Merge branch 'user-programs-stdout' into 'user-programs'

# Conflicts:
#   src/userprog/process.c

src/userprog/process.c

@@ -16,9 +16,18 @@
 #include "threads/interrupt.h"
 #include "threads/synch.h"
 #include "threads/palloc.h"
+#include "threads/malloc.h"
 #include "threads/thread.h"
 #include "threads/vaddr.h"
-#include "devices/timer.h"
+#include "threads/synch.h"
+
+/* Keeps track of the position of pointers to user program arguments
+   within a linked list. */
+struct arg_elem
+  {
+    char* arg;
+    struct list_elem elem;
+  };
 
 static thread_func start_process NO_RETURN;
 static bool load (const char *cmdline, void (**eip) (void), void **esp);
@@ -38,6 +47,9 @@ process_execute (const char *file_name)
   fn_copy = palloc_get_page (0);
   if (fn_copy == NULL)
     return TID_ERROR;
+
+  /* Imposing implicit limit that the command line arguments
+    including the user program name fit within a single page. */
   strlcpy (fn_copy, file_name, PGSIZE);
 
   /* Create a new thread to execute FILE_NAME. */
@@ -47,15 +59,30 @@ process_execute (const char *file_name)
   return tid;
 }
 
+static void *
+push_to_stack (void **esp, void *data, size_t data_size)
+{
+  *esp -= data_size;
+  memcpy (*esp, data, data_size);
+  return *esp;
+}
+
 /* A thread function that loads a user process and starts it
    running. */
 static void
 start_process (void *file_name_)
 {
-  char *file_name = file_name_;
   struct intr_frame if_;
   bool success;
 
+  /* 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[15];
+  strlcpy (file_name, arg, 15);
+
   /* Initialize interrupt frame and load executable. */
   memset (&if_, 0, sizeof if_);
   if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
@@ -63,8 +90,93 @@ start_process (void *file_name_)
   if_.eflags = FLAG_IF | FLAG_MBS;
   success = load (file_name, &if_.eip, &if_.esp);
 
+  /* 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
+     of pointers to the argument data within a linked list. */
+  char *file_name_ptr = push_to_stack (&if_.esp, file_name,
+                                       (strlen (file_name) + 1)
+                                        * sizeof (char));
+
+  struct list arg_list;
+  list_init (&arg_list);
+
+  int arg_count = 1;
+  while (arg != NULL)
+    {
+      push_to_stack (&if_.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);
+          palloc_free_page (file_name_);
+          if (success) process_exit ();
+          thread_exit ();
+        }
+
+      arg_elem->arg = arg;
+      list_push_front (&arg_list, &arg_elem->elem);
+
+      arg_count++;
+      arg = strtok_r (NULL, " ", &saveptr);
+    }
+
+  /* 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 argv_data_size = (arg_count + 1) * sizeof (char *);
+  size_t argv_size = sizeof (char **);
+  size_t argc_size = sizeof (int);
+  size_t return_addr_size = sizeof (void *);
+  size_t remaining_size = align_size + argv_data_size + argv_size + argc_size 
+                          + return_addr_size;
+
+  /* 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)
+    {
+      /* 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;
+  
+  /* Push a null pointer sentinel inside argv. */
+  if_.esp -= sizeof (char *);
+  *(char *) if_.esp = NULL;
+
+  /* Push pointers to process arguments from argument linked list */
+  struct list_elem *e = list_begin (&arg_list);
+  struct list_elem *tail = list_tail (&arg_list);
+  while (e != tail)
+    {
+      struct arg_elem *arg_elem = list_entry (e, struct arg_elem, elem);
+      
+      push_to_stack (&if_.esp, &arg_elem->arg, sizeof (arg_elem->arg));
+      
+      e = list_next (e);
+      free (arg_elem);
+    }
+
+  /* Push pointer to the process file name to the stack. */
+  char **argv = push_to_stack (&if_.esp, &file_name_ptr,
+                               sizeof (file_name_ptr));
+
+  /* Push pointer to the start of argv array. */
+  push_to_stack (&if_.esp, &argv, sizeof(argv));
+
+  /* Push the number of arguments to the stack. */
+  push_to_stack (&if_.esp, &arg_count, sizeof (arg_count));
+
+  /* Push fake return address (null pointer). */
+  if_.esp -= sizeof (char *);
+  *(char *) if_.esp = NULL;
+
   /* If load failed, quit. */
-  palloc_free_page (file_name);
+  palloc_free_page (file_name_);
   if (!success) 
     thread_exit ();