tests: riscv: Validate PMP stack protection under MULTITHREADING

The PMP stack guard test was previously limited to the non-multithreaded
(no-mt) configuration.

This commit updates the test implementation to conditionally handle
stack boundary lookup:

1. When CONFIG_MULTITHREADING is enabled, it uses thread-specific stack
   information (e.g., z_interrupt_stacks[_current_cpu->id] for ISR stack
   and k_current_get()->stack_info for the main thread stack).

2. New test configurations (arch.riscv.pmp.mt.*) are added to explicitly
   run the tests with CONFIG_MULTITHREADING=y.

This ensures PMP stack guards are correctly verified in a multi-threaded
environment.

Signed-off-by: Firas Sammoura <[email protected]>

Author: fsammoura1980

tests/arch/riscv/pmp/no-multithreading/CMakeLists.txt renamed to tests/arch/riscv/pmp/isr-stack-guard/CMakeLists.txt

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

tests/arch/riscv/pmp/isr-stack-guard/prj.conf

@@ -24,6 +24,30 @@ void k_sys_fatal_error_handler(unsigned int reason, const struct arch_esf *pEsf)
 }
 
 #ifdef CONFIG_PMP_STACK_GUARD
+
+#ifdef CONFIG_MULTITHREADING
+
+static void check_isr_stack_guard(void)
+{
+	char *isr_stack = (char *)z_interrupt_stacks[_current_cpu->id];
+
+	valid_fault = true;
+	*isr_stack = 42;
+}
+
+static void check_main_stack_guard(void)
+{
+	struct k_thread *current_thread_ptr = k_current_get();
+	uintptr_t stack_bottom = current_thread_ptr->stack_info.start - K_KERNEL_STACK_RESERVED;
+
+	char *main_stack = (char *)stack_bottom;
+
+	valid_fault = true;
+	*main_stack = 42;
+}
+
+#else /* CONFIG_MULTITHREADING */
+
 static void check_isr_stack_guard(void)
 {
 	char *isr_stack = (char *)z_interrupt_stacks;
@@ -40,7 +64,9 @@ static void check_main_stack_guard(void)
 	*main_stack = 42;
 }
 
-#else
+#endif /* CONFIG_MULTITHREADING */
+
+#else /* CONFIG_PMP_STACK_GUARD */
 
 static void check_isr_stack_guard(void)
 {
@@ -65,7 +91,7 @@ static const pmp_test_func_t pmp_test_func[] = {
  * @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)
+ZTEST(riscv_pmp_isr_main_stack, test_pmp)
 {
 #ifndef PMP_TEST_FUNC_IDX
 #define PMP_TEST_FUNC_IDX 0
@@ -76,4 +102,4 @@ ZTEST(riscv_pmp_no_mt, test_pmp)
 	TC_END_REPORT(TC_FAIL);
 }
 
-ZTEST_SUITE(riscv_pmp_no_mt, NULL, NULL, NULL, NULL, NULL);
+ZTEST_SUITE(riscv_pmp_isr_main_stack, NULL, NULL, NULL, NULL, NULL);

tests/arch/riscv/pmp/no-multithreading/src/main.c renamed to tests/arch/riscv/pmp/isr-stack-guard/src/main.c

@@ -0,0 +1,25 @@
+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
+    extra_configs:
+      - CONFIG_MULTITHREADING=n
+  arch.riscv.pmp.no-mt.main-stack-guard:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1
+    extra_configs:
+      - CONFIG_MULTITHREADING=n
+  arch.riscv.pmp.mt.isr-stack-guard:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=0
+    extra_configs:
+      - CONFIG_MULTITHREADING=y
+  arch.riscv.pmp.mt.main-stack-guard:
+    extra_args: EXTRA_CFLAGS=-DPMP_TEST_FUNC_IDX=1
+    extra_configs:
+      - CONFIG_MULTITHREADING=y