Android Systemtap can not load module

Question

I am trying to load a simple Systemtap module on my GT-i9300

I get the error

Error inserting module '/sdcard/systemtap/modules/monitor_fopen.ko': Unknown symbol in module

Steps that I took:

---

1. Get root on the device

I did this by installing this Rom

2. Build custom kernel

# ====================================================
# Add toolchain

user@ubuntu1210:~/Programs$ git clone https://android.googlesource.com/platform/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.7

user@ubuntu1210:~$ sudo gedit .bashrc


    # Toolchain
    export PATH=${PATH}:~/Programs/arm-linux-androideabi-4.7/bin


# Reboot ubuntu 
# ====================================================


# ====================================================
# Download and extract to ~/android/kernel : 
# https://github.com/SlimRoms/kernel_samsung_smdk4412.git

user@ubuntu1210:~$ cd android/kernel/kernel_samsung_smdk4412/


# ====================================================


# ====================================================
# Set configuration for compiling


user@ubuntu1210:~/android/kernel/kernel_samsung_smdk4412$ make clean -j4 ARCH=arm SUBARCH=arm CROSS_COMPILE=arm-linux-androideabi-

user@ubuntu1210:~/android/kernel/kernel_samsung_smdk4412$ make ARCH=arm SUBARCH=arm CROSS_COMPILE=arm-linux-androideabi- slim_i9300_defconfig

user@ubuntu1210:~/android/kernel/kernel_samsung_smdk4412$ gedit .config

    # Enable config parameters:
    CONFIG_DEBUG_INFO, CONFIG_KPROBES, CONFIG_RELAY, CONFIG_DEBUG_FS, CONFIG_MODULES, CONFIG_MODULE_UNLOAD


# ====================================================
# Build Kernel

user@ubuntu1210:~/android/kernel/kernel_samsung_smdk4412$ make -j4 ARCH=arm SUBARCH=arm CROSS_COMPILE=arm-linux-androideabi-

3. Flash built zImage to device

# Download and extract bootimg_tools.zip from
# http://forum.xda-developers.com/showpost.php?p=44670032&postcount=12
# 
# Download correct ROM .zip file and extract boot.img to the same folder as bootimg_tools

user@ubuntu1210:~/bootimg_tools$ perl split_bootimg.pl boot.img

user@ubuntu1210:~/bootimg_tools$ perl unpack_ramdisk boot.img-ramdisk.gz ramdisk

user@ubuntu1210:~/bootimg_tools$ perl repack_ramdisk ramdisk boot.img-ramdisk.cpio.gz

user@ubuntu1210:~/bootimg_tools$ cp /home/user/kernel_samsung_smdk4412/arch/arm/boot/zImage boot.img-kernel

user@ubuntu1210:~/bootimg_tools$ ./mkbootimg --kernel boot.img-kernel --ramdisk boot.img-ramdisk.cpio.gz --cmdline 'console=null androidboot.hardware=qcom user_debug=31 zcache' --base 0x80200000 --pagesize 2048 -o boot.img

# Download and install heimdall
# https://bitbucket.org/benjamin_dobell/heimdall/downloads

user@ubuntu1210:~/bootimg_tools$ adb reboot bootloader

user@ubuntu1210:~/bootimg_tools$ sudo heimdall flash --BOOT boot.img --verbose

4. Install systemtap on PC

user@ubuntu1210:~$ mkdir systemtap
user@ubuntu1210:~$ cd systemtap/
user@ubuntu1210:~/systemtap$ git clone https://github.com/flipreverse/systemtap-android.git
user@ubuntu1210:~/systemtap$ cd systemtap-android/
user@ubuntu1210:~/systemtap/systemtap-android$ git submodule init
user@ubuntu1210:~/systemtap/systemtap-android$ git submodule update
user@ubuntu1210:~/systemtap/systemtap-android$ sh build.sh 

5. Create an .stp file

user@ubuntu1210:~$ cd /home/user/systemtap/systemtap-android/scripts/
user@ubuntu1210:~$ vi monitor_fopen.stp

#! /usr/bin/stap


probe begin
{
        printf("start monitoring");
}

probe end
{
        printf("end monitoring");
}

6. Build .ko file out of .stp file using compiled Kernel

user@ubuntu1210:~$ /home/user/systemtap/systemtap-android/installed/bin/stap 
-p 4 -v  
-a arm 
-B CROSS_COMPILE=/home/user/Programs/arm-linux-androideabi-4.7/bin/arm-linux-androideabi- 
-r /home/user/android/kernel/kernel_samsung_smdk4412/ 
-j /home/user/systemtap/systemtap-android/installed/share/systemtap/tapset/ 
-R /home/user/systemtap/systemtap-android/installed/share/systemtap/runtime/ 
-t -g -m monitor_fopen /home/user/systemtap/systemtap-android/scripts/monitor_fopen.stp

7. Install Systemtap Android App on the device that runs the custom Kernel

https://github.com/flipreverse/systemtap-android-app

8. Start the app and give the app root access

Superuser.apk should ask you whether Systemtap can have root access

9. Push the .ko file from step 6 to the sdcard

user@ubuntu1210:~$ adb push monitor_fopen.ko /sdcard/systemtap/modules/monitor_fopen.ko

10. Load the module

user@ubuntu1210:~$ adb shell
shell@android:/ $ su
root@android:/ # cd /data/data/com.systemtap.android
root@android:/data/data/com.systemtap.android # sh start_stap.sh   

modulename=monitor_fopen
moduledir=/sdcard/systemtap/modules
outputname=monitor_fopen_2014.mm.dd_sss
outputdir=/sdcard/systemtap/stap_output
logdir=/sdcard/systemtap/stap_log
rundir=/sdcard/systemtap/stap_run
stapdir=/data/data/com.systemtap.android
:q!

11. Read result from loading the module

user@ubuntu1210:~$ adb shell
shell@android:/ $ cd sdcard/systemtap/stap_log/
shell@android:/sdcard/systemtap/stap_log $ cat monitor_fopen_2014.mm.dd_sss.txt

Loaded kernel module: monitor_fopen.ko Output file: monitor_fopen_2014.mm.dd_sss.* Error inserting module '/sdcard/systemtap/modules/monitor_fopen.ko': Unknown symbol in module

---

I have no idea in what step I went wrong. Does anyone have a clue?

Answer 1

thanks to @adelphus, he remembered me to use dmesg and I found the error:

Android: Unknown symbol _GLOBAL_OFFSET_TABLE_

With the help of this site I edited the Makefile of the kernel to

CFLAGS_MODULE   = -fno-pic

Redoing all the other steps in my OP then worked.