mm/debug-pagealloc.c

   1 #include <linux/kernel.h>
   2 #include <linux/string.h>
   3 #include <linux/mm.h>
   4 #include <linux/highmem.h>
   5 #include <linux/page_ext.h>
   6 #include <linux/poison.h>
   7 #include <linux/ratelimit.h>
   8
   9 static bool page_poisoning_enabled __read_mostly;
  10
  11 static bool need_page_poisoning(void)
  12 {
  13         if (!debug_pagealloc_enabled())
  14                 return false;
  15
  16         return true;
  17 }
  18
  19 static void init_page_poisoning(void)
  20 {
  21         if (!debug_pagealloc_enabled())
  22                 return;
  23
  24         page_poisoning_enabled = true;
  25 }
  26
  27 struct page_ext_operations page_poisoning_ops = {
  28         .need = need_page_poisoning,
  29         .init = init_page_poisoning,
  30 };
  31
  32 static inline void set_page_poison(struct page *page)
  33 {
  34         struct page_ext *page_ext;
  35
  36         page_ext = lookup_page_ext(page);
  37         __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  38 }
  39
  40 static inline void clear_page_poison(struct page *page)
  41 {
  42         struct page_ext *page_ext;
  43
  44         page_ext = lookup_page_ext(page);
  45         __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  46 }
  47
  48 static inline bool page_poison(struct page *page)
  49 {
  50         struct page_ext *page_ext;
  51
  52         page_ext = lookup_page_ext(page);
  53         return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  54 }
  55
  56 static void poison_page(struct page *page)
  57 {
  58         void *addr = kmap_atomic(page);
  59
  60         set_page_poison(page);
  61         memset(addr, PAGE_POISON, PAGE_SIZE);
  62         kunmap_atomic(addr);
  63 }
  64
  65 static void poison_pages(struct page *page, int n)
  66 {
  67         int i;
  68
  69         for (i = 0; i < n; i++)
  70                 poison_page(page + i);
  71 }
  72
  73 static bool single_bit_flip(unsigned char a, unsigned char b)
  74 {
  75         unsigned char error = a ^ b;
  76
  77         return error && !(error & (error - 1));
  78 }
  79
  80 static void check_poison_mem(unsigned char *mem, size_t bytes)
  81 {
  82         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
  83         unsigned char *start;
  84         unsigned char *end;
  85
  86         start = memchr_inv(mem, PAGE_POISON, bytes);
  87         if (!start)
  88                 return;
  89
  90         for (end = mem + bytes - 1; end > start; end--) {
  91                 if (*end != PAGE_POISON)
  92                         break;
  93         }
  94
  95         if (!__ratelimit(&ratelimit))
  96                 return;
  97         else if (start == end && single_bit_flip(*start, PAGE_POISON))
  98                 printk(KERN_ERR "pagealloc: single bit error\n");
  99         else
 100                 printk(KERN_ERR "pagealloc: memory corruption\n");
 101
 102         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
 103                         end - start + 1, 1);
 104         dump_stack();
 105 }
 106
 107 static void unpoison_page(struct page *page)
 108 {
 109         void *addr;
 110
 111         if (!page_poison(page))
 112                 return;
 113
 114         addr = kmap_atomic(page);
 115         check_poison_mem(addr, PAGE_SIZE);
 116         clear_page_poison(page);
 117         kunmap_atomic(addr);
 118 }
 119
 120 static void unpoison_pages(struct page *page, int n)
 121 {
 122         int i;
 123
 124         for (i = 0; i < n; i++)
 125                 unpoison_page(page + i);
 126 }
 127
 128 void __kernel_map_pages(struct page *page, int numpages, int enable)
 129 {
 130         if (!page_poisoning_enabled)
 131                 return;
 132
 133         if (enable)
 134                 unpoison_pages(page, numpages);
 135         else
 136                 poison_pages(page, numpages);
 137 }