[Buildroot] Illegal instruction by python's xmlrpclib on powerpc64, gcc-4.9

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Dear Alvaro Gamez,

Adding in Cc: some PowerPC folks: Gustavo Zacarias who added the 6500
config option, and Cody who added the initial PowerPC64 support.
Gustavo, Cody, can you look below ?

Alvaro, read only below for some suggestions.

Thanks!

Thomas

On Tue, 3 Nov 2015 10:40:09 +0100, Alvaro Gamez wrote:

> I'm trying to use xmlrpclib module from python on this architecture,
> but whenever I import that module I'm answered back with an 'Illegal
> instruction':
> 
> Python 2.7.10 (default, Oct 29 2015, 11:03:21)
> [GCC 4.9.3] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
> >>> import xmlrpclib
> Illegal instruction
> 
> And this appears on dmesg:
> python[1439]: unhandled signal 4 at 00003fffb19ec6dc nip 00003fffb19ec6dc
> lr 00003fffb19ec6b0 code 30001
> 
> This doesn't happen when importing other modules, such as sys or os, but I
> haven't tested any other module besides these.
> 
> # cat /proc/cpuinfo
> processor    : 0
> cpu        : e6500, altivec supported
> clock        : 1466.666652MHz
> revision    : 2.0 (pvr 8040 0120)
> [ 7 identical cores more removed from this to avoid clutter ]
> timebase    : 37500000
> platform    : VPX3-133
> model        : cw,vpx3-133
> 
> Attached buildroot's config:
> 
> BR2_powerpc64=y
> BR2_powerpc_e6500=y
> BR2_DL_DIR="$(BR2_EXTERNAL)/dl"
> BR2_PACKAGE_OVERRIDE_FILE="$(BR2_EXTERNAL)/local.mk"
> BR2_GLOBAL_PATCH_DIR="$(BR2_EXTERNAL)/patch"
> BR2_KERNEL_HEADERS_3_10=y
> BR2_TOOLCHAIN_BUILDROOT_CXX=y
> BR2_GCC_ENABLE_LTO=y
> BR2_GCC_ENABLE_OPENMP=y
> BR2_ENABLE_LOCALE_PURGE=y
> BR2_ENABLE_LOCALE_WHITELIST="C"
> BR2_ROOTFS_DEVICE_CREATION_DYNAMIC_EUDEV=y
> BR2_TARGET_GENERIC_GETTY_PORT="tty1"
> BR2_ROOTFS_USERS_TABLES="$(BR2_EXTERNAL)/users.table"
> BR2_LINUX_KERNEL=y
> BR2_LINUX_KERNEL_CUSTOM_GIT=y
> BR2_LINUX_KERNEL_CUSTOM_REPO_URL="ssh://.../linux.git"
> BR2_LINUX_KERNEL_CUSTOM_REPO_VERSION="tag"
> BR2_LINUX_KERNEL_USE_CUSTOM_CONFIG=y
> BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE="$(BR2_EXTERNAL)/$(PROJECT_NAME)tag_defconfig"
> BR2_LINUX_KERNEL_DTS_SUPPORT=y
> BR2_LINUX_KERNEL_USE_CUSTOM_DTS=y
> BR2_LINUX_KERNEL_CUSTOM_DTS_PATH="$(BR2_EXTERNAL)/$(PROJECT_NAME)/tag.dts"
> BR2_PACKAGE_PYTHON=y
> [ And the rest is just a selection of packages and non compiler nor kernel
> related things ]
> 
> 
> This only happens when using buildroot's toolchain.
> One difference between buildroot's toolchain and the others,
> is that buildroot's is the only one that supports a 64 bit target.
> 
> I don't know who can I debug that to provide more information,
> but I'm willing to test whatever is needed.

Can you rebuild with BR2_ENABLE_DEBUG=y, then run "ulimit -c unlimited"
on your target, run the crashing Python stuff, grab back the "core"
file on your host machine, and 1 /look at the backtrace and 2/ at the
specific instruction that caused the crash ?

This would probably help quite a bit I believe.

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com