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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 | #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 want_page_poisoning __read_mostly; static int early_page_poison_param(char *buf) { if (!buf) return -EINVAL; return strtobool(buf, &want_page_poisoning); } early_param("page_poison", early_page_poison_param); bool page_poisoning_enabled(void) { return __page_poisoning_enabled; } static bool need_page_poisoning(void) { return want_page_poisoning; } static void init_page_poisoning(void) { /* * page poisoning is debug page alloc for some arches. If either * of those options are enabled, enable poisoning */ if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) { if (!want_page_poisoning && !debug_pagealloc_enabled()) return; } else { if (!want_page_poisoning) 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 (unlikely(!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 (unlikely(!page_ext)) return; __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags); } bool page_is_poisoned(struct page *page) { struct page_ext *page_ext; page_ext = lookup_page_ext(page); if (unlikely(!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; if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY)) return; 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)) pr_err("pagealloc: single bit error\n"); else pr_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_is_poisoned(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_poison_pages(struct page *page, int numpages, int enable) { if (!page_poisoning_enabled()) return; if (enable) unpoison_pages(page, numpages); else poison_pages(page, numpages); } #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC void __kernel_map_pages(struct page *page, int numpages, int enable) { /* This function does nothing, all work is done via poison pages */ } #endif |