From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752858Ab1IPKiZ (ORCPT ); Fri, 16 Sep 2011 06:38:25 -0400 Received: from out3.smtp.messagingengine.com ([66.111.4.27]:39387 "EHLO out3.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751756Ab1IPKiY (ORCPT ); Fri, 16 Sep 2011 06:38:24 -0400 X-Sasl-enc: 14PhKp0dZGtpSdH0h8zrdRwvrrcspbw+jMP+pcDLEj2M 1316169502 Subject: Re: [PATCH] Force same size of struct autofs_v5_packet on x86 and x86_64 From: Ian Kent To: Thomas Meyer Cc: Al Viro , Linux Kernel Mailing List , dhowells@redhat.com In-Reply-To: <20110916101903.GI2203@ZenIV.linux.org.uk> References: <1316167604.6545.84.camel@localhost.localdomain> <20110916101903.GI2203@ZenIV.linux.org.uk> Content-Type: text/plain; charset="UTF-8" Date: Fri, 16 Sep 2011 18:38:16 +0800 Message-ID: <1316169496.8502.6.camel@perseus.themaw.net> Mime-Version: 1.0 X-Mailer: Evolution 2.32.3 (2.32.3-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2011-09-16 at 11:19 +0100, Al Viro wrote: > On Fri, Sep 16, 2011 at 12:06:38PM +0200, Thomas Meyer wrote: > > autofs_v5_packet is 300 bytes on x86 and 304 bytes on x86_64. > > This difference is wrong and leads to a hang in systemd when running > > a x86 userspace on an x86_64 kernel. > > NAK. > > You are talking about the userland ABI. With existing users. Changing > it might help systemd (what the hell is it doing with autofs, anyway?), > but breaking existing binaries (you know, ones that *do* have some business > dealing with autofs) is not acceptable. That's right. Certainly my mistake (made a long time ago) and when I realized it I decided I would need to handle it in user space for the same reasons Al has mentioned. I think this should be enough (but any further recommendations are welcome, apart from the fact we might get new archs): static size_t get_kpkt_len(void) { size_t pkt_len = sizeof(struct autofs_v5_packet); struct utsname un; uname(&un); if (pkt_len % 8) { if (strcmp(un.machine, "alpha") == 0 || strcmp(un.machine, "ia64") == 0 || strcmp(un.machine, "x86_64") == 0 || strcmp(un.machine, "ppc64") == 0) pkt_len += 4; } return pkt_len; }