update lab1-8 codes and docs. now version is 0.2

code/lab6/user/libs/syscall.c

@@ -70,7 +70,7 @@ sys_pgdir(void) {
     return syscall(SYS_pgdir);
 }
 
-size_t
+int
 sys_gettime(void) {
     return syscall(SYS_gettime);
 }

code/lab6/user/libs/syscall.h

@@ -9,6 +9,7 @@ int sys_kill(int pid);
 int sys_getpid(void);
 int sys_putc(int c);
 int sys_pgdir(void);
+int sys_gettime(void);
 /* FOR LAB6 ONLY */
 void sys_lab6_set_priority(uint32_t priority);