| 1 | #include <linux/kernel.h>
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| 2 | #include <linux/mm.h>
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| 3 | #include <linux/page-debug-flags.h>
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| 4 | #include <linux/poison.h>
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| 5 |
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| 6 | static inline void set_page_poison(struct page *page)
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| 7 | {
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| 8 | __set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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| 9 | }
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| 10 |
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| 11 | static inline void clear_page_poison(struct page *page)
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| 12 | {
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| 13 | __clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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| 14 | }
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| 15 |
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| 16 | static inline bool page_poison(struct page *page)
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| 17 | {
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| 18 | return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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| 19 | }
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| 20 |
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| 21 | static void poison_highpage(struct page *page)
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| 22 | {
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| 23 | |
| 24 | * Page poisoning for highmem pages is not implemented.
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| 25 | *
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| 26 | * This can be called from interrupt contexts.
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| 27 | * So we need to create a new kmap_atomic slot for this
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| 28 | * application and it will need interrupt protection.
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| 29 |
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| 30 | }
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| 31 |
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| 32 | static void poison_page(struct page *page)
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| 33 | {
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| 34 | void *addr;
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| 35 |
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| 36 | if (PageHighMem(page)) {
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| 37 | poison_highpage(page);
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| 38 | return;
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| 39 | }
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| 40 | set_page_poison(page);
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| 41 | addr = page_address(page);
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| 42 | memset(addr, PAGE_POISON, PAGE_SIZE);
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| 43 | }
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| 44 |
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| 45 | static void poison_pages(struct page *page, int n)
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| 46 | {
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| 47 | int i;
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| 48 |
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| 49 | for (i = 0; i < n; i++)
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| 50 | poison_page(page + i);
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| 51 | }
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| 52 |
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| 53 | static bool single_bit_flip(unsigned char a, unsigned char b)
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| 54 | {
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| 55 | unsigned char error = a ^ b;
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| 56 |
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| 57 | return error && !(error & (error - 1));
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| 58 | }
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| 59 |
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| 60 | static void check_poison_mem(unsigned char *mem, size_t bytes)
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| 61 | {
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| 62 | unsigned char *start;
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| 63 | unsigned char *end;
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| 64 |
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| 65 | for (start = mem; start < mem + bytes; start++) {
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| 66 | if (*start != PAGE_POISON)
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| 67 | break;
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| 68 | }
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| 69 | if (start == mem + bytes)
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| 70 | return;
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| 71 |
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| 72 | for (end = mem + bytes - 1; end > start; end--) {
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| 73 | if (*end != PAGE_POISON)
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| 74 | break;
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| 75 | }
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| 76 |
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| 77 | if (!printk_ratelimit())
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| 78 | return;
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| 79 | else if (start == end && single_bit_flip(*start, PAGE_POISON))
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| 80 | printk(KERN_ERR "pagealloc: single bit error\n");
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| 81 | else
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| 82 | printk(KERN_ERR "pagealloc: memory corruption\n");
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| 83 |
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| 84 | print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
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| 85 | end - start + 1, 1);
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| 86 | dump_stack();
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| 87 | }
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| 88 |
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| 89 | static void unpoison_highpage(struct page *page)
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| 90 | {
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| 91 | |
| 92 | * See comment in poison_highpage().
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| 93 | * Highmem pages should not be poisoned for now
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| 94 |
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| 95 | BUG_ON(page_poison(page));
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| 96 | }
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| 97 |
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| 98 | static void unpoison_page(struct page *page)
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| 99 | {
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| 100 | if (PageHighMem(page)) {
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| 101 | unpoison_highpage(page);
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| 102 | return;
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| 103 | }
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| 104 | if (page_poison(page)) {
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| 105 | void *addr = page_address(page);
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| 106 |
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| 107 | check_poison_mem(addr, PAGE_SIZE);
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| 108 | clear_page_poison(page);
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| 109 | }
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| 110 | }
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| 111 |
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| 112 | static void unpoison_pages(struct page *page, int n)
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| 113 | {
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| 114 | int i;
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| 115 |
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| 116 | for (i = 0; i < n; i++)
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| 117 | unpoison_page(page + i);
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| 118 | }
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| 119 |
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| 120 | void kernel_map_pages(struct page *page, int numpages, int enable)
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| 121 | {
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| 122 | if (!debug_pagealloc_enabled)
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| 123 | return;
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| 124 |
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| 125 | if (enable)
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| 126 | unpoison_pages(page, numpages);
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| 127 | else
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| 128 | poison_pages(page, numpages);
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| 129 | }
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