From 1a4736c3d8394f5e64557a41b4b2b8d6dcd04622 Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Wed, 23 Apr 2025 09:54:37 -0400 Subject: rust: types: add `ForeignOwnable::PointedTo` Allow implementors to specify the foreign pointer type; this exposes information about the pointed-to type such as its alignment. This requires the trait to be `unsafe` since it is now possible for implementors to break soundness by returning a misaligned pointer. Encoding the pointer type in the trait (and avoiding pointer casts) allows the compiler to check that implementors return the correct pointer type. This is preferable to directly encoding the alignment in the trait using a constant as the compiler would be unable to check it. Acked-by: Danilo Krummrich Signed-off-by: Tamir Duberstein Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250423-rust-xarray-bindings-v19-1-83cdcf11c114@gmail.com Signed-off-by: Andreas Hindborg --- rust/kernel/alloc/kbox.rs | 38 ++++++++++++++++++++------------------ rust/kernel/miscdevice.rs | 10 +++++----- rust/kernel/pci.rs | 2 +- rust/kernel/platform.rs | 2 +- rust/kernel/sync/arc.rs | 21 ++++++++++++--------- rust/kernel/types.rs | 46 +++++++++++++++++++++++++++++++--------------- 6 files changed, 70 insertions(+), 49 deletions(-) diff --git a/rust/kernel/alloc/kbox.rs b/rust/kernel/alloc/kbox.rs index b77d32f3a58b..6aa88b01e84d 100644 --- a/rust/kernel/alloc/kbox.rs +++ b/rust/kernel/alloc/kbox.rs @@ -360,68 +360,70 @@ where } } -impl ForeignOwnable for Box +// SAFETY: The `into_foreign` function returns a pointer that is well-aligned. +unsafe impl ForeignOwnable for Box where A: Allocator, { + type PointedTo = T; type Borrowed<'a> = &'a T; type BorrowedMut<'a> = &'a mut T; - fn into_foreign(self) -> *mut crate::ffi::c_void { - Box::into_raw(self).cast() + fn into_foreign(self) -> *mut Self::PointedTo { + Box::into_raw(self) } - unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self { + unsafe fn from_foreign(ptr: *mut Self::PointedTo) -> Self { // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous // call to `Self::into_foreign`. - unsafe { Box::from_raw(ptr.cast()) } + unsafe { Box::from_raw(ptr) } } - unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> &'a T { + unsafe fn borrow<'a>(ptr: *mut Self::PointedTo) -> &'a T { // SAFETY: The safety requirements of this method ensure that the object remains alive and // immutable for the duration of 'a. - unsafe { &*ptr.cast() } + unsafe { &*ptr } } - unsafe fn borrow_mut<'a>(ptr: *mut crate::ffi::c_void) -> &'a mut T { - let ptr = ptr.cast(); + unsafe fn borrow_mut<'a>(ptr: *mut Self::PointedTo) -> &'a mut T { // SAFETY: The safety requirements of this method ensure that the pointer is valid and that // nothing else will access the value for the duration of 'a. unsafe { &mut *ptr } } } -impl ForeignOwnable for Pin> +// SAFETY: The `into_foreign` function returns a pointer that is well-aligned. +unsafe impl ForeignOwnable for Pin> where A: Allocator, { + type PointedTo = T; type Borrowed<'a> = Pin<&'a T>; type BorrowedMut<'a> = Pin<&'a mut T>; - fn into_foreign(self) -> *mut crate::ffi::c_void { + fn into_foreign(self) -> *mut Self::PointedTo { // SAFETY: We are still treating the box as pinned. - Box::into_raw(unsafe { Pin::into_inner_unchecked(self) }).cast() + Box::into_raw(unsafe { Pin::into_inner_unchecked(self) }) } - unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self { + unsafe fn from_foreign(ptr: *mut Self::PointedTo) -> Self { // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous // call to `Self::into_foreign`. - unsafe { Pin::new_unchecked(Box::from_raw(ptr.cast())) } + unsafe { Pin::new_unchecked(Box::from_raw(ptr)) } } - unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> Pin<&'a T> { + unsafe fn borrow<'a>(ptr: *mut Self::PointedTo) -> Pin<&'a T> { // SAFETY: The safety requirements for this function ensure that the object is still alive, // so it is safe to dereference the raw pointer. // The safety requirements of `from_foreign` also ensure that the object remains alive for // the lifetime of the returned value. - let r = unsafe { &*ptr.cast() }; + let r = unsafe { &*ptr }; // SAFETY: This pointer originates from a `Pin>`. unsafe { Pin::new_unchecked(r) } } - unsafe fn borrow_mut<'a>(ptr: *mut crate::ffi::c_void) -> Pin<&'a mut T> { - let ptr = ptr.cast(); + unsafe fn borrow_mut<'a>(ptr: *mut Self::PointedTo) -> Pin<&'a mut T> { // SAFETY: The safety requirements for this function ensure that the object is still alive, // so it is safe to dereference the raw pointer. // The safety requirements of `from_foreign` also ensure that the object remains alive for diff --git a/rust/kernel/miscdevice.rs b/rust/kernel/miscdevice.rs index fa9ecc42602a..b4c5f74de23d 100644 --- a/rust/kernel/miscdevice.rs +++ b/rust/kernel/miscdevice.rs @@ -200,7 +200,7 @@ impl MiscdeviceVTable { // type. // // SAFETY: The open call of a file can access the private data. - unsafe { (*raw_file).private_data = ptr.into_foreign() }; + unsafe { (*raw_file).private_data = ptr.into_foreign().cast() }; 0 } @@ -211,7 +211,7 @@ impl MiscdeviceVTable { /// must be associated with a `MiscDeviceRegistration`. unsafe extern "C" fn release(_inode: *mut bindings::inode, file: *mut bindings::file) -> c_int { // SAFETY: The release call of a file owns the private data. - let private = unsafe { (*file).private_data }; + let private = unsafe { (*file).private_data }.cast(); // SAFETY: The release call of a file owns the private data. let ptr = unsafe { ::from_foreign(private) }; @@ -228,7 +228,7 @@ impl MiscdeviceVTable { /// `file` must be a valid file that is associated with a `MiscDeviceRegistration`. unsafe extern "C" fn ioctl(file: *mut bindings::file, cmd: c_uint, arg: c_ulong) -> c_long { // SAFETY: The ioctl call of a file can access the private data. - let private = unsafe { (*file).private_data }; + let private = unsafe { (*file).private_data }.cast(); // SAFETY: Ioctl calls can borrow the private data of the file. let device = unsafe { ::borrow(private) }; @@ -253,7 +253,7 @@ impl MiscdeviceVTable { arg: c_ulong, ) -> c_long { // SAFETY: The compat ioctl call of a file can access the private data. - let private = unsafe { (*file).private_data }; + let private = unsafe { (*file).private_data }.cast(); // SAFETY: Ioctl calls can borrow the private data of the file. let device = unsafe { ::borrow(private) }; @@ -274,7 +274,7 @@ impl MiscdeviceVTable { /// - `seq_file` must be a valid `struct seq_file` that we can write to. unsafe extern "C" fn show_fdinfo(seq_file: *mut bindings::seq_file, file: *mut bindings::file) { // SAFETY: The release call of a file owns the private data. - let private = unsafe { (*file).private_data }; + let private = unsafe { (*file).private_data }.cast(); // SAFETY: Ioctl calls can borrow the private data of the file. let device = unsafe { ::borrow(private) }; // SAFETY: diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs index c97d6d470b28..3aeb1250c27f 100644 --- a/rust/kernel/pci.rs +++ b/rust/kernel/pci.rs @@ -89,7 +89,7 @@ impl Adapter { extern "C" fn remove_callback(pdev: *mut bindings::pci_dev) { // SAFETY: The PCI bus only ever calls the remove callback with a valid pointer to a // `struct pci_dev`. - let ptr = unsafe { bindings::pci_get_drvdata(pdev) }; + let ptr = unsafe { bindings::pci_get_drvdata(pdev) }.cast(); // SAFETY: `remove_callback` is only ever called after a successful call to // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs index 4917cb34e2fe..fd4a494f30e8 100644 --- a/rust/kernel/platform.rs +++ b/rust/kernel/platform.rs @@ -80,7 +80,7 @@ impl Adapter { extern "C" fn remove_callback(pdev: *mut bindings::platform_device) { // SAFETY: `pdev` is a valid pointer to a `struct platform_device`. - let ptr = unsafe { bindings::platform_get_drvdata(pdev) }; + let ptr = unsafe { bindings::platform_get_drvdata(pdev) }.cast(); // SAFETY: `remove_callback` is only ever called after a successful call to // `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs index 8484c814609a..a42c164e577a 100644 --- a/rust/kernel/sync/arc.rs +++ b/rust/kernel/sync/arc.rs @@ -140,9 +140,10 @@ pub struct Arc { _p: PhantomData>, } +#[doc(hidden)] #[pin_data] #[repr(C)] -struct ArcInner { +pub struct ArcInner { refcount: Opaque, data: T, } @@ -371,18 +372,20 @@ impl Arc { } } -impl ForeignOwnable for Arc { +// SAFETY: The `into_foreign` function returns a pointer that is well-aligned. +unsafe impl ForeignOwnable for Arc { + type PointedTo = ArcInner; type Borrowed<'a> = ArcBorrow<'a, T>; type BorrowedMut<'a> = Self::Borrowed<'a>; - fn into_foreign(self) -> *mut crate::ffi::c_void { - ManuallyDrop::new(self).ptr.as_ptr().cast() + fn into_foreign(self) -> *mut Self::PointedTo { + ManuallyDrop::new(self).ptr.as_ptr() } - unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self { + unsafe fn from_foreign(ptr: *mut Self::PointedTo) -> Self { // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous // call to `Self::into_foreign`. - let inner = unsafe { NonNull::new_unchecked(ptr.cast::>()) }; + let inner = unsafe { NonNull::new_unchecked(ptr) }; // SAFETY: By the safety requirement of this function, we know that `ptr` came from // a previous call to `Arc::into_foreign`, which guarantees that `ptr` is valid and @@ -390,17 +393,17 @@ impl ForeignOwnable for Arc { unsafe { Self::from_inner(inner) } } - unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> ArcBorrow<'a, T> { + unsafe fn borrow<'a>(ptr: *mut Self::PointedTo) -> ArcBorrow<'a, T> { // SAFETY: The safety requirements of this function ensure that `ptr` comes from a previous // call to `Self::into_foreign`. - let inner = unsafe { NonNull::new_unchecked(ptr.cast::>()) }; + let inner = unsafe { NonNull::new_unchecked(ptr) }; // SAFETY: The safety requirements of `from_foreign` ensure that the object remains alive // for the lifetime of the returned value. unsafe { ArcBorrow::new(inner) } } - unsafe fn borrow_mut<'a>(ptr: *mut crate::ffi::c_void) -> ArcBorrow<'a, T> { + unsafe fn borrow_mut<'a>(ptr: *mut Self::PointedTo) -> ArcBorrow<'a, T> { // SAFETY: The safety requirements for `borrow_mut` are a superset of the safety // requirements for `borrow`. unsafe { Self::borrow(ptr) } diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs index 9d0471afc964..86562e738eac 100644 --- a/rust/kernel/types.rs +++ b/rust/kernel/types.rs @@ -18,7 +18,19 @@ use pin_init::{PinInit, Zeroable}; /// /// This trait is meant to be used in cases when Rust objects are stored in C objects and /// eventually "freed" back to Rust. -pub trait ForeignOwnable: Sized { +/// +/// # Safety +/// +/// Implementers must ensure that [`into_foreign`] returns a pointer which meets the alignment +/// requirements of [`PointedTo`]. +/// +/// [`into_foreign`]: Self::into_foreign +/// [`PointedTo`]: Self::PointedTo +pub unsafe trait ForeignOwnable: Sized { + /// Type used when the value is foreign-owned. In practical terms only defines the alignment of + /// the pointer. + type PointedTo; + /// Type used to immutably borrow a value that is currently foreign-owned. type Borrowed<'a>; @@ -27,16 +39,18 @@ pub trait ForeignOwnable: Sized { /// Converts a Rust-owned object to a foreign-owned one. /// - /// The foreign representation is a pointer to void. There are no guarantees for this pointer. - /// For example, it might be invalid, dangling or pointing to uninitialized memory. Using it in - /// any way except for [`from_foreign`], [`try_from_foreign`], [`borrow`], or [`borrow_mut`] can - /// result in undefined behavior. + /// # Guarantees + /// + /// The return value is guaranteed to be well-aligned, but there are no other guarantees for + /// this pointer. For example, it might be null, dangling, or point to uninitialized memory. + /// Using it in any way except for [`ForeignOwnable::from_foreign`], [`ForeignOwnable::borrow`], + /// [`ForeignOwnable::try_from_foreign`] can result in undefined behavior. /// /// [`from_foreign`]: Self::from_foreign /// [`try_from_foreign`]: Self::try_from_foreign /// [`borrow`]: Self::borrow /// [`borrow_mut`]: Self::borrow_mut - fn into_foreign(self) -> *mut crate::ffi::c_void; + fn into_foreign(self) -> *mut Self::PointedTo; /// Converts a foreign-owned object back to a Rust-owned one. /// @@ -46,7 +60,7 @@ pub trait ForeignOwnable: Sized { /// must not be passed to `from_foreign` more than once. /// /// [`into_foreign`]: Self::into_foreign - unsafe fn from_foreign(ptr: *mut crate::ffi::c_void) -> Self; + unsafe fn from_foreign(ptr: *mut Self::PointedTo) -> Self; /// Tries to convert a foreign-owned object back to a Rust-owned one. /// @@ -58,7 +72,7 @@ pub trait ForeignOwnable: Sized { /// `ptr` must either be null or satisfy the safety requirements for [`from_foreign`]. /// /// [`from_foreign`]: Self::from_foreign - unsafe fn try_from_foreign(ptr: *mut crate::ffi::c_void) -> Option { + unsafe fn try_from_foreign(ptr: *mut Self::PointedTo) -> Option { if ptr.is_null() { None } else { @@ -81,7 +95,7 @@ pub trait ForeignOwnable: Sized { /// /// [`into_foreign`]: Self::into_foreign /// [`from_foreign`]: Self::from_foreign - unsafe fn borrow<'a>(ptr: *mut crate::ffi::c_void) -> Self::Borrowed<'a>; + unsafe fn borrow<'a>(ptr: *mut Self::PointedTo) -> Self::Borrowed<'a>; /// Borrows a foreign-owned object mutably. /// @@ -109,21 +123,23 @@ pub trait ForeignOwnable: Sized { /// [`from_foreign`]: Self::from_foreign /// [`borrow`]: Self::borrow /// [`Arc`]: crate::sync::Arc - unsafe fn borrow_mut<'a>(ptr: *mut crate::ffi::c_void) -> Self::BorrowedMut<'a>; + unsafe fn borrow_mut<'a>(ptr: *mut Self::PointedTo) -> Self::BorrowedMut<'a>; } -impl ForeignOwnable for () { +// SAFETY: The `into_foreign` function returns a pointer that is dangling, but well-aligned. +unsafe impl ForeignOwnable for () { + type PointedTo = (); type Borrowed<'a> = (); type BorrowedMut<'a> = (); - fn into_foreign(self) -> *mut crate::ffi::c_void { + fn into_foreign(self) -> *mut Self::PointedTo { core::ptr::NonNull::dangling().as_ptr() } - unsafe fn from_foreign(_: *mut crate::ffi::c_void) -> Self {} + unsafe fn from_foreign(_: *mut Self::PointedTo) -> Self {} - unsafe fn borrow<'a>(_: *mut crate::ffi::c_void) -> Self::Borrowed<'a> {} - unsafe fn borrow_mut<'a>(_: *mut crate::ffi::c_void) -> Self::BorrowedMut<'a> {} + unsafe fn borrow<'a>(_: *mut Self::PointedTo) -> Self::Borrowed<'a> {} + unsafe fn borrow_mut<'a>(_: *mut Self::PointedTo) -> Self::BorrowedMut<'a> {} } /// Runs a cleanup function/closure when dropped. -- cgit v1.2.3 From 210b81578efbe5c5e7748e50d313e1a90b03df55 Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Wed, 23 Apr 2025 09:54:38 -0400 Subject: rust: xarray: Add an abstraction for XArray MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit `XArray` is an efficient sparse array of pointers. Add a Rust abstraction for this type. This implementation bounds the element type on `ForeignOwnable` and requires explicit locking for all operations. Future work may leverage RCU to enable lockless operation. Inspired-by: Maíra Canal Inspired-by: Asahi Lina Reviewed-by: Andreas Hindborg Reviewed-by: Alice Ryhl Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20250423-rust-xarray-bindings-v19-2-83cdcf11c114@gmail.com Signed-off-by: Andreas Hindborg --- rust/bindings/bindings_helper.h | 6 + rust/helpers/helpers.c | 1 + rust/helpers/xarray.c | 28 ++++ rust/kernel/lib.rs | 1 + rust/kernel/xarray.rs | 275 ++++++++++++++++++++++++++++++++++++++++ 5 files changed, 311 insertions(+) create mode 100644 rust/helpers/xarray.c create mode 100644 rust/kernel/xarray.rs diff --git a/rust/bindings/bindings_helper.h b/rust/bindings/bindings_helper.h index ab37e1d35c70..e0bcd130b494 100644 --- a/rust/bindings/bindings_helper.h +++ b/rust/bindings/bindings_helper.h @@ -37,6 +37,7 @@ #include #include #include +#include #include #if defined(CONFIG_DRM_PANIC_SCREEN_QR_CODE) @@ -55,3 +56,8 @@ const gfp_t RUST_CONST_HELPER___GFP_ZERO = __GFP_ZERO; const gfp_t RUST_CONST_HELPER___GFP_HIGHMEM = ___GFP_HIGHMEM; const gfp_t RUST_CONST_HELPER___GFP_NOWARN = ___GFP_NOWARN; const blk_features_t RUST_CONST_HELPER_BLK_FEAT_ROTATIONAL = BLK_FEAT_ROTATIONAL; + +const xa_mark_t RUST_CONST_HELPER_XA_PRESENT = XA_PRESENT; + +const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC = XA_FLAGS_ALLOC; +const gfp_t RUST_CONST_HELPER_XA_FLAGS_ALLOC1 = XA_FLAGS_ALLOC1; diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c index 1e7c84df7252..80785b1e7a63 100644 --- a/rust/helpers/helpers.c +++ b/rust/helpers/helpers.c @@ -38,3 +38,4 @@ #include "vmalloc.c" #include "wait.c" #include "workqueue.c" +#include "xarray.c" diff --git a/rust/helpers/xarray.c b/rust/helpers/xarray.c new file mode 100644 index 000000000000..60b299f11451 --- /dev/null +++ b/rust/helpers/xarray.c @@ -0,0 +1,28 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include + +int rust_helper_xa_err(void *entry) +{ + return xa_err(entry); +} + +void rust_helper_xa_init_flags(struct xarray *xa, gfp_t flags) +{ + return xa_init_flags(xa, flags); +} + +int rust_helper_xa_trylock(struct xarray *xa) +{ + return xa_trylock(xa); +} + +void rust_helper_xa_lock(struct xarray *xa) +{ + return xa_lock(xa); +} + +void rust_helper_xa_unlock(struct xarray *xa) +{ + return xa_unlock(xa); +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index de07aadd1ff5..715fab6b1345 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -88,6 +88,7 @@ pub mod transmute; pub mod types; pub mod uaccess; pub mod workqueue; +pub mod xarray; #[doc(hidden)] pub use bindings; diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs new file mode 100644 index 000000000000..75719e7bb491 --- /dev/null +++ b/rust/kernel/xarray.rs @@ -0,0 +1,275 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! XArray abstraction. +//! +//! C header: [`include/linux/xarray.h`](srctree/include/linux/xarray.h) + +use crate::{ + alloc, bindings, build_assert, + error::{Error, Result}, + types::{ForeignOwnable, NotThreadSafe, Opaque}, +}; +use core::{iter, marker::PhantomData, mem, pin::Pin, ptr::NonNull}; +use pin_init::{pin_data, pin_init, pinned_drop, PinInit}; + +/// An array which efficiently maps sparse integer indices to owned objects. +/// +/// This is similar to a [`crate::alloc::kvec::Vec>`], but more efficient when there are +/// holes in the index space, and can be efficiently grown. +/// +/// # Invariants +/// +/// `self.xa` is always an initialized and valid [`bindings::xarray`] whose entries are either +/// `XA_ZERO_ENTRY` or came from `T::into_foreign`. +/// +/// # Examples +/// +/// ```rust +/// use kernel::alloc::KBox; +/// use kernel::xarray::{AllocKind, XArray}; +/// +/// let xa = KBox::pin_init(XArray::new(AllocKind::Alloc1), GFP_KERNEL)?; +/// +/// let dead = KBox::new(0xdead, GFP_KERNEL)?; +/// let beef = KBox::new(0xbeef, GFP_KERNEL)?; +/// +/// let mut guard = xa.lock(); +/// +/// assert_eq!(guard.get(0), None); +/// +/// assert_eq!(guard.store(0, dead, GFP_KERNEL)?.as_deref(), None); +/// assert_eq!(guard.get(0).copied(), Some(0xdead)); +/// +/// *guard.get_mut(0).unwrap() = 0xffff; +/// assert_eq!(guard.get(0).copied(), Some(0xffff)); +/// +/// assert_eq!(guard.store(0, beef, GFP_KERNEL)?.as_deref().copied(), Some(0xffff)); +/// assert_eq!(guard.get(0).copied(), Some(0xbeef)); +/// +/// guard.remove(0); +/// assert_eq!(guard.get(0), None); +/// +/// # Ok::<(), Error>(()) +/// ``` +#[pin_data(PinnedDrop)] +pub struct XArray { + #[pin] + xa: Opaque, + _p: PhantomData, +} + +#[pinned_drop] +impl PinnedDrop for XArray { + fn drop(self: Pin<&mut Self>) { + self.iter().for_each(|ptr| { + let ptr = ptr.as_ptr(); + // SAFETY: `ptr` came from `T::into_foreign`. + // + // INVARIANT: we own the only reference to the array which is being dropped so the + // broken invariant is not observable on function exit. + drop(unsafe { T::from_foreign(ptr) }) + }); + + // SAFETY: `self.xa` is always valid by the type invariant. + unsafe { bindings::xa_destroy(self.xa.get()) }; + } +} + +/// Flags passed to [`XArray::new`] to configure the array's allocation tracking behavior. +pub enum AllocKind { + /// Consider the first element to be at index 0. + Alloc, + /// Consider the first element to be at index 1. + Alloc1, +} + +impl XArray { + /// Creates a new initializer for this type. + pub fn new(kind: AllocKind) -> impl PinInit { + let flags = match kind { + AllocKind::Alloc => bindings::XA_FLAGS_ALLOC, + AllocKind::Alloc1 => bindings::XA_FLAGS_ALLOC1, + }; + pin_init!(Self { + // SAFETY: `xa` is valid while the closure is called. + // + // INVARIANT: `xa` is initialized here to an empty, valid [`bindings::xarray`]. + xa <- Opaque::ffi_init(|xa| unsafe { + bindings::xa_init_flags(xa, flags) + }), + _p: PhantomData, + }) + } + + fn iter(&self) -> impl Iterator> + '_ { + let mut index = 0; + + // SAFETY: `self.xa` is always valid by the type invariant. + iter::once(unsafe { + bindings::xa_find(self.xa.get(), &mut index, usize::MAX, bindings::XA_PRESENT) + }) + .chain(iter::from_fn(move || { + // SAFETY: `self.xa` is always valid by the type invariant. + Some(unsafe { + bindings::xa_find_after(self.xa.get(), &mut index, usize::MAX, bindings::XA_PRESENT) + }) + })) + .map_while(|ptr| NonNull::new(ptr.cast())) + } + + /// Attempts to lock the [`XArray`] for exclusive access. + pub fn try_lock(&self) -> Option> { + // SAFETY: `self.xa` is always valid by the type invariant. + if (unsafe { bindings::xa_trylock(self.xa.get()) } != 0) { + Some(Guard { + xa: self, + _not_send: NotThreadSafe, + }) + } else { + None + } + } + + /// Locks the [`XArray`] for exclusive access. + pub fn lock(&self) -> Guard<'_, T> { + // SAFETY: `self.xa` is always valid by the type invariant. + unsafe { bindings::xa_lock(self.xa.get()) }; + + Guard { + xa: self, + _not_send: NotThreadSafe, + } + } +} + +/// A lock guard. +/// +/// The lock is unlocked when the guard goes out of scope. +#[must_use = "the lock unlocks immediately when the guard is unused"] +pub struct Guard<'a, T: ForeignOwnable> { + xa: &'a XArray, + _not_send: NotThreadSafe, +} + +impl Drop for Guard<'_, T> { + fn drop(&mut self) { + // SAFETY: + // - `self.xa.xa` is always valid by the type invariant. + // - The caller holds the lock, so it is safe to unlock it. + unsafe { bindings::xa_unlock(self.xa.xa.get()) }; + } +} + +/// The error returned by [`store`](Guard::store). +/// +/// Contains the underlying error and the value that was not stored. +pub struct StoreError { + /// The error that occurred. + pub error: Error, + /// The value that was not stored. + pub value: T, +} + +impl From> for Error { + fn from(value: StoreError) -> Self { + value.error + } +} + +impl<'a, T: ForeignOwnable> Guard<'a, T> { + fn load(&self, index: usize, f: F) -> Option + where + F: FnOnce(NonNull) -> U, + { + // SAFETY: `self.xa.xa` is always valid by the type invariant. + let ptr = unsafe { bindings::xa_load(self.xa.xa.get(), index) }; + let ptr = NonNull::new(ptr.cast())?; + Some(f(ptr)) + } + + /// Provides a reference to the element at the given index. + pub fn get(&self, index: usize) -> Option> { + self.load(index, |ptr| { + // SAFETY: `ptr` came from `T::into_foreign`. + unsafe { T::borrow(ptr.as_ptr()) } + }) + } + + /// Provides a mutable reference to the element at the given index. + pub fn get_mut(&mut self, index: usize) -> Option> { + self.load(index, |ptr| { + // SAFETY: `ptr` came from `T::into_foreign`. + unsafe { T::borrow_mut(ptr.as_ptr()) } + }) + } + + /// Removes and returns the element at the given index. + pub fn remove(&mut self, index: usize) -> Option { + // SAFETY: + // - `self.xa.xa` is always valid by the type invariant. + // - The caller holds the lock. + let ptr = unsafe { bindings::__xa_erase(self.xa.xa.get(), index) }.cast(); + // SAFETY: + // - `ptr` is either NULL or came from `T::into_foreign`. + // - `&mut self` guarantees that the lifetimes of [`T::Borrowed`] and [`T::BorrowedMut`] + // borrowed from `self` have ended. + unsafe { T::try_from_foreign(ptr) } + } + + /// Stores an element at the given index. + /// + /// May drop the lock if needed to allocate memory, and then reacquire it afterwards. + /// + /// On success, returns the element which was previously at the given index. + /// + /// On failure, returns the element which was attempted to be stored. + pub fn store( + &mut self, + index: usize, + value: T, + gfp: alloc::Flags, + ) -> Result, StoreError> { + build_assert!( + mem::align_of::() >= 4, + "pointers stored in XArray must be 4-byte aligned" + ); + let new = value.into_foreign(); + + let old = { + let new = new.cast(); + // SAFETY: + // - `self.xa.xa` is always valid by the type invariant. + // - The caller holds the lock. + // + // INVARIANT: `new` came from `T::into_foreign`. + unsafe { bindings::__xa_store(self.xa.xa.get(), index, new, gfp.as_raw()) } + }; + + // SAFETY: `__xa_store` returns the old entry at this index on success or `xa_err` if an + // error happened. + let errno = unsafe { bindings::xa_err(old) }; + if errno != 0 { + // SAFETY: `new` came from `T::into_foreign` and `__xa_store` does not take + // ownership of the value on error. + let value = unsafe { T::from_foreign(new) }; + Err(StoreError { + value, + error: Error::from_errno(errno), + }) + } else { + let old = old.cast(); + // SAFETY: `ptr` is either NULL or came from `T::into_foreign`. + // + // NB: `XA_ZERO_ENTRY` is never returned by functions belonging to the Normal XArray + // API; such entries present as `NULL`. + Ok(unsafe { T::try_from_foreign(old) }) + } + } +} + +// SAFETY: `XArray` has no shared mutable state so it is `Send` iff `T` is `Send`. +unsafe impl Send for XArray {} + +// SAFETY: `XArray` serialises the interior mutability it provides so it is `Sync` iff `T` is +// `Send`. +unsafe impl Sync for XArray {} -- cgit v1.2.3 From fa616196fbea12462107774fb6a1908c95f71cf0 Mon Sep 17 00:00:00 2001 From: Tamir Duberstein Date: Wed, 23 Apr 2025 09:54:39 -0400 Subject: MAINTAINERS: add entry for Rust XArray API Add an entry for the Rust xarray abstractions. Acked-by: Andreas Hindborg Signed-off-by: Tamir Duberstein Link: https://lore.kernel.org/r/20250423-rust-xarray-bindings-v19-3-83cdcf11c114@gmail.com [ Changed T: entry branch to `xarray-rust` - Andreas ] Signed-off-by: Andreas Hindborg --- MAINTAINERS | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/MAINTAINERS b/MAINTAINERS index fa1e04e87d1d..871721367c45 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -26310,6 +26310,17 @@ F: lib/test_xarray.c F: lib/xarray.c F: tools/testing/radix-tree +XARRAY API [RUST] +M: Tamir Duberstein +M: Andreas Hindborg +L: rust-for-linux@vger.kernel.org +S: Supported +W: https://rust-for-linux.com +B: https://github.com/Rust-for-Linux/linux/issues +C: https://rust-for-linux.zulipchat.com +T: git https://github.com/Rust-for-Linux/linux.git xarray-next +F: rust/kernel/xarray.rs + XBOX DVD IR REMOTE M: Benjamin Valentin S: Maintained -- cgit v1.2.3