From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751967AbYI3DJJ (ORCPT ); Mon, 29 Sep 2008 23:09:09 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753105AbYI3DHH (ORCPT ); Mon, 29 Sep 2008 23:07:07 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.125]:53645 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752219AbYI3DG5 (ORCPT ); Mon, 29 Sep 2008 23:06:57 -0400 Message-Id: <20080930030652.298596016@goodmis.org> References: <20080930030236.230994826@goodmis.org> User-Agent: quilt/0.46-1 Date: Mon, 29 Sep 2008 23:02:39 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Andrew Morton , Linus Torvalds , Mathieu Desnoyers , Steven Rostedt Subject: [PATCH 3/6] ring_buffer: add paranoid check for buffer page Content-Disposition: inline; filename=ring-buffer-paranoid-buffer-page-check.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If for some strange reason the buffer_page gets bigger, or the page struct gets smaller, I want to know this ASAP. The best way is to not let the kernel compile. This patch adds code to test the size of the struct buffer_page against the page struct and will cause compile issues if the buffer_page ever gets bigger than the page struct. Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 11 +++++++++++ 1 file changed, 11 insertions(+) Index: linux-tip.git/kernel/trace/ring_buffer.c =================================================================== --- linux-tip.git.orig/kernel/trace/ring_buffer.c 2008-09-29 17:31:05.000000000 -0400 +++ linux-tip.git/kernel/trace/ring_buffer.c 2008-09-29 19:59:24.000000000 -0400 @@ -289,6 +289,12 @@ static void rb_free_cpu_buffer(struct ri kfree(cpu_buffer); } +/* + * Causes compile errors if the struct buffer_page gets bigger + * than the struct page. + */ +extern int ring_buffer_page_too_big(void); + /** * ring_buffer_alloc - allocate a new ring_buffer * @size: the size in bytes that is needed. @@ -305,6 +311,11 @@ struct ring_buffer *ring_buffer_alloc(un int bsize; int cpu; + /* Paranoid! Optimizes out when all is well */ + if (sizeof(struct buffer_page) > sizeof(struct page)) + ring_buffer_page_too_big(); + + /* keep it in its own cache line */ buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), GFP_KERNEL); --