Linux编译模块问题

我的Linux版本是Redhat enterprise 2.6内核

    以为主要参考

    最简单的模块hello.c

    /hello.c

    #include

    #include

    MODULE_LICENSE("Dual BSD/GPL");

    static int hello_init(void)

    {

     printk(KERN_ALERT "Hello, worldn");

     return 0;

    }

    static void hello_exit(void)

    {

     printk(KERN_ALERT"Goodbye, cruel worldn");

    }

    module_init(hello_init);

    module_exit(hello_exit);

    编译模块

    内核代码在/usr/src/kernels/2.6.9-42.EL-smp-x86_64/下面

    也存在于/lib/modules/2.6.9-42.ELsmp/build/

    1,Makefile 文件

     obj-m :=hello.o

     再直接运行

     make -C /usr/src/kernels/2.6.9-42.EL-smp-x86_64/ SUBDIRS=$PWD modules

     得到结果

    make: Entering directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

     CC [M] /root/luckyball/device/hello.o

     Building modules, stage 2.

     MODPOST

     CC /root/luckyball/device/hello.mod.o

     LD [M] /root/luckyball/device/hello.ko

    make: Leaving directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

    生成结果

    [root@localhost device]# ls

    hello.c hello.ko hello.mod.c hello.mod.o hello.o Makefile

    2,Makefile 文件于上面一样

     运行

    make -C /lib/modules/2.6.9-42.ELsmp/build/ SUBDIRS=$PWD modules

    得到运行结果

    make: Entering directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

     CC [M] /root/luckyball/device/hello.o

     Building modules, stage 2.

     MODPOST

     CC /root/luckyball/device/hello.mod.o

     LD [M] /root/luckyball/device/hello.ko

    make: Leaving directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

    可见两个内核代码是相关联的

    生成结果 同上

    3,直接写Makefile 文件

     1 ifneq ($(KERNElRELEASE),)

     2 obj-m := hello.o

     3 else

     4 obj-m := hello.o

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

     6 PWD := $(shell pwd)

     7

     8 default:

     9 $(MAKE) -C $(KERNELDIR) SUBDIRS=$(PWD) modules

     10 endif

    其中/lib/modules/$(shell uname -r)/build 就是上面的

     /lib/modules/2.6.9-42.ELsmp/build/

    得到运行结果

     make -C /lib/modules/2.6.9-42.ELsmp/build SUBDIRS=/root/luckyball/device modulesmake[1]: Entering directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

     CC [M] /root/luckyball/device/hello.o

     Building modules, stage 2.

     MODPOST

     CC /root/luckyball/device/hello.mod.o

     LD [M] /root/luckyball/device/hello.ko

    make[1]: Leaving directory `/usr/src/kernels/2.6.9-42.EL-smp-x86_64'

    生成结果通上

     注意: Makefile文件中的4行,是中没有的,我认为必需加,且我的实践证明也必需加

     if ,else 两个独立的语句,都应该运行obj-m :=hello.o,即说明有一个模块需要从目标文件

     hello.o构造,且名字为hello.ko.

    装载和卸载模块

    insmod ./hello.ko

    rmmod hello

    

    如果不能在终端打印消息,可以/var/log/syslog查看,也可以修改printk优先级使其在终端上先是,参看

     31 #define KERN_EMERG "" /* system is unusable */

     32 #define KERN_ALERT "" /* action must be taken immediately */

     33 #define KERN_CRIT "" /* critical conditions */

     34 #define KERN_ERR "" /* error conditions */

     35 #define KERN_WARNING "" /* warning conditions */

     36 #define KERN_NOTICE "" /* normal but significant condition */

     37 #define KERN_INFO "" /* informational */

     38 #define KERN_DEBUG "" /* debug-level messages */

    把KERN_ALERT 改成 KERN_EMERG

    问题自然就解决了!