Switch ok with debug mode apps, implement sys_exit correctly later.

os/src/task/mod.rs

@@ -0,0 +1,61 @@
+mod context;
+mod switch;
+
+use crate::config::MAX_APP_NUM;
+use crate::loader::{get_num_app, init_app_cx};
+use core::cell::RefCell;
+use lazy_static::*;
+use switch::__switch;
+
+pub use context::TaskContext;
+
+struct TaskControlBlock {
+    task_cx_ptr: usize,
+}
+
+pub struct TaskManager {
+    num_app: usize,
+    tasks: [TaskControlBlock; MAX_APP_NUM],
+    current_task: RefCell<usize>,
+}
+
+unsafe impl Sync for TaskManager {}
+
+lazy_static! {
+    pub static ref TASK_MANAGER: TaskManager = {
+        let num_app = get_num_app();
+        let mut tasks = [TaskControlBlock { task_cx_ptr: 0 }; MAX_APP_NUM];
+        for i in 0..num_app {
+            tasks[i] = TaskControlBlock { task_cx_ptr: init_app_cx(i) as *const _ as usize, };
+        }
+        TaskManager {
+            num_app,
+            tasks,
+            current_task: RefCell::new(0),
+        }
+    };
+}
+
+impl TaskManager {
+    pub fn run_first_task(&self) {
+        unsafe {
+            __switch(&0usize, &self.tasks[0].task_cx_ptr);
+        }
+    }
+    pub fn switch_to_next_task(&self) {
+        let current = *self.current_task.borrow();
+        let next = if current == self.num_app - 1 { 0 } else { current + 1 };
+        *self.current_task.borrow_mut() = next;
+        unsafe {
+            __switch(&self.tasks[current].task_cx_ptr, &self.tasks[next].task_cx_ptr);
+        }
+    }
+}
+
+pub fn run_first_task() {
+    TASK_MANAGER.run_first_task();
+}
+
+pub fn switch_to_next_task() {
+    TASK_MANAGER.switch_to_next_task();
+}