The Linux Kernel, as released on Kernel.org, contains obfuscated source code and code that is licensed as non-Free Software. More disturbingly there are also binary blobs to which no source code is available for review/auditing/improving.
Some distributions like Debian remove all of non-free code.
For those wanting a “vanilla” Kernel to compile that is untainted with propriatery code The Free Software Foundation Latin America are here to help. They release a copy of the kernel that has run through a series of scripts to strip out the unwanted code.
The FSLA Kernel works fine with GRsecurity. I have been using this combination on my Linode and Laptops without any real issues so far.