1 #include <linux/kernel.h>
2 #include <linux/string.h>
4 #include <linux/page-debug-flags.h>
5 #include <linux/poison.h>
6 #include <linux/ratelimit.h>
8 static inline void set_page_poison(struct page *page)
10 __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
13 static inline void clear_page_poison(struct page *page)
15 __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
18 static inline bool page_poison(struct page *page)
20 return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
23 static void poison_highpage(struct page *page)
26 * Page poisoning for highmem pages is not implemented.
28 * This can be called from interrupt contexts.
29 * So we need to create a new kmap_atomic slot for this
30 * application and it will need interrupt protection.
34 static void poison_page(struct page *page)
38 if (PageHighMem(page)) {
39 poison_highpage(page);
42 set_page_poison(page);
43 addr = page_address(page);
44 memset(addr, PAGE_POISON, PAGE_SIZE);
47 static void poison_pages(struct page *page, int n)
51 for (i = 0; i < n; i++)
52 poison_page(page + i);
55 static bool single_bit_flip(unsigned char a, unsigned char b)
57 unsigned char error = a ^ b;
59 return error && !(error & (error - 1));
62 static void check_poison_mem(unsigned char *mem, size_t bytes)
64 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
68 start = memchr_inv(mem, PAGE_POISON, bytes);
72 for (end = mem + bytes - 1; end > start; end--) {
73 if (*end != PAGE_POISON)
77 if (!__ratelimit(&ratelimit))
79 else if (start == end && single_bit_flip(*start, PAGE_POISON))
80 printk(KERN_ERR "pagealloc: single bit error\n");
82 printk(KERN_ERR "pagealloc: memory corruption\n");
84 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
89 static void unpoison_highpage(struct page *page)
92 * See comment in poison_highpage().
93 * Highmem pages should not be poisoned for now
95 BUG_ON(page_poison(page));
98 static void unpoison_page(struct page *page)
100 if (PageHighMem(page)) {
101 unpoison_highpage(page);
104 if (page_poison(page)) {
105 void *addr = page_address(page);
107 check_poison_mem(addr, PAGE_SIZE);
108 clear_page_poison(page);
112 static void unpoison_pages(struct page *page, int n)
116 for (i = 0; i < n; i++)
117 unpoison_page(page + i);
120 void kernel_map_pages(struct page *page, int numpages, int enable)
122 if (!debug_pagealloc_enabled)
126 unpoison_pages(page, numpages);
128 poison_pages(page, numpages);