Doc and Makefile update

Makefile

@@ -17,7 +17,6 @@ dumps:
 
 user_lib:
 	$(MAKE) -C userlib/
-	mv ${TOPDIR}/userlib/sys.a ${TOPDIR}/src/sys.a
 
 tests: user_lib
 	$(MAKE) tests -C test/riscv_instructions/

userlib/syscall.rs

@@ -42,13 +42,17 @@ extern "C" {
     ///Stop Nachos, and print out performance stats
     fn Shutdown() -> ();
 
-    /// Return the time spent running Nachos
+    /// Return the time spent running BurritOS
+    /// ## Param
+    /// - **t** a struct to define the time unit
     fn SysTime(t: Burritos_Time) -> ();
 
-    /// This user program is done (status = 0 means exited normally).
+    /// This user program is done
+    /// ## Param
+    /// - **status** status at the end of execution *(status = 0 means exited normally)*.
     fn Exit(status: i32) -> ();
 
-    /// Run the executable, stored in the Nachos file "name", and return the
+    /// Run the executable, stored in the BurritOS file "name", and return the
     /// master thread identifier
     fn Exec(name: *const char) -> ThreadId;
 
@@ -159,7 +163,7 @@ extern "C" {
     fn CondBroadcast(id: CondId) -> t_error;
 
     ///////////////////////////////////////////////////////
-    /// System calls concerning serial port and console ///
+    /// # System calls concerning serial port and console
     ///////////////////////////////////////////////////////
 
     ///Send the message on the serial communication link.