Linux kernel, missing '__fentry__' symbol

Trying to build the EtherCAT master driver (realtime I/O driver) on a RT Linux (SL6.3) I keep bumping into a missing symbol issue when building the EtherCAT kernel modules: # make modules make -C "/usr/src/kernels/3.8.13-rt27.40.el6rt.x86_64" M="/root/etherlabmaster-code-08aa7305b9baba37bdd9eb4d8c2a8762aa56a7e2" modules make[1] : Entering directory `/usr/src/kernels/3.8.13-rt27.40.el6rt.x86_64' Building modules, stage 2. MODPOST 4 modules WARNING: "__fentry__" [/root/etherlabmaster-code-08aa7305b9baba37bdd9eb4d8c2a8762aa56a7e2/master/ec_master.ko] undefined! WARNING: "__fentry__" [/root/etherlabmaster-code-08aa7305b9baba37bdd9eb4d8c2a8762aa56a7e2/examples/mini/ec_mini.ko] undefined! WARNING: "__fentry__" [/root/etherlabmaster-code-08aa7305b9baba37bdd9eb4d8c2a8762aa56a7e2/devices/ec_generic.ko] undefined! WARNING: "__fentry__" [/root/etherlabmaster-code-08aa7305b9baba37bdd9eb4d8c2a8762aa56a7e2/devices/e1000e/ec_e1000e.ko] undefined! make[1] : Leaving directory `/usr/src/kernels/3.8.13-rt27.40.el6rt.x86_64' # grep -Hin "fentry" /boot/config-uname -r /boot/config-3.8.13-rt27.40.el6rt.x86_64:4797:CONFIG_HAVE_FENTRY=y # strings /boot/System.map-3.8.13-rt27.40.el6rt.x86_64 | grep -i "fentry" -- nothing -- # I'm using **GCC v 4.9.1**, as you can see, the kernel config file does contain an entry related to 'fentry' and is enabled. Weird thing is that I would expect the System.map to contain the __fentry__ symbol declared in there, but it isn't!? I've tried building the EtherCAT driver against the kernel 3.10-rt & 3.14-rt, same issue, it's complaining about about the __fentry__ symbol missing. If I go ahead and launch the EtherCAT service, I get the following: # service ethercat start Starting EtherCAT master 1.5.2 FATAL: Error inserting ec_master (/lib/modules/3.8.13-rt27.40.el6rt.x86_64/ethercat/master/ec_master.ko): Unknown symbol in module, or unknown parameter (see dmesg) failed # dmesg | tail ... ec_master: Unknown symbol __fentry__ (err 0)