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authorWedson Almeida Filho <wedsonaf@gmail.com>2024-02-19 11:48:08 +0000
committerMiguel Ojeda <ojeda@kernel.org>2024-02-25 19:17:31 +0100
commite944171070b65521c0513c01c56174ec8fd7d249 (patch)
treedbd917cf6917f54f77f3a816153bddc20bdc5b8a
parent4951ddd51b816b5e4095cd3cd3bd46fb73b96a65 (diff)
rust: add `container_of!` macro
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> Link: https://lore.kernel.org/r/20240219-b4-rbtree-v2-1-0b113aab330d@google.com Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
-rw-r--r--rust/kernel/lib.rs32
1 files changed, 32 insertions, 0 deletions
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 1e5f229b8263..be68d5e567b1 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -101,3 +101,35 @@ 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
+ }}
+}