tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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#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(buf, &_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 + 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(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(mem, PAGE_POISON, 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(*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, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
71 end - start + 1, 1);
72 dump_stack();
73}
74
75static void unpoison_page(struct page *page)
76{
77 void *addr;
78
79 addr = kmap_atomic(page);
80 kasan_disable_current();
81 /*
82 * Page poisoning when enabled poisons each and every page
83 * that is freed to buddy. Thus no extra check is done to
84 * see if a page was poisoned.
85 */
86 check_poison_mem(kasan_reset_tag(addr), PAGE_SIZE);
87 kasan_enable_current();
88 kunmap_atomic(addr);
89}
90
91void __kernel_unpoison_pages(struct page *page, int n)
92{
93 int i;
94
95 for (i = 0; i < n; i++)
96 unpoison_page(page + i);
97}
98
99#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
100void __kernel_map_pages(struct page *page, int numpages, int enable)
101{
102 /* This function does nothing, all work is done via poison pages */
103}
104#endif