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![Arnd Bergmann](/assets/img/avatar_default.png)
All file_operations should get a .llseek operation so we can make nonseekable_open the default for future file operations without a .llseek pointer. The three cases that we can automatically detect are no_llseek, seq_lseek and default_llseek. For cases where we can we can automatically prove that the file offset is always ignored, we use noop_llseek, which maintains the current behavior of not returning an error from a seek. New drivers should normally not use noop_llseek but instead use no_llseek and call nonseekable_open at open time. Existing drivers can be converted to do the same when the maintainer knows for certain that no user code relies on calling seek on the device file. The generated code is often incorrectly indented and right now contains comments that clarify for each added line why a specific variant was chosen. In the version that gets submitted upstream, the comments will be gone and I will manually fix the indentation, because there does not seem to be a way to do that using coccinelle. Some amount of new code is currently sitting in linux-next that should get the same modifications, which I will do at the end of the merge window. Many thanks to Julia Lawall for helping me learn to write a semantic patch that does all this. ===== begin semantic patch ===== // This adds an llseek= method to all file operations, // as a preparation for making no_llseek the default. // // The rules are // - use no_llseek explicitly if we do nonseekable_open // - use seq_lseek for sequential files // - use default_llseek if we know we access f_pos // - use noop_llseek if we know we don't access f_pos, // but we still want to allow users to call lseek // @ open1 exists @ identifier nested_open; @@ nested_open(...) { <+... nonseekable_open(...) ...+> } @ open exists@ identifier open_f; identifier i, f; identifier open1.nested_open; @@ int open_f(struct inode *i, struct file *f) { <+... ( nonseekable_open(...) | nested_open(...) ) ...+> } @ read disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ read_no_fpos disable optional_qualifier exists @ identifier read_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t read_f(struct file *f, char *p, size_t s, loff_t *off) { ... when != off } @ write @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; expression E; identifier func; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { <+... ( *off = E | *off += E | func(..., off, ...) | E = *off ) ...+> } @ write_no_fpos @ identifier write_f; identifier f, p, s, off; type ssize_t, size_t, loff_t; @@ ssize_t write_f(struct file *f, const char *p, size_t s, loff_t *off) { ... when != off } @ fops0 @ identifier fops; @@ struct file_operations fops = { ... }; @ has_llseek depends on fops0 @ identifier fops0.fops; identifier llseek_f; @@ struct file_operations fops = { ... .llseek = llseek_f, ... }; @ has_read depends on fops0 @ identifier fops0.fops; identifier read_f; @@ struct file_operations fops = { ... .read = read_f, ... }; @ has_write depends on fops0 @ identifier fops0.fops; identifier write_f; @@ struct file_operations fops = { ... .write = write_f, ... }; @ has_open depends on fops0 @ identifier fops0.fops; identifier open_f; @@ struct file_operations fops = { ... .open = open_f, ... }; // use no_llseek if we call nonseekable_open //////////////////////////////////////////// @ nonseekable1 depends on !has_llseek && has_open @ identifier fops0.fops; identifier nso ~= "nonseekable_open"; @@ struct file_operations fops = { ... .open = nso, ... +.llseek = no_llseek, /* nonseekable */ }; @ nonseekable2 depends on !has_llseek @ identifier fops0.fops; identifier open.open_f; @@ struct file_operations fops = { ... .open = open_f, ... +.llseek = no_llseek, /* open uses nonseekable */ }; // use seq_lseek for sequential files ///////////////////////////////////// @ seq depends on !has_llseek @ identifier fops0.fops; identifier sr ~= "seq_read"; @@ struct file_operations fops = { ... .read = sr, ... +.llseek = seq_lseek, /* we have seq_read */ }; // use default_llseek if there is a readdir /////////////////////////////////////////// @ fops1 depends on !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier readdir_e; @@ // any other fop is used that changes pos struct file_operations fops = { ... .readdir = readdir_e, ... +.llseek = default_llseek, /* readdir is present */ }; // use default_llseek if at least one of read/write touches f_pos ///////////////////////////////////////////////////////////////// @ fops2 depends on !fops1 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read.read_f; @@ // read fops use offset struct file_operations fops = { ... .read = read_f, ... +.llseek = default_llseek, /* read accesses f_pos */ }; @ fops3 depends on !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, ... + .llseek = default_llseek, /* write accesses f_pos */ }; // Use noop_llseek if neither read nor write accesses f_pos /////////////////////////////////////////////////////////// @ fops4 depends on !fops1 && !fops2 && !fops3 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; identifier write_no_fpos.write_f; @@ // write fops use offset struct file_operations fops = { ... .write = write_f, .read = read_f, ... +.llseek = noop_llseek, /* read and write both use no f_pos */ }; @ depends on has_write && !has_read && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier write_no_fpos.write_f; @@ struct file_operations fops = { ... .write = write_f, ... +.llseek = noop_llseek, /* write uses no f_pos */ }; @ depends on has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; identifier read_no_fpos.read_f; @@ struct file_operations fops = { ... .read = read_f, ... +.llseek = noop_llseek, /* read uses no f_pos */ }; @ depends on !has_read && !has_write && !fops1 && !fops2 && !has_llseek && !nonseekable1 && !nonseekable2 && !seq @ identifier fops0.fops; @@ struct file_operations fops = { ... +.llseek = noop_llseek, /* no read or write fn */ }; ===== End semantic patch ===== Signed-off-by: Arnd Bergmann <arnd@arndb.de> Cc: Julia Lawall <julia@diku.dk> Cc: Christoph Hellwig <hch@infradead.org>
255 lines
5.5 KiB
C
255 lines
5.5 KiB
C
/*
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* Watchdog driver for Cirrus Logic EP93xx family of devices.
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*
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* Copyright (c) 2004 Ray Lehtiniemi
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* Copyright (c) 2006 Tower Technologies
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* Based on ep93xx driver, bits from alim7101_wdt.c
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*
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* Authors: Ray Lehtiniemi <rayl@mail.com>,
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* Alessandro Zummo <a.zummo@towertech.it>
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*
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* This file is licensed under the terms of the GNU General Public
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* License version 2. This program is licensed "as is" without any
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* warranty of any kind, whether express or implied.
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*
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* This watchdog fires after 250msec, which is a too short interval
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* for us to rely on the user space daemon alone. So we ping the
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* wdt each ~200msec and eventually stop doing it if the user space
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* daemon dies.
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*
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* TODO:
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*
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* - Test last reset from watchdog status
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* - Add a few missing ioctls
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*/
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/miscdevice.h>
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#include <linux/watchdog.h>
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#include <linux/timer.h>
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#include <linux/uaccess.h>
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#include <linux/io.h>
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#include <mach/hardware.h>
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#define WDT_VERSION "0.3"
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#define PFX "ep93xx_wdt: "
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/* default timeout (secs) */
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#define WDT_TIMEOUT 30
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static int nowayout = WATCHDOG_NOWAYOUT;
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static int timeout = WDT_TIMEOUT;
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static struct timer_list timer;
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static unsigned long next_heartbeat;
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static unsigned long wdt_status;
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static unsigned long boot_status;
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#define WDT_IN_USE 0
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#define WDT_OK_TO_CLOSE 1
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#define EP93XX_WDT_REG(x) (EP93XX_WATCHDOG_BASE + (x))
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#define EP93XX_WDT_WATCHDOG EP93XX_WDT_REG(0x00)
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#define EP93XX_WDT_WDSTATUS EP93XX_WDT_REG(0x04)
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/* reset the wdt every ~200ms */
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#define WDT_INTERVAL (HZ/5)
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static void wdt_enable(void)
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{
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__raw_writew(0xaaaa, EP93XX_WDT_WATCHDOG);
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}
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static void wdt_disable(void)
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{
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__raw_writew(0xaa55, EP93XX_WDT_WATCHDOG);
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}
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static inline void wdt_ping(void)
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{
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__raw_writew(0x5555, EP93XX_WDT_WATCHDOG);
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}
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static void wdt_startup(void)
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{
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next_heartbeat = jiffies + (timeout * HZ);
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wdt_enable();
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mod_timer(&timer, jiffies + WDT_INTERVAL);
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}
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static void wdt_shutdown(void)
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{
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del_timer_sync(&timer);
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wdt_disable();
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}
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static void wdt_keepalive(void)
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{
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/* user land ping */
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next_heartbeat = jiffies + (timeout * HZ);
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}
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static int ep93xx_wdt_open(struct inode *inode, struct file *file)
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{
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if (test_and_set_bit(WDT_IN_USE, &wdt_status))
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return -EBUSY;
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clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
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wdt_startup();
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return nonseekable_open(inode, file);
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}
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static ssize_t
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ep93xx_wdt_write(struct file *file, const char __user *data, size_t len,
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loff_t *ppos)
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{
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if (len) {
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if (!nowayout) {
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size_t i;
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clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
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for (i = 0; i != len; i++) {
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char c;
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if (get_user(c, data + i))
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return -EFAULT;
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if (c == 'V')
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set_bit(WDT_OK_TO_CLOSE, &wdt_status);
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else
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clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
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}
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}
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wdt_keepalive();
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}
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return len;
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}
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static const struct watchdog_info ident = {
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.options = WDIOF_CARDRESET | WDIOF_MAGICCLOSE,
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.identity = "EP93xx Watchdog",
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};
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static long ep93xx_wdt_ioctl(struct file *file,
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unsigned int cmd, unsigned long arg)
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{
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int ret = -ENOTTY;
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switch (cmd) {
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case WDIOC_GETSUPPORT:
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ret = copy_to_user((struct watchdog_info __user *)arg, &ident,
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sizeof(ident)) ? -EFAULT : 0;
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break;
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case WDIOC_GETSTATUS:
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ret = put_user(0, (int __user *)arg);
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break;
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case WDIOC_GETBOOTSTATUS:
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ret = put_user(boot_status, (int __user *)arg);
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break;
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case WDIOC_KEEPALIVE:
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wdt_keepalive();
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ret = 0;
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break;
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case WDIOC_GETTIMEOUT:
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/* actually, it is 0.250 seconds.... */
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ret = put_user(1, (int __user *)arg);
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break;
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}
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return ret;
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}
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static int ep93xx_wdt_release(struct inode *inode, struct file *file)
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{
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if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
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wdt_shutdown();
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else
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printk(KERN_CRIT PFX
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"Device closed unexpectedly - timer will not stop\n");
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clear_bit(WDT_IN_USE, &wdt_status);
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clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
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return 0;
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}
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static const struct file_operations ep93xx_wdt_fops = {
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.owner = THIS_MODULE,
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.write = ep93xx_wdt_write,
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.unlocked_ioctl = ep93xx_wdt_ioctl,
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.open = ep93xx_wdt_open,
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.release = ep93xx_wdt_release,
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.llseek = no_llseek,
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};
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static struct miscdevice ep93xx_wdt_miscdev = {
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.minor = WATCHDOG_MINOR,
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.name = "watchdog",
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.fops = &ep93xx_wdt_fops,
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};
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static void ep93xx_timer_ping(unsigned long data)
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{
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if (time_before(jiffies, next_heartbeat))
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wdt_ping();
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/* Re-set the timer interval */
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mod_timer(&timer, jiffies + WDT_INTERVAL);
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}
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static int __init ep93xx_wdt_init(void)
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{
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int err;
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err = misc_register(&ep93xx_wdt_miscdev);
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boot_status = __raw_readl(EP93XX_WDT_WATCHDOG) & 0x01 ? 1 : 0;
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printk(KERN_INFO PFX "EP93XX watchdog, driver version "
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WDT_VERSION "%s\n",
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(__raw_readl(EP93XX_WDT_WATCHDOG) & 0x08)
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? " (nCS1 disable detected)" : "");
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if (timeout < 1 || timeout > 3600) {
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timeout = WDT_TIMEOUT;
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printk(KERN_INFO PFX
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"timeout value must be 1<=x<=3600, using %d\n",
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timeout);
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}
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setup_timer(&timer, ep93xx_timer_ping, 1);
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return err;
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}
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static void __exit ep93xx_wdt_exit(void)
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{
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wdt_shutdown();
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misc_deregister(&ep93xx_wdt_miscdev);
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}
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module_init(ep93xx_wdt_init);
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module_exit(ep93xx_wdt_exit);
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module_param(nowayout, int, 0);
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MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
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module_param(timeout, int, 0);
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MODULE_PARM_DESC(timeout,
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"Watchdog timeout in seconds. (1<=timeout<=3600, default="
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__MODULE_STRING(WDT_TIMEOUT) ")");
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MODULE_AUTHOR("Ray Lehtiniemi <rayl@mail.com>,"
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"Alessandro Zummo <a.zummo@towertech.it>");
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MODULE_DESCRIPTION("EP93xx Watchdog");
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MODULE_LICENSE("GPL");
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MODULE_VERSION(WDT_VERSION);
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MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
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