一、Linux內核樹配置及Hello word

環境說明

1. Dell T30 機器一臺
2. 操作系統 Ubuntu 18.04
3. 參考書《Linux Device Driver Third Edition》

構建源碼樹步驟

1. 查看當前系統版本

$ uname -a
Linux dell-PowerEdge-T30 5.0.0-31-generic #33~18.04.1-Ubuntu SMP Tue Oct 1 10:20:39 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

2. 查看系統中是否已經安裝了Kernel源碼

$ cd /usr/src
$ ls -l
total 24
drwxr-xr-x 25 root root 4096 Sep 25  2019 linux-headers-5.0.0-29
drwxr-xr-x  8 root root 4096 Sep 25  2019 linux-headers-5.0.0-29-generic
drwxr-xr-x 25 root root 4096 Oct  6  2019 linux-headers-5.0.0-31
drwxr-xr-x  8 root root 4096 Oct  6  2019 linux-headers-5.0.0-31-generic
drwxrwxr-x 30 root root 4096 Apr 26 22:26 linux-source-5.0.0
lrwxrwxrwx  1 root root   45 Feb 10 19:33 linux-source-5.0.0.tar.bz2 -> linux-source-5.0.0/linux-source-5.0.0.tar.bz2

在我的系統中已經存在了源代碼，因此無需重新安裝。如果系統中沒有源碼，那麼按下面步驟3進行安裝配置。

3. 如果系統中沒有源碼，可用以下面的命令進行安裝

$ apt-cache search linux-source
linux-source - Linux kernel source with Ubuntu patches
linux-source-4.15.0 - Linux kernel source for version 4.15.0 with Ubuntu patches
linux-source-4.18.0 - Linux kernel source for version 4.18.0 with Ubuntu patches
linux-source-5.0.0 - Linux kernel source for version 5.0.0 with Ubuntu patches
linux-source-5.3.0 - Linux kernel source for version 5.3.0 with Ubuntu patches
linux-source-3.13.0 - Linux kernel source for version 3.13.0 with Ubuntu patches
$ sudo apt-get install linux-source-5.0.0

如果安裝成功，在/usr/src目錄下會看到一個linux-source-5.0.0.tar.bz2壓縮包，解壓：

$ sudo tar jxvf linux-source-5.0.0.tar.bz2

在/usr/src目錄下會看到linux-source-5.0.0文件夾，這就是我們需要的源碼樹。

4. 進入源碼目錄 linux-source-5.0.0

$ sudo make menuconfig
$ sudo make oldconfig 
$ sudo make modules
$ sudo make modules_install

源碼樹構建完成，重啓系統。

開始第一個Hello word驅動程序

1. 編碼hello.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/sched.h>

// 許可證(必要)
MODULE_LICENSE("Dual BSD/GPL");
// 模塊作者
MODULE_AUTHOR("Kama Li");
// 簡短描述
MODULE_DESCRIPTION("First driver module.");
// 模塊版本
MODULE_VERSION("1.0.1");
// 模塊別名
MODULE_ALIAS("Hello world");

void currentInfo(void)
{
    printk(KERN_INFO "The process is \"%s\" (pid %i) (CPU %d)\n", current->comm, current->pid, smp_processor_id());
    printk(KERN_INFO "in_irq() = %ld, in_interrupt() = %ld\n", in_irq(), in_interrupt());
}

static int hello_init(void)
{
    printk(KERN_ALERT "Hello, world\n");
    currentInfo();
    return 0;
}

static void hello_exit(void)
{
    printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init);
module_exit(hello_exit);

2. 編碼makefile

ifneq ($(KERNELRELEASE),)
	mymodule-bojs := hello.o
	obj-m := hello.o
else
	PWD := $(shell pwd)
	KERNELDIR = /lib/modules/$(shell uname -r)/build
all:
	$(MAKE) -C $(KERNELDIR) M=$(PWD) 
clean:
	rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c
endif

3. 編譯及測試

$ make
$ sudo insmod hello.ko

4. 查看kernel打印出來的log

$ sudo cat /var/log/syslog
Apr 26 22:22:19 dell-PowerEdge-T30 kernel: [20733.002512] Goodbye, cruel world
Apr 26 22:22:27 dell-PowerEdge-T30 kernel: [20740.842238] Hello, world
Apr 26 22:22:27 dell-PowerEdge-T30 kernel: [20740.842240] The process is "insmod" (pid 25112) (CPU 1)
Apr 26 22:22:27 dell-PowerEdge-T30 kernel: [20740.842241] in_irq() = 0, in_interrupt() = 0
$ sudo rmmod hello
$ sudo cat /var/log/syslog
Apr 26 22:23:43 dell-PowerEdge-T30 gnome-shell[1663]: [AppIndicatorSupport-WARN] Attempting to re-register :1.6/StatusNotifierItem; resetting instead
Apr 26 22:23:43 dell-PowerEdge-T30 gnome-shell[1663]: [AppIndicatorSupport-WARN] Item :1.6/StatusNotifierItem is already registered
Apr 26 22:24:10 dell-PowerEdge-T30 kernel: [20844.122386] Goodbye, cruel world

補充：查看系統日誌，還可以用

$sudo dmesg
[20528.821058] Hello, world
[20528.821060] The process is "insmod" (pid 18391) (CPU 1)
[20528.821061] in_irq() = 0, in_interrupt() = 0
[20733.002512] Goodbye, cruel world
[20740.842238] Hello, world
[20740.842240] The process is "insmod" (pid 25112) (CPU 1)
[20740.842241] in_irq() = 0, in_interrupt() = 0
[20844.122386] Goodbye, cruel world

到此，驅動開發環境算是完成了。