tests: riscv: test PMP stack guards

Test if PMP protected regions prevents write access.

Signed-off-by: Volodymyr Fialko <vfialko@marvell.com>

tests/arch/riscv/pmp/no-multithreading/CMakeLists.txt

@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(riscv_pmp)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})
+
+target_include_directories(app PRIVATE
+  ${ZEPHYR_BASE}/kernel/include
+  ${ZEPHYR_BASE}/arch/${ARCH}/include
+  )

tests/arch/riscv/pmp/no-multithreading/prj.conf

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+CONFIG_ZTEST=y
+CONFIG_MULTITHREADING=n

tests/arch/riscv/pmp/no-multithreading/src/main.c

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+/*
+ * Copyright (c) 2024 Marvell.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel_internal.h>
+#include <zephyr/tc_util.h>
+#include <zephyr/ztest.h>
+
+static volatile ZTEST_BMEM bool valid_fault;
+
+void k_sys_fatal_error_handler(unsigned int reason, const struct arch_esf *pEsf)
+{
+	int rv = TC_PASS;
+
+	TC_PRINT("Caught system error -- reason %d %d\n", reason, valid_fault);
+	if (!valid_fault) {
+		TC_PRINT("Fatal error was unexpected, aborting...\n");
+		rv = TC_FAIL;
+	}
+	TC_END_RESULT_CUSTOM(rv, "test_pmp");
+	TC_END_REPORT(rv);
+	arch_system_halt(reason);
+}
+
+#ifdef CONFIG_PMP_STACK_GUARD
+static void check_isr_stack_guard(void)
+{
+	char *isr_stack = (char *)z_interrupt_stacks;
+
+	valid_fault = true;
+	*isr_stack = 42;
+}
+
+static void check_main_stack_guard(void)
+{
+	char *main_stack = (char *)z_main_stack;
+
+	valid_fault = true;
+	*main_stack = 42;
+}
+
+#else
+
+static void check_isr_stack_guard(void)
+{
+	ztest_test_skip();
+}
+
+static void check_main_stack_guard(void)
+{
+	ztest_test_skip();
+}
+
+#endif /* CONFIG_PMP_STACK_GUARD */
+
+typedef void (*pmp_test_func_t)(void);
+
+static const pmp_test_func_t pmp_test_func[] = {
+	check_isr_stack_guard,
+	check_main_stack_guard,
+};
+
+/**
+ * @brief Verify RISC-V specific PMP stack guard regions.
+ * @details Manually write to the protected stack region to trigger fatal error.
+ */
+ZTEST(riscv_pmp_no_mt, test_pmp)
+{
+#ifndef PMP_TEST_FUNC_IDX
+#define PMP_TEST_FUNC_IDX 0
+#endif
+	pmp_test_func[PMP_TEST_FUNC_IDX]();
+
+	zassert_unreachable("Write to stack guard did not fault");
+	TC_END_REPORT(TC_FAIL);
+}
+
+ZTEST_SUITE(riscv_pmp_no_mt, NULL, NULL, NULL, NULL, NULL);

tests/arch/riscv/pmp/no-multithreading/testcase.yaml

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+common:
+  platform_allow:
+    - qemu_riscv32
+    - qemu_riscv32e
+    - qemu_riscv64
+  filter: CONFIG_RISCV_PMP
+  ignore_faults: true
+
+tests:
+  arch.riscv.pmp.no-mt.isr-stack-guard:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=0
+  arch.riscv.pmp.no-mt.main-stack-guard:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1