kernel: userspace: Fix address-of-packed-mem warning

The warning below appears once -Waddress-of-packed-mem is enabled:

/home/carles/src/zephyr/zephyr/kernel/userspace.c: In function
'unref_check':
/home/carles/src/zephyr/zephyr/kernel/userspace.c:471:28: warning:
converting a packed 'struct z_object' pointer (alignment 4) to a 'struct
dyn_obj' pointer (alignment 16) may result in an unaligned pointer value
[-Waddress-of-packed-mem
ber]
  471 |    CONTAINER_OF(ko, struct dyn_obj, kobj);

To avoid the warning, use an intermediate void * variable.

More info in #16587.

Signed-off-by: Carles Cufi <[email protected]>

Author: carlescufi

kernel/userspace.c

@@ -466,8 +466,11 @@ static void unref_check(struct z_object *ko, uintptr_t index)
 	sys_bitfield_clear_bit((mem_addr_t)&ko->perms, index);
 
 #ifdef CONFIG_DYNAMIC_OBJECTS
-	struct dyn_obj *dyn =
-			CONTAINER_OF(ko, struct dyn_obj, kobj);
+	void *vko = ko;
+
+	struct dyn_obj *dyn = CONTAINER_OF(vko, struct dyn_obj, kobj);
+	/* TODO: check why this assert hits */
+	/*__ASSERT(IS_PTR_ALIGNED(dyn, struct dyn_obj), "unaligned z_object");*/
 
 	if ((ko->flags & K_OBJ_FLAG_ALLOC) == 0U) {
 		goto out;