Re: [PATCH v12 07/12] static_call: Define EXPORT_STATIC_CALL_FOR_MODULES()

[Sean Christopherson]

 On Tue, Jun 23, 2026, Pawan Gupta wrote:
> There is EXPORT_STATIC_CALL_TRAMP() that hides the static key from all
> modules. But there is no equivalent of EXPORT_SYMBOL_FOR_MODULES() to
> restrict symbol visibility to only certain modules.
> 
> Add EXPORT_STATIC_CALL_FOR_MODULES(name, mods) that wraps both the key and
> the trampoline with EXPORT_SYMBOL_FOR_MODULES(), allowing only a limited
> set of modules to see and update the static key.
> 
> The immediate user is KVM, in the following commit.
> 
> checkpatch reported below warnings with this change that I believe don't
> apply in this case:
> 
>   include/linux/static_call.h:219: WARNING: Non-declarative macros with multiple statements should be enclosed in a do - while loop
>   include/linux/static_call.h:220: WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable
> 
> Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx>
> ---
>  include/linux/static_call.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/include/linux/static_call.h b/include/linux/static_call.h
> index 78a77a4ae0ea..b610afd1ed55 100644
> --- a/include/linux/static_call.h
> +++ b/include/linux/static_call.h
> @@ -216,6 +216,9 @@ extern long __static_call_return0(void);
>  #define EXPORT_STATIC_CALL_GPL(name)					\
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
> +#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
> +	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods);		\
> +	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_TRAMP(name), mods)
>  
>  /* Leave the key unexported, so modules can't change static call targets: */
>  #define EXPORT_STATIC_CALL_TRAMP(name)					\
> @@ -276,6 +279,9 @@ extern long __static_call_return0(void);
>  #define EXPORT_STATIC_CALL_GPL(name)					\
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
>  	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
> +#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
> +	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods);		\
> +	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_TRAMP(name), mods)
>  
>  /* Leave the key unexported, so modules can't change static call targets: */
>  #define EXPORT_STATIC_CALL_TRAMP(name)					\
> @@ -346,6 +352,8 @@ static inline int static_call_text_reserved(void *start, void *end)
>  
>  #define EXPORT_STATIC_CALL(name)	EXPORT_SYMBOL(STATIC_CALL_KEY(name))
>  #define EXPORT_STATIC_CALL_GPL(name)	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name))
> +#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
> +	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods)
>  
>  #endif /* CONFIG_HAVE_STATIC_CALL */

Drat, I forgot about this.  Exporting static call trampolines for KVM came up in
another conversation[*].  I had already put together patches to effectively default
to exporting only the trampoline, and also to deduplicate this code so that the
CONFIG_HAVE_STATIC_CALL_INLINE=y / CONFIG_HAVE_STATIC_CALL=y / CONFIG_HAVE_STATIC_CALL=n
implementations don't need to copy+paste the same lines of code.

The attached patches touch a lot more code, and will conflict mightily with KVM
changes I want to land in 7.3 (more use of a static_call in KVM).  But if we get
them applied (to tip tree) shortly after 7.2-rc1 and provide a topic branch/tag,
then there shouldn't be too much juggling needed?

If we want to go with the more aggressive cleanup, I'll formally post the patches.

[*] https://lore.kernel.org/all/ahhoDGUz39KSGZ6o@xxxxxxxxxx