florian@florian-pc:~/module$ cat main.c

#include<linux/module.h>

#include<linux/init.h>

static int __init init(void)

{

printk("Hi module!\n");

return 0;

}

static void __exit exit(void)

{

printk("Bye module!\n");

}

module_init(init);

module_exit(exit);

florian@florian-pc:~/module$ cat Makefile

obj-m += main.o

#generate the path

CURRENT_PATH:=$(shell pwd)

#the current kernel version number

LINUX_KERNEL:=$(shell uname -r)

#the absolute path

LINUX_KERNEL_PATH:=/usr/src/linux-headers-$(LINUX_KERNEL)

#complie object

all:

make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) modules

#clean

clean:

make -C $(LINUX_KERNEL_PATH) M=$(CURRENT_PATH) clean

florian@florian-pc:~/module$ make

make -C /usr/src/linux-headers-2.6.35-22-generic M=/home/florian/module modules

make[1]: 正在进入目录 `/usr/src/linux-headers-2.6.35-22-generic'

Building modules, stage 2.

MODPOST 1 modules

make[1]:正在离开目录 `/usr/src/linux-headers-2.6.35-22-generic'

florian@florian-pc:~/module$ sudo insmod main.ko;dmesg | tail -1

[31077.810049] Hi module!

florian@florian-pc:~/module$ sudo rmmod main.ko;dmesg | tail -1

[31078.960442] Bye module!

florian@florian-pc:~/module$ readelf -h main.ko

ELF Header:

Magic:   7f 45 4c 46 01 01 01 00 00 00 00 00 00 00 00 00

Class:                             ELF32

Data:                              2's complement, little endian

Version:                           1 (current)

OS/ABI:                            UNIX - System V

ABI Version:                       0

Type:                              REL (Relocatable file)

Machine:                           Intel 80386

Version:                           0x1

Entry point address:               0x0

Start of program headers:          0 (bytes into file)

Start of section headers:          1120 (bytes into file)

Flags:                             0x0

Size of this header:               52 (bytes)

Size of program headers:           0 (bytes)

Number of program headers:         0

Size of section headers:           40 (bytes)

Number of section headers:         19

Section header string table index: 16

linux3.5.2/kernel/module.h:220

struct module

{

……

/* Startup function. */

int (*init)(void);

……

/* Destruction function. */

void (*exit)(void);

……

};

linux3.5.2/kernel/module.c:3009

/* This is where the real work happens */

SYSCALL_DEFINE3(init_module, void __user *, umod,

unsigned long, len, const char __user *, uargs)

{

struct module *mod;

int ret = 0;

……

/* Do all the hard work */

mod = load_module(umod, len, uargs);//模块加载

……

/* Start the module */

if (mod->init != NULL)

ret = do_one_initcall(mod->init);//模块init函数调用

……

return 0;

}

linux3.5.2/kernel/module.c:2864

/* Allocate and load the module: note that size of section 0 is always

zero, and we rely on this for optional sections. */

static struct module *load_module(void __user *umod,

unsigned long len,

const char __user *uargs)

{

struct load_info info = { NULL, };

struct module *mod;

long err;

……

/* Copy in the blobs from userspace, check they are vaguely sane. */

err = copy_and_check(&info, umod, len, uargs);//拷贝到内核

if (err)

return ERR_PTR(err);

/* Figure out module layout, and allocate all the memory. */

mod = layout_and_allocate(&info);//地址空间分配

if (IS_ERR(mod)) {

err = PTR_ERR(mod);

goto free_copy;

}

……

/* Fix up syms, so that st_value is a pointer to location. */

err = simplify_symbols(mod, &info);//符号解析

if (err < 0)

goto free_modinfo;

err = apply_relocations(mod, &info);//重定位

if (err < 0)

goto free_modinfo;

……

}

linux3.5.2/kernel/init.c:673

int __init_or_module do_one_initcall(initcall_t fn)

{

int count = preempt_count();

int ret;

if (initcall_debug)

ret = do_one_initcall_debug(fn);

else

ret = fn();//调用init module

……

return ret;

}

linux3.5.2/kernel/module.c:768

SYSCALL_DEFINE2(delete_module, const char __user *, name_user,

unsigned int, flags)

{

struct module *mod;

char name[MODULE_NAME_LEN];

int ret, forced = 0;

……

/* Final destruction now no one is using it. */

if (mod->exit != NULL)

mod->exit();//调用exit module

……

free_module(mod);//卸载模块

……

}