From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: ipc64_perm - generic Date: Mon, 25 May 2009 22:21:43 +0000 Message-ID: <200905252221.44082.arnd@arndb.de> References: <4A1AE972.9010905@monstr.eu> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from moutng.kundenserver.de ([212.227.126.188]:53548 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751715AbZEYWVz (ORCPT ); Mon, 25 May 2009 18:21:55 -0400 In-Reply-To: <4A1AE972.9010905@monstr.eu> Content-Disposition: inline Sender: linux-arch-owner@vger.kernel.org List-ID: To: monstr@monstr.eu, linux-arch@vger.kernel.org Cc: John Williams , linux-kernel@vger.kernel.org, Arnd Bergmann On Monday 25 May 2009 18:54:42 Michal Simek wrote: > > Hi Arnd, cc: John > > From asm-generic/posix_types.h > > 17 #ifndef __kernel_mode_t > 18 typedef unsigned int __kernel_mode_t; > 19 #endif > > This structure is not aligned properly because of pad2. > > 19 struct ipc64_perm { > 20 __kernel_key_t key; > 21 __kernel_uid32_t uid; > 22 __kernel_gid32_t gid; > 23 __kernel_uid32_t cuid; > 24 __kernel_gid32_t cgid; > 25 __kernel_mode_t mode; > 26 unsigned short __pad1; > 27 unsigned short seq; > 28 unsigned short __pad2; > 29 unsigned long __unused1; > 30 unsigned long __unused2; > 31 }; > > I think we should remove __pad1. > What do you think? Right, well spotted. I'd like to keep the struct ipc64_perm compatible with most architectures, so maybe we can play a little trick here: > Here is proposed struct. > struct ipc64_perm { > __kernel_key_t key; > __kernel_uid32_t uid; > __kernel_gid32_t gid; > __kernel_uid32_t cuid; > __kernel_gid32_t cgid; > __kernel_mode_t mode; + unsigned char __pad1[4 - sizeof(__kernel_mode_t)]; > unsigned short seq; > unsigned short __pad2; > unsigned long __unused1; > unsigned long __unused2; > }; If that's too much of a hack, we could also change the default __kernel_mode_t in asm-generic/posix_types.h to unsigned short, which it is on all 32-bit architectures except mips and xtensa. For some reason, all 64 bit architechtures use unsigned int for mode_t, but I couldn't find out why. Glibc uses unsigned int externally. Arnd <><