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 pgprot_t kmap_prot;
30 extern pte_t *pkmap_page_table;
31 
32 /*
33  * Right now we initialize only a single pte table. It can be extended
34  * easily, subsequent pte tables have to be allocated in one physical
35  * chunk of RAM.
36  */
37 /*
38  * We use one full pte table with 4K pages. And with 16K/64K/256K pages pte
39  * table covers enough memory (32MB/512MB/2GB resp.), so that both FIXMAP
40  * and PKMAP can be placed in a single pte table. We use 512 pages for PKMAP
41  * in case of 16K/64K/256K page sizes.
42  */
43 
44 #define PKMAP_ORDER	PTE_SHIFT
45 #define LAST_PKMAP	(1 << PKMAP_ORDER)
46 
47 #define PKMAP_BASE	((FIXADDR_START - PAGE_SIZE * (LAST_PKMAP + 1)) \
48 								& PMD_MASK)
49 
50 #define LAST_PKMAP_MASK	(LAST_PKMAP - 1)
51 #define PKMAP_NR(virt)  ((virt - PKMAP_BASE) >> PAGE_SHIFT)
52 #define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
53 
54 extern void *kmap_high(struct page *page);
55 extern void kunmap_high(struct page *page);
56 extern void *kmap_atomic_prot(struct page *page, pgprot_t prot);
57 extern void __kunmap_atomic(void *kvaddr);
58 
59 static inline void *kmap(struct page *page)
60 {
61 	might_sleep();
62 	if (!PageHighMem(page))
63 		return page_address(page);
64 	return kmap_high(page);
65 }
66 
67 static inline void kunmap(struct page *page)
68 {
69 	BUG_ON(in_interrupt());
70 	if (!PageHighMem(page))
71 		return;
72 	kunmap_high(page);
73 }
74 
75 static inline void *kmap_atomic(struct page *page)
76 {
77 	return kmap_atomic_prot(page, kmap_prot);
78 }
79 
80 #define flush_cache_kmaps()	{ flush_icache(); flush_dcache(); }
81 
82 #endif /* __KERNEL__ */
83 
84 #endif /* _ASM_HIGHMEM_H */
85