linux-kernel - Re: [PATCH v1 2/3] perf probe: Fix libdw memory leak

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Message-ID: <ZvOnATEtJJQWhThK@google.com>
Date: Tue, 24 Sep 2024 23:00:34 -0700
From: Namhyung Kim <namhyung@...nel.org>
To: Ian Rogers <irogers@...gle.com>
Cc: James Clark <james.clark@...aro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...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 2/3] perf probe: Fix libdw memory leak

On Tue, Sep 24, 2024 at 12:47:33PM -0700, Ian Rogers wrote:
> On Tue, Sep 24, 2024 at 11:40 AM Namhyung Kim <namhyung@...nel.org> wrote:
> >
> > On Tue, Sep 24, 2024 at 10:17:08AM +0100, James Clark wrote:
> > >
> > >
> > > On 24/09/2024 1:37 am, Ian Rogers wrote:
> > > > Add missing dwarf_cfi_end to free memory associated with probe_finder
> > > > cfi_eh or cfi_dbg. This addresses leak sanitizer issues seen in:
> > > > tools/perf/tests/shell/test_uprobe_from_different_cu.sh
> > > >
> > > > Fixes: 270bde1e76f4 ("perf probe: Search both .eh_frame and .debug_frame sections for probe location")
> > > > Signed-off-by: Ian Rogers <irogers@...gle.com>
> > > > ---
> > > >   tools/perf/util/probe-finder.c | 5 +++++
> > > >   1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
> > > > index 630e16c54ed5..78f34fa0c391 100644
> > > > --- a/tools/perf/util/probe-finder.c
> > > > +++ b/tools/perf/util/probe-finder.c
> > > > @@ -1379,6 +1379,11 @@ int debuginfo__find_trace_events(struct debuginfo *dbg,
> > > >     if (ret >= 0 && tf.pf.skip_empty_arg)
> > > >             ret = fill_empty_trace_arg(pev, tf.tevs, tf.ntevs);
> > > > +#if _ELFUTILS_PREREQ(0, 142)
> > > > +   dwarf_cfi_end(tf.pf.cfi_eh);
> > > > +   dwarf_cfi_end(tf.pf.cfi_dbg);
> > > > +#endif
> > > > +
> > >
> > > I noticed that c06547d converted an _ELFUTILS_PREREQ(0, 142) into
> > > HAVE_DWARF_CFI_SUPPORT. But there is still a mixture of both in the code
> > > (unrelated to this patch). The commit message doesn't say why it is better,
> > > just that it could be changed, so I'm not sure which one is right.
> >
> > I think HAVE_DWARF_CFI_SUPPORT is better since it reveals the intention
> > clearly.
> 
> Let's just nuke the conditional compilation, the CFI support is in
> libdw (calling it dwarf is just actively confusing) is 15 years old:
> https://lore.kernel.org/lkml/20240924160418.1391100-7-irogers@google.com/
> https://lore.kernel.org/lkml/20240924160418.1391100-8-irogers@google.com/

Sounds good as long as we checks the version or the API in the feature
test.

Thanks,
Namhyung