Implement syscall for file creation, with relevant locks w/ S.

src/userprog/syscall.c

@@ -1,14 +1,18 @@
 #include "userprog/syscall.h"
 #include "devices/shutdown.h"
 #include "devices/input.h"
+#include "filesys/filesys.h"
 #include "threads/vaddr.h"
 #include "threads/interrupt.h"
 #include "threads/thread.h"
+#include "threads/synch.h"
 #include "userprog/process.h"
 #include "userprog/pagedir.h"
 #include <stdio.h>
 #include <syscall-nr.h>
 
+static struct lock filesys_lock;
+
 static void syscall_handler (struct intr_frame *);
 
 /* A syscall_function is a function that receives up to 3 arguments, the
@@ -68,6 +72,7 @@ void
 syscall_init (void) 
 {
   intr_register_int (0x30, 3, INTR_ON, syscall_handler, "syscall");
+  lock_init (&filesys_lock);
 }
 
 static void
@@ -126,8 +131,13 @@ syscall_wait (pid_t pid)
 static bool
 syscall_create (const char *file UNUSED, unsigned initial_size UNUSED)
 {
-  //TODO
-  return 0;
+  validate_user_pointer (file, 1);
+
+  lock_acquire (&filesys_lock);
+  bool status = filesys_create (file, initial_size);
+  lock_release (&filesys_lock);
+
+  return status;
 }
 
 static bool