use local stack pointer inside syscall_handler

1 files changed, 5 insertions, 4 deletions

diff --git a/userprog/syscall.c b/userprog/syscall.c
index 71aba5c..7f8c397 100644
--- a/userprog/syscall.c
+++ b/userprog/syscall.c
@@ -201,10 +201,10 @@ syscall_handler (struct intr_frame *f)
   handler* fp;
   bool segfault = false;
   int result;
-  syscall_sp = f->esp;
+  void *sp = f->esp;
 
   /* The system call number and the arguments are on the stack */
-  if (! copy_from_user (&syscall_nr,syscall_sp))
+  if (! copy_from_user (&syscall_nr,sp))
     goto fail;
   switch (syscall_nr) {
   case SYS_HALT: fp = syscall_halt; break;
@@ -225,8 +225,9 @@ syscall_handler (struct intr_frame *f)
   default:
     goto fail;
   }
-  result = fp (syscall_sp, &segfault);
-  if (segfault)
+  syscall_sp = sp;
+        result = fp (sp, &segfault);
+        if (segfault)
     goto fail;
   f->eax = result;
   return;