access.c of ldd3 modified for 3.x.x kernel version

Here is the access.c code of scull, which is a part of Linux Device Drivers by Jonathan Corbet, modified for the kernel version 3.x.x. The code has been tested on 3.7.5 /* * access.c — the files with access control on open * * Copyright (C) 2001 Alessandro Rubini and Jonathan Corbet * Copyright (C) 2001 O’Reilly & Associates * * The source code in this file can be freely used, adapted, * and redistributed in source or binary form, so long as an * acknowledgment appears in derived source files. The citation * should list that the code comes from the book “Linux Device * Drivers” by Alessandro Rubini and Jonathan Corbet, published * by O’Reilly & Associates. No warranty is attached; * we cannot take responsibility for errors or fitness for use. * * $Id: access.c,v 1.17 2004/09/26 07:29:56 gregkh Exp $ */ /* FIXME: cloned devices as a use for kobjects? */ #include /* printk() */ #include #include /* kmalloc() */ #include /* everything… */ #include /* error codes */ #include /* size_t */ #include #include #include #include #include #include #include “scull.h” /* local definitions */ static dev_t scull_a_firstdev; /* Where our range begins */ /* * These devices fall back on the main scull operations. They only * differ in the implementation of open() and close() */ /************************************************************************ * * The first device is the single-open one, * it has an hw structure and an open count */ static struct scull_dev scull_s_device; static atomic_t scull_s_available = ATOMIC_INIT(1); static int scull_s_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_s_device; /* device information */ if (! atomic_dec_and_test (&scull_s_available)) { atomic_inc(&scull_s_available); return -EBUSY; /* already open */ } /* then, everything else is copied from the bare scull device */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_s_release(struct inode *inode, struct file *filp) { atomic_inc(&scull_s_available); /* release the device */ return 0; } /* * The other operations for the single-open device come from the bare device */ struct file_operations scull_sngl_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_s_open, .release = scull_s_release, }; /************************************************************************ * * Next, the “uid” device. It can be opened multiple times by the * same user, but access is denied to other users if the device is open */ static struct scull_dev scull_u_device; static int scull_u_count; /* initialized to 0 by default */ static uid_t scull_u_owner; /* initialized to 0 by default */ static spinlock_t scull_u_lock; static int scull_u_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_u_device; /* device information */ spin_lock(&scull_u_lock); printk(KERN_INFO “%d”,current_uid()); if (scull_u_count && (scull_u_owner != current_uid()) && /* allow user */ (scull_u_owner != current_euid()) && /* allow whoever did su */ !capable(CAP_DAC_OVERRIDE)) { /* still allow root */ spin_unlock(&scull_u_lock); return -EBUSY; /* -EPERM would confuse the user */ } if (scull_u_count == 0) scull_u_owner = current_uid(); /* grab it */ scull_u_count++; spin_unlock(&scull_u_lock); /* then, everything else is copied from the bare scull device */ if ((filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_u_release(struct inode *inode, struct file *filp) { spin_lock(&scull_u_lock); scull_u_count–; /* nothing else */ spin_unlock(&scull_u_lock); return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_user_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_u_open, .release = scull_u_release, }; /************************************************************************ * * Next, the device with blocking-open based on uid */ static struct scull_dev scull_w_device; static int scull_w_count; /* initialized to 0 by default */ static uid_t scull_w_owner; /* initialized to 0 by default */ static DECLARE_WAIT_QUEUE_HEAD(scull_w_wait); static spinlock_t scull_w_lock;// = SPIN_LOCK_UNLOCKED; static inline int scull_w_available(void) { return scull_w_count == 0 || scull_w_owner == current_uid() || scull_w_owner == current_euid() || capable(CAP_DAC_OVERRIDE); } static int scull_w_open(struct inode *inode, struct file *filp) { struct scull_dev *dev = &scull_w_device; /* device information */ spin_lock(&scull_w_lock); while (! scull_w_available()) { spin_unlock(&scull_w_lock); if (filp->f_flags & O_NONBLOCK) return -EAGAIN; if (wait_event_interruptible (scull_w_wait, scull_w_available())) return -ERESTARTSYS; /* tell the fs layer to handle it */ spin_lock(&scull_w_lock); } if (scull_w_count == 0) scull_w_owner = current_uid(); /* grab it */ scull_w_count++; spin_unlock(&scull_w_lock); /* then, everything else is copied from the bare scull device */ if ((filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_w_release(struct inode *inode, struct file *filp) { int temp; spin_lock(&scull_w_lock); scull_w_count–; temp = scull_w_count; spin_unlock(&scull_w_lock); if (temp == 0) wake_up_interruptible_sync(&scull_w_wait); /* awake other uid’s */ return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_wusr_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_w_open, .release = scull_w_release, }; /************************************************************************ * * Finally the `cloned’ private device. This is trickier because it * involves list management, and dynamic allocation. */ /* The clone-specific data structure includes a key field */ struct scull_listitem { struct scull_dev device; dev_t key; struct list_head list; }; /* The list of devices, and a lock to protect it */ static LIST_HEAD(scull_c_list); static spinlock_t scull_c_lock;// = SPIN_LOCK_UNLOCKED; /* A placeholder scull_dev which really just holds the cdev stuff. */ static struct scull_dev scull_c_device; /* Look for a device or create one if missing */ static struct scull_dev *scull_c_lookfor_device(dev_t key) { struct scull_listitem *lptr; list_for_each_entry(lptr, &scull_c_list, list) { if (lptr->key == key) return &(lptr->device); } /* not found */ lptr = kmalloc(sizeof(struct scull_listitem), GFP_KERNEL); if (!lptr) return NULL; /* initialize the device */ memset(lptr, 0, sizeof(struct scull_listitem)); lptr->key = key; scull_trim(&(lptr->device)); /* initialize it */ sema_init(&lptr->device.sem,1); /* place it in the list */ list_add(&lptr->list, &scull_c_list); return &(lptr->device); } static int scull_c_open(struct inode *inode, struct file *filp) { struct scull_dev *dev; dev_t key; if (!current->signal->tty) { PDEBUG(“Process \”%s\” has no ctl tty\n”, current->comm); return -EINVAL; } key = tty_devnum(current->signal->tty); /* look for a scullc device in the list */ spin_lock(&scull_c_lock); dev = scull_c_lookfor_device(key); spin_unlock(&scull_c_lock); if (!dev) return -ENOMEM; /* then, everything else is copied from the bare scull device */ if ( (filp->f_flags & O_ACCMODE) == O_WRONLY) scull_trim(dev); filp->private_data = dev; return 0; /* success */ } static int scull_c_release(struct inode *inode, struct file *filp) { /* * Nothing to do, because the device is persistent. * A `real’ cloned device should be freed on last close */ return 0; } /* * The other operations for the device come from the bare device */ struct file_operations scull_priv_fops = { .owner = THIS_MODULE, .llseek = scull_llseek, .read = scull_read, .write = scull_write, .unlocked_ioctl = scull_ioctl, .open = scull_c_open, .release = scull_c_release, }; /************************************************************************ * * And the init and cleanup functions come last */ static struct scull_adev_info { char *name; struct scull_dev *sculldev; struct file_operations *fops; } scull_access_devs[] = { { “scullsingle”, &scull_s_device, &scull_sngl_fops }, { “sculluid”, &scull_u_device, &scull_user_fops }, { “scullwuid”, &scull_w_device, &scull_wusr_fops }, { “sullpriv”, &scull_c_device, &scull_priv_fops } }; #define SCULL_N_ADEVS 4 /* * Set up a single device. */ static void scull_access_setup (dev_t devno, struct scull_adev_info *devinfo) { struct scull_dev *dev = devinfo->sculldev; int err; /* Initialize the device structure */ dev->quantum = scull_quantum; dev->qset = scull_qset; sema_init(&dev->sem,1); /* Do the cdev stuff. */ cdev_init(&dev->cdev, devinfo->fops); kobject_set_name(&dev->cdev.kobj, devinfo->name); dev->cdev.owner = THIS_MODULE; err = cdev_add (&dev->cdev, devno, 1); /* Fail gracefully if need be */ if (err) { printk(KERN_NOTICE “Error %d adding %s\n”, err, devinfo->name); kobject_put(&dev->cdev.kobj); } else printk(KERN_NOTICE “%s registered at %x\n”, devinfo->name, devno); } int scull_access_init(dev_t firstdev) { int result, i; /* Get our number space */ result = register_chrdev_region (firstdev, SCULL_N_ADEVS, “sculla”); if (result < 0) { printk(KERN_WARNING "sculla: device number registration failed\n"); return 0; } scull_a_firstdev = firstdev; /* Set up each device. */ for (i = 0; i < SCULL_N_ADEVS; i++) scull_access_setup (firstdev + i, scull_access_devs + i); return SCULL_N_ADEVS; } /* * This is called by cleanup_module or on failure. * It is required to never fail, even if nothing was initialized first */ void scull_access_cleanup(void) { struct scull_listitem *lptr, *next; int i; /* Clean up the static devs */ for (i = 0; i < SCULL_N_ADEVS; i++) { struct scull_dev *dev = scull_access_devs[i].sculldev; cdev_del(&dev->cdev); scull_trim(scull_access_devs[i].sculldev); } /* And all the cloned devices */ list_for_each_entry_safe(lptr, next, &scull_c_list, list) { list_del(&lptr->list); scull_trim(&(lptr->device)); kfree(lptr); } /* Free up our number space */ unregister_chrdev_region(scull_a_firstdev, SCULL_N_ADEVS); return; }


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Posted February 22, 2013 by Tux Think in category "Linux