linux-kernel - [PATCH 1/3] perf-probe: Fix debuginfo__new() to enable build-id based debuginfo

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Message-Id: <162532651863.393143.11692691321219235810.stgit@devnote2>
Date:   Sun,  4 Jul 2021 00:35:18 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     linux-perf-users@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Stefan Liebler <stli@...ux.ibm.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] perf-probe: Fix debuginfo__new() to enable build-id based debuginfo

From: Masami Hiramatsu <mhriamat@...nel.org>

Fix debuginfo__new() to set the build-id to dso before
dso__read_binary_type_filename() so that it can find
DSO_BINARY_TYPE__BUILDID_DEBUGINFO debuginfo correctly.
However, this may not change the result, because elfutils
(libdwfl) has its own debuginfo finder. With/without this patch,
the perf probe correctly find the debuginfo file.

This is just a failsafe and keep code's sanity (if you use
dso__read_binary_type_filename(), you must set the build-id
to the dso.)

Reported-by: Thomas Richter <tmricht@...ux.ibm.com>
Signed-off-by: Masami Hiramatsu <mhriamat@...nel.org>
---
 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 b029c29ce227..02ef0d78053b 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -118,12 +118,17 @@ struct debuginfo *debuginfo__new(const char *path)
 	char buf[PATH_MAX], nil = '\0';
 	struct dso *dso;
 	struct debuginfo *dinfo = NULL;
+	struct build_id bid;
 
 	/* Try to open distro debuginfo files */
 	dso = dso__new(path);
 	if (!dso)
 		goto out;
 
+	/* Set the build id for DSO_BINARY_TYPE__BUILDID_DEBUGINFO */
+	if (is_regular_file(path) && filename__read_build_id(path, &bid) > 0)
+		dso__set_build_id(dso, &bid);
+
 	for (type = distro_dwarf_types;
 	     !dinfo && *type != DSO_BINARY_TYPE__NOT_FOUND;
 	     type++) {