Re: crossbuild fails in modpost

[Jiri Slaby]

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.

> So something like this (entirely untested):
>
> --- a/scripts/Makefile.modpost
> +++ b/scripts/Makefile.modpost
> @@ -65,7 +65,7 @@ modules   := $(patsubst %.o,%.ko, $(wildcard $(__modules:.ko=.o)))
>  # Stop after building .o files if NOFINAL is set. Makes compile tests quicker
>  _modpost: $(if $(KBUILD_MODPOST_NOFINAL), $(modules:.ko:.o),$(modules))
>  
> -ifneq ($(KBUILD_BUILDHOST),$(ARCH))
> +ifneq ($(CC),$(HOSTCC))

gcc gcc :)

>          cross_build := 1
>  endif
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