logging: bugfix #137: Init log module to enable logging macros

Author: wyfcyx

os/src/logging.rs

@@ -42,6 +42,6 @@ pub fn init() {
         Some("INFO") => LevelFilter::Info,
         Some("DEBUG") => LevelFilter::Debug,
         Some("TRACE") => LevelFilter::Trace,
-        _ => LevelFilter::Off,
+        _ => LevelFilter::Info,
     });
 }