[PATCH 1/2] perf:tools: avoid to create much more maps for kernel symbols on ARM

[tom.leiming@gmail.com]

From: Ming Lei <tom.leiming@gmail.com>

On ARM, module addresss space is ahead of kernel space,
so the module symbols are handled before kernel symbol
in dso__split_kallsyms, then cause one map is created
for each kernel symbol.

This patch fixes the issue by restoring to original kernel
map in dso__split_kallsyms() to avoid create unnecessary maps
for kernel symbols when starting to handle kenel symbol maps
but after module symbol maps are handled over.

Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom Zanussi <tzanussi@gmail.com>
Signed-off-by: Ming Lei <tom.leiming@gmail.com>
---
 tools/perf/util/symbol.c |   58 ++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 58 insertions(+), 0 deletions(-)

diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c
index 0500895..c5b4ccb 100644
--- a/tools/perf/util/symbol.c
+++ b/tools/perf/util/symbol.c
@@ -520,6 +520,53 @@ static int dso__load_all_kallsyms(struct dso *self, const char *filename,
 	return kallsyms__parse(filename, &args, map__process_kallsym_symbol);
 }
 
+static int map_for_module(struct map *map, struct machine *self)
+{
+	char *line = NULL;
+	FILE *file;
+	const char *modules;
+	char name[PATH_MAX];
+	int ret = 0;
+
+	if (machine__is_default_guest(self))
+		modules = symbol_conf.default_guest_modules;
+	else {
+		sprintf(name, "%s/proc/modules", self->root_dir);
+		modules = name;
+	}
+
+	file = fopen(modules, "r");
+	if (file == NULL)
+		return ret;
+
+	/*strip [] of map->dso->short_name*/
+	strncpy(name, map->dso->short_name + 1,
+			strlen(map->dso->short_name) - 2);
+	name[strlen(map->dso->short_name) - 3] = '\0';
+
+	while (!feof(file)) {
+		int line_len;
+		size_t n;
+
+		line_len = getline(&line, &n, file);
+		if (line_len < 0)
+			break;
+
+		if (!line)
+			break;
+
+		line[line_len-1] = '\0'; /* \n */
+
+		if (strstr(line, name)) {
+			ret = 1;
+			break;
+		}
+	}
+
+	free(line);
+	fclose(file);
+	return ret;
+}
 /*
  * Split the symbols into maps, making sure there are no overlaps, i.e. the
  * kernel range is broken in several maps, named [kernel].N, as we don't have
@@ -590,6 +637,16 @@ static int dso__split_kallsyms(struct dso *self, struct map *map,
 			char dso_name[PATH_MAX];
 			struct dso *dso;
 
+			/*
+			 * If module symbol is ahead of kernel symbol like ARM,
+			 * restore to original kernel map to avoid create many
+			 * unnecessary maps for kernel symbols.
+			 */
+			if (map_for_module(curr_map, machine)) {
+				curr_map = map;
+				goto operate_map;
+			}
+
 			if (self->kernel == DSO_TYPE_GUEST_KERNEL)
 				snprintf(dso_name, sizeof(dso_name),
 					"[guest.kernel].%d",
@@ -616,6 +673,7 @@ static int dso__split_kallsyms(struct dso *self, struct map *map,
 			++kernel_range;
 		}
 
+operate_map:
 		if (filter && filter(curr_map, pos)) {
 discard_symbol:		rb_erase(&pos->rb_node, root);
 			symbol__delete(pos);
-- 
1.7.3