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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
    12725 SW Millikan Way - Suite 400 - Beaverton OR, 97005
    (503)-626-2455 x11 (office) (503)-702-2871 (cell)
    (503)-626-2436 (fax)

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