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
10 static bool want_page_poisoning __read_mostly;
11
12 static int __init early_page_poison_param(char *buf)
13 {
14 if (!buf)
15 return -EINVAL;
16 return strtobool(buf, &want_page_poisoning);
17 }
18 early_param("page_poison", early_page_poison_param);
19
20 bool 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
33 static 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
41 static 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
49 static 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
56 static 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
86 static 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
100 static 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
108 void 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
120 void __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
125
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.