perf: Couldn't record kernel reference relocation symbol

I have compiled perf for my kernel (3.11.10). During the compilation, some libraries were missing, so I have installed those.

But now when I run perf, I get following message:

Couldn't record kernel reference relocation symbolSymbol resolution may be skewed if relocation was used (e.g. kexec).Check /proc/kallsyms permission or run as root.Kernel address maps (/proc/{kallsyms,modules}) were restricted.Check /proc/sys/kernel/kptr_restrict before running 'perf record'If some relocation was applied (e.g. kexec) symbols may be misresolved.Samples in kernel modules can't be resolved as well.

Since I am using custom build kernel, the most obvious explanation to me is, that some option is missing from my kernel. If so, how can I find out what is missing?

I am not sure what exactly perf is complaining about. How can I fix this?

EDIT:

/proc/kallsyms does not exist and /proc/sys/kernel/kptr_restrict contains 0:

$ cat /proc/sys/kernel/kptr_restrict0

I have compiled the kernel myself, and it is possible that it is missing some option. What is this /proc/kallsyms ? How can I enable it in my kernel?