1. 根目录:
2. arch
3. microblaze
4. include
5. asm
6. highmem.h

/*
 * highmem.h: virtual kernel memory mappings for high memory
 *
 * Used in CONFIG_HIGHMEM systems for memory pages which
 * are not addressable by direct kernel virtual addresses.
 *
 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
 *		      Gerhard.Wichert@pdb.siemens.de
 *
 *
 * Redesigned the x86 32-bit VM architecture to deal with
 * up to 16 Terabyte physical memory. With current x86 CPUs
 * we now support up to 64 Gigabytes physical RAM.
 *
 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
 */
#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H

#ifdef __KERNEL__

#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <asm/fixmap.h>

extern pte_t *kmap_pte;
extern pgprot_t kmap_prot;
extern pte_t *pkmap_page_table;

/*
 * Right now we initialize only a single pte table. It can be extended
 * easily, subsequent pte tables have to be allocated in one physical
 * chunk of RAM.
 */
/*
 * We use one full pte table with 4K pages. And with 16K/64K/256K pages pte
 * table covers enough memory (32MB/512MB/2GB resp.), so that both FIXMAP
 * and PKMAP can be placed in a single pte table. We use 512 pages for PKMAP
 * in case of 16K/64K/256K page sizes.
 */

#define PKMAP_ORDER	PTE_SHIFT
#define LAST_PKMAP	(1 << PKMAP_ORDER)

#define PKMAP_BASE	((FIXADDR_START - PAGE_SIZE * (LAST_PKMAP + 1)) \
								& PMD_MASK)

#define LAST_PKMAP_MASK	(LAST_PKMAP - 1)
#define PKMAP_NR(virt)  ((virt - PKMAP_BASE) >> PAGE_SHIFT)
#define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))

extern void *kmap_high(struct page *page);
extern void kunmap_high(struct page *page);
extern void *kmap_atomic_prot(struct page *page, pgprot_t prot);
extern void __kunmap_atomic(void *kvaddr);

static inline void *kmap(struct page *page)
{
	might_sleep();
	if (!PageHighMem(page))
		return page_address(page);
	return kmap_high(page);
}

static inline void kunmap(struct page *page)
{
	BUG_ON(in_interrupt());
	if (!PageHighMem(page))
		return;
	kunmap_high(page);
}

static inline void *kmap_atomic(struct page *page)
{
	return kmap_atomic_prot(page, kmap_prot);
}

static inline struct page *kmap_atomic_to_page(void *ptr)
{
	unsigned long idx, vaddr = (unsigned long) ptr;
	pte_t *pte;

	if (vaddr < FIXADDR_START)
		return virt_to_page(ptr);

	idx = virt_to_fix(vaddr);
	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
	return pte_page(*pte);
}

#define flush_cache_kmaps()	{ flush_icache(); flush_dcache(); }

#endif /* __KERNEL__ */

#endif /* _ASM_HIGHMEM_H */