Fall2009/Kernel Hacking Exercise
From OpenSourceSoftwarePractice
Kernel Hacking Exercise
Contents |
Download the source code
- http://www.kernel.org/
- Stable Kernel version : 2.6.30.9
Expand
cd mkdir KernelHacking cd KernelHacking wget http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.30.9.tar.bz2 tar xjvf linux-2.6.30.9.tar.bz2
Configure
cd linux-2.6.30.9 wget http://files.robescriva.com/ossp/config mv {,.}config make menuconfig
 Move the cursor to General Setup and press ENTER |
 Move the cursor down to Local version and press ENTER |
 Enter the string 'OpenSourceClass' and select Ok |
 To go back to the previous menu, press the Right cursor key to select Exit and press ENTER (alternatively, you can hit Esc twice to go back) |
 To exit and save your configuration, select Exit (or double-Esc). |
 You'll be asked to save your new kernel configuration. Select Yes and press ENTER |
Build
To build the kernel (both the image and modules), type:
make -j4
Where "4" is meant as double the number of processors of your system. For example, if you have a quad-core processor, then you should use -j8.
Your newly compiled kernel image can be found in
arch/<platform>/boot/bzImage
Most likely, your <platform> will be x86 or i386
To install the new kernel image, copy it to the /boot directory
sudo cp arch/x86/boot/bzImage /boot/OpenSourceClassKernel
To install the modules, type:
sudo make modules_install
They should now appear under:
/lib/modules/2.6.30.9OpenSourceClass
Reconfigure GRUB
cd /boot/grub edit menu.lst
insert the lines
title Ubuntu-OpenSourceClass root (hd0,0) kernel /boot/OpenSourceClassKernel
Reboot
Before rebooting the first time, you will then need to edit the grub configuration file
http://www.linuxchix.org/content/courses/kernel_hacking/lesson4
Rule number one is never ever delete your current working kernel or bootloader configuration files. Never copy your new kernel over your original kernel. You don't need to keep every kernel you ever compile, but do pick one or more "safe" kernels and keep them and their configuration files intact.
After modifying your grub configuration, reboot.
sudo shutdown -r now
Modify
Go to the directory "init"
cd init
and edit the file
main.c
go to lines 931 where you will see lines
/* * Ok, we have completed the initial bootup, and * we're essentially up and running. Get rid of the * initmem segments and start the user-mode stuff.. */ init_post(); return 0; }
and before "init_post()" insert the following line:
printk("OpenSourceClass: My First Kernel Message");
go back to the parent directory
cd ..
Build / Reboot
Now that you are back in the linux-2.6.30.9 directory, build your modified kernel, copy it to /boot, and restart.
make -j4 sudo cp arch/x86/boot/bzImage /boot/OpenSourceClassKernel sudo shutdown -r now
You do not need to edit your grub config again.
Modify
Go to the directory "fs"
cd fs
and edit the file
read_write.c
go to lines 799 and insert the following line of code
printk(KERN_DEBUG "OpenSource Class Exercise: %s:%i\n", __FILE__, __LINE__);
go back to the parent directory
cd ..
Build / Reboot
Just as before, rebuild the kernel, copy it to /boot and restart.
