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SubjectRe: Kernel Cross Compiling
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Date
 Just to point out that we (OSDL) already do this.

http://www.osdl.org/projects/26lnxstblztn/results/


We are willing to add more but it is always willing
to look at adding more.

Tim

On Fri, 2004-02-13 at 12:57, Herbert Poetzl wrote:
> Hi Folks!
>
> I'm currently investigating the requirements/doability
> of a kernel cross compiling test bed/setup, able to do
> automated kernel builds for different architecture,
> just to see if it compiles and later to verify if a
> given patch breaks that compile on any of the tested
> archs ...
>
> here a short status, and some issues I ran into so far,
> some of them with solutions, others without, and some
> interesting? observations ...
>
> I would be happy if somebody who has done similar, or
> knows how to do it properly ;) could comment on that,
> and/or point out possible improvements ...
>
> TIA,
> Herbert
>
>
> 1) CROSS COMPILER / TOOLCHAIN
>
> after reading and testing several cross build and
> toolchain building howtos, I decided to do it a little
> different, because I do not need glibc to compile the
> kernel ...
>
> the result are two .spec files[1], or the commands
> used to build an appropriate toolchain ...
>
> for the binutils the required commands are:
>
> configure \
> --disable-nls \
> --prefix=/usr \
> --mandir=/usr/share/man \
> --infodir=/usr/share/info \
> --target=${CROSS_ARCH}-linux
> make
>
> and for the gcc (after the binutils have been
> installed on the host):
>
> configure \
> --enable-languages=c \
> --disable-nls \
> --disable-threads \
> --disable-shared \
> --disable-checking \
> --prefix=/usr \
> --mandir=/usr/share/man \
> --infodir=/usr/share/info \
> --target=${CROSS_ARCH}-linux
> make TARGET_LIBGCC2_CFLAGS='-Dinhibit_libc \
> -D__gthr_posix_h'
>
> where ${CROSS_ARCH} is the target architecture you want
> to compile the toochain for, in my case, this where one
> of the following:
>
> alpha, hppa, hppa64, i386, ia64, m68k, mips,
> mips64, ppc, ppc64, s390, sparc, sparc64, x86_64
>
> PROBLEMS HERE:
>
> I decided to use binutils 2.14.90.0.8, and gcc 3.3.2,
> but soon discovered that gcc-3.3.2 will not be able
> to build a cross compiler for some archs like the
> alpha, ia64, powerpc and even i386 ;) without some
> modifications[2] but with some help, I got all headers
> fixed, except for the ia64, which still doesn't work
>
>
> 2) KERNEL CROSS COMPILING
>
> equipped with the cross compiling toolchains for all
> but one of the architectures mentioned above, I wrote
> a little script, which basically does nothing else
> but compiling a given kernel for all possible archs.
>
> basically this can be accomplished by doing:
>
> make ARCH=<arch> CROSS_COMPILE=<arch>-linux-
>
>
> the first result was harrowing:
>
> 2.4.25-pre 2.6.2-rc
> ----------------------------------------------------
> [ARCH alpha/alpha] succeeded. succeeded.
> [ARCH hppa/parisc] failed. failed.
> [ARCH hppa64/parisc] failed. failed.
> [ARCH i386/i386] succeeded. succeeded.
> [ARCH m68k/m68k] failed. failed.
> [ARCH mips/mips] failed. failed.
> [ARCH mips64/mips] failed. failed.
> [ARCH ppc/ppc] succeeded. succeeded.
> [ARCH ppc64/ppc64] failed. failed.
> [ARCH s390/s390] failed. failed.
> [ARCH sparc/sparc] failed. succeeded.
> [ARCH sparc64/sparc] failed. failed.
> [ARCH x86_64/x86_64] failed. succeeded.
>
> so only alpha, i386 and ppc did work on the first run.
>
> what I discovered was, that there IS a big difference
> between an empty .config file and a non exististing
> one, where latter allowed the make oldconfig to work
> similar to the make defaultconfig available on 2.6,
> and added some archs (see [3] for details)
>
> PROBLEMS & SOLUTIONS HERE:
>
> ppc64:
> CROSS32_COMPILE=ppc-linux-
> is needed to make this work as expected.
>
> hppa/hppa64:
> seems not to compile without using a very big
> patch, which changes a lot inside the kernel
>
> mips/mips64:
> seem to use the 'obsoleted' -mcpu= option
> which results in a cc1: error: invalid option
> `cpu=<cpu-here>'
>
> m68k:
> fails with a hundred errors in the includes
>
>
> 3) CONCLUSIONS
>
> it seems that recent kernels (2.4 and 2.6) do not support
> most of the architectures they contain without heavy
> patching (haven't tested for arm, sh3/4, ...)
>
> building cross compiler toolchains isn't that often done
> otherwise it would not require such modifications, and
> the documentation would be up to date ...
>
> it seems that with some minor patches and kernel tweaks
> an automated build is in reach, although some archs seem
> to break from one release to the other ...
>
> the non mainline branches, if they exist are some kernel
> versions behind the current mainstream kernel, which
> might not mean anything ...
>
>
> 4) LINKS & REFERENCES
>
> [1] http://vserver.13thfloor.at/Stuff/Cross/binutils-cross.spec
> http://vserver.13thfloor.at/Stuff/Cross/gcc-cross.spec
>
> [2] http://vserver.13thfloor.at/Stuff/Cross/
> gcc-3.3.2-cross-alpha-fix.diff.bz2
> gcc-3.3.2-cross-i386-fix.diff.bz2
> gcc-3.3.2-cross-ia64-fix.diff.bz2
> gcc-3.3.2-cross-powerpc-fix.diff.bz2
>
> [3] http://vserver.13thfloor.at/Stuff/Cross/compile.info
>
> ia64: http://www.gelato.unsw.edu.au/kerncomp/
> mips: http://www.linux-mips.org/kernel.html
> hppa: http://www.parisc-linux.org/kernel/index.html
> ppc64: http://linuxppc64.org/
>
>
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--
Timothy D. Witham - Lab Director - wookie@osdl.org
Open Source Development Lab Inc - A non-profit corporation
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