xstate -> exit_code

os/src/syscall/process.rs

@@ -1,6 +1,6 @@
 use crate::batch::run_next_app;
 
 pub fn sys_exit(exit_code: i32) -> ! {
-    println!("[kernel] Application exited with code {}", xstate);
+    println!("[kernel] Application exited with code {}", exit_code);
     run_next_app()
 }