1 #include <linux/kernel.h>
2 #include <linux/string.h>
3 #include <linux/mm.h>
4 #include <linux/highmem.h>
5 #include <linux/page_ext.h>
6 #include <linux/poison.h>
7 #include <linux/ratelimit.h>
8
9 static bool page_poisoning_enabled __read_mostly;
10
need_page_poisoning(void)11 static bool need_page_poisoning(void)
12 {
13 if (!debug_pagealloc_enabled())
14 return false;
15
16 return true;
17 }
18
init_page_poisoning(void)19 static void init_page_poisoning(void)
20 {
21 if (!debug_pagealloc_enabled())
22 return;
23
24 page_poisoning_enabled = true;
25 }
26
27 struct page_ext_operations page_poisoning_ops = {
28 .need = need_page_poisoning,
29 .init = init_page_poisoning,
30 };
31
set_page_poison(struct page * page)32 static inline void set_page_poison(struct page *page)
33 {
34 struct page_ext *page_ext;
35
36 page_ext = lookup_page_ext(page);
37 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
38 }
39
clear_page_poison(struct page * page)40 static inline void clear_page_poison(struct page *page)
41 {
42 struct page_ext *page_ext;
43
44 page_ext = lookup_page_ext(page);
45 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
46 }
47
page_poison(struct page * page)48 static inline bool page_poison(struct page *page)
49 {
50 struct page_ext *page_ext;
51
52 page_ext = lookup_page_ext(page);
53 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
54 }
55
poison_page(struct page * page)56 static void poison_page(struct page *page)
57 {
58 void *addr = kmap_atomic(page);
59
60 set_page_poison(page);
61 memset(addr, PAGE_POISON, PAGE_SIZE);
62 kunmap_atomic(addr);
63 }
64
poison_pages(struct page * page,int n)65 static void poison_pages(struct page *page, int n)
66 {
67 int i;
68
69 for (i = 0; i < n; i++)
70 poison_page(page + i);
71 }
72
single_bit_flip(unsigned char a,unsigned char b)73 static bool single_bit_flip(unsigned char a, unsigned char b)
74 {
75 unsigned char error = a ^ b;
76
77 return error && !(error & (error - 1));
78 }
79
check_poison_mem(unsigned char * mem,size_t bytes)80 static void check_poison_mem(unsigned char *mem, size_t bytes)
81 {
82 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
83 unsigned char *start;
84 unsigned char *end;
85
86 start = memchr_inv(mem, PAGE_POISON, bytes);
87 if (!start)
88 return;
89
90 for (end = mem + bytes - 1; end > start; end--) {
91 if (*end != PAGE_POISON)
92 break;
93 }
94
95 if (!__ratelimit(&ratelimit))
96 return;
97 else if (start == end && single_bit_flip(*start, PAGE_POISON))
98 printk(KERN_ERR "pagealloc: single bit error\n");
99 else
100 printk(KERN_ERR "pagealloc: memory corruption\n");
101
102 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
103 end - start + 1, 1);
104 dump_stack();
105 }
106
unpoison_page(struct page * page)107 static void unpoison_page(struct page *page)
108 {
109 void *addr;
110
111 if (!page_poison(page))
112 return;
113
114 addr = kmap_atomic(page);
115 check_poison_mem(addr, PAGE_SIZE);
116 clear_page_poison(page);
117 kunmap_atomic(addr);
118 }
119
unpoison_pages(struct page * page,int n)120 static void unpoison_pages(struct page *page, int n)
121 {
122 int i;
123
124 for (i = 0; i < n; i++)
125 unpoison_page(page + i);
126 }
127
__kernel_map_pages(struct page * page,int numpages,int enable)128 void __kernel_map_pages(struct page *page, int numpages, int enable)
129 {
130 if (!page_poisoning_enabled)
131 return;
132
133 if (enable)
134 unpoison_pages(page, numpages);
135 else
136 poison_pages(page, numpages);
137 }
138