f9f647cdbc7ba3550e83d82c0c9e6996b3ae8878
[linux-2.6.git] / arch / i386 / mm / highmem.c
1 #include <linux/highmem.h>
2 #include <linux/module.h>
3
4 void *kmap(struct page *page)
5 {
6         might_sleep();
7         if (!PageHighMem(page))
8                 return page_address(page);
9         return kmap_high(page);
10 }
11
12 void kunmap(struct page *page)
13 {
14         if (in_interrupt())
15                 BUG();
16         if (!PageHighMem(page))
17                 return;
18         kunmap_high(page);
19 }
20
21 /*
22  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
23  * no global lock is needed and because the kmap code must perform a global TLB
24  * invalidation when the kmap pool wraps.
25  *
26  * However when holding an atomic kmap is is not legal to sleep, so atomic
27  * kmaps are appropriate for short, tight code paths only.
28  */
29 void *kmap_atomic(struct page *page, enum km_type type)
30 {
31         enum fixed_addresses idx;
32         unsigned long vaddr;
33
34         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
35         inc_preempt_count();
36         if (!PageHighMem(page))
37                 return page_address(page);
38
39         idx = type + KM_TYPE_NR*smp_processor_id();
40         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
41         if (!pte_none(*(kmap_pte-idx)))
42                 BUG();
43         set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
44
45         return (void*) vaddr;
46 }
47
48 void kunmap_atomic(void *kvaddr, enum km_type type)
49 {
50         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
51         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
52
53 #ifdef CONFIG_DEBUG_HIGHMEM
54         if (vaddr >= PAGE_OFFSET && vaddr < (unsigned long)high_memory) {
55                 dec_preempt_count();
56                 preempt_check_resched();
57                 return;
58         }
59
60         if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
61                 BUG();
62 #endif
63         /*
64          * Force other mappings to Oops if they'll try to access this pte
65          * without first remap it.  Keeping stale mappings around is a bad idea
66          * also, in case the page changes cacheability attributes or becomes
67          * a protected page in a hypervisor.
68          */
69         kpte_clear_flush(kmap_pte-idx, vaddr);
70
71         dec_preempt_count();
72         preempt_check_resched();
73 }
74
75 /* This is the same as kmap_atomic() but can map memory that doesn't
76  * have a struct page associated with it.
77  */
78 void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
79 {
80         enum fixed_addresses idx;
81         unsigned long vaddr;
82
83         inc_preempt_count();
84
85         idx = type + KM_TYPE_NR*smp_processor_id();
86         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
87         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
88
89         return (void*) vaddr;
90 }
91
92 struct page *kmap_atomic_to_page(void *ptr)
93 {
94         unsigned long idx, vaddr = (unsigned long)ptr;
95         pte_t *pte;
96
97         if (vaddr < FIXADDR_START)
98                 return virt_to_page(ptr);
99
100         idx = virt_to_fix(vaddr);
101         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
102         return pte_page(*pte);
103 }
104
105 EXPORT_SYMBOL(kmap);
106 EXPORT_SYMBOL(kunmap);
107 EXPORT_SYMBOL(kmap_atomic);
108 EXPORT_SYMBOL(kunmap_atomic);
109 EXPORT_SYMBOL(kmap_atomic_to_page);