linux/drivers/watchdog/watchdog_dev.c
Guenter Roeck 0254e95353 watchdog: Drop pointer to watchdog device from struct watchdog_device
The lifetime of the watchdog device pointer is different from the lifetime
of its character device. Remove it entirely to avoid race conditions.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2016-01-11 21:53:59 +01:00

810 lines
19 KiB
C

/*
* watchdog_dev.c
*
* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
*
*
* This source code is part of the generic code that can be used
* by all the watchdog timer drivers.
*
* This part of the generic code takes care of the following
* misc device: /dev/watchdog.
*
* Based on source code of the following authors:
* Matt Domsch <Matt_Domsch@dell.com>,
* Rob Radez <rob@osinvestor.com>,
* Rusty Lynch <rusty@linux.co.intel.com>
* Satyam Sharma <satyam@infradead.org>
* Randy Dunlap <randy.dunlap@oracle.com>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
* admit liability nor provide warranty for any of this software.
* This material is provided "AS-IS" and at no charge.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/cdev.h> /* For character device */
#include <linux/errno.h> /* For the -ENODEV/... values */
#include <linux/fs.h> /* For file operations */
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/kernel.h> /* For printk/panic/... */
#include <linux/kref.h> /* For data references */
#include <linux/miscdevice.h> /* For handling misc devices */
#include <linux/module.h> /* For module stuff/... */
#include <linux/mutex.h> /* For mutexes */
#include <linux/slab.h> /* For memory functions */
#include <linux/types.h> /* For standard types (like size_t) */
#include <linux/watchdog.h> /* For watchdog specific items */
#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
#include "watchdog_core.h"
/*
* struct watchdog_core_data - watchdog core internal data
* @kref: Reference count.
* @cdev: The watchdog's Character device.
* @wdd: Pointer to watchdog device.
* @lock: Lock for watchdog core.
* @status: Watchdog core internal status bits.
*/
struct watchdog_core_data {
struct kref kref;
struct cdev cdev;
struct watchdog_device *wdd;
struct mutex lock;
unsigned long status; /* Internal status bits */
#define _WDOG_DEV_OPEN 0 /* Opened ? */
#define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */
};
/* the dev_t structure to store the dynamically allocated watchdog devices */
static dev_t watchdog_devt;
/* Reference to watchdog device behind /dev/watchdog */
static struct watchdog_core_data *old_wd_data;
/*
* watchdog_ping: ping the watchdog.
* @wdd: the watchdog device to ping
*
* The caller must hold wd_data->lock.
*
* If the watchdog has no own ping operation then it needs to be
* restarted via the start operation. This wrapper function does
* exactly that.
* We only ping when the watchdog device is running.
*/
static int watchdog_ping(struct watchdog_device *wdd)
{
int err;
if (!watchdog_active(wdd))
return 0;
if (wdd->ops->ping)
err = wdd->ops->ping(wdd); /* ping the watchdog */
else
err = wdd->ops->start(wdd); /* restart watchdog */
return err;
}
/*
* watchdog_start: wrapper to start the watchdog.
* @wdd: the watchdog device to start
*
* The caller must hold wd_data->lock.
*
* Start the watchdog if it is not active and mark it active.
* This function returns zero on success or a negative errno code for
* failure.
*/
static int watchdog_start(struct watchdog_device *wdd)
{
int err;
if (watchdog_active(wdd))
return 0;
err = wdd->ops->start(wdd);
if (err == 0)
set_bit(WDOG_ACTIVE, &wdd->status);
return err;
}
/*
* watchdog_stop: wrapper to stop the watchdog.
* @wdd: the watchdog device to stop
*
* The caller must hold wd_data->lock.
*
* Stop the watchdog if it is still active and unmark it active.
* This function returns zero on success or a negative errno code for
* failure.
* If the 'nowayout' feature was set, the watchdog cannot be stopped.
*/
static int watchdog_stop(struct watchdog_device *wdd)
{
int err;
if (!watchdog_active(wdd))
return 0;
if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
wdd->id);
return -EBUSY;
}
err = wdd->ops->stop(wdd);
if (err == 0)
clear_bit(WDOG_ACTIVE, &wdd->status);
return err;
}
/*
* watchdog_get_status: wrapper to get the watchdog status
* @wdd: the watchdog device to get the status from
*
* The caller must hold wd_data->lock.
*
* Get the watchdog's status flags.
*/
static unsigned int watchdog_get_status(struct watchdog_device *wdd)
{
if (!wdd->ops->status)
return 0;
return wdd->ops->status(wdd);
}
/*
* watchdog_set_timeout: set the watchdog timer timeout
* @wdd: the watchdog device to set the timeout for
* @timeout: timeout to set in seconds
*
* The caller must hold wd_data->lock.
*/
static int watchdog_set_timeout(struct watchdog_device *wdd,
unsigned int timeout)
{
if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
return -EOPNOTSUPP;
if (watchdog_timeout_invalid(wdd, timeout))
return -EINVAL;
return wdd->ops->set_timeout(wdd, timeout);
}
/*
* watchdog_get_timeleft: wrapper to get the time left before a reboot
* @wdd: the watchdog device to get the remaining time from
* @timeleft: the time that's left
*
* The caller must hold wd_data->lock.
*
* Get the time before a watchdog will reboot (if not pinged).
*/
static int watchdog_get_timeleft(struct watchdog_device *wdd,
unsigned int *timeleft)
{
*timeleft = 0;
if (!wdd->ops->get_timeleft)
return -EOPNOTSUPP;
*timeleft = wdd->ops->get_timeleft(wdd);
return 0;
}
#ifdef CONFIG_WATCHDOG_SYSFS
static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
}
static DEVICE_ATTR_RO(nowayout);
static ssize_t status_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
struct watchdog_core_data *wd_data = wdd->wd_data;
unsigned int status;
mutex_lock(&wd_data->lock);
status = watchdog_get_status(wdd);
mutex_unlock(&wd_data->lock);
return sprintf(buf, "%u\n", status);
}
static DEVICE_ATTR_RO(status);
static ssize_t bootstatus_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
return sprintf(buf, "%u\n", wdd->bootstatus);
}
static DEVICE_ATTR_RO(bootstatus);
static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
struct watchdog_core_data *wd_data = wdd->wd_data;
ssize_t status;
unsigned int val;
mutex_lock(&wd_data->lock);
status = watchdog_get_timeleft(wdd, &val);
mutex_unlock(&wd_data->lock);
if (!status)
status = sprintf(buf, "%u\n", val);
return status;
}
static DEVICE_ATTR_RO(timeleft);
static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
return sprintf(buf, "%u\n", wdd->timeout);
}
static DEVICE_ATTR_RO(timeout);
static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
return sprintf(buf, "%s\n", wdd->info->identity);
}
static DEVICE_ATTR_RO(identity);
static ssize_t state_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
struct watchdog_device *wdd = dev_get_drvdata(dev);
if (watchdog_active(wdd))
return sprintf(buf, "active\n");
return sprintf(buf, "inactive\n");
}
static DEVICE_ATTR_RO(state);
static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
int n)
{
struct device *dev = container_of(kobj, struct device, kobj);
struct watchdog_device *wdd = dev_get_drvdata(dev);
umode_t mode = attr->mode;
if (attr == &dev_attr_status.attr && !wdd->ops->status)
mode = 0;
else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
mode = 0;
return mode;
}
static struct attribute *wdt_attrs[] = {
&dev_attr_state.attr,
&dev_attr_identity.attr,
&dev_attr_timeout.attr,
&dev_attr_timeleft.attr,
&dev_attr_bootstatus.attr,
&dev_attr_status.attr,
&dev_attr_nowayout.attr,
NULL,
};
static const struct attribute_group wdt_group = {
.attrs = wdt_attrs,
.is_visible = wdt_is_visible,
};
__ATTRIBUTE_GROUPS(wdt);
#else
#define wdt_groups NULL
#endif
/*
* watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
* @wdd: the watchdog device to do the ioctl on
* @cmd: watchdog command
* @arg: argument pointer
*
* The caller must hold wd_data->lock.
*/
static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
unsigned long arg)
{
if (!wdd->ops->ioctl)
return -ENOIOCTLCMD;
return wdd->ops->ioctl(wdd, cmd, arg);
}
/*
* watchdog_write: writes to the watchdog.
* @file: file from VFS
* @data: user address of data
* @len: length of data
* @ppos: pointer to the file offset
*
* A write to a watchdog device is defined as a keepalive ping.
* Writing the magic 'V' sequence allows the next close to turn
* off the watchdog (if 'nowayout' is not set).
*/
static ssize_t watchdog_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
struct watchdog_core_data *wd_data = file->private_data;
struct watchdog_device *wdd;
int err;
size_t i;
char c;
if (len == 0)
return 0;
/*
* Note: just in case someone wrote the magic character
* five months ago...
*/
clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
/* scan to see whether or not we got the magic character */
for (i = 0; i != len; i++) {
if (get_user(c, data + i))
return -EFAULT;
if (c == 'V')
set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
}
/* someone wrote to us, so we send the watchdog a keepalive ping */
err = -ENODEV;
mutex_lock(&wd_data->lock);
wdd = wd_data->wdd;
if (wdd)
err = watchdog_ping(wdd);
mutex_unlock(&wd_data->lock);
if (err < 0)
return err;
return len;
}
/*
* watchdog_ioctl: handle the different ioctl's for the watchdog device.
* @file: file handle to the device
* @cmd: watchdog command
* @arg: argument pointer
*
* The watchdog API defines a common set of functions for all watchdogs
* according to their available features.
*/
static long watchdog_ioctl(struct file *file, unsigned int cmd,
unsigned long arg)
{
struct watchdog_core_data *wd_data = file->private_data;
void __user *argp = (void __user *)arg;
struct watchdog_device *wdd;
int __user *p = argp;
unsigned int val;
int err;
mutex_lock(&wd_data->lock);
wdd = wd_data->wdd;
if (!wdd) {
err = -ENODEV;
goto out_ioctl;
}
err = watchdog_ioctl_op(wdd, cmd, arg);
if (err != -ENOIOCTLCMD)
goto out_ioctl;
switch (cmd) {
case WDIOC_GETSUPPORT:
err = copy_to_user(argp, wdd->info,
sizeof(struct watchdog_info)) ? -EFAULT : 0;
break;
case WDIOC_GETSTATUS:
val = watchdog_get_status(wdd);
err = put_user(val, p);
break;
case WDIOC_GETBOOTSTATUS:
err = put_user(wdd->bootstatus, p);
break;
case WDIOC_SETOPTIONS:
if (get_user(val, p)) {
err = -EFAULT;
break;
}
if (val & WDIOS_DISABLECARD) {
err = watchdog_stop(wdd);
if (err < 0)
break;
}
if (val & WDIOS_ENABLECARD)
err = watchdog_start(wdd);
break;
case WDIOC_KEEPALIVE:
if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
err = -EOPNOTSUPP;
break;
}
err = watchdog_ping(wdd);
break;
case WDIOC_SETTIMEOUT:
if (get_user(val, p)) {
err = -EFAULT;
break;
}
err = watchdog_set_timeout(wdd, val);
if (err < 0)
break;
/* If the watchdog is active then we send a keepalive ping
* to make sure that the watchdog keep's running (and if
* possible that it takes the new timeout) */
err = watchdog_ping(wdd);
if (err < 0)
break;
/* Fall */
case WDIOC_GETTIMEOUT:
/* timeout == 0 means that we don't know the timeout */
if (wdd->timeout == 0) {
err = -EOPNOTSUPP;
break;
}
err = put_user(wdd->timeout, p);
break;
case WDIOC_GETTIMELEFT:
err = watchdog_get_timeleft(wdd, &val);
if (err < 0)
break;
err = put_user(val, p);
break;
default:
err = -ENOTTY;
break;
}
out_ioctl:
mutex_unlock(&wd_data->lock);
return err;
}
/*
* watchdog_open: open the /dev/watchdog* devices.
* @inode: inode of device
* @file: file handle to device
*
* When the /dev/watchdog* device gets opened, we start the watchdog.
* Watch out: the /dev/watchdog device is single open, so we make sure
* it can only be opened once.
*/
static int watchdog_open(struct inode *inode, struct file *file)
{
struct watchdog_core_data *wd_data;
struct watchdog_device *wdd;
int err;
/* Get the corresponding watchdog device */
if (imajor(inode) == MISC_MAJOR)
wd_data = old_wd_data;
else
wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
cdev);
/* the watchdog is single open! */
if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
return -EBUSY;
wdd = wd_data->wdd;
/*
* If the /dev/watchdog device is open, we don't want the module
* to be unloaded.
*/
if (!try_module_get(wdd->ops->owner)) {
err = -EBUSY;
goto out_clear;
}
err = watchdog_start(wdd);
if (err < 0)
goto out_mod;
file->private_data = wd_data;
kref_get(&wd_data->kref);
/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
return nonseekable_open(inode, file);
out_mod:
module_put(wd_data->wdd->ops->owner);
out_clear:
clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
return err;
}
static void watchdog_core_data_release(struct kref *kref)
{
struct watchdog_core_data *wd_data;
wd_data = container_of(kref, struct watchdog_core_data, kref);
kfree(wd_data);
}
/*
* watchdog_release: release the watchdog device.
* @inode: inode of device
* @file: file handle to device
*
* This is the code for when /dev/watchdog gets closed. We will only
* stop the watchdog when we have received the magic char (and nowayout
* was not set), else the watchdog will keep running.
*/
static int watchdog_release(struct inode *inode, struct file *file)
{
struct watchdog_core_data *wd_data = file->private_data;
struct watchdog_device *wdd;
int err = -EBUSY;
mutex_lock(&wd_data->lock);
wdd = wd_data->wdd;
if (!wdd)
goto done;
/*
* We only stop the watchdog if we received the magic character
* or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
* watchdog_stop will fail.
*/
if (!test_bit(WDOG_ACTIVE, &wdd->status))
err = 0;
else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
!(wdd->info->options & WDIOF_MAGICCLOSE))
err = watchdog_stop(wdd);
/* If the watchdog was not stopped, send a keepalive ping */
if (err < 0) {
pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
watchdog_ping(wdd);
}
/* make sure that /dev/watchdog can be re-opened */
clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
done:
mutex_unlock(&wd_data->lock);
/* Allow the owner module to be unloaded again */
module_put(wd_data->cdev.owner);
kref_put(&wd_data->kref, watchdog_core_data_release);
return 0;
}
static const struct file_operations watchdog_fops = {
.owner = THIS_MODULE,
.write = watchdog_write,
.unlocked_ioctl = watchdog_ioctl,
.open = watchdog_open,
.release = watchdog_release,
};
static struct miscdevice watchdog_miscdev = {
.minor = WATCHDOG_MINOR,
.name = "watchdog",
.fops = &watchdog_fops,
};
/*
* watchdog_cdev_register: register watchdog character device
* @wdd: watchdog device
* @devno: character device number
*
* Register a watchdog character device including handling the legacy
* /dev/watchdog node. /dev/watchdog is actually a miscdevice and
* thus we set it up like that.
*/
static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
{
struct watchdog_core_data *wd_data;
int err;
wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
if (!wd_data)
return -ENOMEM;
kref_init(&wd_data->kref);
mutex_init(&wd_data->lock);
wd_data->wdd = wdd;
wdd->wd_data = wd_data;
if (wdd->id == 0) {
old_wd_data = wd_data;
watchdog_miscdev.parent = wdd->parent;
err = misc_register(&watchdog_miscdev);
if (err != 0) {
pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
wdd->info->identity, WATCHDOG_MINOR, err);
if (err == -EBUSY)
pr_err("%s: a legacy watchdog module is probably present.\n",
wdd->info->identity);
old_wd_data = NULL;
kfree(wd_data);
return err;
}
}
/* Fill in the data structures */
cdev_init(&wd_data->cdev, &watchdog_fops);
wd_data->cdev.owner = wdd->ops->owner;
/* Add the device */
err = cdev_add(&wd_data->cdev, devno, 1);
if (err) {
pr_err("watchdog%d unable to add device %d:%d\n",
wdd->id, MAJOR(watchdog_devt), wdd->id);
if (wdd->id == 0) {
misc_deregister(&watchdog_miscdev);
old_wd_data = NULL;
kref_put(&wd_data->kref, watchdog_core_data_release);
}
}
return err;
}
/*
* watchdog_cdev_unregister: unregister watchdog character device
* @watchdog: watchdog device
*
* Unregister watchdog character device and if needed the legacy
* /dev/watchdog device.
*/
static void watchdog_cdev_unregister(struct watchdog_device *wdd)
{
struct watchdog_core_data *wd_data = wdd->wd_data;
cdev_del(&wd_data->cdev);
if (wdd->id == 0) {
misc_deregister(&watchdog_miscdev);
old_wd_data = NULL;
}
mutex_lock(&wd_data->lock);
wd_data->wdd = NULL;
wdd->wd_data = NULL;
mutex_unlock(&wd_data->lock);
kref_put(&wd_data->kref, watchdog_core_data_release);
}
static struct class watchdog_class = {
.name = "watchdog",
.owner = THIS_MODULE,
.dev_groups = wdt_groups,
};
/*
* watchdog_dev_register: register a watchdog device
* @wdd: watchdog device
*
* Register a watchdog device including handling the legacy
* /dev/watchdog node. /dev/watchdog is actually a miscdevice and
* thus we set it up like that.
*/
int watchdog_dev_register(struct watchdog_device *wdd)
{
struct device *dev;
dev_t devno;
int ret;
devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
ret = watchdog_cdev_register(wdd, devno);
if (ret)
return ret;
dev = device_create_with_groups(&watchdog_class, wdd->parent,
devno, wdd, wdd->groups,
"watchdog%d", wdd->id);
if (IS_ERR(dev)) {
watchdog_cdev_unregister(wdd);
return PTR_ERR(dev);
}
return ret;
}
/*
* watchdog_dev_unregister: unregister a watchdog device
* @watchdog: watchdog device
*
* Unregister watchdog device and if needed the legacy
* /dev/watchdog device.
*/
void watchdog_dev_unregister(struct watchdog_device *wdd)
{
device_destroy(&watchdog_class, wdd->wd_data->cdev.dev);
watchdog_cdev_unregister(wdd);
}
/*
* watchdog_dev_init: init dev part of watchdog core
*
* Allocate a range of chardev nodes to use for watchdog devices
*/
int __init watchdog_dev_init(void)
{
int err;
err = class_register(&watchdog_class);
if (err < 0) {
pr_err("couldn't register class\n");
return err;
}
err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
if (err < 0) {
pr_err("watchdog: unable to allocate char dev region\n");
class_unregister(&watchdog_class);
return err;
}
return 0;
}
/*
* watchdog_dev_exit: exit dev part of watchdog core
*
* Release the range of chardev nodes used for watchdog devices
*/
void __exit watchdog_dev_exit(void)
{
unregister_chrdev_region(watchdog_devt, MAX_DOGS);
class_unregister(&watchdog_class);
}