int main()
{
  struct utsname utsn;
  address_t old_syscall;
  int ret;
  ret = my_uname(&utsn);
  printf("%s\n", utsn.sysname);
  init_kmem();
  ret = read_syscall(122, &old_syscall);
  printf("%p\n", old_syscall);
  ret = write_syscall(59, old_syscall);
  memset(&utsn, 0, sizeof(struct utsname));
  ret = my_syscall(&utsn);
  printf("%s\n", utsn.sysname);
}