Try batch but kernel panicked.

os/src/trap/mod.rs

@@ -0,0 +1,38 @@
+mod context;
+
+use riscv::register::{
+    mtvec::TrapMode,
+    stvec,
+    scause::{
+        self,
+        Trap,
+        Exception,
+    },
+    stval,
+};
+
+global_asm!(include_str!("trap.S"));
+
+pub fn init() {
+    extern "C" { fn __alltraps(); }
+    unsafe {
+        stvec::write(__alltraps as usize, TrapMode::Direct);
+    }
+}
+
+#[no_mangle]
+pub fn trap_handler(cx: &mut TrapContext) -> &mut TrapContext {
+    let scause = scause::read();
+    let stval = stval::read();
+    match scause.cause() {
+        Trap::Exception(Exception::UserEnvCall) => {
+            panic!("Triggered UserEnvCall!");
+        }
+        _ => {
+            panic!("Unsupported trap!");
+        }
+    }
+    cx
+}
+
+pub use context::TrapContext;