Энциклопедия разработчика модулей ядра Linux

Померанц Ори

 * to one and to open the file. All the other processes

 * will be called when Already_Open is back to one, so

 * they'll go back to sleep. */

 Already_Open = 0;

 /* Wake up all the processes in WaitQ, so if anybody

 * is waiting for the file, they can have it. */

 module_wake_up(&WaitQ);

 MOD_DEC_USE_COUNT;

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

 return 0; /* success */

#endif

}

/* This function decides whether to allow an operation

* (return zero) or not allow it (return a non-zero

* which indicates why it is not allowed).

*

* The operation can be one of the following values:

* 0 - Execute (run the "file" - meaningless in our case)

* 2 - Write (input to the kernel module)

* 4 - Read (output from the kernel module)

*

* This is the real function that checks file

* permissions. The permissions returned by ls -l are

* for referece only, and can be overridden here. */

static int module_permission(struct inode *inode, int op) {

 /* We allow everybody to read from our module, but

 * only root (uid 0) may write to it */

 if (op == 4 || (op == 2 && current->euid == 0)) return 0;

 /* If it's anything else, access is denied */

 return -EACCES;

}

/* Structures to register as the /proc file, with

* pointers to all the relevant functions. *********** */

/* File operations for our proc file. This is where

* we place pointers to all the functions called when

* somebody tries to do something to our file. NULL

* means we don't want to deal with something. */

static struct file_operations File_Ops_4_Our_Proc_File = {

 NULL, /* lseek */

 module_output, /* "read" from the file */

 module_input, /* "write" to the file */

 NULL, /* readdir */

 NULL, /* select */

 NULL, /* ioctl */

 NULL, /* mmap */

 module_open,/* called when the /proc file is opened */

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

 NULL, /* flush */

#endif

 module_close /* called when it's classed */

};

/* Inode operations for our proc file. We need it so

* we'll have somewhere to specify the file operations

* structure we want to use, and the function we use for

* permissions. It's also possible to specify functions

* to be called for anything else which could be done to an

* inode (although we don't bother, we just put NULL). */

static struct inode_operations Inode_Ops_4_Our_Proc_File = {

 &File_Ops_4_Our_Proc_File,

 NULL, /* create */

 NULL, /* lookup */

 NULL, /* link */

 NULL, /* unlink */

 NULL, /* symlink */

 NULL, /* mkdir */

 NULL, /* rmdir */

 NULL, /* mknod */

 NULL, /* rename */

 NULL, /* readlink */

 NULL, /* follow_link */

 NULL, /* readpage */

 NULL, /* writepage */

 NULL, /* bmap */

 NULL, /* truncate */

 module_permission /* check for permissions */

};

/* Directory entry */

static struct proc_dir_entry Our_Proc_File = {

 0, /* Inode number - ignore, it will be filled by proc_register[_dynamic] */

 5, /* Length of the file name */

 "sleep", /* The file name */

 S_IFREG | S_IRUGO | S_IWUSR,

/* File mode - this is a regular file which

* can be read by its owner, its group, and everybody

* else. Also, its owner can write to it.

*

* Actually, this field is just for reference, it's

* module_permission that does the actual check. It

* could use this field, but in our implementation it

* doesn't, for simplicity. */

 1, /* Number of links (directories where the file is referenced) */