linux-kernel - Re: [PATCH v2 4/5] rust: types: implement `ForeignOwnable` for the unit type

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: <20230130184151.651303ad.gary@garyguo.net>
Date:   Mon, 30 Jan 2023 18:41:51 +0000
From:   Gary Guo <gary@...yguo.net>
To:     Wedson Almeida Filho <wedsonaf@...il.com>
Cc:     rust-for-linux@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        linux-kernel@...r.kernel.org,
        Vincenzo Palazzo <vincenzopalazzodev@...il.com>
Subject: Re: [PATCH v2 4/5] rust: types: implement `ForeignOwnable` for the
 unit type

On Mon, 30 Jan 2023 03:44:03 -0300
Wedson Almeida Filho <wedsonaf@...il.com> wrote:

> This allows us to use the unit type `()` when we have no object whose
> ownership must be managed but one implementing the `ForeignOwnable`
> trait is needed.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>
> Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@...il.com>

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
> v1 -> v2: use `NonNull::dangling` to generate pointer
> 
>  rust/kernel/types.rs | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
> index 411655eca3e9..9d0fdbc55843 100644
> --- a/rust/kernel/types.rs
> +++ b/rust/kernel/types.rs
> @@ -85,6 +85,18 @@ impl<T: 'static> ForeignOwnable for Box<T> {
>      }
>  }
>  
> +impl ForeignOwnable for () {
> +    type Borrowed<'a> = ();
> +
> +    fn into_foreign(self) -> *const core::ffi::c_void {
> +        core::ptr::NonNull::dangling().as_ptr()
> +    }
> +
> +    unsafe fn borrow<'a>(_: *const core::ffi::c_void) -> Self::Borrowed<'a> {}
> +
> +    unsafe fn from_foreign(_: *const core::ffi::c_void) -> Self {}
> +}
> +
>  /// Runs a cleanup function/closure when dropped.
>  ///
>  /// The [`ScopeGuard::dismiss`] function prevents the cleanup function from running.