Creating-modules-and-Hooking-syscalls

Creating modules

A kernel module create character device for process in user space read a random integer

Environment: Virtual Box with Ubuntu 18.04 (64 bit), kernel version 5.0.0-32-generic.

Setup

• Open 2 terminal windows.

• On the first terminal:

  • Compile main.c

    $ gcc -o main main.c

  • Build module hung_chrdev

    $ make

  • Insert moudule into Kernel.

    $ sudo insmod hung_chrdev.ko

  • Run main

    $ ./main

• On the second terminal: see messages on the logging.

  $ sudo dmesg -c
  $ sudo dmesg -wH

• Remove module from kernel on the first terminal.

  $ sudo rmmod hung_chrdev

Hooking syscalls

A kernel module hooking onto sys_write and sys_open.

Created in Zorin 12.4 on 64 bit, with kernel version 4.15.0-30-generic.

Setup

• Open 2 terminals.

• On the first terminal:

  • Compile test.c.

    $ gcc test.c -o test

  • Compile module hook.

    $ make

  • Insert moudule into Kernel.

    $ sudo insmod hook.ko

  • Run test.

    $ ./test

• On the second terminal: see messages on the logging.

  $ sudo dmesg -c
  $ sudo dmesg -wH

• Remove module from kernel on the first terminal.

  $ rm hook