On 30/06/2025 16.32, Petr Pavlu wrote:
> The maximum module name length (MODULE_NAME_LEN) is somewhat confusingly
> defined in terms of the maximum parameter prefix length
> (MAX_PARAM_PREFIX_LEN), when in fact the dependency is in the opposite
> direction.
>
> This split originates from commit 730b69d22525 ("module: check kernel param
> length at compile time, not runtime"). The code needed to use
> MODULE_NAME_LEN in moduleparam.h, but because module.h requires
> moduleparam.h, this created a circular dependency. It was resolved by
> introducing MAX_PARAM_PREFIX_LEN in moduleparam.h and defining
> MODULE_NAME_LEN in module.h in terms of MAX_PARAM_PREFIX_LEN.
>
> Rename MAX_PARAM_PREFIX_LEN to __MODULE_NAME_LEN for clarity. This matches
> the similar approach of defining MODULE_INFO in module.h and __MODULE_INFO
> in moduleparam.h.
>
> Signed-off-by: Petr Pavlu <petr.pavlu@xxxxxxxx>
> ---
> include/linux/module.h | 2 +-
> include/linux/moduleparam.h | 12 ++++++++----
> 2 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/module.h b/include/linux/module.h
> index 5faa1fb1f4b4..0f1dde3996d9 100644
> --- a/include/linux/module.h
> +++ b/include/linux/module.h
> @@ -32,7 +32,7 @@
> #include <linux/percpu.h>
> #include <asm/module.h>
>
> -#define MODULE_NAME_LEN MAX_PARAM_PREFIX_LEN
> +#define MODULE_NAME_LEN __MODULE_NAME_LEN
>
> struct modversion_info {
> unsigned long crc;
> diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
> index 110e9d09de24..a04a2bc4f51e 100644
> --- a/include/linux/moduleparam.h
> +++ b/include/linux/moduleparam.h
> @@ -6,6 +6,13 @@
> #include <linux/stringify.h>
> #include <linux/kernel.h>
>
> +/*
> + * The maximum module name length, including the NUL byte.
> + * Chosen so that structs with an unsigned long line up, specifically
> + * modversion_info.
> + */
> +#define __MODULE_NAME_LEN (64 - sizeof(unsigned long))
> +
> /* You can override this manually, but generally this should match the
> module name. */
> #ifdef MODULE
> @@ -17,9 +24,6 @@
> #define __MODULE_INFO_PREFIX KBUILD_MODNAME "."
> #endif
>
> -/* Chosen so that structs with an unsigned long line up. */
> -#define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
> -
> #define __MODULE_INFO(tag, name, info) \
> static const char __UNIQUE_ID(name)[] \
> __used __section(".modinfo") __aligned(1) \
> @@ -284,7 +288,7 @@ struct kparam_array
>
> /* This is the fundamental function for registering boot/module parameters. */
> #define __module_param_call(prefix, name, ops, arg, perm, level, flags) \
> - static_assert(sizeof(""prefix) - 1 <= MAX_PARAM_PREFIX_LEN); \
> + static_assert(sizeof(""prefix) - 1 <= __MODULE_NAME_LEN); \
> static const char __param_str_##name[] = prefix #name; \
> static struct kernel_param __moduleparam_const __param_##name \
> __used __section("__param") \
LGTM,
Reviewed-by: Daniel Gomez <da.gomez@xxxxxxxxxxx>
