samples: Add mpu stack guard test

This patch adds the mpu_stack_guard_test to the available samples.
The purpose of this test is to exercize the thread stack guard enabled
via MPU on arm platforms.

Change-Id: I4665a20956d9e6d0dd4b5cc862e82040a53afafc
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@linaro.org>

samples/mpu_stack_guard_test/Makefile

@@ -0,0 +1,4 @@
+BOARD ?= v2m_beetle
+CONF_FILE = prj.conf
+
+include ${ZEPHYR_BASE}/Makefile.test

samples/mpu_stack_guard_test/README.rst

@@ -0,0 +1,67 @@
+.. _mpu_stack_guard_test:
+
+MPU Stack Guard Test
+####################
+
+Overview
+********
+
+This is a simple application that demonstrates basic thread stack guarding on
+the supported platforms.
+A thread spawned by the main task recursively calls a function that fills the
+thread stack up to where it overwrites a preposed canary.
+If the MPU is enabled and the Stack Guard feature is present the test succeeds
+because an MEM Faults exception prevents the canary from being overwritten.
+If the MPU is disabled the test fails because the canary is overwritten.
+
+Building and Running
+********************
+
+This project outputs to the console.
+To build the test with the MPU disabled:
+
+.. code-block:: console
+
+   $ cd samples/mpu_stack_guard_test
+   $ make
+
+To build the test with the MPU enabled and the stack guard feature present:
+
+.. code-block:: console
+
+   $ cd samples/mpu_stack_guard_test
+   $ make CONF_FILE=prj_stack_guard.conf
+
+Sample Output
+=============
+
+With the MPU disabled:
+
+.. code-block:: console
+
+   ***** BOOTING ZEPHYR OS v1.7.99 - BUILD: Mar 29 2017 11:07:09 *****
+   MPU STACK GUARD Test
+   Canary Initial Value = 0xf0cacc1a
+   Canary = 0x200003a8     Test not passed.
+   ...
+
+With the MPU enabled and the stack guard feature present:
+
+.. code-block:: console
+
+   ***** BOOTING ZEPHYR OS v1.7.99 - BUILD: Mar 29 2017 11:20:10 *****
+   MPU STACK GUARD Test
+   Canary Initial Value = 0xf0cacc1a
+   [general] [DBG] arm_core_mpu_configure: Region info: 0x200003ac 0x400
+   ***** MPU FAULT *****
+     Executing thread ID (thread): 0x200003ac
+     Faulting instruction address:  0x0
+     Stacking error
+   Fatal fault in thread 0x200003ac! Aborting.
+   ***** HARD FAULT *****
+     Fault escalation (see below)
+   ***** MPU FAULT *****
+     Executing thread ID (thread): 0x200003ac
+     Faulting instruction address:  0x8000466
+     Stacking error
+   Fatal fault in ISR! Spinning...

samples/mpu_stack_guard_test/prj.conf

@@ -0,0 +1 @@
+CONFIG_STDOUT_CONSOLE=y

samples/mpu_stack_guard_test/prj_stack_guard.conf

@@ -0,0 +1,5 @@
+CONFIG_STDOUT_CONSOLE=y
+CONFIG_MPU_STACK_GUARD=y
+CONFIG_SYS_LOG=y
+CONFIG_SYS_LOG_DEFAULT_LEVEL=4
+CONFIG_SYS_LOG_OVERRIDE_LEVEL=4

samples/mpu_stack_guard_test/src/Makefile

@@ -0,0 +1 @@
+obj-y = main.o

samples/mpu_stack_guard_test/src/main.c

@@ -0,0 +1,70 @@
+/* main.c - Hello World demo */
+
+/*
+ * Copyright (c) 2012-2014 Wind River Systems, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <misc/printk.h>
+
+/* size of stack area used by each thread */
+#define STACKSIZE 1024
+
+/* scheduling priority used by each thread */
+#define PRIORITY 7
+
+/* delay between greetings (in ms) */
+#define SLEEPTIME 500
+
+/* Focaccia tastes better than DEEDBEEF ;-) */
+#define STACK_GUARD_CANARY 0xF0CACC1A
+
+struct stack_guard_buffer {
+	/* Make sure canary is not optimized by the compiler */
+	volatile u32_t canary;
+	u8_t stack[STACKSIZE];
+};
+
+struct stack_guard_buffer buf;
+
+u32_t recursive_loop(u32_t counter)
+{
+	if (buf.canary != STACK_GUARD_CANARY) {
+		printk("Canary = 0x%08x\tTest not passed.\n", buf.canary);
+
+		while (1) {
+			k_sleep(SLEEPTIME);
+		}
+	}
+
+	counter++;
+
+	return recursive_loop(counter) + recursive_loop(counter);
+}
+
+/* stack_guard_thread is a dynamic thread */
+void stack_guard_thread(void *dummy1, void *dummy2, void *dummy3)
+{
+	ARG_UNUSED(dummy1);
+	ARG_UNUSED(dummy2);
+	ARG_UNUSED(dummy3);
+
+	u32_t result = recursive_loop(0);
+
+	/* We will never arrive here */
+	printk("Result: %d", result);
+}
+
+void main(void)
+{
+	buf.canary = STACK_GUARD_CANARY;
+
+	printk("MPU STACK GUARD Test\n");
+	printk("Canary Initial Value = 0x%x\n", buf.canary);
+
+	/* spawn stack_guard_thread */
+	k_thread_spawn(buf.stack, STACKSIZE, stack_guard_thread, NULL, NULL,
+		       NULL, PRIORITY, 0, K_NO_WAIT);
+}

samples/mpu_stack_guard_test/testcase.ini

@@ -0,0 +1,10 @@
+[test]
+build_only = true
+tags = apps
+
+[test_stack_guard]
+build_only = true
+extra_args = CONF_FILE=prj_stack_guard.conf
+tags = apps
+arch_whitelist = arm
+filter = CONFIG_MPU_STACK_GUARD and CONFIG_ARM_MPU

samples/samples.rst

@@ -12,6 +12,7 @@ Samples and Demos
    basic/*
    subsys/subsys.rst
    mpu_test/*
+   mpu_stack_guard_test/*
    net/net.rst
    bluetooth/bluetooth.rst
    sensor/*