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Editor to share with you the Linux kernel device driver Linux kernel module loading mechanism example analysis, I believe that most people do not know much about it, so share this article for your reference, I hope you will learn a lot after reading this article, let's learn about it!

# include

1. Module parameters

Define variables in the driver

Static int num = 0; / / 0 when the load module does not specify a value for num

Module_param (variable name, type, permission); type: byte, int, uint, short, ushort, long, ulong, bool, charp, permission cannot have write permission

Pass parameter: insmod test.ko variable name 1 = value 1 variable name 2 = value 2

The calling relationship of module_param is as follows:

# define module_param (name, type, perm)\ module_param_named (name, name, type, perm) # define module_param_named (name, value, type, perm)\ param_check_##type (name, & (value));\ module_param_call (name, param_set_##type, param_get_##type, & value, perm) \ _ MODULE_PARM_TYPE (name, # type) # define module_param_call (name, set, get, arg, perm)\ _ module_param_call (MODULE_PARAM_PREFIX,\ name, set, get, arg,\ _ same_type (* (arg), bool), perm) # define _ module_param_call (prefix, name, set, get, arg, isbool Perm)\ static int _ _ param_perm_check_##name _ attribute__ ((unused)) =\ BUILD_BUG_ON_ZERO ((perm))

0777 | | (perm) & 2)\ + BUILD_BUG_ON_ZERO (sizeof ("" prefix) > MAX_PARAM_PREFIX_LEN);\ static const char _ _ param_str_##name [] = prefix # name \ static struct kernel_param _ moduleparam_const _ param_##name\ _ used\ _ attribute__ ((unused,__section__ ("_ param"), aligned (sizeof (void *)\ = {_ param_str_##name, perm, isbool? KPARAM_ISBOOL: 0,\ set, get, {arg}}

Multiple c files are compiled into a module, which can be implemented using the instruction in xxx-objs, the Makefile, as follows:

Test-objs: = a.o b.o / / compiled into test.ko by A.C, b.c. Note that no .o file can have the same name as the target ko file obj-m + = test.o

You can view the module's information on the system under / sys/module/ module name /

1. View information about elf files

Readelf test.ko-a

Ko file composition

1. Elf file header

2. Text data...

3. Sections table

4. Symbol table

2. EXPORT_SYMBOL (function name / variable address) / / Export the address of the function / or variable to the kernel symbol table

EXPORT_SYMBOL_GPL (function name) /

/ proc/kallsyms view the symbol table of the current system

The above is all the contents of the article "sample Analysis of Linux Kernel Module loading Mechanism for Linux Kernel device drivers". Thank you for reading! I believe we all have a certain understanding, hope to share the content to help you, if you want to learn more knowledge, welcome to follow the industry information channel!

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