Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757246Ab0BLQsd (ORCPT ); Fri, 12 Feb 2010 11:48:33 -0500 Received: from cantor2.suse.de ([195.135.220.15]:56729 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756930Ab0BLQsb (ORCPT ); Fri, 12 Feb 2010 11:48:31 -0500 Message-ID: <4B75865B.8000307@suse.com> Date: Fri, 12 Feb 2010 11:48:27 -0500 From: Jeff Mahoney Organization: SUSE Labs, Novell, Inc User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.7) Gecko/20100111 SUSE/3.0.1-1.1 Thunderbird/3.0.1 MIME-Version: 1.0 To: Linux Kernel Mailing List Cc: Andrew Morton Subject: [PATCH] delayacct: align to 8 byte boundary on 64-bit systems Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2370 Lines: 65 prepare_reply sets up an skb for the response. If I understand it correctly, the payload contains: +--------------------------------+ | genlmsghdr - 4 bytes | +--------------------------------+ | NLA header - 4 bytes | /* Aggregate header */ +-+------------------------------+ | | NLA header - 4 bytes | /* PID header */ | +------------------------------+ | | pid/tgid - 4 bytes | | +------------------------------+ | | NLA header - 4 bytes | /* stats header */ | + -----------------------------+ <- oops. aligned on 4 byte boundary | | struct taskstats - 328 bytes | +-+------------------------------+ The start of the taskstats struct must be 8 byte aligned on IA64 (and other systems with 8 byte alignment rules for 64-bit types) or runtime alignment warnings will be issued. This patch pads the pid/tgid field out to sizeof(long), which forces the alignment of taskstats. The getdelays userspace code is ok with this since it assumes 32-bit pid/tgid and then honors that header's length field. An array is used to avoid exposing kernel memory contents to userspace in the response. Signed-off-by: Jeff Mahoney --- kernel/taskstats.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/kernel/taskstats.c +++ b/kernel/taskstats.c @@ -362,6 +362,12 @@ static struct taskstats *mk_reply(struct struct nlattr *na, *ret; int aggr; + /* If we don't pad, we end up with alignment on a 4 byte boundary. + * This causes lots of runtime warnings on systems requiring 8 byte + * alignment */ + u32 pids[2] = { pid, 0 }; + int pid_size = ALIGN(sizeof(pid), sizeof(long)); + aggr = (type == TASKSTATS_TYPE_PID) ? TASKSTATS_TYPE_AGGR_PID : TASKSTATS_TYPE_AGGR_TGID; @@ -369,7 +375,7 @@ static struct taskstats *mk_reply(struct na = nla_nest_start(skb, aggr); if (!na) goto err; - if (nla_put(skb, type, sizeof(pid), &pid) < 0) + if (nla_put(skb, type, pid_size, pids) < 0) goto err; ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats)); if (!ret) -- Jeff Mahoney SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/