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Message-ID: <59b298ec-028b-7585-3477-ff4eabb27b80@roeck-us.net>
Date: Tue, 30 Jul 2019 21:43:10 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Mark Balantzyan <mbalant3@...il.com>
Cc: wim@...ux-watchdog.org, linux-kernel@...r.kernel.org,
linux-watchdog@...r.kernel.org, andrianov@...ras.ru
Subject: Re: [PATCH] watchdog: pc87413: Rewriting of pc87413_wdt driver to use
watchdog subsystem
On 7/30/19 8:22 PM, Mark Balantzyan wrote:
> This patch rewrites the pc87413_wdt driver to use the watchdog subsystem. In
> doing so, it also addresses a potential race condition owing from the
> swc_base_addr variable being used before being set.
>
> Signed-off-by: Mark Balantzyan <mbalant3@...il.com>
>
> ---
> drivers/watchdog/Kconfig | 1 +
> drivers/watchdog/pc87413_wdt.c | 323 ++++-----------------------------
> 2 files changed, 40 insertions(+), 284 deletions(-)
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 9af07fd9..84a7326d 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1166,6 +1166,7 @@ config SCx200_WDT
>
> config PC87413_WDT
> tristate "NS PC87413 watchdog"
> + select WATCHDOG_CORE
> depends on X86
> ---help---
> This is the driver for the hardware watchdog on the PC87413 chipset
> diff --git a/drivers/watchdog/pc87413_wdt.c b/drivers/watchdog/pc87413_wdt.c
> index 06a892e3..60e3cda6 100644
> --- a/drivers/watchdog/pc87413_wdt.c
> +++ b/drivers/watchdog/pc87413_wdt.c
> @@ -22,15 +22,9 @@
>
> #include <linux/module.h>
> #include <linux/types.h>
> -#include <linux/miscdevice.h>
> #include <linux/watchdog.h>
> #include <linux/ioport.h>
> #include <linux/delay.h>
> -#include <linux/notifier.h>
> -#include <linux/fs.h>
> -#include <linux/reboot.h>
> -#include <linux/init.h>
> -#include <linux/spinlock.h>
> #include <linux/moduleparam.h>
> #include <linux/io.h>
> #include <linux/uaccess.h>
> @@ -60,13 +54,9 @@ static int swc_base_addr = -1;
>
> static int timeout = DEFAULT_TIMEOUT; /* timeout value */
> static unsigned long timer_enabled; /* is the timer enabled? */
> -
> -static char expect_close; /* is the close expected? */
> -
> -static DEFINE_SPINLOCK(io_lock); /* to guard us from io races */
> -
> static bool nowayout = WATCHDOG_NOWAYOUT;
>
> +
> /* -- Low level function ----------------------------------------*/
>
> /* Select pins for Watchdog output */
> @@ -151,13 +141,15 @@ static inline void pc87413_swc_bank3(void)
>
> /* Set watchdog timeout to x minutes */
>
> -static inline void pc87413_programm_wdto(char pc87413_time)
> +static int pc87413_set_timeout(struct watchdog_device *wdd, unsigned int t)
> {
> - /* Step 5: Programm WDTO, Twd. */
> - outb_p(pc87413_time, swc_base_addr + WDTO);
> -#ifdef DEBUG
> - pr_info(DPFX "Set WDTO to %d minutes\n", pc87413_time);
> -#endif
> + /* Step 5: Programm watchdog timeout */
> +
> + if ((t < 1) || ( t > 60)) /* arbitrary upper limit */
> + return -EINVAL;
> +
> + timeout = t;
> + return 0;
> }
>
> /* Enable WDEN */
> @@ -216,281 +208,61 @@ static inline void pc87413_disable_sw_wd_trg(void)
>
> /* -- Higher level functions ------------------------------------*/
>
> -/* Enable the watchdog */
> +/* Enable/start the watchdog */
>
> -static void pc87413_enable(void)
> +static int pc87413_start(struct watchdog_device *wdd)
> {
> - spin_lock(&io_lock);
> -
> pc87413_swc_bank3();
> - pc87413_programm_wdto(timeout);
> + pc87413_set_timeout(wdd,timeout);
> pc87413_enable_wden();
> pc87413_enable_sw_wd_tren();
> pc87413_enable_sw_wd_trg();
> -
> - spin_unlock(&io_lock);
> + return 0;
> }
>
> -/* Disable the watchdog */
> +/* Disable/stop the watchdog */
>
> -static void pc87413_disable(void)
> +static int pc87413_stop(struct watchdog_device *wdd)
> {
> - spin_lock(&io_lock);
> -
> pc87413_swc_bank3();
> pc87413_disable_sw_wd_tren();
> pc87413_disable_sw_wd_trg();
> - pc87413_programm_wdto(0);
> -
> - spin_unlock(&io_lock);
> + pc87413_set_timeout(wdd,0);
> + return 0;
> }
>
> -/* Refresh the watchdog */
> +/* Refresh/keepalive the watchdog */
>
> -static void pc87413_refresh(void)
> +static int pc87413_keepalive(struct watchdog_device *wdd)
> {
> - spin_lock(&io_lock);
> -
> pc87413_swc_bank3();
> pc87413_disable_sw_wd_tren();
> pc87413_disable_sw_wd_trg();
> - pc87413_programm_wdto(timeout);
> + pc87413_set_timeout(wdd,timeout);
> pc87413_enable_wden();
> pc87413_enable_sw_wd_tren();
> pc87413_enable_sw_wd_trg();
> -
> - spin_unlock(&io_lock);
> -}
> -
> -/* -- File operations -------------------------------------------*/
> -
> -/**
> - * pc87413_open:
> - * @inode: inode of device
> - * @file: file handle to device
> - *
> - */
> -
> -static int pc87413_open(struct inode *inode, struct file *file)
> -{
> - /* /dev/watchdog can only be opened once */
> -
> - if (test_and_set_bit(0, &timer_enabled))
> - return -EBUSY;
> -
> - if (nowayout)
> - __module_get(THIS_MODULE);
> -
> - /* Reload and activate timer */
> - pc87413_refresh();
> -
> - pr_info("Watchdog enabled. Timeout set to %d minute(s).\n", timeout);
> -
> - return nonseekable_open(inode, file);
> -}
> -
> -/**
> - * pc87413_release:
> - * @inode: inode to board
> - * @file: file handle to board
> - *
> - * The watchdog has a configurable API. There is a religious dispute
> - * between people who want their watchdog to be able to shut down and
> - * those who want to be sure if the watchdog manager dies the machine
> - * reboots. In the former case we disable the counters, in the latter
> - * case you have to open it again very soon.
> - */
> -
> -static int pc87413_release(struct inode *inode, struct file *file)
> -{
> - /* Shut off the timer. */
> -
> - if (expect_close == 42) {
> - pc87413_disable();
> - pr_info("Watchdog disabled, sleeping again...\n");
> - } else {
> - pr_crit("Unexpected close, not stopping watchdog!\n");
> - pc87413_refresh();
> - }
> - clear_bit(0, &timer_enabled);
> - expect_close = 0;
> return 0;
> }
>
> -/**
> - * pc87413_status:
> - *
> - * return, if the watchdog is enabled (timeout is set...)
> - */
> -
> -
> -static int pc87413_status(void)
> -{
> - return 0; /* currently not supported */
> -}
> -
> -/**
> - * pc87413_write:
> - * @file: file handle to the watchdog
> - * @data: data buffer to write
> - * @len: length in bytes
> - * @ppos: pointer to the position to write. No seeks allowed
> - *
> - * A write to a watchdog device is defined as a keepalive signal. Any
> - * write of data will do, as we we don't define content meaning.
> - */
> -
> -static ssize_t pc87413_write(struct file *file, const char __user *data,
> - size_t len, loff_t *ppos)
> -{
> - /* See if we got the magic character 'V' and reload the timer */
> - if (len) {
> - if (!nowayout) {
> - size_t i;
> -
> - /* reset expect flag */
> - expect_close = 0;
> -
> - /* scan to see whether or not we got the
> - magic character */
> - for (i = 0; i != len; i++) {
> - char c;
> - if (get_user(c, data + i))
> - return -EFAULT;
> - if (c == 'V')
> - expect_close = 42;
> - }
> - }
> -
> - /* someone wrote to us, we should reload the timer */
> - pc87413_refresh();
> - }
> - return len;
> -}
> -
> -/**
> - * pc87413_ioctl:
> - * @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. We only actually usefully support
> - * querying capabilities and current status.
> - */
> -
> -static long pc87413_ioctl(struct file *file, unsigned int cmd,
> - unsigned long arg)
> -{
> - int new_timeout;
> -
> - union {
> - struct watchdog_info __user *ident;
> - int __user *i;
> - } uarg;
> -
> - static const struct watchdog_info ident = {
> - .options = WDIOF_KEEPALIVEPING |
> - WDIOF_SETTIMEOUT |
> - WDIOF_MAGICCLOSE,
> - .firmware_version = 1,
> - .identity = "PC87413(HF/F) watchdog",
> - };
> -
> - uarg.i = (int __user *)arg;
> -
> - switch (cmd) {
> - case WDIOC_GETSUPPORT:
> - return copy_to_user(uarg.ident, &ident,
> - sizeof(ident)) ? -EFAULT : 0;
> - case WDIOC_GETSTATUS:
> - return put_user(pc87413_status(), uarg.i);
> - case WDIOC_GETBOOTSTATUS:
> - return put_user(0, uarg.i);
> - case WDIOC_SETOPTIONS:
> - {
> - int options, retval = -EINVAL;
> - if (get_user(options, uarg.i))
> - return -EFAULT;
> - if (options & WDIOS_DISABLECARD) {
> - pc87413_disable();
> - retval = 0;
> - }
> - if (options & WDIOS_ENABLECARD) {
> - pc87413_enable();
> - retval = 0;
> - }
> - return retval;
> - }
> - case WDIOC_KEEPALIVE:
> - pc87413_refresh();
> -#ifdef DEBUG
> - pr_info(DPFX "keepalive\n");
> -#endif
> - return 0;
> - case WDIOC_SETTIMEOUT:
> - if (get_user(new_timeout, uarg.i))
> - return -EFAULT;
> - /* the API states this is given in secs */
> - new_timeout /= 60;
> - if (new_timeout < 0 || new_timeout > MAX_TIMEOUT)
> - return -EINVAL;
> - timeout = new_timeout;
> - pc87413_refresh();
> - /* fall through and return the new timeout... */
> - case WDIOC_GETTIMEOUT:
> - new_timeout = timeout * 60;
> - return put_user(new_timeout, uarg.i);
> - default:
> - return -ENOTTY;
> - }
> -}
> -
> -/* -- Notifier funtions -----------------------------------------*/
> -
> -/**
> - * notify_sys:
> - * @this: our notifier block
> - * @code: the event being reported
> - * @unused: unused
> - *
> - * Our notifier is called on system shutdowns. We want to turn the card
> - * off at reboot otherwise the machine will reboot again during memory
> - * test or worse yet during the following fsck. This would suck, in fact
> - * trust me - if it happens it does suck.
> - */
> -
> -static int pc87413_notify_sys(struct notifier_block *this,
> - unsigned long code,
> - void *unused)
> -{
> - if (code == SYS_DOWN || code == SYS_HALT)
> - /* Turn the card off */
> - pc87413_disable();
> - return NOTIFY_DONE;
> -}
>
> /* -- Module's structures ---------------------------------------*/
>
> -static const struct file_operations pc87413_fops = {
> - .owner = THIS_MODULE,
> - .llseek = no_llseek,
> - .write = pc87413_write,
> - .unlocked_ioctl = pc87413_ioctl,
> - .open = pc87413_open,
> - .release = pc87413_release,
> -};
>
> -static struct notifier_block pc87413_notifier = {
> - .notifier_call = pc87413_notify_sys,
> +static struct watchdog_ops pc87413wdt_ops = {
> + .owner = THIS_MODULE,
> + .start = pc87413_start,
> + .stop = pc87413_stop,
> + .ping = pc87413_keepalive,
> + .set_timeout = pc87413_set_timeout,
Indentation is off.
> };
>
> -static struct miscdevice pc87413_miscdev = {
> - .minor = WATCHDOG_MINOR,
> - .name = "watchdog",
> - .fops = &pc87413_fops,
> +static struct watchdog_device pc87413wdt_wdd = {
> + .ops = &pc87413wdt_ops,
> + .status = WATCHDOG_NOWAYOUT_INIT_STATUS,
Indentation is off.
> };
>
> +
> /* -- Module init functions -------------------------------------*/
>
> /**
> @@ -498,7 +270,6 @@ static struct miscdevice pc87413_miscdev = {
> *
> * Set up the WDT watchdog board. All we have to do is grab the
> * resources we require and bitch if anyone beat us to them.
> - * The open() function will actually kick the board off.
> */
>
> static int __init pc87413_init(void)
> @@ -508,20 +279,16 @@ static int __init pc87413_init(void)
> pr_info("Version " VERSION " at io 0x%X\n",
> WDT_INDEX_IO_PORT);
>
> + watchdog_set_nowayout(&pc87413wdt_wdd,nowayout);
> +
Should be called right befor4e registering the watchdog.
> if (!request_muxed_region(io, 2, MODNAME))
> return -EBUSY;
>
> - ret = register_reboot_notifier(&pc87413_notifier);
> - if (ret != 0)
> - pr_err("cannot register reboot notifier (err=%d)\n", ret);
> -
> - ret = misc_register(&pc87413_miscdev);
> + watchdog_stop_on_reboot(&pc87413wdt_wdd);
> + ret = watchdog_register_device(&pc87413wdt_wdd);
> if (ret != 0) {
> - pr_err("cannot register miscdev on minor=%d (err=%d)\n",
> - WATCHDOG_MINOR, ret);
> goto reboot_unreg;
> - }
> - pr_info("initialized. timeout=%d min\n", timeout);
> + } pr_info("initialized. timeout=%d min\n", timeout);
Really bad formatting.
>
> pc87413_select_wdt_out();
> pc87413_enable_swc();
> @@ -530,20 +297,16 @@ static int __init pc87413_init(void)
> if (!request_region(swc_base_addr, 0x20, MODNAME)) {
> pr_err("cannot request SWC region at 0x%x\n", swc_base_addr);
> ret = -EBUSY;
> - goto misc_unreg;
> + goto watchdog_unreg;
> }
The point of the original problem was that the misc device was registered before
this region was requested, which caused the race condition. That problem still
exists = the watchdog is registered, and thus may be opened, before this region
is requested.
>
> - pc87413_enable();
> -
> release_region(io, 2);
> return 0;
> -
> -misc_unreg:
> - misc_deregister(&pc87413_miscdev);
> reboot_unreg:
> - unregister_reboot_notifier(&pc87413_notifier);
> release_region(io, 2);
> return ret;
> +watchdog_unreg:
> + watchdog_unregister_device(&pc87413wdt_wdd);
Return value missing. Doesn't the compile complain about that ?
> }
>
> /**
> @@ -558,14 +321,7 @@ reboot_unreg:
>
> static void __exit pc87413_exit(void)
> {
> - /* Stop the timer before we leave */
> - if (!nowayout) {
> - pc87413_disable();
> - pr_info("Watchdog disabled\n");
> - }
> -
> - misc_deregister(&pc87413_miscdev);
> - unregister_reboot_notifier(&pc87413_notifier);
> + watchdog_unregister_device(&pc87413wdt_wdd);
> release_region(swc_base_addr, 0x20);
>
> pr_info("watchdog component driver removed\n");
> @@ -592,4 +348,3 @@ module_param(nowayout, bool, 0);
> MODULE_PARM_DESC(nowayout,
> "Watchdog cannot be stopped once started (default="
> __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> -
>
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