diff options
| -rw-r--r-- | rust/kernel/init.rs | 97 |
1 files changed, 95 insertions, 2 deletions
diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs index 99751375e7c8..ffd539e2f5ef 100644 --- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -195,8 +195,14 @@ use crate::{ }; use alloc::boxed::Box; use core::{ - alloc::AllocError, cell::Cell, convert::Infallible, marker::PhantomData, mem::MaybeUninit, - pin::Pin, ptr, + alloc::AllocError, + cell::Cell, + convert::Infallible, + marker::PhantomData, + mem::MaybeUninit, + num::*, + pin::Pin, + ptr::{self, NonNull}, }; #[doc(hidden)] @@ -1323,3 +1329,90 @@ 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>() -> 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 { + ($($({$($generics:tt)*})? $t:ty, )*) => { + $(unsafe impl$($($generics)*)? Zeroable for $t {})* + }; +} + +impl_zeroable! { + // SAFETY: All primitives that are allowed to be zero. + bool, + char, + u8, u16, u32, u64, u128, usize, + i8, i16, i32, i64, i128, isize, + f32, f64, + + // SAFETY: These are ZSTs, there is nothing to zero. + {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, Infallible, (), + + // SAFETY: Type is allowed to take any value, including all zeros. + {<T>} MaybeUninit<T>, + + // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee). + Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>, + Option<NonZeroU128>, Option<NonZeroUsize>, + Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>, + Option<NonZeroI128>, Option<NonZeroIsize>, + + // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee). + // + // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant. + {<T: ?Sized>} Option<NonNull<T>>, + {<T: ?Sized>} Option<Box<T>>, + + // SAFETY: `null` pointer is valid. + // + // We cannot use `T: ?Sized`, since the VTABLE pointer part of fat pointers is not allowed to be + // null. + // + // When `Pointee` gets stabilized, we could use + // `T: ?Sized where <T as Pointee>::Metadata: Zeroable` + {<T>} *mut T, {<T>} *const T, + + // SAFETY: `null` pointer is valid and the metadata part of these fat pointers is allowed to be + // zero. + {<T>} *mut [T], {<T>} *const [T], *mut str, *const str, + + // SAFETY: `T` is `Zeroable`. + {<const N: usize, T: Zeroable>} [T; N], {<T: Zeroable>} Wrapping<T>, +} + +macro_rules! impl_tuple_zeroable { + ($(,)?) => {}; + ($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); |