DynAMOS is distributed with examples of kernel updates in source code form for Linux 2.4. The source code can be compiled and prepared to be applied as an update. The updated functionality can be loaded in the kernel and activated using the DynAMOS framework. The following examples demonstrate how the collection of tools offered by DynAMOS are used together from start to finish in dynamically applying a kernel update.
The general format of running these examples is shown in Figure 5-1.
Figure 5-1. Running the example updates.
# DynAMOS must run with administrator privileges.
bash$ su -
Password:
bash#
# Start the framework
bash# /etc/init.d/dynamos start
# Check if everything started correctly
bash# dmesg -c
# Build an example's source
bash# cd /usr/share/doc/dynamos/examples/get_pid
bash# make
# Load the example's module
bash# insmod final_dynreplace_file.o
# Activate the update
bash# ./activate.sh
# Verify things work
bash# dmesg -c
bash# cat /dev/dynamos
# Deactivate the update
bash# ./deactivate.sh
# Verify the update is not effective
bash# dmesg -c
bash# cat /dev/dynamos
# Unload the example's module
bash# rmmod final_dynreplace_file
# Stop the framework
bash# /etc/init.d/dynamos stop
# Check if everything stopped correctly
bash# dmesg -c
get_pid() is the Linux process allocation routine. It returns the next available process id that can be used by a newly created process. When applied, this update will report in the kernel logs on process creation the id of the process that calls get_pid() and the pid it returns, as shown in Figure 5-2.