Messages in this thread Patch in this message | | | Date | Sun, 6 Aug 2023 17:08:31 +0100 | From | Gary Guo <> | Subject | Re: [PATCH v3 10/13] rust: init: implement `Zeroable` for `UnsafeCell<T>` and `Opaque<T>` |
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On Sat, 29 Jul 2023 09:10:19 +0000 Benno Lossin <benno.lossin@proton.me> wrote:
> `UnsafeCell<T>` and `T` have the same layout so if `T` is `Zeroable` > then so should `UnsafeCell<T>` be. This allows using the derive macro > for `Zeroable` on types that contain an `UnsafeCell<T>`. > Since `Opaque<T>` contains a `MaybeUninit<T>`, all bytes zero is a valid > bit pattern for that type. > > Signed-off-by: Benno Lossin <benno.lossin@proton.me>
Reviewed-by: Gary Guo <gary@garyguo.net>
> --- > v2 -> v3: > - also implement Zeroable for `UnsafeCell<T>` when `T: Zeroable`, > - use `impl_zeroable!` instead of `derive(Zeroable)`. > > rust/kernel/init.rs | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs > index af96d4acc26b..06ecab4901f2 100644 > --- a/rust/kernel/init.rs > +++ b/rust/kernel/init.rs > @@ -212,10 +212,12 @@ > use crate::{ > error::{self, Error}, > sync::UniqueArc, > + types::Opaque, > }; > use alloc::boxed::Box; > use core::{ > alloc::AllocError, > + cell::UnsafeCell, > convert::Infallible, > marker::PhantomData, > mem::MaybeUninit, > @@ -1157,6 +1159,11 @@ macro_rules! impl_zeroable { > > // SAFETY: Type is allowed to take any value, including all zeros. > {<T>} MaybeUninit<T>, > + // SAFETY: Type is allowed to take any value, including all zeros. > + {<T>} Opaque<T>, > + > + // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`. > + {<T: ?Sized + Zeroable>} UnsafeCell<T>, > > // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee). > Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,
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