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- Compiling the kernel on the development machine
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Hardware setup
Use a Null modem serial cable to connect across the Target and Development machines .
[ Development machine ]----------------------------------[ Target machine ]1-Hardware pinout for the null modem serial cable OR 2-Hardware pinout for the null modem serial cable
Testing the working of the Null-modem serial cable.
On the Development machine : stty ispeed 115200 ospeed 115200 -F /dev/ttyS0
cat testfile.txt > /dev/ttyS0
On the Target machine :stty ispeed 115200 ospeed 115200 -F /dev/ttyS0
cat /dev/ttyS0
Target machine.
The following settings are used for the Remote debugging session, automatically.
stty -F /dev/ttyS0
speed 115200 baud; line = 0;
min = 1; time = 0;
-brkint -icrnl -imaxbel
-opost -onlcr
-isig -icanon -iexten -echo -echoe -echok -echoctl -echoke
Software setup
- Downloaded Linux kernel source :
- Downloaded the 2.6.7 patch :
- Downloaded the Kgdb patch :
- Unzip the kernel sources & the kernel patch
cd ${BASE_DIR}
tar -zxvf linux-2.6.6.tar.gz
bunzip2 patch-2.6.7.bz2
ls ${BASE_DIR} --> linux-2.6.6 patch-2.6.7
- mv ${BASE_DIR}/linux-2.6.6 ${BASE_DIR}/linux-2.6.7
- cd ${BASE_DIR}/linux-2.6.7
- patch -p1 < ${BASE_DIR}/patch-2.6.7
Applying the kgdb patch
- Unzip the kgdb patch
mkdir ${BASE_DIR}/patch-kgdb
cd ${BASE_DIR}/patch-kgdb
tar -jxvf linux-2.6.7-kgdb-2.2.tar.bz2
- patch -p1 < ${BASE_DIR}/patch-kgdb/core-lite.patch
- patch -p1 < ${BASE_DIR}/patch-kgdb/i386-lite.patch
- patch -p1 < ${BASE_DIR}/patch-kgdb/8250.patch
- patch -p1 < ${BASE_DIR}/patch-kgdb/eth.patch
- patch -p1 < ${BASE_DIR}/patch-kgdb/i386.patch
- patch -p1 < ${BASE_DIR}/patch-kgdb/core.patch
Compiling the kernel on the development machine
- In the ${BASE_DIR}/linux-2.6.7/Makefile, set the EXTRAVERSION = -kgdb
- make mrproper V=1
- make xconfig V=1 or make oldconfig V=1
Select the options appropriate for the target machine Hardware.
Select the options pertaining to kgdb under "Kernel hacking" .
Click to view the snapshot image
- make clean V=1
- make bzImage V=1
- Transfer the built kernel to the Target machine from the Development machine .
Copy the Kernel image from ${BASE_DIR}/linux-2.6.7/arch/i386/boot/bzImage to the target machine as /boot/vmlinuz-2.6.7-kgdb
Copy the Map file from ${BASE_DIR}/linux-2.6.7/System.map to the target machine as /boot/System.map-2.6.7-kgdb
Also create links,
ln -s /boot/vmlinuz-2.6.7-kgdb /boot/vmlinuz
ln -s /boot/System.map-2.6.7-kgdb /boot/System.map
- Edit the /boot/grub/grub.conf file in the target machine to have the kgdb enabled kernel entry.
Sample is shown below :-
# Sample grub.conf which will by default boot the kgdb enabled kernel
default=1
timeout=10
splashimage=(hd0,0)/boot/grub/splash.xpm.gz
title RH
root (hd0,0)
kernel /boot/vmlinuz ro root=/dev/sda1
initrd /boot/initrd
title Linux-2.6.7-kgdb
root (hd0,0)
kernel /boot/vmlinuz-2.6.7-kgdb ro root=/dev/sda1 rootfstype=ext3 kgdbwait kgdb8250=0,115200
Starting the debug session
- After booting the target machine will wait for the host development machine to connect, by displaying the message :-
Waiting for connection from remote gdb...
- cd ${BASE_DIR}/linux-2.6.7
- For setting a debug session with baud rate of 115200 on /dev/ttyS0 , run as "root" user:-
gdb ./vmlinux
GNU gdb Red Hat Linux (6.0post-0.20040223.17rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty" for details.
This GDB was configured as "i386-redhat-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1".
(gdb) shell echo -e "\003" > /dev/ttyS0
(gdb) set remotebaud 115200
(gdb) target remote /dev/ttyS0
Remote debugging using /dev/ttyS0
breakpoint () at kernel/kgdb.c:1212
1212 atomic_set(&kgdb_setting_breakpoint, 0);
warning: shared library handler failed to enable breakpoint
(gdb)
- For further commands refer
Useful links and Miscellaneous information
- Useful Links :
- Active Developer : Amit Kale --> amitkale@linsyssoft.com
- Bug Report : kgdb-bugreport@lists.sourceforge.net
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