1 #include <linux/kernel.h>
2 #include <linux/string.h>
4 #include <linux/highmem.h>
5 #include <linux/page_ext.h>
6 #include <linux/poison.h>
7 #include <linux/ratelimit.h>
9 static bool page_poisoning_enabled __read_mostly;
11 static bool need_page_poisoning(void)
13 if (!debug_pagealloc_enabled())
19 static void init_page_poisoning(void)
21 if (!debug_pagealloc_enabled())
24 page_poisoning_enabled = true;
27 struct page_ext_operations page_poisoning_ops = {
28 .need = need_page_poisoning,
29 .init = init_page_poisoning,
32 static inline void set_page_poison(struct page *page)
34 struct page_ext *page_ext;
36 page_ext = lookup_page_ext(page);
39 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
42 static inline void clear_page_poison(struct page *page)
44 struct page_ext *page_ext;
46 page_ext = lookup_page_ext(page);
49 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
52 static inline bool page_poison(struct page *page)
54 struct page_ext *page_ext;
56 page_ext = lookup_page_ext(page);
59 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
62 static void poison_page(struct page *page)
64 void *addr = kmap_atomic(page);
66 set_page_poison(page);
67 memset(addr, PAGE_POISON, PAGE_SIZE);
71 static void poison_pages(struct page *page, int n)
75 for (i = 0; i < n; i++)
76 poison_page(page + i);
79 static bool single_bit_flip(unsigned char a, unsigned char b)
81 unsigned char error = a ^ b;
83 return error && !(error & (error - 1));
86 static void check_poison_mem(unsigned char *mem, size_t bytes)
88 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
92 start = memchr_inv(mem, PAGE_POISON, bytes);
96 for (end = mem + bytes - 1; end > start; end--) {
97 if (*end != PAGE_POISON)
101 if (!__ratelimit(&ratelimit))
103 else if (start == end && single_bit_flip(*start, PAGE_POISON))
104 printk(KERN_ERR "pagealloc: single bit error\n");
106 printk(KERN_ERR "pagealloc: memory corruption\n");
108 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
113 static void unpoison_page(struct page *page)
117 if (!page_poison(page))
120 addr = kmap_atomic(page);
121 check_poison_mem(addr, PAGE_SIZE);
122 clear_page_poison(page);
126 static void unpoison_pages(struct page *page, int n)
130 for (i = 0; i < n; i++)
131 unpoison_page(page + i);
134 void __kernel_map_pages(struct page *page, int numpages, int enable)
136 if (!page_poisoning_enabled)
140 unpoison_pages(page, numpages);
142 poison_pages(page, numpages);