1 files changed, 3334 insertions, 0 deletions

diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
new file mode 100644
index 000000000000..6556f7452ba6
--- /dev/null
+++ b/drivers/tty/tty_io.c
@@ -0,0 +1,3334 @@
+/*
+ *  Copyright (C) 1991, 1992  Linus Torvalds
+ */
+
+/*
+ * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
+ * or rs-channels. It also implements echoing, cooked mode etc.
+ *
+ * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
+ *
+ * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
+ * tty_struct and tty_queue structures.  Previously there was an array
+ * of 256 tty_struct's which was statically allocated, and the
+ * tty_queue structures were allocated at boot time.  Both are now
+ * dynamically allocated only when the tty is open.
+ *
+ * Also restructured routines so that there is more of a separation
+ * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
+ * the low-level tty routines (serial.c, pty.c, console.c).  This
+ * makes for cleaner and more compact code.  -TYT, 9/17/92
+ *
+ * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
+ * which can be dynamically activated and de-activated by the line
+ * discipline handling modules (like SLIP).
+ *
+ * NOTE: pay no attention to the line discipline code (yet); its
+ * interface is still subject to change in this version...
+ * -- TYT, 1/31/92
+ *
+ * Added functionality to the OPOST tty handling.  No delays, but all
+ * other bits should be there.
+ *      -- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
+ *
+ * Rewrote canonical mode and added more termios flags.
+ *      -- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
+ *
+ * Reorganized FASYNC support so mouse code can share it.
+ *      -- ctm@ardi.com, 9Sep95
+ *
+ * New TIOCLINUX variants added.
+ *      -- mj@k332.feld.cvut.cz, 19-Nov-95
+ *
+ * Restrict vt switching via ioctl()
+ *      -- grif@cs.ucr.edu, 5-Dec-95
+ *
+ * Move console and virtual terminal code to more appropriate files,
+ * implement CONFIG_VT and generalize console device interface.
+ *      -- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
+ *
+ * Rewrote tty_init_dev and tty_release_dev to eliminate races.
+ *      -- Bill Hawes <whawes@star.net>, June 97
+ *
+ * Added devfs support.
+ *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
+ *
+ * Added support for a Unix98-style ptmx device.
+ *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
+ *
+ * Reduced memory usage for older ARM systems
+ *      -- Russell King <rmk@arm.linux.org.uk>
+ *
+ * Move do_SAK() into process context.  Less stack use in devfs functions.
+ * alloc_tty_struct() always uses kmalloc()
+ *                       -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
+ */
+
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/fcntl.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/devpts_fs.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/console.h>
+#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/kd.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/seq_file.h>
+#include <linux/serial.h>
+
+#include <linux/uaccess.h>
+#include <asm/system.h>
+
+#include <linux/kbd_kern.h>
+#include <linux/vt_kern.h>
+#include <linux/selection.h>
+
+#include <linux/kmod.h>
+#include <linux/nsproxy.h>
+
+#undef TTY_DEBUG_HANGUP
+
+#define TTY_PARANOIA_CHECK 1
+#define CHECK_TTY_COUNT 1
+
+struct ktermios tty_std_termios = {     /* for the benefit of tty drivers  */
+        .c_iflag = ICRNL | IXON,
+        .c_oflag = OPOST | ONLCR,
+        .c_cflag = B38400 | CS8 | CREAD | HUPCL,
+        .c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
+                   ECHOCTL | ECHOKE | IEXTEN,
+        .c_cc = INIT_C_CC,
+        .c_ispeed = 38400,
+        .c_ospeed = 38400
+};
+
+EXPORT_SYMBOL(tty_std_termios);
+
+/* This list gets poked at by procfs and various bits of boot up code. This
+   could do with some rationalisation such as pulling the tty proc function
+   into this file */
+
+LIST_HEAD(tty_drivers);                 /* linked list of tty drivers */
+
+/* Mutex to protect creating and releasing a tty. This is shared with
+   vt.c for deeply disgusting hack reasons */
+DEFINE_MUTEX(tty_mutex);
+EXPORT_SYMBOL(tty_mutex);
+
+/* Spinlock to protect the tty->tty_files list */
+DEFINE_SPINLOCK(tty_files_lock);
+
+static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
+static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
+ssize_t redirected_tty_write(struct file *, const char __user *,
+                                                        size_t, loff_t *);
+static unsigned int tty_poll(struct file *, poll_table *);
+static int tty_open(struct inode *, struct file *);
+long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
+#ifdef CONFIG_COMPAT
+static long tty_compat_ioctl(struct file *file, unsigned int cmd,
+                                unsigned long arg);
+#else
+#define tty_compat_ioctl NULL
+#endif
+static int __tty_fasync(int fd, struct file *filp, int on);
+static int tty_fasync(int fd, struct file *filp, int on);
+static void release_tty(struct tty_struct *tty, int idx);
+static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
+static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty);
+
+/**
+ *      alloc_tty_struct        -       allocate a tty object
+ *
+ *      Return a new empty tty structure. The data fields have not
+ *      been initialized in any way but has been zeroed
+ *
+ *      Locking: none
+ */
+
+struct tty_struct *alloc_tty_struct(void)
+{
+        return kzalloc(sizeof(struct tty_struct), GFP_KERNEL);
+}
+
+/**
+ *      free_tty_struct         -       free a disused tty
+ *      @tty: tty struct to free
+ *
+ *      Free the write buffers, tty queue and tty memory itself.
+ *
+ *      Locking: none. Must be called after tty is definitely unused
+ */
+
+void free_tty_struct(struct tty_struct *tty)
+{
+        if (tty->dev)
+                put_device(tty->dev);
+        kfree(tty->write_buf);
+        tty_buffer_free_all(tty);
+        kfree(tty);
+}
+
+static inline struct tty_struct *file_tty(struct file *file)
+{
+        return ((struct tty_file_private *)file->private_data)->tty;
+}
+
+/* Associate a new file with the tty structure */
+int tty_add_file(struct tty_struct *tty, struct file *file)
+{
+        struct tty_file_private *priv;
+
+        priv = kmalloc(sizeof(*priv), GFP_KERNEL);
+        if (!priv)
+                return -ENOMEM;
+
+        priv->tty = tty;
+        priv->file = file;
+        file->private_data = priv;
+
+        spin_lock(&tty_files_lock);
+        list_add(&priv->list, &tty->tty_files);
+        spin_unlock(&tty_files_lock);
+
+        return 0;
+}
+
+/* Delete file from its tty */
+void tty_del_file(struct file *file)
+{
+        struct tty_file_private *priv = file->private_data;
+
+        spin_lock(&tty_files_lock);
+        list_del(&priv->list);
+        spin_unlock(&tty_files_lock);
+        file->private_data = NULL;
+        kfree(priv);
+}
+
+
+#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)
+
+/**
+ *      tty_name        -       return tty naming
+ *      @tty: tty structure
+ *      @buf: buffer for output
+ *
+ *      Convert a tty structure into a name. The name reflects the kernel
+ *      naming policy and if udev is in use may not reflect user space
+ *
+ *      Locking: none
+ */
+
+char *tty_name(struct tty_struct *tty, char *buf)
+{
+        if (!tty) /* Hmm.  NULL pointer.  That's fun. */
+                strcpy(buf, "NULL tty");
+        else
+                strcpy(buf, tty->name);
+        return buf;
+}
+
+EXPORT_SYMBOL(tty_name);
+
+int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
+                              const char *routine)
+{
+#ifdef TTY_PARANOIA_CHECK
+        if (!tty) {
+                printk(KERN_WARNING
+                        "null TTY for (%d:%d) in %s\n",
+                        imajor(inode), iminor(inode), routine);
+                return 1;
+        }
+        if (tty->magic != TTY_MAGIC) {
+                printk(KERN_WARNING
+                        "bad magic number for tty struct (%d:%d) in %s\n",
+                        imajor(inode), iminor(inode), routine);
+                return 1;
+        }
+#endif
+        return 0;
+}
+
+static int check_tty_count(struct tty_struct *tty, const char *routine)
+{
+#ifdef CHECK_TTY_COUNT
+        struct list_head *p;
+        int count = 0;
+
+        spin_lock(&tty_files_lock);
+        list_for_each(p, &tty->tty_files) {
+                count++;
+        }
+        spin_unlock(&tty_files_lock);
+        if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+            tty->driver->subtype == PTY_TYPE_SLAVE &&
+            tty->link && tty->link->count)
+                count++;
+        if (tty->count != count) {
+                printk(KERN_WARNING "Warning: dev (%s) tty->count(%d) "
+                                    "!= #fd's(%d) in %s\n",
+                       tty->name, tty->count, count, routine);
+                return count;
+        }
+#endif
+        return 0;
+}
+
+/**
+ *      get_tty_driver          -       find device of a tty
+ *      @dev_t: device identifier
+ *      @index: returns the index of the tty
+ *
+ *      This routine returns a tty driver structure, given a device number
+ *      and also passes back the index number.
+ *
+ *      Locking: caller must hold tty_mutex
+ */
+
+static struct tty_driver *get_tty_driver(dev_t device, int *index)
+{
+        struct tty_driver *p;
+
+        list_for_each_entry(p, &tty_drivers, tty_drivers) {
+                dev_t base = MKDEV(p->major, p->minor_start);
+                if (device < base || device >= base + p->num)
+                        continue;
+                *index = device - base;
+                return tty_driver_kref_get(p);
+        }
+        return NULL;
+}
+
+#ifdef CONFIG_CONSOLE_POLL
+
+/**
+ *      tty_find_polling_driver -       find device of a polled tty
+ *      @name: name string to match
+ *      @line: pointer to resulting tty line nr
+ *
+ *      This routine returns a tty driver structure, given a name
+ *      and the condition that the tty driver is capable of polled
+ *      operation.
+ */
+struct tty_driver *tty_find_polling_driver(char *name, int *line)
+{
+        struct tty_driver *p, *res = NULL;
+        int tty_line = 0;
+        int len;
+        char *str, *stp;
+
+        for (str = name; *str; str++)
+                if ((*str >= '0' && *str <= '9') || *str == ',')
+                        break;
+        if (!*str)
+                return NULL;
+
+        len = str - name;
+        tty_line = simple_strtoul(str, &str, 10);
+
+        mutex_lock(&tty_mutex);
+        /* Search through the tty devices to look for a match */
+        list_for_each_entry(p, &tty_drivers, tty_drivers) {
+                if (strncmp(name, p->name, len) != 0)
+                        continue;
+                stp = str;
+                if (*stp == ',')
+                        stp++;
+                if (*stp == '\0')
+                        stp = NULL;
+
+                if (tty_line >= 0 && tty_line < p->num && p->ops &&
+                    p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
+                        res = tty_driver_kref_get(p);
+                        *line = tty_line;
+                        break;
+                }
+        }
+        mutex_unlock(&tty_mutex);
+
+        return res;
+}
+EXPORT_SYMBOL_GPL(tty_find_polling_driver);
+#endif
+
+/**
+ *      tty_check_change        -       check for POSIX terminal changes
+ *      @tty: tty to check
+ *
+ *      If we try to write to, or set the state of, a terminal and we're
+ *      not in the foreground, send a SIGTTOU.  If the signal is blocked or
+ *      ignored, go ahead and perform the operation.  (POSIX 7.2)
+ *
+ *      Locking: ctrl_lock
+ */
+
+int tty_check_change(struct tty_struct *tty)
+{
+        unsigned long flags;
+        int ret = 0;
+
+        if (current->signal->tty != tty)
+                return 0;
+
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+
+        if (!tty->pgrp) {
+                printk(KERN_WARNING "tty_check_change: tty->pgrp == NULL!\n");
+                goto out_unlock;
+        }
+        if (task_pgrp(current) == tty->pgrp)
+                goto out_unlock;
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+        if (is_ignored(SIGTTOU))
+                goto out;
+        if (is_current_pgrp_orphaned()) {
+                ret = -EIO;
+                goto out;
+        }
+        kill_pgrp(task_pgrp(current), SIGTTOU, 1);
+        set_thread_flag(TIF_SIGPENDING);
+        ret = -ERESTARTSYS;
+out:
+        return ret;
+out_unlock:
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+        return ret;
+}
+
+EXPORT_SYMBOL(tty_check_change);
+
+static ssize_t hung_up_tty_read(struct file *file, char __user *buf,
+                                size_t count, loff_t *ppos)
+{
+        return 0;
+}
+
+static ssize_t hung_up_tty_write(struct file *file, const char __user *buf,
+                                 size_t count, loff_t *ppos)
+{
+        return -EIO;
+}
+
+/* No kernel lock held - none needed ;) */
+static unsigned int hung_up_tty_poll(struct file *filp, poll_table *wait)
+{
+        return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
+}
+
+static long hung_up_tty_ioctl(struct file *file, unsigned int cmd,
+                unsigned long arg)
+{
+        return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
+}
+
+static long hung_up_tty_compat_ioctl(struct file *file,
+                                     unsigned int cmd, unsigned long arg)
+{
+        return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
+}
+
+static const struct file_operations tty_fops = {
+        .llseek         = no_llseek,
+        .read           = tty_read,
+        .write          = tty_write,
+        .poll           = tty_poll,
+        .unlocked_ioctl = tty_ioctl,
+        .compat_ioctl   = tty_compat_ioctl,
+        .open           = tty_open,
+        .release        = tty_release,
+        .fasync         = tty_fasync,
+};
+
+static const struct file_operations console_fops = {
+        .llseek         = no_llseek,
+        .read           = tty_read,
+        .write          = redirected_tty_write,
+        .poll           = tty_poll,
+        .unlocked_ioctl = tty_ioctl,
+        .compat_ioctl   = tty_compat_ioctl,
+        .open           = tty_open,
+        .release        = tty_release,
+        .fasync         = tty_fasync,
+};
+
+static const struct file_operations hung_up_tty_fops = {
+        .llseek         = no_llseek,
+        .read           = hung_up_tty_read,
+        .write          = hung_up_tty_write,
+        .poll           = hung_up_tty_poll,
+        .unlocked_ioctl = hung_up_tty_ioctl,
+        .compat_ioctl   = hung_up_tty_compat_ioctl,
+        .release        = tty_release,
+};
+
+static DEFINE_SPINLOCK(redirect_lock);
+static struct file *redirect;
+
+/**
+ *      tty_wakeup      -       request more data
+ *      @tty: terminal
+ *
+ *      Internal and external helper for wakeups of tty. This function
+ *      informs the line discipline if present that the driver is ready
+ *      to receive more output data.
+ */
+
+void tty_wakeup(struct tty_struct *tty)
+{
+        struct tty_ldisc *ld;
+
+        if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
+                ld = tty_ldisc_ref(tty);
+                if (ld) {
+                        if (ld->ops->write_wakeup)
+                                ld->ops->write_wakeup(tty);
+                        tty_ldisc_deref(ld);
+                }
+        }
+        wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
+}
+
+EXPORT_SYMBOL_GPL(tty_wakeup);
+
+/**
+ *      __tty_hangup            -       actual handler for hangup events
+ *      @work: tty device
+ *
+ *      This can be called by the "eventd" kernel thread.  That is process
+ *      synchronous but doesn't hold any locks, so we need to make sure we
+ *      have the appropriate locks for what we're doing.
+ *
+ *      The hangup event clears any pending redirections onto the hung up
+ *      device. It ensures future writes will error and it does the needed
+ *      line discipline hangup and signal delivery. The tty object itself
+ *      remains intact.
+ *
+ *      Locking:
+ *              BTM
+ *                redirect lock for undoing redirection
+ *                file list lock for manipulating list of ttys
+ *                tty_ldisc_lock from called functions
+ *                termios_mutex resetting termios data
+ *                tasklist_lock to walk task list for hangup event
+ *                  ->siglock to protect ->signal/->sighand
+ */
+void __tty_hangup(struct tty_struct *tty)
+{
+        struct file *cons_filp = NULL;
+        struct file *filp, *f = NULL;
+        struct task_struct *p;
+        struct tty_file_private *priv;
+        int    closecount = 0, n;
+        unsigned long flags;
+        int refs = 0;
+
+        if (!tty)
+                return;
+
+
+        spin_lock(&redirect_lock);
+        if (redirect && file_tty(redirect) == tty) {
+                f = redirect;
+                redirect = NULL;
+        }
+        spin_unlock(&redirect_lock);
+
+        tty_lock();
+
+        /* some functions below drop BTM, so we need this bit */
+        set_bit(TTY_HUPPING, &tty->flags);
+
+        /* inuse_filps is protected by the single tty lock,
+           this really needs to change if we want to flush the
+           workqueue with the lock held */
+        check_tty_count(tty, "tty_hangup");
+
+        spin_lock(&tty_files_lock);
+        /* This breaks for file handles being sent over AF_UNIX sockets ? */
+        list_for_each_entry(priv, &tty->tty_files, list) {
+                filp = priv->file;
+                if (filp->f_op->write == redirected_tty_write)
+                        cons_filp = filp;
+                if (filp->f_op->write != tty_write)
+                        continue;
+                closecount++;
+                __tty_fasync(-1, filp, 0);      /* can't block */
+                filp->f_op = &hung_up_tty_fops;
+        }
+        spin_unlock(&tty_files_lock);
+
+        /*
+         * it drops BTM and thus races with reopen
+         * we protect the race by TTY_HUPPING
+         */
+        tty_ldisc_hangup(tty);
+
+        read_lock(&tasklist_lock);
+        if (tty->session) {
+                do_each_pid_task(tty->session, PIDTYPE_SID, p) {
+                        spin_lock_irq(&p->sighand->siglock);
+                        if (p->signal->tty == tty) {
+                                p->signal->tty = NULL;
+                                /* We defer the dereferences outside fo
+                                   the tasklist lock */
+                                refs++;
+                        }
+                        if (!p->signal->leader) {
+                                spin_unlock_irq(&p->sighand->siglock);
+                                continue;
+                        }
+                        __group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
+                        __group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
+                        put_pid(p->signal->tty_old_pgrp);  /* A noop */
+                        spin_lock_irqsave(&tty->ctrl_lock, flags);
+                        if (tty->pgrp)
+                                p->signal->tty_old_pgrp = get_pid(tty->pgrp);
+                        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                        spin_unlock_irq(&p->sighand->siglock);
+                } while_each_pid_task(tty->session, PIDTYPE_SID, p);
+        }
+        read_unlock(&tasklist_lock);
+
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        clear_bit(TTY_THROTTLED, &tty->flags);
+        clear_bit(TTY_PUSH, &tty->flags);
+        clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+        put_pid(tty->session);
+        put_pid(tty->pgrp);
+        tty->session = NULL;
+        tty->pgrp = NULL;
+        tty->ctrl_status = 0;
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+
+        /* Account for the p->signal references we killed */
+        while (refs--)
+                tty_kref_put(tty);
+
+        /*
+         * If one of the devices matches a console pointer, we
+         * cannot just call hangup() because that will cause
+         * tty->count and state->count to go out of sync.
+         * So we just call close() the right number of times.
+         */
+        if (cons_filp) {
+                if (tty->ops->close)
+                        for (n = 0; n < closecount; n++)
+                                tty->ops->close(tty, cons_filp);
+        } else if (tty->ops->hangup)
+                (tty->ops->hangup)(tty);
+        /*
+         * We don't want to have driver/ldisc interactions beyond
+         * the ones we did here. The driver layer expects no
+         * calls after ->hangup() from the ldisc side. However we
+         * can't yet guarantee all that.
+         */
+        set_bit(TTY_HUPPED, &tty->flags);
+        clear_bit(TTY_HUPPING, &tty->flags);
+        tty_ldisc_enable(tty);
+
+        tty_unlock();
+
+        if (f)
+                fput(f);
+}
+
+static void do_tty_hangup(struct work_struct *work)
+{
+        struct tty_struct *tty =
+                container_of(work, struct tty_struct, hangup_work);
+
+        __tty_hangup(tty);
+}
+
+/**
+ *      tty_hangup              -       trigger a hangup event
+ *      @tty: tty to hangup
+ *
+ *      A carrier loss (virtual or otherwise) has occurred on this like
+ *      schedule a hangup sequence to run after this event.
+ */
+
+void tty_hangup(struct tty_struct *tty)
+{
+#ifdef TTY_DEBUG_HANGUP
+        char    buf[64];
+        printk(KERN_DEBUG "%s hangup...\n", tty_name(tty, buf));
+#endif
+        schedule_work(&tty->hangup_work);
+}
+
+EXPORT_SYMBOL(tty_hangup);
+
+/**
+ *      tty_vhangup             -       process vhangup
+ *      @tty: tty to hangup
+ *
+ *      The user has asked via system call for the terminal to be hung up.
+ *      We do this synchronously so that when the syscall returns the process
+ *      is complete. That guarantee is necessary for security reasons.
+ */
+
+void tty_vhangup(struct tty_struct *tty)
+{
+#ifdef TTY_DEBUG_HANGUP
+        char    buf[64];
+
+        printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
+#endif
+        __tty_hangup(tty);
+}
+
+EXPORT_SYMBOL(tty_vhangup);
+
+
+/**
+ *      tty_vhangup_self        -       process vhangup for own ctty
+ *
+ *      Perform a vhangup on the current controlling tty
+ */
+
+void tty_vhangup_self(void)
+{
+        struct tty_struct *tty;
+
+        tty = get_current_tty();
+        if (tty) {
+                tty_vhangup(tty);
+                tty_kref_put(tty);
+        }
+}
+
+/**
+ *      tty_hung_up_p           -       was tty hung up
+ *      @filp: file pointer of tty
+ *
+ *      Return true if the tty has been subject to a vhangup or a carrier
+ *      loss
+ */
+
+int tty_hung_up_p(struct file *filp)
+{
+        return (filp->f_op == &hung_up_tty_fops);
+}
+
+EXPORT_SYMBOL(tty_hung_up_p);
+
+static void session_clear_tty(struct pid *session)
+{
+        struct task_struct *p;
+        do_each_pid_task(session, PIDTYPE_SID, p) {
+                proc_clear_tty(p);
+        } while_each_pid_task(session, PIDTYPE_SID, p);
+}
+
+/**
+ *      disassociate_ctty       -       disconnect controlling tty
+ *      @on_exit: true if exiting so need to "hang up" the session
+ *
+ *      This function is typically called only by the session leader, when
+ *      it wants to disassociate itself from its controlling tty.
+ *
+ *      It performs the following functions:
+ *      (1)  Sends a SIGHUP and SIGCONT to the foreground process group
+ *      (2)  Clears the tty from being controlling the session
+ *      (3)  Clears the controlling tty for all processes in the
+ *              session group.
+ *
+ *      The argument on_exit is set to 1 if called when a process is
+ *      exiting; it is 0 if called by the ioctl TIOCNOTTY.
+ *
+ *      Locking:
+ *              BTM is taken for hysterical raisins, and held when
+ *                called from no_tty().
+ *                tty_mutex is taken to protect tty
+ *                ->siglock is taken to protect ->signal/->sighand
+ *                tasklist_lock is taken to walk process list for sessions
+ *                  ->siglock is taken to protect ->signal/->sighand
+ */
+
+void disassociate_ctty(int on_exit)
+{
+        struct tty_struct *tty;
+        struct pid *tty_pgrp = NULL;
+
+        if (!current->signal->leader)
+                return;
+
+        tty = get_current_tty();
+        if (tty) {
+                tty_pgrp = get_pid(tty->pgrp);
+                if (on_exit) {
+                        if (tty->driver->type != TTY_DRIVER_TYPE_PTY)
+                                tty_vhangup(tty);
+                }
+                tty_kref_put(tty);
+        } else if (on_exit) {
+                struct pid *old_pgrp;
+                spin_lock_irq(&current->sighand->siglock);
+                old_pgrp = current->signal->tty_old_pgrp;
+                current->signal->tty_old_pgrp = NULL;
+                spin_unlock_irq(&current->sighand->siglock);
+                if (old_pgrp) {
+                        kill_pgrp(old_pgrp, SIGHUP, on_exit);
+                        kill_pgrp(old_pgrp, SIGCONT, on_exit);
+                        put_pid(old_pgrp);
+                }
+                return;
+        }
+        if (tty_pgrp) {
+                kill_pgrp(tty_pgrp, SIGHUP, on_exit);
+                if (!on_exit)
+                        kill_pgrp(tty_pgrp, SIGCONT, on_exit);
+                put_pid(tty_pgrp);
+        }
+
+        spin_lock_irq(&current->sighand->siglock);
+        put_pid(current->signal->tty_old_pgrp);
+        current->signal->tty_old_pgrp = NULL;
+        spin_unlock_irq(&current->sighand->siglock);
+
+        tty = get_current_tty();
+        if (tty) {
+                unsigned long flags;
+                spin_lock_irqsave(&tty->ctrl_lock, flags);
+                put_pid(tty->session);
+                put_pid(tty->pgrp);
+                tty->session = NULL;
+                tty->pgrp = NULL;
+                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                tty_kref_put(tty);
+        } else {
+#ifdef TTY_DEBUG_HANGUP
+                printk(KERN_DEBUG "error attempted to write to tty [0x%p]"
+                       " = NULL", tty);
+#endif
+        }
+
+        /* Now clear signal->tty under the lock */
+        read_lock(&tasklist_lock);
+        session_clear_tty(task_session(current));
+        read_unlock(&tasklist_lock);
+}
+
+/**
+ *
+ *      no_tty  - Ensure the current process does not have a controlling tty
+ */
+void no_tty(void)
+{
+        struct task_struct *tsk = current;
+        tty_lock();
+        disassociate_ctty(0);
+        tty_unlock();
+        proc_clear_tty(tsk);
+}
+
+
+/**
+ *      stop_tty        -       propagate flow control
+ *      @tty: tty to stop
+ *
+ *      Perform flow control to the driver. For PTY/TTY pairs we
+ *      must also propagate the TIOCKPKT status. May be called
+ *      on an already stopped device and will not re-call the driver
+ *      method.
+ *
+ *      This functionality is used by both the line disciplines for
+ *      halting incoming flow and by the driver. It may therefore be
+ *      called from any context, may be under the tty atomic_write_lock
+ *      but not always.
+ *
+ *      Locking:
+ *              Uses the tty control lock internally
+ */
+
+void stop_tty(struct tty_struct *tty)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        if (tty->stopped) {
+                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                return;
+        }
+        tty->stopped = 1;
+        if (tty->link && tty->link->packet) {
+                tty->ctrl_status &= ~TIOCPKT_START;
+                tty->ctrl_status |= TIOCPKT_STOP;
+                wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
+        }
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+        if (tty->ops->stop)
+                (tty->ops->stop)(tty);
+}
+
+EXPORT_SYMBOL(stop_tty);
+
+/**
+ *      start_tty       -       propagate flow control
+ *      @tty: tty to start
+ *
+ *      Start a tty that has been stopped if at all possible. Perform
+ *      any necessary wakeups and propagate the TIOCPKT status. If this
+ *      is the tty was previous stopped and is being started then the
+ *      driver start method is invoked and the line discipline woken.
+ *
+ *      Locking:
+ *              ctrl_lock
+ */
+
+void start_tty(struct tty_struct *tty)
+{
+        unsigned long flags;
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        if (!tty->stopped || tty->flow_stopped) {
+                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                return;
+        }
+        tty->stopped = 0;
+        if (tty->link && tty->link->packet) {
+                tty->ctrl_status &= ~TIOCPKT_STOP;
+                tty->ctrl_status |= TIOCPKT_START;
+                wake_up_interruptible_poll(&tty->link->read_wait, POLLIN);
+        }
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+        if (tty->ops->start)
+                (tty->ops->start)(tty);
+        /* If we have a running line discipline it may need kicking */
+        tty_wakeup(tty);
+}
+
+EXPORT_SYMBOL(start_tty);
+
+/**
+ *      tty_read        -       read method for tty device files
+ *      @file: pointer to tty file
+ *      @buf: user buffer
+ *      @count: size of user buffer
+ *      @ppos: unused
+ *
+ *      Perform the read system call function on this terminal device. Checks
+ *      for hung up devices before calling the line discipline method.
+ *
+ *      Locking:
+ *              Locks the line discipline internally while needed. Multiple
+ *      read calls may be outstanding in parallel.
+ */
+
+static ssize_t tty_read(struct file *file, char __user *buf, size_t count,
+                        loff_t *ppos)
+{
+        int i;
+        struct inode *inode = file->f_path.dentry->d_inode;
+        struct tty_struct *tty = file_tty(file);
+        struct tty_ldisc *ld;
+
+        if (tty_paranoia_check(tty, inode, "tty_read"))
+                return -EIO;
+        if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
+                return -EIO;
+
+        /* We want to wait for the line discipline to sort out in this
+           situation */
+        ld = tty_ldisc_ref_wait(tty);
+        if (ld->ops->read)
+                i = (ld->ops->read)(tty, file, buf, count);
+        else
+                i = -EIO;
+        tty_ldisc_deref(ld);
+        if (i > 0)
+                inode->i_atime = current_fs_time(inode->i_sb);
+        return i;
+}
+
+void tty_write_unlock(struct tty_struct *tty)
+        __releases(&tty->atomic_write_lock)
+{
+        mutex_unlock(&tty->atomic_write_lock);
+        wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
+}
+
+int tty_write_lock(struct tty_struct *tty, int ndelay)
+        __acquires(&tty->atomic_write_lock)
+{
+        if (!mutex_trylock(&tty->atomic_write_lock)) {
+                if (ndelay)
+                        return -EAGAIN;
+                if (mutex_lock_interruptible(&tty->atomic_write_lock))
+                        return -ERESTARTSYS;
+        }
+        return 0;
+}
+
+/*
+ * Split writes up in sane blocksizes to avoid
+ * denial-of-service type attacks
+ */
+static inline ssize_t do_tty_write(
+        ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
+        struct tty_struct *tty,
+        struct file *file,
+        const char __user *buf,
+        size_t count)
+{
+        ssize_t ret, written = 0;
+        unsigned int chunk;
+
+        ret = tty_write_lock(tty, file->f_flags & O_NDELAY);
+        if (ret < 0)
+                return ret;
+
+        /*
+         * We chunk up writes into a temporary buffer. This
+         * simplifies low-level drivers immensely, since they
+         * don't have locking issues and user mode accesses.
+         *
+         * But if TTY_NO_WRITE_SPLIT is set, we should use a
+         * big chunk-size..
+         *
+         * The default chunk-size is 2kB, because the NTTY
+         * layer has problems with bigger chunks. It will
+         * claim to be able to handle more characters than
+         * it actually does.
+         *
+         * FIXME: This can probably go away now except that 64K chunks
+         * are too likely to fail unless switched to vmalloc...
+         */
+        chunk = 2048;
+        if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
+                chunk = 65536;
+        if (count < chunk)
+                chunk = count;
+
+        /* write_buf/write_cnt is protected by the atomic_write_lock mutex */
+        if (tty->write_cnt < chunk) {
+                unsigned char *buf_chunk;
+
+                if (chunk < 1024)
+                        chunk = 1024;
+
+                buf_chunk = kmalloc(chunk, GFP_KERNEL);
+                if (!buf_chunk) {
+                        ret = -ENOMEM;
+                        goto out;
+                }
+                kfree(tty->write_buf);
+                tty->write_cnt = chunk;
+                tty->write_buf = buf_chunk;
+        }
+
+        /* Do the write .. */
+        for (;;) {
+                size_t size = count;
+                if (size > chunk)
+                        size = chunk;
+                ret = -EFAULT;
+                if (copy_from_user(tty->write_buf, buf, size))
+                        break;
+                ret = write(tty, file, tty->write_buf, size);
+                if (ret <= 0)
+                        break;
+                written += ret;
+                buf += ret;
+                count -= ret;
+                if (!count)
+                        break;
+                ret = -ERESTARTSYS;
+                if (signal_pending(current))
+                        break;
+                cond_resched();
+        }
+        if (written) {
+                struct inode *inode = file->f_path.dentry->d_inode;
+                inode->i_mtime = current_fs_time(inode->i_sb);
+                ret = written;
+        }
+out:
+        tty_write_unlock(tty);
+        return ret;
+}
+
+/**
+ * tty_write_message - write a message to a certain tty, not just the console.
+ * @tty: the destination tty_struct
+ * @msg: the message to write
+ *
+ * This is used for messages that need to be redirected to a specific tty.
+ * We don't put it into the syslog queue right now maybe in the future if
+ * really needed.
+ *
+ * We must still hold the BTM and test the CLOSING flag for the moment.
+ */
+
+void tty_write_message(struct tty_struct *tty, char *msg)
+{
+        if (tty) {
+                mutex_lock(&tty->atomic_write_lock);
+                tty_lock();
+                if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
+                        tty_unlock();
+                        tty->ops->write(tty, msg, strlen(msg));
+                } else
+                        tty_unlock();
+                tty_write_unlock(tty);
+        }
+        return;
+}
+
+
+/**
+ *      tty_write               -       write method for tty device file
+ *      @file: tty file pointer
+ *      @buf: user data to write
+ *      @count: bytes to write
+ *      @ppos: unused
+ *
+ *      Write data to a tty device via the line discipline.
+ *
+ *      Locking:
+ *              Locks the line discipline as required
+ *              Writes to the tty driver are serialized by the atomic_write_lock
+ *      and are then processed in chunks to the device. The line discipline
+ *      write method will not be invoked in parallel for each device.
+ */
+
+static ssize_t tty_write(struct file *file, const char __user *buf,
+                                                size_t count, loff_t *ppos)
+{
+        struct inode *inode = file->f_path.dentry->d_inode;
+        struct tty_struct *tty = file_tty(file);
+        struct tty_ldisc *ld;
+        ssize_t ret;
+
+        if (tty_paranoia_check(tty, inode, "tty_write"))
+                return -EIO;
+        if (!tty || !tty->ops->write ||
+                (test_bit(TTY_IO_ERROR, &tty->flags)))
+                        return -EIO;
+        /* Short term debug to catch buggy drivers */
+        if (tty->ops->write_room == NULL)
+                printk(KERN_ERR "tty driver %s lacks a write_room method.\n",
+                        tty->driver->name);
+        ld = tty_ldisc_ref_wait(tty);
+        if (!ld->ops->write)
+                ret = -EIO;
+        else
+                ret = do_tty_write(ld->ops->write, tty, file, buf, count);
+        tty_ldisc_deref(ld);
+        return ret;
+}
+
+ssize_t redirected_tty_write(struct file *file, const char __user *buf,
+                                                size_t count, loff_t *ppos)
+{
+        struct file *p = NULL;
+
+        spin_lock(&redirect_lock);
+        if (redirect) {
+                get_file(redirect);
+                p = redirect;
+        }
+        spin_unlock(&redirect_lock);
+
+        if (p) {
+                ssize_t res;
+                res = vfs_write(p, buf, count, &p->f_pos);
+                fput(p);
+                return res;
+        }
+        return tty_write(file, buf, count, ppos);
+}
+
+static char ptychar[] = "pqrstuvwxyzabcde";
+
+/**
+ *      pty_line_name   -       generate name for a pty
+ *      @driver: the tty driver in use
+ *      @index: the minor number
+ *      @p: output buffer of at least 6 bytes
+ *
+ *      Generate a name from a driver reference and write it to the output
+ *      buffer.
+ *
+ *      Locking: None
+ */
+static void pty_line_name(struct tty_driver *driver, int index, char *p)
+{
+        int i = index + driver->name_base;
+        /* ->name is initialized to "ttyp", but "tty" is expected */
+        sprintf(p, "%s%c%x",
+                driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
+                ptychar[i >> 4 & 0xf], i & 0xf);
+}
+
+/**
+ *      tty_line_name   -       generate name for a tty
+ *      @driver: the tty driver in use
+ *      @index: the minor number
+ *      @p: output buffer of at least 7 bytes
+ *
+ *      Generate a name from a driver reference and write it to the output
+ *      buffer.
+ *
+ *      Locking: None
+ */
+static void tty_line_name(struct tty_driver *driver, int index, char *p)
+{
+        sprintf(p, "%s%d", driver->name, index + driver->name_base);
+}
+
+/**
+ *      tty_driver_lookup_tty() - find an existing tty, if any
+ *      @driver: the driver for the tty
+ *      @idx:    the minor number
+ *
+ *      Return the tty, if found or ERR_PTR() otherwise.
+ *
+ *      Locking: tty_mutex must be held. If tty is found, the mutex must
+ *      be held until the 'fast-open' is also done. Will change once we
+ *      have refcounting in the driver and per driver locking
+ */
+static struct tty_struct *tty_driver_lookup_tty(struct tty_driver *driver,
+                struct inode *inode, int idx)
+{
+        struct tty_struct *tty;
+
+        if (driver->ops->lookup)
+                return driver->ops->lookup(driver, inode, idx);
+
+        tty = driver->ttys[idx];
+        return tty;
+}
+
+/**
+ *      tty_init_termios        -  helper for termios setup
+ *      @tty: the tty to set up
+ *
+ *      Initialise the termios structures for this tty. Thus runs under
+ *      the tty_mutex currently so we can be relaxed about ordering.
+ */
+
+int tty_init_termios(struct tty_struct *tty)
+{
+        struct ktermios *tp;
+        int idx = tty->index;
+
+        tp = tty->driver->termios[idx];
+        if (tp == NULL) {
+                tp = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
+                if (tp == NULL)
+                        return -ENOMEM;
+                memcpy(tp, &tty->driver->init_termios,
+                                                sizeof(struct ktermios));
+                tty->driver->termios[idx] = tp;
+        }
+        tty->termios = tp;
+        tty->termios_locked = tp + 1;
+
+        /* Compatibility until drivers always set this */
+        tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
+        tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
+        return 0;
+}
+EXPORT_SYMBOL_GPL(tty_init_termios);
+
+/**
+ *      tty_driver_install_tty() - install a tty entry in the driver
+ *      @driver: the driver for the tty
+ *      @tty: the tty
+ *
+ *      Install a tty object into the driver tables. The tty->index field
+ *      will be set by the time this is called. This method is responsible
+ *      for ensuring any need additional structures are allocated and
+ *      configured.
+ *
+ *      Locking: tty_mutex for now
+ */
+static int tty_driver_install_tty(struct tty_driver *driver,
+                                                struct tty_struct *tty)
+{
+        int idx = tty->index;
+        int ret;
+
+        if (driver->ops->install) {
+                ret = driver->ops->install(driver, tty);
+                return ret;
+        }
+
+        if (tty_init_termios(tty) == 0) {
+                tty_driver_kref_get(driver);
+                tty->count++;
+                driver->ttys[idx] = tty;
+                return 0;
+        }
+        return -ENOMEM;
+}
+
+/**
+ *      tty_driver_remove_tty() - remove a tty from the driver tables
+ *      @driver: the driver for the tty
+ *      @idx:    the minor number
+ *
+ *      Remvoe a tty object from the driver tables. The tty->index field
+ *      will be set by the time this is called.
+ *
+ *      Locking: tty_mutex for now
+ */
+static void tty_driver_remove_tty(struct tty_driver *driver,
+                                                struct tty_struct *tty)
+{
+        if (driver->ops->remove)
+                driver->ops->remove(driver, tty);
+        else
+                driver->ttys[tty->index] = NULL;
+}
+
+/*
+ *      tty_reopen()    - fast re-open of an open tty
+ *      @tty    - the tty to open
+ *
+ *      Return 0 on success, -errno on error.
+ *
+ *      Locking: tty_mutex must be held from the time the tty was found
+ *               till this open completes.
+ */
+static int tty_reopen(struct tty_struct *tty)
+{
+        struct tty_driver *driver = tty->driver;
+
+        if (test_bit(TTY_CLOSING, &tty->flags) ||
+                        test_bit(TTY_HUPPING, &tty->flags) ||
+                        test_bit(TTY_LDISC_CHANGING, &tty->flags))
+                return -EIO;
+
+        if (driver->type == TTY_DRIVER_TYPE_PTY &&
+            driver->subtype == PTY_TYPE_MASTER) {
+                /*
+                 * special case for PTY masters: only one open permitted,
+                 * and the slave side open count is incremented as well.
+                 */
+                if (tty->count)
+                        return -EIO;
+
+                tty->link->count++;
+        }
+        tty->count++;
+        tty->driver = driver; /* N.B. why do this every time?? */
+
+        mutex_lock(&tty->ldisc_mutex);
+        WARN_ON(!test_bit(TTY_LDISC, &tty->flags));
+        mutex_unlock(&tty->ldisc_mutex);
+
+        return 0;
+}
+
+/**
+ *      tty_init_dev            -       initialise a tty device
+ *      @driver: tty driver we are opening a device on
+ *      @idx: device index
+ *      @ret_tty: returned tty structure
+ *      @first_ok: ok to open a new device (used by ptmx)
+ *
+ *      Prepare a tty device. This may not be a "new" clean device but
+ *      could also be an active device. The pty drivers require special
+ *      handling because of this.
+ *
+ *      Locking:
+ *              The function is called under the tty_mutex, which
+ *      protects us from the tty struct or driver itself going away.
+ *
+ *      On exit the tty device has the line discipline attached and
+ *      a reference count of 1. If a pair was created for pty/tty use
+ *      and the other was a pty master then it too has a reference count of 1.
+ *
+ * WSH 06/09/97: Rewritten to remove races and properly clean up after a
+ * failed open.  The new code protects the open with a mutex, so it's
+ * really quite straightforward.  The mutex locking can probably be
+ * relaxed for the (most common) case of reopening a tty.
+ */
+
+struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
+                                                                int first_ok)
+{
+        struct tty_struct *tty;
+        int retval;
+
+        /* Check if pty master is being opened multiple times */
+        if (driver->subtype == PTY_TYPE_MASTER &&
+                (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
+                return ERR_PTR(-EIO);
+        }
+
+        /*
+         * First time open is complex, especially for PTY devices.
+         * This code guarantees that either everything succeeds and the
+         * TTY is ready for operation, or else the table slots are vacated
+         * and the allocated memory released.  (Except that the termios
+         * and locked termios may be retained.)
+         */
+
+        if (!try_module_get(driver->owner))
+                return ERR_PTR(-ENODEV);
+
+        tty = alloc_tty_struct();
+        if (!tty) {
+                retval = -ENOMEM;
+                goto err_module_put;
+        }
+        initialize_tty_struct(tty, driver, idx);
+
+        retval = tty_driver_install_tty(driver, tty);
+        if (retval < 0)
+                goto err_deinit_tty;
+
+        /*
+         * Structures all installed ... call the ldisc open routines.
+         * If we fail here just call release_tty to clean up.  No need
+         * to decrement the use counts, as release_tty doesn't care.
+         */
+        retval = tty_ldisc_setup(tty, tty->link);
+        if (retval)
+                goto err_release_tty;
+        return tty;
+
+err_deinit_tty:
+        deinitialize_tty_struct(tty);
+        free_tty_struct(tty);
+err_module_put:
+        module_put(driver->owner);
+        return ERR_PTR(retval);
+
+        /* call the tty release_tty routine to clean out this slot */
+err_release_tty:
+        if (printk_ratelimit())
+                printk(KERN_INFO "tty_init_dev: ldisc open failed, "
+                                 "clearing slot %d\n", idx);
+        release_tty(tty, idx);
+        return ERR_PTR(retval);
+}
+
+void tty_free_termios(struct tty_struct *tty)
+{
+        struct ktermios *tp;
+        int idx = tty->index;
+        /* Kill this flag and push into drivers for locking etc */
+        if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
+                /* FIXME: Locking on ->termios array */
+                tp = tty->termios;
+                tty->driver->termios[idx] = NULL;
+                kfree(tp);
+        }
+}
+EXPORT_SYMBOL(tty_free_termios);
+
+void tty_shutdown(struct tty_struct *tty)
+{
+        tty_driver_remove_tty(tty->driver, tty);
+        tty_free_termios(tty);
+}
+EXPORT_SYMBOL(tty_shutdown);
+
+/**
+ *      release_one_tty         -       release tty structure memory
+ *      @kref: kref of tty we are obliterating
+ *
+ *      Releases memory associated with a tty structure, and clears out the
+ *      driver table slots. This function is called when a device is no longer
+ *      in use. It also gets called when setup of a device fails.
+ *
+ *      Locking:
+ *              tty_mutex - sometimes only
+ *              takes the file list lock internally when working on the list
+ *      of ttys that the driver keeps.
+ *
+ *      This method gets called from a work queue so that the driver private
+ *      cleanup ops can sleep (needed for USB at least)
+ */
+static void release_one_tty(struct work_struct *work)
+{
+        struct tty_struct *tty =
+                container_of(work, struct tty_struct, hangup_work);
+        struct tty_driver *driver = tty->driver;
+
+        if (tty->ops->cleanup)
+                tty->ops->cleanup(tty);
+
+        tty->magic = 0;
+        tty_driver_kref_put(driver);
+        module_put(driver->owner);
+
+        spin_lock(&tty_files_lock);
+        list_del_init(&tty->tty_files);
+        spin_unlock(&tty_files_lock);
+
+        put_pid(tty->pgrp);
+        put_pid(tty->session);
+        free_tty_struct(tty);
+}
+
+static void queue_release_one_tty(struct kref *kref)
+{
+        struct tty_struct *tty = container_of(kref, struct tty_struct, kref);
+
+        if (tty->ops->shutdown)
+                tty->ops->shutdown(tty);
+        else
+                tty_shutdown(tty);
+
+        /* The hangup queue is now free so we can reuse it rather than
+           waste a chunk of memory for each port */
+        INIT_WORK(&tty->hangup_work, release_one_tty);
+        schedule_work(&tty->hangup_work);
+}
+
+/**
+ *      tty_kref_put            -       release a tty kref
+ *      @tty: tty device
+ *
+ *      Release a reference to a tty device and if need be let the kref
+ *      layer destruct the object for us
+ */
+
+void tty_kref_put(struct tty_struct *tty)
+{
+        if (tty)
+                kref_put(&tty->kref, queue_release_one_tty);
+}
+EXPORT_SYMBOL(tty_kref_put);
+
+/**
+ *      release_tty             -       release tty structure memory
+ *
+ *      Release both @tty and a possible linked partner (think pty pair),
+ *      and decrement the refcount of the backing module.
+ *
+ *      Locking:
+ *              tty_mutex - sometimes only
+ *              takes the file list lock internally when working on the list
+ *      of ttys that the driver keeps.
+ *              FIXME: should we require tty_mutex is held here ??
+ *
+ */
+static void release_tty(struct tty_struct *tty, int idx)
+{
+        /* This should always be true but check for the moment */
+        WARN_ON(tty->index != idx);
+
+        if (tty->link)
+                tty_kref_put(tty->link);
+        tty_kref_put(tty);
+}
+
+/**
+ *      tty_release             -       vfs callback for close
+ *      @inode: inode of tty
+ *      @filp: file pointer for handle to tty
+ *
+ *      Called the last time each file handle is closed that references
+ *      this tty. There may however be several such references.
+ *
+ *      Locking:
+ *              Takes bkl. See tty_release_dev
+ *
+ * Even releasing the tty structures is a tricky business.. We have
+ * to be very careful that the structures are all released at the
+ * same time, as interrupts might otherwise get the wrong pointers.
+ *
+ * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
+ * lead to double frees or releasing memory still in use.
+ */
+
+int tty_release(struct inode *inode, struct file *filp)
+{
+        struct tty_struct *tty = file_tty(filp);
+        struct tty_struct *o_tty;
+        int     pty_master, tty_closing, o_tty_closing, do_sleep;
+        int     devpts;
+        int     idx;
+        char    buf[64];
+
+        if (tty_paranoia_check(tty, inode, "tty_release_dev"))
+                return 0;
+
+        tty_lock();
+        check_tty_count(tty, "tty_release_dev");
+
+        __tty_fasync(-1, filp, 0);
+
+        idx = tty->index;
+        pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+                      tty->driver->subtype == PTY_TYPE_MASTER);
+        devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
+        o_tty = tty->link;
+
+#ifdef TTY_PARANOIA_CHECK
+        if (idx < 0 || idx >= tty->driver->num) {
+                printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
+                                  "free (%s)\n", tty->name);
+                tty_unlock();
+                return 0;
+        }
+        if (!devpts) {
+                if (tty != tty->driver->ttys[idx]) {
+                        tty_unlock();
+                        printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
+                               "for (%s)\n", idx, tty->name);
+                        return 0;
+                }
+                if (tty->termios != tty->driver->termios[idx]) {
+                        tty_unlock();
+                        printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
+                               "for (%s)\n",
+                               idx, tty->name);
+                        return 0;
+                }
+        }
+#endif
+
+#ifdef TTY_DEBUG_HANGUP
+        printk(KERN_DEBUG "tty_release_dev of %s (tty count=%d)...",
+               tty_name(tty, buf), tty->count);
+#endif
+
+#ifdef TTY_PARANOIA_CHECK
+        if (tty->driver->other &&
+             !(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
+                if (o_tty != tty->driver->other->ttys[idx]) {
+                        tty_unlock();
+                        printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
+                                          "not o_tty for (%s)\n",
+                               idx, tty->name);
+                        return 0 ;
+                }
+                if (o_tty->termios != tty->driver->other->termios[idx]) {
+                        tty_unlock();
+                        printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
+                                          "not o_termios for (%s)\n",
+                               idx, tty->name);
+                        return 0;
+                }
+                if (o_tty->link != tty) {
+                        tty_unlock();
+                        printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
+                        return 0;
+                }
+        }
+#endif
+        if (tty->ops->close)
+                tty->ops->close(tty, filp);
+
+        tty_unlock();
+        /*
+         * Sanity check: if tty->count is going to zero, there shouldn't be
+         * any waiters on tty->read_wait or tty->write_wait.  We test the
+         * wait queues and kick everyone out _before_ actually starting to
+         * close.  This ensures that we won't block while releasing the tty
+         * structure.
+         *
+         * The test for the o_tty closing is necessary, since the master and
+         * slave sides may close in any order.  If the slave side closes out
+         * first, its count will be one, since the master side holds an open.
+         * Thus this test wouldn't be triggered at the time the slave closes,
+         * so we do it now.
+         *
+         * Note that it's possible for the tty to be opened again while we're
+         * flushing out waiters.  By recalculating the closing flags before
+         * each iteration we avoid any problems.
+         */
+        while (1) {
+                /* Guard against races with tty->count changes elsewhere and
+                   opens on /dev/tty */
+
+                mutex_lock(&tty_mutex);
+                tty_lock();
+                tty_closing = tty->count <= 1;
+                o_tty_closing = o_tty &&
+                        (o_tty->count <= (pty_master ? 1 : 0));
+                do_sleep = 0;
+
+                if (tty_closing) {
+                        if (waitqueue_active(&tty->read_wait)) {
+                                wake_up_poll(&tty->read_wait, POLLIN);
+                                do_sleep++;
+                        }
+                        if (waitqueue_active(&tty->write_wait)) {
+                                wake_up_poll(&tty->write_wait, POLLOUT);
+                                do_sleep++;
+                        }
+                }
+                if (o_tty_closing) {
+                        if (waitqueue_active(&o_tty->read_wait)) {
+                                wake_up_poll(&o_tty->read_wait, POLLIN);
+                                do_sleep++;
+                        }
+                        if (waitqueue_active(&o_tty->write_wait)) {
+                                wake_up_poll(&o_tty->write_wait, POLLOUT);
+                                do_sleep++;
+                        }
+                }
+                if (!do_sleep)
+                        break;
+
+                printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue "
+                                    "active!\n", tty_name(tty, buf));
+                tty_unlock();
+                mutex_unlock(&tty_mutex);
+                schedule();
+        }
+
+        /*
+         * The closing flags are now consistent with the open counts on
+         * both sides, and we've completed the last operation that could
+         * block, so it's safe to proceed with closing.
+         */
+        if (pty_master) {
+                if (--o_tty->count < 0) {
+                        printk(KERN_WARNING "tty_release_dev: bad pty slave count "
+                                            "(%d) for %s\n",
+                               o_tty->count, tty_name(o_tty, buf));
+                        o_tty->count = 0;
+                }
+        }
+        if (--tty->count < 0) {
+                printk(KERN_WARNING "tty_release_dev: bad tty->count (%d) for %s\n",
+                       tty->count, tty_name(tty, buf));
+                tty->count = 0;
+        }
+
+        /*
+         * We've decremented tty->count, so we need to remove this file
+         * descriptor off the tty->tty_files list; this serves two
+         * purposes:
+         *  - check_tty_count sees the correct number of file descriptors
+         *    associated with this tty.
+         *  - do_tty_hangup no longer sees this file descriptor as
+         *    something that needs to be handled for hangups.
+         */
+        tty_del_file(filp);
+
+        /*
+         * Perform some housekeeping before deciding whether to return.
+         *
+         * Set the TTY_CLOSING flag if this was the last open.  In the
+         * case of a pty we may have to wait around for the other side
+         * to close, and TTY_CLOSING makes sure we can't be reopened.
+         */
+        if (tty_closing)
+                set_bit(TTY_CLOSING, &tty->flags);
+        if (o_tty_closing)
+                set_bit(TTY_CLOSING, &o_tty->flags);
+
+        /*
+         * If _either_ side is closing, make sure there aren't any
+         * processes that still think tty or o_tty is their controlling
+         * tty.
+         */
+        if (tty_closing || o_tty_closing) {
+                read_lock(&tasklist_lock);
+                session_clear_tty(tty->session);
+                if (o_tty)
+                        session_clear_tty(o_tty->session);
+                read_unlock(&tasklist_lock);
+        }
+
+        mutex_unlock(&tty_mutex);
+
+        /* check whether both sides are closing ... */
+        if (!tty_closing || (o_tty && !o_tty_closing)) {
+                tty_unlock();
+                return 0;
+        }
+
+#ifdef TTY_DEBUG_HANGUP
+        printk(KERN_DEBUG "freeing tty structure...");
+#endif
+        /*
+         * Ask the line discipline code to release its structures
+         */
+        tty_ldisc_release(tty, o_tty);
+        /*
+         * The release_tty function takes care of the details of clearing
+         * the slots and preserving the termios structure.
+         */
+        release_tty(tty, idx);
+
+        /* Make this pty number available for reallocation */
+        if (devpts)
+                devpts_kill_index(inode, idx);
+        tty_unlock();
+        return 0;
+}
+
+/**
+ *      tty_open                -       open a tty device
+ *      @inode: inode of device file
+ *      @filp: file pointer to tty
+ *
+ *      tty_open and tty_release keep up the tty count that contains the
+ *      number of opens done on a tty. We cannot use the inode-count, as
+ *      different inodes might point to the same tty.
+ *
+ *      Open-counting is needed for pty masters, as well as for keeping
+ *      track of serial lines: DTR is dropped when the last close happens.
+ *      (This is not done solely through tty->count, now.  - Ted 1/27/92)
+ *
+ *      The termios state of a pty is reset on first open so that
+ *      settings don't persist across reuse.
+ *
+ *      Locking: tty_mutex protects tty, get_tty_driver and tty_init_dev work.
+ *               tty->count should protect the rest.
+ *               ->siglock protects ->signal/->sighand
+ */
+
+static int tty_open(struct inode *inode, struct file *filp)
+{
+        struct tty_struct *tty = NULL;
+        int noctty, retval;
+        struct tty_driver *driver;
+        int index;
+        dev_t device = inode->i_rdev;
+        unsigned saved_flags = filp->f_flags;
+
+        nonseekable_open(inode, filp);
+
+retry_open:
+        noctty = filp->f_flags & O_NOCTTY;
+        index  = -1;
+        retval = 0;
+
+        mutex_lock(&tty_mutex);
+        tty_lock();
+
+        if (device == MKDEV(TTYAUX_MAJOR, 0)) {
+                tty = get_current_tty();
+                if (!tty) {
+                        tty_unlock();
+                        mutex_unlock(&tty_mutex);
+                        return -ENXIO;
+                }
+                driver = tty_driver_kref_get(tty->driver);
+                index = tty->index;
+                filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
+                /* noctty = 1; */
+                /* FIXME: Should we take a driver reference ? */
+                tty_kref_put(tty);
+                goto got_driver;
+        }
+#ifdef CONFIG_VT
+        if (device == MKDEV(TTY_MAJOR, 0)) {
+                extern struct tty_driver *console_driver;
+                driver = tty_driver_kref_get(console_driver);
+                index = fg_console;
+                noctty = 1;
+                goto got_driver;
+        }
+#endif
+        if (device == MKDEV(TTYAUX_MAJOR, 1)) {
+                struct tty_driver *console_driver = console_device(&index);
+                if (console_driver) {
+                        driver = tty_driver_kref_get(console_driver);
+                        if (driver) {
+                                /* Don't let /dev/console block */
+                                filp->f_flags |= O_NONBLOCK;
+                                noctty = 1;
+                                goto got_driver;
+                        }
+                }
+                tty_unlock();
+                mutex_unlock(&tty_mutex);
+                return -ENODEV;
+        }
+
+        driver = get_tty_driver(device, &index);
+        if (!driver) {
+                tty_unlock();
+                mutex_unlock(&tty_mutex);
+                return -ENODEV;
+        }
+got_driver:
+        if (!tty) {
+                /* check whether we're reopening an existing tty */
+                tty = tty_driver_lookup_tty(driver, inode, index);
+
+                if (IS_ERR(tty)) {
+                        tty_unlock();
+                        mutex_unlock(&tty_mutex);
+                        return PTR_ERR(tty);
+                }
+        }
+
+        if (tty) {
+                retval = tty_reopen(tty);
+                if (retval)
+                        tty = ERR_PTR(retval);
+        } else
+                tty = tty_init_dev(driver, index, 0);
+
+        mutex_unlock(&tty_mutex);
+        tty_driver_kref_put(driver);
+        if (IS_ERR(tty)) {
+                tty_unlock();
+                return PTR_ERR(tty);
+        }
+
+        retval = tty_add_file(tty, filp);
+        if (retval) {
+                tty_unlock();
+                tty_release(inode, filp);
+                return retval;
+        }
+
+        check_tty_count(tty, "tty_open");
+        if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+            tty->driver->subtype == PTY_TYPE_MASTER)
+                noctty = 1;
+#ifdef TTY_DEBUG_HANGUP
+        printk(KERN_DEBUG "opening %s...", tty->name);
+#endif
+        if (tty->ops->open)
+                retval = tty->ops->open(tty, filp);
+        else
+                retval = -ENODEV;
+        filp->f_flags = saved_flags;
+
+        if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) &&
+                                                !capable(CAP_SYS_ADMIN))
+                retval = -EBUSY;
+
+        if (retval) {
+#ifdef TTY_DEBUG_HANGUP
+                printk(KERN_DEBUG "error %d in opening %s...", retval,
+                       tty->name);
+#endif
+                tty_unlock(); /* need to call tty_release without BTM */
+                tty_release(inode, filp);
+                if (retval != -ERESTARTSYS)
+                        return retval;
+
+                if (signal_pending(current))
+                        return retval;
+
+                schedule();
+                /*
+                 * Need to reset f_op in case a hangup happened.
+                 */
+                tty_lock();
+                if (filp->f_op == &hung_up_tty_fops)
+                        filp->f_op = &tty_fops;
+                tty_unlock();
+                goto retry_open;
+        }
+        tty_unlock();
+
+
+        mutex_lock(&tty_mutex);
+        tty_lock();
+        spin_lock_irq(&current->sighand->siglock);
+        if (!noctty &&
+            current->signal->leader &&
+            !current->signal->tty &&
+            tty->session == NULL)
+                __proc_set_tty(current, tty);
+        spin_unlock_irq(&current->sighand->siglock);
+        tty_unlock();
+        mutex_unlock(&tty_mutex);
+        return 0;
+}
+
+
+
+/**
+ *      tty_poll        -       check tty status
+ *      @filp: file being polled
+ *      @wait: poll wait structures to update
+ *
+ *      Call the line discipline polling method to obtain the poll
+ *      status of the device.
+ *
+ *      Locking: locks called line discipline but ldisc poll method
+ *      may be re-entered freely by other callers.
+ */
+
+static unsigned int tty_poll(struct file *filp, poll_table *wait)
+{
+        struct tty_struct *tty = file_tty(filp);
+        struct tty_ldisc *ld;
+        int ret = 0;
+
+        if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_poll"))
+                return 0;
+
+        ld = tty_ldisc_ref_wait(tty);
+        if (ld->ops->poll)
+                ret = (ld->ops->poll)(tty, filp, wait);
+        tty_ldisc_deref(ld);
+        return ret;
+}
+
+static int __tty_fasync(int fd, struct file *filp, int on)
+{
+        struct tty_struct *tty = file_tty(filp);
+        unsigned long flags;
+        int retval = 0;
+
+        if (tty_paranoia_check(tty, filp->f_path.dentry->d_inode, "tty_fasync"))
+                goto out;
+
+        retval = fasync_helper(fd, filp, on, &tty->fasync);
+        if (retval <= 0)
+                goto out;
+
+        if (on) {
+                enum pid_type type;
+                struct pid *pid;
+                if (!waitqueue_active(&tty->read_wait))
+                        tty->minimum_to_wake = 1;
+                spin_lock_irqsave(&tty->ctrl_lock, flags);
+                if (tty->pgrp) {
+                        pid = tty->pgrp;
+                        type = PIDTYPE_PGID;
+                } else {
+                        pid = task_pid(current);
+                        type = PIDTYPE_PID;
+                }
+                get_pid(pid);
+                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                retval = __f_setown(filp, pid, type, 0);
+                put_pid(pid);
+                if (retval)
+                        goto out;
+        } else {
+                if (!tty->fasync && !waitqueue_active(&tty->read_wait))
+                        tty->minimum_to_wake = N_TTY_BUF_SIZE;
+        }
+        retval = 0;
+out:
+        return retval;
+}
+
+static int tty_fasync(int fd, struct file *filp, int on)
+{
+        int retval;
+        tty_lock();
+        retval = __tty_fasync(fd, filp, on);
+        tty_unlock();
+        return retval;
+}
+
+/**
+ *      tiocsti                 -       fake input character
+ *      @tty: tty to fake input into
+ *      @p: pointer to character
+ *
+ *      Fake input to a tty device. Does the necessary locking and
+ *      input management.
+ *
+ *      FIXME: does not honour flow control ??
+ *
+ *      Locking:
+ *              Called functions take tty_ldisc_lock
+ *              current->signal->tty check is safe without locks
+ *
+ *      FIXME: may race normal receive processing
+ */
+
+static int tiocsti(struct tty_struct *tty, char __user *p)
+{
+        char ch, mbz = 0;
+        struct tty_ldisc *ld;
+
+        if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
+                return -EPERM;
+        if (get_user(ch, p))
+                return -EFAULT;
+        tty_audit_tiocsti(tty, ch);
+        ld = tty_ldisc_ref_wait(tty);
+        ld->ops->receive_buf(tty, &ch, &mbz, 1);
+        tty_ldisc_deref(ld);
+        return 0;
+}
+
+/**
+ *      tiocgwinsz              -       implement window query ioctl
+ *      @tty; tty
+ *      @arg: user buffer for result
+ *
+ *      Copies the kernel idea of the window size into the user buffer.
+ *
+ *      Locking: tty->termios_mutex is taken to ensure the winsize data
+ *              is consistent.
+ */
+
+static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
+{
+        int err;
+
+        mutex_lock(&tty->termios_mutex);
+        err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
+        mutex_unlock(&tty->termios_mutex);
+
+        return err ? -EFAULT: 0;
+}
+
+/**
+ *      tty_do_resize           -       resize event
+ *      @tty: tty being resized
+ *      @rows: rows (character)
+ *      @cols: cols (character)
+ *
+ *      Update the termios variables and send the necessary signals to
+ *      peform a terminal resize correctly
+ */
+
+int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
+{
+        struct pid *pgrp;
+        unsigned long flags;
+
+        /* Lock the tty */
+        mutex_lock(&tty->termios_mutex);
+        if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
+                goto done;
+        /* Get the PID values and reference them so we can
+           avoid holding the tty ctrl lock while sending signals */
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        pgrp = get_pid(tty->pgrp);
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+
+        if (pgrp)
+                kill_pgrp(pgrp, SIGWINCH, 1);
+        put_pid(pgrp);
+
+        tty->winsize = *ws;
+done:
+        mutex_unlock(&tty->termios_mutex);
+        return 0;
+}
+
+/**
+ *      tiocswinsz              -       implement window size set ioctl
+ *      @tty; tty side of tty
+ *      @arg: user buffer for result
+ *
+ *      Copies the user idea of the window size to the kernel. Traditionally
+ *      this is just advisory information but for the Linux console it
+ *      actually has driver level meaning and triggers a VC resize.
+ *
+ *      Locking:
+ *              Driver dependent. The default do_resize method takes the
+ *      tty termios mutex and ctrl_lock. The console takes its own lock
+ *      then calls into the default method.
+ */
+
+static int tiocswinsz(struct tty_struct *tty, struct winsize __user *arg)
+{
+        struct winsize tmp_ws;
+        if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
+                return -EFAULT;
+
+        if (tty->ops->resize)
+                return tty->ops->resize(tty, &tmp_ws);
+        else
+                return tty_do_resize(tty, &tmp_ws);
+}
+
+/**
+ *      tioccons        -       allow admin to move logical console
+ *      @file: the file to become console
+ *
+ *      Allow the administrator to move the redirected console device
+ *
+ *      Locking: uses redirect_lock to guard the redirect information
+ */
+
+static int tioccons(struct file *file)
+{
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+        if (file->f_op->write == redirected_tty_write) {
+                struct file *f;
+                spin_lock(&redirect_lock);
+                f = redirect;
+                redirect = NULL;
+                spin_unlock(&redirect_lock);
+                if (f)
+                        fput(f);
+                return 0;
+        }
+        spin_lock(&redirect_lock);
+        if (redirect) {
+                spin_unlock(&redirect_lock);
+                return -EBUSY;
+        }
+        get_file(file);
+        redirect = file;
+        spin_unlock(&redirect_lock);
+        return 0;
+}
+
+/**
+ *      fionbio         -       non blocking ioctl
+ *      @file: file to set blocking value
+ *      @p: user parameter
+ *
+ *      Historical tty interfaces had a blocking control ioctl before
+ *      the generic functionality existed. This piece of history is preserved
+ *      in the expected tty API of posix OS's.
+ *
+ *      Locking: none, the open file handle ensures it won't go away.
+ */
+
+static int fionbio(struct file *file, int __user *p)
+{
+        int nonblock;
+
+        if (get_user(nonblock, p))
+                return -EFAULT;
+
+        spin_lock(&file->f_lock);
+        if (nonblock)
+                file->f_flags |= O_NONBLOCK;
+        else
+                file->f_flags &= ~O_NONBLOCK;
+        spin_unlock(&file->f_lock);
+        return 0;
+}
+
+/**
+ *      tiocsctty       -       set controlling tty
+ *      @tty: tty structure
+ *      @arg: user argument
+ *
+ *      This ioctl is used to manage job control. It permits a session
+ *      leader to set this tty as the controlling tty for the session.
+ *
+ *      Locking:
+ *              Takes tty_mutex() to protect tty instance
+ *              Takes tasklist_lock internally to walk sessions
+ *              Takes ->siglock() when updating signal->tty
+ */
+
+static int tiocsctty(struct tty_struct *tty, int arg)
+{
+        int ret = 0;
+        if (current->signal->leader && (task_session(current) == tty->session))
+                return ret;
+
+        mutex_lock(&tty_mutex);
+        /*
+         * The process must be a session leader and
+         * not have a controlling tty already.
+         */
+        if (!current->signal->leader || current->signal->tty) {
+                ret = -EPERM;
+                goto unlock;
+        }
+
+        if (tty->session) {
+                /*
+                 * This tty is already the controlling
+                 * tty for another session group!
+                 */
+                if (arg == 1 && capable(CAP_SYS_ADMIN)) {
+                        /*
+                         * Steal it away
+                         */
+                        read_lock(&tasklist_lock);
+                        session_clear_tty(tty->session);
+                        read_unlock(&tasklist_lock);
+                } else {
+                        ret = -EPERM;
+                        goto unlock;
+                }
+        }
+        proc_set_tty(current, tty);
+unlock:
+        mutex_unlock(&tty_mutex);
+        return ret;
+}
+
+/**
+ *      tty_get_pgrp    -       return a ref counted pgrp pid
+ *      @tty: tty to read
+ *
+ *      Returns a refcounted instance of the pid struct for the process
+ *      group controlling the tty.
+ */
+
+struct pid *tty_get_pgrp(struct tty_struct *tty)
+{
+        unsigned long flags;
+        struct pid *pgrp;
+
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        pgrp = get_pid(tty->pgrp);
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+
+        return pgrp;
+}
+EXPORT_SYMBOL_GPL(tty_get_pgrp);
+
+/**
+ *      tiocgpgrp               -       get process group
+ *      @tty: tty passed by user
+ *      @real_tty: tty side of the tty passed by the user if a pty else the tty
+ *      @p: returned pid
+ *
+ *      Obtain the process group of the tty. If there is no process group
+ *      return an error.
+ *
+ *      Locking: none. Reference to current->signal->tty is safe.
+ */
+
+static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+        struct pid *pid;
+        int ret;
+        /*
+         * (tty == real_tty) is a cheap way of
+         * testing if the tty is NOT a master pty.
+         */
+        if (tty == real_tty && current->signal->tty != real_tty)
+                return -ENOTTY;
+        pid = tty_get_pgrp(real_tty);
+        ret =  put_user(pid_vnr(pid), p);
+        put_pid(pid);
+        return ret;
+}
+
+/**
+ *      tiocspgrp               -       attempt to set process group
+ *      @tty: tty passed by user
+ *      @real_tty: tty side device matching tty passed by user
+ *      @p: pid pointer
+ *
+ *      Set the process group of the tty to the session passed. Only
+ *      permitted where the tty session is our session.
+ *
+ *      Locking: RCU, ctrl lock
+ */
+
+static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+        struct pid *pgrp;
+        pid_t pgrp_nr;
+        int retval = tty_check_change(real_tty);
+        unsigned long flags;
+
+        if (retval == -EIO)
+                return -ENOTTY;
+        if (retval)
+                return retval;
+        if (!current->signal->tty ||
+            (current->signal->tty != real_tty) ||
+            (real_tty->session != task_session(current)))
+                return -ENOTTY;
+        if (get_user(pgrp_nr, p))
+                return -EFAULT;
+        if (pgrp_nr < 0)
+                return -EINVAL;
+        rcu_read_lock();
+        pgrp = find_vpid(pgrp_nr);
+        retval = -ESRCH;
+        if (!pgrp)
+                goto out_unlock;
+        retval = -EPERM;
+        if (session_of_pgrp(pgrp) != task_session(current))
+                goto out_unlock;
+        retval = 0;
+        spin_lock_irqsave(&tty->ctrl_lock, flags);
+        put_pid(real_tty->pgrp);
+        real_tty->pgrp = get_pid(pgrp);
+        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+out_unlock:
+        rcu_read_unlock();
+        return retval;
+}
+
+/**
+ *      tiocgsid                -       get session id
+ *      @tty: tty passed by user
+ *      @real_tty: tty side of the tty passed by the user if a pty else the tty
+ *      @p: pointer to returned session id
+ *
+ *      Obtain the session id of the tty. If there is no session
+ *      return an error.
+ *
+ *      Locking: none. Reference to current->signal->tty is safe.
+ */
+
+static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
+{
+        /*
+         * (tty == real_tty) is a cheap way of
+         * testing if the tty is NOT a master pty.
+        */
+        if (tty == real_tty && current->signal->tty != real_tty)
+                return -ENOTTY;
+        if (!real_tty->session)
+                return -ENOTTY;
+        return put_user(pid_vnr(real_tty->session), p);
+}
+
+/**
+ *      tiocsetd        -       set line discipline
+ *      @tty: tty device
+ *      @p: pointer to user data
+ *
+ *      Set the line discipline according to user request.
+ *
+ *      Locking: see tty_set_ldisc, this function is just a helper
+ */
+
+static int tiocsetd(struct tty_struct *tty, int __user *p)
+{
+        int ldisc;
+        int ret;
+
+        if (get_user(ldisc, p))
+                return -EFAULT;
+
+        ret = tty_set_ldisc(tty, ldisc);
+
+        return ret;
+}
+
+/**
+ *      send_break      -       performed time break
+ *      @tty: device to break on
+ *      @duration: timeout in mS
+ *
+ *      Perform a timed break on hardware that lacks its own driver level
+ *      timed break functionality.
+ *
+ *      Locking:
+ *              atomic_write_lock serializes
+ *
+ */
+
+static int send_break(struct tty_struct *tty, unsigned int duration)
+{
+        int retval;
+
+        if (tty->ops->break_ctl == NULL)
+                return 0;
+
+        if (tty->driver->flags & TTY_DRIVER_HARDWARE_BREAK)
+                retval = tty->ops->break_ctl(tty, duration);
+        else {
+                /* Do the work ourselves */
+                if (tty_write_lock(tty, 0) < 0)
+                        return -EINTR;
+                retval = tty->ops->break_ctl(tty, -1);
+                if (retval)
+                        goto out;
+                if (!signal_pending(current))
+                        msleep_interruptible(duration);
+                retval = tty->ops->break_ctl(tty, 0);
+out:
+                tty_write_unlock(tty);
+                if (signal_pending(current))
+                        retval = -EINTR;
+        }
+        return retval;
+}
+
+/**
+ *      tty_tiocmget            -       get modem status
+ *      @tty: tty device
+ *      @file: user file pointer
+ *      @p: pointer to result
+ *
+ *      Obtain the modem status bits from the tty driver if the feature
+ *      is supported. Return -EINVAL if it is not available.
+ *
+ *      Locking: none (up to the driver)
+ */
+
+static int tty_tiocmget(struct tty_struct *tty, int __user *p)
+{
+        int retval = -EINVAL;
+
+        if (tty->ops->tiocmget) {
+                retval = tty->ops->tiocmget(tty);
+
+                if (retval >= 0)
+                        retval = put_user(retval, p);
+        }
+        return retval;
+}
+
+/**
+ *      tty_tiocmset            -       set modem status
+ *      @tty: tty device
+ *      @cmd: command - clear bits, set bits or set all
+ *      @p: pointer to desired bits
+ *
+ *      Set the modem status bits from the tty driver if the feature
+ *      is supported. Return -EINVAL if it is not available.
+ *
+ *      Locking: none (up to the driver)
+ */
+
+static int tty_tiocmset(struct tty_struct *tty, unsigned int cmd,
+             unsigned __user *p)
+{
+        int retval;
+        unsigned int set, clear, val;
+
+        if (tty->ops->tiocmset == NULL)
+                return -EINVAL;
+
+        retval = get_user(val, p);
+        if (retval)
+                return retval;
+        set = clear = 0;
+        switch (cmd) {
+        case TIOCMBIS:
+                set = val;
+                break;
+        case TIOCMBIC:
+                clear = val;
+                break;
+        case TIOCMSET:
+                set = val;
+                clear = ~val;
+                break;
+        }
+        set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
+        clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
+        return tty->ops->tiocmset(tty, set, clear);
+}
+
+static int tty_tiocgicount(struct tty_struct *tty, void __user *arg)
+{
+        int retval = -EINVAL;
+        struct serial_icounter_struct icount;
+        memset(&icount, 0, sizeof(icount));
+        if (tty->ops->get_icount)
+                retval = tty->ops->get_icount(tty, &icount);
+        if (retval != 0)
+                return retval;
+        if (copy_to_user(arg, &icount, sizeof(icount)))
+                return -EFAULT;
+        return 0;
+}
+
+struct tty_struct *tty_pair_get_tty(struct tty_struct *tty)
+{
+        if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+            tty->driver->subtype == PTY_TYPE_MASTER)
+                tty = tty->link;
+        return tty;
+}
+EXPORT_SYMBOL(tty_pair_get_tty);
+
+struct tty_struct *tty_pair_get_pty(struct tty_struct *tty)
+{
+        if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
+            tty->driver->subtype == PTY_TYPE_MASTER)
+            return tty;
+        return tty->link;
+}
+EXPORT_SYMBOL(tty_pair_get_pty);
+
+/*
+ * Split this up, as gcc can choke on it otherwise..
+ */
+long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+        struct tty_struct *tty = file_tty(file);
+        struct tty_struct *real_tty;
+        void __user *p = (void __user *)arg;
+        int retval;
+        struct tty_ldisc *ld;
+        struct inode *inode = file->f_dentry->d_inode;
+
+        if (tty_paranoia_check(tty, inode, "tty_ioctl"))
+                return -EINVAL;
+
+        real_tty = tty_pair_get_tty(tty);
+
+        /*
+         * Factor out some common prep work
+         */
+        switch (cmd) {
+        case TIOCSETD:
+        case TIOCSBRK:
+        case TIOCCBRK:
+        case TCSBRK:
+        case TCSBRKP:
+                retval = tty_check_change(tty);
+                if (retval)
+                        return retval;
+                if (cmd != TIOCCBRK) {
+                        tty_wait_until_sent(tty, 0);
+                        if (signal_pending(current))
+                                return -EINTR;
+                }
+                break;
+        }
+
+        /*
+         *      Now do the stuff.
+         */
+        switch (cmd) {
+        case TIOCSTI:
+                return tiocsti(tty, p);
+        case TIOCGWINSZ:
+                return tiocgwinsz(real_tty, p);
+        case TIOCSWINSZ:
+                return tiocswinsz(real_tty, p);
+        case TIOCCONS:
+                return real_tty != tty ? -EINVAL : tioccons(file);
+        case FIONBIO:
+                return fionbio(file, p);
+        case TIOCEXCL:
+                set_bit(TTY_EXCLUSIVE, &tty->flags);
+                return 0;
+        case TIOCNXCL:
+                clear_bit(TTY_EXCLUSIVE, &tty->flags);
+                return 0;
+        case TIOCNOTTY:
+                if (current->signal->tty != tty)
+                        return -ENOTTY;
+                no_tty();
+                return 0;
+        case TIOCSCTTY:
+                return tiocsctty(tty, arg);
+        case TIOCGPGRP:
+                return tiocgpgrp(tty, real_tty, p);
+        case TIOCSPGRP:
+                return tiocspgrp(tty, real_tty, p);
+        case TIOCGSID:
+                return tiocgsid(tty, real_tty, p);
+        case TIOCGETD:
+                return put_user(tty->ldisc->ops->num, (int __user *)p);
+        case TIOCSETD:
+                return tiocsetd(tty, p);
+        case TIOCVHANGUP:
+                if (!capable(CAP_SYS_ADMIN))
+                        return -EPERM;
+                tty_vhangup(tty);
+                return 0;
+        case TIOCGDEV:
+        {
+                unsigned int ret = new_encode_dev(tty_devnum(real_tty));
+                return put_user(ret, (unsigned int __user *)p);
+        }
+        /*
+         * Break handling
+         */
+        case TIOCSBRK:  /* Turn break on, unconditionally */
+                if (tty->ops->break_ctl)
+                        return tty->ops->break_ctl(tty, -1);
+                return 0;
+        case TIOCCBRK:  /* Turn break off, unconditionally */
+                if (tty->ops->break_ctl)
+                        return tty->ops->break_ctl(tty, 0);
+                return 0;
+        case TCSBRK:   /* SVID version: non-zero arg --> no break */
+                /* non-zero arg means wait for all output data
+                 * to be sent (performed above) but don't send break.
+                 * This is used by the tcdrain() termios function.
+                 */
+                if (!arg)
+                        return send_break(tty, 250);
+                return 0;
+        case TCSBRKP:   /* support for POSIX tcsendbreak() */
+                return send_break(tty, arg ? arg*100 : 250);
+
+        case TIOCMGET:
+                return tty_tiocmget(tty, p);
+        case TIOCMSET:
+        case TIOCMBIC:
+        case TIOCMBIS:
+                return tty_tiocmset(tty, cmd, p);
+        case TIOCGICOUNT:
+                retval = tty_tiocgicount(tty, p);
+                /* For the moment allow fall through to the old method */
+                if (retval != -EINVAL)
+                        return retval;
+                break;
+        case TCFLSH:
+                switch (arg) {
+                case TCIFLUSH:
+                case TCIOFLUSH:
+                /* flush tty buffer and allow ldisc to process ioctl */
+                        tty_buffer_flush(tty);
+                        break;
+                }
+                break;
+        }
+        if (tty->ops->ioctl) {
+                retval = (tty->ops->ioctl)(tty, cmd, arg);
+                if (retval != -ENOIOCTLCMD)
+                        return retval;
+        }
+        ld = tty_ldisc_ref_wait(tty);
+        retval = -EINVAL;
+        if (ld->ops->ioctl) {
+                retval = ld->ops->ioctl(tty, file, cmd, arg);
+                if (retval == -ENOIOCTLCMD)
+                        retval = -EINVAL;
+        }
+        tty_ldisc_deref(ld);
+        return retval;
+}
+
+#ifdef CONFIG_COMPAT
+static long tty_compat_ioctl(struct file *file, unsigned int cmd,
+                                unsigned long arg)
+{
+        struct inode *inode = file->f_dentry->d_inode;
+        struct tty_struct *tty = file_tty(file);
+        struct tty_ldisc *ld;
+        int retval = -ENOIOCTLCMD;
+
+        if (tty_paranoia_check(tty, inode, "tty_ioctl"))
+                return -EINVAL;
+
+        if (tty->ops->compat_ioctl) {
+                retval = (tty->ops->compat_ioctl)(tty, cmd, arg);
+                if (retval != -ENOIOCTLCMD)
+                        return retval;
+        }
+
+        ld = tty_ldisc_ref_wait(tty);
+        if (ld->ops->compat_ioctl)
+                retval = ld->ops->compat_ioctl(tty, file, cmd, arg);
+        tty_ldisc_deref(ld);
+
+        return retval;
+}
+#endif
+
+/*
+ * This implements the "Secure Attention Key" ---  the idea is to
+ * prevent trojan horses by killing all processes associated with this
+ * tty when the user hits the "Secure Attention Key".  Required for
+ * super-paranoid applications --- see the Orange Book for more details.
+ *
+ * This code could be nicer; ideally it should send a HUP, wait a few
+ * seconds, then send a INT, and then a KILL signal.  But you then
+ * have to coordinate with the init process, since all processes associated
+ * with the current tty must be dead before the new getty is allowed
+ * to spawn.
+ *
+ * Now, if it would be correct ;-/ The current code has a nasty hole -
+ * it doesn't catch files in flight. We may send the descriptor to ourselves
+ * via AF_UNIX socket, close it and later fetch from socket. FIXME.
+ *
+ * Nasty bug: do_SAK is being called in interrupt context.  This can
+ * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
+ */
+void __do_SAK(struct tty_struct *tty)
+{
+#ifdef TTY_SOFT_SAK
+        tty_hangup(tty);
+#else
+        struct task_struct *g, *p;
+        struct pid *session;
+        int             i;
+        struct file     *filp;
+        struct fdtable *fdt;
+
+        if (!tty)
+                return;
+        session = tty->session;
+
+        tty_ldisc_flush(tty);
+
+        tty_driver_flush_buffer(tty);
+
+        read_lock(&tasklist_lock);
+        /* Kill the entire session */
+        do_each_pid_task(session, PIDTYPE_SID, p) {
+                printk(KERN_NOTICE "SAK: killed process %d"
+                        " (%s): task_session(p)==tty->session\n",
+                        task_pid_nr(p), p->comm);
+                send_sig(SIGKILL, p, 1);
+        } while_each_pid_task(session, PIDTYPE_SID, p);
+        /* Now kill any processes that happen to have the
+         * tty open.
+         */
+        do_each_thread(g, p) {
+                if (p->signal->tty == tty) {
+                        printk(KERN_NOTICE "SAK: killed process %d"
+                            " (%s): task_session(p)==tty->session\n",
+                            task_pid_nr(p), p->comm);
+                        send_sig(SIGKILL, p, 1);
+                        continue;
+                }
+                task_lock(p);
+                if (p->files) {
+                        /*
+                         * We don't take a ref to the file, so we must
+                         * hold ->file_lock instead.
+                         */
+                        spin_lock(&p->files->file_lock);
+                        fdt = files_fdtable(p->files);
+                        for (i = 0; i < fdt->max_fds; i++) {
+                                filp = fcheck_files(p->files, i);
+                                if (!filp)
+                                        continue;
+                                if (filp->f_op->read == tty_read &&
+                                    file_tty(filp) == tty) {
+                                        printk(KERN_NOTICE "SAK: killed process %d"
+                                            " (%s): fd#%d opened to the tty\n",
+                                            task_pid_nr(p), p->comm, i);
+                                        force_sig(SIGKILL, p);
+                                        break;
+                                }
+                        }
+                        spin_unlock(&p->files->file_lock);
+                }
+                task_unlock(p);
+        } while_each_thread(g, p);
+        read_unlock(&tasklist_lock);
+#endif
+}
+
+static void do_SAK_work(struct work_struct *work)
+{
+        struct tty_struct *tty =
+                container_of(work, struct tty_struct, SAK_work);
+        __do_SAK(tty);
+}
+
+/*
+ * The tq handling here is a little racy - tty->SAK_work may already be queued.
+ * Fortunately we don't need to worry, because if ->SAK_work is already queued,
+ * the values which we write to it will be identical to the values which it
+ * already has. --akpm
+ */
+void do_SAK(struct tty_struct *tty)
+{
+        if (!tty)
+                return;
+        schedule_work(&tty->SAK_work);
+}
+
+EXPORT_SYMBOL(do_SAK);
+
+static int dev_match_devt(struct device *dev, void *data)
+{
+        dev_t *devt = data;
+        return dev->devt == *devt;
+}
+
+/* Must put_device() after it's unused! */
+static struct device *tty_get_device(struct tty_struct *tty)
+{
+        dev_t devt = tty_devnum(tty);
+        return class_find_device(tty_class, NULL, &devt, dev_match_devt);
+}
+
+
+/**
+ *      initialize_tty_struct
+ *      @tty: tty to initialize
+ *
+ *      This subroutine initializes a tty structure that has been newly
+ *      allocated.
+ *
+ *      Locking: none - tty in question must not be exposed at this point
+ */
+
+void initialize_tty_struct(struct tty_struct *tty,
+                struct tty_driver *driver, int idx)
+{
+        memset(tty, 0, sizeof(struct tty_struct));
+        kref_init(&tty->kref);
+        tty->magic = TTY_MAGIC;
+        tty_ldisc_init(tty);
+        tty->session = NULL;
+        tty->pgrp = NULL;
+        tty->overrun_time = jiffies;
+        tty->buf.head = tty->buf.tail = NULL;
+        tty_buffer_init(tty);
+        mutex_init(&tty->termios_mutex);
+        mutex_init(&tty->ldisc_mutex);
+        init_waitqueue_head(&tty->write_wait);
+        init_waitqueue_head(&tty->read_wait);
+        INIT_WORK(&tty->hangup_work, do_tty_hangup);
+        mutex_init(&tty->atomic_read_lock);
+        mutex_init(&tty->atomic_write_lock);
+        mutex_init(&tty->output_lock);
+        mutex_init(&tty->echo_lock);
+        spin_lock_init(&tty->read_lock);
+        spin_lock_init(&tty->ctrl_lock);
+        INIT_LIST_HEAD(&tty->tty_files);
+        INIT_WORK(&tty->SAK_work, do_SAK_work);
+
+        tty->driver = driver;
+        tty->ops = driver->ops;
+        tty->index = idx;
+        tty_line_name(driver, idx, tty->name);
+        tty->dev = tty_get_device(tty);
+}
+
+/**
+ *      deinitialize_tty_struct
+ *      @tty: tty to deinitialize
+ *
+ *      This subroutine deinitializes a tty structure that has been newly
+ *      allocated but tty_release cannot be called on that yet.
+ *
+ *      Locking: none - tty in question must not be exposed at this point
+ */
+void deinitialize_tty_struct(struct tty_struct *tty)
+{
+        tty_ldisc_deinit(tty);
+}
+
+/**
+ *      tty_put_char    -       write one character to a tty
+ *      @tty: tty
+ *      @ch: character
+ *
+ *      Write one byte to the tty using the provided put_char method
+ *      if present. Returns the number of characters successfully output.
+ *
+ *      Note: the specific put_char operation in the driver layer may go
+ *      away soon. Don't call it directly, use this method
+ */
+
+int tty_put_char(struct tty_struct *tty, unsigned char ch)
+{
+        if (tty->ops->put_char)
+                return tty->ops->put_char(tty, ch);
+        return tty->ops->write(tty, &ch, 1);
+}
+EXPORT_SYMBOL_GPL(tty_put_char);
+
+struct class *tty_class;
+
+/**
+ *      tty_register_device - register a tty device
+ *      @driver: the tty driver that describes the tty device
+ *      @index: the index in the tty driver for this tty device
+ *      @device: a struct device that is associated with this tty device.
+ *              This field is optional, if there is no known struct device
+ *              for this tty device it can be set to NULL safely.
+ *
+ *      Returns a pointer to the struct device for this tty device
+ *      (or ERR_PTR(-EFOO) on error).
+ *
+ *      This call is required to be made to register an individual tty device
+ *      if the tty driver's flags have the TTY_DRIVER_DYNAMIC_DEV bit set.  If
+ *      that bit is not set, this function should not be called by a tty
+ *      driver.
+ *
+ *      Locking: ??
+ */
+
+struct device *tty_register_device(struct tty_driver *driver, unsigned index,
+                                   struct device *device)
+{
+        char name[64];
+        dev_t dev = MKDEV(driver->major, driver->minor_start) + index;
+
+        if (index >= driver->num) {
+                printk(KERN_ERR "Attempt to register invalid tty line number "
+                       " (%d).\n", index);
+                return ERR_PTR(-EINVAL);
+        }
+
+        if (driver->type == TTY_DRIVER_TYPE_PTY)
+                pty_line_name(driver, index, name);
+        else
+                tty_line_name(driver, index, name);
+
+        return device_create(tty_class, device, dev, NULL, name);
+}
+EXPORT_SYMBOL(tty_register_device);
+
+/**
+ *      tty_unregister_device - unregister a tty device
+ *      @driver: the tty driver that describes the tty device
+ *      @index: the index in the tty driver for this tty device
+ *
+ *      If a tty device is registered with a call to tty_register_device() then
+ *      this function must be called when the tty device is gone.
+ *
+ *      Locking: ??
+ */
+
+void tty_unregister_device(struct tty_driver *driver, unsigned index)
+{
+        device_destroy(tty_class,
+                MKDEV(driver->major, driver->minor_start) + index);
+}
+EXPORT_SYMBOL(tty_unregister_device);
+
+struct tty_driver *alloc_tty_driver(int lines)
+{
+        struct tty_driver *driver;
+
+        driver = kzalloc(sizeof(struct tty_driver), GFP_KERNEL);
+        if (driver) {
+                kref_init(&driver->kref);
+                driver->magic = TTY_DRIVER_MAGIC;
+                driver->num = lines;
+                /* later we'll move allocation of tables here */
+        }
+        return driver;
+}
+EXPORT_SYMBOL(alloc_tty_driver);
+
+static void destruct_tty_driver(struct kref *kref)
+{
+        struct tty_driver *driver = container_of(kref, struct tty_driver, kref);
+        int i;
+        struct ktermios *tp;
+        void *p;
+
+        if (driver->flags & TTY_DRIVER_INSTALLED) {
+                /*
+                 * Free the termios and termios_locked structures because
+                 * we don't want to get memory leaks when modular tty
+                 * drivers are removed from the kernel.
+                 */
+                for (i = 0; i < driver->num; i++) {
+                        tp = driver->termios[i];
+                        if (tp) {
+                                driver->termios[i] = NULL;
+                                kfree(tp);
+                        }
+                        if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV))
+                                tty_unregister_device(driver, i);
+                }
+                p = driver->ttys;
+                proc_tty_unregister_driver(driver);
+                driver->ttys = NULL;
+                driver->termios = NULL;
+                kfree(p);
+                cdev_del(&driver->cdev);
+        }
+        kfree(driver);
+}
+
+void tty_driver_kref_put(struct tty_driver *driver)
+{
+        kref_put(&driver->kref, destruct_tty_driver);
+}
+EXPORT_SYMBOL(tty_driver_kref_put);
+
+void tty_set_operations(struct tty_driver *driver,
+                        const struct tty_operations *op)
+{
+        driver->ops = op;
+};
+EXPORT_SYMBOL(tty_set_operations);
+
+void put_tty_driver(struct tty_driver *d)
+{
+        tty_driver_kref_put(d);
+}
+EXPORT_SYMBOL(put_tty_driver);
+
+/*
+ * Called by a tty driver to register itself.
+ */
+int tty_register_driver(struct tty_driver *driver)
+{
+        int error;
+        int i;
+        dev_t dev;
+        void **p = NULL;
+        struct device *d;
+
+        if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) {
+                p = kzalloc(driver->num * 2 * sizeof(void *), GFP_KERNEL);
+                if (!p)
+                        return -ENOMEM;
+        }
+
+        if (!driver->major) {
+                error = alloc_chrdev_region(&dev, driver->minor_start,
+                                                driver->num, driver->name);
+                if (!error) {
+                        driver->major = MAJOR(dev);
+                        driver->minor_start = MINOR(dev);
+                }
+        } else {
+                dev = MKDEV(driver->major, driver->minor_start);
+                error = register_chrdev_region(dev, driver->num, driver->name);
+        }
+        if (error < 0) {
+                kfree(p);
+                return error;
+        }
+
+        if (p) {
+                driver->ttys = (struct tty_struct **)p;
+                driver->termios = (struct ktermios **)(p + driver->num);
+        } else {
+                driver->ttys = NULL;
+                driver->termios = NULL;
+        }
+
+        cdev_init(&driver->cdev, &tty_fops);
+        driver->cdev.owner = driver->owner;
+        error = cdev_add(&driver->cdev, dev, driver->num);
+        if (error) {
+                unregister_chrdev_region(dev, driver->num);
+                driver->ttys = NULL;
+                driver->termios = NULL;
+                kfree(p);
+                return error;
+        }
+
+        mutex_lock(&tty_mutex);
+        list_add(&driver->tty_drivers, &tty_drivers);
+        mutex_unlock(&tty_mutex);
+
+        if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
+                for (i = 0; i < driver->num; i++) {
+                        d = tty_register_device(driver, i, NULL);
+                        if (IS_ERR(d)) {
+                                error = PTR_ERR(d);
+                                goto err;
+                        }
+                }
+        }
+        proc_tty_register_driver(driver);
+        driver->flags |= TTY_DRIVER_INSTALLED;
+        return 0;
+
+err:
+        for (i--; i >= 0; i--)
+                tty_unregister_device(driver, i);
+
+        mutex_lock(&tty_mutex);
+        list_del(&driver->tty_drivers);
+        mutex_unlock(&tty_mutex);
+
+        unregister_chrdev_region(dev, driver->num);
+        driver->ttys = NULL;
+        driver->termios = NULL;
+        kfree(p);
+        return error;
+}
+
+EXPORT_SYMBOL(tty_register_driver);
+
+/*
+ * Called by a tty driver to unregister itself.
+ */
+int tty_unregister_driver(struct tty_driver *driver)
+{
+#if 0
+        /* FIXME */
+        if (driver->refcount)
+                return -EBUSY;
+#endif
+        unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
+                                driver->num);
+        mutex_lock(&tty_mutex);
+        list_del(&driver->tty_drivers);
+        mutex_unlock(&tty_mutex);
+        return 0;
+}
+
+EXPORT_SYMBOL(tty_unregister_driver);
+
+dev_t tty_devnum(struct tty_struct *tty)
+{
+        return MKDEV(tty->driver->major, tty->driver->minor_start) + tty->index;
+}
+EXPORT_SYMBOL(tty_devnum);
+
+void proc_clear_tty(struct task_struct *p)
+{
+        unsigned long flags;
+        struct tty_struct *tty;
+        spin_lock_irqsave(&p->sighand->siglock, flags);
+        tty = p->signal->tty;
+        p->signal->tty = NULL;
+        spin_unlock_irqrestore(&p->sighand->siglock, flags);
+        tty_kref_put(tty);
+}
+
+/* Called under the sighand lock */
+
+static void __proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
+{
+        if (tty) {
+                unsigned long flags;
+                /* We should not have a session or pgrp to put here but.... */
+                spin_lock_irqsave(&tty->ctrl_lock, flags);
+                put_pid(tty->session);
+                put_pid(tty->pgrp);
+                tty->pgrp = get_pid(task_pgrp(tsk));
+                spin_unlock_irqrestore(&tty->ctrl_lock, flags);
+                tty->session = get_pid(task_session(tsk));
+                if (tsk->signal->tty) {
+                        printk(KERN_DEBUG "tty not NULL!!\n");
+                        tty_kref_put(tsk->signal->tty);
+                }
+        }
+        put_pid(tsk->signal->tty_old_pgrp);
+        tsk->signal->tty = tty_kref_get(tty);
+        tsk->signal->tty_old_pgrp = NULL;
+}
+
+static void proc_set_tty(struct task_struct *tsk, struct tty_struct *tty)
+{
+        spin_lock_irq(&tsk->sighand->siglock);
+        __proc_set_tty(tsk, tty);
+        spin_unlock_irq(&tsk->sighand->siglock);
+}
+
+struct tty_struct *get_current_tty(void)
+{
+        struct tty_struct *tty;
+        unsigned long flags;
+
+        spin_lock_irqsave(&current->sighand->siglock, flags);
+        tty = tty_kref_get(current->signal->tty);
+        spin_unlock_irqrestore(&current->sighand->siglock, flags);
+        return tty;
+}
+EXPORT_SYMBOL_GPL(get_current_tty);
+
+void tty_default_fops(struct file_operations *fops)
+{
+        *fops = tty_fops;
+}
+
+/*
+ * Initialize the console device. This is called *early*, so
+ * we can't necessarily depend on lots of kernel help here.
+ * Just do some early initializations, and do the complex setup
+ * later.
+ */
+void __init console_init(void)
+{
+        initcall_t *call;
+
+        /* Setup the default TTY line discipline. */
+        tty_ldisc_begin();
+
+        /*
+         * set up the console device so that later boot sequences can
+         * inform about problems etc..
+         */
+        call = __con_initcall_start;
+        while (call < __con_initcall_end) {
+                (*call)();
+                call++;
+        }
+}
+
+static char *tty_devnode(struct device *dev, mode_t *mode)
+{
+        if (!mode)
+                return NULL;
+        if (dev->devt == MKDEV(TTYAUX_MAJOR, 0) ||
+            dev->devt == MKDEV(TTYAUX_MAJOR, 2))
+                *mode = 0666;
+        return NULL;
+}
+
+static int __init tty_class_init(void)
+{
+        tty_class = class_create(THIS_MODULE, "tty");
+        if (IS_ERR(tty_class))
+                return PTR_ERR(tty_class);
+        tty_class->devnode = tty_devnode;
+        return 0;
+}
+
+postcore_initcall(tty_class_init);
+
+/* 3/2004 jmc: why do these devices exist? */
+static struct cdev tty_cdev, console_cdev;
+
+static ssize_t show_cons_active(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        struct console *cs[16];
+        int i = 0;
+        struct console *c;
+        ssize_t count = 0;
+
+        console_lock();
+        for_each_console(c) {
+                if (!c->device)
+                        continue;
+                if (!c->write)
+                        continue;
+                if ((c->flags & CON_ENABLED) == 0)
+                        continue;
+                cs[i++] = c;
+                if (i >= ARRAY_SIZE(cs))
+                        break;
+        }
+        while (i--)
+                count += sprintf(buf + count, "%s%d%c",
+                                 cs[i]->name, cs[i]->index, i ? ' ':'\n');
+        console_unlock();
+
+        return count;
+}
+static DEVICE_ATTR(active, S_IRUGO, show_cons_active, NULL);
+
+static struct device *consdev;
+
+void console_sysfs_notify(void)
+{
+        if (consdev)
+                sysfs_notify(&consdev->kobj, NULL, "active");
+}
+
+/*
+ * Ok, now we can initialize the rest of the tty devices and can count
+ * on memory allocations, interrupts etc..
+ */
+int __init tty_init(void)
+{
+        cdev_init(&tty_cdev, &tty_fops);
+        if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
+            register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
+                panic("Couldn't register /dev/tty driver\n");
+        device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");
+
+        cdev_init(&console_cdev, &console_fops);
+        if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
+            register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
+                panic("Couldn't register /dev/console driver\n");
+        consdev = device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 1), NULL,
+                              "console");
+        if (IS_ERR(consdev))
+                consdev = NULL;
+        else
+                WARN_ON(device_create_file(consdev, &dev_attr_active) < 0);
+
+#ifdef CONFIG_VT
+        vty_init(&console_fops);
+#endif
+        return 0;
+}
+