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(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_local_page(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_local(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(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(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	dump_page(page, "pagealloc: corrupted page details");
74}
75
76static void unpoison_page(struct page *page)
77{
78	void *addr;
79
80	addr = kmap_local_page(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, kasan_reset_tag(addr), PAGE_SIZE);
88	kasan_enable_current();
89	kunmap_local(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 + 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