linux - GDB: lx-symbols undefined command -

I am following the guide below:

When I use the following command Trying to load the module symbols while doing: (GDB) LX-symbols

GDB says this order is undefined. How do I add these helper commands to gdb?

GDB Info: GDB-7.6.1-51. Santos 7.0 at el7.x86-64

You must obtain the latest kernel source (may be 4.0-RC4) or backport. Actually, you have a script / gdb / directory in the kernel sources because this is where you get these scripts.

Then you follow the steps outlined in