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1// SPDX-License-Identifier: GPL-2.0
2#include <linux/kernel.h>
3#include <linux/string.h>
4#include <linux/mm.h>
5#include <linux/highmem.h>
6#include <linux/page_ext.h>
7#include <linux/poison.h>
8#include <linux/ratelimit.h>
9
10static bool want_page_poisoning __read_mostly;
11
12static int __init 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 /*
23 * Assumes that debug_pagealloc_enabled is set before
24 * free_all_bootmem.
25 * Page poisoning is debug page alloc for some arches. If
26 * either of those options are enabled, enable poisoning.
27 */
28 return (want_page_poisoning ||
29 (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
30 debug_pagealloc_enabled()));
31}
32
33static void poison_page(struct page *page)
34{
35 void *addr = kmap_atomic(page);
36
37 memset(addr, PAGE_POISON, PAGE_SIZE);
38 kunmap_atomic(addr);
39}
40
41static void poison_pages(struct page *page, int n)
42{
43 int i;
44
45 for (i = 0; i < n; i++)
46 poison_page(page + i);
47}
48
49static bool single_bit_flip(unsigned char a, unsigned char b)
50{
51 unsigned char error = a ^ b;
52
53 return error && !(error & (error - 1));
54}
55
56static void check_poison_mem(unsigned char *mem, size_t bytes)
57{
58 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
59 unsigned char *start;
60 unsigned char *end;
61
62 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
63 return;
64
65 start = memchr_inv(mem, PAGE_POISON, bytes);
66 if (!start)
67 return;
68
69 for (end = mem + bytes - 1; end > start; end--) {
70 if (*end != PAGE_POISON)
71 break;
72 }
73
74 if (!__ratelimit(&ratelimit))
75 return;
76 else if (start == end && single_bit_flip(*start, PAGE_POISON))
77 pr_err("pagealloc: single bit error\n");
78 else
79 pr_err("pagealloc: memory corruption\n");
80
81 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
82 end - start + 1, 1);
83 dump_stack();
84}
85
86static void unpoison_page(struct page *page)
87{
88 void *addr;
89
90 addr = kmap_atomic(page);
91 /*
92 * Page poisoning when enabled poisons each and every page
93 * that is freed to buddy. Thus no extra check is done to
94 * see if a page was posioned.
95 */
96 check_poison_mem(addr, PAGE_SIZE);
97 kunmap_atomic(addr);
98}
99
100static void unpoison_pages(struct page *page, int n)
101{
102 int i;
103
104 for (i = 0; i < n; i++)
105 unpoison_page(page + i);
106}
107
108void kernel_poison_pages(struct page *page, int numpages, int enable)
109{
110 if (!page_poisoning_enabled())
111 return;
112
113 if (enable)
114 unpoison_pages(page, numpages);
115 else
116 poison_pages(page, numpages);
117}
118
119#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
120void __kernel_map_pages(struct page *page, int numpages, int enable)
121{
122 /* This function does nothing, all work is done via poison pages */
123}
124#endif
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
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}
24early_param("page_poison", early_page_poison_param);
25
26bool page_poisoning_enabled(void)
27{
28 return __page_poisoning_enabled;
29}
30
31static bool need_page_poisoning(void)
32{
33 return want_page_poisoning;
34}
35
36static 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
53struct page_ext_operations page_poisoning_ops = {
54 .need = need_page_poisoning,
55 .init = init_page_poisoning,
56};
57
58static 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
66static 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
74bool 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
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