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// SPDX-License-Identifier: GPL-2.0
#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>
#include <linux/kasan.h>
bool _page_poisoning_enabled_early;
EXPORT_SYMBOL(_page_poisoning_enabled_early);
DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled);
EXPORT_SYMBOL(_page_poisoning_enabled);
static int __init early_page_poison_param(char *buf)
{
return kstrtobool(buf, &_page_poisoning_enabled_early);
}
early_param("page_poison", early_page_poison_param);
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
/* KASAN still think the page is in-use, so skip it. */
kasan_disable_current();
memset(addr, PAGE_POISON, PAGE_SIZE);
kasan_enable_current();
kunmap_atomic(addr);
}
void __kernel_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;
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 poisoned.
*/
check_poison_mem(addr, PAGE_SIZE);
kunmap_atomic(addr);
}
void __kernel_unpoison_pages(struct page *page, int n)
{
int i;
for (i = 0; i < n; i++)
unpoison_page(page + i);
}
#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
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