Commit e9441710 authored by Wedson Almeida Filho's avatar Wedson Almeida Filho Committed by Miguel Ojeda
Browse files

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: default avatarWedson Almeida Filho <wedsonaf@gmail.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Tested-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarMatt Gilbride <mattgilbride@google.com>
Link: https://lore.kernel.org/r/20240219-b4-rbtree-v2-1-0b113aab330d@google.com


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 4951ddd5

rust/kernel/lib.rs

+32 −0
Original line number Diff line number Diff line
@@ -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

    }}

}