linux-kernel - Re: BPF relocation 'perf test' entries failing was: Re: [GIT PULL 00/27] perf/core improvements and fixes

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Message-ID: <20180726191435.GB20438@kernel.org>
Date:   Thu, 26 Jul 2018 16:14:35 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Sandipan Das <sandipan@...ux.ibm.com>
Cc:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Ingo Molnar <mingo@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Clark Williams <williams@...hat.com>,
        linux-perf-users@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wang Nan <wangnan0@...wei.com>, linux-kernel@...r.kernel.org,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Hendrik Brueckner <brueckner@...ux.ibm.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>
Subject: Re: BPF relocation 'perf test' entries failing was: Re: [GIT PULL
 00/27] perf/core improvements and fixes

Em Thu, Jul 26, 2018 at 03:58:05PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Jul 26, 2018 at 11:04:08PM +0530, Sandipan Das escreveu:
> > I came across the same problem. Does the following patch fix it?

> > https://lkml.org/lkml/2018/7/26/669
 
> Oh my, that one was subtle... Checking...

Right, when it said it was running:

  40.3: BPF prologue generation

In fact it was running:

  40.4: BPF relocation checker

That error message in the 'perf test -v' output:

  libbpf: Program 'func=sys_write' contains non-map related relo data pointing to section 65522

Was the _expected_ one for "40.4: BPF relocation checker", then it
failed when it couldn't run the off by one "last" subtest, duh.

Thomas, this was a problem introduced by a patch from you, just for
reference, this one:

    Fixes: 9ef0112442bd ("perf test: Fix subtest number when showing results")

I should have caught this by running 'perf test' before/after applying
that patch, I'll now make sure this is done before sending pull reqs
upstream.

In fact I did after, and thought, hey, some BPF related regression, I
must've updated clang/llvm and something new appeared on the radar, so I
went that direction and went nowhere, well, now I have an uptodate
llvm/clang combo to play with BTF, pahole, etc 8-)

Thanks!

- Arnaldo