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-debug-flags.h>
   6 #include <linux/poison.h>
   7 #include <linux/ratelimit.h>
   8
   9 static inline void set_page_poison(struct page *page)
  10 {
  11         __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  12 }
  13
  14 static inline void clear_page_poison(struct page *page)
  15 {
  16         __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  17 }
  18
  19 static inline bool page_poison(struct page *page)
  20 {
  21         return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  22 }
  23
  24 static void poison_page(struct page *page)
  25 {
  26         void *addr = kmap_atomic(page);
  27
  28         set_page_poison(page);
  29         memset(addr, PAGE_POISON, PAGE_SIZE);
  30         kunmap_atomic(addr);
  31 }
  32
  33 static void poison_pages(struct page *page, int n)
  34 {
  35         int i;
  36
  37         for (i = 0; i < n; i++)
  38                 poison_page(page + i);
  39 }
  40
  41 static bool single_bit_flip(unsigned char a, unsigned char b)
  42 {
  43         unsigned char error = a ^ b;
  44
  45         return error && !(error & (error - 1));
  46 }
  47
  48 static void check_poison_mem(unsigned char *mem, size_t bytes)
  49 {
  50         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
  51         unsigned char *start;
  52         unsigned char *end;
  53
  54         start = memchr_inv(mem, PAGE_POISON, bytes);
  55         if (!start)
  56                 return;
  57
  58         for (end = mem + bytes - 1; end > start; end--) {
  59                 if (*end != PAGE_POISON)
  60                         break;
  61         }
  62
  63         if (!__ratelimit(&ratelimit))
  64                 return;
  65         else if (start == end && single_bit_flip(*start, PAGE_POISON))
  66                 printk(KERN_ERR "pagealloc: single bit error\n");
  67         else
  68                 printk(KERN_ERR "pagealloc: memory corruption\n");
  69
  70         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
  71                         end - start + 1, 1);
  72         dump_stack();
  73 }
  74
  75 static void unpoison_page(struct page *page)
  76 {
  77         void *addr;
  78
  79         if (!page_poison(page))
  80                 return;
  81
  82         addr = kmap_atomic(page);
  83         check_poison_mem(addr, PAGE_SIZE);
  84         clear_page_poison(page);
  85         kunmap_atomic(addr);
  86 }
  87
  88 static void unpoison_pages(struct page *page, int n)
  89 {
  90         int i;
  91
  92         for (i = 0; i < n; i++)
  93                 unpoison_page(page + i);
  94 }
  95
  96 void kernel_map_pages(struct page *page, int numpages, int enable)
  97 {
  98         if (!debug_pagealloc_enabled)
  99                 return;
 100
 101         if (enable)
 102                 unpoison_pages(page, numpages);
 103         else
 104                 poison_pages(page, numpages);
 105 }