// SPDX-License-Identifier: GPL-2.0+ /* * watchdog_dev.c * * (c) Copyright 2008-2011 Alan Cox , * All Rights Reserved. * * (c) Copyright 2008-2011 Wim Van Sebroeck . * * (c) Copyright 2021 Hewlett Packard Enterprise Development LP. * * 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 , * Rob Radez , * Rusty Lynch * Satyam Sharma * Randy Dunlap * * 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 /* For character device */ #include /* For the -ENODEV/... values */ #include /* For file operations */ #include /* For __init/__exit/... */ #include /* For hrtimers */ #include /* For printk/panic/... */ #include /* For kthread_work */ #include /* For handling misc devices */ #include /* For module stuff/... */ #include /* For mutexes */ #include /* For memory functions */ #include /* For standard types (like size_t) */ #include /* For watchdog specific items */ #include /* For copy_to_user/put_user/... */ #include "watchdog_core.h" #include "watchdog_pretimeout.h" #include /* 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; static struct kthread_worker *watchdog_kworker; static bool handle_boot_enabled = IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED); static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT; static bool watchdog_past_open_deadline(struct watchdog_core_data *data) { return ktime_after(ktime_get(), data->open_deadline); } static void watchdog_set_open_deadline(struct watchdog_core_data *data) { data->open_deadline = open_timeout ? ktime_get() + ktime_set(open_timeout, 0) : KTIME_MAX; } static inline bool watchdog_need_worker(struct watchdog_device *wdd) { /* All variables in milli-seconds */ unsigned int hm = wdd->max_hw_heartbeat_ms; unsigned int t = wdd->timeout * 1000; /* * A worker to generate heartbeat requests is needed if all of the * following conditions are true. * - Userspace activated the watchdog. * - The driver provided a value for the maximum hardware timeout, and * thus is aware that the framework supports generating heartbeat * requests. * - Userspace requests a longer timeout than the hardware can handle. * * Alternatively, if userspace has not opened the watchdog * device, we take care of feeding the watchdog if it is * running. */ return (hm && watchdog_active(wdd) && t > hm) || (t && !watchdog_active(wdd) && watchdog_hw_running(wdd)); } static ktime_t watchdog_next_keepalive(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; unsigned int timeout_ms = wdd->timeout * 1000; ktime_t keepalive_interval; ktime_t last_heartbeat, latest_heartbeat; ktime_t virt_timeout; unsigned int hw_heartbeat_ms; if (watchdog_active(wdd)) virt_timeout = ktime_add(wd_data->last_keepalive, ms_to_ktime(timeout_ms)); else virt_timeout = wd_data->open_deadline; hw_heartbeat_ms = min_not_zero(timeout_ms, wdd->max_hw_heartbeat_ms); keepalive_interval = ms_to_ktime(hw_heartbeat_ms / 2); /* * To ensure that the watchdog times out wdd->timeout seconds * after the most recent ping from userspace, the last * worker ping has to come in hw_heartbeat_ms before this timeout. */ last_heartbeat = ktime_sub(virt_timeout, ms_to_ktime(hw_heartbeat_ms)); latest_heartbeat = ktime_sub(last_heartbeat, ktime_get()); if (ktime_before(latest_heartbeat, keepalive_interval)) return latest_heartbeat; return keepalive_interval; } static inline void watchdog_update_worker(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; if (watchdog_need_worker(wdd)) { ktime_t t = watchdog_next_keepalive(wdd); if (t > 0) hrtimer_start(&wd_data->timer, t, HRTIMER_MODE_REL_HARD); } else { hrtimer_cancel(&wd_data->timer); } } static int __watchdog_ping(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; ktime_t earliest_keepalive, now; int err; earliest_keepalive = ktime_add(wd_data->last_hw_keepalive, ms_to_ktime(wdd->min_hw_heartbeat_ms)); now = ktime_get(); if (ktime_after(earliest_keepalive, now)) { hrtimer_start(&wd_data->timer, ktime_sub(earliest_keepalive, now), HRTIMER_MODE_REL_HARD); return 0; } wd_data->last_hw_keepalive = now; if (wdd->ops->ping) { err = wdd->ops->ping(wdd); /* ping the watchdog */ trace_watchdog_ping(wdd, err); } else { err = wdd->ops->start(wdd); /* restart watchdog */ trace_watchdog_start(wdd, err); } if (err == 0) watchdog_hrtimer_pretimeout_start(wdd); watchdog_update_worker(wdd); return err; } /* * watchdog_ping - ping the watchdog * @wdd: The watchdog device to ping * * 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. * The caller must hold wd_data->lock. * * Return: 0 on success, error otherwise. */ static int watchdog_ping(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; if (!watchdog_active(wdd) && !watchdog_hw_running(wdd)) return 0; set_bit(_WDOG_KEEPALIVE, &wd_data->status); wd_data->last_keepalive = ktime_get(); return __watchdog_ping(wdd); } static bool watchdog_worker_should_ping(struct watchdog_core_data *wd_data) { struct watchdog_device *wdd = wd_data->wdd; if (!wdd) return false; if (watchdog_active(wdd)) return true; return watchdog_hw_running(wdd) && !watchdog_past_open_deadline(wd_data); } static void watchdog_ping_work(struct kthread_work *work) { struct watchdog_core_data *wd_data; wd_data = container_of(work, struct watchdog_core_data, work); mutex_lock(&wd_data->lock); if (watchdog_worker_should_ping(wd_data)) __watchdog_ping(wd_data->wdd); mutex_unlock(&wd_data->lock); } static enum hrtimer_restart watchdog_timer_expired(struct hrtimer *timer) { struct watchdog_core_data *wd_data; wd_data = container_of(timer, struct watchdog_core_data, timer); kthread_queue_work(watchdog_kworker, &wd_data->work); return HRTIMER_NORESTART; } /* * watchdog_start - wrapper to start the watchdog * @wdd: The watchdog device to start * * Start the watchdog if it is not active and mark it active. * The caller must hold wd_data->lock. * * Return: 0 on success or a negative errno code for failure. */ static int watchdog_start(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; ktime_t started_at; int err; if (watchdog_active(wdd)) return 0; set_bit(_WDOG_KEEPALIVE, &wd_data->status); started_at = ktime_get(); if (watchdog_hw_running(wdd) && wdd->ops->ping) { err = __watchdog_ping(wdd); if (err == 0) { set_bit(WDOG_ACTIVE, &wdd->status); watchdog_hrtimer_pretimeout_start(wdd); } } else { err = wdd->ops->start(wdd); trace_watchdog_start(wdd, err); if (err == 0) { set_bit(WDOG_ACTIVE, &wdd->status); wd_data->last_keepalive = started_at; wd_data->last_hw_keepalive = started_at; watchdog_update_worker(wdd); watchdog_hrtimer_pretimeout_start(wdd); } } return err; } /* * watchdog_stop - wrapper to stop the watchdog * @wdd: The watchdog device to stop * * Stop the watchdog if it is still active and unmark it active. * If the 'nowayout' feature was set, the watchdog cannot be stopped. * The caller must hold wd_data->lock. * * Return: 0 on success or a negative errno code for failure. */ static int watchdog_stop(struct watchdog_device *wdd) { int err = 0; 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; } if (wdd->ops->stop) { clear_bit(WDOG_HW_RUNNING, &wdd->status); err = wdd->ops->stop(wdd); trace_watchdog_stop(wdd, err); } else { set_bit(WDOG_HW_RUNNING, &wdd->status); } if (err == 0) { clear_bit(WDOG_ACTIVE, &wdd->status); watchdog_update_worker(wdd); watchdog_hrtimer_pretimeout_stop(wdd); } return err; } /* * watchdog_get_status - wrapper to get the watchdog status * @wdd: The watchdog device to get the status from * * Get the watchdog's status flags. * The caller must hold wd_data->lock. * * Return: watchdog's status flags. */ static unsigned int watchdog_get_status(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; unsigned int status; if (wdd->ops->status) status = wdd->ops->status(wdd); else status = wdd->bootstatus & (WDIOF_CARDRESET | WDIOF_OVERHEAT | WDIOF_FANFAULT | WDIOF_EXTERN1 | WDIOF_EXTERN2 | WDIOF_POWERUNDER | WDIOF_POWEROVER); if (test_bit(_WDOG_ALLOW_RELEASE, &wd_data->status)) status |= WDIOF_MAGICCLOSE; if (test_and_clear_bit(_WDOG_KEEPALIVE, &wd_data->status)) status |= WDIOF_KEEPALIVEPING; if (IS_ENABLED(CONFIG_WATCHDOG_HRTIMER_PRETIMEOUT)) status |= WDIOF_PRETIMEOUT; return status; } /* * 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. * * Return: 0 if successful, error otherwise. */ static int watchdog_set_timeout(struct watchdog_device *wdd, unsigned int timeout) { int err = 0; if (!(wdd->info->options & WDIOF_SETTIMEOUT)) return -EOPNOTSUPP; if (watchdog_timeout_invalid(wdd, timeout)) return -EINVAL; if (wdd->ops->set_timeout) { err = wdd->ops->set_timeout(wdd, timeout); trace_watchdog_set_timeout(wdd, timeout, err); } else { wdd->timeout = timeout; /* Disable pretimeout if it doesn't fit the new timeout */ if (wdd->pretimeout >= wdd->timeout) wdd->pretimeout = 0; } watchdog_update_worker(wdd); return err; } /* * watchdog_set_pretimeout - set the watchdog timer pretimeout * @wdd: The watchdog device to set the timeout for * @timeout: pretimeout to set in seconds * * Return: 0 if successful, error otherwise. */ static int watchdog_set_pretimeout(struct watchdog_device *wdd, unsigned int timeout) { int err = 0; if (!watchdog_have_pretimeout(wdd)) return -EOPNOTSUPP; if (watchdog_pretimeout_invalid(wdd, timeout)) return -EINVAL; if (wdd->ops->set_pretimeout && (wdd->info->options & WDIOF_PRETIMEOUT)) err = wdd->ops->set_pretimeout(wdd, timeout); else wdd->pretimeout = timeout; return err; } /* * 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 * * Get the time before a watchdog will reboot (if not pinged). * The caller must hold wd_data->lock. * * Return: 0 if successful, error otherwise. */ 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 sysfs_emit(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status)); } static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t len) { struct watchdog_device *wdd = dev_get_drvdata(dev); unsigned int value; int ret; ret = kstrtouint(buf, 0, &value); if (ret) return ret; if (value > 1) return -EINVAL; /* nowayout cannot be disabled once set */ if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value) return -EPERM; watchdog_set_nowayout(wdd, value); return len; } static DEVICE_ATTR_RW(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 sysfs_emit(buf, "0x%x\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 sysfs_emit(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 = sysfs_emit(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 sysfs_emit(buf, "%u\n", wdd->timeout); } static DEVICE_ATTR_RO(timeout); static ssize_t min_timeout_show(struct device *dev, struct device_attribute *attr, char *buf) { struct watchdog_device *wdd = dev_get_drvdata(dev); return sysfs_emit(buf, "%u\n", wdd->min_timeout); } static DEVICE_ATTR_RO(min_timeout); static ssize_t max_timeout_show(struct device *dev, struct device_attribute *attr, char *buf) { struct watchdog_device *wdd = dev_get_drvdata(dev); return sysfs_emit(buf, "%u\n", wdd->max_timeout); } static DEVICE_ATTR_RO(max_timeout); static ssize_t pretimeout_show(struct device *dev, struct device_attribute *attr, char *buf) { struct watchdog_device *wdd = dev_get_drvdata(dev); return sysfs_emit(buf, "%u\n", wdd->pretimeout); } static DEVICE_ATTR_RO(pretimeout); static ssize_t identity_show(struct device *dev, struct device_attribute *attr, char *buf) { struct watchdog_device *wdd = dev_get_drvdata(dev); return sysfs_emit(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 sysfs_emit(buf, "active\n"); return sysfs_emit(buf, "inactive\n"); } static DEVICE_ATTR_RO(state); static ssize_t pretimeout_available_governors_show(struct device *dev, struct device_attribute *attr, char *buf) { return watchdog_pretimeout_available_governors_get(buf); } static DEVICE_ATTR_RO(pretimeout_available_governors); static ssize_t pretimeout_governor_show(struct device *dev, struct device_attribute *attr, char *buf) { struct watchdog_device *wdd = dev_get_drvdata(dev); return watchdog_pretimeout_governor_get(wdd, buf); } static ssize_t pretimeout_governor_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { struct watchdog_device *wdd = dev_get_drvdata(dev); int ret = watchdog_pretimeout_governor_set(wdd, buf); if (!ret) ret = count; return ret; } static DEVICE_ATTR_RW(pretimeout_governor); static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr, int n) { struct device *dev = kobj_to_dev(kobj); struct watchdog_device *wdd = dev_get_drvdata(dev); umode_t mode = attr->mode; if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft) mode = 0; else if (attr == &dev_attr_pretimeout.attr && !watchdog_have_pretimeout(wdd)) mode = 0; else if ((attr == &dev_attr_pretimeout_governor.attr || attr == &dev_attr_pretimeout_available_governors.attr) && (!watchdog_have_pretimeout(wdd) || !IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_GOV))) mode = 0; return mode; } static struct attribute *wdt_attrs[] = { &dev_attr_state.attr, &dev_attr_identity.attr, &dev_attr_timeout.attr, &dev_attr_min_timeout.attr, &dev_attr_max_timeout.attr, &dev_attr_pretimeout.attr, &dev_attr_timeleft.attr, &dev_attr_bootstatus.attr, &dev_attr_status.attr, &dev_attr_nowayout.attr, &dev_attr_pretimeout_governor.attr, &dev_attr_pretimeout_available_governors.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. * * Return: 0 if successful, error otherwise. */ 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). * * Return: @len if successful, error otherwise. */ 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. * * Return: 0 if successful, error otherwise. */ 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; fallthrough; 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; case WDIOC_SETPRETIMEOUT: if (get_user(val, p)) { err = -EFAULT; break; } err = watchdog_set_pretimeout(wdd, val); break; case WDIOC_GETPRETIMEOUT: err = put_user(wdd->pretimeout, 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. * * Return: 0 if successful, error otherwise. */ static int watchdog_open(struct inode *inode, struct file *file) { struct watchdog_core_data *wd_data; struct watchdog_device *wdd; bool hw_running; 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. */ hw_running = watchdog_hw_running(wdd); if (!hw_running && !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; if (!hw_running) get_device(&wd_data->dev); /* * open_timeout only applies for the first open from * userspace. Set open_deadline to infinity so that the kernel * will take care of an always-running hardware watchdog in * case the device gets magic-closed or WDIOS_DISABLECARD is * applied. */ wd_data->open_deadline = KTIME_MAX; /* dev/watchdog is a virtual (and thus non-seekable) filesystem */ return stream_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 device *dev) { struct watchdog_core_data *wd_data; wd_data = container_of(dev, struct watchdog_core_data, dev); 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. * * Always returns 0. */ 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; bool running; 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 (!watchdog_active(wdd)) 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); } watchdog_update_worker(wdd); /* make sure that /dev/watchdog can be re-opened */ clear_bit(_WDOG_DEV_OPEN, &wd_data->status); done: running = wdd && watchdog_hw_running(wdd); mutex_unlock(&wd_data->lock); /* * Allow the owner module to be unloaded again unless the watchdog * is still running. If the watchdog is still running, it can not * be stopped, and its driver must not be unloaded. */ if (!running) { module_put(wd_data->cdev.owner); put_device(&wd_data->dev); } return 0; } static const struct file_operations watchdog_fops = { .owner = THIS_MODULE, .write = watchdog_write, .unlocked_ioctl = watchdog_ioctl, .compat_ioctl = compat_ptr_ioctl, .open = watchdog_open, .release = watchdog_release, }; static struct miscdevice watchdog_miscdev = { .minor = WATCHDOG_MINOR, .name = "watchdog", .fops = &watchdog_fops, }; static struct class watchdog_class = { .name = "watchdog", .owner = THIS_MODULE, .dev_groups = wdt_groups, }; /* * watchdog_cdev_register - register watchdog character device * @wdd: Watchdog device * * 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. * * Return: 0 if successful, error otherwise. */ static int watchdog_cdev_register(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data; int err; wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL); if (!wd_data) return -ENOMEM; mutex_init(&wd_data->lock); wd_data->wdd = wdd; wdd->wd_data = wd_data; if (IS_ERR_OR_NULL(watchdog_kworker)) { kfree(wd_data); return -ENODEV; } device_initialize(&wd_data->dev); wd_data->dev.devt = MKDEV(MAJOR(watchdog_devt), wdd->id); wd_data->dev.class = &watchdog_class; wd_data->dev.parent = wdd->parent; wd_data->dev.groups = wdd->groups; wd_data->dev.release = watchdog_core_data_release; dev_set_drvdata(&wd_data->dev, wdd); err = dev_set_name(&wd_data->dev, "watchdog%d", wdd->id); if (err) { put_device(&wd_data->dev); return err; } kthread_init_work(&wd_data->work, watchdog_ping_work); hrtimer_init(&wd_data->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); wd_data->timer.function = watchdog_timer_expired; watchdog_hrtimer_pretimeout_init(wdd); 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; put_device(&wd_data->dev); return err; } } /* Fill in the data structures */ cdev_init(&wd_data->cdev, &watchdog_fops); /* Add the device */ err = cdev_device_add(&wd_data->cdev, &wd_data->dev); 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; } put_device(&wd_data->dev); return err; } wd_data->cdev.owner = wdd->ops->owner; /* Record time of most recent heartbeat as 'just before now'. */ wd_data->last_hw_keepalive = ktime_sub(ktime_get(), 1); watchdog_set_open_deadline(wd_data); /* * If the watchdog is running, prevent its driver from being unloaded, * and schedule an immediate ping. */ if (watchdog_hw_running(wdd)) { __module_get(wdd->ops->owner); get_device(&wd_data->dev); if (handle_boot_enabled) hrtimer_start(&wd_data->timer, 0, HRTIMER_MODE_REL_HARD); else pr_info("watchdog%d running and kernel based pre-userspace handler disabled\n", wdd->id); } return 0; } /* * watchdog_cdev_unregister - unregister watchdog character device * @wdd: 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_device_del(&wd_data->cdev, &wd_data->dev); if (wdd->id == 0) { misc_deregister(&watchdog_miscdev); old_wd_data = NULL; } if (watchdog_active(wdd) && test_bit(WDOG_STOP_ON_UNREGISTER, &wdd->status)) { watchdog_stop(wdd); } watchdog_hrtimer_pretimeout_stop(wdd); mutex_lock(&wd_data->lock); wd_data->wdd = NULL; wdd->wd_data = NULL; mutex_unlock(&wd_data->lock); hrtimer_cancel(&wd_data->timer); kthread_cancel_work_sync(&wd_data->work); put_device(&wd_data->dev); } /** * 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. * * Return: 0 if successful, error otherwise. */ int watchdog_dev_register(struct watchdog_device *wdd) { int ret; ret = watchdog_cdev_register(wdd); if (ret) return ret; ret = watchdog_register_pretimeout(wdd); if (ret) watchdog_cdev_unregister(wdd); return ret; } /** * watchdog_dev_unregister - unregister a watchdog device * @wdd: watchdog device * * Unregister watchdog device and if needed the legacy * /dev/watchdog device. */ void watchdog_dev_unregister(struct watchdog_device *wdd) { watchdog_unregister_pretimeout(wdd); watchdog_cdev_unregister(wdd); } /** * watchdog_set_last_hw_keepalive - set last HW keepalive time for watchdog * @wdd: Watchdog device * @last_ping_ms: Time since last HW heartbeat * * Adjusts the last known HW keepalive time for a watchdog timer. * This is needed if the watchdog is already running when the probe * function is called, and it can't be pinged immediately. This * function must be called immediately after watchdog registration, * and min_hw_heartbeat_ms must be set for this to be useful. * * Return: 0 if successful, error otherwise. */ int watchdog_set_last_hw_keepalive(struct watchdog_device *wdd, unsigned int last_ping_ms) { struct watchdog_core_data *wd_data; ktime_t now; if (!wdd) return -EINVAL; wd_data = wdd->wd_data; now = ktime_get(); wd_data->last_hw_keepalive = ktime_sub(now, ms_to_ktime(last_ping_ms)); if (watchdog_hw_running(wdd) && handle_boot_enabled) return __watchdog_ping(wdd); return 0; } EXPORT_SYMBOL_GPL(watchdog_set_last_hw_keepalive); /** * watchdog_dev_init - init dev part of watchdog core * * Allocate a range of chardev nodes to use for watchdog devices. * * Return: 0 if successful, error otherwise. */ int __init watchdog_dev_init(void) { int err; watchdog_kworker = kthread_create_worker(0, "watchdogd"); if (IS_ERR(watchdog_kworker)) { pr_err("Failed to create watchdog kworker\n"); return PTR_ERR(watchdog_kworker); } sched_set_fifo(watchdog_kworker->task); err = class_register(&watchdog_class); if (err < 0) { pr_err("couldn't register class\n"); goto err_register; } err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); if (err < 0) { pr_err("watchdog: unable to allocate char dev region\n"); goto err_alloc; } return 0; err_alloc: class_unregister(&watchdog_class); err_register: kthread_destroy_worker(watchdog_kworker); return err; } /** * 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); kthread_destroy_worker(watchdog_kworker); } int watchdog_dev_suspend(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; int ret = 0; if (!wdd->wd_data) return -ENODEV; /* ping for the last time before suspend */ mutex_lock(&wd_data->lock); if (watchdog_worker_should_ping(wd_data)) ret = __watchdog_ping(wd_data->wdd); mutex_unlock(&wd_data->lock); if (ret) return ret; /* * make sure that watchdog worker will not kick in when the wdog is * suspended */ hrtimer_cancel(&wd_data->timer); kthread_cancel_work_sync(&wd_data->work); return 0; } int watchdog_dev_resume(struct watchdog_device *wdd) { struct watchdog_core_data *wd_data = wdd->wd_data; int ret = 0; if (!wdd->wd_data) return -ENODEV; /* * __watchdog_ping will also retrigger hrtimer and therefore restore the * ping worker if needed. */ mutex_lock(&wd_data->lock); if (watchdog_worker_should_ping(wd_data)) ret = __watchdog_ping(wd_data->wdd); mutex_unlock(&wd_data->lock); return ret; } module_param(handle_boot_enabled, bool, 0444); MODULE_PARM_DESC(handle_boot_enabled, "Watchdog core auto-updates boot enabled watchdogs before userspace takes over (default=" __MODULE_STRING(IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED)) ")"); module_param(open_timeout, uint, 0644); MODULE_PARM_DESC(open_timeout, "Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default=" __MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");