From: Wedson Almeida Filho <wedsonaf@gmail.com>
This macro is used to obtain a pointer to an entire struct
when given a pointer to a field in that struct.
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Matt Gilbride <mattgilbride@google.com>
---
rust/kernel/lib.rs | 32 ++++++++++++++++++++++++++++++++
1 file changed, 32 insertions(+)
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 7ac39874aeac..c7963efd1318 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -102,3 +102,35 @@ fn panic(info: &core::panic::PanicInfo<'_>) -> ! {
// SAFETY: FFI call.
unsafe { bindings::BUG() };
}
+
+/// Produces a pointer to an object from a pointer to one of its fields.
+///
+/// # Safety
+///
+/// The pointer passed to this macro, and the pointer returned by this macro, must both be in
+/// bounds of the same allocation.
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::container_of;
+/// struct Test {
+/// a: u64,
+/// b: u32,
+/// }
+///
+/// let test = Test { a: 10, b: 20 };
+/// let b_ptr = &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) };
+/// assert!(core::ptr::eq(&test, test_alias));
+/// ```
+#[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
+ }}
+}
--
2.44.0.rc0.258.g7320e95886-goog