6a11f75b6a
CONFIG_DEBUG_PAGEALLOC is now supported by x86, powerpc, sparc64, and s390. This patch implements it for the rest of the architectures by filling the pages with poison byte patterns after free_pages() and verifying the poison patterns before alloc_pages(). This generic one cannot detect invalid page accesses immediately but invalid read access may cause invalid dereference by poisoned memory and invalid write access can be detected after a long delay. Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com> Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
130 lines
2.5 KiB
C
130 lines
2.5 KiB
C
#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/page-debug-flags.h>
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#include <linux/poison.h>
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static inline void set_page_poison(struct page *page)
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{
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__set_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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}
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static inline void clear_page_poison(struct page *page)
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{
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__clear_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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}
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static inline bool page_poison(struct page *page)
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{
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return test_bit(PAGE_DEBUG_FLAG_POISON, &page->debug_flags);
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}
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static void poison_highpage(struct page *page)
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{
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/*
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* Page poisoning for highmem pages is not implemented.
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*
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* This can be called from interrupt contexts.
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* So we need to create a new kmap_atomic slot for this
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* application and it will need interrupt protection.
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*/
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}
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static void poison_page(struct page *page)
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{
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void *addr;
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if (PageHighMem(page)) {
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poison_highpage(page);
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return;
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}
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set_page_poison(page);
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addr = page_address(page);
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memset(addr, PAGE_POISON, PAGE_SIZE);
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}
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static void poison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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poison_page(page + i);
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}
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static bool single_bit_flip(unsigned char a, unsigned char b)
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{
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unsigned char error = a ^ b;
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return error && !(error & (error - 1));
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}
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static void check_poison_mem(unsigned char *mem, size_t bytes)
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{
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unsigned char *start;
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unsigned char *end;
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for (start = mem; start < mem + bytes; start++) {
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if (*start != PAGE_POISON)
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break;
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}
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if (start == mem + bytes)
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return;
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for (end = mem + bytes - 1; end > start; end--) {
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if (*end != PAGE_POISON)
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break;
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}
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if (!printk_ratelimit())
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return;
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else if (start == end && single_bit_flip(*start, PAGE_POISON))
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printk(KERN_ERR "pagealloc: single bit error\n");
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else
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printk(KERN_ERR "pagealloc: memory corruption\n");
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print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1, start,
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end - start + 1, 1);
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dump_stack();
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}
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static void unpoison_highpage(struct page *page)
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{
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/*
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* See comment in poison_highpage().
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* Highmem pages should not be poisoned for now
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*/
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BUG_ON(page_poison(page));
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}
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static void unpoison_page(struct page *page)
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{
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if (PageHighMem(page)) {
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unpoison_highpage(page);
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return;
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}
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if (page_poison(page)) {
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void *addr = page_address(page);
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check_poison_mem(addr, PAGE_SIZE);
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clear_page_poison(page);
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}
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}
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static void unpoison_pages(struct page *page, int n)
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{
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int i;
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for (i = 0; i < n; i++)
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unpoison_page(page + i);
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}
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void kernel_map_pages(struct page *page, int numpages, int enable)
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{
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if (!debug_pagealloc_enabled)
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return;
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if (enable)
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unpoison_pages(page, numpages);
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else
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poison_pages(page, numpages);
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}
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