[yocto] Cross-compiling python fails with new custom tuning

[Michael Habibi]

All,

I added a new machine definition with tuning parameters for haswell
microarchitectures (basically just duplicated corei7 but tuned it for
haswell). This seems to work correctly, but failed when running do_install
for python toward the end of the build process. I am running with the Yocto
2.0 framework, with very minimal changes to create a new distribution and
machine for our custom embedded device. Note I had this distro
configuration working before, and the only difference is I added a new
machine with this tuning.

I believe the issue is because, as part of the do_install step for Python,
it attempts to run python on the local host, despite being cross-compiled.
However, it is tuned for a processor that my host machine doesn't run, so I
get an instruction exception.

Did I do something weird? I figure python would be configured for
cross-compiling and therefore wouldn't try to run the target version on the
host, even for sanity tests. Here is the output of the failure:

$ tail -20
/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/temp/log.do_install.17258

x86_64-diags-linux-ar rc libpython2.7.a Modules/threadmodule.o
 Modules/signalmodule.o  Modules/posixmodule.o  Modules/errnomodule.o
 Modules/pwdmodule.o  Modules/_sre.o  Modules/_codecsmodule.o
 Modules/_weakref.o  Modules/zipimport.o  Modules/symtablemodule.o
 Modules/md5module.o Modules/md5.o  Modules/xxsubtype.o
x86_64-diags-linux-ranlib libpython2.7.a
Modules/posixmodule.o: In function `posix_tmpnam':
/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/Python-2.7.9/Modules/posixmodule.c:7575:
warning: the use of `tmpnam_r' is dangerous, better use `mkstemp'
Modules/posixmodule.o: In function `posix_tempnam':
/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/Python-2.7.9/Modules/posixmodule.c:7522:
warning: the use of `tempnam' is dangerous, better use `mkstemp'
x86_64-diags-linux-gcc  -m64 -march=haswell -mtune=haswell -mfpmath=sse
-mavx2 --sysroot=/projects/yocto-git/build/tmp/sysroots/continental -Wl,-O1
-Wl,--hash-style=gnu -Wl,--as-needed -Xlinker -export-dynamic -o python \
                        Modules/python.o \
                        -L. -lpython2.7 -lpthread -ldl  -lpthread -lutil
-lm
_PYTHON_PROJECT_BASE=/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/build
_PYTHON_HOST_PLATFORM=linux2-x86_64
PYTHONPATH=/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/build/build/lib.linux2-x86_64-2.7:/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/Python-2.7.9/Lib:/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/Python-2.7.9/Lib/plat-linux2
python2.7 -S -m sysconfig --generate-posix-vars ;\
        if test $? -ne 0 ; then \
                echo "generate-posix-vars failed" ; \
                rm -f ./pybuilddir.txt ; \
                exit 1 ; \
        fi
Illegal instruction (core dumped)
make: *** [sharedmods] Error 132
WARNING: exit code 1 from a shell command.
ERROR: oe_runmake failed
ERROR: Function failed: do_install (log file is located at
/projects/yocto-git/build/tmp/work/haswell-diags-linux/python/2.7.9-r1/temp/log.do_install.17258)

Here is my tune-haswell.inc (ignore some copy/paste comment issues right
now =):

# Settings for the GCC(1) cpu-type "haswell":
#
#     Intel Core i7 CPU with 64-bit extensions, MOVBE, MMX, SSE, SSE2,
SSE3,·
#     SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES, PCLMUL, FSGSBASE,
#     RDRND, FMA, BMI, BMI2 and F16C instruction set support.
#
# This tune is recommended for Intel Nehalem and Silvermont (e.g. Bay
Trail) CPUs
# (and beyond).
#
DEFAULTTUNE ?= "haswell"

# Pull in the previous tune in to pull in PACKAGE_EXTRA_ARCHS
require conf/machine/include/tune-corei7.inc

# Extra tune features
TUNEVALID[haswell] = "Enable haswell specific processor optimizations"
TUNE_CCARGS .= "${@bb.utils.contains("TUNE_FEATURES", "haswell", "
-march=haswell -mtune=haswell -mfpmath=sse -mavx2", "", d)}"

# Extra tune selections
AVAILTUNES += "haswell"
TUNE_FEATURES_tune-haswell = "${TUNE_FEATURES_tune-x86-64} haswell"
BASE_LIB_tune-haswell = "lib"
TUNE_PKGARCH_tune-haswell = "haswell"
PACKAGE_EXTRA_ARCHS_tune-haswell = "${PACKAGE_EXTRA_ARCHS_tune-corei7}
haswell"
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