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

[Ian Rogers]

On Tue, Sep 24, 2024 at 11:40 AM Namhyung Kim <namhyung@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > ---
> > >   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@xxxxxxxxxx/
https://lore.kernel.org/lkml/20240924160418.1391100-8-irogers@xxxxxxxxxx/

Thanks,
Ian