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

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Message-ID: <20260127221531.GC3382807@ax162>
Date: Tue, 27 Jan 2026 15:15:31 -0700
From: Nathan Chancellor <nathan@...nel.org>
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>, 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 Tue, Jan 27, 2026 at 05:11:04PM +0000, 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
> 
> Signed-off-by: Gary Guo <gary@...yguo.net>

Acked-by: Nathan Chancellor <nathan@...nel.org>

Is the limit customizable?

> ---
>  scripts/Makefile.warn | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/scripts/Makefile.warn b/scripts/Makefile.warn
> index 5567da6c7dfe..254a4d53f8f3 100644
> --- a/scripts/Makefile.warn
> +++ b/scripts/Makefile.warn
> @@ -23,6 +23,7 @@ KBUILD_CFLAGS += -Wmissing-prototypes
>  
>  ifneq ($(CONFIG_FRAME_WARN),0)
>  KBUILD_CFLAGS += -Wframe-larger-than=$(CONFIG_FRAME_WARN)
> +KBUILD_RUSTFLAGS += -Wklint::stack-frame-too-large
>  endif
>  
>  KBUILD_CFLAGS-$(CONFIG_CC_NO_ARRAY_BOUNDS) += -Wno-array-bounds
> -- 
> 2.51.2
>