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

src/threads/thread.c

@@ -238,6 +238,7 @@ thread_create (const char *name, int priority,
   struct thread *parent_thread = thread_current ();
   init_thread (t, name, parent_thread->nice, priority, parent_thread->recent_cpu);
   tid = t->tid = allocate_tid ();
+  hash_init (&t->open_files, fd_hash, fd_less, NULL);
 
   /* Prepare thread for first run by initializing its stack.
      Do this atomically so intermediate values for the 'stack' 
@@ -662,7 +663,6 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->priority = t->base_priority;
 
   t->exit_status = -1;
-  hash_init (&t->open_files, fd_hash, fd_less, NULL);
 
   old_level = intr_disable ();
   list_push_back (&all_list, &t->allelem);

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"
@@ -12,6 +13,7 @@
 #include <syscall-nr.h>
 
 static struct lock filesys_lock;
+static unsigned fd_counter = MIN_USER_FD;
 
 struct open_file
   {
@@ -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

src/userprog/syscall.h

@@ -3,6 +3,8 @@
 
 #include <hash.h>
 
+#define MIN_USER_FD 2
+
 typedef int pid_t;
 
 void syscall_init (void);