highmem.h revision 9bf2b5cdc5fe5e3136ceeecc85141765023ded6e 
1/*
2 * highmem.h: virtual kernel memory mappings for high memory
3 *
4 * PowerPC version, stolen from the i386 version.
5 *
6 * Used in CONFIG_HIGHMEM systems for memory pages which
7 * are not addressable by direct kernel virtual addresses.
8 *
9 * Copyright (C) 1999 Gerhard Wichert, Siemens AG
10 *		      Gerhard.Wichert@pdb.siemens.de
11 *
12 *
13 * Redesigned the x86 32-bit VM architecture to deal with
14 * up to 16 Terrabyte physical memory. With current x86 CPUs
15 * we now support up to 64 Gigabytes physical RAM.
16 *
17 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
18 */
19
20#ifndef _ASM_HIGHMEM_H
21#define _ASM_HIGHMEM_H
22
23#ifdef __KERNEL__
24
25#include <linux/init.h>
26#include <linux/interrupt.h>
27#include <asm/kmap_types.h>
28#include <asm/tlbflush.h>
29#include <asm/page.h>
30#include <asm/fixmap.h>
31
32extern pte_t *kmap_pte;
33extern pgprot_t kmap_prot;
34extern pte_t *pkmap_page_table;
35
36/*
37 * Right now we initialize only a single pte table. It can be extended
38 * easily, subsequent pte tables have to be allocated in one physical
39 * chunk of RAM.
40 */
41#define LAST_PKMAP 	(1 << PTE_SHIFT)
42#define LAST_PKMAP_MASK (LAST_PKMAP-1)
43#define PKMAP_BASE	((FIXADDR_START - PAGE_SIZE*(LAST_PKMAP + 1)) & PMD_MASK)
44#define PKMAP_NR(virt)  ((virt-PKMAP_BASE) >> PAGE_SHIFT)
45#define PKMAP_ADDR(nr)  (PKMAP_BASE + ((nr) << PAGE_SHIFT))
46
47extern void *kmap_high(struct page *page);
48extern void kunmap_high(struct page *page);
49
50static inline void *kmap(struct page *page)
51{
52	might_sleep();
53	if (!PageHighMem(page))
54		return page_address(page);
55	return kmap_high(page);
56}
57
58static inline void kunmap(struct page *page)
59{
60	BUG_ON(in_interrupt());
61	if (!PageHighMem(page))
62		return;
63	kunmap_high(page);
64}
65
66/*
67 * The use of kmap_atomic/kunmap_atomic is discouraged - kmap/kunmap
68 * gives a more generic (and caching) interface. But kmap_atomic can
69 * be used in IRQ contexts, so in some (very limited) cases we need
70 * it.
71 */
72static inline void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
73{
74	unsigned int idx;
75	unsigned long vaddr;
76
77	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
78	pagefault_disable();
79	if (!PageHighMem(page))
80		return page_address(page);
81
82	idx = type + KM_TYPE_NR*smp_processor_id();
83	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
84#ifdef CONFIG_DEBUG_HIGHMEM
85	BUG_ON(!pte_none(*(kmap_pte-idx)));
86#endif
87	__set_pte_at(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
88	flush_tlb_page(NULL, vaddr);
89
90	return (void*) vaddr;
91}
92
93static inline void *kmap_atomic(struct page *page, enum km_type type)
94{
95	return kmap_atomic_prot(page, type, kmap_prot);
96}
97
98static inline void kunmap_atomic(void *kvaddr, enum km_type type)
99{
100#ifdef CONFIG_DEBUG_HIGHMEM
101	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
102	enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
103
104	if (vaddr < __fix_to_virt(FIX_KMAP_END)) {
105		pagefault_enable();
106		return;
107	}
108
109	BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
110
111	/*
112	 * force other mappings to Oops if they'll try to access
113	 * this pte without first remap it
114	 */
115	pte_clear(&init_mm, vaddr, kmap_pte-idx);
116	flush_tlb_page(NULL, vaddr);
117#endif
118	pagefault_enable();
119}
120
121static inline struct page *kmap_atomic_to_page(void *ptr)
122{
123	unsigned long idx, vaddr = (unsigned long) ptr;
124	pte_t *pte;
125
126	if (vaddr < FIXADDR_START)
127		return virt_to_page(ptr);
128
129	idx = virt_to_fix(vaddr);
130	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
131	return pte_page(*pte);
132}
133
134#define flush_cache_kmaps()	flush_cache_all()
135
136#endif /* __KERNEL__ */
137
138#endif /* _ASM_HIGHMEM_H */
139