linux-kernel - Re: [PATCH v5 6/6] rust: use strict provenance APIs

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Message-ID: <67d8671d.050a0220.3305ab.6372@mx.google.com>
Date: Mon, 17 Mar 2025 11:16:58 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Danilo Krummrich <dakr@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,	linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org,	rust-for-linux@...r.kernel.org,
 linux-kselftest@...r.kernel.org,	kunit-dev@...glegroups.com,
 linux-pci@...r.kernel.org,	linux-block@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v5 6/6] rust: use strict provenance APIs

On Mon, Mar 17, 2025 at 02:10:42PM -0400, Tamir Duberstein wrote:
> On Mon, Mar 17, 2025 at 2:06 PM Boqun Feng <boqun.feng@...il.com> wrote:
> >
> > On Mon, Mar 17, 2025 at 02:04:34PM -0400, Tamir Duberstein wrote:
> > > On Mon, Mar 17, 2025 at 1:39 PM Boqun Feng <boqun.feng@...il.com> wrote:
> > > >
> > > > On Mon, Mar 17, 2025 at 10:23:56AM -0400, Tamir Duberstein wrote:
> > > > [...]
> > > > > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> > > > > index fc6835cc36a3..c1b274c04a0f 100644
> > > > > --- a/rust/kernel/lib.rs
> > > > > +++ b/rust/kernel/lib.rs
> > > > > @@ -17,6 +17,11 @@
> > > > >  #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(coerce_unsized))]
> > > > >  #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(dispatch_from_dyn))]
> > > > >  #![cfg_attr(not(CONFIG_RUSTC_HAS_COERCE_POINTEE), feature(unsize))]
> > > > > +#![cfg_attr(
> > > > > +    CONFIG_RUSTC_HAS_STABLE_STRICT_PROVENANCE,
> > > > > +    feature(strict_provenance_lints),
> > > > > +    deny(fuzzy_provenance_casts, lossy_provenance_casts)
> > > > > +)]
> > > > >  #![feature(inline_const)]
> > > > >  #![feature(lint_reasons)]
> > > > >  // Stable in Rust 1.83
> > > > > @@ -25,6 +30,109 @@
> > > > >  #![feature(const_ptr_write)]
> > > > >  #![feature(const_refs_to_cell)]
> > > > >
> > > > > +#[cfg(CONFIG_RUSTC_HAS_STABLE_STRICT_PROVENANCE)]
> > > > > +#[allow(clippy::incompatible_msrv)]
> > > > > +mod strict_provenance {
> > > > > +    /// Gets the "address" portion of the pointer.
> > > > > +    ///
> > > > > +    /// See https://doc.rust-lang.org/stable/core/primitive.pointer.html#method.addr.
> > > > > +    #[inline]
> > > > > +    pub fn addr<T>(ptr: *const T) -> usize {
> > > > > +        ptr.addr()
> > > > > +    }
> > > > > +
> > > >
> > > > For addr(), I would just enable feature(strict_provenance) if
> > > > CONFIG_RUSTC_HAS_STABLE_STRICT_PROVENANCE=n, because that feature is
> > > > available for 1.78. Plus we may need with_addr() or map_addr() in the
> > > > future.
> > >
> > > We still need these stubs to avoid `clippy::incompatible_msrv`, and
> > > we'll need those until MSRV is above 1.84.
> > >
> >
> > Hmm.. why? Clippy cannot work with unstable features?
> 
> Yes, `clippy::incompatible_msrv` doesn't pay attention to enabled
> unstable features.

Then we should fix clippy or how we set msrv rather adding the stub.
@Miguel?

Regards,
Boqun