Linux Driver Development

1. Install Linux
2. Write Hello World
hello.c

 #include <linux/kernel.h> /*Needed by all modules*/#include <linux/module.h> /*Needed for KERN_* */#include <linux/init.h> /* Needed for the macros */MODULE_LICENSE("GPL");static int year=2014;static int hello_init(void){  printk(KERN_WARNING "Hello kernel, it‘s %d!\n",year);  return 0;}static void hello_exit(void){  printk("Bye, kernel!\n");}/* main module function*/module_init(hello_init);module_exit(hello_exit);

Obj-m: = hello.o is compiled into a module, followed by the corresponding file name plus. o
Makefile

 obj-m  := hello.oKERNELDIR ?= /lib/modules/$(shell uname -r)/buildPWD       := $(shell pwd)all:    $(MAKE) -C $(KERNELDIR) M=$(PWD)clean:    rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions

Install Module command insmod./hello.ko
Remove Rmmod./hello.ko
viewing logs with command Tail/var/log/kern.log

 [email protected]:~/desktop# makemake-c/lib/modules/4.2.0-27-generic/build M=/root/Desktopmake[1]: Entering Directory '/usr/src/linux-headers-4.2.0-27-generic ' LD/ROOT/DESKTOP/BUILT-IN.O CC [M]/root/desktop/hello.o Buil  Ding modules, Stage 2. Modpost 1 Modules cc/root/desktop/hello.mod.o LD [M]/root/desktop/hello.komake[1]: Leaving directory '/usr/src/l Inux-headers-4.2.0-27-generic ' [email protected]:~/desktop# insmod./hello.ko[email protected]:~/ desktop# Tail/var/log/kern.logaug 05:54:38 ubuntu kernel: [11.882941] audit:type=1400 Audit (1535288078.331:11): AP Parmor= "STATUS" operation= "Profile_load" profile= "unconfined" name= "/usr/lib/lightdm/lightdm-guest-session" pid= 825 comm= "Apparmor_parser" 05:54:38 ubuntu kernel: [12.138198] Ipv6:addrconf (NETDEV_UP): Eth0:link is not ready 05:54:38 ubuntu kernel: [12.423300] E1000:eth0 NIC Link is up $ Mbps full Duplex, Flow Control:noneaug 26 0 5:54:38 ubuntu kernel: [12.436023] Ipv6:addrconf (netdev_change): Eth0:link becomes Readyaug-05:55:05 ubuntu kernel: [39.322268] Audit_printk_sk b:150 callbacks Suppressedaug 05:55:05 ubuntu kernel: [39.322272] audit:type=1400 Audit (1535288105.459:62): Apparm Or= "STATUS" operation= "Profile_replace" profile= "unconfined" name= "/usr/lib/cups/backend/cups-pdf" pid=2171 comm= "  Apparmor_parser "05:55:05 ubuntu kernel: [39.322282] audit:type=1400 Audit (1535288105.459:63): apparmor=" STATUS " operation= "Profile_replace" profile= "unconfined" name= "/usr/sbin/cupsd" pid=2171 comm= "Apparmor_parser" 26 05:55:05 ubuntu kernel: [39.322809] audit:type=1400 Audit (1535288105.459:64): apparmor= "STATUS" operation= "profile_re Place "profile=" unconfined "name="/usr/sbin/cupsd "pid=2171 comm=" Apparmor_parser "to 06:15:14 Ubuntu kernel: [ 1248.118385] Hello:module verification failed:signature and/or required key missing-tainting Kernelaug to 06:15:14 Ubu NTU kernel: [1248.121354] Hello kernel, it ' s 2014![email protected]:~/desktop# rmmod/hello.ko [email protected]:~/desktop# Tail/var/log/kern.logaug 26   05:54:38 ubuntu kernel: [12.138198] Ipv6:addrconf (NETDEV_UP): Eth0:link is not Readyaug-05:54:38 ubuntu kernel: [ 12.423300] E1000:eth0 NIC Link is up to $ Mbps full Duplex, Flow Control:noneaug 05:54:38 ubuntu kernel: [12.436 023] Ipv6:addrconf (netdev_change): Eth0:link becomes Readyaug-05:55:05 ubuntu kernel: [39.322268] Audit_printk_skb : Callbacks Suppressedaug 05:55:05 ubuntu kernel: [39.322272] audit:type=1400 Audit (1535288105.459:62): Apparmo R= "STATUS" operation= "Profile_replace" profile= "unconfined" name= "/usr/lib/cups/backend/cups-pdf" pid=2171 comm= "  Apparmor_parser "05:55:05 ubuntu kernel: [39.322282] audit:type=1400 Audit (1535288105.459:63): apparmor=" STATUS " operation= "Profile_replace" profile= "unconfined" name= "/usr/sbin/cupsd" pid=2171 comm= "Apparmor_parser" 26 05:55:05 ubuntu kernel: [39.322809] Audit:type=1Audit (1535288105.459:64): apparmor= "STATUS" operation= "Profile_replace" profile= "unconfined" Name= "/usr/sbin/ CUPSD "pid=2171 comm=" Apparmor_parser "06:15:14 ubuntu kernel: [1248.118385] hello:module verification Failed:sig Nature and/or required key missing-tainting Kernelaug 06:15:14 ubuntu kernel: [1248.121354] Hello kernel, it ' s 2014! 06:16:13 ubuntu kernel: [1306.921227] Bye, kernel!  [email protected]:~/desktop#

Problems that arise
1. The IDE may not be able to find the # include <linux/kernel.h> etc header file
Yes, the include does not
This is okay because the kernel source to see the kernel version first

[email protected]:~/Desktop# uname -r4.2.0-27-generic[email protected]:~/Desktop#

Use $ (shell uname-r) to write the makefile file again.

Linux Driver Development