From 331c24e6ce814af2af74bac648d1ac1708873e9c Mon Sep 17 00:00:00 2001 From: Alexandre Courbot Date: Fri, 1 Aug 2025 22:24:10 +0900 Subject: [PATCH] rust: transmute: add `as_bytes_mut` method to `AsBytes` trait Types that implement both `AsBytes` and `FromBytes` can be safely modified as a slice of bytes. Add a `as_bytes_mut` method for that purpose. [acourbot@nvidia.com: use fully qualified `core::mem::size_of_val` to build with Rust 1.78.] Reviewed-by: Alice Ryhl Reviewed-by: Danilo Krummrich Reviewed-by: Gary Guo Reviewed-by: Benno Lossin Acked-by: Miguel Ojeda Link: https://lore.kernel.org/r/20250801-as_bytes-v5-2-975f87d5dc85@nvidia.com Signed-off-by: Alexandre Courbot --- rust/kernel/transmute.rs | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/rust/kernel/transmute.rs b/rust/kernel/transmute.rs index a2d8f39182b2..517a432ac693 100644 --- a/rust/kernel/transmute.rs +++ b/rust/kernel/transmute.rs @@ -57,6 +57,21 @@ pub unsafe trait AsBytes { // SAFETY: `data` is non-null and valid for reads of `len * sizeof::()` bytes. unsafe { core::slice::from_raw_parts(data, len) } } + + /// Returns `self` as a mutable slice of bytes. + fn as_bytes_mut(&mut self) -> &mut [u8] + where + Self: FromBytes, + { + // CAST: `Self` implements both `AsBytes` and `FromBytes` thus making `Self` + // bi-directionally transmutable to `[u8; size_of_val(self)]`. + let data = core::ptr::from_mut(self).cast::(); + let len = core::mem::size_of_val(self); + + // SAFETY: `data` is non-null and valid for read and writes of `len * sizeof::()` + // bytes. + unsafe { core::slice::from_raw_parts_mut(data, len) } + } } macro_rules! impl_asbytes { -- 2.51.0