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
   9static inline void set_page_poison(struct page *page)
  10{
  11        __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  12}
  13
  14static inline void clear_page_poison(struct page *page)
  15{
  16        __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  17}
  18
  19static inline bool page_poison(struct page *page)
  20{
  21        return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
  22}
  23
  24static 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
  33static 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
  41static 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
  48static 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
  75static 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
  88static 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
  96void kernel_map_pages(struct page *page, int numpages, int enable)
  97{
  98        if (enable)
  99                unpoison_pages(page, numpages);
 100        else
 101                poison_pages(page, numpages);
 102}
 103
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