fix fork bug

os/src/interrupt.rs

@@ -66,6 +66,7 @@ fn super_timer() {
     clock_set_next_event();
     tick();
 }
+
 fn page_fault(tf: &mut TrapFrame) {
     println!(
         "{:?} va = {:#x} instruction = {:#x}",

os/src/process/mod.rs

@@ -71,6 +71,6 @@ pub fn add_thread(thread: Box<Thread>) -> usize {
     CPU.add_thread(thread)
 }
 
-pub fn current_thread() -> Box<Thread> {
+pub fn current_thread() -> &'static Box<Thread> {
     CPU.current_thread()
 }

os/src/process/processor.rs

@@ -133,7 +133,7 @@ impl Processor {
         self.inner().current.as_mut().unwrap().0 as usize
     }
 
-    pub fn current_thread(&self) -> Box<Thread> {
-        self.inner().current.as_ref().unwrap().1.clone()
+    pub fn current_thread(&self) -> &Box<Thread> {
+        &self.inner().current.as_mut().unwrap().1
     }
 }

os/src/process/structs.rs

@@ -119,7 +119,6 @@ impl Thread {
     }
 }
 
-#[derive(Clone)]
 pub struct KernelStack(usize);
 
 impl KernelStack {

usr/rust/src/bin/fork.rs

@@ -10,6 +10,7 @@ use user::syscall::sys_fork;
 
 #[no_mangle]
 pub fn main() -> usize {
+    let tid = sys_fork();
     let tid = sys_fork();
     if tid == 0 {
         println!("I am child");