Avoid casting the input pointer to `*const _`, allowing the output pointer to be `*mut` if the input is `*mut`. This allows a number of `*const` to `*mut` conversions to be removed at the cost of slightly worse ergonomics when the macro is used with a reference rather than a pointer; the only example of this was in the macro's own doctest.
Reviewed-by: Benno Lossin benno.lossin@proton.me Reviewed-by: Alice Ryhl aliceryhl@google.com Signed-off-by: Tamir Duberstein tamird@gmail.com --- rust/kernel/lib.rs | 5 ++--- rust/kernel/pci.rs | 2 +- rust/kernel/platform.rs | 2 +- rust/kernel/rbtree.rs | 23 ++++++++++------------- 4 files changed, 14 insertions(+), 18 deletions(-)
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index c92497c7c655..fc6835cc36a3 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -187,7 +187,7 @@ fn panic(info: &core::panic::PanicInfo<'_>) -> ! { /// } /// /// let test = Test { a: 10, b: 20 }; -/// let b_ptr = &test.b; +/// let b_ptr: *const _ = &test.b; /// // SAFETY: The pointer points at the `b` field of a `Test`, so the resulting pointer will be /// // in-bounds of the same allocation as `b_ptr`. /// let test_alias = unsafe { container_of!(b_ptr, Test, b) }; @@ -196,9 +196,8 @@ fn panic(info: &core::panic::PanicInfo<'_>) -> ! { #[macro_export] macro_rules! container_of { ($ptr:expr, $type:ty, $($f:tt)*) => {{ - let ptr = $ptr as *const _ as *const u8; let offset: usize = ::core::mem::offset_of!($type, $($f)*); - ptr.sub(offset) as *const $type + $ptr.byte_sub(offset).cast::<$type>() }} }
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs index f7b2743828ae..271a7690a9a0 100644 --- a/rust/kernel/pci.rs +++ b/rust/kernel/pci.rs @@ -364,7 +364,7 @@ pub unsafe fn from_dev(dev: ARefdevice::Device) -> Self { fn as_raw(&self) -> *mut bindings::pci_dev { // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device` // embedded in `struct pci_dev`. - unsafe { container_of!(self.0.as_raw(), bindings::pci_dev, dev) as _ } + unsafe { container_of!(self.0.as_raw(), bindings::pci_dev, dev) } }
/// Returns the PCI vendor ID. diff --git a/rust/kernel/platform.rs b/rust/kernel/platform.rs index 1297f5292ba9..84a4ecc642a1 100644 --- a/rust/kernel/platform.rs +++ b/rust/kernel/platform.rs @@ -189,7 +189,7 @@ unsafe fn from_dev(dev: ARefdevice::Device) -> Self { fn as_raw(&self) -> *mut bindings::platform_device { // SAFETY: By the type invariant `self.0.as_raw` is a pointer to the `struct device` // embedded in `struct platform_device`. - unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) }.cast_mut() + unsafe { container_of!(self.0.as_raw(), bindings::platform_device, dev) } } }
diff --git a/rust/kernel/rbtree.rs b/rust/kernel/rbtree.rs index 1ea25c7092fb..27de954a0889 100644 --- a/rust/kernel/rbtree.rs +++ b/rust/kernel/rbtree.rs @@ -424,7 +424,7 @@ pub fn cursor_lower_bound(&mut self, key: &K) -> Option<Cursor<'_, K, V>> while !node.is_null() { // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self` // point to the links field of `Node<K, V>` objects. - let this = unsafe { container_of!(node, Node<K, V>, links) }.cast_mut(); + let this = unsafe { container_of!(node, Node<K, V>, links) }; // SAFETY: `this` is a non-null node so it is valid by the type invariants. let this_key = unsafe { &(*this).key }; // SAFETY: `node` is a non-null node so it is valid by the type invariants. @@ -496,7 +496,7 @@ fn drop(&mut self) { // but it is not observable. The loop invariant is still maintained.
// SAFETY: `this` is valid per the loop invariant. - unsafe { drop(KBox::from_raw(this.cast_mut())) }; + unsafe { drop(KBox::from_raw(this)) }; } } } @@ -761,7 +761,7 @@ pub fn remove_current(self) -> (Option<Self>, RBTreeNode<K, V>) { let next = self.get_neighbor_raw(Direction::Next); // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self` // point to the links field of `Node<K, V>` objects. - let this = unsafe { container_of!(self.current.as_ptr(), Node<K, V>, links) }.cast_mut(); + let this = unsafe { container_of!(self.current.as_ptr(), Node<K, V>, links) }; // SAFETY: `this` is valid by the type invariants as described above. let node = unsafe { KBox::from_raw(this) }; let node = RBTreeNode { node }; @@ -806,7 +806,7 @@ fn remove_neighbor(&mut self, direction: Direction) -> Option<RBTreeNode<K, V>> unsafe { bindings::rb_erase(neighbor, addr_of_mut!(self.tree.root)) }; // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self` // point to the links field of `Node<K, V>` objects. - let this = unsafe { container_of!(neighbor, Node<K, V>, links) }.cast_mut(); + let this = unsafe { container_of!(neighbor, Node<K, V>, links) }; // SAFETY: `this` is valid by the type invariants as described above. let node = unsafe { KBox::from_raw(this) }; return Some(RBTreeNode { node }); @@ -912,7 +912,7 @@ unsafe fn to_key_value_mut<'b>(node: NonNullbindings::rb_node) -> (&'b K, &'b unsafe fn to_key_value_raw<'b>(node: NonNullbindings::rb_node) -> (&'b K, *mut V) { // SAFETY: By the type invariant of `Self`, all non-null `rb_node` pointers stored in `self` // point to the links field of `Node<K, V>` objects. - let this = unsafe { container_of!(node.as_ptr(), Node<K, V>, links) }.cast_mut(); + let this = unsafe { container_of!(node.as_ptr(), Node<K, V>, links) }; // SAFETY: The passed `node` is the current node or a non-null neighbor, // thus `this` is valid by the type invariants. let k = unsafe { &(*this).key }; @@ -1021,7 +1021,7 @@ fn next(&mut self) -> OptionSelf::Item {
// SAFETY: By the type invariant of `IterRaw`, `self.next` is a valid node in an `RBTree`, // and by the type invariant of `RBTree`, all nodes point to the links field of `Node<K, V>` objects. - let cur = unsafe { container_of!(self.next, Node<K, V>, links) }.cast_mut(); + let cur = unsafe { container_of!(self.next, Node<K, V>, links) };
// SAFETY: `self.next` is a valid tree node by the type invariants. self.next = unsafe { bindings::rb_next(self.next) }; @@ -1216,7 +1216,7 @@ pub fn get_mut(&mut self) -> &mut V { // SAFETY: // - `self.node_links` is a valid pointer to a node in the tree. // - We have exclusive access to the underlying tree, and can thus give out a mutable reference. - unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links).cast_mut())).value } + unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links))).value } }
/// Converts the entry into a mutable reference to its value. @@ -1226,7 +1226,7 @@ pub fn into_mut(self) -> &'a mut V { // SAFETY: // - `self.node_links` is a valid pointer to a node in the tree. // - This consumes the `&'a mut RBTree<K, V>`, therefore it can give out a mutable reference that lives for `'a`. - unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links).cast_mut())).value } + unsafe { &mut (*(container_of!(self.node_links, Node<K, V>, links))).value } }
/// Remove this entry from the [`RBTree`]. @@ -1239,9 +1239,7 @@ pub fn remove_node(self) -> RBTreeNode<K, V> { RBTreeNode { // SAFETY: The node was a node in the tree, but we removed it, so we can convert it // back into a box. - node: unsafe { - KBox::from_raw(container_of!(self.node_links, Node<K, V>, links).cast_mut()) - }, + node: unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links)) }, } }
@@ -1272,8 +1270,7 @@ fn replace(self, node: RBTreeNode<K, V>) -> RBTreeNode<K, V> { // SAFETY: // - `self.node_ptr` produces a valid pointer to a node in the tree. // - Now that we removed this entry from the tree, we can convert the node to a box. - let old_node = - unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links).cast_mut()) }; + let old_node = unsafe { KBox::from_raw(container_of!(self.node_links, Node<K, V>, links)) };
RBTreeNode { node: old_node } }