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highmem.h
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1 /*
2  * highmem.h: virtual kernel memory mappings for high memory
3  *
4  * Used in CONFIG_HIGHMEM systems for memory pages which
5  * are not addressable by direct kernel virtual addresses.
6  *
7  * Copyright (C) 1999 Gerhard Wichert, Siemens AG
9  *
10  *
11  * Redesigned the x86 32-bit VM architecture to deal with
12  * up to 16 Terabyte physical memory. With current x86 CPUs
13  * we now support up to 64 Gigabytes physical RAM.
14  *
15  * Copyright (C) 1999 Ingo Molnar <[email protected]>
16  */
17 #ifndef _ASM_HIGHMEM_H
18 #define _ASM_HIGHMEM_H
19 
20 #ifdef __KERNEL__
21 
22 #include <linux/init.h>
23 #include <linux/interrupt.h>
24 #include <linux/uaccess.h>
25 #include <asm/fixmap.h>
26 
27 extern pte_t *kmap_pte;
28 extern pgprot_t kmap_prot;
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 extern void *kmap_high(struct page *page);
54 extern void kunmap_high(struct page *page);
55 extern void *kmap_atomic_prot(struct page *page, pgprot_t prot);
56 extern void __kunmap_atomic(void *kvaddr);
57 
58 static inline void *kmap(struct page *page)
59 {
60  might_sleep();
61  if (!PageHighMem(page))
62  return page_address(page);
63  return kmap_high(page);
64 }
65 
66 static inline void kunmap(struct page *page)
67 {
69  if (!PageHighMem(page))
70  return;
71  kunmap_high(page);
72 }
73 
74 static inline void *__kmap_atomic(struct page *page)
75 {
76  return kmap_atomic_prot(page, kmap_prot);
77 }
78 
79 static inline struct page *kmap_atomic_to_page(void *ptr)
80 {
81  unsigned long idx, vaddr = (unsigned long) ptr;
82  pte_t *pte;
83 
84  if (vaddr < FIXADDR_START)
85  return virt_to_page(ptr);
86 
87  idx = virt_to_fix(vaddr);
88  pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
89  return pte_page(*pte);
90 }
91 
92 #define flush_cache_kmaps() { flush_icache(); flush_dcache(); }
93 
94 #endif /* __KERNEL__ */
95 
96 #endif /* _ASM_HIGHMEM_H */