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Date:   Fri, 20 Oct 2023 17:39:25 -0300
From:   Arnaldo Carvalho de Melo <acme@kernel.org>
To:     Manu Bretelle <chantr4@gmail.com>
Cc:     Ian Rogers <irogers@google.com>,
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        Quentin Monnet <quentin@isovalent.com>
Subject: Re: [PATCH v1 1/4] perf parse-events: Remove BPF event support
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Em Thu, Oct 19, 2023 at 03:48:56PM -0700, Manu Bretelle escreveu:
> On Thu, Oct 19, 2023 at 06:08:33PM -0300, Arnaldo Carvalho de Melo wrote:
> > I wonder how to improve the current situation to detect these kinds of
> > problems in the future, i.e. how to notice that some file needed by some
> > Makefile, etc got removed or that some feature test fails because some
> > change in the test .c files makes them fail and thus activates fallbacks
> > like the one above :-\
 
> I think it is tricky. Specifically to this situation, some CI could try to build
> the different combinaison of bpftool and check the features through the build
> `bpftool --version`.

Right, if the right packages are installed, we expect to get some
bpftool build output, if that changes after some patch, flag it.

Does bpftool have something like:

⬢[acme@toolbox perf-tools-next]$ perf version --build-options
perf version 6.6.rc1.ga8dd62d05e56
                 dwarf: [ on  ]  # HAVE_DWARF_SUPPORT
    dwarf_getlocations: [ on  ]  # HAVE_DWARF_GETLOCATIONS_SUPPORT
         syscall_table: [ on  ]  # HAVE_SYSCALL_TABLE_SUPPORT
                libbfd: [ OFF ]  # HAVE_LIBBFD_SUPPORT
            debuginfod: [ on  ]  # HAVE_DEBUGINFOD_SUPPORT
                libelf: [ on  ]  # HAVE_LIBELF_SUPPORT
               libnuma: [ on  ]  # HAVE_LIBNUMA_SUPPORT
numa_num_possible_cpus: [ on  ]  # HAVE_LIBNUMA_SUPPORT
               libperl: [ on  ]  # HAVE_LIBPERL_SUPPORT
             libpython: [ on  ]  # HAVE_LIBPYTHON_SUPPORT
              libslang: [ on  ]  # HAVE_SLANG_SUPPORT
             libcrypto: [ on  ]  # HAVE_LIBCRYPTO_SUPPORT
             libunwind: [ on  ]  # HAVE_LIBUNWIND_SUPPORT
    libdw-dwarf-unwind: [ on  ]  # HAVE_DWARF_SUPPORT
                  zlib: [ on  ]  # HAVE_ZLIB_SUPPORT
                  lzma: [ on  ]  # HAVE_LZMA_SUPPORT
             get_cpuid: [ on  ]  # HAVE_AUXTRACE_SUPPORT
                   bpf: [ on  ]  # HAVE_LIBBPF_SUPPORT
                   aio: [ on  ]  # HAVE_AIO_SUPPORT
                  zstd: [ on  ]  # HAVE_ZSTD_SUPPORT
               libpfm4: [ on  ]  # HAVE_LIBPFM
         libtraceevent: [ on  ]  # HAVE_LIBTRACEEVENT
         bpf_skeletons: [ on  ]  # HAVE_BPF_SKEL
⬢[acme@toolbox perf-tools-next]$

?

> This is actually a test that I run internally to make sure our build has some
> feature enabled.
> This is actually tested by bpftool in the GH CI:
> https://github.com/libbpf/bpftool/blob/main/.github/workflows/build.yaml#L62
 
> As a matter of fact, it would not have been detected because that CI uses a
> different Makefile.feature.
 
> Quentin and I were talking offline how we could improve bpftool CI at diff time.
> This is an example where it would have helped :)
> 
> > I'll get this merged in my perf-tools-fixes-for-v6.6 that I'll submit
> > tomorrow to Linus, thanks for reporting!
> > 
> > I'll add your:
> > 
> > Reported-by: Manu Bretelle <chantr4@gmail.com>
> > 
> > And:
> > 
> > Fixes: 56b11a2126bf2f42 ("perf bpf: Remove support for embedding clang for compiling BPF events (-e foo.c)")
> > 
> > Ok?
 
> SGTM. Thanks for the quick turnaround.
 
> Reviewed-by: Manu Bretelle <chantr4@gmail.com>

You're welcome, thanks for the detailed report, the patch was just sent
to Linus.

- Arnaldo