rust: split Rust-only "common" crate

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Link: https://lore.kernel.org/r/20250827104147.717203-6-marcandre.lureau@redhat.com
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/rust/common/src/zeroable.rs b/rust/common/src/zeroable.rs
new file mode 100644
index 0000000000..fd056deb1f
--- /dev/null
+++ b/rust/common/src/zeroable.rs
@@ -0,0 +1,18 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Defines a trait for structs that can be safely initialized with zero bytes.
+
+/// Encapsulates the requirement that
+/// `MaybeUninit::<Self>::zeroed().assume_init()` does not cause undefined
+/// behavior.
+///
+/// # Safety
+///
+/// Do not add this trait to a type unless all-zeroes is a valid value for the
+/// type.  In particular, raw pointers can be zero, but references and
+/// `NonNull<T>` cannot.
+pub unsafe trait Zeroable: Default {
+    /// Return a value of Self whose memory representation consists of all
+    /// zeroes, with the possible exclusion of padding bytes.
+    const ZERO: Self = unsafe { ::core::mem::MaybeUninit::<Self>::zeroed().assume_init() };
+}