Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758529Ab2FOXM1 (ORCPT ); Fri, 15 Jun 2012 19:12:27 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:51801 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758479Ab2FOXMY (ORCPT ); Fri, 15 Jun 2012 19:12:24 -0400 Date: Fri, 15 Jun 2012 16:12:20 -0700 From: Greg Kroah-Hartman To: Geert Uytterhoeven Cc: =?iso-8859-1?Q?Bj=F8rn?= Mork , USB list , linux-kernel@vger.kernel.org, Linux-Next , linux-kbuild , Linux/m68k Subject: Re: [-next] FATAL: drivers/gpu/drm/udl/udl: sizeof(struct usb_device_id)=24 is not a modulo of the size of section __mod_usb_device_table=44. Message-ID: <20120615231220.GC8205@kroah.com> References: <20120615201021.GB14544@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3443 Lines: 91 On Fri, Jun 15, 2012 at 11:02:55PM +0200, Geert Uytterhoeven wrote: > Hi Greg, > > On Fri, Jun 15, 2012 at 10:10 PM, Greg Kroah-Hartman > wrote: > > On Fri, Jun 15, 2012 at 07:42:08PM +0200, Geert Uytterhoeven wrote: > >> commit 81df2d594340dcb6d1a02191976be88a1ca8120c ("USB: allow match > >> on bInterfaceNumber") added a byte to the interior of struct usb_device_id, > >> enabling implicit padding: > >> > >> --- a/include/linux/mod_devicetable.h > >> +++ b/include/linux/mod_devicetable.h > >> @@ -115,6 +118,9 @@ struct usb_device_id { > >> ? ? ? ? __u8 ? ? ? ? ? ?bInterfaceSubClass; > >> ? ? ? ? __u8 ? ? ? ? ? ?bInterfaceProtocol; > >> > >> + ? ? ? /* Used for vendor-specific interface matches */ > >> + ? ? ? __u8 ? ? ? ? ? ?bInterfaceNumber; > >> + > >> ? ? ? ? /* not matched against */ > >> ? ? ? ? kernel_ulong_t ?driver_info; > >> ?}; > >> > >> On m68k, this causes failures like: > >> > >> | FATAL: drivers/gpu/drm/udl/udl: sizeof(struct usb_device_id)=24 is > >> not a modulo of the size of section __mod_usb_device_table=44. > >> | Fix definition of struct usb_device_id in mod_devicetable.h > >> > >> M68k is special in that it uses 2 for the alignment of 32-bit entities, hence > >> sizeof(struct usb_device_id) = 22. > >> > >> However, when cross-compiling on amd64, sizeof(struct usb_device_id) = 24 > >> in scripts/mod/file2alias.c. > > > > I don't really understand, what is the problem here? ?The fact that we > > added one byte to the structure? ?And now something breaks? ?How? > > > > What can we do to resolve it? > > As "kernel_ulong_t ?driver_info" is no longer naturally aligned, the > compiler will > add implicit padding. But the padding depends on the architecture. Ah, so we were "lucky" before, nice. > It can be fixed by adding explicit padding. Probably it should be padded by > 7 bytes (not 3), as kernel_ulong_t may require 8-byte alignment on some 64-bit > platforms. Or by an explicit alignment attribute. > > See also > * commit 8175fe2dda1c93a9c596921c8ed4a0b4baccdefe ("HID: fix > hid_device_id for cross compiling") > * commit 7492d4a416d68ab4bd254b36ffcc4e0138daa8ff ("sdio: fix module > device table definition for m68k") > * commit 9e2d3cd34a159948dc753a14573e16bffc04dba8 ("[PATCH] > mod_devicetable.h fixes") So would the patch below fix this? It should force alignment of the driver_data field, which is all you want here, right? > Still, there's a bug in file2alias (which is compiled by the host > compiler), in that > it may use different padding than the target platform when cross-compiling. That's not good, but outside of this specific issue, right? Have we just been fortunate it hasn't really hit us yet? thanks, greg k-h diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h index 7771d45..6955045 100644 --- a/include/linux/mod_devicetable.h +++ b/include/linux/mod_devicetable.h @@ -122,7 +122,8 @@ struct usb_device_id { __u8 bInterfaceNumber; /* not matched against */ - kernel_ulong_t driver_info; + kernel_ulong_t driver_info + __attribute__((aligned(sizeof(kernel_ulong_t)))); }; /* Some useful macros to use to create struct usb_device_id */ -- 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/