perf symbols: Allow lookups by symbol name too

Configurable via symbol_conf.sort_by_name, so that the cost of an
extra rb_node on all 'struct symbol' instances is not paid by tools
that only want to decode addresses.

How to use it:

	symbol_conf.sort_by_name = true;
	symbol_init(&symbol_conf);

	struct map *map = map_groups__find_by_name(kmaps, MAP__VARIABLE, "[kernel.kallsyms]");

	if (map == NULL) {
		pr_err("couldn't find map!\n");
		kernel_maps__fprintf(stdout);
	} else {
		struct symbol *sym = map__find_symbol_by_name(map, sym_filter, NULL);
		if (sym == NULL)
			pr_err("couldn't find symbol %s!\n", sym_filter);
		else
			pr_info("symbol %s: %#Lx-%#Lx \n", sym_filter, sym->start, sym->end);
	}

Looking over the vmlinux/kallsyms is common enough that I'll add a
variable to the upcoming struct perf_session to avoid the need to
use map_groups__find_by_name to get the main vmlinux/kallsyms map.

The above example looks on the 'variable' symtab, but it is just
like that for the functions one.

Also the sort operation is done when we first use
map__find_symbol_by_name, in a lazy way.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <1260564622-12392-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 53 insertions, 32 deletions

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 69f94fe9db2..175f1f6b691 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -104,45 +104,66 @@ void map__fixup_end(struct map *self)
 
 #define DSO__DELETED "(deleted)"
 
-struct symbol *map__find_symbol(struct map *self, u64 addr,
-                                symbol_filter_t filter)
+static int map__load(struct map *self, symbol_filter_t filter)
 {
-        if (!dso__loaded(self->dso, self->type)) {
-                int nr = dso__load(self->dso, self, filter);
-
-                if (nr < 0) {
-                        if (self->dso->has_build_id) {
-                                char sbuild_id[BUILD_ID_SIZE * 2 + 1];
-
-                                build_id__sprintf(self->dso->build_id,
-                                                  sizeof(self->dso->build_id),
-                                                  sbuild_id);
-                                pr_warning("%s with build id %s not found",
-                                           self->dso->long_name, sbuild_id);
-                        } else
-                                pr_warning("Failed to open %s",
-                                           self->dso->long_name);
-                        pr_warning(", continuing without symbols\n");
-                        return NULL;
-                } else if (nr == 0) {
-                        const char *name = self->dso->long_name;
-                        const size_t len = strlen(name);
-                        const size_t real_len = len - sizeof(DSO__DELETED);
-
-                        if (len > sizeof(DSO__DELETED) &&
-                            strcmp(name + real_len + 1, DSO__DELETED) == 0) {
-                                pr_warning("%.*s was updated, restart the long running apps that use it!\n",
-                                           (int)real_len, name);
-                        } else {
-                                pr_warning("no symbols found in %s, maybe install a debug package?\n", name);
-                        }
-                        return NULL;
+        const char *name = self->dso->long_name;
+        int nr = dso__load(self->dso, self, filter);
+
+        if (nr < 0) {
+                if (self->dso->has_build_id) {
+                        char sbuild_id[BUILD_ID_SIZE * 2 + 1];
+
+                        build_id__sprintf(self->dso->build_id,
+                                          sizeof(self->dso->build_id),
+                                          sbuild_id);
+                        pr_warning("%s with build id %s not found",
+                                   name, sbuild_id);
+                } else
+                        pr_warning("Failed to open %s", name);
+
+                pr_warning(", continuing without symbols\n");
+                return -1;
+        } else if (nr == 0) {
+                const size_t len = strlen(name);
+                const size_t real_len = len - sizeof(DSO__DELETED);
+
+                if (len > sizeof(DSO__DELETED) &&
+                    strcmp(name + real_len + 1, DSO__DELETED) == 0) {
+                        pr_warning("%.*s was updated, restart the long "
+                                   "running apps that use it!\n",
+                                   (int)real_len, name);
+                } else {
+                        pr_warning("no symbols found in %s, maybe install "
+                                   "a debug package?\n", name);
                 }
+
+                return -1;
         }
 
+        return 0;
+}
+
+struct symbol *map__find_symbol(struct map *self, u64 addr,
+                                symbol_filter_t filter)
+{
+        if (!dso__loaded(self->dso, self->type) && map__load(self, filter) < 0)
+                return NULL;
+
         return self->dso->find_symbol(self->dso, self->type, addr);
 }
 
+struct symbol *map__find_symbol_by_name(struct map *self, const char *name,
+                                        symbol_filter_t filter)
+{
+        if (!dso__loaded(self->dso, self->type) && map__load(self, filter) < 0)
+                return NULL;
+
+        if (!dso__sorted_by_name(self->dso, self->type))
+                dso__sort_by_name(self->dso, self->type);
+
+        return dso__find_symbol_by_name(self->dso, self->type, name);
+}
+
 struct map *map__clone(struct map *self)
 {
         struct map *map = malloc(sizeof(*self));