How to build Helloword in android custom kernel

Question

insmod: failed to load hello.ko: Function not implemented during kernel build to logout message like 'hello world', I've got such an error, following steps will reproduce the bug:

1)I downloaded goldfish kernel from git clone https://android.googlesource.com/kernel/goldfish/ -b android-goldfish-3.18

2)also downloaded the toolchain coming with the above repo using git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.9

3)I changed directory to goldfish and created the paths mentioned in the documentation (github)

4)then i attempted to build the kernel using this sudo make ARCH=x86_64 CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android- in the kernel directory (goldfish) and set LOADABLE_MODULES=y

5)In the next step, I created hello.c file and the Makefile related to it in helloKernel directory.

hello.c

#include<linux/module.h>
#include<linux/init.h>
#include<linux/kernel.h>

MODULE_AUTHOR("Robert P. J. Day");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION("2:1.0") ;
MODULE_DESCRIPTION("You have to start somewhere.");


static int hello_init(void){
    printk(KERN_ALERT "Hello TheLittleNaruto it’s your first driver.\n");
return 0;
}

static void hello_exit(void){
    printk(KERN_INFO "Goodbye TheLittleNaruto No point in keeping this driv er running.\n");
}

module_init(hello_init);
module_exit(hello_exit);

Makefile

obj-m := hello.o  

KERNELDIR := /home/ana/goldfish/
PWD :=$(shell pwd)  
ARCH=x86_64 
CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android-
CC=$(CROSS_COMPILE)gcc  
LD=$(CROSS_COMPILE)ld  
CFLAGS_MODULE=-fno-pic  

modules:  
    make -C $(KERNELDIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) M=$(PWD) modules    
clean:    
    rm *.o *.ko *.mod.c *.order *.symvers

in the same directory I created hello.ko with this sudo make ARCH=x86_64 CROSS_COMPILE=/home/ana/x86_64-linux-android-4.9-nougat-dev/bin/x86_64-linux-android-

7)and then i copied hello.ko to android emulator using sudo adb push hello.ko /data/local

8)and then i attempt insmod hello.ko in /data/local

and I get the above-mentioned error, please help me solve this problem. thanks in advance

score 0 · Answer 1 · answered Jul 17 '21 at 18:14

0

two things to add in your code

function entry and exit routine module_init(init_module); module_exit(cleanup_module);
Let init_module function return 0 rather 1 because 0 means we are good.

answered Jul 17 '21 at 18:14

tej parkash

137
2

I add above functions but i get same error – Reza Bakhshande Jul 19 '21 at 04:56
can you please show us the complete code again – tej parkash Jul 19 '21 at 06:32
Do you think the problem with wrong execution of the kernel in the emulator or my hello.c? – Reza Bakhshande Jul 19 '21 at 06:49
Never seen such error earlier but can you check in your kernel .config if it has enabled CONFIG_MODULES=y and CONFIG_MODULE_UNLOAD=y options – tej parkash Jul 19 '21 at 08:11
Yes, enable but i think my kernel have a problem because after i run emulator with custom kernel i see dark image on my emulator – Reza Bakhshande Jul 19 '21 at 08:16
Kind of running out of idea. lets enable debug_initcall, as somewhere init code is returning ENOSYS, causing this issue. https://chengyihe.wordpress.com/2015/12/13/android-kernel-enable-initcall_debug-to-debug-initcall/ – tej parkash Jul 19 '21 at 10:30
Can i add and build hello.c in my emulator without building custom kernel? (with defult emulator kernel) – Reza Bakhshande Jul 24 '21 at 05:52

How to build Helloword in android custom kernel

1 Answers1