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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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//! Rust interface for C doubly circular intrusive linked lists.//!//! This module provides Rust abstractions for iterating over C `list_head`-based//! linked lists. It should only be used for cases where C and Rust code share//! direct access to the same linked list through a C interop interface.//!//! Note: This *must not* be used by Rust components that just need a linked list//! primitive. Use [`kernel::list::List`] instead.//!//! # Examples//!//! ```//! use kernel::{//! bindings,//! interop::list::clist_create,//! types::Opaque,//! };//! # // Create test list with values (0, 10, 20) - normally done by C code but it is//! # // emulated here for doctests using the C bindings.//! # use core::mem::MaybeUninit;//! #//! # /// C struct with embedded `list_head` (typically will be allocated by C code).//! # #[repr(C)]//! # pub struct SampleItemC {//! # pub value: i32,//! # pub link: bindings::list_head,//! # }//! #//! # let mut head = MaybeUninit::<bindings::list_head>::uninit();//! #//! # let head = head.as_mut_ptr();//! # // SAFETY: `head` and all the items are test objects allocated in this scope.//! # unsafe { bindings::INIT_LIST_HEAD(head) };//! #//! # let mut items = [//! # MaybeUninit::<SampleItemC>::uninit(),//! # MaybeUninit::<SampleItemC>::uninit(),//! # MaybeUninit::<SampleItemC>::uninit(),//! # ];//! #//! # for (i, item) in items.iter_mut().enumerate() {//! # let ptr = item.as_mut_ptr();//! # // SAFETY: `ptr` points to a valid `MaybeUninit<SampleItemC>`.//! # unsafe { (*ptr).value = i as i32 * 10 };//! # // SAFETY: `&raw mut` creates a pointer valid for `INIT_LIST_HEAD`.//! # unsafe { bindings::INIT_LIST_HEAD(&raw mut (*ptr).link) };//! # // SAFETY: `link` was just initialized and `head` is a valid list head.//! # unsafe { bindings::list_add_tail(&mut (*ptr).link, head) };//! # }//!//! /// Rust wrapper for the C struct.//! /////! /// The list item struct in this example is defined in C code as://! /////! /// ```c//! /// struct SampleItemC {//! /// int value;//! /// struct list_head link;//! /// };//! /// ```//! #[repr(transparent)]//! pub struct Item(Opaque<SampleItemC>);//!//! impl Item {//! pub fn value(&self) -> i32 {//! // SAFETY: `Item` has the same layout as `SampleItemC`.//! unsafe { (*self.0.get()).value }//! }//! }//!//! // Create typed [`CList`] from sentinel head.//! // SAFETY: `head` is valid and initialized, items are `SampleItemC` with//! // embedded `link` field, and `Item` is `#[repr(transparent)]` over `SampleItemC`.//! let list = unsafe { clist_create!(head, Item, SampleItemC, link) };//!//! // Iterate directly over typed items.//! let mut found_0 = false;//! let mut found_10 = false;//! let mut found_20 = false;//!//! for item in list.iter() {//! let val = item.value();//! if val == 0 { found_0 = true; }//! if val == 10 { found_10 = true; }//! if val == 20 { found_20 = true; }//! }//!//! assert!(found_0 && found_10 && found_20);//! ```
use core::{ iter::FusedIterator, marker::PhantomData, //};
use crate::{ bindings, types::Opaque, //};
use pin_init::{ pin_data, pin_init, PinInit, //};
/// FFI wrapper for a C `list_head` object used in intrusive linked lists.////// # Invariants////// - The underlying `list_head` is initialized with valid non-`NULL` `next`/`prev` pointers.#[pin_data]#[repr(transparent)]pub struct CListHead { #[pin] inner: Opaque<bindings::list_head>,}
impl CListHead { /// Create a `&CListHead` reference from a raw `list_head` pointer. /// /// # Safety /// /// - `ptr` must be a valid pointer to an initialized `list_head` (e.g. via /// `INIT_LIST_HEAD()`), with valid non-`NULL` `next`/`prev` pointers. /// - `ptr` must remain valid for the lifetime `'a`. /// - The list and all linked `list_head` nodes must not be modified from /// anywhere for the lifetime `'a`, unless done so via any [`CListHead`] APIs. #[inline] pub unsafe fn from_raw<'a>(ptr: *mut bindings::list_head) -> &'a Self { // SAFETY: // - `CListHead` has the same layout as `list_head`. // - `ptr` is valid and unmodified for `'a` per caller guarantees. unsafe { &*ptr.cast() } }
/// Get the raw `list_head` pointer. #[inline] pub fn as_raw(&self) -> *mut bindings::list_head { self.inner.get() }
/// Get the next [`CListHead`] in the list. #[inline] pub fn next(&self) -> &Self { let raw = self.as_raw(); // SAFETY: // - `self.as_raw()` is valid and initialized per type invariants. // - The `next` pointer is valid and non-`NULL` per type invariants // (initialized via `INIT_LIST_HEAD()` or equivalent). unsafe { Self::from_raw((*raw).next) } }
/// Check if this node is linked in a list (not isolated). #[inline] pub fn is_linked(&self) -> bool { let raw = self.as_raw(); // SAFETY: `self.as_raw()` is valid per type invariants. unsafe { (*raw).next != raw && (*raw).prev != raw } }
/// Returns a pin-initializer for the list head. pub fn new() -> impl PinInit<Self> { pin_init!(Self { // SAFETY: `INIT_LIST_HEAD` initializes `slot` to a valid empty list. inner <- Opaque::ffi_init(|slot| unsafe { bindings::INIT_LIST_HEAD(slot) }), }) }}
// SAFETY: `list_head` contains no thread-bound state; it only holds// `next`/`prev` pointers.unsafe impl Send for CListHead {}
// SAFETY: `CListHead` can be shared among threads as modifications are// not allowed at the moment.unsafe impl Sync for CListHead {}
impl PartialEq for CListHead { #[inline] fn eq(&self, other: &Self) -> bool { core::ptr::eq(self, other) }}
impl Eq for CListHead {}
/// Low-level iterator over `list_head` nodes.////// An iterator used to iterate over a C intrusive linked list (`list_head`). The caller has to/// perform conversion of returned [`CListHead`] to an item (using [`container_of`] or similar).////// # Invariants////// `current` and `sentinel` are valid references into an initialized linked list.struct CListHeadIter<'a> { /// Current position in the list. current: &'a CListHead, /// The sentinel head (used to detect end of iteration). sentinel: &'a CListHead,}
impl<'a> Iterator for CListHeadIter<'a> { type Item = &'a CListHead;
#[inline] fn next(&mut self) -> Option<Self::Item> { // Check if we've reached the sentinel (end of list). if self.current == self.sentinel { return None; }
let item = self.current; self.current = item.next(); Some(item) }}
impl<'a> FusedIterator for CListHeadIter<'a> {}
/// A typed C linked list with a sentinel head intended for FFI use-cases where/// a C subsystem manages a linked list that Rust code needs to read. Generally/// required only for special cases.////// A sentinel head [`CListHead`] represents the entire linked list and can be used/// for iteration over items of type `T`; it is not associated with a specific item.////// The const generic `OFFSET` specifies the byte offset of the `list_head` field within/// the struct that `T` wraps.////// # Invariants////// - The sentinel [`CListHead`] has valid non-`NULL` `next`/`prev` pointers./// - `OFFSET` is the byte offset of the `list_head` field within the struct that `T` wraps./// - All the list's `list_head` nodes have valid non-`NULL` `next`/`prev` pointers.#[repr(transparent)]pub struct CList<T, const OFFSET: usize>(CListHead, PhantomData<T>);
impl<T, const OFFSET: usize> CList<T, OFFSET> { /// Create a typed [`CList`] reference from a raw sentinel `list_head` pointer. /// /// # Safety /// /// - `ptr` must be a valid pointer to an initialized sentinel `list_head` (e.g. via /// `INIT_LIST_HEAD()`), with valid non-`NULL` `next`/`prev` pointers. /// - `ptr` must remain valid for the lifetime `'a`. /// - The list and all linked nodes must not be concurrently modified for the lifetime `'a`. /// - The list must contain items where the `list_head` field is at byte offset `OFFSET`. /// - `T` must be `#[repr(transparent)]` over the C struct. #[inline] pub unsafe fn from_raw<'a>(ptr: *mut bindings::list_head) -> &'a Self { // SAFETY: // - `CList` has the same layout as `CListHead` due to `#[repr(transparent)]`. // - Caller guarantees `ptr` is a valid, sentinel `list_head` object. unsafe { &*ptr.cast() } }
/// Check if the list is empty. #[inline] pub fn is_empty(&self) -> bool { !self.0.is_linked() }
/// Create an iterator over typed items. #[inline] pub fn iter(&self) -> CListIter<'_, T, OFFSET> { let head = &self.0; CListIter { head_iter: CListHeadIter { current: head.next(), sentinel: head, }, _phantom: PhantomData, } }}
/// High-level iterator over typed list items.pub struct CListIter<'a, T, const OFFSET: usize> { head_iter: CListHeadIter<'a>, _phantom: PhantomData<&'a T>,}
impl<'a, T, const OFFSET: usize> Iterator for CListIter<'a, T, OFFSET> { type Item = &'a T;
#[inline] fn next(&mut self) -> Option<Self::Item> { let head = self.head_iter.next()?;
// Convert to item using `OFFSET`. // // SAFETY: The pointer calculation is valid because `OFFSET` is derived // from `offset_of!` per type invariants. Some(unsafe { &*head.as_raw().byte_sub(OFFSET).cast::<T>() }) }}
impl<'a, T, const OFFSET: usize> FusedIterator for CListIter<'a, T, OFFSET> {}
/// Create a C doubly-circular linked list interface [`CList`] from a raw `list_head` pointer.////// This macro creates a `CList<T, OFFSET>` that can iterate over items of type `$rust_type`/// linked via the `$field` field in the underlying C struct `$c_type`.////// # Arguments////// - `$head`: Raw pointer to the sentinel `list_head` object (`*mut bindings::list_head`)./// - `$rust_type`: Each item's Rust wrapper type./// - `$c_type`: Each item's C struct type that contains the embedded `list_head`./// - `$field`: The name of the `list_head` field within the C struct.////// # Safety////// The caller must ensure:////// - `$head` is a valid, initialized sentinel `list_head` (e.g. via `INIT_LIST_HEAD()`)/// pointing to a list that is not concurrently modified for the lifetime of the [`CList`]./// - The list contains items of type `$c_type` linked via an embedded `$field`./// - `$rust_type` is `#[repr(transparent)]` over `$c_type` or has compatible layout.////// # Examples////// Refer to the examples in the [`crate::interop::list`] module documentation.#[macro_export]macro_rules! clist_create { ($head:expr, $rust_type:ty, $c_type:ty, $($field:tt).+) => {{ // Compile-time check that field path is a `list_head`. let _: fn(*const $c_type) -> *const $crate::bindings::list_head = |p| &raw const (*p).$($field).+;
// Calculate offset and create `CList`. const OFFSET: usize = ::core::mem::offset_of!($c_type, $($field).+); $crate::interop::list::CList::<$rust_type, OFFSET>::from_raw($head) }};}pub use clist_create;