linux-kernel - Re: [PATCH 08/46] static_call, lto: Mark static keys as _

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Message-ID: <20221114185718.kladzjm4ulcnq7bj@treble>
Date:   Mon, 14 Nov 2022 10:57:18 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Jason Baron <jbaron@...mai.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Martin Liska <mliska@...e.cz>, Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH 08/46] static_call, lto: Mark static keys as __visible

On Mon, Nov 14, 2022 at 12:43:06PM +0100, Jiri Slaby (SUSE) wrote:
> From: Andi Kleen <andi@...stfloor.org>
> 
> Symbols referenced from assembler (either directly or e.f. from
> DEFINE_STATIC_KEY()) need to be global and visible in gcc LTO because
> they could end up in a different object file than the assembler. This
> can lead to linker errors without this patch.
> 
> So mark static call functions as __visible, namely static keys here.
> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Josh Poimboeuf <jpoimboe@...nel.org>
> Cc: Jason Baron <jbaron@...mai.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ard Biesheuvel <ardb@...nel.org>
> Signed-off-by: Andi Kleen <andi@...stfloor.org>
> Signed-off-by: Martin Liska <mliska@...e.cz>
> Signed-off-by: Jiri Slaby <jslaby@...e.cz>
> ---
>  include/linux/static_call.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/static_call.h b/include/linux/static_call.h
> index df53bed9d71f..e629ab0c4ca3 100644
> --- a/include/linux/static_call.h
> +++ b/include/linux/static_call.h
> @@ -182,7 +182,7 @@ extern long __static_call_return0(void);
>  
>  #define DEFINE_STATIC_CALL(name, _func)					\
>  	DECLARE_STATIC_CALL(name, _func);				\
> -	struct static_call_key STATIC_CALL_KEY(name) = {		\
> +	__visible struct static_call_key STATIC_CALL_KEY(name) = {		\

Why not __visible_on_lto?

-- 
Josh