第2章 建立和运行模块

2.2. Hello World 模块

2.2.1 代码

//hello.c
//运行：insmod ./hello.ko
卸载：rmmod hello

//注意hello,world只能在控制台上显示,不能在SecureCRT上显示
#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 0;
}
static void hello_exit(void)
{

        printk(KERN_ALERT "Goodbye, cruel world\n");
}

module_init(hello_init);
module_exit(hello_exit);

2.2.2 Makefile

#Makefile
# If KERNELRELEASE is defined, we've been invoked from the
# kernel build system and can use its language.
ifneq ($(KERNELRELEASE),)
 obj-m := hello.o 
# Otherwise we were called directly from the command
# line; invoke the kernel build system.
else
 KERNELDIR ?= /lib/modules/$(shell uname -r)/build
 PWD := $(shell pwd) 
default:
 $(MAKE) -C $(KERNELDIR) M=$(PWD) modules
endif 

2.8. 模块参数

//hello.c,Makefile同上
//运行：insmod hello howmany=10 whom="Mom" 
                                               
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>

MODULE_LICENSE("Dual BSD/GPL");

static char *whom = "world";
static int howmany = 1;
module_param(howmany, int, S_IRUGO);
module_param(whom, charp, S_IRUGO);

static int hello_init(void)
{
	int i;
	for (i = 0; i < howmany; i++)
		printk(KERN_ALERT "(%d) Hello, %s\n", i, whom);
	return 0;
}

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

module_init(hello_init);
module_exit(hello_exit);