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         if (!page_ext)
  38                 return;
  39         __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  40 }
  41
  42 static inline void clear_page_poison(struct page *page)
  43 {
  44         struct page_ext *page_ext;
  45
  46         page_ext = lookup_page_ext(page);
  47         if (!page_ext)
  48                 return;
  49         __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  50 }
  51
  52 static inline bool page_poison(struct page *page)
  53 {
  54         struct page_ext *page_ext;
  55
  56         page_ext = lookup_page_ext(page);
  57         if (!page_ext)
  58                 return false;
  59         return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  60 }
  61
  62 static void poison_page(struct page *page)
  63 {
  64         void *addr = kmap_atomic(page);
  65
  66         set_page_poison(page);
  67         memset(addr, PAGE_POISON, PAGE_SIZE);
  68         kunmap_atomic(addr);
  69 }
  70
  71 static void poison_pages(struct page *page, int n)
  72 {
  73         int i;
  74
  75         for (i = 0; i < n; i++)
  76                 poison_page(page + i);
  77 }
  78
  79 static bool single_bit_flip(unsigned char a, unsigned char b)
  80 {
  81         unsigned char error = a ^ b;
  82
  83         return error && !(error & (error - 1));
  84 }
  85
  86 static void check_poison_mem(unsigned char *mem, size_t bytes)
  87 {
  88         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
  89         unsigned char *start;
  90         unsigned char *end;
  91
  92         start = memchr_inv(mem, PAGE_POISON, bytes);
  93         if (!start)
  94                 return;
  95
  96         for (end = mem + bytes - 1; end > start; end--) {
  97                 if (*end != PAGE_POISON)
  98                         break;
  99         }
 100
 101         if (!__ratelimit(&ratelimit))
 102                 return;
 103         else if (start == end && single_bit_flip(*start, PAGE_POISON))
 104                 printk(KERN_ERR "pagealloc: single bit error\n");
 105         else
 106                 printk(KERN_ERR "pagealloc: memory corruption\n");
 107
 108         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
 109                         end - start + 1, 1);
 110         dump_stack();
 111 }
 112
 113 static void unpoison_page(struct page *page)
 114 {
 115         void *addr;
 116
 117         if (!page_poison(page))
 118                 return;
 119
 120         addr = kmap_atomic(page);
 121         check_poison_mem(addr, PAGE_SIZE);
 122         clear_page_poison(page);
 123         kunmap_atomic(addr);
 124 }
 125
 126 static void unpoison_pages(struct page *page, int n)
 127 {
 128         int i;
 129
 130         for (i = 0; i < n; i++)
 131                 unpoison_page(page + i);
 132 }
 133
 134 void __kernel_map_pages(struct page *page, int numpages, int enable)
 135 {
 136         if (!page_poisoning_enabled)
 137                 return;
 138
 139         if (enable)
 140                 unpoison_pages(page, numpages);
 141         else
 142                 poison_pages(page, numpages);
 143 }