linux-kernel - Re: [PATCH] uaccess: decouple INLINE_COPY_FROM_USER and CONFIG

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Message-ID: <aPtDGA0JjmfDvxXd@google.com>
Date: Fri, 24 Oct 2025 09:12:56 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: "Yury Norov (NVIDIA)" <yury.norov@...il.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, 
	Danilo Krummrich <dakr@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Arnd Bergmann <arnd@...db.de>, Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>, 
	John Hubbard <jhubbard@...dia.com>, 
	"Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>, 
	Andreas Hindborg <a.hindborg@...nel.org>, Trevor Gross <tmgross@...ch.edu>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] uaccess: decouple INLINE_COPY_FROM_USER and CONFIG_RUST

On Thu, Oct 23, 2025 at 01:16:06PM -0400, Yury Norov (NVIDIA) wrote:
> Commit 1f9a8286bc0c ("uaccess: always export _copy_[from|to]_user with
> CONFIG_RUST") exports _copy_{from,to}_user() unconditionally, if RUST
> is enabled. This pollutes exported symbols namespace, and spreads RUST
> ifdefery in core files.
> 
> It's better to declare a corresponding helper under the rust/helpers,
> similarly to how non-underscored copy_{from,to}_user() is handled.
> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>

Overall LGTM:
Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Tested-by: Alice Ryhl <aliceryhl@...gle.com>


In include/linux/uaccess.h there is the comment:

	Rust code always uses the extern definition.

I think we should reword this comment as part of this change. You can
say that Rust accesses _inline_copy_from_user() through a helper, or
similar.

After all, when using LTO or other mechanism to inline helpers, it is no
longer the case that Rust always uses the a function call.

Alice