@Override
	protected MemoryPage getPage(long addr) {
		IteratorSTL<Pair<Long, MemoryPage>> iter;
		iter = page.find(addr);
		if (iter.equals(page.end())) {
			MemoryPage pageptr;
			if (underlie == null) {
				int size = getPageSize();
				pageptr = new MemoryPage(size);
				for(int i=0;i<size;++i) {
					pageptr.data[i] = 0;
				}
				pageptr.setUninitialized();
				return pageptr;
			}
			// defer to underlie memory bank
			pageptr = underlie.getPage(addr);
			page.add(addr, pageptr);
			return pageptr;
		}
		return (iter.get()).second;
	}
A page overlay memory bank needs all the parameters for a generic memory bank
and it needs to know the underlying memory bank being overlayed.
@param spc is the address space associated with the memory bank
@param ul is the underlying MemoryBank
@param faultHandler
Ghidra/Framework/Emulation/src/main/java/ghidra/pcode/memstate/MemoryPageOverlay.java