Adds a macro for safely implementing the ListItem trait. As part of the
implementation of the macro, we also provide a HasListLinks trait
similar to the workqueue's HasWorkItem trait.
The HasListLinks trait is only necessary if you are implementing
ListItem using the impl_list_item macro.
Signed-off-by: Alice Ryhl <[email protected]>
---
rust/kernel/list.rs | 3 ++
rust/kernel/list/impl_list_item_mod.rs | 99 ++++++++++++++++++++++++++++++++++
2 files changed, 102 insertions(+)
diff --git a/rust/kernel/list.rs b/rust/kernel/list.rs
index b5cfbb96a392..f2eca542e090 100644
--- a/rust/kernel/list.rs
+++ b/rust/kernel/list.rs
@@ -8,6 +8,9 @@
use crate::types::Opaque;
use core::ptr;
+mod impl_list_item_mod;
+pub use self::impl_list_item_mod::{impl_has_list_links, impl_list_item, HasListLinks};
+
mod arc;
pub use self::arc::{
impl_list_arc_safe, AtomicListArcTracker, ListArc, ListArcSafe, TryNewListArc,
diff --git a/rust/kernel/list/impl_list_item_mod.rs b/rust/kernel/list/impl_list_item_mod.rs
new file mode 100644
index 000000000000..3ff483be89d1
--- /dev/null
+++ b/rust/kernel/list/impl_list_item_mod.rs
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0
+
+// Copyright (C) 2024 Google LLC.
+
+//! Helpers for implementing list traits safely.
+
+use crate::list::ListLinks;
+
+/// Declares that this type has a `ListLinks<ID>` field at a fixed offset.
+///
+/// This trait is only used to help implement `ListItem` safely. If `ListItem` is implemented
+/// manually, then this trait is not needed.
+///
+/// # Safety
+///
+/// All values of this type must have a `ListLinks<ID>` field at the given offset.
+pub unsafe trait HasListLinks<const ID: u64 = 0> {
+ /// The offset of the `ListLinks` field.
+ const OFFSET: usize;
+
+ /// Returns a pointer to the [`ListLinks<T, ID>`] field.
+ ///
+ /// # Safety
+ ///
+ /// The provided pointer must point at a valid struct of type `Self`.
+ ///
+ /// [`ListLinks<T, ID>`]: ListLinks
+ // We don't really need this method, but it's necessary for the implementation of
+ // `impl_has_work!` to be correct.
+ #[inline]
+ unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut ListLinks<ID> {
+ // SAFETY: The caller promises that the pointer is valid. The implementer promises that the
+ // `OFFSET` constant is correct.
+ unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut ListLinks<ID> }
+ }
+}
+
+/// Implements the [`HasListLinks`] trait for the given type.
+#[macro_export]
+macro_rules! impl_has_list_links {
+ ($(impl$(<$($implarg:ident),*>)?
+ HasListLinks$(<$id:tt>)?
+ for $self:ident $(<$($selfarg:ty),*>)?
+ { self$(.$field:ident)* }
+ )*) => {$(
+ // SAFETY: The implementation of `raw_get_list_links` only compiles if the field has the
+ // right type.
+ unsafe impl$(<$($implarg),*>)? $crate::list::HasListLinks$(<$id>)? for
+ $self $(<$($selfarg),*>)?
+ {
+ const OFFSET: usize = ::core::mem::offset_of!(Self, $($field).*) as usize;
+
+ #[inline]
+ unsafe fn raw_get_list_links(ptr: *mut Self) -> *mut $crate::list::ListLinks$(<$id>)? {
+ // SAFETY: The caller promises that the pointer is not dangling.
+ unsafe {
+ ::core::ptr::addr_of_mut!((*ptr)$(.$field)*)
+ }
+ }
+ }
+ )*};
+}
+pub use impl_has_list_links;
+
+/// Implements the [`ListItem`] trait for the given type.
+///
+/// Assumes that the type implements [`HasListLinks`].
+///
+/// [`ListItem`]: crate::list::ListItem
+#[macro_export]
+macro_rules! impl_list_item {
+ (
+ impl$({$($generics:tt)*})? $crate::list::ListItem<$num:tt> for $t:ty {
+ using ListLinks;
+ } $($rest:tt)*
+ ) => {
+ unsafe impl$(<$($generics)*>)? $crate::list::ListItem<$num> for $t {
+ unsafe fn view_links(me: *const Self) -> *mut $crate::list::ListLinks<$num> {
+ unsafe {
+ <Self as $crate::list::HasListLinks<$num>>::raw_get_list_links(me.cast_mut())
+ }
+ }
+
+ unsafe fn view_value(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
+ let offset = <Self as $crate::list::HasListLinks<$num>>::OFFSET;
+ unsafe { (me as *const u8).sub(offset) as *const Self }
+ }
+
+ unsafe fn prepare_to_insert(me: *const Self) -> *mut $crate::list::ListLinks<$num> {
+ unsafe { <Self as $crate::list::ListItem<$num>>::view_links(me) }
+ }
+
+ unsafe fn post_remove(me: *mut $crate::list::ListLinks<$num>) -> *const Self {
+ unsafe { <Self as $crate::list::ListItem<$num>>::view_value(me) }
+ }
+ }
+ };
+}
+pub use impl_list_item;
--
2.45.0.rc1.225.g2a3ae87e7f-goog