Cross-compile error when building kernel (nexus9 memory forensics)

I'm currently following the AndroidMemoryForensics guide (I cannot post a link) on how to extract memory from an android device using LiME. I'm using the flounder_defconfig build configuration and create the .config file using

Code:

---

make flounder_defconfig

---

. In order to be able to load the LiME module to the kernel I need to add the following lines to the .config file:
CONFIG_MODULES=y
CONFIG_MODULES_UNLOAD=y
CONFIG_MODULES_FORCE_UNLOAD=y

When I compile the kernel I set the architecture to arm64 (ARCH=arm64) and use the aarch64-linux-android-4.9 toolchain (CROSS_COMPILE=aarch64-linux-android-4.9/aarch64-linux-android-).
When running

Code:

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make

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I get compile errors saying that "battery_voltage_monitor_on" is undeclared (see below).

If I try to compile the kernel without making the changes to the .config file I get no compile errors.
Am I missing something here, e.g. some package, or have I done something wrong to cause this compile error?
I tried to search for a solution online but have had little success so far so I hope I have better success here :)

Thanks in advance!
Jonas


Output:
CC drivers/htc_debug/stability/reboot_params.o
LD drivers/htc_debug/stability/built-in.o
CC drivers/hwmon/hwmon.o
CC drivers/hwmon/battery_system_voltage_monitor.o
In file included from include/linux/linkage.h:6:0,
from include/linux/kernel.h:6,
from include/linux/sched.h:31,
from /home/jonas/android/Nexus9_Volantis_source/test2/flounder-kernel/tegra/arch/arm64/include/asm/compat.h:25,
from /home/jonas/android/Nexus9_Volantis_source/test2/flounder-kernel/tegra/arch/arm64/include/asm/stat.h:23,
from include/linux/stat.h:5,
from include/linux/module.h:10,
from drivers/hwmon/battery_system_voltage_monitor.c:15:
drivers/hwmon/battery_system_voltage_monitor.c:151:19: error: 'battery_voltage_monitor_on' undeclared here (not in a function)
EXPORT_SYMBOL_GPL(battery_voltage_monitor_on);
^
include/linux/export.h:57:16: note: in definition of macro '__EXPORT_SYMBOL'
extern typeof(sym) sym; \
^
drivers/hwmon/battery_system_voltage_monitor.c:151:1: note: in expansion of macro 'EXPORT_SYMBOL_GPL'
EXPORT_SYMBOL_GPL(battery_voltage_monitor_on);
^
drivers/hwmon/battery_system_voltage_monitor.c:183:19: error: 'system_voltage_monitor_on' undeclared here (not in a function)
EXPORT_SYMBOL_GPL(system_voltage_monitor_on);
^
include/linux/export.h:57:16: note: in definition of macro '__EXPORT_SYMBOL'
extern typeof(sym) sym; \
^
drivers/hwmon/battery_system_voltage_monitor.c:183:1: note: in expansion of macro 'EXPORT_SYMBOL_GPL'
EXPORT_SYMBOL_GPL(system_voltage_monitor_on);
^
make[2]: *** [drivers/hwmon/battery_system_voltage_monitor.o] Error 1
make[1]: *** [drivers/hwmon] Error 2
make: *** [drivers] Error 2