linux-kernel - Re: [RFC PATCH 2/2] kbuild: rust: use klint to provide CONFIG_FRAME

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Message-Id: <DFZSRE43IHOU.2OZNE9IFIO3UB@nvidia.com>
Date: Wed, 28 Jan 2026 09:31:02 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "Gary Guo" <gary@...nel.org>
Cc: "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>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Danilo Krummrich" <dakr@...nel.org>,
 "Nathan Chancellor" <nathan@...nel.org>, "Nicolas Schier" <nsc@...nel.org>,
 Thomas Weißschuh <linux@...ssschuh.net>, "Masahiro Yamada"
 <masahiroy@...nel.org>, "Kees Cook" <kees@...nel.org>,
 <rust-for-linux@...r.kernel.org>, <linux-kbuild@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 2/2] kbuild: rust: use klint to provide
 CONFIG_FRAME_WARN

On Wed Jan 28, 2026 at 2:11 AM JST, Gary Guo wrote:
> From: Gary Guo <gary@...yguo.net>
>
> klint is able to analyze frame size and warn on frames that are too big.
>
> With `register_tool(klint)` support, we can simply instruct rust to turn on
> `klint::stack_frame_too_large`. This is a no-op if normal rustc (or Clippy)
> is invoked, but will perform the check if klint is used.
>
> This is an example of a bug caught using this option:
>
> warning: stack size of `gsp::cmdq::Cmdq::new` is 8216 bytes, exceeds the 2048-byte limit
>    --> drivers/gpu/nova-core/gsp/cmdq.rs:453:5
>     |
> 453 |     pub(crate) fn new(dev: &device::Device<device::Bound>) -> Result<Cmdq> {
>     |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>     |
>     = note: the stack size is inferred from instruction `sub $0x2018,%rsp` at .text+32778

Initially this error puzzled me a bit since the objects directly built
by Cmdq::new are not larger than ~40 bytes, but then I dug into the
constructors it called and found that `PteArray`, a large struct, is
built on the stack! We need to convert it to an `Init` I guess.

Super valuable tool!