Kernel debugging using KGDB

KGDB is full integrated with the latest kernel. These instructions are for linux-2.6.31.12. Not sure if these will work for any previous or later versions.

1. make menuconfig and select the following
1. Select Kernel Hacking → KGDB: kernel debugging with remote gdb
1. Select KGDB: use kgdb over the serial console
2. Build the kernel
    make bzImage; make modules; sudo make modules_install
3. Install the kernel. Copy bzImage, System.map and .config into /boot
4. On another machine (say remote) where the serial null modem cable is connected, copy the entire kernel folder that you compiled on the target machine. 
5. Restart the target machine.  At the grub menu, select your kernel, edit it and add the following at the end of the kernel line:
    kgdboc=ttyS0,115200 kgdbwait
   This is assuming that you have a serial port and it is connected on ttyS0. Boot into your kernel. It will wait for gdb to connect.
6. On the remote machine, go in the kernel folder you copied over and debug vmlinx by starting gdb
1. gdb ./vmliux
2. Set the baud rate - (gdb) set remotebaud 115200
3. Connect to the target - (gdb) target remote /dev/ttyS0
4. Run the kernel - (gdb) continue

For more details, refer to the docbook on KGDB in the kernel documentation folder. Just do a make htmldocs to convert into a readable format. You would have to install xmlto first. sudo aptitude install xmlto should help.