linux-kernel - Re: [PATCH v3 4/7] rust: cpumask: Add getters for globally defined cpumasks

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: <aLi7Ptya5xp22P-B@yury>
Date: Wed, 3 Sep 2025 18:03:51 -0400
From: Yury Norov <yury.norov@...il.com>
To: Mitchell Levy <levymitchell0@...il.com>
Cc: 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>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Danilo Krummrich <dakr@...nel.org>,
	Benno Lossin <lossin@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Tyler Hicks <code@...icks.com>, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH v3 4/7] rust: cpumask: Add getters for globally defined
 cpumasks

On Thu, Aug 28, 2025 at 12:00:11PM -0700, Mitchell Levy wrote:
> Add getters for the global cpumasks documented in
> `include/linux/cpumask.h`, specifically:
> - cpu_possible_mask
> - cpu_online_mask
> - cpu_enabled_mask
> - cpu_present_mask
> - cpu_active_mask
> 
> Signed-off-by: Mitchell Levy <levymitchell0@...il.com>
> ---
>  rust/kernel/cpumask.rs | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 46 insertions(+)
> 
> diff --git a/rust/kernel/cpumask.rs b/rust/kernel/cpumask.rs
> index b7401848f59e..ca9aa6875b4a 100644
> --- a/rust/kernel/cpumask.rs
> +++ b/rust/kernel/cpumask.rs
> @@ -77,6 +77,52 @@ pub unsafe fn as_ref<'a>(ptr: *const bindings::cpumask) -> &'a Self {
>          unsafe { &*ptr.cast() }
>      }
>  
> +    /// Get a CPU mask representing possible CPUs; has bit `cpu` set iff cpu is populatable
> +    #[inline]
> +    pub fn possible() -> &'static Self {
> +        // SAFETY: `__cpu_possible_mask` is a valid global provided by the kernel that lives
> +        // forever.
> +        unsafe { Cpumask::as_ref(&raw const bindings::__cpu_possible_mask) }
> +    }

This function and the following look like returning a boolean.
Maybe possible_cpus()? 

The general rule is to keep the rust naming as close to C as
possible, but in this case Cpumask::cpu_possible_mask is, OK,
somewhat excessive.

Thanks,
Yury

> +
> +    /// Get a CPU mask representing online CPUs; has bit `cpu` set iff cpu available to the
> +    /// scheduler
> +    #[inline]
> +    pub fn online() -> &'static Self {
> +        // SAFETY: `__cpu_online_mask` is a valid global provided by the kernel that lives forever.
> +        // Since we wrap the returned pointer in an `Opaque`, it's ok that `__cpu_online_mask`
> +        // may change its value.
> +        unsafe { Cpumask::as_ref(&raw const bindings::__cpu_online_mask) }
> +    }
> +
> +    /// Get a CPU mask representing enabled CPUs; has bit `cpu` set iff cpu can be brought online
> +    #[inline]
> +    pub fn enabled() -> &'static Self {
> +        // SAFETY: `__cpu_enabled_mask` is a valid global provided by the kernel that lives forever.
> +        // Since we wrap the returned pointer in an `Opaque`, it's ok that `__cpu_enabled_mask`
> +        // may change its value.
> +        unsafe { Cpumask::as_ref(&raw const bindings::__cpu_enabled_mask) }
> +    }
> +
> +    /// Get a CPU mask representing present CPUs; has bit `cpu` set iff cpu is populated
> +    #[inline]
> +    pub fn present() -> &'static Self {
> +        // SAFETY: `__cpu_present_mask` is a valid global provided by the kernel that lives
> +        // forever. Since we wrap the returned pointer in an `Opaque`, it's ok that
> +        // `__cpu_present_mask` may change its value.
> +        unsafe { Cpumask::as_ref(&raw const bindings::__cpu_present_mask) }
> +    }
> +
> +    /// Get a CPU mask representing active CPUs; has bit `cpu` set iff cpu is available to
> +    /// migration.
> +    #[inline]
> +    pub fn active() -> &'static Self {
> +        // SAFETY: `__cpu_active_mask` is a valid global provided by the kernel that lives forever.
> +        // Since we wrap the returned pointer in an `Opaque`, it's ok that `__cpu_active_mask`
> +        // may change its value.
> +        unsafe { Cpumask::as_ref(&raw const bindings::__cpu_active_mask) }
> +    }
> +
>      /// Obtain the raw `struct cpumask` pointer.
>      pub fn as_raw(&self) -> *mut bindings::cpumask {
>          let this: *const Self = self;
> 
> -- 
> 2.34.1