The Linux Networking Architecture [Electronic resources] نسخه متنی

Appendix D. Example for a Kernel Module

/**********************************************************
* Example of a kernel module
* Compile:
* gcc -I/lib/modules/'uname -r'/build/include -c module.c
**********************************************************/
#ifndef _KERNEL_
#define _KERNEL_
#endif
#ifndef MODULE
#define MODULE
#endif
#ifndef EXPORT_SYMTAB
#define EXPORT_SYMTAB
#endif
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/proc_fs.h>
MODULE_AUTHOR("Test Author (klaus@Linux-netzwerkarchitektur.de)");
MODULE_DESCRIPTION("This is an example module for the book
Linux Network Architecture.");
/*****************************************/
/* Example variables for module parameters */
/*****************************************/
unsigned int variable1;
unsigned long variable2[3] = {0,1,2};
/* Example function; will be exported as symbol. */
void methode1(int test1, char *test2)
{
// do anything
}

EXPORT_SYMBOL (variable1);
EXPORT_SYMBOL (variable2);
EXPORT_SYMBOL (methode1);
MODULE_PARM (variable1, "i");
MODULE_PARM_DESC (variable1, "Description for the integer");
MODULE_PARM (variable2, "1-3l");
MODULE_PARM_DESC (variable2, "Description for the array of longs");
/*******************************************************/
/* Function to create the output from proc files. */
/*******************************************************/
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *test_dir, *entry;
int test_proc_get_info(char *buf, char **start, off_t offset, int len)
{
len = sprintf(buf, "\n This is a test module\n\n");
len += sprintf(buf+len, " Integer: %u\n", variable1);
len += sprintf(buf+len, " Long[0]: %lu\n", variable2[0]);
len += sprintf(buf+len, " Long[1]: %lu\n", variable2[1]);
len += sprintf(buf+len, " Long[2]: %lu\n", variable2[2]);
return len;
}
int test_proc_read(char *buf, char **start, off_t off, int count, int *eof, void *data)
{
unsigned int       *ptr_var1 = data;
return sprintf(buf, "%u\n", *ptr_var1);
}
int test_proc_write(struct file *file, const char *buffer, unsigned long count, void *data)
{
unsigned int      *ptr_var1 = data;
printk(KERN_DEBUG "TEST: variable1 set to: %s", buffer);
*ptr_var1 = simple_strtoul(buffer, NULL, 10);
return count;
}
register_proc_files()
{
test_dir = proc_mkdir("test_dir", &proc_root);
if (!create_proc_info_entry("test", 0444, test_dir, test_proc_get_info))
printk(KERN_DEBUG "TEST: Error creating /proc/test.");
entry = create_proc_entry("test_rw", 0644, test_dir);
entry->nlink = 1;
entry->data = (void *) &variable1;
      entry->read_proc = test_proc_read;
entry->write_proc = test_proc_write;
}
unregister_proc_files()
{
remove_proc_entry("test", test_dir);
remove_proc_entry("test_rw", test_dir);
remove_proc_entry("test_dir", NULL);
}
#endif /* CONFIG_PROC_FS */
/**************************************/
/* Initialization function of the module */
/**************************************/
int skull_init(void)
{
/* Register the functionality of the module, */
/* e.g., register_netdevice, inet_add_protocol, dev_add_pack, etc. */
#ifdef CONFIG_PROC_FS
register_proc_files();
#endif /* CONFIG_PROC_FS */
return 0;
}
/*********************************************/
/* Function to clean up the module context */
/*********************************************/
void skull_cleanup(void)
{
/* Unregister the functionality of the module, */
/* e.g., unregister_netdevice, inet_del_protocol, dev_remove_pack, etc. */
#ifdef CONFIG_PROC_FS
unregister_proc_files();
#endif /* CONFIG_PROC_FS */
}
/* Alternative function names for init_module() and cleanup_module() */
module_init(skull_init);
module_exit(skull_cleanup);