Fix rox checking and make filesys_lock global

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"
@@ -81,8 +82,8 @@ process_execute (const char *cmd)
      of the process. */
   char *file_name = strtok_r (cmd_copy, " ", &data->cmd_saveptr);
 
-/* Validates that the current file to be executed is a valid file */
-if (filesys_open (file_name) == NULL)
+  /* Validates that the current file to be executed is a valid file */
+  if (filesys_open (file_name) == NULL)
     return TID_ERROR;
 
   /* Create a new thread to execute the command, by initializing

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)
@@ -114,10 +106,10 @@ 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++)
-    args[i] = *(uintptr_t *)(f->esp + sizeof (uintptr_t) * (i + 1));
+                         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
      there is a return value it is stored in f->eax. */
@@ -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)
     {
@@ -408,75 +398,17 @@ 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.
-   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)
+   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)
 {
-  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++;
-    }
+  return (void *) 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;
-}

src/userprog/syscall.h

@@ -2,11 +2,14 @@
 #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);