| #include <linux/types.h> |
| #include <linux/errno.h> |
| #include <linux/kmod.h> |
| #include <linux/sched.h> |
| #include <linux/interrupt.h> |
| #include <linux/tty.h> |
| #include <linux/tty_driver.h> |
| #include <linux/file.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/seq_file.h> |
| #include <linux/uaccess.h> |
| #include <linux/ratelimit.h> |
| |
| #undef LDISC_DEBUG_HANGUP |
| |
| #ifdef LDISC_DEBUG_HANGUP |
| #define tty_ldisc_debug(tty, f, args...) ({ \ |
| char __b[64]; \ |
| printk(KERN_DEBUG "%s: %s: " f, __func__, tty_name(tty, __b), ##args); \ |
| }) |
| #else |
| #define tty_ldisc_debug(tty, f, args...) |
| #endif |
| |
| /* lockdep nested classes for tty->ldisc_sem */ |
| enum { |
| LDISC_SEM_NORMAL, |
| LDISC_SEM_OTHER, |
| }; |
| |
| |
| /* |
| * This guards the refcounted line discipline lists. The lock |
| * must be taken with irqs off because there are hangup path |
| * callers who will do ldisc lookups and cannot sleep. |
| */ |
| |
| static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
| /* Line disc dispatch table */ |
| static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; |
| |
| /** |
| * tty_register_ldisc - install a line discipline |
| * @disc: ldisc number |
| * @new_ldisc: pointer to the ldisc object |
| * |
| * Installs a new line discipline into the kernel. The discipline |
| * is set up as unreferenced and then made available to the kernel |
| * from this point onwards. |
| * |
| * Locking: |
| * takes tty_ldiscs_lock to guard against ldisc races |
| */ |
| |
| int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) |
| { |
| unsigned long flags; |
| int ret = 0; |
| |
| if (disc < N_TTY || disc >= NR_LDISCS) |
| return -EINVAL; |
| |
| raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
| tty_ldiscs[disc] = new_ldisc; |
| new_ldisc->num = disc; |
| new_ldisc->refcount = 0; |
| raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(tty_register_ldisc); |
| |
| /** |
| * tty_unregister_ldisc - unload a line discipline |
| * @disc: ldisc number |
| * @new_ldisc: pointer to the ldisc object |
| * |
| * Remove a line discipline from the kernel providing it is not |
| * currently in use. |
| * |
| * Locking: |
| * takes tty_ldiscs_lock to guard against ldisc races |
| */ |
| |
| int tty_unregister_ldisc(int disc) |
| { |
| unsigned long flags; |
| int ret = 0; |
| |
| if (disc < N_TTY || disc >= NR_LDISCS) |
| return -EINVAL; |
| |
| raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
| if (tty_ldiscs[disc]->refcount) |
| ret = -EBUSY; |
| else |
| tty_ldiscs[disc] = NULL; |
| raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL(tty_unregister_ldisc); |
| |
| static struct tty_ldisc_ops *get_ldops(int disc) |
| { |
| unsigned long flags; |
| struct tty_ldisc_ops *ldops, *ret; |
| |
| raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
| ret = ERR_PTR(-EINVAL); |
| ldops = tty_ldiscs[disc]; |
| if (ldops) { |
| ret = ERR_PTR(-EAGAIN); |
| if (try_module_get(ldops->owner)) { |
| ldops->refcount++; |
| ret = ldops; |
| } |
| } |
| raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
| return ret; |
| } |
| |
| static void put_ldops(struct tty_ldisc_ops *ldops) |
| { |
| unsigned long flags; |
| |
| raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
| ldops->refcount--; |
| module_put(ldops->owner); |
| raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
| } |
| |
| /** |
| * tty_ldisc_get - take a reference to an ldisc |
| * @disc: ldisc number |
| * |
| * Takes a reference to a line discipline. Deals with refcounts and |
| * module locking counts. Returns NULL if the discipline is not available. |
| * Returns a pointer to the discipline and bumps the ref count if it is |
| * available |
| * |
| * Locking: |
| * takes tty_ldiscs_lock to guard against ldisc races |
| */ |
| |
| static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
| { |
| struct tty_ldisc *ld; |
| struct tty_ldisc_ops *ldops; |
| |
| if (disc < N_TTY || disc >= NR_LDISCS) |
| return ERR_PTR(-EINVAL); |
| |
| /* |
| * Get the ldisc ops - we may need to request them to be loaded |
| * dynamically and try again. |
| */ |
| ldops = get_ldops(disc); |
| if (IS_ERR(ldops)) { |
| request_module("tty-ldisc-%d", disc); |
| ldops = get_ldops(disc); |
| if (IS_ERR(ldops)) |
| return ERR_CAST(ldops); |
| } |
| |
| ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL); |
| if (ld == NULL) { |
| put_ldops(ldops); |
| return ERR_PTR(-ENOMEM); |
| } |
| |
| ld->ops = ldops; |
| ld->tty = tty; |
| |
| return ld; |
| } |
| |
| /** |
| * tty_ldisc_put - release the ldisc |
| * |
| * Complement of tty_ldisc_get(). |
| */ |
| static inline void tty_ldisc_put(struct tty_ldisc *ld) |
| { |
| if (WARN_ON_ONCE(!ld)) |
| return; |
| |
| put_ldops(ld->ops); |
| kfree(ld); |
| } |
| |
| static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
| { |
| return (*pos < NR_LDISCS) ? pos : NULL; |
| } |
| |
| static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
| { |
| (*pos)++; |
| return (*pos < NR_LDISCS) ? pos : NULL; |
| } |
| |
| static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) |
| { |
| } |
| |
| static int tty_ldiscs_seq_show(struct seq_file *m, void *v) |
| { |
| int i = *(loff_t *)v; |
| struct tty_ldisc_ops *ldops; |
| |
| ldops = get_ldops(i); |
| if (IS_ERR(ldops)) |
| return 0; |
| seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
| put_ldops(ldops); |
| return 0; |
| } |
| |
| static const struct seq_operations tty_ldiscs_seq_ops = { |
| .start = tty_ldiscs_seq_start, |
| .next = tty_ldiscs_seq_next, |
| .stop = tty_ldiscs_seq_stop, |
| .show = tty_ldiscs_seq_show, |
| }; |
| |
| static int proc_tty_ldiscs_open(struct inode *inode, struct file *file) |
| { |
| return seq_open(file, &tty_ldiscs_seq_ops); |
| } |
| |
| const struct file_operations tty_ldiscs_proc_fops = { |
| .owner = THIS_MODULE, |
| .open = proc_tty_ldiscs_open, |
| .read = seq_read, |
| .llseek = seq_lseek, |
| .release = seq_release, |
| }; |
| |
| /** |
| * tty_ldisc_ref_wait - wait for the tty ldisc |
| * @tty: tty device |
| * |
| * Dereference the line discipline for the terminal and take a |
| * reference to it. If the line discipline is in flux then |
| * wait patiently until it changes. |
| * |
| * Note: Must not be called from an IRQ/timer context. The caller |
| * must also be careful not to hold other locks that will deadlock |
| * against a discipline change, such as an existing ldisc reference |
| * (which we check for) |
| * |
| * Note: only callable from a file_operations routine (which |
| * guarantees tty->ldisc != NULL when the lock is acquired). |
| */ |
| |
| struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |
| { |
| ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
| WARN_ON(!tty->ldisc); |
| return tty->ldisc; |
| } |
| EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
| |
| /** |
| * tty_ldisc_ref - get the tty ldisc |
| * @tty: tty device |
| * |
| * Dereference the line discipline for the terminal and take a |
| * reference to it. If the line discipline is in flux then |
| * return NULL. Can be called from IRQ and timer functions. |
| */ |
| |
| struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) |
| { |
| struct tty_ldisc *ld = NULL; |
| |
| if (ldsem_down_read_trylock(&tty->ldisc_sem)) { |
| ld = tty->ldisc; |
| if (!ld) |
| ldsem_up_read(&tty->ldisc_sem); |
| } |
| return ld; |
| } |
| EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
| |
| /** |
| * tty_ldisc_deref - free a tty ldisc reference |
| * @ld: reference to free up |
| * |
| * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May |
| * be called in IRQ context. |
| */ |
| |
| void tty_ldisc_deref(struct tty_ldisc *ld) |
| { |
| ldsem_up_read(&ld->tty->ldisc_sem); |
| } |
| EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
| |
| |
| static inline int __lockfunc |
| tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
| { |
| return ldsem_down_write(&tty->ldisc_sem, timeout); |
| } |
| |
| static inline int __lockfunc |
| tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
| { |
| return ldsem_down_write_nested(&tty->ldisc_sem, |
| LDISC_SEM_OTHER, timeout); |
| } |
| |
| static inline void tty_ldisc_unlock(struct tty_struct *tty) |
| { |
| return ldsem_up_write(&tty->ldisc_sem); |
| } |
| |
| static int __lockfunc |
| tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
| unsigned long timeout) |
| { |
| int ret; |
| |
| if (tty < tty2) { |
| ret = tty_ldisc_lock(tty, timeout); |
| if (ret) { |
| ret = tty_ldisc_lock_nested(tty2, timeout); |
| if (!ret) |
| tty_ldisc_unlock(tty); |
| } |
| } else { |
| /* if this is possible, it has lots of implications */ |
| WARN_ON_ONCE(tty == tty2); |
| if (tty2 && tty != tty2) { |
| ret = tty_ldisc_lock(tty2, timeout); |
| if (ret) { |
| ret = tty_ldisc_lock_nested(tty, timeout); |
| if (!ret) |
| tty_ldisc_unlock(tty2); |
| } |
| } else |
| ret = tty_ldisc_lock(tty, timeout); |
| } |
| |
| if (!ret) |
| return -EBUSY; |
| |
| set_bit(TTY_LDISC_HALTED, &tty->flags); |
| if (tty2) |
| set_bit(TTY_LDISC_HALTED, &tty2->flags); |
| return 0; |
| } |
| |
| static void __lockfunc |
| tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
| { |
| tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); |
| } |
| |
| static void __lockfunc tty_ldisc_unlock_pair(struct tty_struct *tty, |
| struct tty_struct *tty2) |
| { |
| tty_ldisc_unlock(tty); |
| if (tty2) |
| tty_ldisc_unlock(tty2); |
| } |
| |
| static void __lockfunc tty_ldisc_enable_pair(struct tty_struct *tty, |
| struct tty_struct *tty2) |
| { |
| clear_bit(TTY_LDISC_HALTED, &tty->flags); |
| if (tty2) |
| clear_bit(TTY_LDISC_HALTED, &tty2->flags); |
| |
| tty_ldisc_unlock_pair(tty, tty2); |
| } |
| |
| /** |
| * tty_ldisc_flush - flush line discipline queue |
| * @tty: tty |
| * |
| * Flush the line discipline queue (if any) for this tty. If there |
| * is no line discipline active this is a no-op. |
| */ |
| |
| void tty_ldisc_flush(struct tty_struct *tty) |
| { |
| struct tty_ldisc *ld = tty_ldisc_ref(tty); |
| if (ld) { |
| if (ld->ops->flush_buffer) |
| ld->ops->flush_buffer(tty); |
| tty_ldisc_deref(ld); |
| } |
| tty_buffer_flush(tty); |
| } |
| EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
| |
| /** |
| * tty_set_termios_ldisc - set ldisc field |
| * @tty: tty structure |
| * @num: line discipline number |
| * |
| * This is probably overkill for real world processors but |
| * they are not on hot paths so a little discipline won't do |
| * any harm. |
| * |
| * Locking: takes termios_mutex |
| */ |
| |
| static void tty_set_termios_ldisc(struct tty_struct *tty, int num) |
| { |
| mutex_lock(&tty->termios_mutex); |
| tty->termios.c_line = num; |
| mutex_unlock(&tty->termios_mutex); |
| } |
| |
| /** |
| * tty_ldisc_open - open a line discipline |
| * @tty: tty we are opening the ldisc on |
| * @ld: discipline to open |
| * |
| * A helper opening method. Also a convenient debugging and check |
| * point. |
| * |
| * Locking: always called with BTM already held. |
| */ |
| |
| static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) |
| { |
| WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); |
| if (ld->ops->open) { |
| int ret; |
| /* BTM here locks versus a hangup event */ |
| ret = ld->ops->open(tty); |
| if (ret) |
| clear_bit(TTY_LDISC_OPEN, &tty->flags); |
| return ret; |
| } |
| return 0; |
| } |
| |
| /** |
| * tty_ldisc_close - close a line discipline |
| * @tty: tty we are opening the ldisc on |
| * @ld: discipline to close |
| * |
| * A helper close method. Also a convenient debugging and check |
| * point. |
| */ |
| |
| static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) |
| { |
| WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
| clear_bit(TTY_LDISC_OPEN, &tty->flags); |
| if (ld->ops->close) |
| ld->ops->close(tty); |
| } |
| |
| /** |
| * tty_ldisc_restore - helper for tty ldisc change |
| * @tty: tty to recover |
| * @old: previous ldisc |
| * |
| * Restore the previous line discipline or N_TTY when a line discipline |
| * change fails due to an open error |
| */ |
| |
| static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) |
| { |
| char buf[64]; |
| struct tty_ldisc *new_ldisc; |
| int r; |
| |
| /* There is an outstanding reference here so this is safe */ |
| old = tty_ldisc_get(tty, old->ops->num); |
| WARN_ON(IS_ERR(old)); |
| tty->ldisc = old; |
| tty_set_termios_ldisc(tty, old->ops->num); |
| if (tty_ldisc_open(tty, old) < 0) { |
| tty_ldisc_put(old); |
| /* This driver is always present */ |
| new_ldisc = tty_ldisc_get(tty, N_TTY); |
| if (IS_ERR(new_ldisc)) |
| panic("n_tty: get"); |
| tty->ldisc = new_ldisc; |
| tty_set_termios_ldisc(tty, N_TTY); |
| r = tty_ldisc_open(tty, new_ldisc); |
| if (r < 0) |
| panic("Couldn't open N_TTY ldisc for " |
| "%s --- error %d.", |
| tty_name(tty, buf), r); |
| } |
| } |
| |
| /** |
| * tty_set_ldisc - set line discipline |
| * @tty: the terminal to set |
| * @ldisc: the line discipline |
| * |
| * Set the discipline of a tty line. Must be called from a process |
| * context. The ldisc change logic has to protect itself against any |
| * overlapping ldisc change (including on the other end of pty pairs), |
| * the close of one side of a tty/pty pair, and eventually hangup. |
| */ |
| |
| int tty_set_ldisc(struct tty_struct *tty, int ldisc) |
| { |
| int retval; |
| struct tty_ldisc *o_ldisc, *new_ldisc; |
| struct tty_struct *o_tty = tty->link; |
| |
| new_ldisc = tty_ldisc_get(tty, ldisc); |
| if (IS_ERR(new_ldisc)) |
| return PTR_ERR(new_ldisc); |
| |
| retval = tty_ldisc_lock_pair_timeout(tty, o_tty, 5 * HZ); |
| if (retval) { |
| tty_ldisc_put(new_ldisc); |
| return retval; |
| } |
| |
| /* |
| * Check the no-op case |
| */ |
| |
| if (tty->ldisc->ops->num == ldisc) { |
| tty_ldisc_enable_pair(tty, o_tty); |
| tty_ldisc_put(new_ldisc); |
| return 0; |
| } |
| |
| /* FIXME: why 'shutoff' input if the ldisc is locked? */ |
| tty->receive_room = 0; |
| |
| o_ldisc = tty->ldisc; |
| tty_lock(tty); |
| |
| /* FIXME: for testing only */ |
| WARN_ON(test_bit(TTY_HUPPED, &tty->flags)); |
| |
| if (test_bit(TTY_HUPPING, &tty->flags)) { |
| /* We were raced by the hangup method. It will have stomped |
| the ldisc data and closed the ldisc down */ |
| tty_ldisc_enable_pair(tty, o_tty); |
| tty_ldisc_put(new_ldisc); |
| tty_unlock(tty); |
| return -EIO; |
| } |
| |
| /* Shutdown the current discipline. */ |
| tty_ldisc_close(tty, o_ldisc); |
| |
| /* Now set up the new line discipline. */ |
| tty->ldisc = new_ldisc; |
| tty_set_termios_ldisc(tty, ldisc); |
| |
| retval = tty_ldisc_open(tty, new_ldisc); |
| if (retval < 0) { |
| /* Back to the old one or N_TTY if we can't */ |
| tty_ldisc_put(new_ldisc); |
| tty_ldisc_restore(tty, o_ldisc); |
| } |
| |
| /* At this point we hold a reference to the new ldisc and a |
| a reference to the old ldisc. If we ended up flipping back |
| to the existing ldisc we have two references to it */ |
| |
| if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc) |
| tty->ops->set_ldisc(tty); |
| |
| tty_ldisc_put(o_ldisc); |
| |
| /* |
| * Allow ldisc referencing to occur again |
| */ |
| tty_ldisc_enable_pair(tty, o_tty); |
| |
| /* Restart the work queue in case no characters kick it off. Safe if |
| already running */ |
| schedule_work(&tty->port->buf.work); |
| if (o_tty) |
| schedule_work(&o_tty->port->buf.work); |
| |
| tty_unlock(tty); |
| return retval; |
| } |
| |
| /** |
| * tty_reset_termios - reset terminal state |
| * @tty: tty to reset |
| * |
| * Restore a terminal to the driver default state. |
| */ |
| |
| static void tty_reset_termios(struct tty_struct *tty) |
| { |
| mutex_lock(&tty->termios_mutex); |
| tty->termios = tty->driver->init_termios; |
| tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); |
| tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); |
| mutex_unlock(&tty->termios_mutex); |
| } |
| |
| |
| /** |
| * tty_ldisc_reinit - reinitialise the tty ldisc |
| * @tty: tty to reinit |
| * @ldisc: line discipline to reinitialize |
| * |
| * Switch the tty to a line discipline and leave the ldisc |
| * state closed |
| */ |
| |
| static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc) |
| { |
| struct tty_ldisc *ld = tty_ldisc_get(tty, ldisc); |
| |
| if (IS_ERR(ld)) |
| return -1; |
| |
| tty_ldisc_close(tty, tty->ldisc); |
| tty_ldisc_put(tty->ldisc); |
| /* |
| * Switch the line discipline back |
| */ |
| tty->ldisc = ld; |
| tty_set_termios_ldisc(tty, ldisc); |
| |
| return 0; |
| } |
| |
| /** |
| * tty_ldisc_hangup - hangup ldisc reset |
| * @tty: tty being hung up |
| * |
| * Some tty devices reset their termios when they receive a hangup |
| * event. In that situation we must also switch back to N_TTY properly |
| * before we reset the termios data. |
| * |
| * Locking: We can take the ldisc mutex as the rest of the code is |
| * careful to allow for this. |
| * |
| * In the pty pair case this occurs in the close() path of the |
| * tty itself so we must be careful about locking rules. |
| */ |
| |
| void tty_ldisc_hangup(struct tty_struct *tty) |
| { |
| struct tty_ldisc *ld; |
| int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS; |
| int err = 0; |
| |
| tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
| |
| ld = tty_ldisc_ref(tty); |
| if (ld != NULL) { |
| if (ld->ops->flush_buffer) |
| ld->ops->flush_buffer(tty); |
| tty_driver_flush_buffer(tty); |
| if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && |
| ld->ops->write_wakeup) |
| ld->ops->write_wakeup(tty); |
| if (ld->ops->hangup) |
| ld->ops->hangup(tty); |
| tty_ldisc_deref(ld); |
| } |
| |
| wake_up_interruptible_poll(&tty->write_wait, POLLOUT); |
| wake_up_interruptible_poll(&tty->read_wait, POLLIN); |
| |
| tty_unlock(tty); |
| |
| /* |
| * Shutdown the current line discipline, and reset it to |
| * N_TTY if need be. |
| * |
| * Avoid racing set_ldisc or tty_ldisc_release |
| */ |
| tty_ldisc_lock_pair(tty, tty->link); |
| tty_lock(tty); |
| |
| if (tty->ldisc) { |
| |
| /* At this point we have a halted ldisc; we want to close it and |
| reopen a new ldisc. We could defer the reopen to the next |
| open but it means auditing a lot of other paths so this is |
| a FIXME */ |
| if (reset == 0) { |
| |
| if (!tty_ldisc_reinit(tty, tty->termios.c_line)) |
| err = tty_ldisc_open(tty, tty->ldisc); |
| else |
| err = 1; |
| } |
| /* If the re-open fails or we reset then go to N_TTY. The |
| N_TTY open cannot fail */ |
| if (reset || err) { |
| BUG_ON(tty_ldisc_reinit(tty, N_TTY)); |
| WARN_ON(tty_ldisc_open(tty, tty->ldisc)); |
| } |
| } |
| tty_ldisc_enable_pair(tty, tty->link); |
| if (reset) |
| tty_reset_termios(tty); |
| |
| tty_ldisc_debug(tty, "re-opened ldisc: %p\n", tty->ldisc); |
| } |
| |
| /** |
| * tty_ldisc_setup - open line discipline |
| * @tty: tty being shut down |
| * @o_tty: pair tty for pty/tty pairs |
| * |
| * Called during the initial open of a tty/pty pair in order to set up the |
| * line disciplines and bind them to the tty. This has no locking issues |
| * as the device isn't yet active. |
| */ |
| |
| int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) |
| { |
| struct tty_ldisc *ld = tty->ldisc; |
| int retval; |
| |
| retval = tty_ldisc_open(tty, ld); |
| if (retval) |
| return retval; |
| |
| if (o_tty) { |
| retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
| if (retval) { |
| tty_ldisc_close(tty, ld); |
| return retval; |
| } |
| } |
| return 0; |
| } |
| |
| static void tty_ldisc_kill(struct tty_struct *tty) |
| { |
| /* |
| * Now kill off the ldisc |
| */ |
| tty_ldisc_close(tty, tty->ldisc); |
| tty_ldisc_put(tty->ldisc); |
| /* Force an oops if we mess this up */ |
| tty->ldisc = NULL; |
| |
| /* Ensure the next open requests the N_TTY ldisc */ |
| tty_set_termios_ldisc(tty, N_TTY); |
| } |
| |
| /** |
| * tty_ldisc_release - release line discipline |
| * @tty: tty being shut down |
| * @o_tty: pair tty for pty/tty pairs |
| * |
| * Called during the final close of a tty/pty pair in order to shut down |
| * the line discpline layer. On exit the ldisc assigned is N_TTY and the |
| * ldisc has not been opened. |
| */ |
| |
| void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty) |
| { |
| /* |
| * Shutdown this line discipline. As this is the final close, |
| * it does not race with the set_ldisc code path. |
| */ |
| |
| tty_ldisc_debug(tty, "closing ldisc: %p\n", tty->ldisc); |
| |
| tty_ldisc_lock_pair(tty, o_tty); |
| tty_lock_pair(tty, o_tty); |
| |
| tty_ldisc_kill(tty); |
| if (o_tty) |
| tty_ldisc_kill(o_tty); |
| |
| tty_unlock_pair(tty, o_tty); |
| tty_ldisc_unlock_pair(tty, o_tty); |
| |
| /* And the memory resources remaining (buffers, termios) will be |
| disposed of when the kref hits zero */ |
| |
| tty_ldisc_debug(tty, "ldisc closed\n"); |
| } |
| |
| /** |
| * tty_ldisc_init - ldisc setup for new tty |
| * @tty: tty being allocated |
| * |
| * Set up the line discipline objects for a newly allocated tty. Note that |
| * the tty structure is not completely set up when this call is made. |
| */ |
| |
| void tty_ldisc_init(struct tty_struct *tty) |
| { |
| struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
| if (IS_ERR(ld)) |
| panic("n_tty: init_tty"); |
| tty->ldisc = ld; |
| } |
| |
| /** |
| * tty_ldisc_init - ldisc cleanup for new tty |
| * @tty: tty that was allocated recently |
| * |
| * The tty structure must not becompletely set up (tty_ldisc_setup) when |
| * this call is made. |
| */ |
| void tty_ldisc_deinit(struct tty_struct *tty) |
| { |
| tty_ldisc_put(tty->ldisc); |
| tty->ldisc = NULL; |
| } |
| |
| void tty_ldisc_begin(void) |
| { |
| /* Setup the default TTY line discipline. */ |
| (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY); |
| } |