int add(int a, int b) {
  return a + b;  // 待调试的函数
}

int main() {
  int x = 5;
  int y = 3;
  int result = add(x, y);
  volatile char *tohost_addr = (volatile char *)(0x80001000 - 4);
  *tohost_addr = 0xff;
  *tohost_addr = result;
  return 0;
}