Fix Bug: Free all entries in the fd hashtable when the process exits, (Saleh, Ethan)

src/threads/synch.c

@@ -212,6 +212,7 @@ donate_priority (struct thread *donee) {
   ASSERT (intr_get_level () == INTR_OFF);
 
   struct thread *donor = thread_current ();
+  list_remove (&donor->donor_elem);
   list_push_back (&donee->donors_list, &donor->donor_elem);
   
   while (donee != NULL)
@@ -260,6 +261,7 @@ lock_acquire (struct lock *lock)
   ASSERT (!lock_held_by_current_thread (lock));
 
   struct thread *t = thread_current ();
+  ASSERT (t->waiting_lock == NULL);
 
   enum intr_level old_level = intr_disable ();
   if (lock->holder != NULL)
@@ -341,7 +343,6 @@ lock_release (struct lock *lock)
      released, transfer the remaining orphaned donors to its donor list. */
   if (max_donor != NULL)
     {
-      list_remove (&max_donor->donor_elem);
       while (!list_empty (&orphan_list))
         list_push_back (&max_donor->donors_list, list_pop_front (&orphan_list));
     }

src/threads/thread.c

@@ -373,7 +373,9 @@ thread_exit (void)
      and schedule another process.  That process will destroy us
      when it calls thread_schedule_tail(). */
   intr_disable ();
-  list_remove (&thread_current()->allelem);
+  struct thread *t = thread_current ();
+  list_remove (&t->allelem);
+  list_remove (&t->donor_elem);
   thread_current ()->status = THREAD_DYING;
   schedule ();
   NOT_REACHED ();
@@ -679,6 +681,7 @@ init_thread (struct thread *t, const char *name, int nice, int priority,
   t->base_priority
       = thread_mlfqs ? calculate_bsd_priority (recent_cpu, nice) : priority;
   list_init (&t->donors_list);
+  list_push_back (&t->donors_list, &t->donor_elem);
   t->waiting_lock = NULL;
 
   t->nice = nice;

src/userprog/exception.c

@@ -145,14 +145,6 @@ 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 (!user)
-    {
-      f->eip = (void *)f->eax;
-      f->eax = 0xffffffff;
-      return;
-    }
-
   /* To implement virtual memory, delete the rest of the function
      body, and replace it with code that brings in the page to
      which fault_addr refers. */

src/userprog/process.c

@@ -8,6 +8,7 @@
 #include <string.h>
 #include "userprog/gdt.h"
 #include "userprog/pagedir.h"
+#include "userprog/syscall.h"
 #include "userprog/tss.h"
 #include "filesys/directory.h"
 #include "filesys/file.h"
@@ -46,6 +47,9 @@ struct process_start_data
                           tokens while maintaining state. */
     char file_name[FNAME_MAX_LEN + 1]; /* Name of the file of the process to
                                       be started. */
+    struct semaphore load_sema;
+
+    bool success;
   };
 
 static thread_func start_process NO_RETURN;
@@ -61,11 +65,7 @@ process_execute (const char *cmd)
   char *cmd_copy;
   tid_t tid;
   
-  struct process_start_data *data = malloc (sizeof (struct process_start_data));
-  if (data == NULL)
-    {
-      return TID_ERROR;
-    }
+  struct process_start_data data;
 
   /* Make a copy of command.
      Otherwise there's a race between the caller and load(). */
@@ -79,21 +79,39 @@ process_execute (const char *cmd)
 
   /* Retrieve first argument of command, which is the file name
      of the process. */
-  char *file_name = strtok_r (cmd_copy, " ", &data->cmd_saveptr);
+  char *file_name = strtok_r (cmd_copy, " ", &data.cmd_saveptr);
 
+  /* NOTE: Currently, the file being executed is closed in load () and then
+          reopened here. Because load is an exported public function, this
+          might be necessary. */
+  lock_acquire (&filesys_lock);
   /* Validates that the current file to be executed is a valid file */
-if (filesys_open (file_name) == NULL)
+  bool valid_file = filesys_open (file_name) != NULL;
+  lock_release (&filesys_lock);
+  if (!valid_file)
     return TID_ERROR;
 
   /* Create a new thread to execute the command, by initializing
      it running the function 'start_process' with the appropriate
      arguments. For details of arguments, see 'start_process'. */
-  data->cmd = cmd_copy;
-  strlcpy (data->file_name, file_name, FNAME_MAX_LEN + 1);
+  data.cmd = cmd_copy;
+  strlcpy (data.file_name, file_name, FNAME_MAX_LEN + 1);
+  sema_init (&data.load_sema, 0);
+  data.success = false;
+
+  tid = thread_create (file_name, PRI_DEFAULT, start_process, &data);
 
-  tid = thread_create (file_name, PRI_DEFAULT, start_process, data);
   if (tid == TID_ERROR)
+    {
       palloc_free_page (cmd_copy);
+    }
+  else
+    {
+      sema_down (&data.load_sema);
+      if (!data.success)
+        tid = TID_ERROR;
+    }
+
   return tid;
 }
 
@@ -111,7 +129,6 @@ static void
 start_process (void *proc_start_data)
 {
   struct intr_frame if_;
-  bool success;
 
   struct process_start_data *data = proc_start_data;
 
@@ -120,34 +137,38 @@ start_process (void *proc_start_data)
   if_.gs = if_.fs = if_.es = if_.ds = if_.ss = SEL_UDSEG;
   if_.cs = SEL_UCSEG;
   if_.eflags = FLAG_IF | FLAG_MBS;
-  success = load (data->file_name, &if_.eip, &if_.esp);
   
-  /* If load failed, quit. */
-  if (!success) 
+  lock_acquire (&filesys_lock);
+  
+  /* Prevent writing to the file being executed. */
+  struct file *exec_file = filesys_open (data->file_name);
+  thread_current ()->exec_file = exec_file;
+  file_deny_write (exec_file);
+  lock_release (&filesys_lock);
+
+  data->success = load (data->file_name, &if_.eip, &if_.esp);
+
+  /* If load failed, free process startup data and quit. */
+  if (!data->success)
     {
       palloc_free_page (data->cmd);
-      goto fail;
+      sema_up (&data->load_sema);
+      thread_exit ();
     }
 
   /* Initialize user process stack and free page used to store the
      command that executed the process. */
-  success = process_init_stack (data->cmd_saveptr, &if_.esp, data->file_name);
+  bool success = process_init_stack (data->cmd_saveptr, &if_.esp, data->file_name);
   palloc_free_page (data->cmd);
+  data->success = success;
+  sema_up (&data->load_sema);
   
-  /* If stack initialization failed, free resources and quit. */
+  /* If stack initialization failed, free process resources and quit. */
   if (!success)
     {
-      process_exit ();
-      goto fail;
+      thread_exit ();
     }
 
-  /* NOTE: Currently, the file being executed is closed in load () and then 
-           reopened here. Because load is an exported public function, this
-           might be necessary. */
-  struct file *exec_file = filesys_open (data->file_name);
-  thread_current ()->exec_file = exec_file;
-  file_deny_write (exec_file);
-
   /* 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
@@ -156,11 +177,6 @@ start_process (void *proc_start_data)
      and jump to it. */
   asm volatile ("movl %0, %%esp; jmp intr_exit" : : "g" (&if_) : "memory");
   NOT_REACHED ();
-
-/* If starting the process failed, free its common resources and exit. */
- fail:
-  free (data);
-  thread_exit ();
 }
 
 /* Helper function that initializes the stack of a newly created 
@@ -291,7 +307,9 @@ process_wait (tid_t child_tid UNUSED)
         break;
     }
   if (child_result == NULL)
+    {
       return -1;
+    }
   /* Wait for child to die. */
   sema_down (&child_result->sema);
   /* We need lock release in process_exit, so we need to acquire (and possibly
@@ -305,6 +323,7 @@ process_wait (tid_t child_tid UNUSED)
   int exit_status = child_result->exit_status;
   lock_release (&child_result->lock);
   free (child_result);
+
   return exit_status;
 }
 
@@ -312,11 +331,23 @@ process_wait (tid_t child_tid UNUSED)
 void
 process_exit (void)
 {
+
+
   struct thread *cur = thread_current ();
   uint32_t *pd;
 
   printf ("%s: exit(%d)\n", cur->name, cur->exit_status);
+
+  /* Clean up all open files */
+  hash_destroy (&cur->open_files, fd_cleanup);
+
+  /* Close the executable file. */
+  if (cur->exec_file != NULL)
+    {
+      lock_acquire (&filesys_lock);
       file_close (cur->exec_file);
+      lock_release (&filesys_lock);
+    }
 
   /* Update process result. */
   if (cur->result != NULL)
@@ -341,10 +372,11 @@ process_exit (void)
   /* Free child process results or signal parent's death. */
   struct list_elem *e;
   for (e = list_begin (&cur->child_results);
-       e != list_end (&cur->child_results); e = list_next (e))
+       e != list_end (&cur->child_results);)
     {
       struct process_result *result
           = list_entry (e, struct process_result, elem);
+      struct list_elem *next = list_next (e);
       lock_acquire (&result->lock);
       /* Child has died (and was not waited for). Free the result. */
       if (sema_try_down (&result->sema))
@@ -358,6 +390,7 @@ process_exit (void)
           sema_up (&result->sema);
           lock_release (&result->lock);
         }
+      e = next;
     }
 
   /* Destroy the current process's page directory and switch back
@@ -476,6 +509,7 @@ load (const char *file_name, void (**eip) (void), void **esp)
   off_t file_ofs;
   bool success = false;
   int i;
+  lock_acquire (&filesys_lock);
 
   /* Allocate and activate page directory. */
   t->pagedir = pagedir_create ();
@@ -575,6 +609,7 @@ load (const char *file_name, void (**eip) (void), void **esp)
  done:
   /* We arrive here whether the load is successful or not. */
   file_close (file);
+  lock_release (&filesys_lock);
   return success;
 }
 

src/userprog/syscall.c

@@ -11,12 +11,8 @@
 #include "userprog/process.h"
 #include "userprog/pagedir.h"
 #include <stdio.h>
-#include <stdbool.h>
 #include <syscall-nr.h>
 
-#define MAX_SYSCALL_ARGS 3
-
-static struct lock filesys_lock;
 static unsigned fd_counter = MIN_USER_FD;
 
 struct open_file
@@ -49,11 +45,7 @@ static unsigned syscall_tell (int fd);
 static void syscall_close (int fd);
 
 static struct open_file *fd_get_file (int fd);
-static void validate_user_pointer (const void *ptr, size_t size,
-                                   bool check_write);
-static void validate_user_string (const char *str, bool check_write);
-static int get_user (const uint8_t *);
-static bool put_user (uint8_t *, uint8_t);
+static void *validate_user_pointer (const void *ptr, size_t size);
 
 /* A struct defining a syscall_function pointer along with its arity. */
 typedef struct
@@ -103,8 +95,8 @@ static void
 syscall_handler (struct intr_frame *f)
 {
   /* First, read the system call number from the stack. */
-  validate_user_pointer (f->esp, sizeof (uintptr_t), false);
-  uintptr_t syscall_number = *(int *)f->esp;
+  validate_user_pointer (f->esp, 1);
+  unsigned syscall_number = *(int *) f->esp;
 
   /* Ensures the number corresponds to a system call that can be handled. */
   if (syscall_number >= LOOKUP_SIZE)
@@ -114,9 +106,9 @@ syscall_handler (struct intr_frame *f)
 
   /* Next, read and copy the arguments from the stack pointer. */
   validate_user_pointer (f->esp + sizeof (uintptr_t),
-                         syscall.arity * sizeof (uintptr_t), false);
-  uintptr_t args[MAX_SYSCALL_ARGS] = { 0 };
-  for (int i = 0; i < syscall.arity && i < MAX_SYSCALL_ARGS; i++)
+                         syscall.arity * sizeof (uintptr_t));
+  uintptr_t args[3] = {0};
+  for (int i=0; i < syscall.arity; i++)
       args[i] = *(uintptr_t *) (f->esp + sizeof (uintptr_t) * (i + 1));
 
   /* Call the function that handles this system call with the arguments. When
@@ -148,11 +140,9 @@ syscall_exit (int status)
 static pid_t
 syscall_exec (const char *cmd_line)
 {
-  validate_user_string (cmd_line, false);
+  validate_user_pointer (cmd_line, 1);
 
-  lock_acquire (&filesys_lock);
   pid_t pid = process_execute(cmd_line);
-  lock_release (&filesys_lock);
 
   return pid;
 }
@@ -171,7 +161,7 @@ syscall_wait (pid_t pid)
 static bool
 syscall_create (const char *file UNUSED, unsigned initial_size UNUSED)
 {
-  validate_user_string (file, false);
+  validate_user_pointer (file, 1);
 
   lock_acquire (&filesys_lock);
   bool status = filesys_create (file, initial_size);
@@ -186,7 +176,7 @@ syscall_create (const char *file UNUSED, unsigned initial_size UNUSED)
 static bool
 syscall_remove (const char *file)
 {
-  validate_user_string (file, false);
+  validate_user_pointer (file, 1);
 
   lock_acquire (&filesys_lock);
   bool status = filesys_remove (file);
@@ -202,7 +192,7 @@ syscall_remove (const char *file)
 static int
 syscall_open (const char *file)
 {
-  validate_user_string (file, false);
+  validate_user_pointer (file, 1);
 
   lock_acquire (&filesys_lock);
   struct file *ptr = filesys_open (file);
@@ -257,7 +247,7 @@ syscall_read (int fd, void *buffer, unsigned size)
   if (fd < 0 || fd == STDOUT_FILENO)
     return -1;
 
-  validate_user_pointer (buffer, size, true);
+  validate_user_pointer (buffer, size);
 
   if (fd == STDIN_FILENO)
     {
@@ -294,7 +284,7 @@ syscall_write (int fd, const void *buffer, unsigned size)
   if (fd <= 0)
     return 0;
 
-  validate_user_pointer (buffer, size, false);
+  validate_user_pointer (buffer, size);
 
   if (fd == STDOUT_FILENO)
     {
@@ -388,6 +378,20 @@ fd_less (const struct hash_elem *a_, const struct hash_elem *b_,
   return a->fd < b->fd;
 }
 
+/* Function to clean up an open file entry. Closes the file and frees the
+   associated memory. */
+void
+fd_cleanup (struct hash_elem *e, void *aux UNUSED)
+{
+  struct open_file *file_info = hash_entry (e, struct open_file, elem);
+
+  lock_acquire (&filesys_lock);
+  file_close (file_info->file);
+  lock_release (&filesys_lock);
+
+  free (file_info);
+}
+
 /* Gets a file from its descriptor (FD number). If there is no file with the fd
    FD it returns NULL. */
 static struct open_file *
@@ -408,75 +412,17 @@ fd_get_file (int fd)
 }
 
 /* Validates if a block of memory starting at PTR and of size SIZE bytes is
-   fully contained within valid user virtual memory. thread_exit () if the
-   memory is invalid.
+   fully contained within user virtual memory. Kills the thread (by calling
+   thread_exit) if the memory is invalid. Otherwise, returns the PTR given.
    If the size is 0, the function does no checks and returns PTR.*/
-static void
-validate_user_pointer (const void *ptr, size_t size, bool check_write)
+static void *
+validate_user_pointer (const void *ptr, size_t size)
 {
-  if (size == 0)
-    return;
-  /* ptr < ptr + size - 1, so sufficient to check that (ptr + size -1) is a
-     valid user virtual memory address. */
-  void *last = ptr + size - 1;
-  if (!is_user_vaddr (last))
+  if (size > 0 && (ptr == NULL ||
+                   !is_user_vaddr (ptr) ||
+                   !is_user_vaddr (ptr + size - 1) ||
+                   pagedir_get_page (thread_current()->pagedir, ptr) == NULL))
     thread_exit ();
-  ptr = pg_round_down (ptr);
-  while (ptr <= last)
-    {
-      int result;
-      /* Check read access to pointer. */
-      if ((result = get_user (ptr)) == -1)
-        thread_exit ();
-      /* Check write access to pointer (if required). */
-      if (check_write && !put_user (ptr, result))
-        thread_exit ();
-      ptr += PGSIZE;
-    }
-}
 
-/* Validates of a C-string starting at ptr is fully contained within valid
-   user virtual memory. thread_exit () if the memory is invalid. */
-static void
-validate_user_string (const char *ptr, bool check_write)
-{
-  while (true)
-    {
-      if (!is_user_vaddr (ptr))
-        thread_exit ();
-      int result;
-      if ((result = get_user ((const uint8_t *)ptr)) == -1)
-        thread_exit ();
-      if (check_write && !put_user ((uint8_t *)ptr, result))
-        thread_exit ();
-      if (*ptr == '\0')
-        return;
-      ptr++;
-    }
-}
-
-/* PROVIDED BY SPEC.
-   Reads a byte at user virtual address UADDR.
-   UADDR must be below PHYS_BASE.
-   Returns the byte value if successful, -1 if a segfault occurred. */
-static int
-get_user (const uint8_t *uaddr)
-{
-  int result;
-  asm ("movl $1f, %0; movzbl %1, %0; 1:" : "=&a"(result) : "m"(*uaddr));
-  return result;
-}
-
-/* PROVIDED BY SPEC.
-   Writes BYTE to user address UDST.
-   UDST must be below PHYS_BASE.
-   Returns true if successful, false if a segfault occurred. */
-static bool
-put_user (uint8_t *udst, uint8_t byte)
-{
-  int error_code;
-  asm ("movl $1f, %0; movb %b2, %1; 1:"
-       : "=&a"(error_code), "=m"(*udst)
-       : "q"(byte));
-  return error_code != -1;
+  return (void *) ptr;
 }

src/userprog/syscall.h

@@ -2,14 +2,18 @@
 #define USERPROG_SYSCALL_H
 
 #include <hash.h>
+#include "threads/synch.h"
 
 #define MIN_USER_FD 2
 
 typedef int pid_t;
 
+struct lock filesys_lock;
+
 void syscall_init (void);
 
 unsigned fd_hash (const struct hash_elem *element, void *aux);
 bool fd_less (const struct hash_elem *a, const struct hash_elem *b, void *aux);
+void fd_cleanup (struct hash_elem *e, void *aux);
 
 #endif /* userprog/syscall.h */