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

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Message-ID: <67d85e51.050a0220.2a36b.58b3@mx.google.com>
Date: Mon, 17 Mar 2025 10:39:26 -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 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.

It saves the cost of maintaining our own *addr() and removing it when
we bump to a strict_provenance stablized version as minimal verision in
the future. Thoughts?

Regards,
Boqun

[...]
>  // Ensure conditional compilation based on the kernel configuration works;
>  // otherwise we may silently break things like initcall handling.
>  #[cfg(not(CONFIG_RUST))]
> diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
> index 40d1bd13682c..b70076d16008 100644
> --- a/rust/kernel/of.rs
> +++ b/rust/kernel/of.rs
> @@ -22,7 +22,7 @@ unsafe impl RawDeviceId for DeviceId {
>      const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::of_device_id, data);
>  
>      fn index(&self) -> usize {
> -        self.0.data as usize
> +        crate::addr(self.0.data)
>      }
>  }
>  
[...]