Linux Kernel Modules

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Introduction

Linux Kernel Development Environment

Linux Kernel Development Process

Linux Kernel Compilation

Linux Kernel Modules

Linux Kernel Build System

Linux Kernel Patch

Linux Kernel Developer

Linux Kernel Modules

Lsmod
Show the status of modules in the Linux Kernel
Let's look at two modules
[email protected]:~$ lsmod | grep button
button                 16384  1 i915
[email protected]:~$ lsmod | grep pcspkr
pcspkr                 16384  0
[email protected]:~$
Challenge
Find out where button and pcspkr are under:
/lib/modules/
Kernel Configuration
Mainline
Hello World Module Source Code
Make a "helloworld" directory
[email protected]:~$ mkdir helloworld
Create helloworld.c file under our helloworld directory and add the C code below, this is a simple Hello World Kernel Module
[email protected]:~/helloworld$ helloworld.c
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
​
static int module_init_function(void)
​
{
    printk(KERN_INFO "Module? Hello!\n");
    return 0;
}
​
static void module_exit_function(void)
{
    printk(KERN_INFO "Module? Bye!\n");
}
​
MODULE_LICENSE("GPL");
MODULE_AUTHOR("xe1gyq");
MODULE_DESCRIPTION("My First Linux Kernel Module");
​
module_init(module_init_function);
module_exit(module_exit_function);
Hello World Module Makefile
Create the Makefile under helloworld directory and add the code below
[email protected]:~/helloworld$ nano Makefile
obj-m += helloworld.o
​
all:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
clean:
    make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
Hello World Module Compilation
[email protected]:~/helloworld$ ls
helloworld.c  Makefile
[email protected]rkstation:~/helloworld$
Now compile your Hello World Module
[email protected]:~/helloworld$ make
make -C /lib/modules/4.12.0-kali2-amd64/build M=/home/user/helloworld modules
make[1]: Entering directory '/usr/src/linux-headers-4.12.0-kali2-amd64'
  CC [M]  /home/user/helloworld/helloworld.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/user/helloworld/helloworld.mod.o
  LD [M]  /home/user/helloworld/helloworld.ko
make[1]: Leaving directory '/usr/src/linux-headers-4.12.0-kali2-amd64'
[email protected]:~/helloworld$
Hello World Module Files
[email protected]:~/helloworld$ ls
helloworld.c  helloworld.ko  helloworld.mod.c  helloworld.mod.o  helloworld.o  Makefile  modules.order    Module.symvers
[email protected]:~/helloworld$
[email protected]:~/helloworld$ modinfo helloworld.ko
[email protected]:~/helloworld$ insmod helloworld.ko
[email protected]:~/helloworld$ dmesg
[email protected]:~/helloworld$ lsmod
[email protected]:~/helloworld$ cat /proc/modules
[email protected]:~/helloworld$ rmmod helloworld
[email protected]:~/helloworld$ dmesg

Linux Kernel Compilation

Linux Kernel Build System

Last modified 4yr ago

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Outline

Lsmod

Hello World Module Source Code

Hello World Module Makefile

Hello World Module Compilation

Hello World Module Files