mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-24 01:41:39 +00:00
![Kees Cook](/assets/img/avatar_default.png)
In preparation for adding another sysctl to the tty subsystem, move the tty setup code into the "core" tty code, which contains tty_init() itself. Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Jiri Slaby <jirislaby@kernel.org> Signed-off-by: Kees Cook <keescook@chromium.org> Link: https://lore.kernel.org/r/20221022182949.2684794-1-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
819 lines
20 KiB
C
819 lines
20 KiB
C
// 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(tty, f, args...) tty_debug(tty, f, ##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
|
|
* @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)
|
|
{
|
|
unsigned long flags;
|
|
int ret = 0;
|
|
|
|
if (new_ldisc->num < N_TTY || new_ldisc->num >= NR_LDISCS)
|
|
return -EINVAL;
|
|
|
|
raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
|
|
tty_ldiscs[new_ldisc->num] = new_ldisc;
|
|
raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL(tty_register_ldisc);
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
unsigned long flags;
|
|
|
|
raw_spin_lock_irqsave(&tty_ldiscs_lock, flags);
|
|
tty_ldiscs[ldisc->num] = NULL;
|
|
raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
|
|
}
|
|
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))
|
|
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);
|
|
module_put(ldops->owner);
|
|
raw_spin_unlock_irqrestore(&tty_ldiscs_lock, flags);
|
|
}
|
|
|
|
int tty_ldisc_autoload = IS_BUILTIN(CONFIG_LDISC_AUTOLOAD);
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
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)) {
|
|
if (!capable(CAP_SYS_MODULE) && !tty_ldisc_autoload)
|
|
return ERR_PTR(-EPERM);
|
|
request_module("tty-ldisc-%d", disc);
|
|
ldops = get_ldops(disc);
|
|
if (IS_ERR(ldops))
|
|
return ERR_CAST(ldops);
|
|
}
|
|
|
|
/*
|
|
* There is no way to handle allocation failure of only 16 bytes.
|
|
* Let's simplify error handling and save more memory.
|
|
*/
|
|
ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL | __GFP_NOFAIL);
|
|
ld->ops = ldops;
|
|
ld->tty = tty;
|
|
|
|
return ld;
|
|
}
|
|
|
|
/**
|
|
* tty_ldisc_put - release the ldisc
|
|
* @ld: lisdsc to release
|
|
*
|
|
* Complement of tty_ldisc_get().
|
|
*/
|
|
static 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;
|
|
}
|
|
|
|
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,
|
|
};
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
struct tty_ldisc *ld;
|
|
|
|
ldsem_down_read(&tty->ldisc_sem, MAX_SCHEDULE_TIMEOUT);
|
|
ld = tty->ldisc;
|
|
if (!ld)
|
|
ldsem_up_read(&tty->ldisc_sem);
|
|
return ld;
|
|
}
|
|
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
|
|
__tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
|
|
{
|
|
return ldsem_down_write(&tty->ldisc_sem, timeout);
|
|
}
|
|
|
|
static inline int
|
|
__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)
|
|
{
|
|
ldsem_up_write(&tty->ldisc_sem);
|
|
}
|
|
|
|
int tty_ldisc_lock(struct tty_struct *tty, unsigned long timeout)
|
|
{
|
|
int ret;
|
|
|
|
/* Kindly asking blocked readers to release the read side */
|
|
set_bit(TTY_LDISC_CHANGING, &tty->flags);
|
|
wake_up_interruptible_all(&tty->read_wait);
|
|
wake_up_interruptible_all(&tty->write_wait);
|
|
|
|
ret = __tty_ldisc_lock(tty, timeout);
|
|
if (!ret)
|
|
return -EBUSY;
|
|
set_bit(TTY_LDISC_HALTED, &tty->flags);
|
|
return 0;
|
|
}
|
|
|
|
void tty_ldisc_unlock(struct tty_struct *tty)
|
|
{
|
|
clear_bit(TTY_LDISC_HALTED, &tty->flags);
|
|
/* Can be cleared here - ldisc_unlock will wake up writers firstly */
|
|
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
|
|
__tty_ldisc_unlock(tty);
|
|
}
|
|
|
|
static int
|
|
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 tty_ldisc_lock_pair(struct tty_struct *tty, struct tty_struct *tty2)
|
|
{
|
|
tty_ldisc_lock_pair_timeout(tty, tty2, MAX_SCHEDULE_TIMEOUT);
|
|
}
|
|
|
|
static void tty_ldisc_unlock_pair(struct tty_struct *tty,
|
|
struct tty_struct *tty2)
|
|
{
|
|
__tty_ldisc_unlock(tty);
|
|
if (tty2)
|
|
__tty_ldisc_unlock(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)
|
|
{
|
|
struct tty_ldisc *ld = tty_ldisc_ref(tty);
|
|
|
|
tty_buffer_flush(tty, ld);
|
|
if (ld)
|
|
tty_ldisc_deref(ld);
|
|
}
|
|
EXPORT_SYMBOL_GPL(tty_ldisc_flush);
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
down_write(&tty->termios_rwsem);
|
|
tty->termios.c_line = disc;
|
|
up_write(&tty->termios_rwsem);
|
|
|
|
tty->disc_data = NULL;
|
|
tty->receive_room = 0;
|
|
}
|
|
|
|
/**
|
|
* 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);
|
|
|
|
tty_ldisc_debug(tty, "%p: opened\n", ld);
|
|
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)
|
|
{
|
|
lockdep_assert_held_write(&tty->ldisc_sem);
|
|
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_debug(tty, "%p: closed\n", 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)
|
|
{
|
|
struct tty_ldisc *disc = tty_ldisc_get(tty, ld);
|
|
int r;
|
|
|
|
lockdep_assert_held_write(&tty->ldisc_sem);
|
|
if (IS_ERR(disc))
|
|
return PTR_ERR(disc);
|
|
tty->ldisc = disc;
|
|
tty_set_termios_ldisc(tty, ld);
|
|
r = tty_ldisc_open(tty, disc);
|
|
if (r < 0)
|
|
tty_ldisc_put(disc);
|
|
return r;
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
/* There is an outstanding reference here so this is safe */
|
|
if (tty_ldisc_failto(tty, old->ops->num) < 0) {
|
|
const char *name = tty_name(tty);
|
|
|
|
pr_warn("Falling back ldisc for %s.\n", name);
|
|
/*
|
|
* The traditional behaviour is to fall back to N_TTY, we
|
|
* want to avoid falling back to N_NULL unless we have no
|
|
* choice to avoid the risk of breaking anything
|
|
*/
|
|
if (tty_ldisc_failto(tty, N_TTY) < 0 &&
|
|
tty_ldisc_failto(tty, N_NULL) < 0)
|
|
panic("Couldn't open N_NULL ldisc for %s.", name);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* 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)
|
|
{
|
|
int retval;
|
|
struct tty_ldisc *old_ldisc, *new_ldisc;
|
|
|
|
new_ldisc = tty_ldisc_get(tty, disc);
|
|
if (IS_ERR(new_ldisc))
|
|
return PTR_ERR(new_ldisc);
|
|
|
|
tty_lock(tty);
|
|
retval = tty_ldisc_lock(tty, 5 * HZ);
|
|
if (retval)
|
|
goto err;
|
|
|
|
if (!tty->ldisc) {
|
|
retval = -EIO;
|
|
goto out;
|
|
}
|
|
|
|
/* Check the no-op case */
|
|
if (tty->ldisc->ops->num == disc)
|
|
goto out;
|
|
|
|
if (test_bit(TTY_HUPPED, &tty->flags)) {
|
|
/* We were raced by hangup */
|
|
retval = -EIO;
|
|
goto out;
|
|
}
|
|
|
|
old_ldisc = tty->ldisc;
|
|
|
|
/* Shutdown the old discipline. */
|
|
tty_ldisc_close(tty, old_ldisc);
|
|
|
|
/* Now set up the new line discipline. */
|
|
tty->ldisc = new_ldisc;
|
|
tty_set_termios_ldisc(tty, disc);
|
|
|
|
retval = tty_ldisc_open(tty, new_ldisc);
|
|
if (retval < 0) {
|
|
/* Back to the old one or N_TTY if we can't */
|
|
tty_ldisc_put(new_ldisc);
|
|
tty_ldisc_restore(tty, old_ldisc);
|
|
}
|
|
|
|
if (tty->ldisc->ops->num != old_ldisc->ops->num && tty->ops->set_ldisc) {
|
|
down_read(&tty->termios_rwsem);
|
|
tty->ops->set_ldisc(tty);
|
|
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;
|
|
}
|