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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Fri, 4 Jan 2019 18:16:31 +0100
Message-ID: <CAMuHMdXRN=mSKTjZNBSxQi-pkgSrKqeANxD-GB+hqC8pDjx7nQ@mail.gmail.com>
Subject: Re: selftests/bpf doesn't compile
To:     Shuah Khan <shuah@kernel.org>
Cc:     Daniel Borkmann <daniel@iogearbox.net>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        Thomas Meyer <thomas@m3y3r.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        Shuah Khan <shuahkh@osg.samsung.com>,
        Networking <netdev@vger.kernel.org>,
        Masahiro Yamada <yamada.masahiro@socionext.com>,
        linux-kbuild <linux-kbuild@vger.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Shuah,

CC kbuild, gpio

On Thu, Sep 14, 2017 at 5:34 PM Shuah Khan <shuah@kernel.org> wrote:
> bpf test depends on clang and fails to compile when
>
> ------------------------------------------------------
> make -C tools/testing/selftests/bpf run_tests
>
>
> make: clang: Command not found
> Makefile:39: recipe for target '.linux-kselftest/tools/testing/selftests/bpf/test_pkt_access.o' failed
> make: *** [./linux-kselftest/tools/testing/selftests/bpf/test_pkt_access.o] Error 127
> make: Leaving directory '.linux-kselftest/tools/testing/selftests/bpf'

The above failure is indeed due to missing clang.

> With "make TARGETS=bpf kselftest" it fails earlier:
>
> make[3]: Entering directory './linux-kselftest/tools/lib/bpf'
> Makefile:40: tools/scripts/Makefile.arch: No such file or directory
> Makefile:84: tools/build/Makefile.feature: No such file or directory
> Makefile:143: tools/build/Makefile.include: No such file or directory

This is due to srctree being "." instead of the actual source tree,
when invoked as "make kselftest".
When using "make -C tools/testing/selftests", srctree is correct.

tools/testing/selftests/bpf/Makefile has:

    $(BPFOBJ): force
            $(MAKE) -C $(BPFDIR) OUTPUT=$(OUTPUT)/

to enter the tools/lib/bpf directory to force a build of libbpf.a

Note that tools/gpio has the same issue.

There seem to be _four_ different ways to build kselftests
(Documentation/dev-tools/kselftest.rst):

    make kselftest
    make O=/path/to/output kselftest
    make -C tools/testing/selftests
    make O=/path/to/output -C tools/testing/selftests

I'm not so fond of the latter two, as they basically run make from
somewhere inside the tree, which complicates things. I believe we don't
support this anywhere else.

Each of the four seem to have (different) issues. Especially when you
throw cross-compiling into the mix. And care about where installed
headers end up (yes, kselftest calls headers_install internally).

I'm working on fixes for some of them, but I don't know how to fix the
srctree issue.

Anyone with a suggestion?

Thanks!

> make[3]: *** No rule to make target 'tools/build/Makefile.include'.  Stop.
> make[3]: Leaving directory '.linux-kselftest/tools/lib/bpf'
> Makefile:34: recipe for target './linux-kselftest/tools/testing/selftests/bpf/libbpf.a' failed
> make[2]: *** [./linux-kselftest/tools/testing/selftests/bpf/libbpf.a] Error 2
> make[2]: Leaving directory './linux-kselftest/tools/testing/selftests/bpf'
> Makefile:69: recipe for target 'all' failed
> make[1]: *** [all] Error 2
> Makefile:1190: recipe for target 'kselftest' failed
> make: *** [kselftest] Error 2

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds