netdev - Re: [PATCH bpf] samples/bpf: kbuild: add CONFIG_SAMPLE

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Date:   Wed, 2 Oct 2019 10:48:54 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     Networking <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Björn Töpel <bjorn.topel@...el.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH bpf] samples/bpf: kbuild: add CONFIG_SAMPLE_BPF Kconfig

On Tue, Oct 1, 2019 at 11:16 PM Björn Töpel <bjorn.topel@...il.com> wrote:
>
> On Tue, 1 Oct 2019 at 14:33, Masahiro Yamada
> <yamada.masahiro@...ionext.com> wrote:
> >
> > Hi Bjorn
> >
> > On Tue, Oct 1, 2019 at 7:14 PM Björn Töpel <bjorn.topel@...il.com> wrote:
> > >
> [...]
> > >  subdir-$(CONFIG_SAMPLE_VFS)            += vfs
> > > +subdir-$(CONFIG_SAMPLE_BPF)            += bpf
> >
> >
> > Please keep samples/Makefile sorted alphabetically.
> >
>
> Thank you, I'll address that in the v2!
>
> >
> >
> >
> > I am not checking samples/bpf/Makefile, but
> > allmodconfig no longer compiles for me.
> >
> >
> >
> > samples/bpf/Makefile:209: WARNING: Detected possible issues with include path.
> > samples/bpf/Makefile:210: WARNING: Please install kernel headers
> > locally (make headers_install).
> > error: unable to create target: 'No available targets are compatible
> > with triple "bpf"'
> > 1 error generated.
> > readelf: Error: './llvm_btf_verify.o': No such file
> > *** ERROR: LLVM (llc) does not support 'bpf' target
> >    NOTICE: LLVM version >= 3.7.1 required
> >

So, samples/bpf intentionally opts out the normal build
because most of people fail to build it.

It must be fixed somehow
before supporting it in samples/Makefile.



> Yes, the BPF samples require clang/LLVM with BPF support to build. Any
> suggestion on a good way to address this (missing tools), better than
> the warning above? After the commit 394053f4a4b3 ("kbuild: make single
> targets work more correctly"), it's no longer possible to build
> samples/bpf without support in the samples/Makefile.


You can with

"make M=samples/bpf"



--
Best Regards
Masahiro Yamada