diff --git a/src/threads/thread.h b/src/threads/thread.h
index 60f91ce..f031981 100644
--- a/src/threads/thread.h
+++ b/src/threads/thread.h
@@ -143,9 +143,7 @@ struct thread
     struct hash open_files;             /* Hash Table of FD -> Struct File. */
 #endif
 
-#ifdef VM
     void *curr_esp;
-#endif
 
     /* Owned by thread.c. */
     unsigned magic;                     /* Detects stack overflow. */
diff --git a/src/userprog/Make.vars b/src/userprog/Make.vars
index e4dbb08..23bae3d 100644
--- a/src/userprog/Make.vars
+++ b/src/userprog/Make.vars
@@ -1,7 +1,7 @@
 # -*- makefile -*-
 
-kernel.bin: DEFINES = -DUSERPROG -DFILESYS
-KERNEL_SUBDIRS = threads devices lib lib/kernel userprog filesys
+kernel.bin: DEFINES = -DUSERPROG -DFILESYS -DVM
+KERNEL_SUBDIRS = threads devices lib lib/kernel userprog filesys vm
 TEST_SUBDIRS = tests/userprog tests/userprog/no-vm tests/filesys/base
 GRADING_FILE = $(SRCDIR)/tests/userprog/Grading
 SIMULATOR = --qemu
diff --git a/src/userprog/exception.c b/src/userprog/exception.c
index 3e3b133..1fcbe61 100644
--- a/src/userprog/exception.c
+++ b/src/userprog/exception.c
@@ -146,19 +146,19 @@ page_fault (struct intr_frame *f)
   write = (f->error_code & PF_W) != 0;
   user = (f->error_code & PF_U) != 0;
 
-  /* Kernel page fault is further handled by the kernel itself. */
-  if (kernel)
+  if (user && not_present)
     {
-      f->eip = (void *)f->eax;
+  	  if (try_alloc_new_page (fault_addr, f->esp))
+        return;
+    }
+  else
+    {
+      if (try_alloc_new_page (fault_addr, thread_current ()->curr_esp))
+        return;
+	  f->eip = (void *)f->eax;
       f->eax = 0xffffffff;
       return;
-    }
-
-   if (user)
-     {
-       if (try_alloc_new_page (fault_addr, f->esp))
-        return;
-     }
+	}
 
   /* To implement virtual memory, delete the rest of the function
      body, and replace it with code that brings in the page to
diff --git a/src/userprog/syscall.c b/src/userprog/syscall.c
index da6d77d..4bc34ca 100644
--- a/src/userprog/syscall.c
+++ b/src/userprog/syscall.c
@@ -10,9 +10,6 @@
 #include "threads/synch.h"
 #include "userprog/process.h"
 #include "userprog/pagedir.h"
-#ifdef VM
-#include "vm/stackgrowth.h"
-#endif
 #include <stdio.h>
 #include <stdbool.h>
 #include <syscall-nr.h>
@@ -465,17 +462,17 @@ validate_user_pointer (const void *ptr, size_t size, bool check_write)
      valid user virtual memory address. */
   void *last = ptr + size - 1;
   if (!is_user_vaddr (last))
-    thread_exit ();
+    syscall_exit (EXIT_FAILURE);
   ptr = pg_round_down (ptr);
   while (ptr <= last)
     {
       int result;
       /* Check read access to pointer. */
       if ((result = get_user (ptr)) == -1)
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       /* Check write access to pointer (if required). */
       if (check_write && !put_user (ptr, result))
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       ptr += PGSIZE;
     }
 }
@@ -485,18 +482,33 @@ validate_user_pointer (const void *ptr, size_t size, bool check_write)
 static void
 validate_user_string (const char *ptr, bool check_write)
 {
-  while (true)
+  size_t offset = (uintptr_t) ptr % PGSIZE;
+
+  for (;;)
     {
+      void *page = pg_round_down (ptr);
+
+      if (!is_user_vaddr (page))
+        syscall_exit (EXIT_FAILURE);
       if (!is_user_vaddr (ptr))
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       int result;
       if ((result = get_user ((const uint8_t *)ptr)) == -1)
-        thread_exit ();
+        syscall_exit (EXIT_FAILURE);
       if (check_write && !put_user ((uint8_t *)ptr, result))
-        thread_exit ();
-      if (*ptr == '\0')
-        return;
-      ptr++;
+        syscall_exit (EXIT_FAILURE);
+
+      while (offset < PGSIZE)
+      {
+        if (*ptr == '\0')
+          return; /* We reached the end of the string without issues. */
+
+        ptr++;
+        offset++;
+      }
+
+      offset = 0;
+
     }
 }