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Octocat-spinner-32-eaf2f5

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file 106 lines (84 sloc) 2.144 kb
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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)
{
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))
printk(KERN_ERR "pagealloc: single bit error\n");
else
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))
return;

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)
{
int i;

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

void kernel_map_pages(struct page *page, int numpages, int enable)
{
if (!debug_pagealloc_enabled)
return;

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