linux-kernel - Re: [PATCH] rust: fix regexp in scripts/is_rust

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Date:   Mon, 13 Feb 2023 16:01:05 +0100
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Eric Curtin <ecurtin@...hat.com>, Daniel Xu <dxu@...uu.xyz>,
        Martin Reboredo <yakoyoku@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        bjorn3_gh@...tonmail.com, rust-for-linux@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: fix regexp in scripts/is_rust_module.sh

On Mon, Feb 13, 2023 at 02:19:38PM +0100, Miguel Ojeda wrote:
> On Fri, Feb 10, 2023 at 4:26 PM Andrea Righi <andrea.righi@...onical.com> wrote:
> >
> > nm can use "R" or "r" to show read-only data sections, but
> > scripts/is_rust_module.sh can only recognize "r", so with some versions
> > of binutils it can fail to detect if a module is a Rust module or not.
> 
> Do you know which versions? If so, it would be nice to document it here.
> 
> > Moreover, with this patch applied I can also relax the constraint of
> > "RUST depends on !DEBUG_INFO_BTF" and build a kernel with Rust and BTF
> > enabled at the same time (of course BTF generation is still skipped for
> > Rust modules).
> 
> Even if that build succeeds, can you load the modules? i.e. the
> constraint was there due to
> https://github.com/Rust-for-Linux/linux/issues/735.

This patch simply fixes scripts/is_rust_module.sh to recognize Rust
modules from "regular" C modules with certain versions of binutils, so
that BTF generation is properly skipped for Rust modules.

In this way both C and Rust modules can be loaded correctly (at least in
my tests I'm able load both with CONFIG_DEBUG_INFO_BTF enabled).

I haven't dropped the "RUST depends on !DEBUG_INFO_BTF" yet, but I think
with this fix is applied we can relax this constraint.

-Andrea

> 
> Also Cc'ing Daniel, Eric and Martin since they are the ones working on this.
> 
> Cheers,
> Miguel