1 files changed, 15 insertions, 1 deletions
diff --git a/sysproc.c b/sysproc.c
index 11770ff..efaa372 100644
--- a/sysproc.c
+++ b/sysproc.c
@@ -57,7 +57,8 @@ sys_sbrk(void)
 int
 sys_sleep(void)
 {
-  int n, ticks0;
+  int n;
+  uint ticks0;
   
   if(argint(0, &n) < 0)
     return -1;
@@ -73,3 +74,16 @@ sys_sleep(void)
   release(&tickslock);
   return 0;
 }
+
+// return how many clock tick interrupts have occurred
+// since boot.
+int
+sys_uptime(void)
+{
+  uint xticks;
+  
+  acquire(&tickslock);
+  xticks = ticks;
+  release(&tickslock);
+  return xticks;
+}