debug-pagealloc.c
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#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/page-debug-flags.h>
#include <linux/poison.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_highpage(struct page *page)
{
/*
* Page poisoning for highmem pages is not implemented.
*
* This can be called from interrupt contexts.
* So we need to create a new kmap_atomic slot for this
* application and it will need interrupt protection.
*/
}
static void poison_page(struct page *page)
{
void *addr;
if (PageHighMem(page)) {
poison_highpage(page);
return;
}
set_page_poison(page);
addr = page_address(page);
memset(addr, PAGE_POISON, PAGE_SIZE);
}
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)
{
unsigned char *start;
unsigned char *end;
for (start = mem; start < mem + bytes; start++) {
if (*start != PAGE_POISON)
break;
}
if (start == mem + bytes)
return;
for (end = mem + bytes - 1; end > start; end--) {
if (*end != PAGE_POISON)
break;
}
if (!printk_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_highpage(struct page *page)
{
/*
* See comment in poison_highpage().
* Highmem pages should not be poisoned for now
*/
BUG_ON(page_poison(page));
}
static void unpoison_page(struct page *page)
{
if (PageHighMem(page)) {
unpoison_highpage(page);
return;
}
if (page_poison(page)) {
void *addr = page_address(page);
check_poison_mem(addr, PAGE_SIZE);
clear_page_poison(page);
}
}
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);
}