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Linux/mm/debug-pagealloc.c

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  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 }
106 

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