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#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>
#ifndef mark_addr_rdonly
#define mark_addr_rdonly(a)
#endif
#ifndef mark_addr_rdwrite
#define mark_addr_rdwrite(a)
#endif
static bool page_poisoning_enabled __read_mostly;
static bool need_page_poisoning(void)
{
if (!debug_pagealloc_enabled())
return false;
return true;
}
static void init_page_poisoning(void)
{
if (!debug_pagealloc_enabled())
return;
page_poisoning_enabled = true;
}
struct page_ext_operations page_poisoning_ops = {
.need = need_page_poisoning,
.init = init_page_poisoning,
};
static inline void set_page_poison(struct page *page)
{
struct page_ext *page_ext;
page_ext = lookup_page_ext(page);
__set_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}
static inline void clear_page_poison(struct page *page)
{
struct page_ext *page_ext;
page_ext = lookup_page_ext(page);
__clear_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}
static inline bool page_poison(struct page *page)
{
struct page_ext *page_ext;
page_ext = lookup_page_ext(page);
return test_bit(PAGE_EXT_DEBUG_POISON, &page_ext->flags);
}
static void poison_page(struct page *page)
{
void *addr = kmap_atomic(page);
set_page_poison(page);
memset(addr, PAGE_POISON, PAGE_SIZE);
mark_addr_rdonly(addr);
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(struct page *page,
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 on page with phys start 0x%lx\n",
(unsigned long)page_to_phys(page));
else
pr_err("pagealloc: memory corruption on page with phys start 0x%lx\n",
(unsigned long)page_to_phys(page));
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))
return;
addr = kmap_atomic(page);
check_poison_mem(page, addr, PAGE_SIZE);
mark_addr_rdwrite(addr);
clear_page_poison(page);
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_map_pages(struct page *page, int numpages, int enable)
{
if (!page_poisoning_enabled)
return;
if (enable)
unpoison_pages(page, numpages);
else
poison_pages(page, numpages);
}
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