linux-kernel - Re: [PATCH] rust: transmute: add `as

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAH5fLgj-crrKyZbgPBLyWNmzw_oB6ZVc==rqAFt5jr6402nHLA@mail.gmail.com>
Date: Fri, 25 Jul 2025 09:52:44 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: Abdiel Janulgue <abdiel.janulgue@...il.com>, Danilo Krummrich <dakr@...nel.org>, 
	Daniel Almeida <daniel.almeida@...labora.com>, Robin Murphy <robin.murphy@....com>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, 
	Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <lossin@...nel.org>, Trevor Gross <tmgross@...ch.edu>, 
	"Christian S. Lima" <christiansantoslima21@...il.com>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: transmute: add `as_bytes` method for `AsBytes` trait

On Fri, Jul 25, 2025 at 4:11 AM Alexandre Courbot <acourbot@...dia.com> wrote:
>
> Every time that implements `AsBytes` should be able to provide its byte
> representation. Introduce the `as_bytes` method that returns the
> implementer as a stream of bytes.
>
> Since types implementing `Sized` can trivially be represented as a
> stream of bytes, introduce the `AsBytesSized` proxy trait that can be
> implemented for any `Sized` type and provides an `AsBytes`
> implementation suitable for such types. Types that are not `Sized` need
> to implement `AsBytes` directly and provide a method implementation.
>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>

Is the AsBytesSized trait necessary? Can't we just do this?

pub unsafe trait AsBytes {
    /// Returns `self` as a slice of bytes.
    fn as_bytes(&self) -> &[u8] {
        let size = size_of_val(self);
        let ptr = self as *const Self as *const u8;
        unsafe { slice::from_raw_parts(ptr, size) }
    }
}

Alice