module: Restore the moduleparam prefix length check

[ Upstream commit bdc877ba6b7ff1b6d2ebeff11e63da4a50a54854 ]

The moduleparam code allows modules to provide their own definition of
MODULE_PARAM_PREFIX, instead of using the default KBUILD_MODNAME ".".

Commit 730b69d2 ("module: check kernel param length at compile time,
not runtime") added a check to ensure the prefix doesn't exceed
MODULE_NAME_LEN, as this is what param_sysfs_builtin() expects.

Later, commit 58f86cc8 ("VERIFY_OCTAL_PERMISSIONS: stricter checking
for sysfs perms.") removed this check, but there is no indication this was
intentional.

Since the check is still useful for param_sysfs_builtin() to function
properly, reintroduce it in __module_param_call(), but in a modernized form
using static_assert().

While here, clean up the __module_param_call() comments. In particular,
remove the comment "Default value instead of permissions?", which comes
from commit 9774a1f5 ("[PATCH] Compile-time check re world-writeable
module params"). This comment was related to the test variable
__param_perm_check_##name, which was removed in the previously mentioned
commit 58f86cc8.

Fixes: 58f86cc8 ("VERIFY_OCTAL_PERMISSIONS: stricter checking for sysfs perms.")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Reviewed-by: Daniel Gomez <da.gomez@samsung.com>
Link: https://lore.kernel.org/r/20250630143535.267745-4-petr.pavlu@suse.com


Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>