// UnveilBlock blocks future unveil calls.
// For more information see unveil(2).
func UnveilBlock() error {
	if err := supportsUnveil(); err != nil {
		return err
	}
	return unveil(nil, nil)
}

// supportsUnveil checks for availability of the unveil(2) system call based
// on the running OpenBSD version.
func supportsUnveil() error {
	maj, min, err := majmin()
	if err != nil {
		return err
	}