perf ftrace: Use CAP_SYS_ADMIN instead of euid==0

The kernel requires CAP_SYS_ADMIN instead of euid==0 to mount debugfs
for ftrace.  Make perf do the same.

Signed-off-by: Igor Lubashev <ilubashe@akamai.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/bd8763b72ed4d58d0b42d44fbc7eb474d32e53a3.1565188228.git.ilubashe@akamai.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-ftrace.c

@@ -13,6 +13,7 @@
 #include <signal.h>
 #include <fcntl.h>
 #include <poll.h>
+#include <linux/capability.h>
 
 #include "debug.h"
 #include <subcmd/parse-options.h>
@@ -21,6 +22,7 @@
 #include "target.h"
 #include "cpumap.h"
 #include "thread_map.h"
+#include "util/cap.h"
 #include "util/config.h"
 
 
@@ -281,7 +283,7 @@ static int __cmd_ftrace(struct perf_ftrace *ftrace, int argc, const char **argv)
 		.events = POLLIN,
 	};
 
-	if (geteuid() != 0) {
+	if (!perf_cap__capable(CAP_SYS_ADMIN)) {
 		pr_err("ftrace only works for root!\n");
 		return -1;
 	}