mm/debug-pagealloc.c

   1 #include <linux/kernel.h>
   2 #include <linux/mm.h>
   3 #include <linux/page-debug-flags.h>
   4 #include <linux/poison.h>
   5
   6 static inline void set_page_poison(struct page *page)
   7 {
   8         __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
   9 }
  10
  11 static inline void clear_page_poison(struct page *page)
  12 {
  13         __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  14 }
  15
  16 static inline bool page_poison(struct page *page)
  17 {
  18         return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  19 }
  20
  21 static void poison_highpage(struct page *page)
  22 {
  23         /*
  24          * Page poisoning for highmem pages is not implemented.
  25          *
  26          * This can be called from interrupt contexts.
  27          * So we need to create a new kmap_atomic slot for this
  28          * application and it will need interrupt protection.
  29          */
  30 }
  31
  32 static void poison_page(struct page *page)
  33 {
  34         void *addr;
  35
  36         if (PageHighMem(page)) {
  37                 poison_highpage(page);
  38                 return;
  39         }
  40         set_page_poison(page);
  41         addr = page_address(page);
  42         memset(addr, PAGE_POISON, PAGE_SIZE);
  43 }
  44
  45 static void poison_pages(struct page *page, int n)
  46 {
  47         int i;
  48
  49         for (i = 0; i < n; i++)
  50                 poison_page(page + i);
  51 }
  52
  53 static bool single_bit_flip(unsigned char a, unsigned char b)
  54 {
  55         unsigned char error = a ^ b;
  56
  57         return error && !(error & (error - 1));
  58 }
  59
  60 static void check_poison_mem(unsigned char *mem, size_t bytes)
  61 {
  62         unsigned char *start;
  63         unsigned char *end;
  64
  65         for (start = mem; start < mem + bytes; start++) {
  66                 if (*start != PAGE_POISON)
  67                         break;
  68         }
  69         if (start == mem + bytes)
  70                 return;
  71
  72         for (end = mem + bytes - 1; end > start; end--) {
  73                 if (*end != PAGE_POISON)
  74                         break;
  75         }
  76
  77         if (!printk_ratelimit())
  78                 return;
  79         else if (start == end && single_bit_flip(*start, PAGE_POISON))
  80                 printk(KERN_ERR "pagealloc: single bit error\n");
  81         else
  82                 printk(KERN_ERR "pagealloc: memory corruption\n");
  83
  84         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
  85                         end - start + 1, 1);
  86         dump_stack();
  87 }
  88
  89 static void unpoison_highpage(struct page *page)
  90 {
  91         /*
  92          * See comment in poison_highpage().
  93          * Highmem pages should not be poisoned for now
  94          */
  95         BUG_ON(page_poison(page));
  96 }
  97
  98 static void unpoison_page(struct page *page)
  99 {
 100         if (PageHighMem(page)) {
 101                 unpoison_highpage(page);
 102                 return;
 103         }
 104         if (page_poison(page)) {
 105                 void *addr = page_address(page);
 106
 107                 check_poison_mem(addr, PAGE_SIZE);
 108                 clear_page_poison(page);
 109         }
 110 }
 111
 112 static void unpoison_pages(struct page *page, int n)
 113 {
 114         int i;
 115
 116         for (i = 0; i < n; i++)
 117                 unpoison_page(page + i);
 118 }
 119
 120 void kernel_map_pages(struct page *page, int numpages, int enable)
 121 {
 122         if (!debug_pagealloc_enabled)
 123                 return;
 124
 125         if (enable)
 126                 unpoison_pages(page, numpages);
 127         else
 128                 poison_pages(page, numpages);
 129 }