CONFIG_KEXEC_CORE (not configurable)

modulename: kexec.ko

and/or

machine_kexec.ko

and/or

kexec_core.ko

configname: CONFIG_KEXEC_CORE

Linux Kernel Configuration
└─>KEXEC_CORE
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
kernel/kexec_core.c