vmemmap
#define vmemmap ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
#define vmemmap ((struct page *)((VMALLOC_END + PMD_SIZE) & PMD_MASK))
#define vmemmap ((struct page *)VMEMMAP_BASE)
#define vmemmap ((struct page *)VMEMMAP_START - vmemmap_start_pfn)
#define vmemmap ((struct page *)VMEMMAP_BASE)
#define vmemmap ((struct page *)VMEMMAP_START)