page.h

LINUX1.0内核源代码,学习LINUX编程的一定要看。

#ifndef _LINUX_PAGE_H
#define _LINUX_PAGE_H

			/* PAGE_SHIFT determines the page size */
#define PAGE_SHIFT			12
#define PAGE_SIZE			((unsigned long)1<<PAGE_SHIFT)

#ifdef __KERNEL__

			/* number of bits that fit into a memory pointer */
#define BITS_PER_PTR			(8*sizeof(unsigned long))
			/* to mask away the intra-page address bits */
#define PAGE_MASK			(~(PAGE_SIZE-1))
			/* to align the pointer to the (next) page boundary */
#define PAGE_ALIGN(addr)		(((addr)+PAGE_SIZE-1)&PAGE_MASK)
			/* to align the pointer to a pointer address */
#define PTR_MASK			(~(sizeof(void*)-1))

					/* sizeof(void*)==1<<SIZEOF_PTR_LOG2 */
					/* 64-bit machines, beware!  SRB. */
#define SIZEOF_PTR_LOG2			2

			/* to find an entry in a page-table-directory */
#define PAGE_DIR_OFFSET(base,address)	((unsigned long*)((base)+\
  ((unsigned long)(address)>>(PAGE_SHIFT-SIZEOF_PTR_LOG2)*2&PTR_MASK&~PAGE_MASK)))
			/* to find an entry in a page-table */
#define PAGE_PTR(address)		\
  ((unsigned long)(address)>>(PAGE_SHIFT-SIZEOF_PTR_LOG2)&PTR_MASK&~PAGE_MASK)
			/* the no. of pointers that fit on a page */
#define PTRS_PER_PAGE			(PAGE_SIZE/sizeof(void*))

#endif /* __KERNEL__ */

#endif /* _LINUX_PAGE_H */