Kernel cannot dump now.

os/src/trap/mod.rs

@@ -68,7 +68,7 @@ pub fn trap_handler() -> ! {
         Trap::Exception(Exception::LoadFault) |
         Trap::Exception(Exception::LoadPageFault) => {
             println!(
-                "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, core dumped.",
+                "[kernel] {:?} in application, bad addr = {:#x}, bad instruction = {:#x}, kernel killed it.",
                 scause.cause(),
                 stval,
                 current_trap_cx().sepc,
@@ -77,7 +77,7 @@ pub fn trap_handler() -> ! {
             exit_current_and_run_next(-2);
         }
         Trap::Exception(Exception::IllegalInstruction) => {
-            println!("[kernel] IllegalInstruction in application, core dumped.");
+            println!("[kernel] IllegalInstruction in application, kernel killed it.");
             // illegal instruction exit code
             exit_current_and_run_next(-3);
         }