src/threads/thread.h

@@ -143,6 +143,10 @@ 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. */
   };

src/userprog/syscall.c

@@ -10,6 +10,9 @@
 #include "threads/synch.h"
 #include "userprog/process.h"
 #include "userprog/pagedir.h"
+#ifdef VM
+#include "vm/stackgrowth.h"
+#endif
 #include <stdio.h>
 #include <syscall-nr.h>
 
@@ -98,6 +101,7 @@ syscall_handler (struct intr_frame *f)
   /* First, read the system call number from the stack. */
   validate_user_pointer (f->esp, sizeof (uintptr_t));
   uintptr_t syscall_number = *(int *) f->esp;
+  thread_current ()->curr_esp = f->esp;
 
   /* Ensures the number corresponds to a system call that can be handled. */
   if (syscall_number >= LOOKUP_SIZE)
@@ -451,6 +455,20 @@ fd_get_file (int fd)
   return hash_entry (e, struct open_file, elem);
 }
 
+static bool
+try_alloc_new_page (const void *ptr)
+{
+  if (needs_new_page (ptr, thread_current()->curr_esp))
+  {
+    if (!grow_stack (ptr))
+      return 0;
+    else
+      return 1;
+  }
+  else
+    return 0;
+}
+
 /* Validates if a block of memory starting at START and of size SIZE bytes is
    fully contained within user virtual memory. Kills the thread (by exiting with
    failure) if the memory is invalid. Otherwise, returns (nothing) normally.
@@ -472,7 +490,10 @@ validate_user_pointer (const void *start, size_t size)
      memory by the page table. */
   for (const void *ptr = pg_round_down (start); ptr <= end; ptr += PGSIZE)
     if (pagedir_get_page (thread_current ()->pagedir, ptr) == NULL)
-      syscall_exit (EXIT_FAILURE);
+      {
+        if (!try_alloc_new_page (ptr))
+          syscall_exit (EXIT_FAILURE);
+      }
 }
 
 /* Validates if a string is fully contained within user virtual memory. Kills
@@ -495,10 +516,13 @@ validate_user_string (const char *str)
 
     /* If we reach addresses that are not mapped to physical memory before the
        end of the string, the thread is terminated. */
-    if (!is_user_vaddr(page) ||
-        pagedir_get_page (thread_current ()->pagedir, page) == NULL)
+    if (!is_user_vaddr(page))
       syscall_exit (EXIT_FAILURE);
 
+    if (pagedir_get_page (thread_current ()->pagedir, page) == NULL)
+      if (!try_alloc_new_page (str))
+        syscall_exit (EXIT_FAILURE);
+
     while (offset < PGSIZE)
       {
         if (*str == '\0')