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/* SPDX-License-Identifier: GPL-2.0 */
* 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
* 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 <>
#ifndef _ASM_HIGHMEM_H
#define _ASM_HIGHMEM_H
#ifdef __KERNEL__
#include <linux/bug.h>
#include <linux/interrupt.h>
#include <linux/uaccess.h>
#include <asm/cpu-features.h>
#include <asm/kmap_types.h>
/* declarations for highmem.c */
extern unsigned long highstart_pfn, highend_pfn;
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.
#define LAST_PKMAP 512
#define LAST_PKMAP 1024
#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(struct page *page);
extern void kunmap(struct page *page);
extern void *kmap_atomic(struct page *page);
extern void __kunmap_atomic(void *kvaddr);
extern void *kmap_atomic_pfn(unsigned long pfn);
#define flush_cache_kmaps() BUG_ON(cpu_has_dc_aliases)
extern void kmap_init(void);
#define kmap_prot PAGE_KERNEL
#endif /* __KERNEL__ */
#endif /* _ASM_HIGHMEM_H */