linux-kernel - [PATCH v2] perf: Fix display of kernel symbols

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Message-ID: <2ea4501209d5363bac71a6757fe91c0747558a42.1736329923.git.christophe.leroy@csgroup.eu>
Date: Wed,  8 Jan 2025 10:54:20 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: 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>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	linux-perf-users@...r.kernel.org,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH v2] perf: Fix display of kernel symbols

Since commit 659ad3492b91 ("perf maps: Switch from rbtree to lazily
sorted array for addresses"), perf doesn't display anymore kernel
symbols on powerpc, allthough it still detects them as kernel addresses.

	# Overhead  Command     Shared Object  Symbol
	# ........  ..........  ............. ......................................
	#
	    80.49%  Coeur main  [unknown]      [k] 0xc005f0f8
	     3.91%  Coeur main  gau            [.] engine_loop.constprop.0.isra.0
	     1.72%  Coeur main  [unknown]      [k] 0xc005f11c
	     1.09%  Coeur main  [unknown]      [k] 0xc01f82c8
	     0.44%  Coeur main  libc.so.6      [.] epoll_wait
	     0.38%  Coeur main  [unknown]      [k] 0xc0011718
	     0.36%  Coeur main  [unknown]      [k] 0xc01f45c0

This is because function maps__find_next_entry() now returns current
entry instead of next entry, leading to kernel map end address
getting mis-configured with its own start address instead of the
start address of the following map.

Fix it by really taking the next entry, also make sure that entry
follows current one by making sure entries are sorted.

Fixes: 659ad3492b91 ("perf maps: Switch from rbtree to lazily sorted array for addresses")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Reviewed-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
v2: Make sure the entries are sorted, if not sort them.
---
 tools/perf/util/maps.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/maps.c b/tools/perf/util/maps.c
index 432399cbe5dd..09c9cc326c08 100644
--- a/tools/perf/util/maps.c
+++ b/tools/perf/util/maps.c
@@ -1136,8 +1136,13 @@ struct map *maps__find_next_entry(struct maps *maps, struct map *map)
 	struct map *result = NULL;
 
 	down_read(maps__lock(maps));
+	while (!maps__maps_by_address_sorted(maps)) {
+		up_read(maps__lock(maps));
+		maps__sort_by_address(maps);
+		down_read(maps__lock(maps));
+	}
 	i = maps__by_address_index(maps, map);
-	if (i < maps__nr_maps(maps))
+	if (++i < maps__nr_maps(maps))
 		result = map__get(maps__maps_by_address(maps)[i]);
 
 	up_read(maps__lock(maps));
-- 
2.47.0