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
  12 static int early_page_poison_param(char *buf)
  13 {
  14         if (!buf)
  15                 return -EINVAL;
  16         return strtobool(buf, &want_page_poisoning);
  17 }
  18 early_param("page_poison", early_page_poison_param);
  19
  20 bool page_poisoning_enabled(void)
  21 {
  22         return __page_poisoning_enabled;
  23 }
  24
  25 static bool need_page_poisoning(void)
  26 {
  27         return want_page_poisoning;
  28 }
  29
  30 static void init_page_poisoning(void)
  31 {
  32         /*
  33          * page poisoning is debug page alloc for some arches. If either
  34          * of those options are enabled, enable poisoning
  35          */
  36         if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) {
  37                 if (!want_page_poisoning && !debug_pagealloc_enabled())
  38                         return;
  39         } else {
  40                 if (!want_page_poisoning)
  41                         return;
  42         }
  43
  44         __page_poisoning_enabled = true;
  45 }
  46
  47 struct page_ext_operations page_poisoning_ops = {
  48         .need = need_page_poisoning,
  49         .init = init_page_poisoning,
  50 };
  51
  52 static inline void set_page_poison(struct page *page)
  53 {
  54         struct page_ext *page_ext;
  55
  56         page_ext = lookup_page_ext(page);
  57         __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  58 }
  59
  60 static inline void clear_page_poison(struct page *page)
  61 {
  62         struct page_ext *page_ext;
  63
  64         page_ext = lookup_page_ext(page);
  65         __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  66 }
  67
  68 bool page_is_poisoned(struct page *page)
  69 {
  70         struct page_ext *page_ext;
  71
  72         page_ext = lookup_page_ext(page);
  73         if (!page_ext)
  74                 return false;
  75
  76         return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
  77 }
  78
  79 static void poison_page(struct page *page)
  80 {
  81         void *addr = kmap_atomic(page);
  82
  83         set_page_poison(page);
  84         memset(addr, PAGE_POISON, PAGE_SIZE);
  85         kunmap_atomic(addr);
  86 }
  87
  88 static void poison_pages(struct page *page, int n)
  89 {
  90         int i;
  91
  92         for (i = 0; i < n; i++)
  93                 poison_page(page + i);
  94 }
  95
  96 static bool single_bit_flip(unsigned char a, unsigned char b)
  97 {
  98         unsigned char error = a ^ b;
  99
 100         return error && !(error & (error - 1));
 101 }
 102
 103 static void check_poison_mem(unsigned char *mem, size_t bytes)
 104 {
 105         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
 106         unsigned char *start;
 107         unsigned char *end;
 108
 109         if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
 110                 return;
 111
 112         start = memchr_inv(mem, PAGE_POISON, bytes);
 113         if (!start)
 114                 return;
 115
 116         for (end = mem + bytes - 1; end > start; end--) {
 117                 if (*end != PAGE_POISON)
 118                         break;
 119         }
 120
 121         if (!__ratelimit(&ratelimit))
 122                 return;
 123         else if (start == end && single_bit_flip(*start, PAGE_POISON))
 124                 pr_err("pagealloc: single bit error\n");
 125         else
 126                 pr_err("pagealloc: memory corruption\n");
 127
 128         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
 129                         end - start + 1, 1);
 130         dump_stack();
 131 }
 132
 133 static void unpoison_page(struct page *page)
 134 {
 135         void *addr;
 136
 137         if (!page_is_poisoned(page))
 138                 return;
 139
 140         addr = kmap_atomic(page);
 141         check_poison_mem(addr, PAGE_SIZE);
 142         clear_page_poison(page);
 143         kunmap_atomic(addr);
 144 }
 145
 146 static void unpoison_pages(struct page *page, int n)
 147 {
 148         int i;
 149
 150         for (i = 0; i < n; i++)
 151                 unpoison_page(page + i);
 152 }
 153
 154 void kernel_poison_pages(struct page *page, int numpages, int enable)
 155 {
 156         if (!page_poisoning_enabled())
 157                 return;
 158
 159         if (enable)
 160                 unpoison_pages(page, numpages);
 161         else
 162                 poison_pages(page, numpages);
 163 }
 164
 165 #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
 166 void __kernel_map_pages(struct page *page, int numpages, int enable)
 167 {
 168         /* This function does nothing, all work is done via poison pages */
 169 }
 170 #endif