spin::Mutex->UPSafeCell

os/src/task/context.rs

@@ -3,13 +3,22 @@ use crate::trap::trap_return;
 #[repr(C)]
 pub struct TaskContext {
     ra: usize,
+    sp: usize,
     s: [usize; 12],
 }
 
 impl TaskContext {
-    pub fn goto_trap_return() -> Self {
+    pub fn zero_init() -> Self {
+        Self {
+            ra: 0,
+            sp: 0,
+            s: [0; 12],
+        }
+    }
+    pub fn goto_trap_return(kstack_ptr: usize) -> Self {
         Self {
             ra: trap_return as usize,
+            sp: kstack_ptr,
             s: [0; 12],
         }
     }