/home/osboxes/Documenti/AOSV/aosv1819-federicoalfano/session_module.h File Reference

The header of the main functions that allows the user a session-based file access semantic. More...

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/fdtable.h>
#include <linux/cdev.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/uaccess.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <linux/rbtree.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/dcache.h>
#include <linux/sched/signal.h>
#include <linux/file.h>
#include <linux/namei.h>
#include <linux/mount.h>

Go to the source code of this file.

Data Structures
struct	session_cdev
	The wrapper containing the char device used to manage sessions plus the kobject needed into the /sys to get info about the open sessions. More...
struct	session_file_node
	This is the structure into the rb_tree that contains all the open files with their counter. More...
struct	session_proc_node
	This is the structure into the rb_tree that contains all the processes which are currently using the sessions. More...
struct	session_priv_data
	This structure is linked to the original file through the field private_data and the main purpose is to keep the pointer to the session file. More...

Macros
#define	SESSION_MAJOR_NUMBER   0
#define	SESSION_BASE_MINOR   0
#define	MAX_FILENAME_SIZE   128
#define	MAX_PATH_SIZE   256
#define	MAX_FILE_NUM   256
#define	N_SESS_DIGITS   8
#define	N_PROC_DIGITS   6

Functions
int	session_release (struct inode *, struct file *)
	Closes the session related to filp, unlinking the temporary session node, it's called just after an unexpected close. The right way to close a session is with the SESSION_CLOSE from ioctl that replaces the file operations from the original file. More...
ssize_t	session_read (struct file *, char __user *, size_t, loff_t *)
	It reads is onto the session file, every concurrent change onto the original file between the session open and the session release are invisible to the read. More...
loff_t	session_llseek (struct file *, loff_t, int)
	It seeks the position into the session file. More...
ssize_t	session_write (struct file *, const char __user *, size_t, loff_t *)
	It writes only onto session file keeping immutate the original one. More...

Detailed Description

The header of the main functions that allows the user a session-based file access semantic.

Author

Federico Alfano

Date

2 May, 2020

Macro Definition Documentation

#define MAX_FILE_NUM   256

It indicates how many files can be represented, this macro is useful to indicate to the file_counter how many lines can show

#define MAX_FILENAME_SIZE   128

The maximum filename length, you can compile it with different values if you know the maximum length of your files

#define MAX_PATH_SIZE   256

The maximum length of the path

#define N_PROC_DIGITS   6

Indicates of how many digits the proc_counter can have, in other words are maximum number of digits needed to represent the number of per-process sessions

#define N_SESS_DIGITS   8

Indicates of how many digits the session_counter can have, (e.g. setting at 3, the subsystem cannot show more than 999 session)

#define SESSION_BASE_MINOR   0

This is the base minor, it's not critical as the driver is designed to work with just one instance

#define SESSION_MAJOR_NUMBER   0

The Major number of the driver if 0 it's chosen dynamically by the system, please change only if you know what you are doing

Function Documentation

loff_t session_llseek	(	struct file *	,
		loff_t	,
		int
	)

It seeks the position into the session file.

Parameters

filp	the file structure pointer referred by the call
off	the seek offset
whence	the seek method

Returns

returns the resulting offset location as measured in bytes from the beginning of the file or an error code

ssize_t session_read	(	struct file *	,
		char __user *	,
		size_t	,
		loff_t *
	)

It reads is onto the session file, every concurrent change onto the original file between the session open and the session release are invisible to the read.

Parameters

filp	the file structure pointer referred by the call
buff	the destination buffer with data to write
count	maximum number of bytes to read
offp	where the read has to start

Returns

return the number of bytes read or error code

int session_release	(	struct inode *	,
		struct file *
	)

Closes the session related to filp, unlinking the temporary session node, it's called just after an unexpected close. The right way to close a session is with the SESSION_CLOSE from ioctl that replaces the file operations from the original file.

Parameters

inodep	the inode structure pointer referred by the call
filp	the file structure pointer referred by the call

Returns

0 or error code

ssize_t session_write	(	struct file *	,
		const char __user *	,
		size_t	,
		loff_t *
	)

It writes only onto session file keeping immutate the original one.

Parameters

filp	the file structure pointer referred by the call
buff	the buffer containing the data to write
count	maximum number of bytes to write
offp	where the write has to start

Returns

the resulting offset location as measured in bytes from the beginning of the file or an error code