1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/kernel.h>
3 #include <linux/string.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>
11 static bool want_page_poisoning __read_mostly;
13 static int __init early_page_poison_param(char *buf)
17 return strtobool(buf, &want_page_poisoning);
19 early_param("page_poison", early_page_poison_param);
21 bool page_poisoning_enabled(void)
24 * Assumes that debug_pagealloc_enabled is set before
26 * Page poisoning is debug page alloc for some arches. If
27 * either of those options are enabled, enable poisoning.
29 return (want_page_poisoning ||
30 (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
31 debug_pagealloc_enabled()));
34 static void poison_page(struct page *page)
36 void *addr = kmap_atomic(page);
38 /* KASAN still think the page is in-use, so skip it. */
39 kasan_disable_current();
40 memset(addr, PAGE_POISON, PAGE_SIZE);
41 kasan_enable_current();
45 static void poison_pages(struct page *page, int n)
49 for (i = 0; i < n; i++)
50 poison_page(page + i);
53 static bool single_bit_flip(unsigned char a, unsigned char b)
55 unsigned char error = a ^ b;
57 return error && !(error & (error - 1));
60 static void check_poison_mem(unsigned char *mem, size_t bytes)
62 static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
66 if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
69 start = memchr_inv(mem, PAGE_POISON, bytes);
73 for (end = mem + bytes - 1; end > start; end--) {
74 if (*end != PAGE_POISON)
78 if (!__ratelimit(&ratelimit))
80 else if (start == end && single_bit_flip(*start, PAGE_POISON))
81 pr_err("pagealloc: single bit error\n");
83 pr_err("pagealloc: memory corruption\n");
85 print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
90 static void unpoison_page(struct page *page)
94 addr = kmap_atomic(page);
96 * Page poisoning when enabled poisons each and every page
97 * that is freed to buddy. Thus no extra check is done to
98 * see if a page was posioned.
100 check_poison_mem(addr, PAGE_SIZE);
104 static void unpoison_pages(struct page *page, int n)
108 for (i = 0; i < n; i++)
109 unpoison_page(page + i);
112 void kernel_poison_pages(struct page *page, int numpages, int enable)
114 if (!page_poisoning_enabled())
118 unpoison_pages(page, numpages);
120 poison_pages(page, numpages);
123 #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
124 void __kernel_map_pages(struct page *page, int numpages, int enable)
126 /* This function does nothing, all work is done via poison pages */