[RFC PATCH v2 28/37] tools perf: add 'perf bpf record' subcommand.

[Wang Nan <wangnan0@huawei.com>]

'perf bpf record' will be implemented to load eBPF object file then
start recording on events defined in it. This patch only adds a
'--object' option for selecting object file. Other arguments are
directly passed to cmd_record.

Example:

 # perf bpf --object obj1.o --object obj2.o -- -a command-to-record

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
 tools/perf/builtin-bpf.c | 111 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 109 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-bpf.c b/tools/perf/builtin-bpf.c
index a8858e2..b5c613f 100644
--- a/tools/perf/builtin-bpf.c
+++ b/tools/perf/builtin-bpf.c
@@ -48,14 +48,121 @@ static void print_usage(void)
 	exit(129);
 }
 
-static const char * const bpf_subcommands[] = { NULL };
+static const char * const bpf_record_usage[] = {
+	"perf bpf record [<options>] -- [options passed to record]",
+	NULL
+};
+
+struct param {
+	struct strlist *object_file_names;
+} param;
+
+static int add_bpf_object_file(const struct option *opt,
+			       const char *str,
+			       int unset __maybe_unused)
+{
+	struct strlist **filenames = (struct strlist **)opt->value;
+
+	if (!*filenames)
+		*filenames = strlist__new(true, NULL);
+
+	if (!*filenames) {
+		pr_err("alloc strlist failed\n");
+		return -ENOMEM;
+	}
+
+	strlist__add(*filenames, str);
+	return 0;
+}
+
+static int start_bpf_record(int argc, const char **argv)
+{
+	int i, new_argc, err, pos = 0;
+	const char **new_argv;
+
+	new_argc = argc + 1;
+	new_argv = malloc((new_argc + 1) * sizeof(const char *));
+	if (!new_argv) {
+		pr_err("malloc failed\n");
+		return -ENOMEM;
+	}
+	bzero(new_argv, sizeof(const char *) * (new_argc + 1));
+
+	new_argv[pos++] = strdup("bpf record --");
+
+	for (i = 0; i < argc; i++) {
+		new_argv[pos++] = strdup(argv[i]);
+		if (!new_argv[pos - 1]) {
+			pr_err("strdup failed\n");
+			err = -ENOMEM;
+			goto errout;
+		}
+	}
+
+	return cmd_record(new_argc, new_argv, NULL);
+
+errout:
+	if (new_argv) {
+		for (i = 0; i < pos; i++)
+			free((void *)new_argv[i]);
+		free(new_argv);
+	}
+	return err;
+}
+
+static int cmd_bpf_record(int argc, const char **argv,
+			    const char *prefix __maybe_unused)
+{
+	/*
+	 * Options in perf-record may be mirrored here. This command
+	 * should add '-e' options to cmd_record.
+	 */
+	static const struct option options[] = {
+		OPT_CALLBACK(0, "object", &param.object_file_names,
+			     "file", "eBPF object file name",
+			     add_bpf_object_file),
+		OPT_END()
+	};
+	struct str_node *str_node;
+
+	argc = parse_options(argc, argv, options,
+			     bpf_record_usage, PARSE_OPT_KEEP_DASHDASH);
+
+	if (!param.object_file_names) {
+		pr_err("At least one '--object' option is needed to "
+		       "select an eBPF object file\n");
+		goto usage;
+	}
+
+	if (!argv || strcmp(argv[0], "--")) {
+		pr_err("Should use '--' to pass options to perf "
+		       "record\n");
+		goto usage;
+	}
+
+	/* skip "--" */
+	argc--;
+	argv++;
+
+	strlist__for_each(str_node, param.object_file_names)
+		pr_debug("loading %s\n", str_node->s);
+
+	return start_bpf_record(argc, argv);
+usage:
+	usage_with_options(bpf_record_usage, options);
+	return -1;
+}
+
+
+static const char * const bpf_subcommands[] = { "record", NULL };
 
 static struct bpf_cmd bpf_cmds[] = {
+	{ "record", "load eBPF program into kernel then start record on events in it", cmd_bpf_record },
 	{ .name = NULL, },
 };
 
 int cmd_bpf(int argc, const char **argv,
-	    const char *prefix __maybe_unused)
+	    const char *prefix)
 {
 	struct bpf_cmd *cmd;
 	const char *cmdstr;
-- 
1.8.3.4