CONFIG_X86_64 (not configurable)

modulename: bugs_64.ko

and/or

vsyscall_64.ko

and/or

vsyscall_emu_64.ko

and/or

syscall_64.ko

and/or

pci-nommu_64.ko

and/or

reboot.ko

and/or

sys_x86_64.ko

configname: CONFIG_X86_64

Linux Kernel Configuration for x86
└─>X86_64
In linux kernel since version 2.6.12  
source code:
arch/x86/kernel/