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>

6 files changed, 130 insertions, 0 deletions

diff --git a/tools/perf/Build b/tools/perf/Build
index 5f392dbb88fc..db61dbe2b543 100644
--- a/tools/perf/Build
+++ b/tools/perf/Build
@@ -24,6 +24,7 @@ perf-y += builtin-mem.o
 perf-y += builtin-data.o
 perf-y += builtin-version.o
 perf-y += builtin-c2c.o
+perf-y += builtin-daemon.o
 
 perf-$(CONFIG_TRACE) += builtin-trace.o
 perf-$(CONFIG_LIBELF) += builtin-probe.o
diff --git a/tools/perf/Documentation/perf-daemon.txt b/tools/perf/Documentation/perf-daemon.txt
new file mode 100644
index 000000000000..d05b8dab0a6a
--- /dev/null
+++ b/tools/perf/Documentation/perf-daemon.txt
@@ -0,0 +1,40 @@
+perf-daemon(1)
+==============
+
+
+NAME
+----
+perf-daemon - Run record sessions on background
+
+
+SYNOPSIS
+--------
+[verse]
+'perf daemon'
+'perf daemon' [<options>]
+'perf daemon start'  [<options>]
+
+
+DESCRIPTION
+-----------
+This command allows to run simple daemon process that starts and
+monitors configured record sessions.
+
+
+OPTIONS
+-------
+-v::
+--verbose::
+	Be more verbose.
+
+All generic options are available also under commands.
+
+
+START COMMAND
+-------------
+The start command creates the daemon process.
+
+
+SEE ALSO
+--------
+linkperf:perf-record[1], linkperf:perf-config[1]
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;
+}
diff --git a/tools/perf/builtin.h b/tools/perf/builtin.h
index 14a2db622a7b..7303e80a639c 100644
--- a/tools/perf/builtin.h
+++ b/tools/perf/builtin.h
@@ -37,6 +37,7 @@ int cmd_inject(int argc, const char **argv);
 int cmd_mem(int argc, const char **argv);
 int cmd_data(int argc, const char **argv);
 int cmd_ftrace(int argc, const char **argv);
+int cmd_daemon(int argc, const char **argv);
 
 int find_scripts(char **scripts_array, char **scripts_path_array, int num,
 		 int pathlen);
diff --git a/tools/perf/command-list.txt b/tools/perf/command-list.txt
index bc6c585f74fc..825a12e8d694 100644
--- a/tools/perf/command-list.txt
+++ b/tools/perf/command-list.txt
@@ -31,3 +31,4 @@ perf-timechart			mainporcelain common
 perf-top			mainporcelain common
 perf-trace			mainporcelain audit
 perf-version			mainporcelain common
+perf-daemon			mainporcelain common
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 27f94b0bb874..20cb91ef06ff 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -88,6 +88,7 @@ static struct cmd_struct commands[] = {
 	{ "mem",	cmd_mem,	0 },
 	{ "data",	cmd_data,	0 },
 	{ "ftrace",	cmd_ftrace,	0 },
+	{ "daemon",	cmd_daemon,	0 },
 };
 
 struct pager_config {