// SPDX-License-Identifier: GPL-2.0 #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/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> #include "tty.h" #undef LDISC_DEBUG_HANGUP #ifdef LDISC_DEBUG_HANGUP #define tty_ldisc_debug … #else #define tty_ldisc_debug(tty, f, args...) … #endif /* lockdep nested classes for tty->ldisc_sem */ enum { … }; /* * 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 * @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(struct tty_ldisc_ops *new_ldisc) { … } EXPORT_SYMBOL(…); /** * tty_unregister_ldisc - unload a line discipline * @ldisc: ldisc number * * Remove a line discipline from the kernel providing it is not currently in * use. * * Locking: takes %tty_ldiscs_lock to guard against ldisc races */ void tty_unregister_ldisc(struct tty_ldisc_ops *ldisc) { … } EXPORT_SYMBOL(…); static struct tty_ldisc_ops *get_ldops(int disc) { … } static void put_ldops(struct tty_ldisc_ops *ldops) { … } int tty_ldisc_autoload = … IS_BUILTIN(…); /** * tty_ldisc_get - take a reference to an ldisc * @tty: tty device * @disc: ldisc number * * Takes a reference to a line discipline. Deals with refcounts and module * locking counts. If the discipline is not available, its module loaded, if * possible. * * Returns: * * -%EINVAL if the discipline index is not [%N_TTY .. %NR_LDISCS] or if the * discipline is not registered * * -%EAGAIN if request_module() failed to load or register the discipline * * -%ENOMEM if allocation failure * * Otherwise, returns a pointer to the discipline and bumps the ref count * * Locking: takes %tty_ldiscs_lock to guard against ldisc races */ static struct tty_ldisc *tty_ldisc_get(struct tty_struct *tty, int disc) { … } /** * tty_ldisc_put - release the ldisc * @ld: lisdsc to release * * Complement of tty_ldisc_get(). */ static void tty_ldisc_put(struct tty_ldisc *ld) { … } static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos) { … } static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos) { … } static void tty_ldiscs_seq_stop(struct seq_file *m, void *v) { … } static int tty_ldiscs_seq_show(struct seq_file *m, void *v) { … } const struct seq_operations tty_ldiscs_seq_ops = …; /** * 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. * * Returns: %NULL if the tty has been hungup and not re-opened with a new file * descriptor, otherwise valid ldisc reference * * Note 1: 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 2: a file_operations routine (read/poll/write) should use this function * to wait for any ldisc lifetime events to finish. */ struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty) { … } EXPORT_SYMBOL_GPL(…); /** * 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) { … } EXPORT_SYMBOL_GPL(…); /** * 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) { … } EXPORT_SYMBOL_GPL(…); static inline int __tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { … } static inline int __tty_ldisc_lock_nested(struct tty_struct *tty, unsigned long timeout) { … } static inline void __tty_ldisc_unlock(struct tty_struct *tty) { … } int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout) { … } void tty_ldisc_unlock(struct tty_struct *tty) { … } static int tty_ldisc_lock_pair_timeout(struct tty_struct *tty, struct tty_struct *tty2, unsigned long timeout) { … } static void tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2) { … } static void tty_ldisc_unlock_pair(struct tty_struct *tty, struct tty_struct *tty2) { … } /** * tty_ldisc_flush - flush line discipline queue * @tty: tty to flush ldisc for * * Flush the line discipline queue (if any) and the tty flip buffers for this * @tty. */ void tty_ldisc_flush(struct tty_struct *tty) { … } EXPORT_SYMBOL_GPL(…); /** * tty_set_termios_ldisc - set ldisc field * @tty: tty structure * @disc: 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. * * The line discipline-related tty_struct fields are reset to prevent the ldisc * driver from re-using stale information for the new ldisc instance. * * Locking: takes termios_rwsem */ static void tty_set_termios_ldisc(struct tty_struct *tty, int disc) { … } /** * 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) { … } /** * 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) { … } /** * tty_ldisc_failto - helper for ldisc failback * @tty: tty to open the ldisc on * @ld: ldisc we are trying to fail back to * * Helper to try and recover a tty when switching back to the old ldisc fails * and we need something attached. */ static int tty_ldisc_failto(struct tty_struct *tty, int ld) { … } /** * 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) { … } /** * tty_set_ldisc - set line discipline * @tty: the terminal to set * @disc: the line discipline number * * Set the discipline of a tty line. Must be called from a process context. The * ldisc change logic has to protect itself against any overlapping ldisc * change (including on the other end of pty pairs), the close of one side of a * tty/pty pair, and eventually hangup. */ int tty_set_ldisc(struct tty_struct *tty, int disc) { … } EXPORT_SYMBOL_GPL(…); /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … } /** * 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) { … }
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