linux-kernel - Re: [PATCH v4 1/6] rust: bitmap: add MAX_LEN and NO_ALLOC_MAX

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: <aRIAQVjLiM1UKzXT@yury>
Date: Mon, 10 Nov 2025 10:09:53 -0500
From: Yury Norov <yury.norov@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Tamir Duberstein <tamird@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Christian Brauner <brauner@...nel.org>,
	Carlos Llamas <cmllamas@...gle.com>,
	Suren Baghdasaryan <surenb@...gle.com>, Burak Emir <bqe@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>, 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>,
	Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/6] rust: bitmap: add MAX_LEN and NO_ALLOC_MAX_LEN
 constants

On Mon, Nov 10, 2025 at 10:01:32AM -0500, Yury Norov wrote:
> On Mon, Nov 10, 2025 at 02:20:17PM +0000, Alice Ryhl wrote:
> > On Mon, Nov 10, 2025 at 08:59:36AM -0500, Tamir Duberstein wrote:
> > > On Mon, Nov 10, 2025 at 8:06 AM Alice Ryhl <aliceryhl@...gle.com> wrote:
> > > >
> > > > To avoid hard-coding these values in drivers, define constants for them
> > > > that drivers can reference.
> > > >
> > > > Acked-by: Danilo Krummrich <dakr@...nel.org>
> > > > Reviewed-by: Burak Emir <bqe@...gle.com>
> > > > Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
> > > > ---
> > > >  rust/kernel/bitmap.rs | 16 +++++++++++-----
> > > >  1 file changed, 11 insertions(+), 5 deletions(-)
> > > >
> > > > diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs
> > > > index aa8fc7bf06fc99865ae755d8694e4bec3dc8e7f0..15fa23b45054b9272415fcc000e3e3b52c74d7c1 100644
> > > > --- a/rust/kernel/bitmap.rs
> > > > +++ b/rust/kernel/bitmap.rs
> > > > @@ -149,14 +149,14 @@ macro_rules! bitmap_assert_return {
> > > >  ///
> > > >  /// # Invariants
> > > >  ///
> > > > -/// * `nbits` is `<= i32::MAX` and never changes.
> > > > +/// * `nbits` is `<= MAX_LEN`.
> > > >  /// * if `nbits <= bindings::BITS_PER_LONG`, then `repr` is a `usize`.
> > > 
> > > Should this and other references to bindings::BITS_PER_LONG be
> > > `NO_ALLOC_MAX_LEN` instead?
> > 
> > Ah yeah it probably makes sense to update this in a bunch of places.
> 
> Yes, please. 
> 
> NO_ALLOC sounds a bit weird in exported API. Maybe NBITS_INPLACE
> or similar?

You add a 'new_inline()' constructor in this series, so this parameter
should be LEN_INLINE or NBITS_INLINE, like that.
 
> Also, at this point we're really close to:
> 
>    pub const NBITS_INPLACE: usize = CONFIG_NBITS_INPLACE;
> 
>    union BitmapRepr {
>        bitmap: [usize, BITS_TO_LONGS(NBITS_INPLACE)]
>        ptr: NonNull<usize>,
>    }
> 
> That would be a very useful addition for some particular scenarios,
> I believe. Even if you don't want to make it configurable, let's
> keep this option in mind?
> 
> Thanks,
> Yury