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)
16 static void init_page_poisoning(void)
18 page_poisoning_enabled = true;
21 struct page_ext_operations page_poisoning_ops = {
22 .need = need_page_poisoning,
23 .init = init_page_poisoning,
26 static inline void set_page_poison(struct page *page)
28 struct page_ext *page_ext;
30 page_ext = lookup_page_ext(page);
31 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
34 static inline void clear_page_poison(struct page *page)
36 struct page_ext *page_ext;
38 page_ext = lookup_page_ext(page);
39 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
42 static inline bool page_poison(struct page *page)
44 struct page_ext *page_ext;
46 page_ext = lookup_page_ext(page);
47 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
50 static void poison_page(struct page *page)
52 void *addr = kmap_atomic(page);
54 set_page_poison(page);
55 memset(addr, PAGE_POISON, PAGE_SIZE);
59 static void poison_pages(struct page *page, int n)
63 for (i = 0; i < n; i++)
64 poison_page(page + i);
67 static bool single_bit_flip(unsigned char a, unsigned char b)
69 unsigned char error = a ^ b;
71 return error && !(error & (error - 1));
74 static void check_poison_mem(unsigned char *mem, size_t bytes)
76 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
80 start = memchr_inv(mem, PAGE_POISON, bytes);
84 for (end = mem + bytes - 1; end > start; end--) {
85 if (*end != PAGE_POISON)
89 if (!__ratelimit(&ratelimit))
91 else if (start == end && single_bit_flip(*start, PAGE_POISON))
92 printk(KERN_ERR "pagealloc: single bit error\n");
94 printk(KERN_ERR "pagealloc: memory corruption\n");
96 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
101 static void unpoison_page(struct page *page)
105 if (!page_poison(page))
108 addr = kmap_atomic(page);
109 check_poison_mem(addr, PAGE_SIZE);
110 clear_page_poison(page);
114 static void unpoison_pages(struct page *page, int n)
118 for (i = 0; i < n; i++)
119 unpoison_page(page + i);
122 void kernel_map_pages(struct page *page, int numpages, int enable)
124 if (!page_poisoning_enabled)
128 unpoison_pages(page, numpages);
130 poison_pages(page, numpages);