linux-kernel - Re: [PATCH] objtool/rust: add one more `noreturn` Rust function

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Message-ID: <20251022081331.GJ4067720@noisy.programming.kicks-ass.net>
Date: Wed, 22 Oct 2025 10:13:31 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc: Gary Guo <gary@...yguo.net>, Miguel Ojeda <ojeda@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	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>, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
	stable@...r.kernel.org
Subject: Re: [PATCH] objtool/rust: add one more `noreturn` Rust function

On Tue, Oct 21, 2025 at 07:25:11PM +0200, Miguel Ojeda wrote:
> On Tue, Oct 21, 2025 at 7:19 PM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > I'll go stick it in tip/objtool/core; but I gotta ask, where are we with
> > the toolchain support for noreturn?
> 
> Thanks Peter!
> 
> We discussed it with upstream Rust, and they understood the need, so
> we may get something like `--emit=noreturn` or similar, but it is
> still open (and not too high in the priority list since we can survive
> with this for now and we have other things that we really need them to
> get stabilized etc. But if you feel it should be prioritized more,
> please let me know).

Nah, as long as its not forgotten I suppose it'll show up at some point.

I would place including C headers in Rust at a *MUCH* higher priority
than this. This bindgen nonsense is a giant pain in the arse.

> I have the status under "Export (somehow) a list of all noreturn symbols." at:
> 
>     https://github.com/Rust-for-Linux/linux/issues/355
> 
> In particular, Gary proposed an alternative during those discussions:
> 
>     "Gary proposed reading DWARF instead and wrote a quick Rust script
> for it via object and gimli, though DWARF would need to be available
> or generated on the fly just for that (and we cannot commit a fixed
> list since the kernel config may change and we support several Rust
> versions and so on):
> https://gist.github.com/nbdd0121/449692570622c2f46a29ad9f47c3379a."

Right, the problem with DWARF is that you need to have DWARF and debug
builds are *SLOW* :/ But perhaps rust compile times are such that that
isn't noticable?