2 hello world 内核模块

学习《linux内核模块编程指南》第2章节 hello world 内核模块

在2.2章节 编译内核模块 hello附件： hello.rar   将rar修改为rar

1. 当在init_module初始化函数中，返回非0，函数初始化失败，模块加载失败

如：

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

加载模块后显示如下：

ywx@ywx:~/Desktop/module/hello$ dmesg | tail -3
[ 3626.517217] hello, world
[ 3626.517633] print_hello
[ 3630.949706] bye, world

如果，我将hello_init返回值，修改为非0，那么在编译成模块后，不能正常加载模块，错误如下显示

static int hello_init(void)
{
        printk(KERN_ALERT "hello, world\n");
        return 1;
}

ywx@ywx:~/Desktop/module/hello$ dmesg | tail -8
[ 3670.816134] sys_init_module: 'hello'->init suspiciously returned 1, it should follow 0/-E convention 加载失败
[ 3670.816136] sys_init_module: loading module anyway...
[ 3670.816253] Pid: 3372, comm: insmod Not tainted 2.6.35-31-generic #63-Ubuntu
[ 3670.816307] Call Trace:
[ 3670.816885]  [<c05c95a1>] ? printk+0x2d/0x34
[ 3670.817047]  [<c0181905>] sys_init_module+0x1d5/0x1e0
[ 3670.817078]  [<c05cc204>] syscall_call+0x7/0xb
[ 3680.924736] bye, world

=============

2.4章节 __init __exit __initdata 宏

宏__initdata同__init类似，只不过对变量有效

static int hello_data __initdata = 3;

static int hello_init(void)
{
        printk(KERN_ALERT "hello, world hello_data=%d\n",hello_data);
        return 0;
}

========

2.6从命令行传递参数给内核模块

附件； hello.rar   将rar修改为tar.bz2

#include <linux/init.h>//__init __exit __initdata
#include <linux/module.h>//MODULE_LICENSE
#include <linux/kernel.h>//printk
#include <linux/moduleparam.h>//module_param
#include <linux/stat.h>//S_IRUGSR

static int hello_data __initdata = 3;

static int howmany = 1;
static char *whom = "apologize";

module_param(howmany,int,00444);//S_IRUGO=00444
module_param(whom,charp,S_IRUGO);//char point
//bool,invbool,charp,int,long,short,uint ulong ushort
//module_param(name,type,num,perm);

static int hello_init(void)
{
        printk(KERN_ALERT "hello, world hello_data=%d\n",hello_data);
        printk("howmany=%d\n",howmany);
        printk("whom=%s\n",whom);
        return 0;
}

显示如下：

ywx@ywx:~/Desktop/module/hello$ sudo insmod ./hello.ko howmany=123 whom="jj"
ywx@ywx:~/Desktop/module/hello$ sudo rmmod hello
ywx@ywx:~/Desktop/module/hello$ dmesg | tail - 4
[ 8375.884555] hello, world hello_data=3
[ 8375.884581] howmany=123
[ 8375.884597] whom=jj
[ 8385.706078] bye, world