I am seeing this error when loading a compiled module into my compiled kernel 3.18. This thread indicates that I need "CONFIG_FTRACE=y" in my kernel config:
http://dpdk.org/ml/archives/dev/2014-July/004105.html .
Like the user in that thread, I have compiled the kernel with "CONFIG_FTRACE" turned on and I do not see "__fentry__" in /proc/kallsyms.
What could be going wrong here? I have attached my kernel config to assist in troubleshooting.