linux-kernel - Re: [PATCH v4 1/2] rust: add `Alignment` 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: <DCNEM8ECAQED.1CTI4N9WE311P@nvidia.com>
Date: Mon, 08 Sep 2025 21:06:08 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Danilo Krummrich" <dakr@...nel.org>
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>, "Benno Lossin" <lossin@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, <linux-kernel@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <nouveau@...ts.freedesktop.org>
Subject: Re: [PATCH v4 1/2] rust: add `Alignment` type

On Mon Sep 8, 2025 at 9:02 PM JST, Danilo Krummrich wrote:
> On 8/21/25 2:42 PM, Alexandre Courbot wrote:
>> +    /// Validates that `align` is a power of two at build-time, and returns an [`Alignment`] of the
>> +    /// same value.
>> +    ///
>> +    /// A build error is triggered if `align` cannot be asserted to be a power of two.
>> +    ///
>> +    /// # Examples
>> +    ///
>> +    /// ```
>> +    /// use kernel::ptr::Alignment;
>> +    ///
>> +    /// let v = Alignment::new(16);
>> +    /// assert_eq!(v.as_usize(), 16);
>> +    /// ```
>> +    #[inline(always)]
>> +    pub const fn new(align: usize) -> Self {
>> +        build_assert!(align.is_power_of_two());
>> +
>> +        // INVARIANT: `align` is a power of two.
>> +        // SAFETY: `align` is a power of two, and thus non-zero.
>> +        Self(unsafe { NonZero::new_unchecked(align) })
>> +    }
>
> For DmaMask::new() we used a const generic instead, which makes it more obvious
> to the caller that the argument must be known at compile time. So, I'd prefer
> this here as well.

Ah, being consistent is good, and I think I prefer the const generic as
well. Let's do the same thing here.