The code in __register_chrdev_region checks that if the driver wishing to register has the same major as an existing driver the new minor range is strictly less than the existing minor range. However, it does not also check that the new minor range is strictly greater than the existing minor range. That is, if driver X has registered with major=x and minor=0-3, __register_chrdev_region will allow driver Y to register with major=x and minor=1-4. Signed-off-by: Amos Waterland <apw@us.ibm.com> Cc: Linas Vepstas <linas@austin.ibm.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
502 lines
11 KiB
C
502 lines
11 KiB
C
/*
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* linux/fs/char_dev.c
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*
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* Copyright (C) 1991, 1992 Linus Torvalds
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*/
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/major.h>
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#include <linux/errno.h>
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#include <linux/module.h>
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#include <linux/smp_lock.h>
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#include <linux/seq_file.h>
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#include <linux/kobject.h>
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#include <linux/kobj_map.h>
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#include <linux/cdev.h>
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#include <linux/mutex.h>
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#include <linux/backing-dev.h>
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#ifdef CONFIG_KMOD
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#include <linux/kmod.h>
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#endif
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/*
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* capabilities for /dev/mem, /dev/kmem and similar directly mappable character
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* devices
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* - permits shared-mmap for read, write and/or exec
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* - does not permit private mmap in NOMMU mode (can't do COW)
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* - no readahead or I/O queue unplugging required
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*/
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struct backing_dev_info directly_mappable_cdev_bdi = {
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.capabilities = (
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#ifdef CONFIG_MMU
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/* permit private copies of the data to be taken */
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BDI_CAP_MAP_COPY |
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#endif
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/* permit direct mmap, for read, write or exec */
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BDI_CAP_MAP_DIRECT |
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BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
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};
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static struct kobj_map *cdev_map;
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static DEFINE_MUTEX(chrdevs_lock);
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static struct char_device_struct {
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struct char_device_struct *next;
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unsigned int major;
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unsigned int baseminor;
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int minorct;
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char name[64];
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struct file_operations *fops;
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struct cdev *cdev; /* will die */
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} *chrdevs[CHRDEV_MAJOR_HASH_SIZE];
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/* index in the above */
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static inline int major_to_index(int major)
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{
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return major % CHRDEV_MAJOR_HASH_SIZE;
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}
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#ifdef CONFIG_PROC_FS
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void chrdev_show(struct seq_file *f, off_t offset)
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{
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struct char_device_struct *cd;
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if (offset < CHRDEV_MAJOR_HASH_SIZE) {
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mutex_lock(&chrdevs_lock);
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for (cd = chrdevs[offset]; cd; cd = cd->next)
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seq_printf(f, "%3d %s\n", cd->major, cd->name);
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mutex_unlock(&chrdevs_lock);
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}
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}
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#endif /* CONFIG_PROC_FS */
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/*
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* Register a single major with a specified minor range.
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*
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* If major == 0 this functions will dynamically allocate a major and return
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* its number.
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*
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* If major > 0 this function will attempt to reserve the passed range of
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* minors and will return zero on success.
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*
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* Returns a -ve errno on failure.
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*/
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static struct char_device_struct *
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__register_chrdev_region(unsigned int major, unsigned int baseminor,
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int minorct, const char *name)
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{
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struct char_device_struct *cd, **cp;
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int ret = 0;
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int i;
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cd = kzalloc(sizeof(struct char_device_struct), GFP_KERNEL);
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if (cd == NULL)
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return ERR_PTR(-ENOMEM);
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mutex_lock(&chrdevs_lock);
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/* temporary */
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if (major == 0) {
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for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
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if (chrdevs[i] == NULL)
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break;
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}
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if (i == 0) {
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ret = -EBUSY;
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goto out;
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}
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major = i;
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ret = major;
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}
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cd->major = major;
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cd->baseminor = baseminor;
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cd->minorct = minorct;
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strncpy(cd->name,name, 64);
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i = major_to_index(major);
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for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
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if ((*cp)->major > major ||
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((*cp)->major == major &&
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(((*cp)->baseminor >= baseminor) ||
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((*cp)->baseminor + (*cp)->minorct > baseminor))))
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break;
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/* Check for overlapping minor ranges. */
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if (*cp && (*cp)->major == major) {
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int old_min = (*cp)->baseminor;
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int old_max = (*cp)->baseminor + (*cp)->minorct - 1;
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int new_min = baseminor;
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int new_max = baseminor + minorct - 1;
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/* New driver overlaps from the left. */
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if (new_max >= old_min && new_max <= old_max) {
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ret = -EBUSY;
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goto out;
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}
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/* New driver overlaps from the right. */
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if (new_min <= old_max && new_min >= old_min) {
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ret = -EBUSY;
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goto out;
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}
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}
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cd->next = *cp;
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*cp = cd;
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mutex_unlock(&chrdevs_lock);
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return cd;
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out:
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mutex_unlock(&chrdevs_lock);
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kfree(cd);
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return ERR_PTR(ret);
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}
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static struct char_device_struct *
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__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
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{
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struct char_device_struct *cd = NULL, **cp;
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int i = major_to_index(major);
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mutex_lock(&chrdevs_lock);
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for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
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if ((*cp)->major == major &&
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(*cp)->baseminor == baseminor &&
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(*cp)->minorct == minorct)
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break;
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if (*cp) {
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cd = *cp;
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*cp = cd->next;
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}
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mutex_unlock(&chrdevs_lock);
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return cd;
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}
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int register_chrdev_region(dev_t from, unsigned count, const char *name)
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{
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struct char_device_struct *cd;
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dev_t to = from + count;
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dev_t n, next;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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if (next > to)
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next = to;
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cd = __register_chrdev_region(MAJOR(n), MINOR(n),
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next - n, name);
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if (IS_ERR(cd))
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goto fail;
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}
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return 0;
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fail:
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to = n;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
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}
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return PTR_ERR(cd);
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}
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int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
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const char *name)
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{
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struct char_device_struct *cd;
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cd = __register_chrdev_region(0, baseminor, count, name);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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*dev = MKDEV(cd->major, cd->baseminor);
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return 0;
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}
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/**
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* register_chrdev() - Register a major number for character devices.
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* @major: major device number or 0 for dynamic allocation
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* @name: name of this range of devices
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* @fops: file operations associated with this devices
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*
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* If @major == 0 this functions will dynamically allocate a major and return
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* its number.
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*
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* If @major > 0 this function will attempt to reserve a device with the given
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* major number and will return zero on success.
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*
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* Returns a -ve errno on failure.
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*
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* The name of this device has nothing to do with the name of the device in
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* /dev. It only helps to keep track of the different owners of devices. If
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* your module name has only one type of devices it's ok to use e.g. the name
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* of the module here.
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*
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* This function registers a range of 256 minor numbers. The first minor number
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* is 0.
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*/
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int register_chrdev(unsigned int major, const char *name,
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const struct file_operations *fops)
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{
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struct char_device_struct *cd;
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struct cdev *cdev;
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char *s;
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int err = -ENOMEM;
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cd = __register_chrdev_region(major, 0, 256, name);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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cdev = cdev_alloc();
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if (!cdev)
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goto out2;
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cdev->owner = fops->owner;
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cdev->ops = fops;
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kobject_set_name(&cdev->kobj, "%s", name);
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for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
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*s = '!';
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err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
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if (err)
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goto out;
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cd->cdev = cdev;
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return major ? 0 : cd->major;
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out:
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kobject_put(&cdev->kobj);
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out2:
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kfree(__unregister_chrdev_region(cd->major, 0, 256));
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return err;
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}
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void unregister_chrdev_region(dev_t from, unsigned count)
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{
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dev_t to = from + count;
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dev_t n, next;
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for (n = from; n < to; n = next) {
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next = MKDEV(MAJOR(n)+1, 0);
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if (next > to)
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next = to;
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kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
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}
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}
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int unregister_chrdev(unsigned int major, const char *name)
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{
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struct char_device_struct *cd;
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cd = __unregister_chrdev_region(major, 0, 256);
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if (cd && cd->cdev)
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cdev_del(cd->cdev);
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kfree(cd);
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return 0;
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}
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static DEFINE_SPINLOCK(cdev_lock);
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static struct kobject *cdev_get(struct cdev *p)
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{
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struct module *owner = p->owner;
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struct kobject *kobj;
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if (owner && !try_module_get(owner))
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return NULL;
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kobj = kobject_get(&p->kobj);
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if (!kobj)
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module_put(owner);
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return kobj;
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}
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void cdev_put(struct cdev *p)
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{
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if (p) {
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struct module *owner = p->owner;
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kobject_put(&p->kobj);
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module_put(owner);
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}
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}
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/*
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* Called every time a character special file is opened
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*/
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int chrdev_open(struct inode * inode, struct file * filp)
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{
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struct cdev *p;
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struct cdev *new = NULL;
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int ret = 0;
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spin_lock(&cdev_lock);
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p = inode->i_cdev;
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if (!p) {
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struct kobject *kobj;
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int idx;
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spin_unlock(&cdev_lock);
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kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
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if (!kobj)
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return -ENXIO;
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new = container_of(kobj, struct cdev, kobj);
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spin_lock(&cdev_lock);
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p = inode->i_cdev;
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if (!p) {
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inode->i_cdev = p = new;
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inode->i_cindex = idx;
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list_add(&inode->i_devices, &p->list);
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new = NULL;
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} else if (!cdev_get(p))
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ret = -ENXIO;
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} else if (!cdev_get(p))
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ret = -ENXIO;
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spin_unlock(&cdev_lock);
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cdev_put(new);
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if (ret)
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return ret;
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filp->f_op = fops_get(p->ops);
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if (!filp->f_op) {
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cdev_put(p);
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return -ENXIO;
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}
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if (filp->f_op->open) {
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lock_kernel();
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ret = filp->f_op->open(inode,filp);
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unlock_kernel();
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}
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if (ret)
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cdev_put(p);
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return ret;
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}
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void cd_forget(struct inode *inode)
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{
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spin_lock(&cdev_lock);
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list_del_init(&inode->i_devices);
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inode->i_cdev = NULL;
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spin_unlock(&cdev_lock);
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}
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static void cdev_purge(struct cdev *cdev)
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{
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spin_lock(&cdev_lock);
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while (!list_empty(&cdev->list)) {
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struct inode *inode;
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inode = container_of(cdev->list.next, struct inode, i_devices);
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list_del_init(&inode->i_devices);
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inode->i_cdev = NULL;
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}
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spin_unlock(&cdev_lock);
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}
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/*
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* Dummy default file-operations: the only thing this does
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* is contain the open that then fills in the correct operations
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* depending on the special file...
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*/
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const struct file_operations def_chr_fops = {
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.open = chrdev_open,
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};
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static struct kobject *exact_match(dev_t dev, int *part, void *data)
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{
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struct cdev *p = data;
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return &p->kobj;
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}
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static int exact_lock(dev_t dev, void *data)
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{
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struct cdev *p = data;
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return cdev_get(p) ? 0 : -1;
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}
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int cdev_add(struct cdev *p, dev_t dev, unsigned count)
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{
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p->dev = dev;
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p->count = count;
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return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
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}
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static void cdev_unmap(dev_t dev, unsigned count)
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{
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kobj_unmap(cdev_map, dev, count);
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}
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void cdev_del(struct cdev *p)
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{
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cdev_unmap(p->dev, p->count);
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kobject_put(&p->kobj);
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}
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static void cdev_default_release(struct kobject *kobj)
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{
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struct cdev *p = container_of(kobj, struct cdev, kobj);
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cdev_purge(p);
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}
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static void cdev_dynamic_release(struct kobject *kobj)
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{
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struct cdev *p = container_of(kobj, struct cdev, kobj);
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cdev_purge(p);
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kfree(p);
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}
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static struct kobj_type ktype_cdev_default = {
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.release = cdev_default_release,
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};
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static struct kobj_type ktype_cdev_dynamic = {
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.release = cdev_dynamic_release,
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};
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struct cdev *cdev_alloc(void)
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{
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struct cdev *p = kzalloc(sizeof(struct cdev), GFP_KERNEL);
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if (p) {
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p->kobj.ktype = &ktype_cdev_dynamic;
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INIT_LIST_HEAD(&p->list);
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kobject_init(&p->kobj);
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}
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return p;
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}
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void cdev_init(struct cdev *cdev, const struct file_operations *fops)
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{
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memset(cdev, 0, sizeof *cdev);
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INIT_LIST_HEAD(&cdev->list);
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cdev->kobj.ktype = &ktype_cdev_default;
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kobject_init(&cdev->kobj);
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cdev->ops = fops;
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}
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static struct kobject *base_probe(dev_t dev, int *part, void *data)
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{
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if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
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/* Make old-style 2.4 aliases work */
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request_module("char-major-%d", MAJOR(dev));
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return NULL;
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}
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void __init chrdev_init(void)
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{
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cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
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}
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/* Let modules do char dev stuff */
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EXPORT_SYMBOL(register_chrdev_region);
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EXPORT_SYMBOL(unregister_chrdev_region);
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EXPORT_SYMBOL(alloc_chrdev_region);
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EXPORT_SYMBOL(cdev_init);
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EXPORT_SYMBOL(cdev_alloc);
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EXPORT_SYMBOL(cdev_del);
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EXPORT_SYMBOL(cdev_add);
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EXPORT_SYMBOL(register_chrdev);
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EXPORT_SYMBOL(unregister_chrdev);
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EXPORT_SYMBOL(directly_mappable_cdev_bdi);
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