highmem.h

linux 内核源代码

/*
 * 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
 *		      [e-mail]
 *
 *
 * Redesigned the x86 32-bit VM architecture to deal with 
 * up to 16 Terrabyte physical memory. With current x86 CPUs
 * we now support up to 64 Gigabytes physical RAM.
 *
 * Copyright (C) 1999 Ingo Molnar <[e-mail]>
 */

#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H

#ifdef __KERNEL__

#include <linux/interrupt.h>
#include <asm/fixmap.h>
#include <asm/vaddrs.h>
#include <asm/kmap_types.h>
#include <asm/pgtable.h>

/* declarations for highmem.c */
extern unsigned long highstart_pfn, highend_pfn;

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

extern void kmap_init(void) __init;

/*
 * 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.  Currently the simplest way to do this is to align the
 * pkmap region on a pagetable boundary (4MB).
 */
#define LAST_PKMAP 1024
#define PKMAP_SIZE (LAST_PKMAP << PAGE_SHIFT)
#define PKMAP_BASE PMD_ALIGN(SRMMU_NOCACHE_VADDR + (SRMMU_MAX_NOCACHE_PAGES << PAGE_SHIFT))

#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))

#define PKMAP_END (PKMAP_ADDR(LAST_PKMAP))

extern void *kmap_high(struct page *page);
extern void kunmap_high(struct page *page);

static inline void *kmap(struct page *page)
{
	BUG_ON(in_interrupt());
	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);
}

extern void *kmap_atomic(struct page *page, enum km_type type);
extern void kunmap_atomic(void *kvaddr, enum km_type type);
extern struct page *kmap_atomic_to_page(void *vaddr);

#define flush_cache_kmaps()	flush_cache_all()

#endif /* __KERNEL__ */

#endif /* _ASM_HIGHMEM_H */