default or selected kernelversion does not have config value CONFIG_KEXEC_CORE.
Result is shown for kernelversion 6.9.9

CONFIG_KEXEC_CORE (not configurable)

modulename: kexec.ko

and/or

kexec_relocate.ko

and/or

machine_kexec.ko

and/or

kexec_core.ko

configname: CONFIG_KEXEC_CORE

Linux Kernel Configuration
└─>General architecture-dependent options
└─>KEXEC_CORE
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
arch/powerpc/platforms/pseries/kexec.c

is depended by
CONFIG_KEXEC_FILE