perf daemon: Add base option

Add a base option allowing the user to specify a base directory.  It
will have precedence over config file base definition coming in the
following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexei Budankov <abudankov@huawei.com>
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/20210208200908.1019149-4-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-daemon.txt

@@ -31,6 +31,10 @@ OPTIONS
 	Config file path. If not provided, perf will check system and default
 	locations (/etc/perfconfig, $HOME/.perfconfig).
 
+--base=<PATH>::
+	Base directory path. Each daemon instance is running on top
+	of base directory.
+
 All generic options are available also under commands.
 
 

tools/perf/builtin-daemon.c

@@ -6,6 +6,7 @@
 #include <stdlib.h>
 #include <stdio.h>
 #include <unistd.h>
+#include <errno.h>
 #include "builtin.h"
 #include "perf.h"
 #include "debug.h"
@@ -15,6 +16,7 @@
 struct daemon {
 	const char		*config;
 	char			*config_real;
+	const char		*base_user;
 	char			*base;
 	FILE			*out;
 	char			 perf[PATH_MAX];
@@ -38,10 +40,17 @@ static void sig_handler(int sig __maybe_unused)
 static void daemon__exit(struct daemon *daemon)
 {
 	free(daemon->config_real);
+	free(daemon->base);
 }
 
 static int setup_config(struct daemon *daemon)
 {
+	if (daemon->base_user) {
+		daemon->base = strdup(daemon->base_user);
+		if (!daemon->base)
+			return -ENOMEM;
+	}
+
 	if (daemon->config) {
 		char *real = realpath(daemon->config, NULL);
 
@@ -104,6 +113,8 @@ int cmd_daemon(int argc, const char **argv)
 		OPT_INCR('v', "verbose", &verbose, "be more verbose"),
 		OPT_STRING(0, "config", &__daemon.config,
 			"config file", "config file path"),
+		OPT_STRING(0, "base", &__daemon.base_user,
+			"directory", "base directory"),
 		OPT_END()
 	};