Commit b9b88be0 authored Aug 14, 2023 by Benno Lossin Committed by Miguel Ojeda Aug 21, 2023

rust: init: wrap type checking struct initializers in a closure

In the implementation of the init macros there is a `if false` statement
that type checks the initializer to ensure every field is initialized.
Since the next patch has a stack variable to store the struct, the
function might allocate too much memory on debug builds. Putting the
struct into a closure that is never executed ensures that even in debug
builds no stack overflow error is caused. In release builds this was not
a problem since the code was optimized away due to the `if false`.

Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20230814084602.25699-6-benno.lossin@proton.me

Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

parent 97de919d

rust/kernel/init/macros.rs

+4 −4

Original line number	Diff line number	Diff line
		@@ -1040,14 +1040,14 @@ macro_rules! __init_internal {
		// once, this struct initializer will still be type-checked and complain with a
		// very natural error message if a field is forgotten/mentioned more than once.
		#[allow(unreachable_code, clippy::diverging_sub_expression)]
		if false {
		let _ = \|\| {
		$crate::__init_internal!(make_initializer:
		@slot(slot),
		@type_name($t),
		@munch_fields($($fields)*,),
		@acc(),
		);
		}
		};
		}
		Ok(__InitOk)
		}
		@@ -1168,8 +1168,8 @@ macro_rules! __init_internal {
		@acc($($acc:tt)*),
		) => {
		// Endpoint, nothing more to munch, create the initializer.
		// Since we are in the `if false` branch, this will never get executed. We abuse `slot` to
		// get the correct type inference here:
		// Since we are in the closure that is never called, this will never get executed.
		// We abuse `slot` to get the correct type inference here:
		unsafe {
		::core::ptr::write($slot, $t {
		$($acc)*