#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); }