linux-kernel - Re: [PATCH v1 0/3] 2 memory fixes and a build fix

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Message-ID: <fe2b22aa-ad48-4279-89c0-2d846d1d405a@linaro.org>
Date: Tue, 24 Sep 2024 10:18:18 +0100
From: James Clark <james.clark@...aro.org>
To: Ian Rogers <irogers@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Kajol Jain <kjain@...ux.ibm.com>,
 Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
 "Steinar H. Gunderson" <sesse@...gle.com>,
 Masami Hiramatsu <mhiramat@...nel.org>, "David S. Miller"
 <davem@...emloft.net>, Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 Alexander Lobakin <aleksander.lobakin@...el.com>,
 Hemant Kumar <hemant@...ux.vnet.ibm.com>, linux-perf-users@...r.kernel.org,
 linux-kernel@...r.kernel.org, Yang Jihong <yangjihong@...edance.com>,
 leo.yan@....com
Subject: Re: [PATCH v1 0/3] 2 memory fixes and a build fix

On 24/09/2024 1:37 am, Ian Rogers wrote:
> I was looking into some lsan regressions and a latent issue with
> libdw, creating these fixes.
> 
> A thought, we should probably simplify the libdw logic but rather than
> do it here I'll do it as a separate series on top of these. The issues
> I see are:
> 
> 1) dwfl_thread_getframes is used to test for the presence of
>     libdw-dwarf-unwind. The blame date on this function is
>     2013-05-30. As the function is 10 years old I think having libdw
>     implies having dwfl_thread_getframes and so we can just merge the
>     two pieces of logic instead of having different feature tests and
>     ifdefs.
> 
> 2) similarly, dwarf_getlocations has a blame date of 2013-08-23 so
>     let's just make libdw tests test for this and make having libdw
>     imply dwarf_getlocations support.
> 
> 3) similarly, dwarf_getcfi has a blame date of 2009-06-24 so let's
>     just make libdw tests test for this and make having libdw imply
>     dwarf_getcfi support.
> 
> 4) in Makefie.config feature-dwarf is a synonym for libdw support. I
>     think using the name libdw is more intention revealing as dwarf can
>     mean multiple things. Let's change HAVE_DWARF_SUPPORT to
>     HAVE_LIBDW_SUPPORT and all similar dwarf vs libdw names.
> 
> 5) We have "#if _ELFUTILS_PREREQ(0, 142)" testing for elfutils version
>     0.142. Elfutils 0.142 was released around 2009-06-13 (via git blame
>     on the NEWS file). Let's remove the #if and ensure elfutils feature
>     tests for at least 0.142. If someone were using an incredibly old
>     version then they'd lose some elfutils support, but given the 15
>     year old age of the library I find it unlikely anyone is doing
>     this. They can also just move to a newer version.
> 
>  From the mailing list I notice also overlap with the last patch and
> this series:
> https://lore.kernel.org/lkml/20240919013513.118527-1-yangjihong@bytedance.com/
> Simplifying the libdw support will address some of those issues too.
> 
> Ian Rogers (3):
>    perf disasm: Fix capstone memory leak
>    perf probe: Fix libdw memory leak
>    perf build: Fix !HAVE_DWARF_GETLOCATIONS_SUPPORT
> 
>   tools/perf/Makefile.config     |  6 ++++++
>   tools/perf/util/disasm.c       | 11 +++++++----
>   tools/perf/util/dwarf-aux.h    |  1 +
>   tools/perf/util/probe-finder.c |  5 +++++
>   4 files changed, 19 insertions(+), 4 deletions(-)
> 

Reviewed-by: James Clark <james.clark@...aro.org>