building powerpc64 kernel with crosstool (was: Re: crosstool powerpc-970)

[Dan Kegel <dank at kegel dot com>]

Raffael Himmelreich wrote:
> Hi there,
>
> I was trying to build a powerpc-970 kernel with crosstool
> 0.28-rc37 while I got the same error messages as in
> <http://kegel.com/crosstool/crosstool-0.28-rc37/buildlogs/0.28/powerpc-970-gcc-3.4.2-glibc-2.3.3.log.txt>.

namely:
gcc -Wp,-MD,arch/ppc64/boot/.crt0.o.d -D__ASSEMBLY__ -Wall -Wstrict-prototypes -O2 -fomit-frame-pointer -Iinclude -fno-builtin  -traditional -c -o arch/ppc64/boot/crt0.o arch/ppc64/boot/crt0.S
arch/ppc64/boot/crt0.S: Assembler messages:
arch/ppc64/boot/crt0.S:17: Error: no such instruction: `lis 9,_start@h'
arch/ppc64/boot/crt0.S:18: Error: no such instruction: `lis 8,_etext@ha'
...
make[1]: *** [arch/ppc64/boot/crt0.o] Error 1
make: *** [zImage] Error 2


> After looking what got wrong I had the following insights:
>  - the error messages are triggered when trying to build
>    with the wrong assembler (host instead of boot)

Right

>  - linux-2.6.8/arch/ppc64/boot/Makefile has to be
>    edited to compile with gcc -m32 (these kernel parts need
>    32bit code) and with 32bit binutils. I tried to build
>    biarch binutils but failed (ld complained that powerpc32 is
>    not the default output type), so I compiled 32bit binutils
>    and wrote the paths in that Makefile. (But, propably you will
>    be able to build/use biarch binutils.)

An alternate fix, and one that is easier than getting biarch
going, is described at
http://www.ussg.iu.edu/hypermail/linux/kernel/0409.2/1758.html
i.e. build a 32 bit toolchain with crosstool first, then when
compiling the kernel with the 64 bit toolchain, set the Make
variable CROSS32_COMPILE on the commandline, e.g. (for 2.6)
  make ARCH=$ARCH  CROSS_COMPILE=$PREFIX/bin/$TARGET-  CROSS32_COMPILE=$PREFIX32/bin/$TARGET32-
where ARCH is ppc64,
$PREFIX and $PREFIX32 are where you installed the 64 and 32 bit toolchains,
$TARGET is the machine tuple of the 32 bit toolchain (powerpc-750-linux-gnu),
$TARGET64 is the machine tuple of the 64 bit toolchain (powerpc-970-linux-gnu)

I've been meaning to use this workaround in my testlinux.sh script
that comes with crosstool, but haven't had a chance.

Hope that helps,
Dan

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