1e3b3d0f5SGreg Kroah-Hartman // SPDX-License-Identifier: GPL-2.0 296fd7ce5SGreg Kroah-Hartman #include <linux/types.h> 396fd7ce5SGreg Kroah-Hartman #include <linux/errno.h> 48b3ffa17SJiri Slaby #include <linux/kmod.h> 596fd7ce5SGreg Kroah-Hartman #include <linux/sched.h> 696fd7ce5SGreg Kroah-Hartman #include <linux/interrupt.h> 796fd7ce5SGreg Kroah-Hartman #include <linux/tty.h> 896fd7ce5SGreg Kroah-Hartman #include <linux/tty_driver.h> 996fd7ce5SGreg Kroah-Hartman #include <linux/file.h> 1096fd7ce5SGreg Kroah-Hartman #include <linux/mm.h> 1196fd7ce5SGreg Kroah-Hartman #include <linux/string.h> 1296fd7ce5SGreg Kroah-Hartman #include <linux/slab.h> 1396fd7ce5SGreg Kroah-Hartman #include <linux/poll.h> 1496fd7ce5SGreg Kroah-Hartman #include <linux/proc_fs.h> 1596fd7ce5SGreg Kroah-Hartman #include <linux/module.h> 1696fd7ce5SGreg Kroah-Hartman #include <linux/device.h> 1796fd7ce5SGreg Kroah-Hartman #include <linux/wait.h> 1896fd7ce5SGreg Kroah-Hartman #include <linux/bitops.h> 1996fd7ce5SGreg Kroah-Hartman #include <linux/seq_file.h> 2096fd7ce5SGreg Kroah-Hartman #include <linux/uaccess.h> 210c73c08eSJiri Slaby #include <linux/ratelimit.h> 2296fd7ce5SGreg Kroah-Hartman 23fc575ee6SPeter Hurley #undef LDISC_DEBUG_HANGUP 24fc575ee6SPeter Hurley 25fc575ee6SPeter Hurley #ifdef LDISC_DEBUG_HANGUP 260a6adc13SPeter Hurley #define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) 27fc575ee6SPeter Hurley #else 28fc575ee6SPeter Hurley #define tty_ldisc_debug(tty, f, args...) 29fc575ee6SPeter Hurley #endif 30fc575ee6SPeter Hurley 31d2c43890SPeter Hurley /* lockdep nested classes for tty->ldisc_sem */ 32d2c43890SPeter Hurley enum { 33d2c43890SPeter Hurley LDISC_SEM_NORMAL, 34d2c43890SPeter Hurley LDISC_SEM_OTHER, 35d2c43890SPeter Hurley }; 36d2c43890SPeter Hurley 37d2c43890SPeter Hurley 3896fd7ce5SGreg Kroah-Hartman /* 3996fd7ce5SGreg Kroah-Hartman * This guards the refcounted line discipline lists. The lock 4096fd7ce5SGreg Kroah-Hartman * must be taken with irqs off because there are hangup path 4196fd7ce5SGreg Kroah-Hartman * callers who will do ldisc lookups and cannot sleep. 4296fd7ce5SGreg Kroah-Hartman */ 4396fd7ce5SGreg Kroah-Hartman 44137084bbSPeter Hurley static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); 4596fd7ce5SGreg Kroah-Hartman /* Line disc dispatch table */ 4696fd7ce5SGreg Kroah-Hartman static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; 4796fd7ce5SGreg Kroah-Hartman 4896fd7ce5SGreg Kroah-Hartman /** 4996fd7ce5SGreg Kroah-Hartman * tty_register_ldisc - install a line discipline 5096fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 5196fd7ce5SGreg Kroah-Hartman * @new_ldisc: pointer to the ldisc object 5296fd7ce5SGreg Kroah-Hartman * 5396fd7ce5SGreg Kroah-Hartman * Installs a new line discipline into the kernel. The discipline 5496fd7ce5SGreg Kroah-Hartman * is set up as unreferenced and then made available to the kernel 5596fd7ce5SGreg Kroah-Hartman * from this point onwards. 5696fd7ce5SGreg Kroah-Hartman * 5796fd7ce5SGreg Kroah-Hartman * Locking: 58137084bbSPeter Hurley * takes tty_ldiscs_lock to guard against ldisc races 5996fd7ce5SGreg Kroah-Hartman */ 6096fd7ce5SGreg Kroah-Hartman 6196fd7ce5SGreg Kroah-Hartman int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc) 6296fd7ce5SGreg Kroah-Hartman { 6396fd7ce5SGreg Kroah-Hartman unsigned long flags; 6496fd7ce5SGreg Kroah-Hartman int ret = 0; 6596fd7ce5SGreg Kroah-Hartman 6696fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 6796fd7ce5SGreg Kroah-Hartman return -EINVAL; 6896fd7ce5SGreg Kroah-Hartman 69137084bbSPeter Hurley raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); 7096fd7ce5SGreg Kroah-Hartman tty_ldiscs[disc] = new_ldisc; 7196fd7ce5SGreg Kroah-Hartman new_ldisc->num = disc; 7296fd7ce5SGreg Kroah-Hartman new_ldisc->refcount = 0; 73137084bbSPeter Hurley raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); 7496fd7ce5SGreg Kroah-Hartman 7596fd7ce5SGreg Kroah-Hartman return ret; 7696fd7ce5SGreg Kroah-Hartman } 7796fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL(tty_register_ldisc); 7896fd7ce5SGreg Kroah-Hartman 7996fd7ce5SGreg Kroah-Hartman /** 8096fd7ce5SGreg Kroah-Hartman * tty_unregister_ldisc - unload a line discipline 8196fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 8296fd7ce5SGreg Kroah-Hartman * 8396fd7ce5SGreg Kroah-Hartman * Remove a line discipline from the kernel providing it is not 8496fd7ce5SGreg Kroah-Hartman * currently in use. 8596fd7ce5SGreg Kroah-Hartman * 8696fd7ce5SGreg Kroah-Hartman * Locking: 87137084bbSPeter Hurley * takes tty_ldiscs_lock to guard against ldisc races 8896fd7ce5SGreg Kroah-Hartman */ 8996fd7ce5SGreg Kroah-Hartman 9096fd7ce5SGreg Kroah-Hartman int tty_unregister_ldisc(int disc) 9196fd7ce5SGreg Kroah-Hartman { 9296fd7ce5SGreg Kroah-Hartman unsigned long flags; 9396fd7ce5SGreg Kroah-Hartman int ret = 0; 9496fd7ce5SGreg Kroah-Hartman 9596fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 9696fd7ce5SGreg Kroah-Hartman return -EINVAL; 9796fd7ce5SGreg Kroah-Hartman 98137084bbSPeter Hurley raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); 9996fd7ce5SGreg Kroah-Hartman if (tty_ldiscs[disc]->refcount) 10096fd7ce5SGreg Kroah-Hartman ret = -EBUSY; 10196fd7ce5SGreg Kroah-Hartman else 10296fd7ce5SGreg Kroah-Hartman tty_ldiscs[disc] = NULL; 103137084bbSPeter Hurley raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); 10496fd7ce5SGreg Kroah-Hartman 10596fd7ce5SGreg Kroah-Hartman return ret; 10696fd7ce5SGreg Kroah-Hartman } 10796fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL(tty_unregister_ldisc); 10896fd7ce5SGreg Kroah-Hartman 10996fd7ce5SGreg Kroah-Hartman static struct tty_ldisc_ops *get_ldops(int disc) 11096fd7ce5SGreg Kroah-Hartman { 11196fd7ce5SGreg Kroah-Hartman unsigned long flags; 11296fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops, *ret; 11396fd7ce5SGreg Kroah-Hartman 114137084bbSPeter Hurley raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); 11596fd7ce5SGreg Kroah-Hartman ret = ERR_PTR(-EINVAL); 11696fd7ce5SGreg Kroah-Hartman ldops = tty_ldiscs[disc]; 11796fd7ce5SGreg Kroah-Hartman if (ldops) { 11896fd7ce5SGreg Kroah-Hartman ret = ERR_PTR(-EAGAIN); 11996fd7ce5SGreg Kroah-Hartman if (try_module_get(ldops->owner)) { 12096fd7ce5SGreg Kroah-Hartman ldops->refcount++; 12196fd7ce5SGreg Kroah-Hartman ret = ldops; 12296fd7ce5SGreg Kroah-Hartman } 12396fd7ce5SGreg Kroah-Hartman } 124137084bbSPeter Hurley raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); 12596fd7ce5SGreg Kroah-Hartman return ret; 12696fd7ce5SGreg Kroah-Hartman } 12796fd7ce5SGreg Kroah-Hartman 12896fd7ce5SGreg Kroah-Hartman static void put_ldops(struct tty_ldisc_ops *ldops) 12996fd7ce5SGreg Kroah-Hartman { 13096fd7ce5SGreg Kroah-Hartman unsigned long flags; 13196fd7ce5SGreg Kroah-Hartman 132137084bbSPeter Hurley raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); 13396fd7ce5SGreg Kroah-Hartman ldops->refcount--; 13496fd7ce5SGreg Kroah-Hartman module_put(ldops->owner); 135137084bbSPeter Hurley raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); 13696fd7ce5SGreg Kroah-Hartman } 13796fd7ce5SGreg Kroah-Hartman 13896fd7ce5SGreg Kroah-Hartman /** 13996fd7ce5SGreg Kroah-Hartman * tty_ldisc_get - take a reference to an ldisc 140*8a3bdec1SLee Jones * @tty: tty device 14196fd7ce5SGreg Kroah-Hartman * @disc: ldisc number 14296fd7ce5SGreg Kroah-Hartman * 14396fd7ce5SGreg Kroah-Hartman * Takes a reference to a line discipline. Deals with refcounts and 144c0cc1c5dSPeter Hurley * module locking counts. 145c0cc1c5dSPeter Hurley * 146c0cc1c5dSPeter Hurley * Returns: -EINVAL if the discipline index is not [N_TTY..NR_LDISCS] or 147c0cc1c5dSPeter Hurley * if the discipline is not registered 148c0cc1c5dSPeter Hurley * -EAGAIN if request_module() failed to load or register the 149c0cc1c5dSPeter Hurley * the discipline 150c0cc1c5dSPeter Hurley * -ENOMEM if allocation failure 151c0cc1c5dSPeter Hurley * 152c0cc1c5dSPeter Hurley * Otherwise, returns a pointer to the discipline and bumps the 153c0cc1c5dSPeter Hurley * ref count 15496fd7ce5SGreg Kroah-Hartman * 15596fd7ce5SGreg Kroah-Hartman * Locking: 156137084bbSPeter Hurley * takes tty_ldiscs_lock to guard against ldisc races 15796fd7ce5SGreg Kroah-Hartman */ 15896fd7ce5SGreg Kroah-Hartman 159530c4ba3SPavel Machek static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); 1607c0cca7cSGreg Kroah-Hartman 16136697529SPeter Hurley static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) 16296fd7ce5SGreg Kroah-Hartman { 16396fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 16496fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops; 16596fd7ce5SGreg Kroah-Hartman 16696fd7ce5SGreg Kroah-Hartman if (disc < N_TTY || disc >= NR_LDISCS) 16796fd7ce5SGreg Kroah-Hartman return ERR_PTR(-EINVAL); 16896fd7ce5SGreg Kroah-Hartman 16996fd7ce5SGreg Kroah-Hartman /* 17096fd7ce5SGreg Kroah-Hartman * Get the ldisc ops - we may need to request them to be loaded 17196fd7ce5SGreg Kroah-Hartman * dynamically and try again. 17296fd7ce5SGreg Kroah-Hartman */ 17396fd7ce5SGreg Kroah-Hartman ldops = get_ldops(disc); 17496fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) { 1757c0cca7cSGreg Kroah-Hartman if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) 1767c0cca7cSGreg Kroah-Hartman return ERR_PTR(-EPERM); 17796fd7ce5SGreg Kroah-Hartman request_module("tty-ldisc-%d", disc); 17896fd7ce5SGreg Kroah-Hartman ldops = get_ldops(disc); 17996fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) 18096fd7ce5SGreg Kroah-Hartman return ERR_CAST(ldops); 18196fd7ce5SGreg Kroah-Hartman } 18296fd7ce5SGreg Kroah-Hartman 183bcdd0ca8STetsuo Handa /* 184bcdd0ca8STetsuo Handa * There is no way to handle allocation failure of only 16 bytes. 185bcdd0ca8STetsuo Handa * Let's simplify error handling and save more memory. 186bcdd0ca8STetsuo Handa */ 187bcdd0ca8STetsuo Handa ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); 18896fd7ce5SGreg Kroah-Hartman ld->ops = ldops; 18936697529SPeter Hurley ld->tty = tty; 1901541f845SIvo Sieben 19196fd7ce5SGreg Kroah-Hartman return ld; 19296fd7ce5SGreg Kroah-Hartman } 19396fd7ce5SGreg Kroah-Hartman 194734de249SPeter Hurley /** 195734de249SPeter Hurley * tty_ldisc_put - release the ldisc 196734de249SPeter Hurley * 197734de249SPeter Hurley * Complement of tty_ldisc_get(). 198734de249SPeter Hurley */ 199cb128f69SDenys Vlasenko static void tty_ldisc_put(struct tty_ldisc *ld) 200734de249SPeter Hurley { 201734de249SPeter Hurley if (WARN_ON_ONCE(!ld)) 202734de249SPeter Hurley return; 203734de249SPeter Hurley 20436697529SPeter Hurley put_ldops(ld->ops); 205734de249SPeter Hurley kfree(ld); 206734de249SPeter Hurley } 207734de249SPeter Hurley 20896fd7ce5SGreg Kroah-Hartman static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) 20996fd7ce5SGreg Kroah-Hartman { 21096fd7ce5SGreg Kroah-Hartman return (*pos < NR_LDISCS) ? pos : NULL; 21196fd7ce5SGreg Kroah-Hartman } 21296fd7ce5SGreg Kroah-Hartman 21396fd7ce5SGreg Kroah-Hartman static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) 21496fd7ce5SGreg Kroah-Hartman { 21596fd7ce5SGreg Kroah-Hartman (*pos)++; 21696fd7ce5SGreg Kroah-Hartman return (*pos < NR_LDISCS) ? pos : NULL; 21796fd7ce5SGreg Kroah-Hartman } 21896fd7ce5SGreg Kroah-Hartman 21996fd7ce5SGreg Kroah-Hartman static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) 22096fd7ce5SGreg Kroah-Hartman { 22196fd7ce5SGreg Kroah-Hartman } 22296fd7ce5SGreg Kroah-Hartman 22396fd7ce5SGreg Kroah-Hartman static int tty_ldiscs_seq_show(struct seq_file *m, void *v) 22496fd7ce5SGreg Kroah-Hartman { 22596fd7ce5SGreg Kroah-Hartman int i = *(loff_t *)v; 22696fd7ce5SGreg Kroah-Hartman struct tty_ldisc_ops *ldops; 22796fd7ce5SGreg Kroah-Hartman 22896fd7ce5SGreg Kroah-Hartman ldops = get_ldops(i); 22996fd7ce5SGreg Kroah-Hartman if (IS_ERR(ldops)) 23096fd7ce5SGreg Kroah-Hartman return 0; 23196fd7ce5SGreg Kroah-Hartman seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); 23296fd7ce5SGreg Kroah-Hartman put_ldops(ldops); 23396fd7ce5SGreg Kroah-Hartman return 0; 23496fd7ce5SGreg Kroah-Hartman } 23596fd7ce5SGreg Kroah-Hartman 236fddda2b7SChristoph Hellwig const struct seq_operations tty_ldiscs_seq_ops = { 23796fd7ce5SGreg Kroah-Hartman .start = tty_ldiscs_seq_start, 23896fd7ce5SGreg Kroah-Hartman .next = tty_ldiscs_seq_next, 23996fd7ce5SGreg Kroah-Hartman .stop = tty_ldiscs_seq_stop, 24096fd7ce5SGreg Kroah-Hartman .show = tty_ldiscs_seq_show, 24196fd7ce5SGreg Kroah-Hartman }; 24296fd7ce5SGreg Kroah-Hartman 24396fd7ce5SGreg Kroah-Hartman /** 24496fd7ce5SGreg Kroah-Hartman * tty_ldisc_ref_wait - wait for the tty ldisc 24596fd7ce5SGreg Kroah-Hartman * @tty: tty device 24696fd7ce5SGreg Kroah-Hartman * 24796fd7ce5SGreg Kroah-Hartman * Dereference the line discipline for the terminal and take a 24896fd7ce5SGreg Kroah-Hartman * reference to it. If the line discipline is in flux then 24996fd7ce5SGreg Kroah-Hartman * wait patiently until it changes. 25096fd7ce5SGreg Kroah-Hartman * 251892d1fa7SPeter Hurley * Returns: NULL if the tty has been hungup and not re-opened with 252892d1fa7SPeter Hurley * a new file descriptor, otherwise valid ldisc reference 253892d1fa7SPeter Hurley * 25496fd7ce5SGreg Kroah-Hartman * Note: Must not be called from an IRQ/timer context. The caller 25596fd7ce5SGreg Kroah-Hartman * must also be careful not to hold other locks that will deadlock 25696fd7ce5SGreg Kroah-Hartman * against a discipline change, such as an existing ldisc reference 25796fd7ce5SGreg Kroah-Hartman * (which we check for) 25896fd7ce5SGreg Kroah-Hartman * 259e55afd11SPeter Hurley * Note: a file_operations routine (read/poll/write) should use this 260e55afd11SPeter Hurley * function to wait for any ldisc lifetime events to finish. 26196fd7ce5SGreg Kroah-Hartman */ 26296fd7ce5SGreg Kroah-Hartman 26396fd7ce5SGreg Kroah-Hartman struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) 26496fd7ce5SGreg Kroah-Hartman { 265a4a3e061SDmitry Vyukov struct tty_ldisc *ld; 266a4a3e061SDmitry Vyukov 26736697529SPeter Hurley ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); 268a4a3e061SDmitry Vyukov ld = tty->ldisc; 269a4a3e061SDmitry Vyukov if (!ld) 270a570a49aSPeter Hurley ldsem_up_read(&tty->ldisc_sem); 271a4a3e061SDmitry Vyukov return ld; 27296fd7ce5SGreg Kroah-Hartman } 27396fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); 27496fd7ce5SGreg Kroah-Hartman 27596fd7ce5SGreg Kroah-Hartman /** 27696fd7ce5SGreg Kroah-Hartman * tty_ldisc_ref - get the tty ldisc 27796fd7ce5SGreg Kroah-Hartman * @tty: tty device 27896fd7ce5SGreg Kroah-Hartman * 27996fd7ce5SGreg Kroah-Hartman * Dereference the line discipline for the terminal and take a 28096fd7ce5SGreg Kroah-Hartman * reference to it. If the line discipline is in flux then 28196fd7ce5SGreg Kroah-Hartman * return NULL. Can be called from IRQ and timer functions. 28296fd7ce5SGreg Kroah-Hartman */ 28396fd7ce5SGreg Kroah-Hartman 28496fd7ce5SGreg Kroah-Hartman struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) 28596fd7ce5SGreg Kroah-Hartman { 28636697529SPeter Hurley struct tty_ldisc *ld = NULL; 28736697529SPeter Hurley 28836697529SPeter Hurley if (ldsem_down_read_trylock(&tty->ldisc_sem)) { 28936697529SPeter Hurley ld = tty->ldisc; 29036697529SPeter Hurley if (!ld) 29136697529SPeter Hurley ldsem_up_read(&tty->ldisc_sem); 29236697529SPeter Hurley } 29336697529SPeter Hurley return ld; 29496fd7ce5SGreg Kroah-Hartman } 29596fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_ref); 29696fd7ce5SGreg Kroah-Hartman 29796fd7ce5SGreg Kroah-Hartman /** 29896fd7ce5SGreg Kroah-Hartman * tty_ldisc_deref - free a tty ldisc reference 29996fd7ce5SGreg Kroah-Hartman * @ld: reference to free up 30096fd7ce5SGreg Kroah-Hartman * 30196fd7ce5SGreg Kroah-Hartman * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May 30296fd7ce5SGreg Kroah-Hartman * be called in IRQ context. 30396fd7ce5SGreg Kroah-Hartman */ 30496fd7ce5SGreg Kroah-Hartman 30596fd7ce5SGreg Kroah-Hartman void tty_ldisc_deref(struct tty_ldisc *ld) 30696fd7ce5SGreg Kroah-Hartman { 30736697529SPeter Hurley ldsem_up_read(&ld->tty->ldisc_sem); 30896fd7ce5SGreg Kroah-Hartman } 30996fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_deref); 31096fd7ce5SGreg Kroah-Hartman 311d2c43890SPeter Hurley 312c2bb524bSPeter Hurley static inline int 313e80a10eeSPeter Hurley __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) 314d2c43890SPeter Hurley { 315d2c43890SPeter Hurley return ldsem_down_write(&tty->ldisc_sem, timeout); 316d2c43890SPeter Hurley } 317d2c43890SPeter Hurley 318c2bb524bSPeter Hurley static inline int 319e80a10eeSPeter Hurley __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) 320d2c43890SPeter Hurley { 321d2c43890SPeter Hurley return ldsem_down_write_nested(&tty->ldisc_sem, 322d2c43890SPeter Hurley LDISC_SEM_OTHER, timeout); 323d2c43890SPeter Hurley } 324d2c43890SPeter Hurley 325e80a10eeSPeter Hurley static inline void __tty_ldisc_unlock(struct tty_struct *tty) 326d2c43890SPeter Hurley { 32752772ea6SGuillaume Gomez ldsem_up_write(&tty->ldisc_sem); 328d2c43890SPeter Hurley } 329d2c43890SPeter Hurley 330b027e229SGaurav Kohli int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) 331fae76e9aSPeter Hurley { 332fae76e9aSPeter Hurley int ret; 333fae76e9aSPeter Hurley 334c96cf923SDmitry Safonov /* Kindly asking blocked readers to release the read side */ 335c96cf923SDmitry Safonov set_bit(TTY_LDISC_CHANGING, &tty->flags); 336c96cf923SDmitry Safonov wake_up_interruptible_all(&tty->read_wait); 337c96cf923SDmitry Safonov wake_up_interruptible_all(&tty->write_wait); 338c96cf923SDmitry Safonov 339fae76e9aSPeter Hurley ret = __tty_ldisc_lock(tty, timeout); 340fae76e9aSPeter Hurley if (!ret) 341fae76e9aSPeter Hurley return -EBUSY; 342fae76e9aSPeter Hurley set_bit(TTY_LDISC_HALTED, &tty->flags); 343fae76e9aSPeter Hurley return 0; 344fae76e9aSPeter Hurley } 345fae76e9aSPeter Hurley 346b027e229SGaurav Kohli void tty_ldisc_unlock(struct tty_struct *tty) 347fae76e9aSPeter Hurley { 348fae76e9aSPeter Hurley clear_bit(TTY_LDISC_HALTED, &tty->flags); 349c96cf923SDmitry Safonov /* Can be cleared here - ldisc_unlock will wake up writers firstly */ 350c96cf923SDmitry Safonov clear_bit(TTY_LDISC_CHANGING, &tty->flags); 351fae76e9aSPeter Hurley __tty_ldisc_unlock(tty); 352fae76e9aSPeter Hurley } 353fae76e9aSPeter Hurley 354c2bb524bSPeter Hurley static int 355d2c43890SPeter Hurley tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, 356d2c43890SPeter Hurley unsigned long timeout) 357d2c43890SPeter Hurley { 358d2c43890SPeter Hurley int ret; 359d2c43890SPeter Hurley 360d2c43890SPeter Hurley if (tty < tty2) { 361e80a10eeSPeter Hurley ret = __tty_ldisc_lock(tty, timeout); 362d2c43890SPeter Hurley if (ret) { 363e80a10eeSPeter Hurley ret = __tty_ldisc_lock_nested(tty2, timeout); 364d2c43890SPeter Hurley if (!ret) 365e80a10eeSPeter Hurley __tty_ldisc_unlock(tty); 366d2c43890SPeter Hurley } 367d2c43890SPeter Hurley } else { 368d2c43890SPeter Hurley /* if this is possible, it has lots of implications */ 369d2c43890SPeter Hurley WARN_ON_ONCE(tty == tty2); 370d2c43890SPeter Hurley if (tty2 && tty != tty2) { 371e80a10eeSPeter Hurley ret = __tty_ldisc_lock(tty2, timeout); 372d2c43890SPeter Hurley if (ret) { 373e80a10eeSPeter Hurley ret = __tty_ldisc_lock_nested(tty, timeout); 374d2c43890SPeter Hurley if (!ret) 375e80a10eeSPeter Hurley __tty_ldisc_unlock(tty2); 376d2c43890SPeter Hurley } 377d2c43890SPeter Hurley } else 378e80a10eeSPeter Hurley ret = __tty_ldisc_lock(tty, timeout); 379d2c43890SPeter Hurley } 380d2c43890SPeter Hurley 381d2c43890SPeter Hurley if (!ret) 382d2c43890SPeter Hurley return -EBUSY; 383d2c43890SPeter Hurley 384d2c43890SPeter Hurley set_bit(TTY_LDISC_HALTED, &tty->flags); 385d2c43890SPeter Hurley if (tty2) 386d2c43890SPeter Hurley set_bit(TTY_LDISC_HALTED, &tty2->flags); 387d2c43890SPeter Hurley return 0; 388d2c43890SPeter Hurley } 389d2c43890SPeter Hurley 390c2bb524bSPeter Hurley static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) 391d2c43890SPeter Hurley { 392d2c43890SPeter Hurley tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); 393d2c43890SPeter Hurley } 394d2c43890SPeter Hurley 395c2bb524bSPeter Hurley static void tty_ldisc_unlock_pair(struct tty_struct *tty, 396d2c43890SPeter Hurley struct tty_struct *tty2) 397d2c43890SPeter Hurley { 398e80a10eeSPeter Hurley __tty_ldisc_unlock(tty); 399d2c43890SPeter Hurley if (tty2) 400e80a10eeSPeter Hurley __tty_ldisc_unlock(tty2); 401d2c43890SPeter Hurley } 402d2c43890SPeter Hurley 40396fd7ce5SGreg Kroah-Hartman /** 40496fd7ce5SGreg Kroah-Hartman * tty_ldisc_flush - flush line discipline queue 40596fd7ce5SGreg Kroah-Hartman * @tty: tty 40696fd7ce5SGreg Kroah-Hartman * 40786c80a8eSPeter Hurley * Flush the line discipline queue (if any) and the tty flip buffers 40886c80a8eSPeter Hurley * for this tty. 40996fd7ce5SGreg Kroah-Hartman */ 41096fd7ce5SGreg Kroah-Hartman 41196fd7ce5SGreg Kroah-Hartman void tty_ldisc_flush(struct tty_struct *tty) 41296fd7ce5SGreg Kroah-Hartman { 41396fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld = tty_ldisc_ref(tty); 41486c80a8eSPeter Hurley 41586c80a8eSPeter Hurley tty_buffer_flush(tty, ld); 41686c80a8eSPeter Hurley if (ld) 41796fd7ce5SGreg Kroah-Hartman tty_ldisc_deref(ld); 41896fd7ce5SGreg Kroah-Hartman } 41996fd7ce5SGreg Kroah-Hartman EXPORT_SYMBOL_GPL(tty_ldisc_flush); 42096fd7ce5SGreg Kroah-Hartman 42196fd7ce5SGreg Kroah-Hartman /** 42296fd7ce5SGreg Kroah-Hartman * tty_set_termios_ldisc - set ldisc field 42396fd7ce5SGreg Kroah-Hartman * @tty: tty structure 424c12da96fSPeter Hurley * @disc: line discipline number 42596fd7ce5SGreg Kroah-Hartman * 42696fd7ce5SGreg Kroah-Hartman * This is probably overkill for real world processors but 42796fd7ce5SGreg Kroah-Hartman * they are not on hot paths so a little discipline won't do 42896fd7ce5SGreg Kroah-Hartman * any harm. 42996fd7ce5SGreg Kroah-Hartman * 430dd42bf11SPeter Hurley * The line discipline-related tty_struct fields are reset to 431dd42bf11SPeter Hurley * prevent the ldisc driver from re-using stale information for 432dd42bf11SPeter Hurley * the new ldisc instance. 433dd42bf11SPeter Hurley * 4346a1c0680SPeter Hurley * Locking: takes termios_rwsem 43596fd7ce5SGreg Kroah-Hartman */ 43696fd7ce5SGreg Kroah-Hartman 437c12da96fSPeter Hurley static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) 43896fd7ce5SGreg Kroah-Hartman { 4396a1c0680SPeter Hurley down_write(&tty->termios_rwsem); 440c12da96fSPeter Hurley tty->termios.c_line = disc; 4416a1c0680SPeter Hurley up_write(&tty->termios_rwsem); 442dd42bf11SPeter Hurley 443dd42bf11SPeter Hurley tty->disc_data = NULL; 444dd42bf11SPeter Hurley tty->receive_room = 0; 44596fd7ce5SGreg Kroah-Hartman } 44696fd7ce5SGreg Kroah-Hartman 44796fd7ce5SGreg Kroah-Hartman /** 44896fd7ce5SGreg Kroah-Hartman * tty_ldisc_open - open a line discipline 44996fd7ce5SGreg Kroah-Hartman * @tty: tty we are opening the ldisc on 45096fd7ce5SGreg Kroah-Hartman * @ld: discipline to open 45196fd7ce5SGreg Kroah-Hartman * 45296fd7ce5SGreg Kroah-Hartman * A helper opening method. Also a convenient debugging and check 45396fd7ce5SGreg Kroah-Hartman * point. 45496fd7ce5SGreg Kroah-Hartman * 45596fd7ce5SGreg Kroah-Hartman * Locking: always called with BTM already held. 45696fd7ce5SGreg Kroah-Hartman */ 45796fd7ce5SGreg Kroah-Hartman 45896fd7ce5SGreg Kroah-Hartman static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) 45996fd7ce5SGreg Kroah-Hartman { 46096fd7ce5SGreg Kroah-Hartman WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); 46196fd7ce5SGreg Kroah-Hartman if (ld->ops->open) { 46296fd7ce5SGreg Kroah-Hartman int ret; 46396fd7ce5SGreg Kroah-Hartman /* BTM here locks versus a hangup event */ 46496fd7ce5SGreg Kroah-Hartman ret = ld->ops->open(tty); 4657f90cfc5SJiri Slaby if (ret) 4667f90cfc5SJiri Slaby clear_bit(TTY_LDISC_OPEN, &tty->flags); 467fb6edc91SPeter Hurley 468a570a49aSPeter Hurley tty_ldisc_debug(tty, "%p: opened\n", ld); 46996fd7ce5SGreg Kroah-Hartman return ret; 47096fd7ce5SGreg Kroah-Hartman } 47196fd7ce5SGreg Kroah-Hartman return 0; 47296fd7ce5SGreg Kroah-Hartman } 47396fd7ce5SGreg Kroah-Hartman 47496fd7ce5SGreg Kroah-Hartman /** 47596fd7ce5SGreg Kroah-Hartman * tty_ldisc_close - close a line discipline 47696fd7ce5SGreg Kroah-Hartman * @tty: tty we are opening the ldisc on 47796fd7ce5SGreg Kroah-Hartman * @ld: discipline to close 47896fd7ce5SGreg Kroah-Hartman * 47996fd7ce5SGreg Kroah-Hartman * A helper close method. Also a convenient debugging and check 48096fd7ce5SGreg Kroah-Hartman * point. 48196fd7ce5SGreg Kroah-Hartman */ 48296fd7ce5SGreg Kroah-Hartman 48396fd7ce5SGreg Kroah-Hartman static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) 48496fd7ce5SGreg Kroah-Hartman { 4859ffbe8acSNikolay Borisov lockdep_assert_held_write(&tty->ldisc_sem); 48696fd7ce5SGreg Kroah-Hartman WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); 48796fd7ce5SGreg Kroah-Hartman clear_bit(TTY_LDISC_OPEN, &tty->flags); 48896fd7ce5SGreg Kroah-Hartman if (ld->ops->close) 48996fd7ce5SGreg Kroah-Hartman ld->ops->close(tty); 490a570a49aSPeter Hurley tty_ldisc_debug(tty, "%p: closed\n", ld); 49196fd7ce5SGreg Kroah-Hartman } 49296fd7ce5SGreg Kroah-Hartman 49396fd7ce5SGreg Kroah-Hartman /** 4948a8dabf2SAlan Cox * tty_ldisc_failto - helper for ldisc failback 4958a8dabf2SAlan Cox * @tty: tty to open the ldisc on 4968a8dabf2SAlan Cox * @ld: ldisc we are trying to fail back to 4978a8dabf2SAlan Cox * 4988a8dabf2SAlan Cox * Helper to try and recover a tty when switching back to the old 4998a8dabf2SAlan Cox * ldisc fails and we need something attached. 5008a8dabf2SAlan Cox */ 5018a8dabf2SAlan Cox 5028a8dabf2SAlan Cox static int tty_ldisc_failto(struct tty_struct *tty, int ld) 5038a8dabf2SAlan Cox { 5048a8dabf2SAlan Cox struct tty_ldisc *disc = tty_ldisc_get(tty, ld); 5058a8dabf2SAlan Cox int r; 5068a8dabf2SAlan Cox 5079ffbe8acSNikolay Borisov lockdep_assert_held_write(&tty->ldisc_sem); 5088a8dabf2SAlan Cox if (IS_ERR(disc)) 5098a8dabf2SAlan Cox return PTR_ERR(disc); 5108a8dabf2SAlan Cox tty->ldisc = disc; 5118a8dabf2SAlan Cox tty_set_termios_ldisc(tty, ld); 5128a8dabf2SAlan Cox if ((r = tty_ldisc_open(tty, disc)) < 0) 5138a8dabf2SAlan Cox tty_ldisc_put(disc); 5148a8dabf2SAlan Cox return r; 5158a8dabf2SAlan Cox } 5168a8dabf2SAlan Cox 5178a8dabf2SAlan Cox /** 518a8983d01SGreg Kroah-Hartman * tty_ldisc_restore - helper for tty ldisc change 519a8983d01SGreg Kroah-Hartman * @tty: tty to recover 520a8983d01SGreg Kroah-Hartman * @old: previous ldisc 521a8983d01SGreg Kroah-Hartman * 522a8983d01SGreg Kroah-Hartman * Restore the previous line discipline or N_TTY when a line discipline 523a8983d01SGreg Kroah-Hartman * change fails due to an open error 524a8983d01SGreg Kroah-Hartman */ 525a8983d01SGreg Kroah-Hartman 526a8983d01SGreg Kroah-Hartman static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) 527a8983d01SGreg Kroah-Hartman { 528a8983d01SGreg Kroah-Hartman /* There is an outstanding reference here so this is safe */ 529598c2d41STetsuo Handa if (tty_ldisc_failto(tty, old->ops->num) < 0) { 530598c2d41STetsuo Handa const char *name = tty_name(tty); 531598c2d41STetsuo Handa 532598c2d41STetsuo Handa pr_warn("Falling back ldisc for %s.\n", name); 5338a8dabf2SAlan Cox /* The traditional behaviour is to fall back to N_TTY, we 5348a8dabf2SAlan Cox want to avoid falling back to N_NULL unless we have no 5358a8dabf2SAlan Cox choice to avoid the risk of breaking anything */ 5368a8dabf2SAlan Cox if (tty_ldisc_failto(tty, N_TTY) < 0 && 5378a8dabf2SAlan Cox tty_ldisc_failto(tty, N_NULL) < 0) 538598c2d41STetsuo Handa panic("Couldn't open N_NULL ldisc for %s.", name); 539a8983d01SGreg Kroah-Hartman } 540a8983d01SGreg Kroah-Hartman } 541a8983d01SGreg Kroah-Hartman 542a8983d01SGreg Kroah-Hartman /** 54396fd7ce5SGreg Kroah-Hartman * tty_set_ldisc - set line discipline 54496fd7ce5SGreg Kroah-Hartman * @tty: the terminal to set 545fa441954SJiri Slaby * @disc: the line discipline number 54696fd7ce5SGreg Kroah-Hartman * 54796fd7ce5SGreg Kroah-Hartman * Set the discipline of a tty line. Must be called from a process 54896fd7ce5SGreg Kroah-Hartman * context. The ldisc change logic has to protect itself against any 54996fd7ce5SGreg Kroah-Hartman * overlapping ldisc change (including on the other end of pty pairs), 55096fd7ce5SGreg Kroah-Hartman * the close of one side of a tty/pty pair, and eventually hangup. 55196fd7ce5SGreg Kroah-Hartman */ 55296fd7ce5SGreg Kroah-Hartman 553c12da96fSPeter Hurley int tty_set_ldisc(struct tty_struct *tty, int disc) 55496fd7ce5SGreg Kroah-Hartman { 555a8983d01SGreg Kroah-Hartman int retval; 556a8983d01SGreg Kroah-Hartman struct tty_ldisc *old_ldisc, *new_ldisc; 557a8983d01SGreg Kroah-Hartman 558a8983d01SGreg Kroah-Hartman new_ldisc = tty_ldisc_get(tty, disc); 559a8983d01SGreg Kroah-Hartman if (IS_ERR(new_ldisc)) 560a8983d01SGreg Kroah-Hartman return PTR_ERR(new_ldisc); 56196fd7ce5SGreg Kroah-Hartman 562c8483bc9SPeter Hurley tty_lock(tty); 563276a661aSPeter Hurley retval = tty_ldisc_lock(tty, 5 * HZ); 56463d8cb3fSPeter Hurley if (retval) 56563d8cb3fSPeter Hurley goto err; 56696fd7ce5SGreg Kroah-Hartman 567a570a49aSPeter Hurley if (!tty->ldisc) { 568a570a49aSPeter Hurley retval = -EIO; 569a570a49aSPeter Hurley goto out; 570a570a49aSPeter Hurley } 571a570a49aSPeter Hurley 57263d8cb3fSPeter Hurley /* Check the no-op case */ 573a8983d01SGreg Kroah-Hartman if (tty->ldisc->ops->num == disc) 57463d8cb3fSPeter Hurley goto out; 57596fd7ce5SGreg Kroah-Hartman 57663d8cb3fSPeter Hurley if (test_bit(TTY_HUPPED, &tty->flags)) { 57763d8cb3fSPeter Hurley /* We were raced by hangup */ 57863d8cb3fSPeter Hurley retval = -EIO; 57963d8cb3fSPeter Hurley goto out; 58096fd7ce5SGreg Kroah-Hartman } 58196fd7ce5SGreg Kroah-Hartman 582a8983d01SGreg Kroah-Hartman old_ldisc = tty->ldisc; 583a8983d01SGreg Kroah-Hartman 584a8983d01SGreg Kroah-Hartman /* Shutdown the old discipline. */ 585a8983d01SGreg Kroah-Hartman tty_ldisc_close(tty, old_ldisc); 586a8983d01SGreg Kroah-Hartman 587a8983d01SGreg Kroah-Hartman /* Now set up the new line discipline. */ 588a8983d01SGreg Kroah-Hartman tty->ldisc = new_ldisc; 589a8983d01SGreg Kroah-Hartman tty_set_termios_ldisc(tty, disc); 590a8983d01SGreg Kroah-Hartman 591a8983d01SGreg Kroah-Hartman retval = tty_ldisc_open(tty, new_ldisc); 59296fd7ce5SGreg Kroah-Hartman if (retval < 0) { 59396fd7ce5SGreg Kroah-Hartman /* Back to the old one or N_TTY if we can't */ 594a8983d01SGreg Kroah-Hartman tty_ldisc_put(new_ldisc); 595a8983d01SGreg Kroah-Hartman tty_ldisc_restore(tty, old_ldisc); 59696fd7ce5SGreg Kroah-Hartman } 59796fd7ce5SGreg Kroah-Hartman 598a8983d01SGreg Kroah-Hartman if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { 5999191aaaaSPeter Hurley down_read(&tty->termios_rwsem); 60096fd7ce5SGreg Kroah-Hartman tty->ops->set_ldisc(tty); 6019191aaaaSPeter Hurley up_read(&tty->termios_rwsem); 6029191aaaaSPeter Hurley } 60396fd7ce5SGreg Kroah-Hartman 604a8983d01SGreg Kroah-Hartman /* At this point we hold a reference to the new ldisc and a 605a8983d01SGreg Kroah-Hartman reference to the old ldisc, or we hold two references to 606a8983d01SGreg Kroah-Hartman the old ldisc (if it was restored as part of error cleanup 607a8983d01SGreg Kroah-Hartman above). In either case, releasing a single reference from 608a8983d01SGreg Kroah-Hartman the old ldisc is correct. */ 609a8983d01SGreg Kroah-Hartman new_ldisc = old_ldisc; 61063d8cb3fSPeter Hurley out: 611276a661aSPeter Hurley tty_ldisc_unlock(tty); 61296fd7ce5SGreg Kroah-Hartman 61396fd7ce5SGreg Kroah-Hartman /* Restart the work queue in case no characters kick it off. Safe if 61496fd7ce5SGreg Kroah-Hartman already running */ 61517a69219SPeter Hurley tty_buffer_restart_work(tty->port); 61663d8cb3fSPeter Hurley err: 617a8983d01SGreg Kroah-Hartman tty_ldisc_put(new_ldisc); /* drop the extra reference */ 61889c8d91eSAlan Cox tty_unlock(tty); 61996fd7ce5SGreg Kroah-Hartman return retval; 62096fd7ce5SGreg Kroah-Hartman } 6211ab92da3SOkash Khawaja EXPORT_SYMBOL_GPL(tty_set_ldisc); 62296fd7ce5SGreg Kroah-Hartman 62396fd7ce5SGreg Kroah-Hartman /** 6246ffeb4b2SPeter Hurley * tty_ldisc_kill - teardown ldisc 6256ffeb4b2SPeter Hurley * @tty: tty being released 6266ffeb4b2SPeter Hurley * 6276ffeb4b2SPeter Hurley * Perform final close of the ldisc and reset tty->ldisc 6286ffeb4b2SPeter Hurley */ 6296ffeb4b2SPeter Hurley static void tty_ldisc_kill(struct tty_struct *tty) 6306ffeb4b2SPeter Hurley { 6319ffbe8acSNikolay Borisov lockdep_assert_held_write(&tty->ldisc_sem); 6326ffeb4b2SPeter Hurley if (!tty->ldisc) 6336ffeb4b2SPeter Hurley return; 6346ffeb4b2SPeter Hurley /* 6356ffeb4b2SPeter Hurley * Now kill off the ldisc 6366ffeb4b2SPeter Hurley */ 6376ffeb4b2SPeter Hurley tty_ldisc_close(tty, tty->ldisc); 6386ffeb4b2SPeter Hurley tty_ldisc_put(tty->ldisc); 6396ffeb4b2SPeter Hurley /* Force an oops if we mess this up */ 6406ffeb4b2SPeter Hurley tty->ldisc = NULL; 6416ffeb4b2SPeter Hurley } 6426ffeb4b2SPeter Hurley 6436ffeb4b2SPeter Hurley /** 64496fd7ce5SGreg Kroah-Hartman * tty_reset_termios - reset terminal state 64596fd7ce5SGreg Kroah-Hartman * @tty: tty to reset 64696fd7ce5SGreg Kroah-Hartman * 64796fd7ce5SGreg Kroah-Hartman * Restore a terminal to the driver default state. 64896fd7ce5SGreg Kroah-Hartman */ 64996fd7ce5SGreg Kroah-Hartman 65096fd7ce5SGreg Kroah-Hartman static void tty_reset_termios(struct tty_struct *tty) 65196fd7ce5SGreg Kroah-Hartman { 6526a1c0680SPeter Hurley down_write(&tty->termios_rwsem); 653adc8d746SAlan Cox tty->termios = tty->driver->init_termios; 654adc8d746SAlan Cox tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios); 655adc8d746SAlan Cox tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios); 6566a1c0680SPeter Hurley up_write(&tty->termios_rwsem); 65796fd7ce5SGreg Kroah-Hartman } 65896fd7ce5SGreg Kroah-Hartman 65996fd7ce5SGreg Kroah-Hartman 66096fd7ce5SGreg Kroah-Hartman /** 66196fd7ce5SGreg Kroah-Hartman * tty_ldisc_reinit - reinitialise the tty ldisc 66296fd7ce5SGreg Kroah-Hartman * @tty: tty to reinit 663c12da96fSPeter Hurley * @disc: line discipline to reinitialize 66496fd7ce5SGreg Kroah-Hartman * 6657896f30dSPeter Hurley * Completely reinitialize the line discipline state, by closing the 666892d1fa7SPeter Hurley * current instance, if there is one, and opening a new instance. If 667892d1fa7SPeter Hurley * an error occurs opening the new non-N_TTY instance, the instance 668892d1fa7SPeter Hurley * is dropped and tty->ldisc reset to NULL. The caller can then retry 669892d1fa7SPeter Hurley * with N_TTY instead. 6707896f30dSPeter Hurley * 6717896f30dSPeter Hurley * Returns 0 if successful, otherwise error code < 0 67296fd7ce5SGreg Kroah-Hartman */ 67396fd7ce5SGreg Kroah-Hartman 674892d1fa7SPeter Hurley int tty_ldisc_reinit(struct tty_struct *tty, int disc) 67596fd7ce5SGreg Kroah-Hartman { 6767896f30dSPeter Hurley struct tty_ldisc *ld; 6777896f30dSPeter Hurley int retval; 6781c95ba1eSPhilippe Rétornaz 6799ffbe8acSNikolay Borisov lockdep_assert_held_write(&tty->ldisc_sem); 6807896f30dSPeter Hurley ld = tty_ldisc_get(tty, disc); 681a8983d01SGreg Kroah-Hartman if (IS_ERR(ld)) { 682a8983d01SGreg Kroah-Hartman BUG_ON(disc == N_TTY); 6837896f30dSPeter Hurley return PTR_ERR(ld); 684a8983d01SGreg Kroah-Hartman } 68596fd7ce5SGreg Kroah-Hartman 6867896f30dSPeter Hurley if (tty->ldisc) { 68796fd7ce5SGreg Kroah-Hartman tty_ldisc_close(tty, tty->ldisc); 68896fd7ce5SGreg Kroah-Hartman tty_ldisc_put(tty->ldisc); 6897896f30dSPeter Hurley } 6907896f30dSPeter Hurley 6917896f30dSPeter Hurley /* switch the line discipline */ 692f4807045SPeter Hurley tty->ldisc = ld; 693c12da96fSPeter Hurley tty_set_termios_ldisc(tty, disc); 6947896f30dSPeter Hurley retval = tty_ldisc_open(tty, tty->ldisc); 6957896f30dSPeter Hurley if (retval) { 6967896f30dSPeter Hurley tty_ldisc_put(tty->ldisc); 6977896f30dSPeter Hurley tty->ldisc = NULL; 6987896f30dSPeter Hurley } 6997896f30dSPeter Hurley return retval; 70096fd7ce5SGreg Kroah-Hartman } 70196fd7ce5SGreg Kroah-Hartman 70296fd7ce5SGreg Kroah-Hartman /** 70396fd7ce5SGreg Kroah-Hartman * tty_ldisc_hangup - hangup ldisc reset 70496fd7ce5SGreg Kroah-Hartman * @tty: tty being hung up 70596fd7ce5SGreg Kroah-Hartman * 70696fd7ce5SGreg Kroah-Hartman * Some tty devices reset their termios when they receive a hangup 70796fd7ce5SGreg Kroah-Hartman * event. In that situation we must also switch back to N_TTY properly 70896fd7ce5SGreg Kroah-Hartman * before we reset the termios data. 70996fd7ce5SGreg Kroah-Hartman * 71096fd7ce5SGreg Kroah-Hartman * Locking: We can take the ldisc mutex as the rest of the code is 71196fd7ce5SGreg Kroah-Hartman * careful to allow for this. 71296fd7ce5SGreg Kroah-Hartman * 71396fd7ce5SGreg Kroah-Hartman * In the pty pair case this occurs in the close() path of the 71496fd7ce5SGreg Kroah-Hartman * tty itself so we must be careful about locking rules. 71596fd7ce5SGreg Kroah-Hartman */ 71696fd7ce5SGreg Kroah-Hartman 717892d1fa7SPeter Hurley void tty_ldisc_hangup(struct tty_struct *tty, bool reinit) 71896fd7ce5SGreg Kroah-Hartman { 71996fd7ce5SGreg Kroah-Hartman struct tty_ldisc *ld; 72096fd7ce5SGreg Kroah-Hartman 721a570a49aSPeter Hurley tty_ldisc_debug(tty, "%p: hangup\n", tty->ldisc); 722fc575ee6SPeter Hurley 72396fd7ce5SGreg Kroah-Hartman ld = tty_ldisc_ref(tty); 72496fd7ce5SGreg Kroah-Hartman if (ld != NULL) { 72596fd7ce5SGreg Kroah-Hartman if (ld->ops->flush_buffer) 72696fd7ce5SGreg Kroah-Hartman ld->ops->flush_buffer(tty); 72796fd7ce5SGreg Kroah-Hartman tty_driver_flush_buffer(tty); 72896fd7ce5SGreg Kroah-Hartman if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) && 72996fd7ce5SGreg Kroah-Hartman ld->ops->write_wakeup) 73096fd7ce5SGreg Kroah-Hartman ld->ops->write_wakeup(tty); 73196fd7ce5SGreg Kroah-Hartman if (ld->ops->hangup) 73296fd7ce5SGreg Kroah-Hartman ld->ops->hangup(tty); 73396fd7ce5SGreg Kroah-Hartman tty_ldisc_deref(ld); 73496fd7ce5SGreg Kroah-Hartman } 73536697529SPeter Hurley 736a9a08845SLinus Torvalds wake_up_interruptible_poll(&tty->write_wait, EPOLLOUT); 737a9a08845SLinus Torvalds wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); 73836697529SPeter Hurley 73996fd7ce5SGreg Kroah-Hartman /* 74096fd7ce5SGreg Kroah-Hartman * Shutdown the current line discipline, and reset it to 74196fd7ce5SGreg Kroah-Hartman * N_TTY if need be. 74296fd7ce5SGreg Kroah-Hartman * 74396fd7ce5SGreg Kroah-Hartman * Avoid racing set_ldisc or tty_ldisc_release 74496fd7ce5SGreg Kroah-Hartman */ 745fae76e9aSPeter Hurley tty_ldisc_lock(tty, MAX_SCHEDULE_TIMEOUT); 74696fd7ce5SGreg Kroah-Hartman 747892d1fa7SPeter Hurley if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) 74896fd7ce5SGreg Kroah-Hartman tty_reset_termios(tty); 749fc575ee6SPeter Hurley 750892d1fa7SPeter Hurley if (tty->ldisc) { 751892d1fa7SPeter Hurley if (reinit) { 752e65c62b1SJohannes Weiner if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && 753e65c62b1SJohannes Weiner tty_ldisc_reinit(tty, N_TTY) < 0) 754e65c62b1SJohannes Weiner WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); 755892d1fa7SPeter Hurley } else 756892d1fa7SPeter Hurley tty_ldisc_kill(tty); 757892d1fa7SPeter Hurley } 758892d1fa7SPeter Hurley tty_ldisc_unlock(tty); 75996fd7ce5SGreg Kroah-Hartman } 76096fd7ce5SGreg Kroah-Hartman 76196fd7ce5SGreg Kroah-Hartman /** 76296fd7ce5SGreg Kroah-Hartman * tty_ldisc_setup - open line discipline 76396fd7ce5SGreg Kroah-Hartman * @tty: tty being shut down 76496fd7ce5SGreg Kroah-Hartman * @o_tty: pair tty for pty/tty pairs 76596fd7ce5SGreg Kroah-Hartman * 76696fd7ce5SGreg Kroah-Hartman * Called during the initial open of a tty/pty pair in order to set up the 76796fd7ce5SGreg Kroah-Hartman * line disciplines and bind them to the tty. This has no locking issues 76896fd7ce5SGreg Kroah-Hartman * as the device isn't yet active. 76996fd7ce5SGreg Kroah-Hartman */ 77096fd7ce5SGreg Kroah-Hartman 77196fd7ce5SGreg Kroah-Hartman int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty) 77296fd7ce5SGreg Kroah-Hartman { 7739de2a7ceSPeter Hurley int retval = tty_ldisc_open(tty, tty->ldisc); 77496fd7ce5SGreg Kroah-Hartman if (retval) 77596fd7ce5SGreg Kroah-Hartman return retval; 77696fd7ce5SGreg Kroah-Hartman 77796fd7ce5SGreg Kroah-Hartman if (o_tty) { 778110b8928SDmitry Safonov /* 779110b8928SDmitry Safonov * Called without o_tty->ldisc_sem held, as o_tty has been 780110b8928SDmitry Safonov * just allocated and no one has a reference to it. 781110b8928SDmitry Safonov */ 78296fd7ce5SGreg Kroah-Hartman retval = tty_ldisc_open(o_tty, o_tty->ldisc); 78396fd7ce5SGreg Kroah-Hartman if (retval) { 7849de2a7ceSPeter Hurley tty_ldisc_close(tty, tty->ldisc); 78596fd7ce5SGreg Kroah-Hartman return retval; 78696fd7ce5SGreg Kroah-Hartman } 78796fd7ce5SGreg Kroah-Hartman } 78896fd7ce5SGreg Kroah-Hartman return 0; 78996fd7ce5SGreg Kroah-Hartman } 79089c8d91eSAlan Cox 79196fd7ce5SGreg Kroah-Hartman /** 79296fd7ce5SGreg Kroah-Hartman * tty_ldisc_release - release line discipline 79362462aefSPeter Hurley * @tty: tty being shut down (or one end of pty pair) 79496fd7ce5SGreg Kroah-Hartman * 79562462aefSPeter Hurley * Called during the final close of a tty or a pty pair in order to shut 7965b6e6832SPeter Hurley * down the line discpline layer. On exit, each tty's ldisc is NULL. 79796fd7ce5SGreg Kroah-Hartman */ 79896fd7ce5SGreg Kroah-Hartman 79962462aefSPeter Hurley void tty_ldisc_release(struct tty_struct *tty) 80096fd7ce5SGreg Kroah-Hartman { 80162462aefSPeter Hurley struct tty_struct *o_tty = tty->link; 80262462aefSPeter Hurley 80396fd7ce5SGreg Kroah-Hartman /* 804a2965b7bSPeter Hurley * Shutdown this line discipline. As this is the final close, 805a2965b7bSPeter Hurley * it does not race with the set_ldisc code path. 80696fd7ce5SGreg Kroah-Hartman */ 80796fd7ce5SGreg Kroah-Hartman 80836697529SPeter Hurley tty_ldisc_lock_pair(tty, o_tty); 80989c8d91eSAlan Cox tty_ldisc_kill(tty); 81089c8d91eSAlan Cox if (o_tty) 81189c8d91eSAlan Cox tty_ldisc_kill(o_tty); 81236697529SPeter Hurley tty_ldisc_unlock_pair(tty, o_tty); 81336697529SPeter Hurley 81496fd7ce5SGreg Kroah-Hartman /* And the memory resources remaining (buffers, termios) will be 81596fd7ce5SGreg Kroah-Hartman disposed of when the kref hits zero */ 816fc575ee6SPeter Hurley 817fb6edc91SPeter Hurley tty_ldisc_debug(tty, "released\n"); 81896fd7ce5SGreg Kroah-Hartman } 8191ab92da3SOkash Khawaja EXPORT_SYMBOL_GPL(tty_ldisc_release); 82096fd7ce5SGreg Kroah-Hartman 82196fd7ce5SGreg Kroah-Hartman /** 82296fd7ce5SGreg Kroah-Hartman * tty_ldisc_init - ldisc setup for new tty 82396fd7ce5SGreg Kroah-Hartman * @tty: tty being allocated 82496fd7ce5SGreg Kroah-Hartman * 82596fd7ce5SGreg Kroah-Hartman * Set up the line discipline objects for a newly allocated tty. Note that 82696fd7ce5SGreg Kroah-Hartman * the tty structure is not completely set up when this call is made. 82796fd7ce5SGreg Kroah-Hartman */ 82896fd7ce5SGreg Kroah-Hartman 829903f9db1STetsuo Handa int tty_ldisc_init(struct tty_struct *tty) 83096fd7ce5SGreg Kroah-Hartman { 83136697529SPeter Hurley struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); 83296fd7ce5SGreg Kroah-Hartman if (IS_ERR(ld)) 833903f9db1STetsuo Handa return PTR_ERR(ld); 834f4807045SPeter Hurley tty->ldisc = ld; 835903f9db1STetsuo Handa return 0; 83696fd7ce5SGreg Kroah-Hartman } 83796fd7ce5SGreg Kroah-Hartman 8386716671dSJiri Slaby /** 839c8b710b3SPeter Hurley * tty_ldisc_deinit - ldisc cleanup for new tty 8406716671dSJiri Slaby * @tty: tty that was allocated recently 8416716671dSJiri Slaby * 8426716671dSJiri Slaby * The tty structure must not becompletely set up (tty_ldisc_setup) when 8436716671dSJiri Slaby * this call is made. 8446716671dSJiri Slaby */ 8456716671dSJiri Slaby void tty_ldisc_deinit(struct tty_struct *tty) 8466716671dSJiri Slaby { 847110b8928SDmitry Safonov /* no ldisc_sem, tty is being destroyed */ 848c8b710b3SPeter Hurley if (tty->ldisc) 849ebc9baedSPeter Hurley tty_ldisc_put(tty->ldisc); 850f4807045SPeter Hurley tty->ldisc = NULL; 8516716671dSJiri Slaby } 8527c0cca7cSGreg Kroah-Hartman 8537c0cca7cSGreg Kroah-Hartman static struct ctl_table tty_table[] = { 8547c0cca7cSGreg Kroah-Hartman { 8557c0cca7cSGreg Kroah-Hartman .procname = "ldisc_autoload", 8567c0cca7cSGreg Kroah-Hartman .data = &tty_ldisc_autoload, 8577c0cca7cSGreg Kroah-Hartman .maxlen = sizeof(tty_ldisc_autoload), 8587c0cca7cSGreg Kroah-Hartman .mode = 0644, 8597c0cca7cSGreg Kroah-Hartman .proc_handler = proc_dointvec, 860eec4844fSMatteo Croce .extra1 = SYSCTL_ZERO, 861eec4844fSMatteo Croce .extra2 = SYSCTL_ONE, 8627c0cca7cSGreg Kroah-Hartman }, 8637c0cca7cSGreg Kroah-Hartman { } 8647c0cca7cSGreg Kroah-Hartman }; 8657c0cca7cSGreg Kroah-Hartman 8667c0cca7cSGreg Kroah-Hartman static struct ctl_table tty_dir_table[] = { 8677c0cca7cSGreg Kroah-Hartman { 8687c0cca7cSGreg Kroah-Hartman .procname = "tty", 8697c0cca7cSGreg Kroah-Hartman .mode = 0555, 8707c0cca7cSGreg Kroah-Hartman .child = tty_table, 8717c0cca7cSGreg Kroah-Hartman }, 8727c0cca7cSGreg Kroah-Hartman { } 8737c0cca7cSGreg Kroah-Hartman }; 8747c0cca7cSGreg Kroah-Hartman 8757c0cca7cSGreg Kroah-Hartman static struct ctl_table tty_root_table[] = { 8767c0cca7cSGreg Kroah-Hartman { 8777c0cca7cSGreg Kroah-Hartman .procname = "dev", 8787c0cca7cSGreg Kroah-Hartman .mode = 0555, 8797c0cca7cSGreg Kroah-Hartman .child = tty_dir_table, 8807c0cca7cSGreg Kroah-Hartman }, 8817c0cca7cSGreg Kroah-Hartman { } 8827c0cca7cSGreg Kroah-Hartman }; 8837c0cca7cSGreg Kroah-Hartman 8847c0cca7cSGreg Kroah-Hartman void tty_sysctl_init(void) 8857c0cca7cSGreg Kroah-Hartman { 8867c0cca7cSGreg Kroah-Hartman register_sysctl_table(tty_root_table); 8877c0cca7cSGreg Kroah-Hartman } 888