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From:   Ian Rogers <irogers@google.com>
Date:   Tue, 12 Dec 2023 10:10:37 -0800
Message-ID: <CAP-5=fV5sA1ga5UfvHW_=Ep25b-TzsLJ8Atqk3KePKOx-fk9TQ@mail.gmail.com>
Subject: Re: [PATCH 0/3] perf tools: Random fixes for DWARF unwind
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org,
        Milian Wolff <milian.wolff@kdab.com>,
        Pablo Galindo <pablogsal@gmail.com>,
        Fangrui Song <maskray@google.com>
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On Mon, Dec 11, 2023 at 11:05=E2=80=AFPM Namhyung Kim <namhyung@kernel.org>=
 wrote:
>
> Hello,
>
> I've found a couple of issues on the unwind code while I'm playing with
> the JIT-dump code for the CPython.  The code assumes normal DSOs mapped
> from the beginning of the file and aligned to the page size.  But it's
> not true for the JIT-dumped DSOs which are generated for each function.

We have a JIT test in:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git/tr=
ee/tools/perf/tests/shell/test_java_symbol.sh?h=3Dperf-tools-next

It'd be great if we could do similar for CPython.

Thanks,
Ian


> Depending on the JIT implementation, the code address and accompanied
> ELF info (like ELF file headers and unwind info) can be overlapped to
> adjacent (JIT-dumped) DSOs.  So it should take more care when it
> calculates the mapping address for the DSO.
>
> It seems these changes need to go to the stable trees but they are
> changed a lot since then so I'm not sure.
>
> Thanks,
> Namhyung
>
>
> Namhyung Kim (3):
>   perf genelf: Set ELF program header addresses properly
>   perf unwind-libdw: Handle JIT-generated DSOs properly
>   perf unwind-libunwind: Fix base address for .eh_frame
>
>  tools/perf/util/genelf.c                 |  6 +++---
>  tools/perf/util/unwind-libdw.c           | 21 +++++++++++++++++----
>  tools/perf/util/unwind-libunwind-local.c |  2 +-
>  3 files changed, 21 insertions(+), 8 deletions(-)
>
> --
> 2.43.0.472.g3155946c3a-goog
>