { NonNull::new_unchecked(page) };
-
// SAFETY:
- // - `page` is a valid pointer to a `struct page`, given that by the safety requirements of
- // this function `ptr` is a valid pointer to a `Vmalloc` allocation.
- // - By the safety requirements of this function `ptr` is valid for the entire lifetime of
- // `'a`.
- unsafe { page::BorrowedPage::from_raw(page) }
+ // - `vmalloc_to_page` returns a valid, non-null pointer to a `struct page` for a valid
+ // pointer to `Vmalloc` memory, given that by the safety requirements of this function
+ // `ptr` is a valid pointer to a `Vmalloc` allocation.
+ // - By the safety requirements of this function `ptr`, and hence the `struct page`, is
+ // valid for the entire lifetime of `'a`.
+ unsafe { &*page.cast() }
}
}
diff --git a/rust/kernel/alloc/allocator/iter.rs b/rust/kernel/alloc/allocator/iter.rs
index 02fda3ea5cae6..8dcc16ed89893 100644
--- a/rust/kernel/alloc/allocator/iter.rs
+++ b/rust/kernel/alloc/allocator/iter.rs
@@ -9,7 +9,7 @@
ptr::NonNull, //
};
-/// An [`Iterator`] of [`page::BorrowedPage`] items owned by a [`Vmalloc`] allocation.
+/// An [`Iterator`] of [`Page`](page::Page) references owned by a [`Vmalloc`] allocation.
///
/// # Guarantees
///
@@ -28,11 +28,11 @@ pub struct VmallocPageIter<'a> {
size: usize,
/// The current page index of the [`Iterator`].
index: usize,
- _p: PhantomData<page::BorrowedPage<'a>>,
+ _p: PhantomData<&'a page::Page>,
}
impl<'a> Iterator for VmallocPageIter<'a> {
- type Item = page::BorrowedPage<'a>;
+ type Item = &'a page::Page;
fn next(&mut self) -> Option<Self::Item> {
let offset = self.index.checked_mul(page::PAGE_SIZE)?;
diff --git a/rust/kernel/page.rs b/rust/kernel/page.rs
index 8affd8262891b..6dc1c2395acaf 100644
--- a/rust/kernel/page.rs
+++ b/rust/kernel/page.rs
@@ -12,16 +12,16 @@
code::*,
Result, //
},
+ types::{
+ Opaque,
+ Ownable,
+ Owned, //
+ },
uaccess::UserSliceReader, //
};
-use core::{
- marker::PhantomData,
- mem::ManuallyDrop,
- ops::Deref,
- ptr::{
- self,
- NonNull, //
- }, //
+use core::ptr::{
+ self,
+ NonNull, //
};
/// A bitwise shift for the page size.
@@ -65,93 +65,29 @@ pub const fn page_align(addr: usize) -> Option<usize> {
Some(sum & PAGE_MASK)
}
-/// Representation of a non-owning reference to a [`Page`].
-///
-/// This type provides a borrowed version of a [`Page`] that is owned by some other entity, e.g. a
-/// [`Vmalloc`] allocation such as [`VBox`].
-///
-/// # Example
-///
-/// ```
-/// # use kernel::{bindings, prelude::*};
-/// use kernel::page::{BorrowedPage, Page, PAGE_SIZE};
-/// # use core::{mem::MaybeUninit, ptr, ptr::NonNull };
-///
-/// fn borrow_page<'a>(vbox: &'a mut VBox<MaybeUninit<[u8; PAGE_SIZE]>>) -> BorrowedPage<'a> {
-/// let ptr = ptr::from_ref(&**vbox);
-///
-/// // SAFETY: `ptr` is a valid pointer to `Vmalloc` memory.
-/// let page = unsafe { bindings::vmalloc_to_page(ptr.cast()) };
-///
-/// // SAFETY: `vmalloc_to_page` returns a valid pointer to a `struct page` for a valid
-/// // pointer to `Vmalloc` memory.
-/// let page = unsafe { NonNull::new_unchecked(page) };
-///
-/// // SAFETY:
-/// // - `self.0` is a valid pointer to a `struct page`.
-/// // - `self.0` is valid for the entire lifetime of `self`.
-/// unsafe { BorrowedPage::from_raw(page) }
-/// }
-///
-/// let mut vbox = VBox::<[u8; PAGE_SIZE]>::new_uninit(GFP_KERNEL)?;
-/// let page = borrow_page(&mut vbox);
-///
-/// // SAFETY: There is no concurrent read or write to this page.
-/// unsafe { page.fill_zero_raw(0, PAGE_SIZE)? };
-/// # Ok::<(), Error>(())
-/// ```
-///
-/// # Invariants
-///
-/// The borrowed underlying pointer to a `struct page` is valid for the entire lifetime `'a`.
-///
-/// [`VBox`]: kernel::alloc::VBox
-/// [`Vmalloc`]: kernel::alloc::allocator::Vmalloc
-pub struct BorrowedPage<'a>(ManuallyDrop<Page>, PhantomData<&'a Page>);
-
-impl<'a> BorrowedPage<'a> {
- /// Constructs a [`BorrowedPage`] from a raw pointer to a `struct page`.
- ///
- /// # Safety
- ///
- /// - `ptr` must point to a valid `bindings::page`.
- /// - `ptr` must remain valid for the entire lifetime `'a`.
- pub unsafe fn from_raw(ptr: NonNull<bindings::page>) -> Self {
- let page = Page { page: ptr };
-
- // INVARIANT: The safety requirements guarantee that `ptr` is valid for the entire lifetime
- // `'a`.
- Self(ManuallyDrop::new(page), PhantomData)
- }
-}
-
-impl<'a> Deref for BorrowedPage<'a> {
- type Target = Page;
-
- fn deref(&self) -> &Self::Target {
- &self.0
- }
-}
-
-/// Trait to be implemented by types which provide an [`Iterator`] implementation of
-/// [`BorrowedPage`] items, such as [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
+/// Trait to be implemented by types which provide an [`Iterator`] of [`Page`] references, such as
+/// [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
pub trait AsPageIter {
/// The [`Iterator`] type, e.g. [`VmallocPageIter`](kernel::alloc::allocator::VmallocPageIter).
- type Iter<'a>: Iterator<Item = BorrowedPage<'a>>
+ type Iter<'a>: Iterator<Item = &'a Page>
where
Self: 'a;
- /// Returns an [`Iterator`] of [`BorrowedPage`] items over all pages owned by `self`.
+ /// Returns an [`Iterator`] of [`Page`] references over all pages owned by `self`.
fn page_iter(&mut self) -> Self::Iter<'_>;
}
-/// A pointer to a page that owns the page allocation.
+/// A `struct page`.
+///
+/// A `Page` is accessed through a shared reference or through an owning [`Owned<Page>`]; the latter
+/// frees the page allocation when it is dropped.
///
/// # Invariants
///
-/// The pointer is valid, and has ownership over the page.
+/// The `Page` is backed by a valid `struct page`.
+#[repr(transparent)]
pub struct Page {
- page: NonNull<bindings::page>,
+ page: Opaque<bindings::page>,
}
// SAFETY: Pages have no logic that relies on them staying on a given thread, so moving them across
@@ -185,19 +121,20 @@ impl Page {
/// # Ok::<(), kernel::alloc::AllocError>(())
/// ```
#[inline]
- pub fn alloc_page(flags: Flags) -> Result<Self, AllocError> {
+ pub fn alloc_page(flags: Flags) -> Result<Owned<Self>, AllocError> {
// SAFETY: Depending on the value of `gfp_flags`, this call may sleep. Other than that, it
// is always safe to call this method.
let page = unsafe { bindings::alloc_pages(flags.as_raw(), 0) };
let page = NonNull::new(page).ok_or(AllocError)?;
- // INVARIANT: We just successfully allocated a page, so we now have ownership of the newly
- // allocated page. We transfer that ownership to the new `Page` object.
- Ok(Self { page })
+ // SAFETY: We just successfully allocated a page, so we now have ownership of the newly
+ // allocated page. We transfer that ownership to the new `Owned<Page>` object.
+ // Since `Page` is transparent, we can cast the pointer directly.
+ Ok(unsafe { Owned::from_raw(page.cast()) })
}
/// Returns a raw pointer to the page.
pub fn as_ptr(&self) -> *mut bindings::page {
- self.page.as_ptr()
+ Opaque::cast_into(&self.page)
}
/// Get the node id containing this page.
@@ -372,10 +309,11 @@ pub unsafe fn copy_from_user_slice_raw(
}
}
-impl Drop for Page {
+impl Ownable for Page {
#[inline]
- fn drop(&mut self) {
- // SAFETY: By the type invariants, we have ownership of the page and can free it.
- unsafe { bindings::__free_pages(self.page.as_ptr(), 0) };
+ unsafe fn release(this: NonNull<Self>) {
+ // SAFETY: By the function safety requirements, we have ownership of the page and can free
+ // it. Since Page is transparent, we can cast the raw pointer directly.
+ unsafe { bindings::__free_pages(this.as_ptr().cast(), 0) };
}
}
--
2.51.2
^ permalink raw reply related
* [PATCH v18 7/8] rust: Add `OwnableRefCounted`
From: Andreas Hindborg @ 2026-06-25 10:15 UTC (permalink / raw)
To: Danilo Krummrich, Lorenzo Stoakes, Vlastimil Babka,
Liam R. Howlett, Uladzislau Rezki, Miguel Ojeda, Boqun Feng,
Gary Guo, Björn Roy Baron, Benno Lossin, Alice Ryhl,
Trevor Gross, Daniel Almeida, Tamir Duberstein, Alexandre Courbot,
Onur Özkan, Lyude Paul, Greg Kroah-Hartman,
Arve Hjønnevåg, Todd Kjos, Christian Brauner,
Carlos Llamas, Rafael J. Wysocki, Dave Ertman, Ira Weiny,
Leon Romanovsky, Paul Moore, Serge Hallyn, David Airlie,
Simona Vetter, Alexander Viro, Jan Kara, Igor Korotin,
Viresh Kumar, Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Pavel Tikhomirov, Michal Wilczynski
Cc: Andreas Hindborg, Philipp Stanner, rust-for-linux, linux-kernel,
linux-mm, driver-core, linux-block, linux-security-module,
dri-devel, linux-fsdevel, linux-pm, linux-pci, linux-pwm,
Oliver Mangold
In-Reply-To: <20260625-unique-ref-v18-0-4e06b5896d47@kernel.org>
From: Oliver Mangold <oliver.mangold@pm.me>
Types implementing one of these traits can safely convert between an
`ARef<T>` and an `Owned<T>`.
This is useful for types which generally are accessed through an `ARef`
but have methods which can only safely be called when the reference is
unique, like e.g. `block::mq::Request::end_ok()`.
Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
[ Andreas: Fix formatting, update documentation, fix error handling in
examples. ]
Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
rust/kernel/owned.rs | 140 +++++++++++++++++++++++++++++++++++++++++++++--
rust/kernel/sync/aref.rs | 16 +++++-
rust/kernel/types.rs | 1 +
3 files changed, 151 insertions(+), 6 deletions(-)
diff --git a/rust/kernel/owned.rs b/rust/kernel/owned.rs
index e79936c00002c..bb4223c0f725a 100644
--- a/rust/kernel/owned.rs
+++ b/rust/kernel/owned.rs
@@ -14,20 +14,26 @@
pin::Pin,
ptr::NonNull, //
};
+use kernel::{
+ sync::aref::ARef,
+ types::RefCounted, //
+};
use kernel::types::ForeignOwnable;
/// Types that specify their own way of performing allocation and destruction. Typically, this trait
/// is implemented on types from the C side.
///
-/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type. This
-/// is useful when it is desirable to tie the lifetime of the reference to an owned object, rather
-/// than pass around a bare reference. [`Ownable`] types can define custom drop logic that is
-/// executed when the owned reference [`Owned<Self>`] pointing to the object is dropped.
+/// Implementing this trait allows types to be referenced via the [`Owned<Self>`] pointer type.
+/// - This is useful when it is desirable to tie the lifetime of an object reference to an owned
+/// object, rather than pass around a bare reference.
+/// - [`Ownable`] types can define custom drop logic that is executed when the owned reference
+/// of type [`Owned<_>`] pointing to the object is dropped.
///
/// Note: The underlying object is not required to provide internal reference counting, because it
/// represents a unique, owned reference. If reference counting (on the Rust side) is required,
-/// [`RefCounted`](crate::types::RefCounted) should be implemented.
+/// [`RefCounted`] should be implemented. [`OwnableRefCounted`] should be implemented if conversion
+/// between unique and shared (reference counted) ownership is needed.
///
/// # Examples
///
@@ -239,3 +245,127 @@ unsafe fn borrow_mut<'a>(ptr: *mut kernel::ffi::c_void) -> Self::BorrowedMut<'a>
unsafe { Pin::new_unchecked(inner) }
}
}
+
+/// A trait for objects that can be wrapped in either one of the reference types [`Owned`] and
+/// [`ARef`].
+///
+/// # Examples
+///
+/// A minimal example implementation of [`OwnableRefCounted`], [`Ownable`] and its usage with
+/// [`ARef`] and [`Owned`] looks like this:
+///
+/// ```
+/// # #![expect(clippy::disallowed_names)]
+/// # use core::cell::Cell;
+/// # use core::ptr::NonNull;
+/// # use kernel::alloc::{flags, kbox::KBox, AllocError};
+/// # use kernel::sync::aref::{ARef, RefCounted};
+/// # use kernel::types::{Owned, Ownable, OwnableRefCounted};
+///
+/// // An internally refcounted struct for demonstration purposes.
+/// //
+/// // # Invariants
+/// //
+/// // - `refcount` is always non-zero for a valid object.
+/// // - `refcount` is >1 if there is more than one Rust reference to it.
+/// //
+/// struct Foo {
+/// refcount: Cell<usize>,
+/// }
+///
+/// impl Foo {
+/// fn new() -> Result<Owned<Self>> {
+/// // We are just using a `KBox` here to handle the actual allocation, as our `Foo` is
+/// // not actually a C-allocated object.
+/// // INVARIANT: We initialize `refcount` to 1, satisfying the invariants.
+/// let result = KBox::new(
+/// Foo {
+/// refcount: Cell::new(1),
+/// },
+/// flags::GFP_KERNEL,
+/// )?;
+/// let result = KBox::into_non_null(result);
+/// // SAFETY:
+/// // - We just allocated the `Self`, thus it is valid and we own it.
+/// // - We can transfer this ownership to the `from_raw` method.
+/// Ok(unsafe { Owned::from_raw(result) })
+/// }
+/// }
+///
+/// // SAFETY: We increment and decrement each time the respective function is called and only free
+/// // the `Foo` when the refcount reaches zero.
+/// unsafe impl RefCounted for Foo {
+/// fn inc_ref(&self) {
+/// self.refcount.replace(self.refcount.get() + 1);
+/// }
+///
+/// unsafe fn dec_ref(this: NonNull<Self>) {
+/// // SAFETY: By requirement on calling this function, the refcount is non-zero,
+/// // implying the underlying object is valid.
+/// let refcount = unsafe { &this.as_ref().refcount };
+/// let new_refcount = refcount.get() - 1;
+/// if new_refcount == 0 {
+/// // The `Foo` will be dropped when `KBox` goes out of scope.
+/// // SAFETY: The [`KBox<Foo>`] is still alive as the old refcount is 1. We can pass
+/// // ownership to the [`KBox`] as by requirement on calling this function,
+/// // the `Self` will no longer be used by the caller.
+/// unsafe { KBox::from_raw(this.as_ptr()) };
+/// } else {
+/// refcount.replace(new_refcount);
+/// }
+/// }
+/// }
+///
+/// impl OwnableRefCounted for Foo {
+/// fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>> {
+/// if this.refcount.get() == 1 {
+/// // SAFETY: The `Foo` is still alive and has no other Rust references as the refcount
+/// // is 1.
+/// Ok(unsafe { Owned::from_raw(ARef::into_raw(this)) })
+/// } else {
+/// Err(this)
+/// }
+/// }
+/// }
+///
+/// impl Ownable for Foo {
+/// unsafe fn release(this: NonNull<Self>) {
+/// // SAFETY: Using `dec_ref()` from [`RefCounted`] to release is okay, as the refcount is
+/// // always 1 for an [`Owned<Foo>`].
+/// unsafe { Foo::dec_ref(this) };
+/// }
+/// }
+///
+/// let foo = Foo::new()?;
+/// let foo = ARef::from(foo);
+/// {
+/// let bar = foo.clone();
+/// assert!(Owned::try_from(bar).is_err());
+/// }
+/// assert!(Owned::try_from(foo).is_ok());
+/// # Ok::<(), Error>(())
+/// ```
+pub trait OwnableRefCounted: RefCounted + Ownable + Sized {
+ /// Checks if the [`ARef`] is unique and converts it to an [`Owned`] if that is the case.
+ /// Otherwise it returns again an [`ARef`] to the same underlying object.
+ fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>>;
+
+ /// Converts the [`Owned`] into an [`ARef`].
+ #[inline]
+ fn into_shared(this: Owned<Self>) -> ARef<Self> {
+ // SAFETY: `Owned::into_raw` returns a pointer to a valid `Self`, and the `Owned` owned the
+ // reference count that we now transfer to the new `ARef`.
+ unsafe { ARef::from_raw(Owned::into_raw(this)) }
+ }
+}
+
+impl<T: OwnableRefCounted> TryFrom<ARef<T>> for Owned<T> {
+ type Error = ARef<T>;
+ /// Tries to convert the [`ARef`] to an [`Owned`] by calling
+ /// [`try_from_shared()`](OwnableRefCounted::try_from_shared). In case the [`ARef`] is not
+ /// unique, it returns again an [`ARef`] to the same underlying object.
+ #[inline]
+ fn try_from(b: ARef<T>) -> Result<Owned<T>, Self::Error> {
+ T::try_from_shared(b)
+ }
+}
diff --git a/rust/kernel/sync/aref.rs b/rust/kernel/sync/aref.rs
index d0865aeb9371b..77eb390139079 100644
--- a/rust/kernel/sync/aref.rs
+++ b/rust/kernel/sync/aref.rs
@@ -23,6 +23,10 @@
ops::Deref,
ptr::NonNull, //
};
+use kernel::types::{
+ OwnableRefCounted,
+ Owned, //
+};
/// Types that are internally reference counted.
///
@@ -35,7 +39,10 @@
/// Note: Implementing this trait allows types to be wrapped in an [`ARef<Self>`]. It requires an
/// internal reference count and provides only shared references. If unique references are required
/// [`Ownable`](crate::types::Ownable) should be implemented which allows types to be wrapped in an
-/// [`Owned<Self>`](crate::types::Owned).
+/// [`Owned<Self>`](crate::types::Owned). Implementing the trait
+/// [`OwnableRefCounted`] allows to convert between unique and
+/// shared references (i.e. [`Owned<Self>`](crate::types::Owned) and
+/// [`ARef<Self>`](crate::types::Owned)).
///
/// # Safety
///
@@ -188,6 +195,13 @@ fn from(b: &T) -> Self {
}
}
+impl<T: OwnableRefCounted> From<Owned<T>> for ARef<T> {
+ #[inline]
+ fn from(b: Owned<T>) -> Self {
+ T::into_shared(b)
+ }
+}
+
impl<T: RefCounted> Drop for ARef<T> {
fn drop(&mut self) {
// SAFETY: The type invariants guarantee that the `ARef` owns the reference we're about to
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 5ef763717e59a..6aa760952cb63 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -18,6 +18,7 @@
pub use crate::{
owned::{
Ownable,
+ OwnableRefCounted,
Owned, //
},
sync::aref::{
--
2.51.2
^ permalink raw reply related
* Re: [PATCH v4 2/2] rust: introduce abstractions for fwctl
From: Zhi Wang @ 2026-06-25 8:24 UTC (permalink / raw)
To: Danilo Krummrich
Cc: rust-for-linux, linux-kernel, jgg, gary, joelagnelf, aliceryhl,
kwilczynski, ojeda, alex.gaynor, boqun.feng, bjorn3_gh, lossin,
a.hindborg, tmgross, cjia, smitra, ankita, aniketa, kwankhede,
targupta, kjaju, alkumar, acourbot, jhubbard, zhiwang,
daniel.almeida
In-Reply-To: <DJHGQN654CJR.281FZSV2S5AI8@kernel.org>
On Wed, 24 Jun 2026 19:41:45 +0200
"Danilo Krummrich" <dakr@kernel.org> wrote:
> On Wed Jun 24, 2026 at 11:17 AM CEST, Zhi Wang wrote:
> > +impl<T: Operations> Device<T> {
snip
> I have recently been working on getting rid of Devres for
> Registration types and device resources in favor of Rust-native
> lifetimes using higher-ranked types (HRT). This has a couple of
> advantages, e.g. it simplifies accessing device resources from
> destructors and (with pin-init self-referential support) allows us to
> share (Rust) references between private data structures.
>
> This has been merged for existing device resources, bus device
> private data and auxiliary registration data [1]. There's also a
> follow-up series to support invariance [2] and another one to enable
> it for the DRM subsystem [3].
>
Hi Danilo:
Thanks so much for the pointers. I went through the HRT series. If we
are getting rid of the Devres with HRT, then my PATCH 1 is not required
as well. I actually got this callback example from DRM subsystem.
> Class devices infrastructure should follow that same pattern, i.e. the
> fwctl::Registration type should gain a lifetime and the fwctl private
> data provided via fwctl callbacks should be tied to the lifetime of
> the Registration, i.e. the lifetime the underlying bus device is
> bound to the driver.
>
Got it.
> Please find a diff in [4] implementing this for fwctl and a diff in
> [5] demonstrating how this is used in nova-core. (Feel free to pick
> up the provided code and use it in any way.)
>
Thanks so much. I will take a look and re-spin it today.
> (Please ignore that I use fwctl::DeviceType::Mlx5 in the nova-core
> diff, it is just there to make the code compile, so I could do a
> smoke test.)
>
> Thanks,
> Danilo
>
> [1]
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2c7c65933600e8db2ec1a78dec5008de876dd3ad
> [2]
> https://lore.kernel.org/driver-core/20260618230834.812007-1-dakr@kernel.org/
> [3]
> https://lore.kernel.org/driver-core/20260620184924.2247517-1-dakr@kernel.org/
>
> [4] FWCTL diff:
>
> diff --git a/rust/kernel/fwctl.rs b/rust/kernel/fwctl.rs
> index f5f802f5299c..65abea866b22 100644
> --- a/rust/kernel/fwctl.rs
> +++ b/rust/kernel/fwctl.rs
> @@ -8,16 +8,20 @@
> bindings,
> container_of,
> device,
> - devres::Devres,
> prelude::*,
> sync::aref::{
> ARef,
> AlwaysRefCounted, //
> },
> - types::Opaque, //
> + types::{
> + ForLt,
> + Opaque, //
> + }, //
> };
> use core::{
> + cell::UnsafeCell,
> marker::PhantomData,
> + mem,
> ptr::NonNull,
> slice, //
> };
> @@ -89,8 +93,12 @@ pub enum FwRpcResponse {
> /// vtable used by the core `fwctl` layer to manage per-FD user
> contexts and /// handle RPC requests.
> pub trait Operations: Sized + Send + Sync {
> - /// Driver data embedded alongside the `fwctl_device` allocation.
> - type DeviceData: Send + Sync;
> + /// Data owned by the [`Registration`] and accessible during
> callbacks.
> + ///
> + /// This is a [`ForLt`](trait@ForLt) type whose lifetime is tied
> to the parent bus device
> + /// binding scope. Drivers use this to store references to
> resources bound to this scope, such as PCI
> + /// BARs or typed bus device references.
> + type RegistrationData: ForLt;
>
> /// fwctl device type identifier.
> const DEVICE_TYPE: DeviceType;
> @@ -99,57 +107,68 @@ pub trait Operations: Sized + Send + Sync {
> ///
> /// Returns a [`PinInit`] initializer for `Self`. The instance
> is dropped /// automatically when the FD is closed (after
> [`close`](Self::close)).
> - fn open(device: &Device<Self>) -> impl PinInit<Self, Error>;
> + fn open<'a>(
> + device: &'a Device<Self>,
> + reg_data: &'a <Self::RegistrationData as ForLt>::Of<'a>,
> + ) -> impl PinInit<Self, Error>;
>
> /// Called when the user context is closed.
> ///
> /// The driver may perform additional cleanup here that requires
> access /// to the owning [`Device`]. `Self` is dropped automatically
> after this /// returns.
> - fn close(_this: Pin<&mut Self>, _device: &Device<Self>) {}
> + fn close<'a>(
> + _this: Pin<&mut Self>,
> + _device: &'a Device<Self>,
> + _reg_data: &'a <Self::RegistrationData as ForLt>::Of<'a>,
> + ) {
> + }
>
> /// Return device information to userspace.
> ///
> /// The default implementation returns no device-specific data.
> - fn info(_this: Pin<&Self>, _device: &Device<Self>) ->
> Result<KVec<u8>, Error> {
> + fn info<'a>(
> + _this: Pin<&Self>,
> + _device: &'a Device<Self>,
> + _reg_data: &'a <Self::RegistrationData as ForLt>::Of<'a>,
> + ) -> Result<KVec<u8>, Error> {
> Ok(KVec::new())
> }
>
> /// Handle a userspace RPC request.
> - fn fw_rpc(
> + fn fw_rpc<'a>(
> this: Pin<&Self>,
> - device: &Device<Self>,
> + device: &'a Device<Self>,
> + reg_data: &'a <Self::RegistrationData as ForLt>::Of<'a>,
> scope: RpcScope,
> rpc_in: &mut [u8],
> ) -> Result<FwRpcResponse, Error>;
> }
>
> -/// A fwctl device with embedded driver data.
> +/// A fwctl device.
> ///
> -/// `#[repr(C)]` with the `fwctl_device` at offset 0, matching the C
> -/// `fwctl_alloc_device()` layout convention.
> +/// `#[repr(C)]` with the `fwctl_device` at offset 0, matching the C
> `fwctl_alloc_device()` layout +/// convention. Contains a pointer to
> the [`Registration`]'s data, set at registration time and +///
> cleared on unregistration. ///
> /// # Invariants
> ///
> /// - `dev` is embedded at offset 0 and is initialised by fwctl.
> /// - The fwctl refcount owns the allocation lifetime.
> -/// - `data` is dropped from the fwctl core release hook before
> `kfree()`. +/// - `registration_data` is either `NonNull::dangling()`
> (before registration / after +/// unregistration) or points to a
> valid `RegistrationData` owned by the [`Registration`]. #[repr(C)]
> pub struct Device<T: Operations> {
> dev: Opaque<bindings::fwctl_device>,
> - data: T::DeviceData,
> + registration_data: UnsafeCell<NonNull<<T::RegistrationData as
> ForLt>::Of<'static>>>, }
>
> impl<T: Operations> Device<T> {
> - /// Allocate a new fwctl device with embedded driver data.
> + /// Allocate a new fwctl device.
> ///
> /// Returns an [`ARef`] that can be passed to
> [`Registration::new()`]
> - /// to make the device visible to userspace. The caller may
> inspect or
> - /// configure the device between allocation and registration.
> - pub fn new(
> - parent: &device::Device<device::Bound>,
> - data: impl PinInit<T::DeviceData, Error>,
> - ) -> Result<ARef<Self>> {
> + /// to make the device visible to userspace.
> + pub fn new(parent: &device::Device<device::Bound>) ->
> Result<ARef<Self>> { const_assert!(
> core::mem::offset_of!(Self, dev) == 0,
> "struct fwctl_device must be at offset 0"
> @@ -157,8 +176,7 @@ pub fn new(
>
> let ops =
> core::ptr::from_ref::<bindings::fwctl_ops>(&VTable::<T>::VTABLE).cast_mut();
> - // SAFETY: `ops` is static, `parent` is bound, and `size`
> includes the
> - // offset-0 `fwctl_device` plus `DeviceData`.
> + // SAFETY: `ops` is static, `parent` is bound, and `size`
> covers the full `Device<T>`. let raw = unsafe {
> bindings::_fwctl_alloc_device(parent.as_raw(), ops,
> core::mem::size_of::<Self>()) };
> @@ -169,42 +187,21 @@ pub fn new(
>
> let this = raw.cast::<Self>();
>
> + // INVARIANT: Set `registration_data` to dangling (no
> registration yet). // SAFETY: `this` points to the allocation just
> returned by fwctl.
> - let data_ptr = unsafe {
> core::ptr::addr_of_mut!((*this).data) };
> - // SAFETY: `data_ptr` addresses the uninitialised tail data.
> - unsafe { data.__pinned_init(data_ptr) }.inspect_err(|_| {
> - // SAFETY: `raw` still owns the initial reference.
> - unsafe { bindings::fwctl_put(raw) };
> - })?;
> -
> - // SAFETY: `raw` is a live fwctl_device allocated above.
> - unsafe { (*raw).release_data =
> Some(Self::release_data_callback) }; -
> - // SAFETY: `raw` owns the initial reference and `DeviceData`
> is ready.
> - Ok(unsafe {
> ARef::from_raw(NonNull::new(raw.cast::<Self>()).ok_or(ENOMEM)?) })
> - }
> + unsafe {
> + core::ptr::addr_of_mut!((*this).registration_data)
> + .write(UnsafeCell::new(NonNull::dangling()));
> + };
>
> - /// Returns a reference to the embedded driver data.
> - pub fn data(&self) -> &T::DeviceData {
> - &self.data
> + // SAFETY: `raw` owns the initial reference.
> + Ok(unsafe { ARef::from_raw(NonNull::new_unchecked(this)) })
> }
>
> fn as_raw(&self) -> *mut bindings::fwctl_device {
> self.dev.get()
> }
>
> - /// # Safety
> - ///
> - /// `raw` must point to an offset-0 `fwctl_device` embedded in
> `Device<T>`.
> - /// fwctl calls this exactly once from the device release path.
> - unsafe extern "C" fn release_data_callback(raw: *mut
> bindings::fwctl_device) {
> - let this = raw.cast::<Self>();
> -
> - // SAFETY: fwctl invokes this callback once during the final
> device
> - // release, before freeing the allocation.
> - unsafe {
> core::ptr::drop_in_place(core::ptr::addr_of_mut!((*this).data)) };
> - }
> -
> /// # Safety
> ///
> /// `ptr` must point to a valid `fwctl_device` embedded in a
> `Device<T>`. @@ -213,18 +210,17 @@ unsafe fn from_raw<'a>(ptr: *mut
> bindings::fwctl_device) -> &'a Self { unsafe { &*ptr.cast() }
> }
>
> - /// Returns the parent device.
> + /// Returns a reference to the registration data.
> + ///
> + /// # Safety
> ///
> - /// The parent is guaranteed to be bound while any fwctl
> callback is
> - /// running (ensured by the `registration_lock` read lock on the
> ioctl
> - /// path and by `Devres` on the teardown path).
> - pub fn parent(&self) -> &device::Device<device::Bound> {
> - // SAFETY: fwctl sets the parent during allocation.
> - let parent_dev = unsafe { (*self.as_raw()).dev.parent };
> - // SAFETY: The parent stays live while fwctl ops run.
> - let dev: &device::Device = unsafe {
> device::Device::from_raw(parent_dev) };
> - // SAFETY: Devres teardown keeps the parent bound here.
> - unsafe { dev.as_bound() }
> + /// The caller must ensure the device is registered, i.e. that
> this is called within a fwctl
> + /// callback protected by `registration_lock`. The pointer cast
> from `Of<'static>` to `Of<'_>`
> + /// is sound because [`ForLt`] guarantees covariance.
> + unsafe fn registration_data_unchecked(&self) ->
> &<T::RegistrationData as ForLt>::Of<'_> {
> + // SAFETY: Caller guarantees the device is registered, so
> the pointer is valid.
> + // Lifetimes do not affect layout, so the cast is sound.
> + unsafe {
> (*self.registration_data.get()).cast::<_>().as_ref() } }
> }
>
> @@ -251,62 +247,98 @@ unsafe fn dec_ref(obj: NonNull<Self>) {
> }
> }
>
> -// SAFETY: `Device<T>` is refcounted by the fwctl core and may be
> released from -// any thread. The embedded driver data is `Send`.
> +// SAFETY: `Device<T>` is refcounted by the fwctl core and may be
> released from any thread. unsafe impl<T: Operations> Send for
> Device<T> {}
> -// SAFETY: Shared access to the embedded `fwctl_device` is protected
> by the -// fwctl core, and the embedded driver data is `Sync`.
> +// SAFETY: Shared access to the embedded `fwctl_device` is protected
> by the fwctl core. The +// `registration_data` field is only mutated
> before registration and after unregistration (both +//
> single-threaded with respect to callbacks). unsafe impl<T:
> Operations> Sync for Device<T> {}
> /// A registered fwctl device.
> ///
> -/// Must live inside a [`Devres`] to guarantee that
> [`fwctl_unregister`] runs -/// before the parent driver unbinds.
> `Devres` prevents the `Registration` -/// from being moved to a
> context that could outlive the parent device. +/// Carries the
> lifetime `'a` of the parent device to ensure that
> [`fwctl_unregister`] runs (via +/// [`Drop`]) before the parent
> driver unbinds. Owns the +///
> [`RegistrationData`](Operations::RegistrationData) which is
> accessible during callbacks via the +/// pointer stored in
> [`Device`]. /// -/// On drop the device is unregistered (all user
> contexts are closed and -/// `ops` is set to `NULL`) and the [`ARef`]
> is released. +/// On drop the device is unregistered (all user
> contexts are closed and `ops` is set to `NULL`) +/// and the
> registration data is dropped. /// /// [`fwctl_unregister`]:
> srctree/drivers/fwctl/main.c -pub struct Registration<T: Operations> {
> +pub struct Registration<'a, T: Operations> {
> dev: ARef<Device<T>>,
> + _reg_data: Pin<KBox<<T::RegistrationData as ForLt>::Of<'a>>>,
> }
>
> -impl<T: Operations> Registration<T> {
> - /// Register a previously allocated fwctl device.
> - pub fn new<'a>(
> - parent: &'a device::Device<device::Bound>,
> - dev: &'a Device<T>,
> - ) -> impl PinInit<Devres<Self>, Error> + 'a {
> - pin_init::pin_init_scope(move || {
> - // SAFETY: `dev` is a valid fwctl_device backed by an
> ARef.
> - let ret = unsafe {
> bindings::fwctl_register(dev.as_raw()) };
> - if ret != 0 {
> - return Err(Error::from_errno(ret));
> - }
> +impl<'a, T: Operations> Registration<'a, T>
> +where
> + for<'b> <T::RegistrationData as ForLt>::Of<'b>: Send + Sync,
> +{
> + /// Register a previously allocated fwctl device with the given
> registration data.
> + ///
> + /// The `reg_data` is owned by the registration and accessible
> during callbacks via
> + /// `Device::registration_data_unchecked()`.
> + ///
> + /// # Safety
> + ///
> + /// Callers must not `mem::forget()` the returned
> [`Registration`] or otherwise prevent its
> + /// [`Drop`] implementation from running, since
> `fwctl_unregister` must be called before the
> + /// parent device is unbound.
> + pub unsafe fn new(
> + _parent: &'a device::Device<device::Bound>,
> + dev: &Device<T>,
> + reg_data: impl PinInit<<T::RegistrationData as
> ForLt>::Of<'a>, Error>,
> + ) -> Result<Self> {
> + let reg_data: Pin<KBox<<T::RegistrationData as
> ForLt>::Of<'a>>> =
> + KBox::pin_init(reg_data, GFP_KERNEL)?;
> +
> + // Store the registration data pointer in the device before
> registration, so that it is
> + // visible once callbacks can be invoked.
> + //
> + // SAFETY: Lifetimes do not affect layout, so the pointer
> cast is sound.
> + let ptr: NonNull<<T::RegistrationData as
> ForLt>::Of<'static>> =
> + unsafe {
> mem::transmute(NonNull::from(Pin::get_ref(reg_data.as_ref()))) }; +
> + // SAFETY: No concurrent access; the device is not yet
> registered.
> + unsafe { *dev.registration_data.get() = ptr };
> +
> + // SAFETY: `dev` is a valid fwctl_device backed by an ARef.
> + let ret = unsafe { bindings::fwctl_register(dev.as_raw()) };
> + if ret != 0 {
> + // SAFETY: No concurrent readers; registration failed.
> + unsafe { *dev.registration_data.get() =
> NonNull::dangling() };
> + return Err(Error::from_errno(ret));
> + }
>
> - Ok(Devres::new(parent, Self { dev: dev.into() }))
> + Ok(Self {
> + dev: dev.into(),
> + _reg_data: reg_data,
> })
> }
> }
>
> -impl<T: Operations> Drop for Registration<T> {
> +impl<T: Operations> Drop for Registration<'_, T> {
> fn drop(&mut self) {
> - // SAFETY: `Registration` lives inside a `Devres`, which
> guarantees
> - // that drop runs while the parent device is still bound.
> + // SAFETY: The Registration lifetime guarantees that the
> parent device is still bound.
> + // `fwctl_unregister` takes the write lock, closes all user
> contexts, and sets ops=NULL.
> + // After it returns, no callbacks can be running or will run.
> unsafe { bindings::fwctl_unregister(self.dev.as_raw()) };
> - // ARef<Device<T>> is dropped after this, calling fwctl_put.
> +
> + // SAFETY: `fwctl_unregister` guarantees no concurrent
> readers.
> + unsafe { *self.dev.registration_data.get() =
> NonNull::dangling() }; +
> + // `self._reg_data` is dropped here — safe because no
> concurrent readers remain. }
> }
>
> -// SAFETY: `Registration` can be sent between threads; the underlying
> -// fwctl_device uses internal locking.
> -unsafe impl<T: Operations> Send for Registration<T> {}
> +// SAFETY: `Registration` can be sent between threads; the
> underlying fwctl_device uses internal +// locking.
> +unsafe impl<T: Operations> Send for Registration<'_, T> {}
>
> -// SAFETY: `Registration` provides no mutable access; the underlying
> -// fwctl_device is protected by internal locking.
> -unsafe impl<T: Operations> Sync for Registration<T> {}
> +// SAFETY: `Registration` provides no mutable access; the underlying
> fwctl_device is protected by +// internal locking.
> +unsafe impl<T: Operations> Sync for Registration<'_, T> {}
>
> /// Internal per-FD user context wrapping `struct fwctl_uctx` and
> `T`. ///
> @@ -376,7 +408,10 @@ impl<T: Operations> VTable<T> {
> // SAFETY: Rust fwctl devices use the offset-0 `Device<T>`
> layout. let device = unsafe { Device::<T>::from_raw(raw_fwctl) };
>
> - let initializer = T::open(device);
> + // SAFETY: open_uctx is called under registration_lock read;
> the device is registered.
> + let reg_data = unsafe { device.registration_data_unchecked()
> }; +
> + let initializer = T::open(device, reg_data);
>
> let uctx_offset = core::mem::offset_of!(UserCtx<T>, uctx);
> // SAFETY: `uctx_size` reserves space for the full
> `UserCtx<T>`. @@ -396,13 +431,17 @@ impl<T: Operations> VTable<T> {
> // SAFETY: fwctl keeps the owning device live for this
> callback. let device = unsafe { Device::<T>::from_raw((*uctx).fwctl)
> };
> + // SAFETY: close_uctx is called under registration_lock
> write (from fwctl_unregister) or
> + // under registration_lock read (from fwctl_fops_release);
> the device is registered.
> + let reg_data = unsafe { device.registration_data_unchecked()
> }; +
> // SAFETY: close is called for an opened Rust user context.
> let ctx = unsafe { UserCtx::<T>::from_raw_mut(uctx) };
>
> {
> // SAFETY: fwctl never moves an opened user context.
> let pinned = unsafe { Pin::new_unchecked(&mut ctx.uctx)
> };
> - T::close(pinned, device);
> + T::close(pinned, device, reg_data);
> }
>
> // SAFETY: close is the last callback before fwctl frees the
> allocation. @@ -421,10 +460,13 @@ impl<T: Operations> VTable<T> {
> let ctx = unsafe { UserCtx::<T>::from_raw(uctx) };
> let device = ctx.device();
>
> + // SAFETY: info is called under registration_lock read; the
> device is registered.
> + let reg_data = unsafe { device.registration_data_unchecked()
> }; +
> // SAFETY: fwctl never moves an opened user context.
> let pinned = unsafe { Pin::new_unchecked(&ctx.uctx) };
>
> - match T::info(pinned, device) {
> + match T::info(pinned, device, reg_data) {
> Ok(kvec) if kvec.is_empty() => {
> // SAFETY: `length` is a valid out-parameter.
> unsafe { *length = 0 };
> @@ -461,6 +503,9 @@ impl<T: Operations> VTable<T> {
> let ctx = unsafe { UserCtx::<T>::from_raw(uctx) };
> let device = ctx.device();
>
> + // SAFETY: fw_rpc is called under registration_lock read;
> the device is registered.
> + let reg_data = unsafe { device.registration_data_unchecked()
> }; +
> // SAFETY: fwctl passes a valid in/out buffer for this
> callback. let rpc_in_slice: &mut [u8] =
> unsafe { slice::from_raw_parts_mut(rpc_in.cast::<u8>(),
> in_len) }; @@ -468,7 +513,7 @@ impl<T: Operations> VTable<T> {
> // SAFETY: fwctl never moves an opened user context.
> let pinned = unsafe { Pin::new_unchecked(&ctx.uctx) };
>
> - match T::fw_rpc(pinned, device, scope, rpc_in_slice) {
> + match T::fw_rpc(pinned, device, reg_data, scope,
> rpc_in_slice) { Ok(FwRpcResponse::InPlace(len)) => {
> // SAFETY: `out_len` is valid.
> unsafe { *out_len = len };
>
> [5] nova-core diff:
>
> diff --git a/drivers/gpu/nova-core/driver.rs
> b/drivers/gpu/nova-core/driver.rs index 5738d4ac521b..34d595b655fc
> 100644 --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -3,6 +3,7 @@
> use kernel::{
> auxiliary,
> device::Core,
> + fwctl,
> pci,
> pci::{
> Class,
> @@ -15,7 +16,7 @@
> Atomic,
> Relaxed, //
> },
> - types::ForLt,
> + types::ForLt, //
> };
>
> use crate::gpu::Gpu;
> @@ -23,6 +24,34 @@
> /// Counter for generating unique auxiliary device IDs.
> static AUXILIARY_ID_COUNTER: Atomic<u32> = Atomic::new(0);
>
> +struct FwctlRegData<'a> {
> + _bar: Bar0<'a>,
> +}
> +
> +struct FwctlUctx;
> +
> +impl fwctl::Operations for FwctlUctx {
> + type RegistrationData = ForLt!(FwctlRegData<'_>);
> + const DEVICE_TYPE: fwctl::DeviceType = fwctl::DeviceType::Mlx5;
> +
> + fn open(
> + _device: &fwctl::Device<Self>,
> + _reg_data: &FwctlRegData<'_>,
> + ) -> impl PinInit<Self, Error> {
> + Ok(FwctlUctx)
> + }
> +
> + fn fw_rpc(
> + _this: core::pin::Pin<&Self>,
> + _device: &fwctl::Device<Self>,
> + _reg_data: &FwctlRegData<'_>,
> + _scope: fwctl::RpcScope,
> + _rpc_in: &mut [u8],
> + ) -> Result<fwctl::FwRpcResponse, Error> {
> + Err(ENOTSUPP)
> + }
> +}
> +
> #[pin_data]
> pub(crate) struct NovaCore<'bound> {
> #[pin]
> @@ -30,6 +59,7 @@ pub(crate) struct NovaCore<'bound> {
> bar: pci::Bar<'bound, BAR0_SIZE>,
> #[allow(clippy::type_complexity)]
> _reg: auxiliary::Registration<'bound, ForLt!(())>,
> + _fwctl_reg: fwctl::Registration<'bound, FwctlUctx>,
> }
>
> pub(crate) struct NovaCoreDriver;
> @@ -78,6 +108,8 @@ fn probe<'bound>(
> pdev.enable_device_mem()?;
> pdev.set_master();
>
> + let fwctl_dev =
> fwctl::Device::<FwctlUctx>::new(pdev.as_ref())?; +
> Ok(try_pin_init!(NovaCore {
> bar: pdev.iomap_region_sized::<BAR0_SIZE>(0,
> c"nova-core/bar0")?, // TODO: Use `&bar` self-referential pin-init
> syntax once available. @@ -95,6 +127,17 @@ fn probe<'bound>(
> crate::MODULE_NAME,
> (),
> )?,
> + // SAFETY: `_fwctl_reg` is dropped before `bar`
> (struct field drop order), and its
> + // drop calls `fwctl_unregister` before the parent
> device is unbound.
> + _fwctl_reg: unsafe {
> + fwctl::Registration::new(
> + pdev.as_ref(),
> + &fwctl_dev,
> + Ok(FwctlRegData {
> + _bar: &*core::ptr::from_ref(bar),
> + }),
> + )?
> + },
> }))
> })
> }
> diff --git a/drivers/gpu/nova-core/nova_core.rs
> b/drivers/gpu/nova-core/nova_core.rs index 735b8e17c6b6..d5f050b2b55e
> 100644 --- a/drivers/gpu/nova-core/nova_core.rs
> +++ b/drivers/gpu/nova-core/nova_core.rs
> @@ -74,6 +74,7 @@ fn init(module: &'static kernel::ThisModule) ->
> impl PinInit<Self, Error> { description: "Nova Core GPU driver",
> license: "GPL v2",
> firmware: [],
> + imports_ns: ["FWCTL"],
> }
>
> kernel::module_firmware!(firmware::ModInfoBuilder);
^ permalink raw reply
* Re: [PATCH v2] rust_binder: reject context manager self-transaction
From: Alice Ryhl @ 2026-06-25 5:52 UTC (permalink / raw)
To: Carlos Llamas
Cc: Keshav Verma, Greg Kroah-Hartman, Arve Hjønnevåg,
Todd Kjos, Christian Brauner, Miguel Ojeda, Boqun Feng, Gary Guo,
linux-kernel, rust-for-linux, stable
In-Reply-To: <ajx4bYtQRvBZp4M0@google.com>
On Thu, Jun 25, 2026 at 2:38 AM Carlos Llamas <cmllamas@google.com> wrote:
>
> On Tue, Jun 23, 2026 at 11:37:11AM +0000, Alice Ryhl wrote:
> > On Mon, Jun 22, 2026 at 08:28:01PM +0530, Keshav Verma wrote:
> > > Rust binder resolved handle 0 to the context manager node, but it does not
> > > reject the case where the caller owns the same node.
> > >
> > > The C binder driver rejects transactions from the context-manager process
> > > to handle 0 after resolving the target node. Match that behavior in Rust
> > > Binder by rejecting handle 0 transactions when the resolved context-manager
> > > node is owned by the calling process.
> > >
> > > This applies to both synchronous and oneway transactions because both paths
> > > resolve the target through Process::get_transaction_node().
> > >
> > > Cc: stable@kernel.org
> > > Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
> > > Signed-off-by: Keshav Verma <iganschel@gmail.com>
> > > ---
> > > Changes in v2:
> > > - Compare the underlying OS process task instead of Rust Binder `Process` object.
> >
> > I would prefer to compare the Binder Process object. Rejecting
> > transactions between different fds owned by the same process doesn't
> > really have any benefit and makes fuzz testing much harder.
> >
> > Alice
>
> Hey Alice,
>
> The restrictions were added in the C version in order to patch
> vulnerabilities associated with this "self-transaction" behavior.
> See: http://git.kernel.org/torvalds/c/4b836a1426cb
>
> I haven't really looked much into this, but do we even need this for the
> Rust version? Is this even fixing anything at all?
Even if there's no vulnerability, self-transactions are still very
weird and may introduce edge cases I can't think of. I would prefer to
reject them.
Alice
^ permalink raw reply
* Re: [PATCH v2] rust_binder: reject context manager self-transaction
From: Carlos Llamas @ 2026-06-25 0:38 UTC (permalink / raw)
To: Alice Ryhl
Cc: Keshav Verma, Greg Kroah-Hartman, Arve Hjønnevåg,
Todd Kjos, Christian Brauner, Miguel Ojeda, Boqun Feng, Gary Guo,
linux-kernel, rust-for-linux, stable
In-Reply-To: <ajpv5xkakp06ArMj@google.com>
On Tue, Jun 23, 2026 at 11:37:11AM +0000, Alice Ryhl wrote:
> On Mon, Jun 22, 2026 at 08:28:01PM +0530, Keshav Verma wrote:
> > Rust binder resolved handle 0 to the context manager node, but it does not
> > reject the case where the caller owns the same node.
> >
> > The C binder driver rejects transactions from the context-manager process
> > to handle 0 after resolving the target node. Match that behavior in Rust
> > Binder by rejecting handle 0 transactions when the resolved context-manager
> > node is owned by the calling process.
> >
> > This applies to both synchronous and oneway transactions because both paths
> > resolve the target through Process::get_transaction_node().
> >
> > Cc: stable@kernel.org
> > Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
> > Signed-off-by: Keshav Verma <iganschel@gmail.com>
> > ---
> > Changes in v2:
> > - Compare the underlying OS process task instead of Rust Binder `Process` object.
>
> I would prefer to compare the Binder Process object. Rejecting
> transactions between different fds owned by the same process doesn't
> really have any benefit and makes fuzz testing much harder.
>
> Alice
Hey Alice,
The restrictions were added in the C version in order to patch
vulnerabilities associated with this "self-transaction" behavior.
See: http://git.kernel.org/torvalds/c/4b836a1426cb
I haven't really looked much into this, but do we even need this for the
Rust version? Is this even fixing anything at all?
--
Carlos Llamas
^ permalink raw reply
* Re: [GIT PULL] Rust for v7.2 (addendum)
From: pr-tracker-bot @ 2026-06-24 22:16 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Linus Torvalds, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, rust-for-linux, linux-kernel
In-Reply-To: <20260624144713.585327-1-ojeda@kernel.org>
The pull request you sent on Wed, 24 Jun 2026 16:47:13 +0200:
> https://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux.git tags/rust-7.2-2
has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/ab9de95c9cf952332ab79453b4b5d1bfca8e514f
Thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/prtracker.html
^ permalink raw reply
* Re: [GIT PULL] Rust fixes for 7.2
From: pr-tracker-bot @ 2026-06-24 22:16 UTC (permalink / raw)
To: Miguel Ojeda
Cc: Linus Torvalds, Miguel Ojeda, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Daniel Almeida, Tamir Duberstein,
Alexandre Courbot, Onur Özkan, rust-for-linux, linux-kernel
In-Reply-To: <20260624144630.585128-1-ojeda@kernel.org>
The pull request you sent on Wed, 24 Jun 2026 16:46:30 +0200:
> https://git.kernel.org/pub/scm/linux/kernel/git/ojeda/linux.git tags/rust-fixes-7.2
has been merged into torvalds/linux.git:
https://git.kernel.org/torvalds/c/dcebfd2c1404d1c931e86ec5168cdc006d503909
Thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/prtracker.html
^ permalink raw reply
* Re: [PATCH v17 06/10] rust: rename `AlwaysRefCounted` to `RefCounted`.
From: Andreas Hindborg @ 2026-06-24 19:17 UTC (permalink / raw)
To: Onur Özkan
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Daniel Almeida, Viresh Kumar,
Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Boqun Feng, Uladzislau Rezki,
Lorenzo Stoakes, Vlastimil Babka, Liam R. Howlett, Igor Korotin,
Pavel Tikhomirov, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci, driver-core, Oliver Mangold, Viresh Kumar
In-Reply-To: <20260623175814.87191-1-work@onurozkan.dev>
Onur Özkan <work@onurozkan.dev> writes:
> On Thu, 04 Jun 2026 22:11:18 +0200
> Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
>> From: Oliver Mangold <oliver.mangold@pm.me>
>>
>> There are types where it may both be reference counted in some cases and
>> owned in others. In such cases, obtaining `ARef<T>` from `&T` would be
>> unsound as it allows creation of `ARef<T>` copy from `&Owned<T>`.
>>
>> Therefore, we split `AlwaysRefCounted` into `RefCounted` (which `ARef<T>`
>> would require) and a marker trait to indicate that the type is always
>> reference counted (and not `Ownable`) so the `&T` -> `ARef<T>` conversion
>> is possible.
>>
>> - Rename `AlwaysRefCounted` to `RefCounted`.
>> - Add a new unsafe trait `AlwaysRefCounted`.
>> - Implement the new trait `AlwaysRefCounted` for the newly renamed
>> `RefCounted` implementations. This leaves functionality of existing
>> implementers of `AlwaysRefCounted` intact.
>>
>> Suggested-by: Alice Ryhl <aliceryhl@google.com>
>> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
>> Signed-off-by: Oliver Mangold <oliver.mangold@pm.me>
>> [ Andreas: Updated commit message and rebase on rust-6.20-7.0 ]
>> Acked-by: Igor Korotin <igor.korotin.linux@gmail.com>
>> Acked-by: Danilo Krummrich <dakr@kernel.org>
>> Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
>> Reviewed-by: Gary Guo <gary@garyguo.net>
>> Co-developed-by: Andreas Hindborg <a.hindborg@kernel.org>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>> rust/kernel/auxiliary.rs | 7 +++++-
>> rust/kernel/block/mq/request.rs | 15 ++++++++-----
>> rust/kernel/cred.rs | 13 +++++++++--
>> rust/kernel/device.rs | 12 ++++++++--
>> rust/kernel/device/property.rs | 11 +++++++--
>> rust/kernel/drm/device.rs | 9 ++++++--
>> rust/kernel/drm/gem/mod.rs | 16 ++++++++++----
>> rust/kernel/fs/file.rs | 16 ++++++++++----
>> rust/kernel/i2c.rs | 13 ++++++++---
>> rust/kernel/mm.rs | 15 +++++++++----
>> rust/kernel/mm/mmput_async.rs | 9 ++++++--
>> rust/kernel/opp.rs | 10 ++++++---
>> rust/kernel/owned.rs | 2 +-
>> rust/kernel/pci.rs | 10 ++++++++-
>> rust/kernel/pid_namespace.rs | 12 ++++++++--
>> rust/kernel/platform.rs | 7 +++++-
>> rust/kernel/sync/aref.rs | 49 ++++++++++++++++++++++++++---------------
>> rust/kernel/task.rs | 13 +++++++++--
>> rust/kernel/types.rs | 3 ++-
>> rust/kernel/usb.rs | 17 +++++++++++---
>> 20 files changed, 195 insertions(+), 64 deletions(-)
>>
>> diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
>> index 93c0db1f6655..49f07740f657 100644
>> --- a/rust/kernel/auxiliary.rs
>> +++ b/rust/kernel/auxiliary.rs
>> @@ -19,6 +19,7 @@
>> to_result, //
>> },
>> prelude::*,
>> + sync::aref::{AlwaysRefCounted, RefCounted},
>
> This patch has multiple horizontal use statements around.
Thanks, I'll take another pass to fix that.
Best regards,
Andreas Hindborg
^ permalink raw reply
* Re: [PATCH v17 08/10] rust: aref: update formatting of use statements
From: Andreas Hindborg @ 2026-06-24 19:16 UTC (permalink / raw)
To: Onur Özkan
Cc: Miguel Ojeda, Gary Guo, Björn Roy Baron, Benno Lossin,
Alice Ryhl, Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Dave Ertman, Ira Weiny, Leon Romanovsky, Paul Moore, Serge Hallyn,
Rafael J. Wysocki, David Airlie, Simona Vetter, Alexander Viro,
Christian Brauner, Jan Kara, Daniel Almeida, Viresh Kumar,
Nishanth Menon, Stephen Boyd, Bjorn Helgaas,
Krzysztof Wilczyński, Boqun Feng, Uladzislau Rezki,
Lorenzo Stoakes, Vlastimil Babka, Liam R. Howlett, Igor Korotin,
Pavel Tikhomirov, linux-kernel, rust-for-linux, linux-block,
linux-security-module, dri-devel, linux-fsdevel, linux-mm,
linux-pm, linux-pci, driver-core
In-Reply-To: <20260623175531.85421-1-work@onurozkan.dev>
Onur Özkan <work@onurozkan.dev> writes:
> On Thu, 04 Jun 2026 22:11:20 +0200
> Andreas Hindborg <a.hindborg@kernel.org> wrote:
>
>> Update formatting if use statements in preparation for next commit.
>
> I guess you meant "formatting use statements"? Also, why not doing this in
> the next commit directly?
Because it is an unrelated change.
Best regards,
Andreas Hindborg
^ permalink raw reply
* Re: [PATCH v3 2/7] rust: types: introduce ForLt base trait for CovariantForLt
From: Danilo Krummrich @ 2026-06-24 18:06 UTC (permalink / raw)
To: Gary Guo
Cc: gregkh, rafael, ojeda, boqun, bjorn3_gh, lossin, a.hindborg,
aliceryhl, tmgross, acourbot, ecourtney, m.wilczynski,
david.m.ertman, ira.weiny, leon, daniel.almeida, bhelgaas,
kwilczynski, driver-core, linux-kernel, nova-gpu, dri-devel,
linux-pwm, rust-for-linux
In-Reply-To: <DJHDQ7X94BXR.2XYSWSK79USDB@garyguo.net>
On Wed Jun 24, 2026 at 5:20 PM CEST, Gary Guo wrote:
> This is still unsound, as I mentioned in the last version that the prover must
> be kept.
Heh, I think I just forgot to finish this up, good catch!
^ permalink raw reply
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