tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
9static bool __page_poisoning_enabled __read_mostly;
10static bool want_page_poisoning __read_mostly;
11
12static int early_page_poison_param(char *buf)
13{
14 if (!buf)
15 return -EINVAL;
16 return strtobool(buf, &want_page_poisoning);
17}
18early_param("page_poison", early_page_poison_param);
19
20bool page_poisoning_enabled(void)
21{
22 return __page_poisoning_enabled;
23}
24
25static bool need_page_poisoning(void)
26{
27 return want_page_poisoning;
28}
29
30static void init_page_poisoning(void)
31{
32 /*
33 * page poisoning is debug page alloc for some arches. If either
34 * of those options are enabled, enable poisoning
35 */
36 if (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC)) {
37 if (!want_page_poisoning && !debug_pagealloc_enabled())
38 return;
39 } else {
40 if (!want_page_poisoning)
41 return;
42 }
43
44 __page_poisoning_enabled = true;
45}
46
47struct page_ext_operations page_poisoning_ops = {
48 .need = need_page_poisoning,
49 .init = init_page_poisoning,
50};
51
52static inline void set_page_poison(struct page *page)
53{
54 struct page_ext *page_ext;
55
56 page_ext = lookup_page_ext(page);
57 if (unlikely(!page_ext))
58 return;
59
60 __set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
61}
62
63static inline void clear_page_poison(struct page *page)
64{
65 struct page_ext *page_ext;
66
67 page_ext = lookup_page_ext(page);
68 if (unlikely(!page_ext))
69 return;
70
71 __clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
72}
73
74bool page_is_poisoned(struct page *page)
75{
76 struct page_ext *page_ext;
77
78 page_ext = lookup_page_ext(page);
79 if (unlikely(!page_ext))
80 return false;
81
82 return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
83}
84
85static 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
94static 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
102static 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
109static 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
139static 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
152static 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
160void 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
172void __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