linux-kernel - Re: crossbuild fails in modpost

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Message-ID: <20080518213133.GA13821@uranus.ravnborg.org>
Date:	Sun, 18 May 2008 23:31:33 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Jiri Slaby <jirislaby@...il.com>
Cc:	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Michael Buesch <mb@...sch.de>,
	Gordon Farquharson <gordonfarquharson@...il.com>
Subject: Re: crossbuild fails in modpost

On Thu, May 15, 2008 at 09:19:26PM +0200, Jiri Slaby wrote:
> Sam Ravnborg napsal(a):
> >On Thu, May 15, 2008 at 07:35:39PM +0200, Sam Ravnborg wrote:
> >>On Thu, May 15, 2008 at 07:12:34PM +0200, Jiri Slaby wrote:
> >>>Well, let's fix sam's email.
> >>>
> >>>Jiri Slaby napsal(a):
> >>>>Hi,
> >>>>
> >>>>probably
> >>>>4ce6efed48d736e3384c39ff87bda723e1f8e041
> >>>>kbuild: soften modpost checks when doing cross builds
> >>>>
> >>>>causes build failures on x86_64 kernel build on 32 bit machine:
> >>>>
> >>>>make -f /local/xslaby/hid/scripts/Makefile.modpost
> >>>>YYYYYYYYYYYYYY x86_64 x86_64
> >>>> scripts/mod/modpost -m -a -o /local/xslaby/buhid/Module.symvers    -S 
> >>>>-K /local/xslaby/buhid/Module.markers -M 
> >>>>/local/xslaby/buhid/Module.markers   -s
> >>>>XXXXXXXXXXXXXXXXXX 20: 0 (2), 4 (4), 8 (4), 12 (8)
> >>>>FATAL: drivers/hid/hid-apple: sizeof(struct hid_device_id)=20 is not a 
> >>>>modulo of the size of section __mod_hid_device_table=648.
> >>>>Fix definition of struct hid_device_id in mod_devicetable.h
> >>>>make[2]: *** [__modpost] Error 1
> >>>>make[1]: *** [modules] Error 2
> >>>>make: *** [sub-make] Error 2
> >>>>
> >>>>after sticking echo into:
> >>>>__modpost: $(modules:.ko=.o) FORCE
> >>>>+       @echo YYYYYYYYYYYYYY $(KBUILD_BUILDHOST) $(ARCH)
> >>>>       $(call cmd,modpost) $(wildcard vmlinux) $(filter-out FORCE,$^)
> >>>>
> >>Your machine claims it is a x86_64 and you are building for a x86_64
> >>according to the following line:
> >>>>YYYYYYYYYYYYYY x86_64 x86_64
> >>So it looks to me that you are building for 64 bit on a 64 bit machine.
> >>So when you write:
> >> on x86_64 kernel build on 32 bit machine:
> >>
> >>I assume you try to say that your HOSTCC is 32 bit and your
> >>kernel cc is 64 bit (or something similar).
> >>
> >>The commit you reference loosen up the check so we do not do the
> >>check if we _know_ that the host and the target system differs.
> >>The only thing I can imagine right now to solve your issue would
> >>be to skip the check if we do not use the same gcc for target and host?
> 
> Well, the compiler is the same, but it's told to compile the kernel with 
> -m64. It runs on x86_64 kernel and i386 userspace. It's debian i386 gcc 
> package which understands x86_64 objects too. No SUBARCH option, it seems 
> to default to x86_64.

In that cae modpost tells you to fix your typedefiniton so the
size used in the kernel matches what the userspace can see.
So what we have here is exactly the kind of issues this
check were introduced to catch.

Add a bit more alignment to  hid_device_id and userspace and
kernel should be happy.

	Sam
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