[PATCH v5 bpf-next 00/15] samples: bpf: improve/fix cross-compilation

From: Ivan Khoronzhuk
Date: Thu Oct 10 2019 - 20:29:51 EST

This series contains mainly fixes/improvements for cross-compilation
but not only, tested for arm, arm64, and intended for any arch.
Also verified on native build (not cross compilation) for x86_64
and arm, arm64.

Initial RFC link:

Prev. version:

Besides the patches given here, the RFC also contains couple patches
related to llvm clang
arm: include: asm: swab: mask rev16 instruction for clang
arm: include: asm: unified: mask .syntax unified for clang
They are necessarily to verify arm 32 build.

Also, couple more fixes were added but are not merged in bpf-next yet,
they can be needed for verification/configuration steps, if not in
your tree the fixes can be taken here:

Now, to build samples, SAMPLE_BPF should be enabled in config.

The change touches not only cross-compilation and can have impact on
other archs and build environments, so might be good idea to verify
it in order to add appropriate changes, some warn options could be
tuned also.

All is tested on x86-64 with clang installed (has to be built containing
targets for arm, arm64..., see llc --version, usually it's present already)

Instructions to test native on x86_64
Native build on x86_64 is done in usual way and shouldn't have difference
except HOSTCC is now printed as CC wile building the samples.

Instructions to test cross compilation on arm64
#Toolchain used for test:
gcc version 8.3.0
(GNU Toolchain for the A-profile Architecture 8.3-2019.03 (arm-rel-8.36))

# Get some arm64 FS, containing at least libelf
I've used sdk for TI am65x got here:

# Install this binary to some dir, say "sdk".
# Configure kernel (use defconfig as no matter), but clean everything
# before.
make ARCH=arm64 -C tools/ clean
make ARCH=arm64 -C samples/bpf clean
make ARCH=arm64 clean
make ARCH=arm64 defconfig

# Enable SAMPLE_BPF and it's dependencies in config

# The kernel version used in sdk doesn't correspond to checked one,
# but for this verification only headers need to be syched,
# so install them (can be enabled in config):
make ARCH=arm64 headers_install

# or on SDK if need keep them in sync (not necessarily to verify):

make ARCH=arm64 INSTALL_HDR_PATH=/../sdk/\
aarch64-linux/usr headers_install

# Build samples
make samples/bpf/ ARCH=arm64 CROSS_COMPILE="aarch64-linux-gnu-"\

Instructions to test cross compilation on arm
#Toolchains used for test:
arm-linux-gnueabihf-gcc (Linaro GCC 7.2-2017.11) 7.2.1 20171011
(GNU Toolchain for the A-profile Architecture 8.3-2019.03 \
(arm-rel-8.36)) 8.3.0

# Get some FS, I've used sdk for TI am52xx got here:

# Install this binary to some dir, say "sdk".
# Configure kernel, but clean everything before.
make ARCH=arm -C tools/ clean
make ARCH=arm -C samples/bpf clean
make ARCH=arm clean
make ARCH=arm omap2plus_defconfig

# The kernel version used in sdk doesn't correspond to checked one, but
# headers only should be synched,
# so install them (can be enabled in config):

make ARCH=arm headers_install

# or on SDK if need keep them in sync (not necessarily):

make ARCH=arm INSTALL_HDR_PATH=/../sdk/\
armv7ahf-neon-linux-gnueabi/usr headers_install

# Build samples
make samples/bpf/ ARCH=arm CROSS_COMPILE="arm-linux-gnueabihf-"\

Based on bpf-next/master

- any changes, only missed SOBs are added

- used filter for ARCH_ARM_SELECTOR
- omit "-fomit-frame-pointer" and use same flags for native and "cross"
- used sample/bpf prefixes
- use C instead of C++ compiler for test_libbpf target

- renamed makefile.progs to makeifle.target, as more appropriate
- left only __LINUX_ARM_ARCH__ for D options for arm
- for host build - left options from KBUILD_HOST for compatibility reasons
- split patch adding c/cxx/ld flags to libbpf by modules
- moved readme change to separate patch
- added patch setting options for cross-compile
- fixed issue with option error for syscall_nrs.S,
avoiding overlap for ccflags-y.

- restructured patches order
- split "samples: bpf: Makefile: base progs build on Makefile.progs"
to make change more readable. It added couple nice extra patches.
- removed redundant patch:
"samples: bpf: Makefile: remove target for native build"
- added fix:
"samples: bpf: makefile: fix cookie_uid_helper_example obj build"
- limited -D option filter only for arm
- improved comments
- added couple instructions to verify cross compilation for arm and
arm64 arches based on TI am57xx and am65xx sdks.
- corrected include a little order

Ivan Khoronzhuk (15):
samples/bpf: fix HDR_PROBE "echo"
samples/bpf: fix cookie_uid_helper_example obj build
samples/bpf: use --target from cross-compile
samples/bpf: use own EXTRA_CFLAGS for clang commands
samples/bpf: use __LINUX_ARM_ARCH__ selector for arm
samples/bpf: drop unnecessarily inclusion for bpf_load
samples/bpf: add makefile.target for separate CC target build
samples/bpf: base target programs rules on Makefile.target
samples/bpf: use own flags but not HOSTCFLAGS
samples/bpf: use target CC environment for HDR_PROBE
libbpf: don't use cxx to test_libpf target
libbpf: add C/LDFLAGS to libbpf.so and test_libpf targets
samples/bpf: provide C/LDFLAGS to libbpf
samples/bpf: add sysroot support
samples/bpf: add preparation steps and sysroot info to readme

samples/bpf/Makefile | 164 ++++++++++--------
samples/bpf/Makefile.target | 75 ++++++++
samples/bpf/README.rst | 41 ++++-
tools/lib/bpf/Makefile | 23 +--
.../bpf/{test_libbpf.cpp => test_libbpf.c} | 14 +-
5 files changed, 218 insertions(+), 99 deletions(-)
create mode 100644 samples/bpf/Makefile.target
rename tools/lib/bpf/{test_libbpf.cpp => test_libbpf.c} (61%)