linux-kernel - Re: [PATCH] rust: kbuild: Don't export _

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Message-ID: <CANiq72mrteWUqCPBP=hULfiaPh2US+x-O4hg_K8Ljb6t9fdUkw@mail.gmail.com>
Date: Tue, 8 Apr 2025 21:50:38 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: kbuild: Don't export __pfx symbols

On Wed, Mar 19, 2025 at 12:18 AM Sami Tolvanen <samitolvanen@...gle.com> wrote:
>
> With CONFIG_PREFIX_SYMBOLS, objtool adds __pfx prefix symbols
> to claim the compiler emitted call padding bytes. When
> CONFIG_X86_KERNEL_IBT is not selected, the symbols are added to
> individual object files and for Rust objects, they end up being
> exported, resulting in warnings with CONFIG_GENDWARFKSYMS as the
> symbols have no debugging information:
>
> warning: gendwarfksyms: symbol_print_versions: no information for symbol __pfx_rust_helper_put_task_struct
> warning: gendwarfksyms: symbol_print_versions: no information for symbol __pfx_rust_helper_task_euid
> warning: gendwarfksyms: symbol_print_versions: no information for symbol __pfx_rust_helper_readq_relaxed
> ...
>
> Filter out the __pfx prefix from exported symbols similarly to
> the existing __cfi and __odr_asan prefixes.
>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>

Applied to `rust-fixes` -- thanks everyone!

It also gets rid of a lot of `modpost` warnings too at link time.

    Cc: stable@...r.kernel.org
    Fixes: ac61506bf2d1 ("rust: Use gendwarfksyms + extended
modversions for CONFIG_MODVERSIONS")

Thanks!

Cheers,
Miguel