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

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Message-ID: <aPuDAHzirb3Arl6h@yury>
Date: Fri, 24 Oct 2025 09:45:36 -0400
From: Yury Norov <yury.norov@...il.com>
To: Alice Ryhl <aliceryhl@...gle.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 Fri, Oct 24, 2025 at 09:12:56AM +0000, Alice Ryhl wrote:
> 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.

It is actually worth to just drop the rust part of the comment - with
this patch there's nothing special in managing the _copy_from_user().

I'll send v2. Thanks for review!

Thanks,
Yury