Parse error with kprobe event registration

Question

I'm testing kprobe events on CentOS 7, kernel version 3.10.0-1160.59.1.el7.x86_64.

[root@linux2 ~]# echo 'p:qwe do_sys_openat2 filename=+0($arg2):string' > /sys/kernel/debug/tracing/kprobe_events
-bash: echo: write error: Invalid argument
[root@linux2 ~]# dmesg
[447101.144698] Parse error at argument[0]. (-22)

Does anyone know what's wrong here?