riscv: implements arch_thread_priv_stack_space_get

This implements arch_thread_priv_stack_space_get() so this can
be used to figure out how much privileged stack space is used.

Signed-off-by: Daniel Leung <[email protected]>

Author: dcpleung

arch/Kconfig

@@ -121,6 +121,7 @@ config RISCV
 	select SCHED_IPI_SUPPORTED if SMP
 	select ARCH_HAS_DIRECTED_IPIS
 	select BARRIER_OPERATIONS_BUILTIN
+	select ARCH_HAS_THREAD_PRIV_STACK_SPACE_GET if USERSPACE
 	imply XIP
 	help
 	  RISCV architecture

arch/riscv/core/thread.c

@@ -195,6 +195,18 @@ FUNC_NORETURN void arch_user_mode_enter(k_thread_entry_t user_entry,
 	CODE_UNREACHABLE;
 }
 
+int arch_thread_priv_stack_space_get(const struct k_thread *thread, size_t *stack_size,
+				     size_t *unused_ptr)
+{
+	if ((thread->base.user_options & K_USER) != K_USER) {
+		return -EINVAL;
+	}
+
+	*stack_size = Z_STACK_PTR_ALIGN(K_KERNEL_STACK_RESERVED + CONFIG_PRIVILEGED_STACK_SIZE);
+
+	return z_stack_space_get((void *)thread->arch.priv_stack_start, *stack_size, unused_ptr);
+}
+
 #endif /* CONFIG_USERSPACE */
 
 #ifndef CONFIG_MULTITHREADING