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855 lines
21 KiB
855 lines
21 KiB
// SPDX-License-Identifier: GPL-2.0 |
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#include <linux/types.h> |
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#include <linux/errno.h> |
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#include <linux/kmod.h> |
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#include <linux/sched.h> |
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#include <linux/interrupt.h> |
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#include <linux/tty.h> |
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#include <linux/tty_driver.h> |
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#include <linux/file.h> |
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#include <linux/mm.h> |
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#include <linux/string.h> |
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#include <linux/slab.h> |
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#include <linux/poll.h> |
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#include <linux/proc_fs.h> |
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#include <linux/module.h> |
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#include <linux/device.h> |
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#include <linux/wait.h> |
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#include <linux/bitops.h> |
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#include <linux/seq_file.h> |
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#include <linux/uaccess.h> |
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#include <linux/ratelimit.h> |
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#include "tty.h" |
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#undef LDISC_DEBUG_HANGUP |
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#ifdef LDISC_DEBUG_HANGUP |
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#define tty_ldisc_debug(tty, f, args...) tty_debug(tty, f, ##args) |
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#else |
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#define tty_ldisc_debug(tty, f, args...) |
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#endif |
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/* lockdep nested classes for tty->ldisc_sem */ |
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enum { |
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LDISC_SEM_NORMAL, |
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LDISC_SEM_OTHER, |
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}; |
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|
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/* |
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* This guards the refcounted line discipline lists. The lock |
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* must be taken with irqs off because there are hangup path |
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* callers who will do ldisc lookups and cannot sleep. |
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*/ |
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static DEFINE_RAW_SPINLOCK(tty_ldiscs_lock); |
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/* Line disc dispatch table */ |
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static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS]; |
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/** |
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* tty_register_ldisc - install a line discipline |
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* @new_ldisc: pointer to the ldisc object |
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* |
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* Installs a new line discipline into the kernel. The discipline is set up as |
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* unreferenced and then made available to the kernel from this point onwards. |
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* |
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* Locking: takes %tty_ldiscs_lock to guard against ldisc races |
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*/ |
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int tty_register_ldisc(struct tty_ldisc_ops *new_ldisc) |
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{ |
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unsigned long flags; |
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int ret = 0; |
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if (new_ldisc->num < N_TTY || new_ldisc->num >= NR_LDISCS) |
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return -EINVAL; |
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
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tty_ldiscs[new_ldisc->num] = new_ldisc; |
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
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return ret; |
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} |
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EXPORT_SYMBOL(tty_register_ldisc); |
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/** |
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* tty_unregister_ldisc - unload a line discipline |
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* @ldisc: ldisc number |
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* |
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* Remove a line discipline from the kernel providing it is not currently in |
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* use. |
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* |
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* Locking: takes %tty_ldiscs_lock to guard against ldisc races |
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*/ |
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void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc) |
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{ |
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unsigned long flags; |
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
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tty_ldiscs[ldisc->num] = NULL; |
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
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} |
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EXPORT_SYMBOL(tty_unregister_ldisc); |
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static struct tty_ldisc_ops *get_ldops(int disc) |
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{ |
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unsigned long flags; |
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struct tty_ldisc_ops *ldops, *ret; |
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
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ret = ERR_PTR(-EINVAL); |
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ldops = tty_ldiscs[disc]; |
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if (ldops) { |
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ret = ERR_PTR(-EAGAIN); |
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if (try_module_get(ldops->owner)) |
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ret = ldops; |
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} |
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
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return ret; |
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} |
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static void put_ldops(struct tty_ldisc_ops *ldops) |
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{ |
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unsigned long flags; |
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raw_spin_lock_irqsave(&tty_ldiscs_lock, flags); |
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module_put(ldops->owner); |
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raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags); |
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} |
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static int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD); |
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/** |
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* tty_ldisc_get - take a reference to an ldisc |
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* @tty: tty device |
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* @disc: ldisc number |
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* |
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* Takes a reference to a line discipline. Deals with refcounts and module |
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* locking counts. If the discipline is not available, its module loaded, if |
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* possible. |
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* |
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* Returns: |
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* * -%EINVAL if the discipline index is not [%N_TTY .. %NR_LDISCS] or if the |
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* discipline is not registered |
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* * -%EAGAIN if request_module() failed to load or register the discipline |
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* * -%ENOMEM if allocation failure |
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* * Otherwise, returns a pointer to the discipline and bumps the ref count |
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* |
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* Locking: takes %tty_ldiscs_lock to guard against ldisc races |
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*/ |
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static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) |
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{ |
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struct tty_ldisc *ld; |
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struct tty_ldisc_ops *ldops; |
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if (disc < N_TTY || disc >= NR_LDISCS) |
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return ERR_PTR(-EINVAL); |
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/* |
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* Get the ldisc ops - we may need to request them to be loaded |
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* dynamically and try again. |
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*/ |
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ldops = get_ldops(disc); |
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if (IS_ERR(ldops)) { |
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if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload) |
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return ERR_PTR(-EPERM); |
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request_module("tty-ldisc-%d", disc); |
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ldops = get_ldops(disc); |
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if (IS_ERR(ldops)) |
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return ERR_CAST(ldops); |
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} |
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/* |
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* There is no way to handle allocation failure of only 16 bytes. |
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* Let's simplify error handling and save more memory. |
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*/ |
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ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL); |
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ld->ops = ldops; |
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ld->tty = tty; |
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return ld; |
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} |
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/** |
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* tty_ldisc_put - release the ldisc |
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* @ld: lisdsc to release |
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* |
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* Complement of tty_ldisc_get(). |
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*/ |
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static void tty_ldisc_put(struct tty_ldisc *ld) |
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{ |
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if (WARN_ON_ONCE(!ld)) |
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return; |
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put_ldops(ld->ops); |
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kfree(ld); |
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} |
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static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) |
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{ |
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return (*pos < NR_LDISCS) ? pos : NULL; |
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} |
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static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) |
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{ |
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(*pos)++; |
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return (*pos < NR_LDISCS) ? pos : NULL; |
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} |
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static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) |
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{ |
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} |
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static int tty_ldiscs_seq_show(struct seq_file *m, void *v) |
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{ |
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int i = *(loff_t *)v; |
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struct tty_ldisc_ops *ldops; |
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ldops = get_ldops(i); |
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if (IS_ERR(ldops)) |
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return 0; |
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seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i); |
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put_ldops(ldops); |
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return 0; |
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} |
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const struct seq_operations tty_ldiscs_seq_ops = { |
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.start = tty_ldiscs_seq_start, |
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.next = tty_ldiscs_seq_next, |
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.stop = tty_ldiscs_seq_stop, |
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.show = tty_ldiscs_seq_show, |
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}; |
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/** |
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* tty_ldisc_ref_wait - wait for the tty ldisc |
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* @tty: tty device |
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* |
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* Dereference the line discipline for the terminal and take a reference to it. |
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* If the line discipline is in flux then wait patiently until it changes. |
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* |
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* Returns: %NULL if the tty has been hungup and not re-opened with a new file |
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* descriptor, otherwise valid ldisc reference |
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* |
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* Note 1: Must not be called from an IRQ/timer context. The caller must also |
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* be careful not to hold other locks that will deadlock against a discipline |
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* change, such as an existing ldisc reference (which we check for). |
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* |
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* Note 2: a file_operations routine (read/poll/write) should use this function |
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* to wait for any ldisc lifetime events to finish. |
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*/ |
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struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) |
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{ |
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struct tty_ldisc *ld; |
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ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT); |
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ld = tty->ldisc; |
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if (!ld) |
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ldsem_up_read(&tty->ldisc_sem); |
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return ld; |
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} |
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EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait); |
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/** |
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* tty_ldisc_ref - get the tty ldisc |
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* @tty: tty device |
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* |
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* Dereference the line discipline for the terminal and take a reference to it. |
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* If the line discipline is in flux then return %NULL. Can be called from IRQ |
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* and timer functions. |
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*/ |
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struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty) |
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{ |
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struct tty_ldisc *ld = NULL; |
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if (ldsem_down_read_trylock(&tty->ldisc_sem)) { |
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ld = tty->ldisc; |
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if (!ld) |
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ldsem_up_read(&tty->ldisc_sem); |
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} |
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return ld; |
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} |
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EXPORT_SYMBOL_GPL(tty_ldisc_ref); |
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/** |
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* tty_ldisc_deref - free a tty ldisc reference |
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* @ld: reference to free up |
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* |
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* Undoes the effect of tty_ldisc_ref() or tty_ldisc_ref_wait(). May be called |
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* in IRQ context. |
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*/ |
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void tty_ldisc_deref(struct tty_ldisc *ld) |
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{ |
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ldsem_up_read(&ld->tty->ldisc_sem); |
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} |
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EXPORT_SYMBOL_GPL(tty_ldisc_deref); |
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static inline int |
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__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
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{ |
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return ldsem_down_write(&tty->ldisc_sem, timeout); |
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} |
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static inline int |
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__tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) |
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{ |
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return ldsem_down_write_nested(&tty->ldisc_sem, |
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LDISC_SEM_OTHER, timeout); |
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} |
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static inline void __tty_ldisc_unlock(struct tty_struct *tty) |
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{ |
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ldsem_up_write(&tty->ldisc_sem); |
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} |
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int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) |
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{ |
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int ret; |
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/* Kindly asking blocked readers to release the read side */ |
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set_bit(TTY_LDISC_CHANGING, &tty->flags); |
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wake_up_interruptible_all(&tty->read_wait); |
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wake_up_interruptible_all(&tty->write_wait); |
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ret = __tty_ldisc_lock(tty, timeout); |
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if (!ret) |
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return -EBUSY; |
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set_bit(TTY_LDISC_HALTED, &tty->flags); |
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return 0; |
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} |
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void tty_ldisc_unlock(struct tty_struct *tty) |
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{ |
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clear_bit(TTY_LDISC_HALTED, &tty->flags); |
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/* Can be cleared here - ldisc_unlock will wake up writers firstly */ |
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clear_bit(TTY_LDISC_CHANGING, &tty->flags); |
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__tty_ldisc_unlock(tty); |
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} |
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static int |
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tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, |
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unsigned long timeout) |
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{ |
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int ret; |
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if (tty < tty2) { |
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ret = __tty_ldisc_lock(tty, timeout); |
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if (ret) { |
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ret = __tty_ldisc_lock_nested(tty2, timeout); |
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if (!ret) |
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__tty_ldisc_unlock(tty); |
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} |
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} else { |
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/* if this is possible, it has lots of implications */ |
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WARN_ON_ONCE(tty == tty2); |
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if (tty2 && tty != tty2) { |
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ret = __tty_ldisc_lock(tty2, timeout); |
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if (ret) { |
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ret = __tty_ldisc_lock_nested(tty, timeout); |
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if (!ret) |
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__tty_ldisc_unlock(tty2); |
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} |
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} else |
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ret = __tty_ldisc_lock(tty, timeout); |
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} |
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if (!ret) |
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return -EBUSY; |
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set_bit(TTY_LDISC_HALTED, &tty->flags); |
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if (tty2) |
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set_bit(TTY_LDISC_HALTED, &tty2->flags); |
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return 0; |
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} |
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static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) |
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{ |
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tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT); |
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} |
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static void tty_ldisc_unlock_pair(struct tty_struct *tty, |
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struct tty_struct *tty2) |
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{ |
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__tty_ldisc_unlock(tty); |
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if (tty2) |
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__tty_ldisc_unlock(tty2); |
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} |
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/** |
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* tty_ldisc_flush - flush line discipline queue |
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* @tty: tty to flush ldisc for |
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* |
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* Flush the line discipline queue (if any) and the tty flip buffers for this |
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* @tty. |
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*/ |
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void tty_ldisc_flush(struct tty_struct *tty) |
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{ |
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struct tty_ldisc *ld = tty_ldisc_ref(tty); |
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tty_buffer_flush(tty, ld); |
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if (ld) |
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tty_ldisc_deref(ld); |
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} |
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EXPORT_SYMBOL_GPL(tty_ldisc_flush); |
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/** |
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* tty_set_termios_ldisc - set ldisc field |
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* @tty: tty structure |
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* @disc: line discipline number |
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* |
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* This is probably overkill for real world processors but they are not on hot |
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* paths so a little discipline won't do any harm. |
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* |
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* The line discipline-related tty_struct fields are reset to prevent the ldisc |
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* driver from re-using stale information for the new ldisc instance. |
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* |
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* Locking: takes termios_rwsem |
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*/ |
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static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) |
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{ |
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down_write(&tty->termios_rwsem); |
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tty->termios.c_line = disc; |
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up_write(&tty->termios_rwsem); |
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tty->disc_data = NULL; |
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tty->receive_room = 0; |
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} |
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/** |
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* tty_ldisc_open - open a line discipline |
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* @tty: tty we are opening the ldisc on |
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* @ld: discipline to open |
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* |
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* A helper opening method. Also a convenient debugging and check point. |
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* |
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* Locking: always called with BTM already held. |
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*/ |
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static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld) |
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{ |
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WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags)); |
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if (ld->ops->open) { |
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int ret; |
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/* BTM here locks versus a hangup event */ |
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ret = ld->ops->open(tty); |
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if (ret) |
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clear_bit(TTY_LDISC_OPEN, &tty->flags); |
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tty_ldisc_debug(tty, "%p: opened\n", ld); |
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return ret; |
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} |
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return 0; |
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} |
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/** |
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* tty_ldisc_close - close a line discipline |
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* @tty: tty we are opening the ldisc on |
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* @ld: discipline to close |
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* |
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* A helper close method. Also a convenient debugging and check point. |
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*/ |
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static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld) |
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{ |
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lockdep_assert_held_write(&tty->ldisc_sem); |
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WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags)); |
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clear_bit(TTY_LDISC_OPEN, &tty->flags); |
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if (ld->ops->close) |
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ld->ops->close(tty); |
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tty_ldisc_debug(tty, "%p: closed\n", ld); |
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} |
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/** |
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* tty_ldisc_failto - helper for ldisc failback |
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* @tty: tty to open the ldisc on |
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* @ld: ldisc we are trying to fail back to |
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* |
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* Helper to try and recover a tty when switching back to the old ldisc fails |
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* and we need something attached. |
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*/ |
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static int tty_ldisc_failto(struct tty_struct *tty, int ld) |
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{ |
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struct tty_ldisc *disc = tty_ldisc_get(tty, ld); |
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int r; |
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lockdep_assert_held_write(&tty->ldisc_sem); |
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if (IS_ERR(disc)) |
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return PTR_ERR(disc); |
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tty->ldisc = disc; |
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tty_set_termios_ldisc(tty, ld); |
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r = tty_ldisc_open(tty, disc); |
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if (r < 0) |
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tty_ldisc_put(disc); |
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return r; |
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} |
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/** |
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* tty_ldisc_restore - helper for tty ldisc change |
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* @tty: tty to recover |
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* @old: previous ldisc |
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* |
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* Restore the previous line discipline or %N_TTY when a line discipline change |
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* fails due to an open error |
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*/ |
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static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old) |
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{ |
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/* There is an outstanding reference here so this is safe */ |
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if (tty_ldisc_failto(tty, old->ops->num) < 0) { |
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const char *name = tty_name(tty); |
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pr_warn("Falling back ldisc for %s.\n", name); |
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/* |
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* The traditional behaviour is to fall back to N_TTY, we |
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* want to avoid falling back to N_NULL unless we have no |
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* choice to avoid the risk of breaking anything |
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*/ |
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if (tty_ldisc_failto(tty, N_TTY) < 0 && |
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tty_ldisc_failto(tty, N_NULL) < 0) |
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panic("Couldn't open N_NULL ldisc for %s.", name); |
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} |
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} |
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/** |
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* tty_set_ldisc - set line discipline |
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* @tty: the terminal to set |
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* @disc: the line discipline number |
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* |
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* Set the discipline of a tty line. Must be called from a process context. The |
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* ldisc change logic has to protect itself against any overlapping ldisc |
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* change (including on the other end of pty pairs), the close of one side of a |
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* tty/pty pair, and eventually hangup. |
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*/ |
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int tty_set_ldisc(struct tty_struct *tty, int disc) |
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{ |
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int retval; |
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struct tty_ldisc *old_ldisc, *new_ldisc; |
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new_ldisc = tty_ldisc_get(tty, disc); |
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if (IS_ERR(new_ldisc)) |
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return PTR_ERR(new_ldisc); |
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tty_lock(tty); |
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retval = tty_ldisc_lock(tty, 5 * HZ); |
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if (retval) |
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goto err; |
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if (!tty->ldisc) { |
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retval = -EIO; |
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goto out; |
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} |
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/* Check the no-op case */ |
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if (tty->ldisc->ops->num == disc) |
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goto out; |
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if (test_bit(TTY_HUPPED, &tty->flags)) { |
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/* We were raced by hangup */ |
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retval = -EIO; |
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goto out; |
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} |
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old_ldisc = tty->ldisc; |
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|
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/* Shutdown the old discipline. */ |
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tty_ldisc_close(tty, old_ldisc); |
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|
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/* Now set up the new line discipline. */ |
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tty->ldisc = new_ldisc; |
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tty_set_termios_ldisc(tty, disc); |
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retval = tty_ldisc_open(tty, new_ldisc); |
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if (retval < 0) { |
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/* Back to the old one or N_TTY if we can't */ |
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tty_ldisc_put(new_ldisc); |
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tty_ldisc_restore(tty, old_ldisc); |
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} |
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|
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if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) { |
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down_read(&tty->termios_rwsem); |
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tty->ops->set_ldisc(tty); |
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up_read(&tty->termios_rwsem); |
|
} |
|
|
|
/* |
|
* At this point we hold a reference to the new ldisc and a |
|
* reference to the old ldisc, or we hold two references to |
|
* the old ldisc (if it was restored as part of error cleanup |
|
* above). In either case, releasing a single reference from |
|
* the old ldisc is correct. |
|
*/ |
|
new_ldisc = old_ldisc; |
|
out: |
|
tty_ldisc_unlock(tty); |
|
|
|
/* |
|
* Restart the work queue in case no characters kick it off. Safe if |
|
* already running |
|
*/ |
|
tty_buffer_restart_work(tty->port); |
|
err: |
|
tty_ldisc_put(new_ldisc); /* drop the extra reference */ |
|
tty_unlock(tty); |
|
return retval; |
|
} |
|
EXPORT_SYMBOL_GPL(tty_set_ldisc); |
|
|
|
/** |
|
* tty_ldisc_kill - teardown ldisc |
|
* @tty: tty being released |
|
* |
|
* Perform final close of the ldisc and reset @tty->ldisc |
|
*/ |
|
static void tty_ldisc_kill(struct tty_struct *tty) |
|
{ |
|
lockdep_assert_held_write(&tty->ldisc_sem); |
|
if (!tty->ldisc) |
|
return; |
|
/* |
|
* 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; |
|
} |
|
|
|
/** |
|
* 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) |
|
{ |
|
down_write(&tty->termios_rwsem); |
|
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); |
|
up_write(&tty->termios_rwsem); |
|
} |
|
|
|
|
|
/** |
|
* tty_ldisc_reinit - reinitialise the tty ldisc |
|
* @tty: tty to reinit |
|
* @disc: line discipline to reinitialize |
|
* |
|
* Completely reinitialize the line discipline state, by closing the current |
|
* instance, if there is one, and opening a new instance. If an error occurs |
|
* opening the new non-%N_TTY instance, the instance is dropped and @tty->ldisc |
|
* reset to %NULL. The caller can then retry with %N_TTY instead. |
|
* |
|
* Returns: 0 if successful, otherwise error code < 0 |
|
*/ |
|
int tty_ldisc_reinit(struct tty_struct *tty, int disc) |
|
{ |
|
struct tty_ldisc *ld; |
|
int retval; |
|
|
|
lockdep_assert_held_write(&tty->ldisc_sem); |
|
ld = tty_ldisc_get(tty, disc); |
|
if (IS_ERR(ld)) { |
|
BUG_ON(disc == N_TTY); |
|
return PTR_ERR(ld); |
|
} |
|
|
|
if (tty->ldisc) { |
|
tty_ldisc_close(tty, tty->ldisc); |
|
tty_ldisc_put(tty->ldisc); |
|
} |
|
|
|
/* switch the line discipline */ |
|
tty->ldisc = ld; |
|
tty_set_termios_ldisc(tty, disc); |
|
retval = tty_ldisc_open(tty, tty->ldisc); |
|
if (retval) { |
|
tty_ldisc_put(tty->ldisc); |
|
tty->ldisc = NULL; |
|
} |
|
return retval; |
|
} |
|
|
|
/** |
|
* tty_ldisc_hangup - hangup ldisc reset |
|
* @tty: tty being hung up |
|
* @reinit: whether to re-initialise the tty |
|
* |
|
* 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, bool reinit) |
|
{ |
|
struct tty_ldisc *ld; |
|
|
|
tty_ldisc_debug(tty, "%p: hangup\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, EPOLLOUT); |
|
wake_up_interruptible_poll(&tty->read_wait, EPOLLIN); |
|
|
|
/* |
|
* 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(tty, MAX_SCHEDULE_TIMEOUT); |
|
|
|
if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) |
|
tty_reset_termios(tty); |
|
|
|
if (tty->ldisc) { |
|
if (reinit) { |
|
if (tty_ldisc_reinit(tty, tty->termios.c_line) < 0 && |
|
tty_ldisc_reinit(tty, N_TTY) < 0) |
|
WARN_ON(tty_ldisc_reinit(tty, N_NULL) < 0); |
|
} else |
|
tty_ldisc_kill(tty); |
|
} |
|
tty_ldisc_unlock(tty); |
|
} |
|
|
|
/** |
|
* 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) |
|
{ |
|
int retval = tty_ldisc_open(tty, tty->ldisc); |
|
|
|
if (retval) |
|
return retval; |
|
|
|
if (o_tty) { |
|
/* |
|
* Called without o_tty->ldisc_sem held, as o_tty has been |
|
* just allocated and no one has a reference to it. |
|
*/ |
|
retval = tty_ldisc_open(o_tty, o_tty->ldisc); |
|
if (retval) { |
|
tty_ldisc_close(tty, tty->ldisc); |
|
return retval; |
|
} |
|
} |
|
return 0; |
|
} |
|
|
|
/** |
|
* tty_ldisc_release - release line discipline |
|
* @tty: tty being shut down (or one end of pty pair) |
|
* |
|
* Called during the final close of a tty or a pty pair in order to shut down |
|
* the line discpline layer. On exit, each tty's ldisc is %NULL. |
|
*/ |
|
void tty_ldisc_release(struct tty_struct *tty) |
|
{ |
|
struct tty_struct *o_tty = tty->link; |
|
|
|
/* |
|
* Shutdown this line discipline. As this is the final close, |
|
* it does not race with the set_ldisc code path. |
|
*/ |
|
|
|
tty_ldisc_lock_pair(tty, o_tty); |
|
tty_ldisc_kill(tty); |
|
if (o_tty) |
|
tty_ldisc_kill(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, "released\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. |
|
*/ |
|
int tty_ldisc_init(struct tty_struct *tty) |
|
{ |
|
struct tty_ldisc *ld = tty_ldisc_get(tty, N_TTY); |
|
|
|
if (IS_ERR(ld)) |
|
return PTR_ERR(ld); |
|
tty->ldisc = ld; |
|
return 0; |
|
} |
|
|
|
/** |
|
* tty_ldisc_deinit - ldisc cleanup for new tty |
|
* @tty: tty that was allocated recently |
|
* |
|
* The tty structure must not be completely set up (tty_ldisc_setup()) when |
|
* this call is made. |
|
*/ |
|
void tty_ldisc_deinit(struct tty_struct *tty) |
|
{ |
|
/* no ldisc_sem, tty is being destroyed */ |
|
if (tty->ldisc) |
|
tty_ldisc_put(tty->ldisc); |
|
tty->ldisc = NULL; |
|
} |
|
|
|
static struct ctl_table tty_table[] = { |
|
{ |
|
.procname = "ldisc_autoload", |
|
.data = &tty_ldisc_autoload, |
|
.maxlen = sizeof(tty_ldisc_autoload), |
|
.mode = 0644, |
|
.proc_handler = proc_dointvec, |
|
.extra1 = SYSCTL_ZERO, |
|
.extra2 = SYSCTL_ONE, |
|
}, |
|
{ } |
|
}; |
|
|
|
static struct ctl_table tty_dir_table[] = { |
|
{ |
|
.procname = "tty", |
|
.mode = 0555, |
|
.child = tty_table, |
|
}, |
|
{ } |
|
}; |
|
|
|
static struct ctl_table tty_root_table[] = { |
|
{ |
|
.procname = "dev", |
|
.mode = 0555, |
|
.child = tty_dir_table, |
|
}, |
|
{ } |
|
}; |
|
|
|
void tty_sysctl_init(void) |
|
{ |
|
register_sysctl_table(tty_root_table); |
|
}
|
|
|