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Linux/mm/page_poison.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_ext.h>
  6 #include <linux/poison.h>
  7 #include <linux/ratelimit.h>
  8 
  9 static bool __page_poisoning_enabled __read_mostly;
 10 static bool want_page_poisoning __read_mostly;
 11 
 12 static int early_page_poison_param(char *buf)
 13 {
 14         if (!buf)
 15                 return -EINVAL;
 16 
 17         if (strcmp(buf, "on") == 0)
 18                 want_page_poisoning = true;
 19         else if (strcmp(buf, "off") == 0)
 20                 want_page_poisoning = false;
 21 
 22         return 0;
 23 }
 24 early_param("page_poison", early_page_poison_param);
 25 
 26 bool page_poisoning_enabled(void)
 27 {
 28         return __page_poisoning_enabled;
 29 }
 30 
 31 static bool need_page_poisoning(void)
 32 {
 33         return want_page_poisoning;
 34 }
 35 
 36 static void init_page_poisoning(void)
 37 {
 38         /*
 39          * page poisoning is debug page alloc for some arches. If either
 40          * of those options are enabled, enable poisoning
 41          */
 42         if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) {
 43                 if (!want_page_poisoning && !debug_pagealloc_enabled())
 44                         return;
 45         } else {
 46                 if (!want_page_poisoning)
 47                         return;
 48         }
 49 
 50         __page_poisoning_enabled = true;
 51 }
 52 
 53 struct page_ext_operations page_poisoning_ops = {
 54         .need = need_page_poisoning,
 55         .init = init_page_poisoning,
 56 };
 57 
 58 static inline void set_page_poison(struct page *page)
 59 {
 60         struct page_ext *page_ext;
 61 
 62         page_ext = lookup_page_ext(page);
 63         __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 64 }
 65 
 66 static inline void clear_page_poison(struct page *page)
 67 {
 68         struct page_ext *page_ext;
 69 
 70         page_ext = lookup_page_ext(page);
 71         __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 72 }
 73 
 74 bool page_is_poisoned(struct page *page)
 75 {
 76         struct page_ext *page_ext;
 77 
 78         page_ext = lookup_page_ext(page);
 79         if (!page_ext)
 80                 return false;
 81 
 82         return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
 83 }
 84 
 85 static void poison_page(struct page *page)
 86 {
 87         void *addr = kmap_atomic(page);
 88 
 89         set_page_poison(page);
 90         memset(addr, PAGE_POISON, PAGE_SIZE);
 91         kunmap_atomic(addr);
 92 }
 93 
 94 static void poison_pages(struct page *page, int n)
 95 {
 96         int i;
 97 
 98         for (i = 0; i < n; i++)
 99                 poison_page(page + i);
100 }
101 
102 static bool single_bit_flip(unsigned char a, unsigned char b)
103 {
104         unsigned char error = a ^ b;
105 
106         return error && !(error & (error - 1));
107 }
108 
109 static void check_poison_mem(unsigned char *mem, size_t bytes)
110 {
111         static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
112         unsigned char *start;
113         unsigned char *end;
114 
115         if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
116                 return;
117 
118         start = memchr_inv(mem, PAGE_POISON, bytes);
119         if (!start)
120                 return;
121 
122         for (end = mem + bytes - 1; end > start; end--) {
123                 if (*end != PAGE_POISON)
124                         break;
125         }
126 
127         if (!__ratelimit(&ratelimit))
128                 return;
129         else if (start == end && single_bit_flip(*start, PAGE_POISON))
130                 pr_err("pagealloc: single bit error\n");
131         else
132                 pr_err("pagealloc: memory corruption\n");
133 
134         print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
135                         end - start + 1, 1);
136         dump_stack();
137 }
138 
139 static void unpoison_page(struct page *page)
140 {
141         void *addr;
142 
143         if (!page_is_poisoned(page))
144                 return;
145 
146         addr = kmap_atomic(page);
147         check_poison_mem(addr, PAGE_SIZE);
148         clear_page_poison(page);
149         kunmap_atomic(addr);
150 }
151 
152 static void unpoison_pages(struct page *page, int n)
153 {
154         int i;
155 
156         for (i = 0; i < n; i++)
157                 unpoison_page(page + i);
158 }
159 
160 void kernel_poison_pages(struct page *page, int numpages, int enable)
161 {
162         if (!page_poisoning_enabled())
163                 return;
164 
165         if (enable)
166                 unpoison_pages(page, numpages);
167         else
168                 poison_pages(page, numpages);
169 }
170 
171 #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
172 void __kernel_map_pages(struct page *page, int numpages, int enable)
173 {
174         /* This function does nothing, all work is done via poison pages */
175 }
176 #endif
177 

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