perf buildid-cache: Support --list option

'perf buildid-cache' allows to add/remove files into cache but there is
no option to list all cached files. Add --list option to list all
_valid_ cached files.

Ex,
# perf buildid-cache --add /tmp/a.out
# perf buildid-cache -l
8a86ef73e44067bca52cc3f6cd3e5446c783391c /tmp/a.out

Signed-off-by: Ravi Bangoria <[e-mail]>
Acked-by: Jiri Olsa <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Kate Stewart <[e-mail]>
Cc: Krister Johansen <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Philippe Ombredanne <[e-mail]>
Cc: Sihyeon Jang <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Documentation/perf-buildid-cache.txt

···
 	exactly same build-id, that is replaced by new one. It can be used
 	to update kallsyms and kernel dso to vmlinux in order to support
 	annotation.
-
+-l::
+--list::
+	List all valid binaries from cache.
 -v::
 --verbose::
 	Be more verbose.

tools/perf/builtin-buildid-cache.c

···
 #include "util/session.h"
 #include "util/symbol.h"
 #include "util/time-utils.h"
+#include "util/probe-file.h"
 
 static int build_id_cache__kcore_buildid(const char *proc_dir, char *sbuildid)
 {
···
 	return err;
 }
 
+static int build_id_cache__show_all(void)
+{
+	struct strlist *bidlist;
+	struct str_node *nd;
+	char *buf;
+
+	bidlist = build_id_cache__list_all(true);
+	if (!bidlist) {
+		pr_debug("Failed to get buildids: -%d\n", errno);
+		return -1;
+	}
+	strlist__for_each_entry(nd, bidlist) {
+		buf = build_id_cache__origname(nd->s);
+		fprintf(stdout, "%s %s\n", nd->s, buf);
+		free(buf);
+	}
+	strlist__delete(bidlist);
+	return 0;
+}
+
 int cmd_buildid_cache(int argc, const char **argv)
 {
 	struct strlist *list;
···
 	int ret = 0;
 	int ns_id = -1;
 	bool force = false;
+	bool list_files = false;
+	bool opts_flag = false;
 	char const *add_name_list_str = NULL,
 		   *remove_name_list_str = NULL,
 		   *purge_name_list_str = NULL,
···
 		    "file(s) to remove"),
 	OPT_STRING('p', "purge", &purge_name_list_str, "file list",
 		    "file(s) to remove (remove old caches too)"),
+	OPT_BOOLEAN('l', "list", &list_files, "list all cached files"),
 	OPT_STRING('M', "missing", &missing_filename, "file",
 		   "to find missing build ids in the cache"),
 	OPT_BOOLEAN('f', "force", &force, "don't complain, do it"),
···
 	argc = parse_options(argc, argv, buildid_cache_options,
 			     buildid_cache_usage, 0);
 
-	if (argc || (!add_name_list_str && !kcore_filename &&
-		     !remove_name_list_str && !purge_name_list_str &&
-		     !missing_filename && !update_name_list_str))
+	opts_flag = add_name_list_str || kcore_filename ||
+		remove_name_list_str || purge_name_list_str ||
+		missing_filename || update_name_list_str;
+
+	if (argc || !(list_files || opts_flag))
 		usage_with_options(buildid_cache_usage, buildid_cache_options);
+
+	/* -l is exclusive. It can not be used with other options. */
+	if (list_files && opts_flag) {
+		usage_with_options_msg(buildid_cache_usage,
+			buildid_cache_options, "-l is exclusive.\n");
+	}
 
 	if (ns_id > 0)
 		nsi = nsinfo__new(ns_id);
···
 		goto out;
 
 	setup_pager();
+
+	if (list_files) {
+		ret = build_id_cache__show_all();
+		goto out;
+	}
 
 	if (add_name_list_str) {
 		list = strlist__new(add_name_list_str, NULL);