public static VM_Address mmap(VM_Address address, int size, int prot, int flags) {
public static VM_Address mmap(VM_Address address, int size, int prot, int flags, int fd, long offset) {
  public static VM_Address mmap(VM_Address address, int size, int prot, int flags) {    if (VM.VerifyAssertions)      VM._assert(isPageAligned(address) && isPageMultiple(size));    VM_BootRecord bootRecord = VM_BootRecord.the_boot_record;    int result = VM.sysCall4(bootRecord.sysMMapNonFileIP, address.toInt(), size, prot, flags);    return VM_Address.fromInt(result);  }