1#include <linux/kernel.h>
  2#include <linux/string.h>
  3#include <linux/mm.h>
  4#include <linux/highmem.h>
  5#include <linux/page-debug-flags.h>
  6#include <linux/poison.h>
  7#include <linux/ratelimit.h>
  8
  9static inline void set_page_poison(struct page *page)
 10{
 11	__set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
 12}
 13
 14static inline void clear_page_poison(struct page *page)
 15{
 16	__clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
 17}
 18
 19static inline bool page_poison(struct page *page)
 20{
 21	return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
 22}
 23
 24static void poison_page(struct page *page)
 25{
 26	void *addr = kmap_atomic(page);
 27
 28	set_page_poison(page);
 29	memset(addr, PAGE_POISON, PAGE_SIZE);
 30	kunmap_atomic(addr);
 31}
 32
 33static void 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		printk(KERN_ERR "pagealloc: single bit error\n");
 67	else
 68		printk(KERN_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	if (!page_poison(page))
 80		return;
 81
 82	addr = kmap_atomic(page);
 83	check_poison_mem(addr, PAGE_SIZE);
 84	clear_page_poison(page);
 85	kunmap_atomic(addr);
 86}
 87
 88static void unpoison_pages(struct page *page, int n)
 89{
 90	int i;
 91
 92	for (i = 0; i < n; i++)
 93		unpoison_page(page + i);
 94}
 95
 96void kernel_map_pages(struct page *page, int numpages, int enable)
 97{
 98	if (enable)
 99		unpoison_pages(page, numpages);
100	else
101		poison_pages(page, numpages);
102}