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/mmdebug.h>
6#include <linux/highmem.h>
7#include <linux/poison.h>
8#include <linux/ratelimit.h>
9#include <linux/kasan.h>
10
11bool _page_poisoning_enabled_early;
12EXPORT_SYMBOL(_page_poisoning_enabled_early);
13DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
14EXPORT_SYMBOL(_page_poisoning_enabled);
15
16static int __init early_page_poison_param(char *buf)
17{
18 return kstrtobool(s: buf, res: &_page_poisoning_enabled_early);
19}
20early_param("page_poison", early_page_poison_param);
21
22static void poison_page(struct page *page)
23{
24 void *addr = kmap_atomic(page);
25
26 /* KASAN still think the page is in-use, so skip it. */
27 kasan_disable_current();
28 memset(kasan_reset_tag(addr), PAGE_POISON, PAGE_SIZE);
29 kasan_enable_current();
30 kunmap_atomic(addr);
31}
32
33void __kernel_poison_pages(struct page *page, int n)
34{
35 int i;
36
37 for (i = 0; i < n; i++)
38 poison_page(page: page + i);
39}
40
41static bool single_bit_flip(unsigned char a, unsigned char b)
42{
43 unsigned char error = a ^ b;
44
45 return error && !(error & (error - 1));
46}
47
48static void check_poison_mem(struct page *page, unsigned char *mem, size_t bytes)
49{
50 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
51 unsigned char *start;
52 unsigned char *end;
53
54 start = memchr_inv(p: mem, PAGE_POISON, size: bytes);
55 if (!start)
56 return;
57
58 for (end = mem + bytes - 1; end > start; end--) {
59 if (*end != PAGE_POISON)
60 break;
61 }
62
63 if (!__ratelimit(&ratelimit))
64 return;
65 else if (start == end && single_bit_flip(a: *start, PAGE_POISON))
66 pr_err("pagealloc: single bit error\n");
67 else
68 pr_err("pagealloc: memory corruption\n");
69
70 print_hex_dump(KERN_ERR, prefix_str: "", prefix_type: DUMP_PREFIX_ADDRESS, rowsize: 16, groupsize: 1, buf: start,
71 len: end - start + 1, ascii: 1);
72 dump_stack();
73 dump_page(page, reason: "pagealloc: corrupted page details");
74}
75
76static void unpoison_page(struct page *page)
77{
78 void *addr;
79
80 addr = kmap_atomic(page);
81 kasan_disable_current();
82 /*
83 * Page poisoning when enabled poisons each and every page
84 * that is freed to buddy. Thus no extra check is done to
85 * see if a page was poisoned.
86 */
87 check_poison_mem(page, mem: kasan_reset_tag(addr), PAGE_SIZE);
88 kasan_enable_current();
89 kunmap_atomic(addr);
90}
91
92void __kernel_unpoison_pages(struct page *page, int n)
93{
94 int i;
95
96 for (i = 0; i < n; i++)
97 unpoison_page(page: page + i);
98}
99
100#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
101void __kernel_map_pages(struct page *page, int numpages, int enable)
102{
103 /* This function does nothing, all work is done via poison pages */
104}
105#endif
106

source code of linux/mm/page_poison.c