1 files changed, 6 insertions, 3 deletions

diff --git a/userprog/syscall.c b/userprog/syscall.c
index f8e0197..541668d 100644
--- a/userprog/syscall.c
+++ b/userprog/syscall.c
@@ -17,6 +17,9 @@
 
 #define STACK_SLOT_SIZE sizeof(int)
 
+/* stored stack pointer for the "page fault inside syscall/kernel"-case */
+void *syscall_sp;
+
 /* Prototypes for Utilities */
 static int get_user (const uint8_t *uaddr);
 static bool put_user (uint8_t *udst, uint8_t byte);
@@ -195,10 +198,10 @@ syscall_handler (struct intr_frame *f)
   handler* fp;
   bool segfault = false;
   int result;
-  void *sp = f->esp;
+  syscall_sp = f->esp;
 
   /* The system call number and the arguments are on the stack */
-  if (! copy_from_user (&syscall_nr,sp))
+  if (! copy_from_user (&syscall_nr,syscall_sp))
     goto fail;
   switch (syscall_nr) {
   case SYS_HALT: fp = syscall_halt; break;
@@ -217,7 +220,7 @@ syscall_handler (struct intr_frame *f)
   default:
     goto fail;
   }
-  result = fp (sp, &segfault);
+  result = fp (syscall_sp, &segfault);
   if (segfault)
     goto fail;
   f->eax = result;