Infrastructure

In order to facilitate learning each topic has a hands-on exercises section which will contain in-depth, incremental clues on how to solve one or multiple tasks. To focus on a particular issue most of the tasks will be performed on existing skeleton drivers. Each skeleton driver has clearly marked sections that needs to be filled in order to complete the tasks.

The skeleton drivers are generated from full source examples located in tools/labs/templates. To solve tasks you start by generating the skeleton drivers, running the skels target in tools/labs. To keep the workspace clean it is recommended to generate the skeletons for one lab only and clean the workspace before start working on a new lab. Labs can be selected by using the LABS variable:

tools/labs $ make clean
tools/labs $ LABS=kernel_modules make skels

tools/labs $ ls skels/kernel_modules/
1-2-test-mod  3-error-mod  4-multi-mod  5-oops-mod  6-cmd-mod  \
7-list-proc  8-kprobes  9-kdb

You can also use the same variable to generate skeletons for specific tasks:

tools/labs $ LABS="kernel_modules/6-cmd-mod kernel_modules/8-kprobes" make skels

tools/labs$ ls skels/kernel_modules
6-cmd-mod  8-kprobes

For each task you may have multiple steps to perform, usually incremental. These steps are marked in the source code as well as in the lab exercises with the keyword TODO. If we have multiple steps to perform they will be prefixed by a number, like TODO1, TODO2, etc. If no number is used it is assumed to be the one and only step. If you want to resume a task from a certain step, you can using the TODO variable. The following example will generate the skeleton with the first TODO step resolved:

tools/labs $ TODO=2 LABS="kernel_modules/8-kprobes" skels

Once the skelton drivers are generated you can build them with the build make target:

tools/labs $ make build
echo "# autogenerated, do not edit " > skels/Kbuild
for i in ./kernel_modules/8-kprobes; do echo "obj-m += $i/" >> skels/Kbuild; done
make -C /home/tavi/src/linux M=/home/tavi/src/linux/tools/labs/skels ARCH=x86 modules
make[1]: Entering directory '/home/tavi/src/linux'
CC [M]  /home/tavi/src/linux/tools/labs/skels/./kernel_modules/8-kprobes/kprobes.o
Building modules, stage 2.
MODPOST 1 modules
CC      /home/tavi/src/linux/tools/labs/skels/./kernel_modules/8-kprobes/kprobes.mod.o
LD [M]  /home/tavi/src/linux/tools/labs/skels/./kernel_modules/8-kprobes/kprobes.ko
make[1]: Leaving directory '/home/tavi/src/linux'

To copy the drivers to the VM you can use either use ssh or update the VM image directly using the copy target:

tools/labs $ make copy
...
'skels/kernel_modules/8-kprobes/kprobes.ko' -> '/tmp/tmp.4UMKcISmQM/home/root/skels/kernel_modules/8-kprobes/kprobes.ko'

Attention

The copy target will fail if the VM is running. This is intentional so that we avoid corrupting the filesystem.