// Hello. C # DEFINE _ no_version _ # include <Linux/module. h>
# Include <Linux/config. h>
# Include <Linux/version. h>
# Include <ASM/uaccess. h>
# Include <Linux/init. h>
# Include <Linux/module. h>
# Include <Linux/kernel. h>
# Include <Linux/fs. h>
# Include <Linux/sched. h>
# Include <Linux/mm. h>
# Include <ASM/page. h>
# Include <Linux/poll. h>
# Include <Linux/kdev_t.h>
# Include <ASM/semaphore. h>
# Include <Linux/slab. h>
# Include <Linux/delay. h>
# Include <ASM/uaccess. h>
# Include <ASM/IRQ. h>
# Include <Linux/interrupt. h>
# Include <Linux/spinlock. h>
Unsigned int test_major = 0;
Static int global_var = 0;
Static int globalvar_count = 0;
Char * mystr = "wodeshen ";
Static struct semaphore SEM;
Static spinlock_t spin = spin_lock_unlocked; // macro definition static ssize_t read_test (struct file * file, char * Buf, size_t count, loff_t * f_pos) has been initialized)
{
Int left;
Printk (kern_info "read_test/N ");
If (verify_area (verify_write, Buf, count) =-efault)
Return-efault; If (down_interruptible (& SEM ))
{
Return-erestartsys;
}
Printk ("copy_to_user ======= 2 =========/N ");
Copy_to_user (BUF, mystr, strlen (mystr ));
/*
For (Left = count; left> 0; left --)
{
_ Put_user ('1', Buf );
Buf ++;
}
*/
Up (& SEM );
// Return sizeof (INT );
Return strlen (mystr );
} Static ssize_t write_test (struct file * file, const char * Buf, size_t count, loff_t * f_pos)
{If (down_interruptible (& SEM ))
{
Return-erestartsys;
}
If (copy_from_user (& global_var, Buf, sizeof (INT )))
{
Up (& SEM );
Return-efault;
}
Up (& SEM );
Printk (kern_info "write_test/N ");
Return sizeof (INT );
} Static int open_test (struct inode * inode, struct file * file ){
Spin_lock (& spin );
Printk ("globalvar open/N ");
// Critical resource access
If (globalvar_count)
{
Spin_unlock (& spin );
Return-ebusy;
}
Globalvar_count ++; // release the selected lock
Spin_unlock (& spin );
Printk (kern_info "open_test/N ");
Mod_inc_use_count;
Return 0;
} Static int release_test (struct inode * inode, struct file * file)
{
Printk (kern_info "release_test/N ");
Mod_dec_use_count;
Globalvar_count --;
Return 0;
} Struct file_operations test_fops = {
Read: read_test,
Write: write_test,
Open: open_test,
Release: release_test
}; Int init_module (void)
{
Int result;
Result = register_chrdev (0, "test", & test_fops );
Init_mutex (& SEM );
If (result <0 ){
Printk (kern_info "test: Can't Get Major number/N ");
Return result;} If (test_major = 0) test_major = result;/* dynamic */
Return 0;} void cleanup_module (void) {unregister_chrdev (test_major, "test");} module_license ("GPL ");
Module_author ("Beckham"); // makefile
Cc = gcc
Modcflags: =-wall-dmodule-d1_kernel _-dlinux-I/usr/src/linux-2.4.20-8/include
Test. O: Hello. c
$ (CC) $ (modcflags)-C hello. C // test. c
# Include <stdio. h>
# Include <sys/types. h>
# Include <sys/STAT. h>
# Include <fcntl. h>
Main ()
{
Int testdev;
Int I;
Int J;
Char * Buf = malloc (150 );
Testdev = open ("/dev/test", o_rdwr );
If (testdev =-1 ){
Perror (open );
Printf ("cann' t open file/N ");
Exit (0 );
} J = read (testdev, Buf, 10 );
Strcat (BUF, "/0 ");
Printf ("% d = % s/n", J, Buf );
While (1 );
Close (testdev );
} Then delete the device RM/dev/test-F in sequence.
Uninstall the rmmode testmakeinsmod test module. omknod/dev/test C 254 0gcc-O test. c. /Test start another terminal and run test. The result will fail and the device is busy. |
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