tests: arch: arm: interrupt: add test-case for user mode IRQ locking

We add a simple test to cover the case of invoking
IRQ lock()/unlock() from ARM Cortex-M user mode.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>

tests/arch/arm/arm_interrupt/README.txt

@@ -1,11 +1,17 @@
-Title: Test to verify code fault handling in ISR execution context (ARM Only)
+Title: Test to verify code fault handling in ISR execution context
+       and the behavior of irq_lock() and irq_unlock() when invoked
+       from User Mode. (ARM Only)
 
 Description:
 
-This test verifies that we can handle system fault conditions
+The first test verifies that we can handle system fault conditions
 while running in handler mode (i.e. in an ISR). Only for ARM
 Cortex-M targets.
 
+The second test verifies that threads in user mode, despite being able to call
+the irq_lock() and irq_unlock() functions without triggering a CPU fault,
+they won't be able to read or modify the current IRQ locking status.
+
 ---------------------------------------------------------------------------
 
 Building and Running Project:
@@ -62,6 +68,13 @@ Sample Output:
 
  PASS - test_arm_interrupt
  ===================================================================
+ starting test - test_arm_user_interrupt
+ PASS - test_arm_user_interrupt
+ ===================================================================
+ Test suite arm_interrupt succeeded
+ ===================================================================
+ PROJECT EXECUTION SUCCESSFUL
+
  Test suite arm_interrupt succeeded
  ===================================================================
  PROJECT EXECUTION SUCCESSFUL

tests/arch/arm/arm_interrupt/prj.conf

@@ -1,2 +1,4 @@
 CONFIG_ZTEST=y
 CONFIG_DYNAMIC_INTERRUPTS=y
+CONFIG_TEST_USERSPACE=y
+CONFIG_APPLICATION_DEFINED_SYSCALL=y

tests/arch/arm/arm_interrupt/src/arm_interrupt.c

@@ -114,6 +114,86 @@ void test_arm_interrupt(void)
 		zassert_true(post_flag == j, "Test flag not set by ISR\n");
 	}
 }
+
+#if defined(CONFIG_USERSPACE)
+#include <syscall_handler.h>
+#include "test_syscalls.h"
+
+void z_impl_test_arm_user_interrupt_syscall(void)
+{
+#if defined(CONFIG_ARMV6_M_ARMV8_M_BASELINE)
+	/* Confirm IRQs are not locked */
+	zassert_false(__get_PRIMASK(), "PRIMASK is set\n");
+#elif defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
+
+	static bool first_call = 1;
+
+	if (first_call == 1) {
+
+		/* First time the syscall is invoked */
+		first_call = 0;
+
+		/* Lock IRQs in supervisor mode */
+		int key = irq_lock();
+
+		/* Verify that IRQs were not already locked */
+		zassert_false(key, "IRQs locked in system call\n");
+	}
+
+	/* Confirm IRQs are still locked */
+	zassert_true(__get_BASEPRI(), "BASEPRI not set\n");
+#endif
+}
+
+static inline void z_vrfy_test_arm_user_interrupt_syscall(void)
+{
+	z_impl_test_arm_user_interrupt_syscall();
+}
+#include <syscalls/test_arm_user_interrupt_syscall_mrsh.c>
+
+void test_arm_user_interrupt(void)
+{
+	/* Test thread executing in user mode */
+	zassert_true(arch_is_user_context(),
+		"Test thread not running in user mode\n");
+
+	/* Attempt to lock IRQs in user mode */
+	irq_lock();
+	/* Attempt to lock again should return non-zero value of previous
+	 * locking attempt, if that were to be successful.
+	 */
+	int lock = irq_lock();
+
+	zassert_false(lock, "IRQs shown locked in user mode\n");
+
+	/* Generate a system call to manage the IRQ locking */
+	test_arm_user_interrupt_syscall();
+
+	/* Attempt to unlock IRQs in user mode */
+	irq_unlock(0);
+
+#if defined(CONFIG_ARMV7_M_ARMV8_M_MAINLINE)
+	/* The first system call has left the IRQs locked.
+	 * Generate a second system call to inspect the IRQ locking.
+	 *
+	 * In Cortex-M Baseline system calls cannot be invoked
+	 * with interrupts locked, so we skip this part of the
+	 * test.
+	 */
+	test_arm_user_interrupt_syscall();
+
+	/* Verify that thread is not able to infer that IRQs are locked. */
+	zassert_false(irq_lock(), "IRQs are shown to be locked\n");
+#endif
+}
+#else
+void test_arm_user_interrupt(void)
+{
+	TC_PRINT("Skipped\n");
+}
+#endif /* CONFIG_USERSPACE */
+
+
 /**
  * @}
  */

tests/arch/arm/arm_interrupt/src/main.c

@@ -7,10 +7,12 @@
 #include <ztest.h>
 
 extern void test_arm_interrupt(void);
+extern void test_arm_user_interrupt(void);
 
 void test_main(void)
 {
 	ztest_test_suite(arm_interrupt,
-		ztest_unit_test(test_arm_interrupt));
+		ztest_unit_test(test_arm_interrupt),
+		ztest_user_unit_test(test_arm_user_interrupt));
 	ztest_run_test_suite(arm_interrupt);
 }

tests/arch/arm/arm_interrupt/src/test_syscalls.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2017 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef _TEST_SYSCALLS_H_
+#define _TEST_SYSCALLS_H_
+#include <zephyr.h>
+
+__syscall void test_arm_user_interrupt_syscall(void);
+
+#include <syscalls/test_syscalls.h>
+
+#endif /* _TEST_SYSCALLS_H_ */