#ifndef _ASM_PGALLOC_H#define _ASM_PGALLOC_H #include <linux/gfp.h>#include <linux/mm.h>#include <linux/threads.h>#include <asm/processor.h>#include <asm/fixmap.h> #include <asm/cache.h> /* Allocate the top level pgd (page directory) * * Here (for 64 bit kernels) we implement a Hybrid L2/L3 scheme: we * allocate the first pmd adjacent to the pgd.  This means that we can * subtract a constant offset to get to it.  The pmd and pgd sizes are * arranged so that a single pmd covers 4GB (giving a full 64-bit * process access to 8TB) so our lookups are effectively L2 for the * first 4GB of the kernel (i.e. for all ILP32 processes and all the * kernel for machines with under 4GB of memory) */static inline pgd_t *pgd_alloc(struct mm_struct *mm){	pgd_t *pgd = (pgd_t *)__get_free_pages(GFP_KERNEL,					       PGD_ALLOC_ORDER);	pgd_t *actual_pgd = pgd; 	if (likely(pgd != NULL)) {		memset(pgd, 0, PAGE_SIZE<<PGD_ALLOC_ORDER);#ifdef CONFIG_64BIT		actual_pgd += PTRS_PER_PGD;		/* Populate first pmd with allocated memory.  We mark it		 * with PxD_FLAG_ATTACHED as a signal to the system that this		 * pmd entry may not be cleared. */		__pgd_val_set(*actual_pgd, (PxD_FLAG_PRESENT | 				        PxD_FLAG_VALID | 					PxD_FLAG_ATTACHED) 			+ (__u32)(__pa((unsigned long)pgd) >> PxD_VALUE_SHIFT));		/* The first pmd entry also is marked with _PAGE_GATEWAY as		 * a signal that this pmd may not be freed */		__pgd_val_set(*pgd, PxD_FLAG_ATTACHED);#endif	}	return actual_pgd;} static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd){#ifdef CONFIG_64BIT	pgd -= PTRS_PER_PGD;#endif	free_pages((unsigned long)pgd, PGD_ALLOC_ORDER);} #if PT_NLEVELS == 3 /* Three Level Page Table Support for pmd's */ static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmd){	__pgd_val_set(*pgd, (PxD_FLAG_PRESENT | PxD_FLAG_VALID) +		        (__u32)(__pa((unsigned long)pmd) >> PxD_VALUE_SHIFT));} static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long address){	pmd_t *pmd = (pmd_t *)__get_free_pages(GFP_KERNEL|__GFP_REPEAT,					       PMD_ORDER);	if (pmd)		memset(pmd, 0, PAGE_SIZE<<PMD_ORDER);	return pmd;} static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd){#ifdef CONFIG_64BIT	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)		/* This is the permanent pmd attached to the pgd;		 * cannot free it */		return;#endif	free_pages((unsigned long)pmd, PMD_ORDER);} #else /* Two Level Page Table Support for pmd's */ /* * allocating and freeing a pmd is trivial: the 1-entry pmd is * inside the pgd, so has no extra memory associated with it. */ #define pmd_alloc_one(mm, addr)		({ BUG(); ((pmd_t *)2); })#define pmd_free(mm, x)			do { } while (0)#define pgd_populate(mm, pmd, pte)	BUG() #endif static inline voidpmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd, pte_t *pte){#ifdef CONFIG_64BIT	/* preserve the gateway marker if this is the beginning of	 * the permanent pmd */	if(pmd_flag(*pmd) & PxD_FLAG_ATTACHED)		__pmd_val_set(*pmd, (PxD_FLAG_PRESENT |				 PxD_FLAG_VALID |				 PxD_FLAG_ATTACHED) 			+ (__u32)(__pa((unsigned long)pte) >> PxD_VALUE_SHIFT));	else#endif		__pmd_val_set(*pmd, (PxD_FLAG_PRESENT | PxD_FLAG_VALID) 			+ (__u32)(__pa((unsigned long)pte) >> PxD_VALUE_SHIFT));} #define pmd_populate(mm, pmd, pte_page) \	pmd_populate_kernel(mm, pmd, page_address(pte_page))#define pmd_pgtable(pmd) pmd_page(pmd) static inline pgtable_tpte_alloc_one(struct mm_struct *mm, unsigned long address){	struct page *page = alloc_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);	if (page)		pgtable_page_ctor(page);	return page;} static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long addr){	pte_t *pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);	return pte;} static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte){	free_page((unsigned long)pte);} static inline void pte_free(struct mm_struct *mm, struct page *pte){	pgtable_page_dtor(pte);	pte_free_kernel(mm, page_address(pte));} #define check_pgt_cache()	do { } while (0) #endif