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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Fri, 20 Dec 2019 17:47:48 -0300
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Namhyung Kim <namhyung@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Martin KaFai Lau <kafai@fb.com>,
        Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>,
        Andrii Nakryiko <andriin@fb.com>, bpf <bpf@vger.kernel.org>,
        Jiri Olsa <jolsa@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] libbpf: Fix build on read-only filesystems
Message-ID: <20191220204748.GA9076@kernel.org>
References: <20191220032558.3259098-1-namhyung@kernel.org>
 <CAEf4BzaZBSRK2M4LD-c12_2-QLa8+jpPs1E4nA9BNeUDskOMBQ@mail.gmail.com>
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Em Fri, Dec 20, 2019 at 12:29:36PM -0800, Andrii Nakryiko escreveu:
> On Thu, Dec 19, 2019 at 7:26 PM Namhyung Kim <namhyung@kernel.org> wrote:
> > I got the following error when I tried to build perf on a read-only
> > filesystem with O=dir option.
> >
> >   $ cd /some/where/ro/linux/tools/perf
> >   $ make O=$HOME/build/perf
> >   ...
> >     CC       /home/namhyung/build/perf/lib.o
> >   /bin/sh: bpf_helper_defs.h: Read-only file system
> >   make[3]: *** [Makefile:184: bpf_helper_defs.h] Error 1
> >   make[2]: *** [Makefile.perf:778: /home/namhyung/build/perf/libbpf.a] Error 2
> >   make[2]: *** Waiting for unfinished jobs....
> >     LD       /home/namhyung/build/perf/libperf-in.o
> >     AR       /home/namhyung/build/perf/libperf.a
> >     PERF_VERSION = 5.4.0
> >   make[1]: *** [Makefile.perf:225: sub-make] Error 2
> >   make: *** [Makefile:70: all] Error 2
> >
> > It was becaused bpf_helper_defs.h was generated in current directory.
> > Move it to OUTPUT directory.
> >
> > Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> > ---
> 
> Overall nothing is obviously broken, except you need to fix up
> selftests/bpf's Makefile as well.
> 
> BTW, this patch doesn't apply cleanly to latest bpf-next, so please rebase.
> 
> Also subject prefix should look like [PATCH bpf-next] if it's meant to
> be applied against bpf-next.

Shouldn't this be applied to the current merge window since a behaviour
that people relied, i.e. using O= to generate the build in a separate
directory, since its not possible to use the source dir tree as it is
read-only is now broken, i.e. isn't this a regression?

- Arnaldo
 
> >  tools/lib/bpf/Makefile | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> >
> 
> [...]

-- 

- Arnaldo