第一个内核模块hello world

2023-08-25 17:51:58

1、源码树的下载和编译（只是研究内核模块的话，应该不需要源码树的）

下载很简单，压缩包解压

编译：make menuconfig

make bzImage -j4

参考

2、

cd /usr/src/linux-4.12.10/drivers/char

建立demo目录，用来存放自己的内核模块

demo目录下新建hello.c 和 Makefile文件

//hello.c

#include <linux/init.h>

#include <linux/module.h>

MODULE_LICENSE("Dual BSD/GPL");

static int hello_init(void)

{

    printk(KERN_ALERT "hello world!\n");

    return ;

}

static void hello_exit(void)

{

    printk(KERN_ALERT "goodbye!\n");

}

module_init(hello_init);

module_exit(hello_exit);

//Makefile

ifeq ($(KERNELRELEASE),)

KERNELDIR ?= /lib/modules/$(shell uname -r)/build

PWD := $(shell pwd)

modules:

    $(MAKE) -C $(KERNELDIR) M=$(PWD) modules

modules_install:

    $(MAKE) -C $(KERNELDIR) M=$(PWD) modules_install

clean:

    rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions Module* modules*

.PHONY: modules modules_install clean

else

obj-m := hello.o

endif

参考

编译结果：

ninjame@ubuntu1604:/usr/src/linux-4.12./drivers/char/demo$ sudo make

make -C /lib/modules/4.4.--generic/build  M=/usr/src/linux-4.12./drivers/char/demo modules

make[]: Entering directory '/usr/src/linux-headers-4.4.80-040480-generic'

  CC [M]  /usr/src/linux-4.12./drivers/char/demo/hello.o

  Building modules, stage .

  MODPOST  modules

  CC      /usr/src/linux-4.12./drivers/char/demo/hello.mod.o

  LD [M]  /usr/src/linux-4.12./drivers/char/demo/hello.ko

make[]: Leaving directory '/usr/src/linux-headers-4.4.80-040480-generic'

模块加载和效果

ninjame@ubuntu1604:/usr/src/linux-4.12./drivers/char/demo$ sudo insmod hello.ko

ninjame@ubuntu1604:/usr/src/linux-4.12./drivers/char/demo$ dmesg | tail

[   15.300169] r8169 ::00.0 enp1s0: link down

[   15.300185] r8169 ::00.0 enp1s0: link down

[   15.300230] IPv6: ADDRCONF(NETDEV_UP): enp1s0: link is not ready

[   16.840866] r8169 ::00.0 enp1s0: link up

[   16.840873] IPv6: ADDRCONF(NETDEV_CHANGE): enp1s0: link becomes ready

[   18.016626] Bluetooth: BNEP (Ethernet Emulation) ver 1.3

[   18.016628] Bluetooth: BNEP filters: protocol multicast

[   18.016631] Bluetooth: BNEP socket layer initialized

[12219.748060] hello: module verification failed: signature and/or required key missing - tainting kernel

[12219.748268] hello world!

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