tty: Split ldisc code into its own file
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
new file mode 100644
index 0000000..241cbde
--- /dev/null
+++ b/drivers/char/tty_ldisc.c
@@ -0,0 +1,714 @@
+#include <linux/types.h>
+#include <linux/major.h>
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/fcntl.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/tty.h>
+#include <linux/tty_driver.h>
+#include <linux/tty_flip.h>
+#include <linux/devpts_fs.h>
+#include <linux/file.h>
+#include <linux/fdtable.h>
+#include <linux/console.h>
+#include <linux/timer.h>
+#include <linux/ctype.h>
+#include <linux/kd.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/smp_lock.h>
+#include <linux/device.h>
+#include <linux/wait.h>
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/seq_file.h>
+
+#include <linux/uaccess.h>
+#include <asm/system.h>
+
+#include <linux/kbd_kern.h>
+#include <linux/vt_kern.h>
+#include <linux/selection.h>
+
+#include <linux/kmod.h>
+#include <linux/nsproxy.h>
+
+/*
+ * 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_SPINLOCK(tty_ldisc_lock);
+static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
+/* 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_ldisc_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;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ tty_ldiscs[disc] = new_ldisc;
+ new_ldisc->num = disc;
+ new_ldisc->refcount = 0;
+ spin_unlock_irqrestore(&tty_ldisc_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_ldisc_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;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ if (tty_ldiscs[disc]->refcount)
+ ret = -EBUSY;
+ else
+ tty_ldiscs[disc] = NULL;
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL(tty_unregister_ldisc);
+
+
+/**
+ * tty_ldisc_try_get - try and reference an ldisc
+ * @disc: ldisc number
+ * @ld: tty ldisc structure to complete
+ *
+ * Attempt to open and lock a line discipline into place. Return
+ * the line discipline refcounted and assigned in ld. On an error
+ * report the error code back
+ */
+
+static int tty_ldisc_try_get(int disc, struct tty_ldisc *ld)
+{
+ unsigned long flags;
+ struct tty_ldisc_ops *ldops;
+ int err = -EINVAL;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ld->ops = NULL;
+ ldops = tty_ldiscs[disc];
+ /* Check the entry is defined */
+ if (ldops) {
+ /* If the module is being unloaded we can't use it */
+ if (!try_module_get(ldops->owner))
+ err = -EAGAIN;
+ else {
+ /* lock it */
+ ldops->refcount++;
+ ld->ops = ldops;
+ err = 0;
+ }
+ }
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ return err;
+}
+
+/**
+ * tty_ldisc_get - take a reference to an ldisc
+ * @disc: ldisc number
+ * @ld: tty line discipline structure to use
+ *
+ * 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_ldisc_lock to guard against ldisc races
+ */
+
+static int tty_ldisc_get(int disc, struct tty_ldisc *ld)
+{
+ int err;
+
+ if (disc < N_TTY || disc >= NR_LDISCS)
+ return -EINVAL;
+ err = tty_ldisc_try_get(disc, ld);
+ if (err == -EAGAIN) {
+ request_module("tty-ldisc-%d", disc);
+ err = tty_ldisc_try_get(disc, ld);
+ }
+ return err;
+}
+
+/**
+ * tty_ldisc_put - drop ldisc reference
+ * @disc: ldisc number
+ *
+ * Drop a reference to a line discipline. Manage refcounts and
+ * module usage counts
+ *
+ * Locking:
+ * takes tty_ldisc_lock to guard against ldisc races
+ */
+
+static void tty_ldisc_put(struct tty_ldisc_ops *ld)
+{
+ unsigned long flags;
+ int disc = ld->num;
+
+ BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ld = tty_ldiscs[disc];
+ BUG_ON(ld->refcount == 0);
+ ld->refcount--;
+ module_put(ld->owner);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+}
+
+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 ld;
+
+ if (tty_ldisc_get(i, &ld) < 0)
+ return 0;
+ seq_printf(m, "%-10s %2d\n", ld.ops->name ? ld.ops->name : "???", i);
+ tty_ldisc_put(ld.ops);
+ 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_assign - set ldisc on a tty
+ * @tty: tty to assign
+ * @ld: line discipline
+ *
+ * Install an instance of a line discipline into a tty structure. The
+ * ldisc must have a reference count above zero to ensure it remains/
+ * The tty instance refcount starts at zero.
+ *
+ * Locking:
+ * Caller must hold references
+ */
+
+static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
+{
+ ld->refcount = 0;
+ tty->ldisc = *ld;
+}
+
+/**
+ * tty_ldisc_try - internal helper
+ * @tty: the tty
+ *
+ * Make a single attempt to grab and bump the refcount on
+ * the tty ldisc. Return 0 on failure or 1 on success. This is
+ * used to implement both the waiting and non waiting versions
+ * of tty_ldisc_ref
+ *
+ * Locking: takes tty_ldisc_lock
+ */
+
+static int tty_ldisc_try(struct tty_struct *tty)
+{
+ unsigned long flags;
+ struct tty_ldisc *ld;
+ int ret = 0;
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ ld = &tty->ldisc;
+ if (test_bit(TTY_LDISC, &tty->flags)) {
+ ld->refcount++;
+ ret = 1;
+ }
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ return ret;
+}
+
+/**
+ * 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)
+ *
+ * Locking: call functions take tty_ldisc_lock
+ */
+
+struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
+{
+ /* wait_event is a macro */
+ wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
+ if (tty->ldisc.refcount == 0)
+ printk(KERN_ERR "tty_ldisc_ref_wait\n");
+ 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.
+ *
+ * Locking: called functions take tty_ldisc_lock
+ */
+
+struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
+{
+ if (tty_ldisc_try(tty))
+ return &tty->ldisc;
+ return NULL;
+}
+
+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.
+ *
+ * Locking: takes tty_ldisc_lock
+ */
+
+void tty_ldisc_deref(struct tty_ldisc *ld)
+{
+ unsigned long flags;
+
+ BUG_ON(ld == NULL);
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ if (ld->refcount == 0)
+ printk(KERN_ERR "tty_ldisc_deref: no references.\n");
+ else
+ ld->refcount--;
+ if (ld->refcount == 0)
+ wake_up(&tty_ldisc_wait);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+}
+
+EXPORT_SYMBOL_GPL(tty_ldisc_deref);
+
+/**
+ * tty_ldisc_enable - allow ldisc use
+ * @tty: terminal to activate ldisc on
+ *
+ * Set the TTY_LDISC flag when the line discipline can be called
+ * again. Do necessary wakeups for existing sleepers.
+ *
+ * Note: nobody should set this bit except via this function. Clearing
+ * directly is allowed.
+ */
+
+void tty_ldisc_enable(struct tty_struct *tty)
+{
+ set_bit(TTY_LDISC, &tty->flags);
+ wake_up(&tty_ldisc_wait);
+}
+
+/**
+ * tty_set_termios_ldisc - set ldisc field
+ * @tty: tty structure
+ * @num: line discipline number
+ *
+ * This is probably overkill for real world processors but
+ * they are not on hot paths so a little discipline won't do
+ * any harm.
+ *
+ * Locking: takes termios_mutex
+ */
+
+static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
+{
+ mutex_lock(&tty->termios_mutex);
+ tty->termios->c_line = num;
+ mutex_unlock(&tty->termios_mutex);
+}
+
+
+/**
+ * tty_ldisc_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;
+
+ /* There is an outstanding reference here so this is safe */
+ tty_ldisc_get(old->ops->num, old);
+ tty_ldisc_assign(tty, old);
+ tty_set_termios_ldisc(tty, old->ops->num);
+ if (old->ops->open && (old->ops->open(tty) < 0)) {
+ tty_ldisc_put(old->ops);
+ /* This driver is always present */
+ if (tty_ldisc_get(N_TTY, &new_ldisc) < 0)
+ panic("n_tty: get");
+ tty_ldisc_assign(tty, &new_ldisc);
+ tty_set_termios_ldisc(tty, N_TTY);
+ if (new_ldisc.ops->open) {
+ int r = new_ldisc.ops->open(tty);
+ if (r < 0)
+ panic("Couldn't open N_TTY ldisc for "
+ "%s --- error %d.",
+ tty_name(tty, buf), r);
+ }
+ }
+}
+
+/**
+ * tty_set_ldisc - set line discipline
+ * @tty: the terminal to set
+ * @ldisc: the line discipline
+ *
+ * Set the discipline of a tty line. Must be called from a process
+ * context.
+ *
+ * Locking: takes tty_ldisc_lock.
+ * called functions take termios_mutex
+ */
+
+int tty_set_ldisc(struct tty_struct *tty, int ldisc)
+{
+ int retval;
+ struct tty_ldisc o_ldisc, new_ldisc;
+ int work;
+ unsigned long flags;
+ struct tty_struct *o_tty;
+
+restart:
+ /* This is a bit ugly for now but means we can break the 'ldisc
+ is part of the tty struct' assumption later */
+ retval = tty_ldisc_get(ldisc, &new_ldisc);
+ if (retval)
+ return retval;
+
+ /*
+ * Problem: What do we do if this blocks ?
+ */
+
+ tty_wait_until_sent(tty, 0);
+
+ if (tty->ldisc.ops->num == ldisc) {
+ tty_ldisc_put(new_ldisc.ops);
+ return 0;
+ }
+
+ /*
+ * No more input please, we are switching. The new ldisc
+ * will update this value in the ldisc open function
+ */
+
+ tty->receive_room = 0;
+
+ o_ldisc = tty->ldisc;
+ o_tty = tty->link;
+
+ /*
+ * Make sure we don't change while someone holds a
+ * reference to the line discipline. The TTY_LDISC bit
+ * prevents anyone taking a reference once it is clear.
+ * We need the lock to avoid racing reference takers.
+ */
+
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
+ if (tty->ldisc.refcount) {
+ /* Free the new ldisc we grabbed. Must drop the lock
+ first. */
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ tty_ldisc_put(o_ldisc.ops);
+ /*
+ * There are several reasons we may be busy, including
+ * random momentary I/O traffic. We must therefore
+ * retry. We could distinguish between blocking ops
+ * and retries if we made tty_ldisc_wait() smarter.
+ * That is up for discussion.
+ */
+ if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
+ return -ERESTARTSYS;
+ goto restart;
+ }
+ if (o_tty && o_tty->ldisc.refcount) {
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ tty_ldisc_put(o_tty->ldisc.ops);
+ if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
+ return -ERESTARTSYS;
+ goto restart;
+ }
+ }
+ /*
+ * If the TTY_LDISC bit is set, then we are racing against
+ * another ldisc change
+ */
+ if (!test_bit(TTY_LDISC, &tty->flags)) {
+ struct tty_ldisc *ld;
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ tty_ldisc_put(new_ldisc.ops);
+ ld = tty_ldisc_ref_wait(tty);
+ tty_ldisc_deref(ld);
+ goto restart;
+ }
+
+ clear_bit(TTY_LDISC, &tty->flags);
+ if (o_tty)
+ clear_bit(TTY_LDISC, &o_tty->flags);
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+
+ /*
+ * From this point on we know nobody has an ldisc
+ * usage reference, nor can they obtain one until
+ * we say so later on.
+ */
+
+ work = cancel_delayed_work(&tty->buf.work);
+ /*
+ * Wait for ->hangup_work and ->buf.work handlers to terminate
+ * MUST NOT hold locks here.
+ */
+ flush_scheduled_work();
+ /* Shutdown the current discipline. */
+ if (o_ldisc.ops->close)
+ (o_ldisc.ops->close)(tty);
+
+ /* Now set up the new line discipline. */
+ tty_ldisc_assign(tty, &new_ldisc);
+ tty_set_termios_ldisc(tty, ldisc);
+ if (new_ldisc.ops->open)
+ retval = (new_ldisc.ops->open)(tty);
+ if (retval < 0) {
+ tty_ldisc_put(new_ldisc.ops);
+ tty_ldisc_restore(tty, &o_ldisc);
+ }
+ /* At this point we hold a reference to the new ldisc and a
+ a reference to the old ldisc. If we ended up flipping back
+ to the existing ldisc we have two references to it */
+
+ if (tty->ldisc.ops->num != o_ldisc.ops->num && tty->ops->set_ldisc)
+ tty->ops->set_ldisc(tty);
+
+ tty_ldisc_put(o_ldisc.ops);
+
+ /*
+ * Allow ldisc referencing to occur as soon as the driver
+ * ldisc callback completes.
+ */
+
+ tty_ldisc_enable(tty);
+ if (o_tty)
+ tty_ldisc_enable(o_tty);
+
+ /* Restart it in case no characters kick it off. Safe if
+ already running */
+ if (work)
+ schedule_delayed_work(&tty->buf.work, 1);
+ return retval;
+}
+
+
+/**
+ * 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 discplines and bind them to the tty.
+ */
+
+int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
+{
+ struct tty_ldisc *ld = &tty->ldisc;
+ int retval;
+
+ if (ld->ops->open) {
+ retval = (ld->ops->open)(tty);
+ if (retval)
+ return retval;
+ }
+ if (o_tty && o_tty->ldisc.ops->open) {
+ retval = (o_tty->ldisc.ops->open)(o_tty);
+ if (retval) {
+ if (ld->ops->close)
+ (ld->ops->close)(tty);
+ return retval;
+ }
+ tty_ldisc_enable(o_tty);
+ }
+ tty_ldisc_enable(tty);
+ return 0;
+}
+
+/**
+ * tty_ldisc_release - release line discipline
+ * @tty: tty being shut down
+ * @o_tty: pair tty for pty/tty pairs
+ *
+ * Called during the final close of a tty/pty pair in order to shut down the
+ * line discpline layer.
+ */
+
+void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
+{
+ unsigned long flags;
+ struct tty_ldisc ld;
+ /*
+ * Prevent flush_to_ldisc() from rescheduling the work for later. Then
+ * kill any delayed work. As this is the final close it does not
+ * race with the set_ldisc code path.
+ */
+ clear_bit(TTY_LDISC, &tty->flags);
+ cancel_delayed_work(&tty->buf.work);
+
+ /*
+ * Wait for ->hangup_work and ->buf.work handlers to terminate
+ */
+
+ flush_scheduled_work();
+
+ /*
+ * Wait for any short term users (we know they are just driver
+ * side waiters as the file is closing so user count on the file
+ * side is zero.
+ */
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ while (tty->ldisc.refcount) {
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
+ spin_lock_irqsave(&tty_ldisc_lock, flags);
+ }
+ spin_unlock_irqrestore(&tty_ldisc_lock, flags);
+ /*
+ * Shutdown the current line discipline, and reset it to N_TTY.
+ *
+ * FIXME: this MUST get fixed for the new reflocking
+ */
+ if (tty->ldisc.ops->close)
+ (tty->ldisc.ops->close)(tty);
+ tty_ldisc_put(tty->ldisc.ops);
+
+ /*
+ * Switch the line discipline back
+ */
+ WARN_ON(tty_ldisc_get(N_TTY, &ld));
+ tty_ldisc_assign(tty, &ld);
+ tty_set_termios_ldisc(tty, N_TTY);
+ if (o_tty) {
+ /* FIXME: could o_tty be in setldisc here ? */
+ clear_bit(TTY_LDISC, &o_tty->flags);
+ if (o_tty->ldisc.ops->close)
+ (o_tty->ldisc.ops->close)(o_tty);
+ tty_ldisc_put(o_tty->ldisc.ops);
+ WARN_ON(tty_ldisc_get(N_TTY, &ld));
+ tty_ldisc_assign(o_tty, &ld);
+ tty_set_termios_ldisc(o_tty, N_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.
+ */
+
+void tty_ldisc_init(struct tty_struct *tty)
+{
+ struct tty_ldisc ld;
+ if (tty_ldisc_get(N_TTY, &ld) < 0)
+ panic("n_tty: init_tty");
+ tty_ldisc_assign(tty, &ld);
+}
+
+void tty_ldisc_begin(void)
+{
+ /* Setup the default TTY line discipline. */
+ (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
+}