linux-kernel - [PATCH v3] perf: fix the probe finder location (.dwo files)

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Date:   Wed,  5 Oct 2022 08:47:02 -0400
From:   Henry Castro <hcvcastro@...il.com>
To:     namhyung@...nel.org
Cc:     Henry Castro <hcvcastro@...il.com>,
        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>, linux-perf-users@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3] perf: fix the probe finder location (.dwo files)

If the file object is compiled using -gsplit-dwarf,
the probe finder location will fail.

Signed-off-by: Henry Castro <hcvcastro@...il.com>
---

> Nit, I think we use _ELFUTILS_PREREQ(0, 171).
Thank you

> How about making it a separate function with 2 versions
> depending on the elfutils?  Then you can have the variables
> only if they are used.

> Something like get_source_from_debuginfod() in the same
> file.

Sounds good, but I prefer simplicity in the patch =),
what do you think about
{
	Dwarf_Die cudie, subdie;
	if (dwarf_cu_info() ..)
	..
}

to resolve unused variable?
}


 tools/perf/util/probe-finder.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index 50d861a80f57..5f6781e712db 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -1200,6 +1200,20 @@ static int debuginfo__find_probe_location(struct debuginfo *dbg,
 			continue;
 		}

+#if _ELFUTILS_PREREQ(0, 171)
+		{
+			uint8_t unit_type;
+			Dwarf_Die cudie, subdie;
+
+			/* Check separate debug information file. */
+			if (dwarf_cu_info(pf->cu_die.cu, NULL,
+					  &unit_type, &cudie,
+					  &subdie, NULL,
+					  NULL, NULL) == 0
+			    && unit_type == DW_UT_skeleton)
+				pf->cu_die = subdie;
+		}
+#endif
 		/* Check if target file is included. */
 		if (pp->file)
 			pf->fname = cu_find_realpath(&pf->cu_die, pp->file);
--
2.20.1