int flags, int fd, Offset offset) { return null;
int flags, int fd, Offset offset) { return VM_SysCallMagic.sysMMap(VM_BootRecord.the_boot_record.sysMMapIP, start, length, protection, flags, fd, offset);
  public static Address sysMMap(Address start, Extent length, int protection,                                   int flags, int fd, Offset offset) {     return null;   }