Question

I am trying to create a simple kernel module.
I am trying to print messages to dmesg but i keep getting

insmod: init_module ‘hello.ko’ failed (Exec format error) in android

after :
dmesg:
unknown relocation: 27

#include <linux/module.h>
#include <linux/kdb.h>
int init_module(void)
{
    printk(KERN_ALERT "Hello world!\n");
    return 1;
}

void cleanup_module(void)
{
    printk(KERN_INFO "Goodbye world 1.\n");
}
MODULE_AUTHOR("Robert P. J. Day");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_VERSION("2:1.0") ;
MODULE_DESCRIPTION("You have to start somewhere.");

The make file

    obj-m +=hello.o


KERNELDIR ?= ~/android/kernel/common
#KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
CROSS_COMPILE=~/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-

ARCH=arm
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) ARCH=arm CROSS_COMPILE=$(CROSS_COMPILE) modules

clean:
$(MAKE) -C $(KERNELDIR) M=$(PWD) clean
rm *.symvers

does anyone know why? And how to get it working?

I found after doing a readelf that when it is compiled the relocation section is pointing to the wrong directions.

Offset     Info    Type            Sym.Value  Sym. Name
00000008  0000171b R_ARM_PLT32       00000000   printk

When in fact it should be:

Offset     Info    Type            Sym.Value  Sym. Name
00000008  0000171c R_ARM_CALL       00000000   printk

Can someone guess/know how this might be?
Thanks @Chris Stratton for helping me this far.

---

I found after doing a readelf that when it is compiled the relocation section is pointing to the wrong directions.

Offset     Info    Type            Sym.Value  Sym. Name
00000008  0000171b R_ARM_PLT32       00000000   printk

When in fact it should be:

Offset     Info    Type            Sym.Value  Sym. Name
00000008  0000171c R_ARM_CALL       00000000   printk

Can someone guess/know how this might be? Thanks @Chris Stratton for helping me this far.

Answer 1

It turns out I had to use

make CFLAGS_MODULE=-fno-pic