Add a fibonacci test to cause context switches

The test creates tasks that pause until the children task have finished.
The value of the perf_event_paranoid file is checked to determine if we
can run the test.

cmake/CheckPerfParanoid.cmake

@@ -0,0 +1,20 @@
+# Copyright (c) 2024 Barcelona Supercomputing Center (BSC)
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+if(EXISTS "/proc/sys/kernel/perf_event_paranoid")
+  file(READ "/proc/sys/kernel/perf_event_paranoid" paranoid_raw)
+
+  string(REPLACE "\n" "" paranoid_value "${paranoid_raw}")
+  message(STATUS "Value of /proc/sys/kernel/perf_event_paranoid is ${paranoid_value}")
+
+  if(paranoid_value LESS_EQUAL 1)
+    message(STATUS "Value of perf_event_paranoid suitable for Kernel tests")
+    set(PERF_PARANOID_KERNEL ON)
+  else()
+    message(STATUS "Value of perf_event_paranoid NOT suitable for Kernel tests")
+    set(PERF_PARANOID_KERNEL OFF)
+  endif()
+else()
+  message(STATUS "Missing /proc/sys/kernel/perf_event_paranoid")
+  set(PERF_PARANOID_KERNEL OFF)
+endif()

test/rt/nodes/CMakeLists.txt

@@ -56,3 +56,14 @@ nodes_rt_test(../nanos6/if0.c NAME if0 SORT)
 nodes_rt_test(../nanos6/sched-add.c NAME sched-add SORT)
 nodes_rt_test(../nanos6/taskloop.c NAME taskloop SORT)
 nodes_rt_test(taskiter.c SORT)
+
+
+include(CheckPerfParanoid)
+if (PERF_PARANOID_KERNEL)
+  message(STATUS "Enabling perf paranoid tests for NODES")
+  nodes_rt_test(fibonacci.c SORT LEVEL 3)
+elseif(ENABLE_ALL_TESTS)
+  message(FATAL_ERROR "Cannot enable perf paranoid tests for NODES")
+else()
+  message(STATUS "Disabling perf paranoid tests for NODES")
+endif()

test/rt/nodes/fibonacci.c

@@ -0,0 +1,61 @@
+/* Copyright (c) 2024 Barcelona Supercomputing Center (BSC)
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "common.h"
+#include "compat.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+static long
+fib(long index)
+{
+	long a, b;
+	if (index <= 1)
+		return index;
+	#pragma oss task shared(a) label("fibonacci")
+	a = fib(index-1);
+	#pragma oss task shared(b) label("fibonacci")
+	b = fib(index-2);
+	#pragma oss taskwait
+	return a + b;
+}
+
+int
+main(void)
+{
+	FILE *f = fopen("/proc/sys/kernel/perf_event_paranoid", "r");
+	if (f == NULL)
+		die("cannot open /proc/sys/kernel/perf_event_paranoid:");
+
+	char buf[16] = {0};
+	if (fread(buf, 1, 16, f) <= 0)
+		die("cannot read /proc/sys/kernel/perf_event_paranoid:");
+
+	fclose(f);
+
+	/* We need the value 1 or less:
+	 * Access to performance monitoring and observability operations is limited.
+	 * Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open
+	 * access to performance monitoring and observability operations for processes
+	 * without CAP_PERFMON, CAP_SYS_PTRACE or CAP_SYS_ADMIN Linux capability.
+	 * More information can be found at 'Perf events and tool security' document:
+	 * https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html
+	 * perf_event_paranoid setting is 3:
+	 *   -1: Allow use of (almost) all events by all users
+	 *       Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK
+	 * >= 0: Disallow raw and ftrace function tracepoint access
+	 * >= 1: Disallow CPU event access
+	 * >= 2: Disallow kernel profiling
+	 * To make the adjusted perf_event_paranoid setting permanent preserve it
+	 * in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = <setting>)
+	 */
+	int level = atoi(buf);
+	if (level > 1)
+		die("requires perf_event_paranoid = 1 or less");
+
+	for (int i = 0; i < 30; i++)
+		fib(5);
+
+	#pragma oss taskwait
+	return 0;
+}