Compilation for xenserver 6.5

[stipmonster]

HI i am trying to compile the vrouter.ko for xenserver 6.5. I have downloaded the kernel sources iso from the xenserver website and used the scons --kernel-dir=~/3.10.0+2-x86_64/ --system-header-path=~/3.10.0+2-x86_64/ vrouter command to compile it when i try to load it the following error shows in demise vrouter: Unknown symbol __fentry__ (err 0)

I tried multiple versions all give the same error. Any idea if this is a bug or am i doing something wrong?