linux-kernel - Re: [PATCH v3 45/64] x86/static_call: Define ELF section entry size of static calls

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Message-ID: <20250627105125.GX1613200@noisy.programming.kicks-ass.net>
Date: Fri, 27 Jun 2025 12:51:25 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
	Petr Mladek <pmladek@...e.com>, Miroslav Benes <mbenes@...e.cz>,
	Joe Lawrence <joe.lawrence@...hat.com>,
	live-patching@...r.kernel.org, Song Liu <song@...nel.org>,
	laokz <laokz@...mail.com>, Jiri Kosina <jikos@...nel.org>,
	Marcos Paulo de Souza <mpdesouza@...e.com>,
	Weinan Liu <wnliu@...gle.com>,
	Fazla Mehrab <a.mehrab@...edance.com>,
	Chen Zhongjin <chenzhongjin@...wei.com>,
	Puranjay Mohan <puranjay@...nel.org>,
	Dylan Hatch <dylanbhatch@...gle.com>
Subject: Re: [PATCH v3 45/64] x86/static_call: Define ELF section entry size
 of static calls

On Thu, Jun 26, 2025 at 04:55:32PM -0700, Josh Poimboeuf wrote:
> In preparation for the objtool klp diff subcommand, define the entry
> size for the .static_call_sites section in its ELF header.  This will
> allow tooling to extract individual entries.
> 
> Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
> ---
>  arch/x86/include/asm/static_call.h      |  3 ++-
>  include/linux/static_call.h             |  6 ------
>  include/linux/static_call_types.h       |  6 ++++++
>  kernel/bounds.c                         |  4 ++++
>  tools/include/linux/static_call_types.h |  6 ++++++
>  tools/objtool/check.c                   | 11 +++++++++--
>  6 files changed, 27 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/x86/include/asm/static_call.h b/arch/x86/include/asm/static_call.h
> index 41502bd2afd6..e03ad9bbbf59 100644
> --- a/arch/x86/include/asm/static_call.h
> +++ b/arch/x86/include/asm/static_call.h
> @@ -58,7 +58,8 @@
>  	ARCH_DEFINE_STATIC_CALL_TRAMP(name, __static_call_return0)
>  
>  #define ARCH_ADD_TRAMP_KEY(name)					\
> -	asm(".pushsection .static_call_tramp_key, \"a\"		\n"	\
> +	asm(".pushsection .static_call_tramp_key, \"aM\", @progbits, "	\
> +	    __stringify(STATIC_CALL_TRAMP_KEY_SIZE) "\n"		\

More horrifically confusing indenting.

>  	    ".long " STATIC_CALL_TRAMP_STR(name) " - .		\n"	\
>  	    ".long " STATIC_CALL_KEY_STR(name) " - .		\n"	\
>  	    ".popsection					\n")