mm/debug-pagealloc.c

   1 #include <linux/kernel.h>
   2 #include <linux/string.h>
   3 #include <linux/mm.h>
   4 #include <linux/page-debug-flags.h>
   5 #include <linux/poison.h>
   6 #include <linux/ratelimit.h>
   7
   8 static inline void set_page_poison(struct page *page)
   9 {
  10         __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  11 }
  12
  13 static inline void clear_page_poison(struct page *page)
  14 {
  15         __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  16 }
  17
  18 static inline bool page_poison(struct page *page)
  19 {
  20         return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  21 }
  22
  23 static void poison_highpage(struct page *page)
  24 {
  25         /*
  26          * Page poisoning for highmem pages is not implemented.
  27          *
  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.
  31          */
  32 }
  33
  34 static void poison_page(struct page *page)
  35 {
  36         void *addr;
  37
  38         if (PageHighMem(page)) {
  39                 poison_highpage(page);
  40                 return;
  41         }
  42         set_page_poison(page);
  43         addr = page_address(page);
  44         memset(addr, PAGE_POISON, PAGE_SIZE);
  45 }
  46
  47 static void poison_pages(struct page *page, int n)
  48 {
  49         int i;
  50
  51         for (i = 0; i < n; i++)
  52                 poison_page(page + i);
  53 }
  54
  55 static bool single_bit_flip(unsigned char a, unsigned char b)
  56 {
  57         unsigned char error = a ^ b;
  58
  59         return error && !(error & (error - 1));
  60 }
  61
  62 static void check_poison_mem(unsigned char *mem, size_t bytes)
  63 {
  64         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
  65         unsigned char *start;
  66         unsigned char *end;
  67
  68         start = memchr_inv(mem, PAGE_POISON, bytes);
  69         if (!start)
  70                 return;
  71
  72         for (end = mem + bytes - 1; end > start; end--) {
  73                 if (*end != PAGE_POISON)
  74                         break;
  75         }
  76
  77         if (!__ratelimit(&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 }