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#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/page-debug-flags.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>
static inline void set_page_poison(struct page *page)
	__set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
static inline void clear_page_poison(struct page *page)
	__clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
static inline bool page_poison(struct page *page)
	return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
static void poison_page(struct page *page)
	void *addr = kmap_atomic(page);
	set_page_poison(page);
	memset(addr, PAGE_POISON, PAGE_SIZE);
	kunmap_atomic(addr);
static void poison_pages(struct page *page, int n)
	for (i = 0; i < n; i++)
		poison_page(page + i);
static bool single_bit_flip(unsigned char a, unsigned char b)
	unsigned char error = a ^ b;
	return error && !(error & (error - 1));
static void check_poison_mem(unsigned char *mem, size_t bytes)
	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
	unsigned char *start;
	unsigned char *end;
	start = memchr_inv(mem, PAGE_POISON, bytes);
	if (!start)
	for (end = mem + bytes - 1; end > start; end--) {
		if (*end != PAGE_POISON)
	if (!__ratelimit(&ratelimit))
	else if (start == end && single_bit_flip(*start, PAGE_POISON))
		printk(KERN_ERR "pagealloc: single bit error\n");
		printk(KERN_ERR "pagealloc: memory corruption\n");
	print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
			end - start + 1, 1);
	dump_stack();
static void unpoison_page(struct page *page)
	void *addr;
	if (!page_poison(page))
	addr = kmap_atomic(page);
	check_poison_mem(addr, PAGE_SIZE);
	clear_page_poison(page);
	kunmap_atomic(addr);
static void unpoison_pages(struct page *page, int n)
	for (i = 0; i < n; i++)
		unpoison_page(page + i);
void kernel_map_pages(struct page *page, int numpages, int enable)
	if (enable)
		unpoison_pages(page, numpages);
		poison_pages(page, numpages);

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debug-pagealloc.c

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