kernel: add a syscall to query generic information about an object

syscall/dispatch.c

@@ -52,6 +52,7 @@ static const virt_addr_t syscall_table[] = {
 		VM_CONTROLLER_SUPPLY_PAGES,
 		vm_controller_supply_pages),
 	SYSCALL_TABLE_ENTRY(KERN_OBJECT_WAIT, kern_object_wait),
+	SYSCALL_TABLE_ENTRY(KERN_OBJECT_QUERY, kern_object_query),
 	SYSCALL_TABLE_ENTRY(FUTEX_WAIT, futex_wait),
 	SYSCALL_TABLE_ENTRY(FUTEX_WAKE, futex_wake),
 };

syscall/object.c

@@ -80,3 +80,32 @@ cleanup:
 	self_thread->tr_state = THREAD_READY;
 	return status;
 }
+
+kern_status_t sys_kern_object_query(
+	kern_handle_t object_handle,
+	kern_object_info_t *out)
+{
+	struct task *self = current_task();
+
+	if (!out) {
+		return KERN_INVALID_ARGUMENT;
+	}
+
+	if (!validate_access_w(self, out, sizeof *out)) {
+		return KERN_MEMORY_FAULT;
+	}
+
+	struct object *obj = NULL;
+	handle_flags_t flags = 0;
+	kern_status_t status
+		= task_resolve_handle(self, object_handle, &obj, &flags);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	out->obj_id = obj->ob_id;
+
+	object_unref(obj);
+
+	return KERN_OK;
+}