From: Benno Lossin benno.lossin@proton.me
commit df27cef153603b18a7d094b53cc3d5264ff32797 upstream.
According to [1], `NonNull<T>` and `#[repr(transparent)]` wrapper types such as `Box<T>` have the null pointer optimization only if `T: Sized`. Thus remove the `Zeroable` implementation for the unsized case.
Link: https://doc.rust-lang.org/stable/std/option/index.html#representation [1] Reported-by: Alice Ryhl aliceryhl@google.com Closes: https://lore.kernel.org/rust-for-linux/CAH5fLghL+qzrD8KiCF1V3vf2YcC6aWySzkma... Cc: stable@vger.kernel.org # v6.12+ (a custom patch will be needed for 6.6.y) Fixes: 38cde0bd7b67 ("rust: init: add `Zeroable` trait and `init::zeroed` function") Signed-off-by: Benno Lossin benno.lossin@proton.me Reviewed-by: Alice Ryhl aliceryhl@google.com Reviewed-by: Andreas Hindborg a.hindborg@kernel.org Link: https://lore.kernel.org/r/20250305132836.2145476-1-benno.lossin@proton.me [ Added Closes tag and moved up the Reported-by one. - Miguel ] Signed-off-by: Miguel Ojeda ojeda@kernel.org --- rust/kernel/init.rs | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs index 2d4b19b86857..6ef9f6182018 100644 --- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -1310,17 +1310,14 @@ macro_rules! impl_zeroable { // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`. {<T: ?Sized + Zeroable>} UnsafeCell<T>,
- // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee). + // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee: + // https://doc.rust-lang.org/stable/std/option/index.html#representation). Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>, Option<NonZeroU128>, Option<NonZeroUsize>, Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>, Option<NonZeroI128>, Option<NonZeroIsize>, - - // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee). - // - // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant. - {<T: ?Sized>} Option<NonNull<T>>, - {<T: ?Sized>} Option<Box<T>>, + {<T>} Option<NonNull<T>>, + {<T>} Option<Box<T>>,
// SAFETY: `null` pointer is valid. //