[RFC PATCH v2 36/37] tools perf: generate event argv.

[Wang Nan <wangnan0@huawei.com>]

bpf_load_gen_argv() generates argc and argv which will be passed to
other commands like cmd_record(). The generated arguments utilized
previous introduced '|' syntax to pass file descriptor of bpf
programs.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
 tools/perf/util/bpf-loader.c | 87 ++++++++++++++++++++++++++++++++++++++++++++
 tools/perf/util/bpf-loader.h |  8 ++++
 2 files changed, 95 insertions(+)

diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
index 7295a3b..a75b0b7 100644
--- a/tools/perf/util/bpf-loader.c
+++ b/tools/perf/util/bpf-loader.c
@@ -215,6 +215,93 @@ int bpf_probe(void)
 	return err < 0 ? err : 0;
 }
 
+int bpf_load_gen_argv(int *pargc, const char ***pargv,
+		      int old_argc, const char **old_argv,
+		      const char *arg0)
+{
+	const char **argv = NULL;
+	int i, argc, pos, err;
+
+	if (!pargc || !pargv)
+		return -EINVAL;
+	if (!old_argv && old_argc)
+		return -EINVAL;
+
+	/*
+	 * <arg0> <new args> <old args> NIL
+	 * Omit the last NIL in argc.
+	 */
+	argc = 1 + params.nr_progs * 2 + old_argc;
+	argv = malloc(sizeof(const char *) * (argc + 1));
+	if (!argv) {
+		pr_err("No enough memory\n");
+		return -ENOMEM;
+	}
+	bzero(argv, sizeof(char *) * (argc + 1));
+
+	pos = 0;
+
+	if (arg0)
+		argv[pos++] = strdup(arg0);
+
+	for (i = 0; i < (int)params.nr_progs; i++) {
+		struct bpf_prog_handler *prog =
+			params.progs[i].prog;
+		struct perf_probe_event *pevent =
+			params.progs[i].pevent;
+		int cmd_size, fd;
+		char *event_str;
+
+		err = bpf_prog_get_fd(prog, &fd);
+		if (err) {
+			pr_err("Unable to get program fd\n");
+			goto errout;
+		}
+
+		cmd_size = snprintf(NULL, 0,
+				"%s:%s|bpf_fd=%d|", pevent->group,
+				pevent->event, fd);
+
+		event_str = malloc(cmd_size + 1);
+		if (!event_str) {
+			pr_err("No enough menory\n");
+			goto errout;
+		}
+
+		snprintf(event_str, cmd_size + 1, "%s:%s|bpf_fd=%d|",
+			 pevent->group, pevent->event, fd);
+
+		argv[pos++] = strdup("-e");
+		if (!argv[pos - 1]) {
+			pr_err("No enough memory\n");
+			goto errout;
+		}
+
+		argv[pos++] = event_str;
+
+		pr_debug("event: -e %s\n", event_str);
+	}
+
+	for (i = 0; i < old_argc; i++) {
+		argv[pos++] = strdup(old_argv[i]);
+		if (!argv[pos - 1]) {
+			pr_err("No enough memory\n");
+			goto errout;
+		}
+	}
+
+	*pargc = pos;
+	*pargv = argv;
+	return 0;
+errout:
+	for (i = 0; (int)i < argc; i++) {
+		if (argv[i])
+			free((void *)argv[i]);
+	}
+	free(argv);
+	return err;
+}
+
 int bpf_load(void)
 {
 	size_t i;
diff --git a/tools/perf/util/bpf-loader.h b/tools/perf/util/bpf-loader.h
index 1ccebdf..eea45f4 100644
--- a/tools/perf/util/bpf-loader.h
+++ b/tools/perf/util/bpf-loader.h
@@ -13,4 +13,12 @@ int bpf_load(void);
 
 int bpf_unprobe(void);
 void bpf_clear(void);
+
+/*
+ * Generates argv like '-e my_event|bpf_fd=5|' for wrapping other
+ * commands.
+ */
+int bpf_load_gen_argv(int *pargc, const char ***pargv,
+		      int old_argc, const char **old_argv,
+		      const char *arg0);
 #endif
-- 
1.8.3.4