Move user process stack initialization into a helper function

src/userprog/process.c

@@ -68,6 +68,9 @@ push_to_stack (void **esp, void *data, size_t data_size)
   return *esp;
 }
 
+static void process_init_stack (void *file_name_, char *saveptr, void **esp,
+                                char *file_name);
+
 /* A thread function that loads a user process and starts it
    running. */
 static void
@@ -79,10 +82,9 @@ start_process (void *file_name_)
    /* Retrieve first argument of command, which is the file name
      of the process. */
   char *saveptr;
-  char *arg = strtok_r (file_name_, " ", &saveptr);
+  char *file_name = strtok_r (file_name_, " ", &saveptr);
-  
+  if (strlen (file_name) > FNAME_MAX_LEN)
-  char file_name[FNAME_MAX_LEN + 1];
+    file_name[FNAME_MAX_LEN + 1] = '\n';
-  strlcpy (file_name, arg, FNAME_MAX_LEN + 1);
 
   /* TODO: Move naming of thread to process_execute, so start
     tokenizing there. */
@@ -95,6 +97,32 @@ start_process (void *file_name_)
   if_.eflags = FLAG_IF | FLAG_MBS;
   success = load (file_name, &if_.eip, &if_.esp);
 
+  /* If load failed, quit. */
+  if (!success) 
+    {
+      palloc_free_page (file_name_);
+      thread_exit ();
+    }
+
+  process_init_stack (file_name_, saveptr, &if_.esp, file_name);
+  palloc_free_page (file_name_);
+
+  /* Start the user process by simulating a return from an
+     interrupt, implemented by intr_exit (in
+     threads/intr-stubs.S).  Because intr_exit takes all of its
+     arguments on the stack in the form of a `struct intr_frame',
+     we just point the stack pointer (%esp) to our stack frame
+     and jump to it. */
+  asm volatile ("movl %0, %%esp; jmp intr_exit" : : "g" (&if_) : "memory");
+  NOT_REACHED ();
+}
+
+/* Helper function that initializes the stack of a newly created 
+   user process. */
+static void
+process_init_stack (void *file_name_, char *saveptr, void **esp,
+                    char *file_name)
+  {
     /* Load command line argument *data* to user process stack.
        This can't cause overflow due to enforcing that the size of
        command line input must fit in a page. Also keep track
@@ -102,22 +130,23 @@ start_process (void *file_name_)
     struct list arg_list;
     list_init (&arg_list);
 
+    char *arg = file_name;
     int arg_count = 0;
     while (arg != NULL)
       {
-      push_to_stack (&if_.esp, arg, (strlen (arg) + 1) * sizeof (char));
+        push_to_stack (esp, arg, (strlen (arg) + 1) * sizeof (char));
         
         struct arg_elem *arg_elem = malloc (sizeof (struct arg_elem));
         if (arg_elem == NULL)
           {
             printf("ERROR: Couldn't allocate argument pointer memory for %s!\n",
-                 file_name);
+                   thread_current ()->name);
             palloc_free_page (file_name_);
-          if (success) process_exit ();
+            process_exit ();
             thread_exit ();
           }
 
-      arg_elem->arg = if_.esp;
+        arg_elem->arg = *esp;
         list_push_front (&arg_list, &arg_elem->elem);
 
         arg_count++;
@@ -126,7 +155,7 @@ start_process (void *file_name_)
 
     /* Calculate the remaining number of bytes that need to be written
        to the user process stack in order to check for possible overflow. */
-  size_t align_size = ((unsigned int) if_.esp % 4) * sizeof (uint8_t);
+    size_t align_size = ((unsigned int) *esp % 4) * sizeof (uint8_t);
     size_t argv_data_size = (arg_count + 1) * sizeof (char *);
     size_t argv_size = sizeof (char **);
     size_t argc_size = sizeof (int);
@@ -136,18 +165,18 @@ start_process (void *file_name_)
 
     /* If pushing the rest of the data required for the stack would cause
        overflow, allocate an extra page. */ 
-  if (PHYS_BASE - if_.esp + remaining_size > PGSIZE)
+    if (PHYS_BASE - *esp + remaining_size > PGSIZE)
       {
         /* TODO: Allocate an extra page for the rest of the process stack. */
       }
 
     /* Align stack pointer to word size before pushing argv elements for
        performance. */
-  if_.esp -= align_size;
+    *esp -= align_size;
     
     /* Push a null pointer sentinel inside argv. */
-  if_.esp -= sizeof (char *);
+    *esp -= sizeof (char *);
-  *(char *) if_.esp = 0;
+    *(char *) *esp = 0;
     
     /* Push pointer to the process file name to the stack. */
     char **argv;
@@ -159,35 +188,21 @@ start_process (void *file_name_)
       {
         struct arg_elem *arg_elem = list_entry (e, struct arg_elem, elem);
         
-      argv = push_to_stack (&if_.esp, &arg_elem->arg, sizeof (arg_elem->arg));
+        argv = push_to_stack (esp, &arg_elem->arg, sizeof (arg_elem->arg));
         
         e = list_next (e);
         free (arg_elem);
       }
 
     /* Push pointer to the start of argv array. */
-  push_to_stack (&if_.esp, &argv, sizeof(argv));
+    push_to_stack (esp, &argv, sizeof(argv));
 
     /* Push the number of arguments to the stack. */
-  push_to_stack (&if_.esp, &arg_count, sizeof (arg_count));
+    push_to_stack (esp, &arg_count, sizeof (arg_count));
 
     /* Push fake return address (null pointer). */
-  if_.esp -= sizeof (char *);
+    *esp -= sizeof (char *);
-  *(char *) if_.esp = 0;
+    *(char *) *esp = 0;
-
-  /* If load failed, quit. */
-  palloc_free_page (file_name_);
-  if (!success) 
-    thread_exit ();
-
-  /* Start the user process by simulating a return from an
-     interrupt, implemented by intr_exit (in
-     threads/intr-stubs.S).  Because intr_exit takes all of its
-     arguments on the stack in the form of a `struct intr_frame',
-     we just point the stack pointer (%esp) to our stack frame
-     and jump to it. */
-  asm volatile ("movl %0, %%esp; jmp intr_exit" : : "g" (&if_) : "memory");
-  NOT_REACHED ();
  }
 
 /* Waits for thread TID to die and returns its exit status.