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);
37 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
40 static inline void clear_page_poison(struct page *page)
42 struct page_ext *page_ext;
44 page_ext = lookup_page_ext(page);
45 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
48 static inline bool page_poison(struct page *page)
50 struct page_ext *page_ext;
52 page_ext = lookup_page_ext(page);
53 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
56 static void poison_page(struct page *page)
58 void *addr = kmap_atomic(page);
60 set_page_poison(page);
61 memset(addr, PAGE_POISON, PAGE_SIZE);
65 static void poison_pages(struct page *page, int n)
69 for (i = 0; i < n; i++)
70 poison_page(page + i);
73 static bool single_bit_flip(unsigned char a, unsigned char b)
75 unsigned char error = a ^ b;
77 return error && !(error & (error - 1));
80 static void check_poison_mem(unsigned char *mem, size_t bytes)
82 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
86 start = memchr_inv(mem, PAGE_POISON, bytes);
90 for (end = mem + bytes - 1; end > start; end--) {
91 if (*end != PAGE_POISON)
95 if (!__ratelimit(&ratelimit))
97 else if (start == end && single_bit_flip(*start, PAGE_POISON))
98 printk(KERN_ERR "pagealloc: single bit error\n");
100 printk(KERN_ERR "pagealloc: memory corruption\n");
102 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
107 static void unpoison_page(struct page *page)
111 if (!page_poison(page))
114 addr = kmap_atomic(page);
115 check_poison_mem(addr, PAGE_SIZE);
116 clear_page_poison(page);
120 static void unpoison_pages(struct page *page, int n)
124 for (i = 0; i < n; i++)
125 unpoison_page(page + i);
128 void __kernel_map_pages(struct page *page, int numpages, int enable)
130 if (!page_poisoning_enabled)
134 unpoison_pages(page, numpages);
136 poison_pages(page, numpages);