selftests/bpf: Better clean up for runqslower in test_bpftool_build.sh

The script test_bpftool_build.sh attempts to build bpftool in the
various supported ways, to make sure nothing breaks.

One of those ways is to run "make tools/bpf" from the root of the kernel
repository. This command builds bpftool, along with the other tools
under tools/bpf, and runqslower in particular. After running the
command and upon a successful bpftool build, the script attempts to
cleanup the generated objects. However, after building with this target
and in the case of runqslower, the files are not cleaned up as expected.

This is because the "tools/bpf" target sets $(OUTPUT) to
.../tools/bpf/runqslower/ when building the tool, causing the object
files to be placed directly under the runqslower directory. But when
running "cd tools/bpf; make clean", the value for $(OUTPUT) is set to
".output" (relative to the runqslower directory) by runqslower's
Makefile, and this is where the Makefile looks for files to clean up.

We cannot easily fix in the root Makefile (where "tools/bpf" is defined)
or in tools/scripts/Makefile.include (setting $(OUTPUT)), where changing
the way the output variables are passed would likely have consequences
elsewhere. We could change runqslower's Makefile to build in the
repository instead of in a dedicated ".output/", but doing so just to
accommodate a test script doesn't sound great. Instead, let's just make
sure that we clean up runqslower properly by adding the correct command
to the script.

This will attempt to clean runqslower twice: the first try with command
"cd tools/bpf; make clean" will search for tools/bpf/runqslower/.output
and fail to clean it (but will still clean the other tools, in
particular bpftool), the second one (added in this commit) sets the
$(OUTPUT) variable like for building with the "tool/bpf" target and
should succeed.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211007194438.34443-12-quentin@isovalent.com

selftests/bpf: Exit with KSFT_SKIP if no Makefile found

This would happend when we run the tests after install kselftests
root@lkp-skl-d01 ~# /kselftests/run_kselftest.sh -t bpf:test_doc_build.sh
TAP version 13
1..1
# selftests: bpf: test_doc_build.sh
perl: warning: Setting locale failed.
perl: warning: Please check that your locale settings:
LANGUAGE = (unset),
LC_ALL = (unset),
LC_ADDRESS = "en_US.UTF-8",
LC_NAME = "en_US.UTF-8",
LC_MONETARY = "en_US.UTF-8",
LC_PAPER = "en_US.UTF-8",
LC_IDENTIFICATION = "en_US.UTF-8",
LC_TELEPHONE = "en_US.UTF-8",
LC_MEASUREMENT = "en_US.UTF-8",
LC_TIME = "en_US.UTF-8",
LC_NUMERIC = "en_US.UTF-8",
LANG = "en_US.UTF-8"
are supported and installed on your system.
perl: warning: Falling back to the standard locale ("C").
# skip: bpftool files not found!
#
ok 1 selftests: bpf: test_doc_build.sh # SKIP

Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210820025549.28325-1-lizhijian@cn.fujitsu.com

tools/bpf: Remove bpf-helpers from bpftool docs

This logic is used for validating the manual pages from selftests, so
move the infra under tools/testing/selftests/bpf/ and rely on selftests
for validation rather than tying it into the bpftool build.

Signed-off-by: Joe Stringer <joe@cilium.io>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210302171947.2268128-12-joe@cilium.io

selftests, bpftool: Add bpftool (and eBPF helpers) documentation build

eBPF selftests include a script to check that bpftool builds correctly
with different command lines. Let's add one build for bpftool's
documentation so as to detect errors or warning reported by rst2man when
compiling the man pages. Also add a build to the selftests Makefile to
make sure we build bpftool documentation along with bpftool when
building the selftests.

This also builds and checks warnings for the man page for eBPF helpers,
which is built along bpftool's documentation.

This change adds rst2man as a dependency for selftests (it comes with
Python's "docutils").

v2:
- Use "--exit-status=1" option for rst2man instead of counting lines
from stderr.
- Also build bpftool as part as the selftests build (and not only when
the tests are actually run).

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200909162251.15498-3-quentin@isovalent.com

selftests, bpftool: Skip the build test if not in tree

If selftests are copied over to another machine/location
for execution the build test of bpftool will obviously
not work, since the sources are not copied.
Skip it if we can't find bpftool's Makefile.

Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20191119105010.19189-3-quentin.monnet@netronome.com

selftests, bpftool: Set EXIT trap after usage function

The trap on EXIT is used to clean up any temporary directory left by the
build attempts. It is not needed when the user simply calls the script
with its --help option, and may not be needed either if we add checks
(e.g. on the availability of bpftool files) before the build attempts.

Let's move this trap and related variables lower down in the code, so
that we don't accidentally change the value returned from the script
on early exits at pre-checks.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Link: https://lore.kernel.org/bpf/20191119105010.19189-2-quentin.monnet@netronome.com

tools: bpftool: improve and check builds for different make invocations

There are a number of alternative "make" invocations that can be used to
compile bpftool. The following invocations are expected to work:

- through the kbuild system, from the top of the repository
(make tools/bpf)
- by telling make to change to the bpftool directory
(make -C tools/bpf/bpftool)
- by building the BPF tools from tools/
(cd tools && make bpf)
- by running make from bpftool directory
(cd tools/bpf/bpftool && make)

Additionally, setting the O or OUTPUT variables should tell the build
system to use a custom output path, for each of these alternatives.

The following patch fixes the following invocations:

$ make tools/bpf
$ make tools/bpf O=<dir>
$ make -C tools/bpf/bpftool OUTPUT=<dir>
$ make -C tools/bpf/bpftool O=<dir>
$ cd tools/ && make bpf O=<dir>
$ cd tools/bpf/bpftool && make OUTPUT=<dir>
$ cd tools/bpf/bpftool && make O=<dir>

After this commit, the build still fails for two variants when passing
the OUTPUT variable:

$ make tools/bpf OUTPUT=<dir>
$ cd tools/ && make bpf OUTPUT=<dir>

In order to remember and check what make invocations are supposed to
work, and to document the ones which do not, a new script is added to
the BPF selftests. Note that some invocations require the kernel to be
configured, so the script skips them if no .config file is found.

v2:
- In make_and_clean(), set $ERROR to 1 when "make" returns non-zero,
even if the binary was produced.
- Run "make clean" from the correct directory (bpf/ instead of bpftool/,
when relevant).

Reported-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>