LINUX module stack technology and multi-ko Compilation

The lsmod command in the driver actually reads the/proc/modules file.
That is, the result corresponding to the lsmod command is cat/proc/modules.

Information about the loaded modules in the kernel exists in the/sys/Module Directory.

The modprobe command is more powerful than the insmod command. When a module is loaded, it loads other modules that the module depends on at the same time.
Use modprobe-r filename to uninstall the modules that are dependent on at the same time.
Modinfo Module name command to obtain module information
Modinfo hello. Ko

Filename: Hello. Ko
Alias: a simplest Module
Description: a simple hello World module
Author: Jimmy
License: Dual BSD/GPL
Srcversion: fc20e540c350c6f733c7546
Depends:
Vermagic: 2.6.28-15-genericsmp mod_unload modversions 586

Driver Module parameters, module_parm_desc can be annotated with Parameters
For example:
Static int num = 4000;
Module_param (Num, Int, s_irugo );
Module_parm_desc (myshort, "a integer ");

# Include <Linux/init. h>
# Include <Linux/module. h>

Module_license ("dual BSD/GPL ");

Static char * book_name = "dissecting Linux Device Driver ";
Static int num = 4000;
Static int Param [8] = {1, 2, 3, 4, 5, 6, 7, 8 };
Static int param_len = 8;

Static int book_init (void)
{
Int I;
Printk (kern_alert "bookname: % s/n", book_name );
Printk (kern_alert "booknum: % d/N", num );
For (I = 0; I <8; I ++)
{
Printk (kern_alert "Param [% d] = % d/N", I, Param [I]);
}

Return 0;
}

Static void book_exit (void)
{
Printk (kern_alert "bookmodule exit/N ");
}

Module_init (book_init );
Module_exit (book_exit );
Module_param (Num, Int, s_irugo );
Module_param (book_name, CHARP, s_irugo );
Module_param_array (Param, Int, & param_len, s_irugo );

Module_author ("Jimmy, fightingjimmy@gmail.com ");
Module_description ("A simple module for testing module Params ");
Module_version ("V1.0 ");

Sudo insmod book. Ko
Dmesg | tail-10
[2, 14047.901352] book name: Dissecting Linux Device Driver
[14047.901366] Book num: 4000
[14047.901377] Param [0] = 1
[2, 14047.901386] Param [1] = 2
[2, 14047.901388] Param [2] = 3
[2, 14047.901389] Param [3] = 4
[1, 14047.901390] Param [4] = 5
[1, 14047.901391] Param [5] = 6
[2, 14047.901392] Param [6] = 7
[2, 14047.901393] Param [7] = 8

Sudo rmmod book. Ko
Sudo insmod book. Ko book_name = 'hello' num = 1000 Param =, 6, 5
[2, 14298.942521] book name: Hello
[14298.942535] Book num: 1000
[1, 14298.942547] Param [0] = 8
[1, 14298.942558] Param [1] = 7
[1, 14298.942559] Param [2] = 6
[2, 14298.942560] Param [3] = 5
[1, 14298.942561] Param [4] = 5
[1, 14298.942562] Param [5] = 6
[2, 14298.942564] Param [6] = 7
[2, 14298.942565] Param [7] = 8

Sudo rmmod book. Ko
Sudo insmod book. Ko book_name = "Hello World" num = 1000 Param = 8, 7, 6, 5
Insmod: Error inserting 'book. ko':-1 unknown symbol in Module

Dmesg | tail-10
[2, 15097.587159] Book: Unknown Parameter 'World'
Conjecture: it may be because the input string parameters contain spaces (please do not hesitate to inform us if you encounter similar situations)

The/proc/kallsyms file of linux2.6 corresponds to the kernel symbol table, which records and the memory address of the symbol.
Export_symbol (symbol name );
Exprot_symbol_gpl (symbol name );

Module/
Include/
Print. h
Print/
Print. c
Makefile
Symbol/
Test. c
Makefile

/*************************************** *
* Print. H *
**************************************** */
# Ifndef print_h
# Define print_h

Void add_integer (int A, int B );
Void sub_integer (int A, int B );

# Endif

/*************************************** *
* Print. C *
**************************************** */
# Include <Linux/init. h>
# Include <Linux/module. h>

# Include "print. H"

Module_license ("dual BSD/GPL ");

Void add_integer (int A, int B)
{
Printk (kern_alert "sum: % d/N", A + B );
}

Void sub_integer (int A, int B)
{
Printk (kern_alert "Sub: % d/N", A-B );
}

Export_symbol (add_integer );
Export_symbol (sub_integer );

/*************************************** *
* Test. C *
**************************************** */
# Include <Linux/init. h>
# Include <Linux/module. h>

# Include "print. H"

Module_license ("GPL ");

Static int symbol_init (void)
{
Printk (kern_alert "symboltest init/N ");
Add_integer (10, 6 );
Sub_integer (10, 6 );
Return 0;
}

Static void symbol_exit (void)
{
Printk (kern_alert "symboltest exit/N ");
}

Module_init (symbol_init );
Module_exit (symbol_exit );

Makefile in the print directory:
OBJ-M: = print. o
Kerneldir? =/Lib/modules/$ (shell uname-R)/build
PWD: = $ (shell PWD)
Print_inc = $ (OBJ)/../include # contains the print. h header file
Extra_cflags + =-I $ (print_inc)

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

. Phony: modules modules_install clean

Makefile in the symbol directory:
OBJ-M: = test. o
Kerneldir? =/Lib/modules/$ (shell uname-R)/build
PWD: = $ (shell PWD)
Symbol_inc = $ (OBJ)/../include
Extra_cflags + =-I $ (symbol_inc)
Kbuild_extra_symbols = $ (OBJ)/../print/module. symvers

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

. Phony: modules modules_install clean

Note: If the MAKEFILE file does not contain kbuild_extra_symbols = $ (OBJ)/../print/module. symvers
Copy module. symvers under the print directory to the symbol directory.
Kernel Versions later than 2.6.26 bug (For details, please refer to the http://bugzilla.kernel.org/show_bug.cgi? Id = 12446)

Compile insmod separately.