linux-kernel - Re: [PATCH 2/3] module: make structure definitions always visible

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Message-ID: <9e5669e5-fc7e-4297-b12f-ceb9dcf36d91@suse.com>
Date: Tue, 8 Jul 2025 11:39:41 +0200
From: Petr Pavlu <petr.pavlu@...e.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Cc: Luis Chamberlain <mcgrof@...nel.org>,
 Sami Tolvanen <samitolvanen@...gle.com>, Daniel Gomez
 <da.gomez@...sung.com>, Brendan Higgins <brendan.higgins@...ux.dev>,
 David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
 linux-modules@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com
Subject: Re: [PATCH 2/3] module: make structure definitions always visible

On 6/12/25 4:53 PM, Thomas Weißschuh wrote:
> To write code that works with both CONFIG_MODULES=y and CONFIG_MODULES=n
> it is convenient to use "if (IS_ENABLED(CONFIG_MODULES))" over raw #ifdef.
> The code will still fully typechecked but the unreachable parts are
> discarded by the compiler. This prevents accidental breakage when a certain
> kconfig combination was not specifically tested by the developer.
> This pattern is already supported to some extend by module.h defining
> empty stub functions if CONFIG_MODULES=n.
> However some users of module.h work on the structured defined by module.h.
> 
> Therefore these structure definitions need to be visible, too.
> 
> Many structure members are still gated by specific configuration settings.
> The assumption for those is that the code using them will be gated behind
> the same configuration setting anyways.
> 
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> ---
>  include/linux/module.h | 23 ++++++++++++-----------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 52f7b0487a2733c56e2531a434887e56e1bf45b2..7f783e71636542b99db3dd869a9387d14992df45 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -302,17 +302,6 @@ static typeof(name) __mod_device_table__##type##__##name		\
>  
>  struct notifier_block;
>  
> -#ifdef CONFIG_MODULES
> -
> -extern int modules_disabled; /* for sysctl */
> -/* Get/put a kernel symbol (calls must be symmetric) */
> -void *__symbol_get(const char *symbol);
> -void *__symbol_get_gpl(const char *symbol);
> -#define symbol_get(x)	({ \
> -	static const char __notrim[] \
> -		__used __section(".no_trim_symbol") = __stringify(x); \
> -	(typeof(&x))(__symbol_get(__stringify(x))); })
> -
>  enum module_state {
>  	MODULE_STATE_LIVE,	/* Normal state. */
>  	MODULE_STATE_COMING,	/* Full formed, running module_init. */
> @@ -598,6 +587,18 @@ struct module {
>  	struct _ddebug_info dyndbg_info;
>  #endif
>  } ____cacheline_aligned __randomize_layout;
> +
> +#ifdef CONFIG_MODULES
> +
> +extern int modules_disabled; /* for sysctl */
> +/* Get/put a kernel symbol (calls must be symmetric) */
> +void *__symbol_get(const char *symbol);
> +void *__symbol_get_gpl(const char *symbol);
> +#define symbol_get(x)	({ \
> +	static const char __notrim[] \
> +		__used __section(".no_trim_symbol") = __stringify(x); \
> +	(typeof(&x))(__symbol_get(__stringify(x))); })
> +
>  #ifndef MODULE_ARCH_INIT
>  #define MODULE_ARCH_INIT {}
>  #endif
> 

Nit: I suggest keeping MODULE_ARCH_INIT in its current position,
immediately after the 'struct module' declaration, because the macro is
directly tied to that structure.

-- 
Thanks,
Petr