[mirror_ubuntu-artful-kernel.git] / mm / page_poison.c

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/page_ext.h>
#include <linux/poison.h>
#include <linux/ratelimit.h>

static bool want_page_poisoning __read_mostly;

static int early_page_poison_param(char *buf)
{
	if (!buf)
		return -EINVAL;
	return strtobool(buf, &want_page_poisoning);
}
early_param("page_poison", early_page_poison_param);

bool page_poisoning_enabled(void)
{
	/*
	 * Assumes that debug_pagealloc_enabled is set before
	 * free_all_bootmem.
	 * Page poisoning is debug page alloc for some arches. If
	 * either of those options are enabled, enable poisoning.
	 */
	return (want_page_poisoning ||
		(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
		debug_pagealloc_enabled()));
}

static void poison_page(struct page *page)
{
	void *addr = kmap_atomic(page);

	memset(addr, PAGE_POISON, PAGE_SIZE);
	kunmap_atomic(addr);
}

static void poison_pages(struct page *page, int n)
{
	int i;

	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;

	if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
		return;

	start = memchr_inv(mem, PAGE_POISON, bytes);
	if (!start)
		return;

	for (end = mem + bytes - 1; end > start; end--) {
		if (*end != PAGE_POISON)
			break;
	}

	if (!__ratelimit(&ratelimit))
		return;
	else if (start == end && single_bit_flip(*start, PAGE_POISON))
		pr_err("pagealloc: single bit error\n");
	else
		pr_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;

	addr = kmap_atomic(page);
	/*
	 * Page poisoning when enabled poisons each and every page
	 * that is freed to buddy. Thus no extra check is done to
	 * see if a page was posioned.
	 */
	check_poison_mem(addr, PAGE_SIZE);
	kunmap_atomic(addr);
}

static void unpoison_pages(struct page *page, int n)
{
	int i;

	for (i = 0; i < n; i++)
		unpoison_page(page + i);
}

void kernel_poison_pages(struct page *page, int numpages, int enable)
{
	if (!page_poisoning_enabled())
		return;

	if (enable)
		unpoison_pages(page, numpages);
	else
		poison_pages(page, numpages);
}

#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
void __kernel_map_pages(struct page *page, int numpages, int enable)
{
	/* This function does nothing, all work is done via poison pages */
}
#endif
Commit	Line	Data
	1	#include <linux/kernel.h>
	2	#include <linux/string.h>
	3	#include <linux/mm.h>
	4	#include <linux/highmem.h>
	5	#include <linux/page_ext.h>
	6	#include <linux/poison.h>
	7	#include <linux/ratelimit.h>
	8
	9	static bool want_page_poisoning __read_mostly;
	10
	11	static int early_page_poison_param(char *buf)
	12	{
	13	if (!buf)
	14	return -EINVAL;
	15	return strtobool(buf, &want_page_poisoning);
	16	}
	17	early_param("page_poison", early_page_poison_param);
	18
	19	bool page_poisoning_enabled(void)
	20	{
	21	/*
	22	* Assumes that debug_pagealloc_enabled is set before
	23	* free_all_bootmem.
	24	* Page poisoning is debug page alloc for some arches. If
	25	* either of those options are enabled, enable poisoning.
	26	*/
	27	return (want_page_poisoning \|\|
	28	(!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) &&
	29	debug_pagealloc_enabled()));
	30	}
	31
	32	static void poison_page(struct page *page)
	33	{
	34	void *addr = kmap_atomic(page);
	35
	36	memset(addr, PAGE_POISON, PAGE_SIZE);
	37	kunmap_atomic(addr);
	38	}
	39
	40	static void poison_pages(struct page *page, int n)
	41	{
	42	int i;
	43
	44	for (i = 0; i < n; i++)
	45	poison_page(page + i);
	46	}
	47
	48	static bool single_bit_flip(unsigned char a, unsigned char b)
	49	{
	50	unsigned char error = a ^ b;
	51
	52	return error && !(error & (error - 1));
	53	}
	54
	55	static void check_poison_mem(unsigned char *mem, size_t bytes)
	56	{
	57	static DEFINE_RATELIMIT_STATE(ratelimit, 5 * HZ, 10);
	58	unsigned char *start;
	59	unsigned char *end;
	60
	61	if (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY))
	62	return;
	63
	64	start = memchr_inv(mem, PAGE_POISON, bytes);
	65	if (!start)
	66	return;
	67
	68	for (end = mem + bytes - 1; end > start; end--) {
	69	if (*end != PAGE_POISON)
	70	break;
	71	}
	72
	73	if (!__ratelimit(&ratelimit))
	74	return;
	75	else if (start == end && single_bit_flip(*start, PAGE_POISON))
	76	pr_err("pagealloc: single bit error\n");
	77	else
	78	pr_err("pagealloc: memory corruption\n");
	79
	80	print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
	81	end - start + 1, 1);
	82	dump_stack();
	83	}
	84
	85	static void unpoison_page(struct page *page)
	86	{
	87	void *addr;
	88
	89	addr = kmap_atomic(page);
	90	/*
	91	* Page poisoning when enabled poisons each and every page
	92	* that is freed to buddy. Thus no extra check is done to
	93	* see if a page was posioned.
	94	*/
	95	check_poison_mem(addr, PAGE_SIZE);
	96	kunmap_atomic(addr);
	97	}
	98
	99	static void unpoison_pages(struct page *page, int n)
	100	{
	101	int i;
	102
	103	for (i = 0; i < n; i++)
	104	unpoison_page(page + i);
	105	}
	106
	107	void kernel_poison_pages(struct page *page, int numpages, int enable)
	108	{
	109	if (!page_poisoning_enabled())
	110	return;
	111
	112	if (enable)
	113	unpoison_pages(page, numpages);
	114	else
	115	poison_pages(page, numpages);
	116	}
	117
	118	#ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC
	119	void __kernel_map_pages(struct page *page, int numpages, int enable)
	120	{
	121	/* This function does nothing, all work is done via poison pages */
	122	}
	123	#endif