I wanted to see if I could help on http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31490 - this prevents gcc building a modular kernel, a fix will be going in to the kernel to tell people not to waste their time trying to build modular with 4.2.0. Unfortunately, I've hit two showstoppers:
1. I can't chroot to the temporary system, it reports an Error, apparently in glibc. At the moment I haven't looked at this part beyond looking at strace.
2. Trying an LFS-style native build to establish what works, it can't build 64-bit glibc (2.5, 2.5 with our patches, 2.6 in any combination with binutils-2.17, 2.17 with our patches, and recent hjl) although 32-bit is ok. The error is
CPP='gcc -m64 -B/tools/bin/ -E -x c-header' /mnt/lfs/building/glibc-build/elf/ld64.so.1 --library-path /mnt/lfs/building/glibc-build:/mnt/lfs/building/glibc-build/math:/mnt/lfs/building/glibc-build/elf:/mnt/lfs/building/glibc-build/dlfcn:/mnt/lfs/building/glibc-build/nss:/mnt/lfs/building/glibc-build/nis:/mnt/lfs/building/glibc-build/rt:/mnt/lfs/building/glibc-build/resolv:/mnt/lfs/building/glibc-build/crypt:/mnt/lfs/building/glibc-build/nptl /mnt/lfs/building/glibc-build/sunrpc/rpcgen -Y ../scripts -c rpcsvc/bootparam_prot.x -o /mnt/lfs/building/glibc-build/sunrpc/xbootparam_prot.T
make[2]: *** [/mnt/lfs/building/glibc-build/sunrpc/xbootparam_prot.stmp] Segmentation fault
make[2]: Leaving directory `/mnt/lfs/building/glibc-2.5/sunrpc'
make[1]: *** [sunrpc/others] Error 2
make[1]: Leaving directory `/mnt/lfs/building/glibc-2.5'
make: *** [all] Error 2
At the moment I'm working through an LFS-style build with hjl binutils, gcc-4.1.2, and our patched glibc-2.5 to iron out the bugs in my script. After that I'll try a native toolchain build into /opt/newtools or wherever using hjl, 4.2.0, and glibc-2.6 (or 2.6.1 if it is out). At that point I can report the failure to build glibc. So, if anybody else is using ppc64, don't hold your breath!