#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 __lockfunctty_ldisc_lock(struct tty_struct *tty, unsigned long timeout){ return ldsem_down_write(&tty->ldisc_sem, timeout);} static inline int __lockfunctty_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 __lockfunctty_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 __lockfunctty_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_rwsem */ static void tty_set_termios_ldisc(struct tty_struct *tty, int num){ down_write(&tty->termios_rwsem); tty->termios.c_line = num; up_write(&tty->termios_rwsem);} /** * 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 "Lines 1–500 of 828. 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#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_rwsem */ static void tty_set_termios_ldisc(struct tty_struct *tty, int num) { down_write(&tty->termios_rwsem); tty->termios.c_line = num; up_write(&tty->termios_rwsem); } /** * 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 "