1#include <linux/kernel.h>
2#include <linux/mm.h>
3#include <linux/page-debug-flags.h>
4#include <linux/poison.h>
5
6static inline void set_page_poison(struct page *page)
7{
8 __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
9}
10
11static inline void clear_page_poison(struct page *page)
12{
13 __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
14}
15
16static inline bool page_poison(struct page *page)
17{
18 return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
19}
20
21static void poison_highpage(struct page *page)
22{
23
24
25
26
27
28
29
30}
31
32static void poison_page(struct page *page)
33{
34 void *addr;
35
36 if (PageHighMem(page)) {
37 poison_highpage(page);
38 return;
39 }
40 set_page_poison(page);
41 addr = page_address(page);
42 memset(addr, PAGE_POISON, PAGE_SIZE);
43}
44
45static void poison_pages(struct page *page, int n)
46{
47 int i;
48
49 for (i = 0; i < n; i++)
50 poison_page(page + i);
51}
52
53static bool single_bit_flip(unsigned char a, unsigned char b)
54{
55 unsigned char error = a ^ b;
56
57 return error && !(error & (error - 1));
58}
59
60static void check_poison_mem(unsigned char *mem, size_t bytes)
61{
62 unsigned char *start;
63 unsigned char *end;
64
65 for (start = mem; start < mem + bytes; start++) {
66 if (*start != PAGE_POISON)
67 break;
68 }
69 if (start == mem + bytes)
70 return;
71
72 for (end = mem + bytes - 1; end > start; end--) {
73 if (*end != PAGE_POISON)
74 break;
75 }
76
77 if (!printk_ratelimit())
78 return;
79 else if (start == end && single_bit_flip(*start, PAGE_POISON))
80 printk(KERN_ERR "pagealloc: single bit error\n");
81 else
82 printk(KERN_ERR "pagealloc: memory corruption\n");
83
84 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
85 end - start + 1, 1);
86 dump_stack();
87}
88
89static void unpoison_highpage(struct page *page)
90{
91
92
93
94
95 BUG_ON(page_poison(page));
96}
97
98static void unpoison_page(struct page *page)
99{
100 if (PageHighMem(page)) {
101 unpoison_highpage(page);
102 return;
103 }
104 if (page_poison(page)) {
105 void *addr = page_address(page);
106
107 check_poison_mem(addr, PAGE_SIZE);
108 clear_page_poison(page);
109 }
110}
111
112static void unpoison_pages(struct page *page, int n)
113{
114 int i;
115
116 for (i = 0; i < n; i++)
117 unpoison_page(page + i);
118}
119
120void kernel_map_pages(struct page *page, int numpages, int enable)
121{
122 if (!debug_pagealloc_enabled)
123 return;
124
125 if (enable)
126 unpoison_pages(page, numpages);
127 else
128 poison_pages(page, numpages);
129}
130