load elf file

user-apps/calculator/src/main.rs

@@ -1,3 +1,14 @@
-fn main() {
-    println!("Hello, world!");
+#![no_std]
+#![no_main]
+
+use core::panic::PanicInfo;
+
+#[panic_handler]
+fn panic(_info: &PanicInfo) -> ! {
+    loop {} // or call your ABI trap, or `abort()`
+}
+
+#[unsafe(no_mangle)]
+fn main() {
+    loop {}
 }