summaryrefslogtreecommitdiffstats
path: root/mm/debug-pagealloc.c
blob: 5bf5906ce13b7316ccb3ff3d101ff6cff00c6818 (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
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/page_ext.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>

static bool page_poisoning_enabled __read_mostly;

static bool need_page_poisoning(void)
{
	if (!debug_pagealloc_enabled())
		return false;

	return true;
}

static void init_page_poisoning(void)
{
	if (!debug_pagealloc_enabled())
		return;

	page_poisoning_enabled = true;
}

struct page_ext_operations page_poisoning_ops = {
	.need = need_page_poisoning,
	.init = init_page_poisoning,
};

static inline void set_page_poison(struct page *page)
{
	struct page_ext *page_ext;

	page_ext = lookup_page_ext(page);
	__set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}

static inline void clear_page_poison(struct page *page)
{
	struct page_ext *page_ext;

	page_ext = lookup_page_ext(page);
	__clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}

static inline bool page_poison(struct page *page)
{
	struct page_ext *page_ext;

	page_ext = lookup_page_ext(page);
	return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}

static void poison_page(struct page *page)
{
	void *addr = kmap_atomic(page);

	set_page_poison(page);
	memset(addr, PAGE_POISON, PAGE_SIZE);
	kunmap_atomic(addr);
}

static void poison_pages(struct page *page, int n)
{
	int i;

	for (i = 0; i < n; i++)
		poison_page(page + i);
}

static bool single_bit_flip(unsigned char a, unsigned char b)
{
	unsigned char error = a ^ b;

	return error && !(error & (error - 1));
}

static void check_poison_mem(unsigned char *mem, size_t bytes)
{
	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
	unsigned char *start;
	unsigned char *end;

	start = memchr_inv(mem, PAGE_POISON, bytes);
	if (!start)
		return;

	for (end = mem + bytes - 1; end > start; end--) {
		if (*end != PAGE_POISON)
			break;
	}

	if (!__ratelimit(&ratelimit))
		return;
	else if (start == end && single_bit_flip(*start, PAGE_POISON))
		printk(KERN_ERR "pagealloc: single bit error\n");
	else
		printk(KERN_ERR "pagealloc: memory corruption\n");

	print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
			end - start + 1, 1);
	dump_stack();
}

static void unpoison_page(struct page *page)
{
	void *addr;

	if (!page_poison(page))
		return;

	addr = kmap_atomic(page);
	check_poison_mem(addr, PAGE_SIZE);
	clear_page_poison(page);
	kunmap_atomic(addr);
}

static void unpoison_pages(struct page *page, int n)
{
	int i;

	for (i = 0; i < n; i++)
		unpoison_page(page + i);
}

void __kernel_map_pages(struct page *page, int numpages, int enable)
{
	if (!page_poisoning_enabled)
		return;

	if (enable)
		unpoison_pages(page, numpages);
	else
		poison_pages(page, numpages);
}