kernel-ark/drivers/char/misc.c
Neil Horman 5d469ec0f4 [PATCH] Correct misc_register return code handling in several drivers
Clean up several code points in which the return code from misc_register is
not handled properly.

Several modules failed to deregister various hooks when misc_register fails,
and this patch cleans them up.  Also there are a few modules that legitimately
don't care about the failure status of misc register.  These drivers however
unilaterally call misc_deregister on module unload.

Since misc_register doesn't initialize the list_head in the init_routine if it
fails, the deregister operation is at risk for oopsing when list_del is
called.  The initial solution was to manually init the list in the miscdev
structure in each of those modules, but the consensus in this thread was to
consolodate and do that universally inside misc_register.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Kylene Jo Hall <kjhall@us.ibm.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Olaf Hering <olh@suse.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07 08:39:35 -08:00

297 lines
6.6 KiB
C

/*
* linux/drivers/char/misc.c
*
* Generic misc open routine by Johan Myreen
*
* Based on code from Linus
*
* Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
* changes incorporated into 0.97pl4
* by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
* See busmouse.c for particulars.
*
* Made things a lot mode modular - easy to compile in just one or two
* of the misc drivers, as they are now completely independent. Linus.
*
* Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
*
* Fixed a failing symbol register to free the device registration
* Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
*
* Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
*
* Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
*
* Handling of mouse minor numbers for kerneld:
* Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
* adapted by Bjorn Ekwall <bj0rn@blox.se>
* corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
*
* Changes for kmod (from kerneld):
* Cyrus Durgin <cider@speakeasy.org>
*
* Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
*/
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/slab.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/stat.h>
#include <linux/init.h>
#include <linux/device.h>
#include <linux/tty.h>
#include <linux/kmod.h>
/*
* Head entry for the doubly linked miscdevice list
*/
static LIST_HEAD(misc_list);
static DECLARE_MUTEX(misc_sem);
/*
* Assigned numbers, used for dynamic minors
*/
#define DYNAMIC_MINORS 64 /* like dynamic majors */
static unsigned char misc_minors[DYNAMIC_MINORS / 8];
extern int pmu_device_init(void);
#ifdef CONFIG_PROC_FS
static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
{
struct miscdevice *p;
loff_t off = 0;
down(&misc_sem);
list_for_each_entry(p, &misc_list, list) {
if (*pos == off++)
return p;
}
return NULL;
}
static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
struct list_head *n = ((struct miscdevice *)v)->list.next;
++*pos;
return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
: NULL;
}
static void misc_seq_stop(struct seq_file *seq, void *v)
{
up(&misc_sem);
}
static int misc_seq_show(struct seq_file *seq, void *v)
{
const struct miscdevice *p = v;
seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
return 0;
}
static struct seq_operations misc_seq_ops = {
.start = misc_seq_start,
.next = misc_seq_next,
.stop = misc_seq_stop,
.show = misc_seq_show,
};
static int misc_seq_open(struct inode *inode, struct file *file)
{
return seq_open(file, &misc_seq_ops);
}
static const struct file_operations misc_proc_fops = {
.owner = THIS_MODULE,
.open = misc_seq_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
#endif
static int misc_open(struct inode * inode, struct file * file)
{
int minor = iminor(inode);
struct miscdevice *c;
int err = -ENODEV;
const struct file_operations *old_fops, *new_fops = NULL;
down(&misc_sem);
list_for_each_entry(c, &misc_list, list) {
if (c->minor == minor) {
new_fops = fops_get(c->fops);
break;
}
}
if (!new_fops) {
up(&misc_sem);
request_module("char-major-%d-%d", MISC_MAJOR, minor);
down(&misc_sem);
list_for_each_entry(c, &misc_list, list) {
if (c->minor == minor) {
new_fops = fops_get(c->fops);
break;
}
}
if (!new_fops)
goto fail;
}
err = 0;
old_fops = file->f_op;
file->f_op = new_fops;
if (file->f_op->open) {
err=file->f_op->open(inode,file);
if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
}
fops_put(old_fops);
fail:
up(&misc_sem);
return err;
}
static struct class *misc_class;
static const struct file_operations misc_fops = {
.owner = THIS_MODULE,
.open = misc_open,
};
/**
* misc_register - register a miscellaneous device
* @misc: device structure
*
* Register a miscellaneous device with the kernel. If the minor
* number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
* and placed in the minor field of the structure. For other cases
* the minor number requested is used.
*
* The structure passed is linked into the kernel and may not be
* destroyed until it has been unregistered.
*
* A zero is returned on success and a negative errno code for
* failure.
*/
int misc_register(struct miscdevice * misc)
{
struct miscdevice *c;
dev_t dev;
int err = 0;
INIT_LIST_HEAD(&misc->list);
down(&misc_sem);
list_for_each_entry(c, &misc_list, list) {
if (c->minor == misc->minor) {
up(&misc_sem);
return -EBUSY;
}
}
if (misc->minor == MISC_DYNAMIC_MINOR) {
int i = DYNAMIC_MINORS;
while (--i >= 0)
if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
break;
if (i<0) {
up(&misc_sem);
return -EBUSY;
}
misc->minor = i;
}
if (misc->minor < DYNAMIC_MINORS)
misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
dev = MKDEV(MISC_MAJOR, misc->minor);
misc->this_device = device_create(misc_class, misc->parent, dev,
"%s", misc->name);
if (IS_ERR(misc->this_device)) {
err = PTR_ERR(misc->this_device);
goto out;
}
/*
* Add it to the front, so that later devices can "override"
* earlier defaults
*/
list_add(&misc->list, &misc_list);
out:
up(&misc_sem);
return err;
}
/**
* misc_deregister - unregister a miscellaneous device
* @misc: device to unregister
*
* Unregister a miscellaneous device that was previously
* successfully registered with misc_register(). Success
* is indicated by a zero return, a negative errno code
* indicates an error.
*/
int misc_deregister(struct miscdevice * misc)
{
int i = misc->minor;
if (list_empty(&misc->list))
return -EINVAL;
down(&misc_sem);
list_del(&misc->list);
device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
if (i < DYNAMIC_MINORS && i>0) {
misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
}
up(&misc_sem);
return 0;
}
EXPORT_SYMBOL(misc_register);
EXPORT_SYMBOL(misc_deregister);
static int __init misc_init(void)
{
#ifdef CONFIG_PROC_FS
struct proc_dir_entry *ent;
ent = create_proc_entry("misc", 0, NULL);
if (ent)
ent->proc_fops = &misc_proc_fops;
#endif
misc_class = class_create(THIS_MODULE, "misc");
if (IS_ERR(misc_class))
return PTR_ERR(misc_class);
if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
printk("unable to get major %d for misc devices\n",
MISC_MAJOR);
class_destroy(misc_class);
return -EIO;
}
return 0;
}
subsys_initcall(misc_init);