mm/page_poison.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 static bool want_page_poisoning __read_mostly =
  11         !IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC);
  12
  13 static int early_page_poison_param(char *buf)
  14 {
  15         if (!buf)
  16                 return -EINVAL;
  17
  18         if (strcmp(buf, "on") == 0)
  19                 want_page_poisoning = true;
  20         else if (strcmp(buf, "off") == 0)
  21                 want_page_poisoning = false;
  22
  23         return 0;
  24 }
  25 early_param("page_poison", early_page_poison_param);
  26
  27 bool page_poisoning_enabled(void)
  28 {
  29         return __page_poisoning_enabled;
  30 }
  31
  32 static bool need_page_poisoning(void)
  33 {
  34         return want_page_poisoning;
  35 }
  36
  37 static void init_page_poisoning(void)
  38 {
  39         if (!want_page_poisoning)
  40                 return;
  41
  42         __page_poisoning_enabled = true;
  43 }
  44
  45 struct page_ext_operations page_poisoning_ops = {
  46         .need = need_page_poisoning,
  47         .init = init_page_poisoning,
  48 };
  49
  50 static inline void set_page_poison(struct page *page)
  51 {
  52         struct page_ext *page_ext;
  53
  54         page_ext = lookup_page_ext(page);
  55         __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  56 }
  57
  58 static inline void clear_page_poison(struct page *page)
  59 {
  60         struct page_ext *page_ext;
  61
  62         page_ext = lookup_page_ext(page);
  63         __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  64 }
  65
  66 static inline bool page_poison(struct page *page)
  67 {
  68         struct page_ext *page_ext;
  69
  70         page_ext = lookup_page_ext(page);
  71         return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  72 }
  73
  74 static void poison_page(struct page *page)
  75 {
  76         void *addr = kmap_atomic(page);
  77
  78         set_page_poison(page);
  79         memset(addr, PAGE_POISON, PAGE_SIZE);
  80         kunmap_atomic(addr);
  81 }
  82
  83 void poison_pages(struct page *page, int n)
  84 {
  85         int i;
  86
  87         for (i = 0; i < n; i++)
  88                 poison_page(page + i);
  89 }
  90
  91 static bool single_bit_flip(unsigned char a, unsigned char b)
  92 {
  93         unsigned char error = a ^ b;
  94
  95         return error && !(error & (error - 1));
  96 }
  97
  98 static void check_poison_mem(unsigned char *mem, size_t bytes)
  99 {
 100         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
 101         unsigned char *start;
 102         unsigned char *end;
 103
 104         if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
 105                 return;
 106
 107         start = memchr_inv(mem, PAGE_POISON, bytes);
 108         if (!start)
 109                 return;
 110
 111         for (end = mem + bytes - 1; end > start; end--) {
 112                 if (*end != PAGE_POISON)
 113                         break;
 114         }
 115
 116         if (!__ratelimit(&ratelimit))
 117                 return;
 118         else if (start == end && single_bit_flip(*start, PAGE_POISON))
 119                 printk(KERN_ERR "pagealloc: single bit error\n");
 120         else
 121                 printk(KERN_ERR "pagealloc: memory corruption\n");
 122
 123         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
 124                         end - start + 1, 1);
 125         dump_stack();
 126 }
 127
 128 static void unpoison_page(struct page *page)
 129 {
 130         void *addr;
 131
 132         if (!page_poison(page))
 133                 return;
 134
 135         addr = kmap_atomic(page);
 136         check_poison_mem(addr, PAGE_SIZE);
 137         clear_page_poison(page);
 138         kunmap_atomic(addr);
 139 }
 140
 141 void unpoison_pages(struct page *page, int n)
 142 {
 143         int i;
 144
 145         for (i = 0; i < n; i++)
 146                 unpoison_page(page + i);
 147 }
 148
 149 void kernel_poison_pages(struct page *page, int numpages, int enable)
 150 {
 151         if (!page_poisoning_enabled())
 152                 return;
 153
 154         if (enable)
 155                 unpoison_pages(page, numpages);
 156         else
 157                 poison_pages(page, numpages);
 158 }