diff --git a/pintos-env/pintos/threads/thread.c b/pintos-env/pintos/threads/thread.c
index 62424df..e3ff6b6 100644
--- a/pintos-env/pintos/threads/thread.c
+++ b/pintos-env/pintos/threads/thread.c
@@ -575,6 +575,7 @@ init_thread (struct thread *t, const char *name, int priority)
   strlcpy (t->name, name, sizeof t->name);
   t->stack = (uint8_t *) t + PGSIZE;
   sema_init(&t->waiting_sem, 0);
+  t->waited_on_before = 0;
 
   if (thread_mlfqs) {
     t->nice_init = priority > 20 || priority < 20 ? 0 : priority;
diff --git a/pintos-env/pintos/threads/thread.h b/pintos-env/pintos/threads/thread.h
index dcebaaf..8d61d67 100755
--- a/pintos-env/pintos/threads/thread.h
+++ b/pintos-env/pintos/threads/thread.h
@@ -101,6 +101,8 @@ struct thread
     int nice_init;
     FPReal recent_cpu;
     struct semaphore waiting_sem;
+    int exit_status;
+    int waited_on_before;
 
 #ifdef USERPROG
     /* Owned by userprog/process.c. */
diff --git a/pintos-env/pintos/userprog/filesys.dsk b/pintos-env/pintos/userprog/filesys.dsk
new file mode 100644
index 0000000..14f36e6
Binary files /dev/null and b/pintos-env/pintos/userprog/filesys.dsk differ
diff --git a/pintos-env/pintos/userprog/process.c b/pintos-env/pintos/userprog/process.c
index 3f0bf7d..63b1286 100755
--- a/pintos-env/pintos/userprog/process.c
+++ b/pintos-env/pintos/userprog/process.c
@@ -179,13 +179,21 @@ start_process (void *file_name_)
 int
 process_wait (tid_t child_tid) 
 {
+  //printf("process wait for: %s on: %ul\n", thread_current()->name, child_tid);
+  
+  // TODO: check if tid is child
+  
   struct thread* child = thread_get_by_tid(child_tid);
-  if (child == NULL) {
+  if (child == NULL || child->waited_on_before) {
+    //printf("child not found\n");
     return -1;
   }
 
+  //printf("child is: %s\n", child->name);
+
   sema_down(&child->waiting_sem);
-  return 0;
+  child->waited_on_before = 1;
+  return child->exit_status;
 }
 
 /* Free the current process's resources. */
diff --git a/pintos-env/pintos/userprog/syscall.c b/pintos-env/pintos/userprog/syscall.c
index 2885f78..a0deea0 100755
--- a/pintos-env/pintos/userprog/syscall.c
+++ b/pintos-env/pintos/userprog/syscall.c
@@ -4,12 +4,17 @@
 #include "threads/interrupt.h"
 #include "threads/thread.h"
 #include <string.h>
+#include "userprog/process.h"
+#include "threads/vaddr.h"
+#include "userprog/pagedir.h"
 
 typedef int (*handler) (uint32_t, uint32_t, uint32_t);
 static handler syscall_vec[128];
 
 static int sys_write (int fd, const void *buffer, unsigned length);
 static int sys_exit (int status);
+static int sys_wait (tid_t tid);
+static tid_t sys_exec (const char* file_name);
 static void syscall_nop(void);
 
 static void syscall_handler (struct intr_frame *);
@@ -18,9 +23,11 @@ void
 syscall_init (void) 
 {
   intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
-
+printf("syscall\n");
   memset(syscall_vec, (int)&syscall_nop, 128);
   syscall_vec[SYS_EXIT] = (handler)sys_exit;
+  syscall_vec[SYS_WAIT] = (handler)sys_wait;
+  syscall_vec[SYS_EXEC] = (handler)sys_exec;
   syscall_vec[SYS_WRITE] = (handler)sys_write;
 }
 
@@ -58,6 +65,24 @@ sys_exit (int status)
 {
   struct thread* t = thread_current();
   printf("%s: exit(%d)\n", t->name, status);
+  t->exit_status = status;
   thread_exit ();
   return -1;
+}
+
+int
+sys_wait (tid_t tid)
+{
+  printf("system call wait\n");
+  return process_wait(tid);
+}
+
+tid_t
+sys_exec (const char* file_name) {
+  if (file_name == NULL || is_kernel_vaddr(file_name) || 
+      pagedir_get_page(thread_current()->pagedir, file_name) == NULL) {
+    return -1;
+  }
+
+  return process_execute(file_name);
 }
\ No newline at end of file