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    SubjectKernel Cross Compiling [update]

    Hi Folks!

    Here is an update to the Kernel Cross Compiling thread
    I started ten days ago ...

    1) CROSS COMPILER / TOOLCHAIN

    there are different solutions for the toolchain issue:

    - Dan Kegel's Crosstool [1]
    - PTXdist [2]
    - my simplified approach [3]

    in one mail [Ref-A], Jim Wilson mentioned that using the
    'inhibit_libc' trick will break the gcc in a subtly way,
    so I decided to verify the fitness of the compiled gcc.

    because 'normal' checks won't work without the glibc and
    the includes, I decided to take the following approach:

    - build gcc 3.3.2 with Dan's crosstool, and with my
    simplified approach.

    - select all tests from the test suite which contain
    tests relevant for the kernel (no floats, no (g)libc
    includes)

    - compile each C source into Assembler code (gcc -O2 -S)
    with both compilers (crosstool gcc version and mine)

    - compare the resulting Assembler code and check for
    differences

    the GCC testsuite contains 2854 files in the relevant
    subdirs consistency.vlad, gcc.c-torture, gcc.dg, and
    gcc.misc-tests.

    after removing the non relevant tests (file matching
    egrep '#include|float|double') 1799 C files remain.

    the result of the tests and comparison[4] shows that
    both compilers produce the same code, except for one
    little difference[5], which I'm unable to explain ...

    my conclusion so far is that my approach should be
    sufficient for Kernel Cross Compiling.


    2) KERNEL CROSS COMPILING

    linux-2.6.3-rc3 linux-2.6.3
    config build config build

    alpha/alpha: OK OK OK OK
    arm/arm: FAILED FAILED FAILED FAILED
    cris/cris: FAILED FAILED FAILED FAILED
    hppa/parisc: OK FAILED OK FAILED
    hppa64/parisc: OK FAILED OK FAILED
    i386/i386: OK OK OK OK
    ia64/ia64: OK OK OK OK
    m68k/m68k: OK FAILED OK FAILED
    mips/mips: OK FAILED OK FAILED
    mips64/mips: OK FAILED OK FAILED
    ppc/ppc: OK FAILED OK FAILED
    ppc64/ppc64: OK OK OK OK
    s390/s390: OK FAILED OK FAILED
    sh/sh: OK FAILED OK FAILED
    sh64/sh: OK FAILED OK FAILED
    sparc/sparc: OK FAILED OK FAILED
    sparc64/sparc64: OK OK OK OK
    v850/v850: FAILED FAILED FAILED FAILED
    x86_64/x86_64: OK OK OK OK


    interesting is that some architectures (arm, chris, v850)
    do not even have an appropriate default config, where
    others seem to require different? binutils (sh and sh64)
    but most other issues seem to be inconsistent configs or
    broken headers/code (details [6])...

    mips/mips64 seems to break because of an cpu= option
    which was depreciated in gcc some time ago, so they might
    build again if those changes are merged back into mainline

    hppa/hppa64 seems to require heavy patches to make them
    compile, which might be too intrusive to get into mainline
    very soon.

    linux-2.4.25
    config dep kernel modules

    alpha/alpha: OK OK OK OK
    arm/arm: OK OK FAILED FAILED
    cris/cris: OK FAILED FAILED FAILED
    hppa/parisc: OK OK FAILED FAILED
    hppa64/parisc: OK OK FAILED FAILED
    i386/i386: OK OK OK OK
    ia64/ia64: OK OK FAILED FAILED
    m68k/m68k: OK OK OK OK
    mips/mips: OK OK FAILED FAILED
    mips64/mips64: OK OK FAILED FAILED
    ppc/ppc: OK OK OK OK
    ppc64/ppc64: OK FAILED FAILED OK
    s390/s390: OK OK OK OK
    sh/sh: OK OK FAILED FAILED
    sh64/sh64: OK OK FAILED FAILED
    sparc/sparc: OK OK FAILED OK
    sparc64/sparc64: OK OK OK OK
    v850/v850: FAILED FAILED FAILED FAILED
    x86_64/x86_64: OK OK OK OK


    the logs[7] for the 2.4.25 kernel build suggest similar
    reasons for similar architectures (compared to 2.6.3)

    3) CONCLUSIONS

    it seems that the fast/easy way to build a cross gcc
    compiler (at least on x86 ;) is sufficient for kernel
    cross compile tests.

    6/7 out of 19 'supported' architectures are currently
    building with the kernel default configuration, when
    cross compiled in an x86 host (about a third).


    best,
    Herbert



    [1] http://kegel.com/crosstool
    [2] http://www.pengutronix.de/software/ptxdist_en.html
    [3] http://vserver.13thfloor.at/Stuff/Cross/howto.info
    [4] http://vserver.13thfloor.at/Stuff/Cross/Comparison
    [5] http://vserver.13thfloor.at/Stuff/Cross/Comparison/TEST-alpha.diff
    [6] http://vserver.13thfloor.at/Stuff/Cross/LOGS-2.6.3
    [7] http://vserver.13thfloor.at/Stuff/Cross/LOGS-2.4.25

    [Ref-A]

    On Mon, Feb 16, 2004 at 02:50:41PM -0800, Jim Wilson wrote:
    > I recommend Dan Kegel's page for anyone trying to build a cross compiler
    > to linux. See
    > http://kegel.com/crosstool
    > This isn't very hard to follow, and it gives you a properly configured
    > and built gcc/glibc for the target.
    >
    > I don't recommend the inhibit_libc trick for building linux crosses.
    > It may work well enough for kernel builds, but it will give you a subtly
    > broken gcc, and that may lead to confusion later.

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