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 want_page_poisoning __read_mostly;
10
11static int early_page_poison_param(char *buf)
12{
13 if (!buf)
14 return -EINVAL;
15 return strtobool(buf, &want_page_poisoning);
16}
17early_param("page_poison", early_page_poison_param);
18
19bool page_poisoning_enabled(void)
20{
21 /*
22 * Assumes that debug_pagealloc_enabled is set before
23 * free_all_bootmem.
24 * Page poisoning is debug page alloc for some arches. If
25 * either of those options are enabled, enable poisoning.
26 */
27 return (want_page_poisoning ||
28 (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
29 debug_pagealloc_enabled()));
30}
31
32static void poison_page(struct page *page)
33{
34 void *addr = kmap_atomic(page);
35
36 memset(addr, PAGE_POISON, PAGE_SIZE);
37 kunmap_atomic(addr);
38}
39
40static void poison_pages(struct page *page, int n)
41{
42 int i;
43
44 for (i = 0; i < n; i++)
45 poison_page(page + i);
46}
47
48static bool single_bit_flip(unsigned char a, unsigned char b)
49{
50 unsigned char error = a ^ b;
51
52 return error && !(error & (error - 1));
53}
54
55static void check_poison_mem(unsigned char *mem, size_t bytes)
56{
57 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
58 unsigned char *start;
59 unsigned char *end;
60
61 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
62 return;
63
64 start = memchr_inv(mem, PAGE_POISON, bytes);
65 if (!start)
66 return;
67
68 for (end = mem + bytes - 1; end > start; end--) {
69 if (*end != PAGE_POISON)
70 break;
71 }
72
73 if (!__ratelimit(&ratelimit))
74 return;
75 else if (start == end && single_bit_flip(*start, PAGE_POISON))
76 pr_err("pagealloc: single bit error\n");
77 else
78 pr_err("pagealloc: memory corruption\n");
79
80 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
81 end - start + 1, 1);
82 dump_stack();
83}
84
85static void unpoison_page(struct page *page)
86{
87 void *addr;
88
89 addr = kmap_atomic(page);
90 /*
91 * Page poisoning when enabled poisons each and every page
92 * that is freed to buddy. Thus no extra check is done to
93 * see if a page was posioned.
94 */
95 check_poison_mem(addr, PAGE_SIZE);
96 kunmap_atomic(addr);
97}
98
99static void unpoison_pages(struct page *page, int n)
100{
101 int i;
102
103 for (i = 0; i < n; i++)
104 unpoison_page(page + i);
105}
106
107void kernel_poison_pages(struct page *page, int numpages, int enable)
108{
109 if (!page_poisoning_enabled())
110 return;
111
112 if (enable)
113 unpoison_pages(page, numpages);
114 else
115 poison_pages(page, numpages);
116}
117
118#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
119void __kernel_map_pages(struct page *page, int numpages, int enable)
120{
121 /* This function does nothing, all work is done via poison pages */
122}
123#endif