netdev - Re: [PATCH 6/6] selftests, bpftool: Add build test for libbpf dynamic linking

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Date:   Mon, 2 Dec 2019 15:38:05 +0000
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     lkml <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Michael Petlan <mpetlan@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Andrii Nakryiko <andriin@...com>
Subject: Re: [PATCH 6/6] selftests, bpftool: Add build test for libbpf dynamic
 linking

Thanks Jiri ! A few comments inline.

2019-12-02 14:18 UTC+0100 ~ Jiri Olsa <jolsa@...nel.org>
> Adding new test to test_bpftool_build.sh script to
> test the dynamic linkage of libbpf for bpftool:
> 
>   $ ./test_bpftool_build.sh
>   [SNIP]
> 
>   ... with dynamic libbpf
> 
>   $PWD:    /home/jolsa/kernel/linux-perf/tools/bpf/bpftool
>   command: make -s -C ../../build/feature clean >/dev/null
>   command: make -s -C ../../lib/bpf clean >/dev/null
>   command: make -s -C ../../lib/bpf prefix=/tmp/tmp.fG8O2Ps8ER install_lib install_headers >/dev/null
>   Parsed description of 117 helper function(s)
>   command: make -s clean >/dev/null
>   command: make -s LIBBPF_DYNAMIC=1 LIBBPF_DIR=/tmp/tmp.fG8O2Ps8ER >/dev/null
>   binary:  /home/jolsa/kernel/linux-perf/tools/bpf/bpftool/bpftool
>   binary:  linked with libbpf
> 
> The test installs libbpf into temp directory
> and links bpftool dynamically with it.
> 
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  .../selftests/bpf/test_bpftool_build.sh       | 53 +++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/test_bpftool_build.sh b/tools/testing/selftests/bpf/test_bpftool_build.sh
> index ac349a5cea7e..e4a6a0520f8e 100755
> --- a/tools/testing/selftests/bpf/test_bpftool_build.sh
> +++ b/tools/testing/selftests/bpf/test_bpftool_build.sh
> @@ -85,6 +85,55 @@ make_with_tmpdir() {
>  	echo
>  }
>  
> +# Assumes current directory is tools/bpf/bpftool
> +make_with_dynamic_libbpf() {
> +	TMPDIR=$(mktemp -d)
> +	echo -e "\$PWD:    $PWD"
> +
> +	# It might be needed to clean build tree first because features
> +	# framework does not detect the change properly
> +	echo -e "command: make -s -C ../../build/feature clean >/dev/null"

(So far I did not echo the "make clean" commands, I printed only the
ones used to build bpftool. But that's your call.)

> +	make $J -s -C ../../build/feature clean >/dev/null
> +	if [ $? -ne 0 ] ; then
> +		ERROR=1
> +	fi
> +	echo -e "command: make -s -C ../../lib/bpf clean >/dev/null"
> +	make $J -s -C ../../lib/bpf clean >/dev/null
> +	if [ $? -ne 0 ] ; then
> +		ERROR=1
> +	fi
> +
> +	# Now install libbpf into TMPDIR
> +	echo -e "command: make -s -C ../../lib/bpf prefix=$TMPDIR install_lib install_headers >/dev/null"
> +	make $J -s -C ../../lib/bpf prefix=$TMPDIR install_lib install_headers >/dev/null
> +	if [ $? -ne 0 ] ; then
> +		ERROR=1
> +	fi
> +
> +	# And final bpftool build (with clean first) with libbpf dynamic link
> +	echo -e "command: make -s clean >/dev/null"
> +	if [ $? -ne 0 ] ; then
> +		ERROR=1
> +	fi

I do not believe you need to "make clean" here, this should have been
done by the previous test in that dir earlier in the script (cd
tools/bpf/bpftool; make_and_clean)

> +	echo -e "command: make -s LIBBPF_DYNAMIC=1 LIBBPF_DIR=$TMPDIR >/dev/null"
> +	make $J -s LIBBPF_DYNAMIC=1 LIBBPF_DIR=$TMPDIR >/dev/null
> +	if [ $? -ne 0 ] ; then
> +		ERROR=1
> +	fi
> +
> +	check .
> +	ldd bpftool | grep -q libbpf.so
> +	if [ $? -ne 0 ] ; then

(Or "if ldd bpftool | grep -q libbpf.so ; then")

> +		printf "FAILURE: Did not find libbpf linked\n"

Please also set $(ERROR) here.

(Also, stick to echo rather than mixing with printf? I can't remember
why I used one over echo in the check() function, that was probably not
on purpose.)

> +	else
> +		echo "binary:  linked with libbpf"
> +	fi
> +	make -s -C ../../lib/bpf clean
> +	make -s clean
> +	rm -rf -- $TMPDIR

We probably want to clean features too? We tried to check that libbpf
was available, but with a very specific $(LIBBPF_DIR), which was
temporary and no longer exist. So better to reset features to a clean state?

> +	echo
> +}
> +
>  echo "Trying to build bpftool"
>  echo -e "... through kbuild\n"
>  
> @@ -145,3 +194,7 @@ make_and_clean
>  make_with_tmpdir OUTPUT
>  
>  make_with_tmpdir O
> +
> +echo -e "... with dynamic libbpf\n"
> +
> +make_with_dynamic_libbpf
> 

Thanks,
Quentin