public static void boot (VM_Address bootStart, int bootSize) {
public static void boot (VM_Address bootStart, VM_Extent bootSize) {
  public static void boot (VM_Address bootStart, int bootSize) {    int startChunk = Conversions.addressToMmapChunksDown(bootStart);    int endChunk = Conversions.addressToMmapChunksDown(bootStart.add(bootSize));    for (int i=startChunk; i<=endChunk; i++)      mapped[i] = MAPPED;  }