shadow_page_for
shadow = shadow_page_for(page);
s_pages[i] = shadow_page_for(pages[i]);
return page_address(shadow_page_for(page));
shadow_page_for(page) = shadow_p;
shadow_page_for(&page[i]) = &shadow[i];
return shadow_page_for(page) && origin_page_for(page);
shadow_page_for(page) = NULL;