perf daemon: Add daemon command

Add a daemon skeleton with a minimal base (non) functionality, covering
various setup in start command.

Add an initial perf-daemon.txt with basic info.

This is in response to pople asking for the possibility to be able run
record long running sessions on the background.

The patchset that starts with this adds support to configure and run
record sessions on background via new 'perf daemon' command.

This is useful for being able to use perf as a flight recorder that one
can interact with asking for events to be enabled or disabled, added or
removed, etc.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/20210208200908.1019149-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 86 insertions, 0 deletions

diff --git a/tools/perf/builtin-daemon.c b/tools/perf/builtin-daemon.c
new file mode 100644
index 000000000000..8b13e455ac40
--- /dev/null
+++ b/tools/perf/builtin-daemon.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <subcmd/parse-options.h>
+#include <linux/limits.h>
+#include <string.h>
+#include <signal.h>
+#include <stdio.h>
+#include <unistd.h>
+#include "builtin.h"
+#include "perf.h"
+#include "debug.h"
+#include "util.h"
+
+struct daemon {
+	char			*base;
+	FILE			*out;
+	char			 perf[PATH_MAX];
+};
+
+static struct daemon __daemon = { };
+
+static const char * const daemon_usage[] = {
+	"perf daemon start [<options>]",
+	"perf daemon [<options>]",
+	NULL
+};
+
+static bool done;
+
+static void sig_handler(int sig __maybe_unused)
+{
+	done = true;
+}
+
+static int __cmd_start(struct daemon *daemon, struct option parent_options[],
+		       int argc, const char **argv)
+{
+	struct option start_options[] = {
+		OPT_PARENT(parent_options),
+		OPT_END()
+	};
+	int err = 0;
+
+	argc = parse_options(argc, argv, start_options, daemon_usage, 0);
+	if (argc)
+		usage_with_options(daemon_usage, start_options);
+
+	debug_set_file(daemon->out);
+	debug_set_display_time(true);
+
+	pr_info("daemon started (pid %d)\n", getpid());
+
+	signal(SIGINT, sig_handler);
+	signal(SIGTERM, sig_handler);
+
+	while (!done && !err) {
+		sleep(1);
+	}
+
+	pr_info("daemon exited\n");
+	fclose(daemon->out);
+	return err;
+}
+
+int cmd_daemon(int argc, const char **argv)
+{
+	struct option daemon_options[] = {
+		OPT_INCR('v', "verbose", &verbose, "be more verbose"),
+		OPT_END()
+	};
+
+	perf_exe(__daemon.perf, sizeof(__daemon.perf));
+	__daemon.out = stdout;
+
+	argc = parse_options(argc, argv, daemon_options, daemon_usage,
+			     PARSE_OPT_STOP_AT_NON_OPTION);
+
+	if (argc) {
+		if (!strcmp(argv[0], "start"))
+			return __cmd_start(&__daemon, daemon_options, argc, argv);
+
+		pr_err("failed: unknown command '%s'\n", argv[0]);
+		return -1;
+	}
+
+	return -1;
+}