stap on syscall probe errors with "unresolved target-symbol expression: identifier"

Issue

• stap on syscall probe errors with unresolved target-symbol expression: identifier
• Using SystemTap to trace a syscall probe, the variables do not work and error when implementing

#!/usr/bin/stap

probe syscall.umask {
    printf("> %s[%d] %#o\n", execname(), tid(), $mask);
    printf("%s\n", task_ancestry(pid2task(tid()), 0));
    print_ubacktrace();
}

probe syscall.umask.return {
    printf("< %s[%d] %o\n", execname(), tid(), $retval);
}