linux-kernel - Re: [PATCH 00/15] Implement MODVERSIONS for Rust

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Date: Tue, 18 Jun 2024 16:32:34 -0700
From: Luis Chamberlain <mcgrof@...nel.org>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Kris Van Hees <kris.van.hees@...cle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Matthew Maurer <mmaurer@...gle.com>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	Gary Guo <gary@...yguo.net>, linux-kbuild@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 00/15] Implement MODVERSIONS for Rust

On Tue, Jun 18, 2024 at 02:19:47PM -0700, Sami Tolvanen wrote:
> Hi Luis,
> 
> On Tue, Jun 18, 2024 at 12:42:51PM -0700, Luis Chamberlain wrote:
> > a) Ensure correctness for all users / tools, so that proper plumbing is
> >    really done. By considering all symbols you increase your scope of
> >    awareness of anything that could really break.
> > 
> > b) Remove the "Rust" nature about this
> > 
> > c) Rust modules just becomes a *user* of this approach
> 
> I believe the only Rust nature here is the last patch that enables
> gendwarfksyms only for Rust. Otherwise, there shouldn't be anything
> strictly Rust specific.

Right now the check for length is generic, and assumes a hash may exist
without considering that check is moot for non-rust modules. So the
inverse is true, but doesn't provide a solution or proper architecture
for it.

> > It gets me wondering, given Kris is also working on allowing traces to
> > map symbols to module names, how does this fit into that world [0]?
> 
> AFAIK long symbol names are only a problem for struct modversion_info,
> which uses a relatively short name buffer, so I'm hoping other efforts
> won't be affected.

We'll see!

> > As for a) the reason I'm thinking about having the ability to test a
> > full real kernel and moules with this is, without that, how are you sure
> > you have the full scope of the changes needed?
> 
> Sure, I can look into hooking this up for the entire kernel and seeing
> what breaks, in addition the issues Masahiro pointed out, of course.

:) should be fun!

I think once its revised as a "generic" strategy and not a Rust one, the
proper architecture will be considered. Right now, it just looks like a
cheap band aid for Rust.

  Luis