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linux/drivers/char/tty_ioctl.c
Alan Cox 5f412b2424 [PATCH] Fix locking for tty drivers when doing urgent characters 
If you send a priority character (as is done for flow control) then the tty
driver can either have its own method for "jumping the queue" or the characrer
can be queued normally.  In the latter case we call the write method but
without the atomic_write_lock taken elsewhere.

Make this consistent.  Note that the send_xchar method if implemented remains
outside of the lock as it can jump ahead of a current write so must not be
locked out by it.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-29 09:18:24 -07:00

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/*
* linux/drivers/char/tty_ioctl.c
*
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
*
* Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
* which can be dynamically activated and de-activated by the line
* discipline handling modules (like SLIP).
*/
#include <linux/types.h>
#include <linux/termios.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/tty.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#undef TTY_DEBUG_WAIT_UNTIL_SENT
#undef DEBUG
/*
* Internal flag options for termios setting behavior
*/
#define TERMIOS_FLUSH 1
#define TERMIOS_WAIT 2
#define TERMIOS_TERMIO 4
/**
* tty_wait_until_sent - wait for I/O to finish
* @tty: tty we are waiting for
* @timeout: how long we will wait
*
* Wait for characters pending in a tty driver to hit the wire, or
* for a timeout to occur (eg due to flow control)
*
* Locking: none
*/
void tty_wait_until_sent(struct tty_struct * tty, long timeout)
{
DECLARE_WAITQUEUE(wait, current);
#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
char buf[64];
printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
#endif
if (!tty->driver->chars_in_buffer)
return;
add_wait_queue(&tty->write_wait, &wait);
if (!timeout)
timeout = MAX_SCHEDULE_TIMEOUT;
do {
#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
printk(KERN_DEBUG "waiting %s...(%d)\n", tty_name(tty, buf),
tty->driver->chars_in_buffer(tty));
#endif
set_current_state(TASK_INTERRUPTIBLE);
if (signal_pending(current))
goto stop_waiting;
if (!tty->driver->chars_in_buffer(tty))
break;
timeout = schedule_timeout(timeout);
} while (timeout);
if (tty->driver->wait_until_sent)
tty->driver->wait_until_sent(tty, timeout);
stop_waiting:
set_current_state(TASK_RUNNING);
remove_wait_queue(&tty->write_wait, &wait);
}
EXPORT_SYMBOL(tty_wait_until_sent);
static void unset_locked_termios(struct termios *termios,
struct termios *old,
struct termios *locked)
{
int i;
#define NOSET_MASK(x,y,z) (x = ((x) & ~(z)) | ((y) & (z)))
if (!locked) {
printk(KERN_WARNING "Warning?!? termios_locked is NULL.\n");
return;
}
NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
termios->c_line = locked->c_line ? old->c_line : termios->c_line;
for (i=0; i < NCCS; i++)
termios->c_cc[i] = locked->c_cc[i] ?
old->c_cc[i] : termios->c_cc[i];
}
/**
* change_termios - update termios values
* @tty: tty to update
* @new_termios: desired new value
*
* Perform updates to the termios values set on this terminal. There
* is a bit of layering violation here with n_tty in terms of the
* internal knowledge of this function.
*
* Locking: termios_sem
*/
static void change_termios(struct tty_struct * tty, struct termios * new_termios)
{
int canon_change;
struct termios old_termios = *tty->termios;
struct tty_ldisc *ld;
/*
* Perform the actual termios internal changes under lock.
*/
/* FIXME: we need to decide on some locking/ordering semantics
for the set_termios notification eventually */
mutex_lock(&tty->termios_mutex);
*tty->termios = *new_termios;
unset_locked_termios(tty->termios, &old_termios, tty->termios_locked);
canon_change = (old_termios.c_lflag ^ tty->termios->c_lflag) & ICANON;
if (canon_change) {
memset(&tty->read_flags, 0, sizeof tty->read_flags);
tty->canon_head = tty->read_tail;
tty->canon_data = 0;
tty->erasing = 0;
}
if (canon_change && !L_ICANON(tty) && tty->read_cnt)
/* Get characters left over from canonical mode. */
wake_up_interruptible(&tty->read_wait);
/* See if packet mode change of state. */
if (tty->link && tty->link->packet) {
int old_flow = ((old_termios.c_iflag & IXON) &&
(old_termios.c_cc[VSTOP] == '\023') &&
(old_termios.c_cc[VSTART] == '\021'));
int new_flow = (I_IXON(tty) &&
STOP_CHAR(tty) == '\023' &&
START_CHAR(tty) == '\021');
if (old_flow != new_flow) {
tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
if (new_flow)
tty->ctrl_status |= TIOCPKT_DOSTOP;
else
tty->ctrl_status |= TIOCPKT_NOSTOP;
wake_up_interruptible(&tty->link->read_wait);
}
}
if (tty->driver->set_termios)
(*tty->driver->set_termios)(tty, &old_termios);
ld = tty_ldisc_ref(tty);
if (ld != NULL) {
if (ld->set_termios)
(ld->set_termios)(tty, &old_termios);
tty_ldisc_deref(ld);
}
mutex_unlock(&tty->termios_mutex);
}
/**
* set_termios - set termios values for a tty
* @tty: terminal device
* @arg: user data
* @opt: option information
*
* Helper function to prepare termios data and run neccessary other
* functions before using change_termios to do the actual changes.
*
* Locking:
* Called functions take ldisc and termios_sem locks
*/
static int set_termios(struct tty_struct * tty, void __user *arg, int opt)
{
struct termios tmp_termios;
struct tty_ldisc *ld;
int retval = tty_check_change(tty);
if (retval)
return retval;
if (opt & TERMIOS_TERMIO) {
memcpy(&tmp_termios, tty->termios, sizeof(struct termios));
if (user_termio_to_kernel_termios(&tmp_termios,
(struct termio __user *)arg))
return -EFAULT;
} else {
if (user_termios_to_kernel_termios(&tmp_termios,
(struct termios __user *)arg))
return -EFAULT;
}
ld = tty_ldisc_ref(tty);
if (ld != NULL) {
if ((opt & TERMIOS_FLUSH) && ld->flush_buffer)
ld->flush_buffer(tty);
tty_ldisc_deref(ld);
}
if (opt & TERMIOS_WAIT) {
tty_wait_until_sent(tty, 0);
if (signal_pending(current))
return -EINTR;
}
change_termios(tty, &tmp_termios);
return 0;
}
static int get_termio(struct tty_struct * tty, struct termio __user * termio)
{
if (kernel_termios_to_user_termio(termio, tty->termios))
return -EFAULT;
return 0;
}
static unsigned long inq_canon(struct tty_struct * tty)
{
int nr, head, tail;
if (!tty->canon_data || !tty->read_buf)
return 0;
head = tty->canon_head;
tail = tty->read_tail;
nr = (head - tail) & (N_TTY_BUF_SIZE-1);
/* Skip EOF-chars.. */
while (head != tail) {
if (test_bit(tail, tty->read_flags) &&
tty->read_buf[tail] == __DISABLED_CHAR)
nr--;
tail = (tail+1) & (N_TTY_BUF_SIZE-1);
}
return nr;
}
#ifdef TIOCGETP
/*
* These are deprecated, but there is limited support..
*
* The "sg_flags" translation is a joke..
*/
static int get_sgflags(struct tty_struct * tty)
{
int flags = 0;
if (!(tty->termios->c_lflag & ICANON)) {
if (tty->termios->c_lflag & ISIG)
flags |= 0x02; /* cbreak */
else
flags |= 0x20; /* raw */
}
if (tty->termios->c_lflag & ECHO)
flags |= 0x08; /* echo */
if (tty->termios->c_oflag & OPOST)
if (tty->termios->c_oflag & ONLCR)
flags |= 0x10; /* crmod */
return flags;
}
static int get_sgttyb(struct tty_struct * tty, struct sgttyb __user * sgttyb)
{
struct sgttyb tmp;
mutex_lock(&tty->termios_mutex);
tmp.sg_ispeed = 0;
tmp.sg_ospeed = 0;
tmp.sg_erase = tty->termios->c_cc[VERASE];
tmp.sg_kill = tty->termios->c_cc[VKILL];
tmp.sg_flags = get_sgflags(tty);
mutex_unlock(&tty->termios_mutex);
return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}
static void set_sgflags(struct termios * termios, int flags)
{
termios->c_iflag = ICRNL | IXON;
termios->c_oflag = 0;
termios->c_lflag = ISIG | ICANON;
if (flags & 0x02) { /* cbreak */
termios->c_iflag = 0;
termios->c_lflag &= ~ICANON;
}
if (flags & 0x08) { /* echo */
termios->c_lflag |= ECHO | ECHOE | ECHOK |
ECHOCTL | ECHOKE | IEXTEN;
}
if (flags & 0x10) { /* crmod */
termios->c_oflag |= OPOST | ONLCR;
}
if (flags & 0x20) { /* raw */
termios->c_iflag = 0;
termios->c_lflag &= ~(ISIG | ICANON);
}
if (!(termios->c_lflag & ICANON)) {
termios->c_cc[VMIN] = 1;
termios->c_cc[VTIME] = 0;
}
}
/**
* set_sgttyb - set legacy terminal values
* @tty: tty structure
* @sgttyb: pointer to old style terminal structure
*
* Updates a terminal from the legacy BSD style terminal information
* structure.
*
* Locking: termios_sem
*/
static int set_sgttyb(struct tty_struct * tty, struct sgttyb __user * sgttyb)
{
int retval;
struct sgttyb tmp;
struct termios termios;
retval = tty_check_change(tty);
if (retval)
return retval;
if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
return -EFAULT;
mutex_lock(&tty->termios_mutex);
termios = *tty->termios;
termios.c_cc[VERASE] = tmp.sg_erase;
termios.c_cc[VKILL] = tmp.sg_kill;
set_sgflags(&termios, tmp.sg_flags);
mutex_unlock(&tty->termios_mutex);
change_termios(tty, &termios);
return 0;
}
#endif
#ifdef TIOCGETC
static int get_tchars(struct tty_struct * tty, struct tchars __user * tchars)
{
struct tchars tmp;
tmp.t_intrc = tty->termios->c_cc[VINTR];
tmp.t_quitc = tty->termios->c_cc[VQUIT];
tmp.t_startc = tty->termios->c_cc[VSTART];
tmp.t_stopc = tty->termios->c_cc[VSTOP];
tmp.t_eofc = tty->termios->c_cc[VEOF];
tmp.t_brkc = tty->termios->c_cc[VEOL2]; /* what is brkc anyway? */
return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}
static int set_tchars(struct tty_struct * tty, struct tchars __user * tchars)
{
struct tchars tmp;
if (copy_from_user(&tmp, tchars, sizeof(tmp)))
return -EFAULT;
tty->termios->c_cc[VINTR] = tmp.t_intrc;
tty->termios->c_cc[VQUIT] = tmp.t_quitc;
tty->termios->c_cc[VSTART] = tmp.t_startc;
tty->termios->c_cc[VSTOP] = tmp.t_stopc;
tty->termios->c_cc[VEOF] = tmp.t_eofc;
tty->termios->c_cc[VEOL2] = tmp.t_brkc; /* what is brkc anyway? */
return 0;
}
#endif
#ifdef TIOCGLTC
static int get_ltchars(struct tty_struct * tty, struct ltchars __user * ltchars)
{
struct ltchars tmp;
tmp.t_suspc = tty->termios->c_cc[VSUSP];
tmp.t_dsuspc = tty->termios->c_cc[VSUSP]; /* what is dsuspc anyway? */
tmp.t_rprntc = tty->termios->c_cc[VREPRINT];
tmp.t_flushc = tty->termios->c_cc[VEOL2]; /* what is flushc anyway? */
tmp.t_werasc = tty->termios->c_cc[VWERASE];
tmp.t_lnextc = tty->termios->c_cc[VLNEXT];
return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}
static int set_ltchars(struct tty_struct * tty, struct ltchars __user * ltchars)
{
struct ltchars tmp;
if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
return -EFAULT;
tty->termios->c_cc[VSUSP] = tmp.t_suspc;
tty->termios->c_cc[VEOL2] = tmp.t_dsuspc; /* what is dsuspc anyway? */
tty->termios->c_cc[VREPRINT] = tmp.t_rprntc;
tty->termios->c_cc[VEOL2] = tmp.t_flushc; /* what is flushc anyway? */
tty->termios->c_cc[VWERASE] = tmp.t_werasc;
tty->termios->c_cc[VLNEXT] = tmp.t_lnextc;
return 0;
}
#endif
/**
* send_prio_char - send priority character
*
* Send a high priority character to the tty even if stopped
*
* Locking: none for xchar method, write ordering for write method.
*/
static int send_prio_char(struct tty_struct *tty, char ch)
{
int was_stopped = tty->stopped;
if (tty->driver->send_xchar) {
tty->driver->send_xchar(tty, ch);
return 0;
}
if (mutex_lock_interruptible(&tty->atomic_write_lock))
return -ERESTARTSYS;
if (was_stopped)
start_tty(tty);
tty->driver->write(tty, &ch, 1);
if (was_stopped)
stop_tty(tty);
mutex_unlock(&tty->atomic_write_lock);
return 0;
}
int n_tty_ioctl(struct tty_struct * tty, struct file * file,
unsigned int cmd, unsigned long arg)
{
struct tty_struct * real_tty;
void __user *p = (void __user *)arg;
int retval;
struct tty_ldisc *ld;
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_MASTER)
real_tty = tty->link;
else
real_tty = tty;
switch (cmd) {
#ifdef TIOCGETP
case TIOCGETP:
return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
case TIOCSETP:
case TIOCSETN:
return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
#endif
#ifdef TIOCGETC
case TIOCGETC:
return get_tchars(real_tty, p);
case TIOCSETC:
return set_tchars(real_tty, p);
#endif
#ifdef TIOCGLTC
case TIOCGLTC:
return get_ltchars(real_tty, p);
case TIOCSLTC:
return set_ltchars(real_tty, p);
#endif
case TCGETS:
if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios))
return -EFAULT;
return 0;
case TCSETSF:
return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT);
case TCSETSW:
return set_termios(real_tty, p, TERMIOS_WAIT);
case TCSETS:
return set_termios(real_tty, p, 0);
case TCGETA:
return get_termio(real_tty, p);
case TCSETAF:
return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
case TCSETAW:
return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
case TCSETA:
return set_termios(real_tty, p, TERMIOS_TERMIO);
case TCXONC:
retval = tty_check_change(tty);
if (retval)
return retval;
switch (arg) {
case TCOOFF:
if (!tty->flow_stopped) {
tty->flow_stopped = 1;
stop_tty(tty);
}
break;
case TCOON:
if (tty->flow_stopped) {
tty->flow_stopped = 0;
start_tty(tty);
}
break;
case TCIOFF:
if (STOP_CHAR(tty) != __DISABLED_CHAR)
return send_prio_char(tty, STOP_CHAR(tty));
break;
case TCION:
if (START_CHAR(tty) != __DISABLED_CHAR)
return send_prio_char(tty, START_CHAR(tty));
break;
default:
return -EINVAL;
}
return 0;
case TCFLSH:
retval = tty_check_change(tty);
if (retval)
return retval;
ld = tty_ldisc_ref(tty);
switch (arg) {
case TCIFLUSH:
if (ld && ld->flush_buffer)
ld->flush_buffer(tty);
break;
case TCIOFLUSH:
if (ld && ld->flush_buffer)
ld->flush_buffer(tty);
/* fall through */
case TCOFLUSH:
if (tty->driver->flush_buffer)
tty->driver->flush_buffer(tty);
break;
default:
tty_ldisc_deref(ld);
return -EINVAL;
}
tty_ldisc_deref(ld);
return 0;
case TIOCOUTQ:
return put_user(tty->driver->chars_in_buffer ?
tty->driver->chars_in_buffer(tty) : 0,
(int __user *) arg);
case TIOCINQ:
retval = tty->read_cnt;
if (L_ICANON(tty))
retval = inq_canon(tty);
return put_user(retval, (unsigned int __user *) arg);
case TIOCGLCKTRMIOS:
if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios_locked))
return -EFAULT;
return 0;
case TIOCSLCKTRMIOS:
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (user_termios_to_kernel_termios(real_tty->termios_locked, (struct termios __user *) arg))
return -EFAULT;
return 0;
case TIOCPKT:
{
int pktmode;
if (tty->driver->type != TTY_DRIVER_TYPE_PTY ||
tty->driver->subtype != PTY_TYPE_MASTER)
return -ENOTTY;
if (get_user(pktmode, (int __user *) arg))
return -EFAULT;
if (pktmode) {
if (!tty->packet) {
tty->packet = 1;
tty->link->ctrl_status = 0;
}
} else
tty->packet = 0;
return 0;
}
case TIOCGSOFTCAR:
return put_user(C_CLOCAL(tty) ? 1 : 0, (int __user *)arg);
case TIOCSSOFTCAR:
if (get_user(arg, (unsigned int __user *) arg))
return -EFAULT;
mutex_lock(&tty->termios_mutex);
tty->termios->c_cflag =
((tty->termios->c_cflag & ~CLOCAL) |
(arg ? CLOCAL : 0));
mutex_unlock(&tty->termios_mutex);
return 0;
default:
return -ENOIOCTLCMD;
}
}
EXPORT_SYMBOL(n_tty_ioctl);
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