PFN_NUMBER
MxGetNextPage(
      VOID 
  );

Routine Description:

    This function returns the next physical page number from either the
    largest low memory descritor or the largest free descriptor. If there
    are no physical pages left, then a bugcheck is executed since the
    system cannot be initialized.

Arguments:

    LoaderBlock - Supplies the address of the loader block.

Return Value:

    None.

Environment:

    Kernel mode.