Ори Померанц - Энциклопедия разработчика модулей ядра Linux

if (*Message_Ptr == 0) return 0;

/* Actually put the data into the buffer */

while (length && *Message_Ptr) {

/* Because the buffer is in the user data segment,

* not the kernel data segment, assignment wouldn't

* work. Instead, we have to use put_user which

* copies data from the kernel data segment to the

* user data segment. */

put_user(*(Message_Ptr++), buffer++);

length--;

bytes_read++;

}

#ifdef DEBUG

printk("Read %d bytes, %d left\n", bytes_read, length);

#endif

/* Read functions are supposed to return the number

* of bytes actually inserted into the buffer */

return bytes_read;

}

/* This function is called when somebody tries to write into our device file. */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

static ssize_t device_write(struct file *file, const char *buffer, size_t length, loff_t *offset)

#else

static int device_write(struct inode *inode, struct file *file, const char *buffer, int length)

#endif

{

int i;

#ifdef DEBUG

printk("device_write(%p,%s,%d)", file, buffer, length);

#endif

for(i=0; i

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

get_user(Message[i], buffer+i);

#else

Message[i] = get_user(buffer+i);

#endif

Message_Ptr = Message;

/* Again, return the number of input characters used */

return i;

}

/* This function is called whenever a process tries to

* do an ioctl on our device file. We get two extra

* parameters (additional to the inode and file

* structures, which all device functions get): the number

* of the ioctl called and the parameter given to the ioctl function.

*

* If the ioctl is write or read/write (meaning output

* is returned to the calling process), the ioctl call

* returns the output of this function. */

int device_ioctl(struct inode *inode, struct file *file,

unsigned int ioctl_num, /* The number of the ioctl */

unsigned long ioctl_param) /* The parameter to it */

{

int i;

char *temp;

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

char ch;

#endif

/* Switch according to the ioctl called */

switch (ioctl_num) {

case IOCTL_SET_MSG:

/* Receive a pointer to a message (in user space)

* and set that to be the device's message. */

/* Get the parameter given to ioctl by the process */

temp = (char*)ioctl_param;

/* Find the length of the message */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

get_user(ch, temp);

for (i=0; ch && i

#else

for (i=0; get_user(temp) && i

#endif

/* Don't reinvent the wheel - call device_write */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

device_write(file, (char*)ioctl_param, i, 0);

#else

device_write(inode, file, (char*)ioctl_param, i);

#endif

break;

case IOCTL_GET_MSG:

/* Give the current message to the calling

* process - the parameter we got is a pointer, fill it. */

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

i = device_read(file, (char*)ioctl_param, 99, 0);

#else

i = device_read(inode, file, (char*)ioctl_param, 99);

#endif

/* Warning - we assume here the buffer length is

* 100. If it's less than that we might overflow

* the buffer, causing the process to core dump.

*

* The reason we only allow up to 99 characters is

* that the NULL which terminates the string also needs room. */

/* Put a zero at the end of the buffer, so it will be properly terminated */

put_user('\0', (char*)ioctl_param+i);

break;

case IOCTL_GET_NTH_BYTE:

/* This ioctl is both input (ioctl_param) and

* output (the return value of this function) */

return Message[ioctl_param];

break;

}

return SUCCESS;

}

/* Module Declarations *************************** */

/* This structure will hold the functions to be called

* when a process does something to the device we

* created. Since a pointer to this structure is kept in

* the devices table, it can't be local to

* init_module. NULL is for unimplemented functions. */

struct file_operations Fops = {

NULL, /* seek */

device_read,

device_write,

NULL, /* readdir */

NULL, /* select */

device_ioctl, /* ioctl */

NULL, /* mmap */

device_open,

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2,2,0)

NULL, /* flush */

#endif

device_release /* a.k.a. close */

};

/* Initialize the module - Register the character device */

int init_module() {

int ret_val;

/* Register the character device (atleast try) */

ret_val = module_register_chrdev(MAJOR_NUM, DEVICE_NAME, &Fops);

/* Negative values signify an error */

if (ret_val < 0) {

printk("%s failed with %d\n", "Sorry, registering the character device ", ret_val);

return ret_val;

}

printk("%s The major device number is %d.\n", "Registeration is a success", MAJOR_NUM);

printk("If you want to talk to the device driver,\n");

printk ("you'll have to create a device file. \n");

printk ("We suggest you use:\n");

printk ("mknod %s c %d 0\n", DEVICE_FILE_NAME, MAJOR_NUM);

printk ("The device file name is important, because\n");

printk ("the ioctl program assumes that's the\n");

printk ("file you'll use.\n");

return 0;

}

/* Cleanup - unregister the appropriate file from /proc */

void cleanup_module() {

int ret;

/* Unregister the device */

ret = module_unregister_chrdev(MAJOR_NUM, DEVICE_NAME);

/* If there's an error, report it */

if (ret < 0) printk("Error in module_unregister_chrdev: %d\n", ret);

}

/* chardev.h - the header file with the ioctl definitions.

*

* The declarations here have to be in a header file,

* because they need to be known both to the kernel

* module (in chardev.c) and the process calling ioctl (ioctl.c)

*/

#ifndef CHARDEV_H

#define CHARDEV_H #

include

/* The major device number. We can't rely on dynamic

* registration any more, because ioctls need to know it. */

#define MAJOR_NUM 100

/* Set the message of the device driver */

#define IOCTL_SET_MSG _IOR(MAJOR_NUM, 0, char *)

/* _IOR means that we're creating an ioctl command

* number for passing information from a user process

* to the kernel module.

*

* The first arguments, MAJOR_NUM, is the major device

* number we're using.

*

* The second argument is the number of the command

* (there could be several with different meanings).

*

* The third argument is the type we want to get from

* the process to the kernel. */

/* Get the message of the device driver */

#define IOCTL_GET_MSG _IOR(MAJOR_NUM, 1, char *)

/* This IOCTL is used for output, to get the message

* of the device driver. However, we still need the

* buffer to place the message in to be input,

* as it is allocated by the process. */

/* Get the n'th byte of the message */

#define IOCTL_GET_NTH_BYTE _IOWR(MAJOR_NUM, 2, int)

/* The IOCTL is used for both input and output. It

* receives from the user a number, n, and returns Message[n]. */

/* The name of the device file */

#define DEVICE_FILE_NAME "char_dev"

#endif

/* ioctl.c - the process to use ioctl's to control the

* kernel module

*

* Until now we could have used cat for input and

* output. But now we need to do ioctl's, which require

* writing our own process. */

/* Copyright (C) 1998 by Ori Pomerantz */

/* device specifics, such as ioctl numbers and the major device file. */

#include "chardev.h"

#include /* open */

#include /* exit */

#include /* ioctl */

/* Functions for the ioctl calls */

ioctl_set_msg(int file_desc, char *message) {

int ret_val;

ret_val = ioctl(file_desc, IOCTL_SET_MSG, message);

if (ret_val < 0) {

printf("ioctl_set_msg failed:%d\n", ret_val);

exit(-1);

}

}

ioctl_get_msg(int file_desc) {

int ret_val;

char message[100];

/* Warning - this is dangerous because we don't tell

* the kernel how far it's allowed to write, so it

* might overflow the buffer. In a real production

* program, we would have used two ioctls - one to tell

* the kernel the buffer length and another to give

* it the buffer to fill */

ret_val = ioctl(file_desc, IOCTL_GET_MSG, message);

if (ret_val < 0) {

printf("ioctl_get_msg failed:%d\n", ret_val);