Add /sys/module/*/import_ns to expose imported namespaces for currently loaded modules. The file contains one namespace per line and only exists for modules that import at least one namespace. Previously, the only way for userspace to inspect the symbol namespaces a module imports is to locate the .ko on disk and invoke modinfo(8) to decompress/parse the metadata. The kernel validated namespaces at load time, but it was otherwise discarded. Exposing this data via sysfs provides a runtime mechanism to verify which namespaces are being used by modules. For example, this allows userspace to audit driver API access in Android GKI, which uses symbol namespaces to restrict vendor drivers from using specific kernel interfaces (e.g., direct filesystem access). Signed-off-by: Nicholas Sielicki <linux@opensource.nslick.com> [Sami: Updated the commit message to explain motivation.] Signed-off-by: Sami Tolvanen <samitolvanen@google.com>