Add user_stack_size to Machine and use it for threads sp

src/kernel/thread_manager.rs

@@ -118,7 +118,8 @@ pub struct ThreadManager {
     /// List of objects created by the thread manager (such as Locks and Semaphores)
     obj_addrs: ObjAddr,
     /// If true, enables debug mode
-    debug: bool
+    debug: bool,
+    sp_max: u64,
 }
 
 impl ThreadManager {
@@ -130,7 +131,8 @@ impl ThreadManager {
             g_alive: List::default(),
             ready_list: List::default(),
             obj_addrs: ObjAddr::init(),
-            debug
+            debug,
+            sp_max: 0
         }
     }
 
@@ -423,6 +425,14 @@ impl ThreadManager {
         }
     }
 
+    pub fn get_sp_max(&self) -> u64 {
+        self.sp_max
+    }
+
+    pub fn set_sp_max(&mut self, sp_max: u64) {
+        self.sp_max = sp_max;
+    }
+
 }
 
 #[cfg(test)]