aboutsummaryrefslogtreecommitdiffstats
path: root/arch/i386/mm/highmem.c
blob: 4b7aaf99d7ea7a1d9a19d2f821070fd4d1a85c4f (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
#include <linux/highmem.h>
#include <linux/module.h>

void *kmap(struct page *page)
{
	might_sleep();
	if (!PageHighMem(page))
		return page_address(page);
	return kmap_high(page);
}

void kunmap(struct page *page)
{
	if (in_interrupt())
		BUG();
	if (!PageHighMem(page))
		return;
	kunmap_high(page);
}

/*
 * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
 * no global lock is needed and because the kmap code must perform a global TLB
 * invalidation when the kmap pool wraps.
 *
 * However when holding an atomic kmap is is not legal to sleep, so atomic
 * kmaps are appropriate for short, tight code paths only.
 */
void *kmap_atomic(struct page *page, enum km_type type)
{
	enum fixed_addresses idx;
	unsigned long vaddr;

	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
	inc_preempt_count();
	if (!PageHighMem(page))
		return page_address(page);

	idx = type + KM_TYPE_NR*smp_processor_id();
	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
	if (!pte_none(*(kmap_pte-idx)))
		BUG();
#endif
	set_pte(kmap_pte-idx, mk_pte(page, kmap_prot));
	__flush_tlb_one(vaddr);

	return (void*) vaddr;
}

void kunmap_atomic(void *kvaddr, enum km_type type)
{
#ifdef CONFIG_DEBUG_HIGHMEM
	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
	enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();

	if (vaddr < FIXADDR_START) { // FIXME
		dec_preempt_count();
		preempt_check_resched();
		return;
	}

	if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
		BUG();

	/*
	 * force other mappings to Oops if they'll try to access
	 * this pte without first remap it
	 */
	pte_clear(&init_mm, vaddr, kmap_pte-idx);
	__flush_tlb_one(vaddr);
#endif

	dec_preempt_count();
	preempt_check_resched();
}

struct page *kmap_atomic_to_page(void *ptr)
{
	unsigned long idx, vaddr = (unsigned long)ptr;
	pte_t *pte;

	if (vaddr < FIXADDR_START)
		return virt_to_page(ptr);

	idx = virt_to_fix(vaddr);
	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
	return pte_page(*pte);
}

EXPORT_SYMBOL(kmap);
EXPORT_SYMBOL(kunmap);
EXPORT_SYMBOL(kmap_atomic);
EXPORT_SYMBOL(kunmap_atomic);
EXPORT_SYMBOL(kmap_atomic_to_page);