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authorAkinobu Mita <akinobu.mita@gmail.com>2009-03-31 15:23:17 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-04-01 08:59:13 -0700
commit6a11f75b6a17b5d9ac5025f8d048382fd1f47377 (patch)
treea3415cd897823975b927f89a233d2703bf97ba2b /mm/debug-pagealloc.c
parent610a77e04a8d9fe8764dc484e2182fa251ce1cc2 (diff)
downloadvexpress-lsk-6a11f75b6a17b5d9ac5025f8d048382fd1f47377.tar.gz
generic debug pagealloc
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>
Diffstat (limited to 'mm/debug-pagealloc.c')
-rw-r--r--mm/debug-pagealloc.c129
1 files changed, 129 insertions, 0 deletions
diff --git a/mm/debug-pagealloc.c b/mm/debug-pagealloc.c
new file mode 100644
index 00000000000..a1e3324de2b
--- /dev/null
+++ b/mm/debug-pagealloc.c
@@ -0,0 +1,129 @@
+#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);
+}