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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 | #include <linux/kernel.h> #include <linux/string.h> #include <linux/mm.h> #include <linux/highmem.h> #include <linux/page_ext.h> #include <linux/poison.h> #include <linux/ratelimit.h> static bool page_poisoning_enabled __read_mostly; static bool need_page_poisoning(void) { if (!debug_pagealloc_enabled()) return false; return true; } static void init_page_poisoning(void) { if (!debug_pagealloc_enabled()) return; page_poisoning_enabled = true; } struct page_ext_operations page_poisoning_ops = { .need = need_page_poisoning, .init = init_page_poisoning, }; static inline void set_page_poison(struct page *page) { struct page_ext *page_ext; page_ext = lookup_page_ext(page); if (!page_ext) return; __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } static inline void clear_page_poison(struct page *page) { struct page_ext *page_ext; page_ext = lookup_page_ext(page); if (!page_ext) return; __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } static inline bool page_poison(struct page *page) { struct page_ext *page_ext; page_ext = lookup_page_ext(page); if (!page_ext) return false; return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } static void poison_page(struct page *page) { void *addr = kmap_atomic(page); set_page_poison(page); memset(addr, PAGE_POISON, PAGE_SIZE); kunmap_atomic(addr); } static void poison_pages(struct page *page, int n) { int i; for (i = 0; i < n; i++) poison_page(page + i); } static bool single_bit_flip(unsigned char a, unsigned char b) { unsigned char error = a ^ b; return error && !(error & (error - 1)); } static void check_poison_mem(unsigned char *mem, size_t bytes) { static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10); unsigned char *start; unsigned char *end; start = memchr_inv(mem, PAGE_POISON, bytes); if (!start) return; for (end = mem + bytes - 1; end > start; end--) { if (*end != PAGE_POISON) break; } if (!__ratelimit(&ratelimit)) return; else if (start == end && single_bit_flip(*start, PAGE_POISON)) printk(KERN_ERR "pagealloc: single bit error\n"); else printk(KERN_ERR "pagealloc: memory corruption\n"); print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start, end - start + 1, 1); dump_stack(); } static void unpoison_page(struct page *page) { void *addr; if (!page_poison(page)) return; addr = kmap_atomic(page); check_poison_mem(addr, PAGE_SIZE); clear_page_poison(page); kunmap_atomic(addr); } static void unpoison_pages(struct page *page, int n) { int i; for (i = 0; i < n; i++) unpoison_page(page + i); } void __kernel_map_pages(struct page *page, int numpages, int enable) { if (!page_poisoning_enabled) return; if (enable) unpoison_pages(page, numpages); else poison_pages(page, numpages); } |