Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | Date | Thu, 30 Mar 2023 12:06:43 +0100 | From | Gary Guo <> | Subject | Re: [PATCH v3 09/13] rust: init: add `Zeroable` trait and `init::zeroed` function |
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On Wed, 29 Mar 2023 22:33:35 +0000 y86-dev@protonmail.com wrote:
> From: Benno Lossin <y86-dev@protonmail.com> > > Add the `Zeroable` trait which marks types that can be initialized by > writing `0x00` to every byte of the type. Also add the `init::zeroed` > function that creates an initializer for a `Zeroable` type that writes > `0x00` to every byte. > > Signed-off-by: Benno Lossin <y86-dev@protonmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
> --- > rust/kernel/init.rs | 65 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 65 insertions(+) > > diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs > index 3358f14beffb..a923546696ce 100644 > --- a/rust/kernel/init.rs > +++ b/rust/kernel/init.rs > @@ -1254,3 +1254,68 @@ pub unsafe trait PinnedDrop: __internal::HasPinData { > /// automatically. > fn drop(self: Pin<&mut Self>, only_call_from_drop: __internal::OnlyCallFromDrop); > } > + > +/// Marker trait for types that can be initialized by writing just zeroes. > +/// > +/// # Safety > +/// > +/// The bit pattern consisting of only zeroes is a valid bit pattern for this type. In other words, > +/// this is not UB: > +/// > +/// ```rust,ignore > +/// let val: Self = unsafe { core::mem::zeroed() }; > +/// ``` > +pub unsafe trait Zeroable {} > + > +/// Create a new zeroed T. > +/// > +/// The returned initializer will write `0x00` to every byte of the given `slot`. > +#[inline] > +pub fn zeroed<T: Zeroable + Unpin>() -> impl Init<T> { > + // SAFETY: Because `T: Zeroable`, all bytes zero is a valid bit pattern for `T` > + // and because we write all zeroes, the memory is initialized. > + unsafe { > + init_from_closure(|slot: *mut T| { > + slot.write_bytes(0, 1); > + Ok(()) > + }) > + } > +} > + > +macro_rules! impl_zeroable { > + ($($t:ty, )*) => { > + $(unsafe impl Zeroable for $t {})* > + }; > +} > + > +impl_zeroable! { > + // SAFETY: All primitives that are allowed to be zero. > + bool, > + char, > + u8, u16, u32, u64, u128, usize, > + i8, i16, i32, i64, i128, isize, > + f32, f64, > + // SAFETY: There is nothing to zero. > + core::marker::PhantomPinned, Infallible, (), > +} > + > +// SAFETY: We are allowed to zero padding bytes. > +unsafe impl<const N: usize, T: Zeroable> Zeroable for [T; N] {} > + > +// SAFETY: There is nothing to zero. > +unsafe impl<T: ?Sized> Zeroable for PhantomData<T> {} > + > +// SAFETY: `null` pointer is valid. > +unsafe impl<T: ?Sized> Zeroable for *mut T {} > +unsafe impl<T: ?Sized> Zeroable for *const T {} > + > +macro_rules! impl_tuple_zeroable { > + ($(,)?) => {}; > + ($first:ident, $($t:ident),* $(,)?) => { > + // SAFETY: All elements are zeroable and padding can be zero. > + unsafe impl<$first: Zeroable, $($t: Zeroable),*> Zeroable for ($first, $($t),*) {} > + impl_tuple_zeroable!($($t),* ,); > + } > +} > + > +impl_tuple_zeroable!(A, B, C, D, E, F, G, H, I, J); > -- > 2.39.2 > >
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