linux-kernel - [PATCH/RFC 6/9] perf symbols: Use already loaded module dso when loading kcore

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Date:   Fri, 23 Jun 2017 14:48:24 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Wang Nan <wangnan0@...wei.com>
Subject: [PATCH/RFC 6/9] perf symbols: Use already loaded module dso when loading kcore

Even every module has loaded onto same addresses, some modules can be
changed and reloaded.  In that case it needs to access to the old module
in the build-id cache.

Cc: Adrian Hunter <adrian.hunter@...el.com>
Cc: Wang Nan <wangnan0@...wei.com>
Signed-off-by: Namhyung Kim <namhyung@...nel.org>
---
 tools/perf/util/symbol.c | 45 +++++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index ce79a51f25bf..fe46eb782297 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -1155,6 +1155,7 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	int err, fd;
 	char kcore_filename[PATH_MAX];
 	struct symbol *sym;
+	struct map_groups old_mg;
 
 	if (!kmaps)
 		return -EINVAL;
@@ -1196,15 +1197,8 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 		goto out_err;
 	}
 
-	/* Remove old maps */
-	old_map = map_groups__first(kmaps, map->type);
-	while (old_map) {
-		struct map *next = map_groups__next(old_map);
-
-		if (old_map != map)
-			map_groups__remove(kmaps, old_map);
-		old_map = next;
-	}
+	old_mg = *kmaps;
+	kmaps->maps[map->type].entries = RB_ROOT;
 
 	/* Find the kernel map using the first symbol */
 	sym = dso__first_symbol(dso, map->type);
@@ -1223,24 +1217,31 @@ static int dso__load_kcore(struct dso *dso, struct map *map,
 	while (!list_empty(&md.maps)) {
 		new_map = list_entry(md.maps.next, struct map, node);
 		list_del_init(&new_map->node);
-		if (new_map == replacement_map) {
-			map->start	= new_map->start;
-			map->end	= new_map->end;
-			map->pgoff	= new_map->pgoff;
-			map->map_ip	= new_map->map_ip;
-			map->unmap_ip	= new_map->unmap_ip;
-			/* Ensure maps are correctly ordered */
-			map__get(map);
-			map_groups__remove(kmaps, map);
-			map_groups__insert(kmaps, map);
-			map__put(map);
-		} else {
-			map_groups__insert(kmaps, new_map);
+
+		map_groups__insert(kmaps, new_map);
+
+		if (new_map != replacement_map) {
+			old_map = map_groups__find(&old_mg, new_map->type, new_map->start);
+			if (old_map && dso__loaded(old_map->dso, old_map->type)) {
+				new_map->pgoff = old_map->pgoff;
+
+				dso__put(new_map->dso);
+				new_map->dso = dso__get(old_map->dso);
+			}
 		}
 
 		map__put(new_map);
 	}
 
+	/* Remove old maps */
+	old_map = map_groups__first(&old_mg, map->type);
+	while (old_map) {
+		struct map *next = map_groups__next(old_map);
+
+		map_groups__remove(&old_mg, old_map);
+		old_map = next;
+	}
+
 	/*
 	 * Set the data type and long name so that kcore can be read via
 	 * dso__data_read_addr().
-- 
2.13.1