linux-kernel - Re: [PATCH v6 9/9] rust: sync: atomic: Add Atomic<{usize,isize}>

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: <DB93Q0CXTA0G.37LQP5VCP9IGP@kernel.org>
Date: Fri, 11 Jul 2025 11:00:33 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Boqun Feng" <boqun.feng@...il.com>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <lkmm@...ts.linux.dev>,
 <linux-arch@...r.kernel.org>
Cc: "Miguel Ojeda" <ojeda@...nel.org>, "Alex Gaynor"
 <alex.gaynor@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Danilo Krummrich" <dakr@...nel.org>,
 "Will Deacon" <will@...nel.org>, "Peter Zijlstra" <peterz@...radead.org>,
 "Mark Rutland" <mark.rutland@....com>, "Wedson Almeida Filho"
 <wedsonaf@...il.com>, "Viresh Kumar" <viresh.kumar@...aro.org>, "Lyude
 Paul" <lyude@...hat.com>, "Ingo Molnar" <mingo@...nel.org>, "Mitchell Levy"
 <levymitchell0@...il.com>, "Paul E. McKenney" <paulmck@...nel.org>, "Greg
 Kroah-Hartman" <gregkh@...uxfoundation.org>, "Linus Torvalds"
 <torvalds@...ux-foundation.org>, "Thomas Gleixner" <tglx@...utronix.de>,
 "Alan Stern" <stern@...land.harvard.edu>
Subject: Re: [PATCH v6 9/9] rust: sync: atomic: Add Atomic<{usize,isize}>

On Thu Jul 10, 2025 at 8:00 AM CEST, Boqun Feng wrote:
> Add generic atomic support for `usize` and `isize`. Note that instead of
> mapping directly to `atomic_long_t`, the represention type
> (`AllowAtomic::Repr`) is selected based on CONFIG_64BIT. This reduces
> the necessity of creating `atomic_long_*` helpers, which could save
> the binary size of kernel if inline helpers are not available.
>
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Reviewed-by: Andreas Hindborg <a.hindborg@...nel.org>
> Signed-off-by: Boqun Feng <boqun.feng@...il.com>

Reviewed-by: Benno Lossin <lossin@...nel.org>

> ---
>  rust/kernel/sync/atomic.rs | 48 ++++++++++++++++++++++++++++++++++----
>  1 file changed, 44 insertions(+), 4 deletions(-)
>
> diff --git a/rust/kernel/sync/atomic.rs b/rust/kernel/sync/atomic.rs
> index e676bc7d9275..e1e40757d7b5 100644
> --- a/rust/kernel/sync/atomic.rs
> +++ b/rust/kernel/sync/atomic.rs
> @@ -53,6 +53,26 @@ fn delta_into_repr(d: Self::Delta) -> Self::Repr {
>      }
>  }
>  
> +// SAFETY: For 32bit kernel, `isize` has the same size and alignment with `i32` and is round-trip
> +// transmutable to it, for 64bit kernel `isize` has the same size and alignment with `i64` and is
> +// round-trip transmutable to it.
> +unsafe impl generic::AllowAtomic for isize {
> +    #[cfg(not(CONFIG_64BIT))]
> +    type Repr = i32;
> +    #[cfg(CONFIG_64BIT)]
> +    type Repr = i64;

Do we have a static assert with these cfgs that `isize` has the same
size as these?

If not, then it would probably make sense to add them now.

---
Cheers,
Benno

> +}