1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * highmem.h: virtual kernel memory mappings for high memory
4  *
5  * Used in CONFIG_HIGHMEM systems for memory pages which
6  * are not addressable by direct kernel virtual addresses.
7  *
8  * Copyright (C) 1999 Gerhard Wichert, Siemens AG
9  *		      Gerhard.Wichert@pdb.siemens.de
10  *
11  *
12  * Redesigned the x86 32-bit VM architecture to deal with
13  * up to 16 Terabyte physical memory. With current x86 CPUs
14  * we now support up to 64 Gigabytes physical RAM.
15  *
16  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17  */
18 #ifndef _ASM_HIGHMEM_H
19 #define _ASM_HIGHMEM_H
20 
21 #ifdef __KERNEL__
22 
23 #include <linux/init.h>
24 #include <linux/interrupt.h>
25 #include <linux/uaccess.h>
26 #include <asm/fixmap.h>
27 
28 extern pte_t *kmap_pte;
29 extern pte_t *pkmap_page_table;
30 
31 /*
32  * Right now we initialize only a single pte table. It can be extended
33  * easily, subsequent pte tables have to be allocated in one physical
34  * chunk of RAM.
35  */
36 /*
37  * We use one full pte table with 4K pages. And with 16K/64K/256K pages pte
38  * table covers enough memory (32MB/512MB/2GB resp.), so that both FIXMAP
39  * and PKMAP can be placed in a single pte table. We use 512 pages for PKMAP
40  * in case of 16K/64K/256K page sizes.
41  */
42 
43 #define PKMAP_ORDER	PTE_SHIFT
44 #define LAST_PKMAP	(1 << PKMAP_ORDER)
45 
46 #define PKMAP_BASE	((FIXADDR_START - PAGE_SIZE * (LAST_PKMAP + 1)) \
47 								& PMD_MASK)
48 
49 #define LAST_PKMAP_MASK	(LAST_PKMAP - 1)
50 #define PKMAP_NR(virt)  ((virt - PKMAP_BASE) >> PAGE_SHIFT)
51 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
52 
53 #define flush_cache_kmaps()	{ flush_icache(); flush_dcache(); }
54 
55 #endif /* __KERNEL__ */
56 
57 #endif /* _ASM_HIGHMEM_H */
58