full mmap implementation

1 files changed, 8 insertions, 3 deletions

diff --git a/userprog/syscall.c b/userprog/syscall.c
index 14cbaab..9da3044 100644
--- a/userprog/syscall.c
+++ b/userprog/syscall.c
@@ -576,9 +576,10 @@ static int
 syscall_mmap (void *sp, bool *segfault)
 {
   int fd;
-  void *addr, *offset;
+  uint8_t *addr, *offset;
   struct file *file, *file2;
   off_t len;
+  struct thread *thread = thread_current ();
 
   /* get arguments */
   if (! copy_from_user (&fd, STACK_ADDR (sp,1)) ||
@@ -605,11 +606,15 @@ syscall_mmap (void *sp, bool *segfault)
   if (len <= 0)
     return -1;
 
-  /* check if the pages don't overlap any existing pages */
+  /* check if the pages don't overlap any existing pages AND mapped pages */
   offset = addr;
   while(offset < addr + len)
   {
-    if (page_table_fetch (&thread_current ()->page_table, offset))
+    /* check for pages either loaded or not */
+    if (page_table_fetch (&thread->page_table, offset))
+      return -1;
+    /* check for already loaded pages not in page table (e.g. stack) */
+    if (pagedir_get_page (thread->pagedir, offset))
       return -1;
     offset += PGSIZE;
   }