Implement syscall for file opening and refactor open_files initialisation in thread.c w/ S.

src/userprog/syscall.c

@@ -4,6 +4,7 @@
 #include "filesys/filesys.h"
 #include "threads/vaddr.h"
 #include "threads/interrupt.h"
+#include "threads/malloc.h"
 #include "threads/thread.h"
 #include "threads/synch.h"
 #include "userprog/process.h"
@@ -12,11 +13,12 @@
 #include <syscall-nr.h>
 
 static struct lock filesys_lock;
+static unsigned fd_counter = MIN_USER_FD;
 
 struct open_file
   {
-    int fd;              /* File Descriptor / Identifier */
-    struct file *file;   /* Pointer to the associated file */
+    int fd;                     /* File Descriptor / Identifier */
+    struct file *file;          /* Pointer to the associated file */
     struct hash_elem elem;      /* elem for a hash table */
   };
 
@@ -165,10 +167,27 @@ syscall_remove (const char *file)
 }
 
 static int
-syscall_open (const char *file UNUSED)
+syscall_open (const char *file)
 {
-  //TODO
-  return 0;
+  validate_user_pointer (file, 1);
+
+  lock_acquire (&filesys_lock);
+  struct file *ptr = filesys_open (file);
+  lock_release (&filesys_lock);
+  if (ptr == NULL)
+    return -1;
+
+  struct open_file *file_info
+    = (struct open_file*) malloc (sizeof (struct open_file));
+  if (file_info == NULL)
+    return -1;
+
+  file_info->fd = fd_counter++;
+  file_info->file = ptr;
+
+  hash_insert (&thread_current ()->open_files, &file_info->elem);
+
+  return file_info->fd;
 }
 
 static int