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