On 5/10/25 23:01, Kent Overstreet wrote:
> Static keys can now be a module parameter, e.g.
>
> module_param_named(foo, foo.key, static_key_t, 0644)
>
> bcachefs is now using this.
>
> Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
> Cc: Petr Pavlu <petr.pavlu@xxxxxxxx>
> Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> Cc: Daniel Gomez <da.gomez@xxxxxxxxxxx>
> Cc: linux-modules@xxxxxxxxxxxxxxx
Please Cc also the "STATIC BRANCH/CALL" folks on the next version.
> Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
> ---
> include/linux/jump_label.h | 2 ++
> include/linux/moduleparam.h | 6 ++++++
> kernel/params.c | 35 +++++++++++++++++++++++++++++++++++
> 3 files changed, 43 insertions(+)
>
> diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
> index fdb79dd1ebd8..0fc9b71db56f 100644
> --- a/include/linux/jump_label.h
> +++ b/include/linux/jump_label.h
> @@ -107,6 +107,8 @@ struct static_key {
> #endif /* CONFIG_JUMP_LABEL */
> };
>
> +typedef struct static_key static_key_t;
> +
> #endif /* __ASSEMBLY__ */
>
> #ifdef CONFIG_JUMP_LABEL
> diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
> index bfb85fd13e1f..2494e7e67453 100644
> --- a/include/linux/moduleparam.h
> +++ b/include/linux/moduleparam.h
The module_param() macro in this file has a kernel-doc that describes
all currently supported standard types:
* Standard types are:
* byte, hexint, short, ushort, int, uint, long, ulong
* charp: a character pointer
* bool: a bool, values 0/1, y/n, Y/N.
* invbool: the above, only sense-reversed (N = true).
The static_key_t should be added to this list.
> @@ -488,6 +488,12 @@ extern int param_set_bint(const char *val, const struct kernel_param *kp);
> #define param_get_bint param_get_int
> #define param_check_bint param_check_int
>
> +/* A static key, which can only be set like a bool */
> +extern const struct kernel_param_ops param_ops_static_key_t;
> +extern int param_set_static_key_t(const char *val, const struct kernel_param *kp);
> +extern int param_get_static_key_t(char *buffer, const struct kernel_param *kp);
> +#define param_check_static_key_t(name, p) __param_check(name, p, struct static_key)
> +
> /**
> * module_param_array - a parameter which is an array of some type
> * @name: the name of the array variable
> diff --git a/kernel/params.c b/kernel/params.c
> index 2509f216c9f3..991f49e138e7 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -14,6 +14,7 @@
> #include <linux/overflow.h>
> #include <linux/security.h>
> #include <linux/slab.h>
> +#include <linux/static_key.h>
> #include <linux/string.h>
>
> #ifdef CONFIG_SYSFS
> @@ -412,6 +413,40 @@ const struct kernel_param_ops param_ops_bint = {
> };
> EXPORT_SYMBOL(param_ops_bint);
>
> +int param_set_static_key_t(const char *val, const struct kernel_param *kp)
> +{
> + /* Match bool exactly, by re-using it. */
> + struct kernel_param boolkp = *kp;
> + bool v;
> + int ret;
> +
> + boolkp.arg = &v;
> +
> + ret = param_set_bool(val, &boolkp);
> + if (ret)
> + return ret;
> + if (v)
> + static_key_enable(kp->arg);
> + else
> + static_key_disable(kp->arg);
> + return 0;
> +}
> +EXPORT_SYMBOL(param_set_static_key_t);
> +
> +int param_get_static_key_t(char *buffer, const struct kernel_param *kp)
> +{
> + struct static_key *key = kp->arg;
> + return sprintf(buffer, "%c\n", static_key_enabled(key) ? 'N' : 'Y');
The 'N'/'Y' values are the other way around.
> +}
> +EXPORT_SYMBOL(param_get_static_key_t);
> +
> +const struct kernel_param_ops param_ops_static_key_t = {
> + .flags = KERNEL_PARAM_OPS_FL_NOARG,
> + .set = param_set_static_key_t,
> + .get = param_get_static_key_t,
> +};
> +EXPORT_SYMBOL(param_ops_static_key_t);
> +
> /* We break the rule and mangle the string. */
> static int param_array(struct module *mod,
> const char *name,
--
Thanks
Petr
