1 files changed, 100 insertions, 25 deletions

diff --git a/drivers/char/n_tty.c b/drivers/char/n_tty.c
index 708c2b1dbe51..efbfe9612658 100644
--- a/drivers/char/n_tty.c
+++ b/drivers/char/n_tty.c
@@ -26,7 +26,7 @@
  *
  * 2002/03/18   Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
  *              waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
- *              Also fixed a bug in BLOCKING mode where write_chan returns
+ *              Also fixed a bug in BLOCKING mode where n_tty_write returns
  *              EAGAIN
  */
 
@@ -99,6 +99,7 @@ static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
 
 static void n_tty_set_room(struct tty_struct *tty)
 {
+        /* tty->read_cnt is not read locked ? */
         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
 
         /*
@@ -121,6 +122,16 @@ static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
         }
 }
 
+/**
+ *      put_tty_queue           -       add character to tty
+ *      @c: character
+ *      @tty: tty device
+ *
+ *      Add a character to the tty read_buf queue. This is done under the
+ *      read_lock to serialize character addition and also to protect us
+ *      against parallel reads or flushes
+ */
+
 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
 {
         unsigned long flags;
@@ -137,14 +148,11 @@ static void put_tty_queue(unsigned char c, struct tty_struct *tty)
  *      check_unthrottle        -       allow new receive data
  *      @tty; tty device
  *
- *      Check whether to call the driver.unthrottle function.
- *      We test the TTY_THROTTLED bit first so that it always
- *      indicates the current state. The decision about whether
- *      it is worth allowing more input has been taken by the caller.
+ *      Check whether to call the driver unthrottle functions
+ *
  *      Can sleep, may be called under the atomic_read_lock mutex but
  *      this is not guaranteed.
  */
-
 static void check_unthrottle(struct tty_struct *tty)
 {
         if (tty->count)
@@ -158,6 +166,8 @@ static void check_unthrottle(struct tty_struct *tty)
  *      Reset the read buffer counters, clear the flags,
  *      and make sure the driver is unthrottled. Called
  *      from n_tty_open() and n_tty_flush_buffer().
+ *
+ *      Locking: tty_read_lock for read fields.
  */
 static void reset_buffer_flags(struct tty_struct *tty)
 {
@@ -181,7 +191,7 @@ static void reset_buffer_flags(struct tty_struct *tty)
  *      at hangup) or when the N_TTY line discipline internally has to
  *      clean the pending queue (for example some signals).
  *
- *      Locking: ctrl_lock
+ *      Locking: ctrl_lock, read_lock.
  */
 
 static void n_tty_flush_buffer(struct tty_struct *tty)
@@ -207,6 +217,8 @@ static void n_tty_flush_buffer(struct tty_struct *tty)
  *
  *      Report the number of characters buffered to be delivered to user
  *      at this instant in time.
+ *
+ *      Locking: read_lock
  */
 
 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
@@ -346,7 +358,7 @@ static int opost(unsigned char c, struct tty_struct *tty)
  *      the simple cases normally found and helps to generate blocks of
  *      symbols for the console driver and thus improve performance.
  *
- *      Called from write_chan under the tty layer write lock. Relies
+ *      Called from n_tty_write under the tty layer write lock. Relies
  *      on lock_kernel for the tty->column state.
  */
 
@@ -410,6 +422,8 @@ break_out:
  *
  *      Echo user input back onto the screen. This must be called only when
  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
+ *
+ *      Relies on BKL for tty column locking
  */
 
 static void echo_char(unsigned char c, struct tty_struct *tty)
@@ -422,6 +436,12 @@ static void echo_char(unsigned char c, struct tty_struct *tty)
                 opost(c, tty);
 }
 
+/**
+ *      finsh_erasing           -       complete erase
+ *      @tty: tty doing the erase
+ *
+ *      Relies on BKL for tty column locking
+ */
 static inline void finish_erasing(struct tty_struct *tty)
 {
         if (tty->erasing) {
@@ -439,6 +459,8 @@ static inline void finish_erasing(struct tty_struct *tty)
  *      Perform erase and necessary output when an erase character is
  *      present in the stream from the driver layer. Handles the complexities
  *      of UTF-8 multibyte symbols.
+ *
+ *      Locking: read_lock for tty buffers, BKL for column/erasing state
  */
 
 static void eraser(unsigned char c, struct tty_struct *tty)
@@ -447,6 +469,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
         int head, seen_alnums, cnt;
         unsigned long flags;
 
+        /* FIXME: locking needed ? */
         if (tty->read_head == tty->canon_head) {
                 /* opost('\a', tty); */         /* what do you think? */
                 return;
@@ -481,6 +504,7 @@ static void eraser(unsigned char c, struct tty_struct *tty)
         }
 
         seen_alnums = 0;
+        /* FIXME: Locking ?? */
         while (tty->read_head != tty->canon_head) {
                 head = tty->read_head;
 
@@ -583,6 +607,8 @@ static void eraser(unsigned char c, struct tty_struct *tty)
  *      may caus terminal flushing to take place according to the termios
  *      settings and character used. Called from the driver receive_buf
  *      path so serialized.
+ *
+ *      Locking: ctrl_lock, read_lock (both via flush buffer)
  */
 
 static inline void isig(int sig, struct tty_struct *tty, int flush)
@@ -1007,12 +1033,26 @@ int is_ignored(int sig)
  *      and is protected from re-entry by the tty layer. The user is
  *      guaranteed that this function will not be re-entered or in progress
  *      when the ldisc is closed.
+ *
+ *      Locking: Caller holds tty->termios_mutex
  */
 
 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
 {
-        if (!tty)
-                return;
+        int canon_change = 1;
+        BUG_ON(!tty);
+
+        if (old)
+                canon_change = (old->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)
+                wake_up_interruptible(&tty->read_wait);
 
         tty->icanon = (L_ICANON(tty) != 0);
         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
@@ -1143,7 +1183,7 @@ static inline int input_available_p(struct tty_struct *tty, int amt)
  *      @b: user data
  *      @nr: size of data
  *
- *      Helper function to speed up read_chan.  It is only called when
+ *      Helper function to speed up n_tty_read.  It is only called when
  *      ICANON is off; it copies characters straight from the tty queue to
  *      user space directly.  It can be profitably called twice; once to
  *      drain the space from the tail pointer to the (physical) end of the
@@ -1210,7 +1250,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
         if (file->f_op->write != redirected_tty_write &&
             current->signal->tty == tty) {
                 if (!tty->pgrp)
-                        printk(KERN_ERR "read_chan: no tty->pgrp!\n");
+                        printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
                 else if (task_pgrp(current) != tty->pgrp) {
                         if (is_ignored(SIGTTIN) ||
                             is_current_pgrp_orphaned())
@@ -1225,7 +1265,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
 
 
 /**
- *      read_chan               -       read function for tty
+ *      n_tty_read              -       read function for tty
  *      @tty: tty device
  *      @file: file object
  *      @buf: userspace buffer pointer
@@ -1239,7 +1279,7 @@ static int job_control(struct tty_struct *tty, struct file *file)
  *      This code must be sure never to sleep through a hangup.
  */
 
-static ssize_t read_chan(struct tty_struct *tty, struct file *file,
+static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
                          unsigned char __user *buf, size_t nr)
 {
         unsigned char __user *b = buf;
@@ -1254,10 +1294,7 @@ static ssize_t read_chan(struct tty_struct *tty, struct file *file,
 
 do_it_again:
 
-        if (!tty->read_buf) {
-                printk(KERN_ERR "n_tty_read_chan: read_buf == NULL?!?\n");
-                return -EIO;
-        }
+        BUG_ON(!tty->read_buf);
 
         c = job_control(tty, file);
         if (c < 0)
@@ -1444,7 +1481,7 @@ do_it_again:
 }
 
 /**
- *      write_chan              -       write function for tty
+ *      n_tty_write             -       write function for tty
  *      @tty: tty device
  *      @file: file object
  *      @buf: userspace buffer pointer
@@ -1458,7 +1495,7 @@ do_it_again:
  *      This code must be sure never to sleep through a hangup.
  */
 
-static ssize_t write_chan(struct tty_struct *tty, struct file *file,
+static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
                           const unsigned char *buf, size_t nr)
 {
         const unsigned char *b = buf;
@@ -1532,7 +1569,7 @@ break_out:
 }
 
 /**
- *      normal_poll             -       poll method for N_TTY
+ *      n_tty_poll              -       poll method for N_TTY
  *      @tty: terminal device
  *      @file: file accessing it
  *      @wait: poll table
@@ -1545,7 +1582,7 @@ break_out:
  *      Called without the kernel lock held - fine
  */
 
-static unsigned int normal_poll(struct tty_struct *tty, struct file *file,
+static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
                                                         poll_table *wait)
 {
         unsigned int mask = 0;
@@ -1573,6 +1610,44 @@ static unsigned int normal_poll(struct tty_struct *tty, struct file *file,
         return mask;
 }
 
+static unsigned long inq_canon(struct tty_struct *tty)
+{
+        int nr, head, tail;
+
+        if (!tty->canon_data)
+                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;
+}
+
+static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
+                       unsigned int cmd, unsigned long arg)
+{
+        int retval;
+
+        switch (cmd) {
+        case TIOCOUTQ:
+                return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
+        case TIOCINQ:
+                /* FIXME: Locking */
+                retval = tty->read_cnt;
+                if (L_ICANON(tty))
+                        retval = inq_canon(tty);
+                return put_user(retval, (unsigned int __user *) arg);
+        default:
+                return n_tty_ioctl_helper(tty, file, cmd, arg);
+        }
+}
+
 struct tty_ldisc_ops tty_ldisc_N_TTY = {
         .magic           = TTY_LDISC_MAGIC,
         .name            = "n_tty",
@@ -1580,11 +1655,11 @@ struct tty_ldisc_ops tty_ldisc_N_TTY = {
         .close           = n_tty_close,
         .flush_buffer    = n_tty_flush_buffer,
         .chars_in_buffer = n_tty_chars_in_buffer,
-        .read            = read_chan,
-        .write           = write_chan,
+        .read            = n_tty_read,
+        .write           = n_tty_write,
         .ioctl           = n_tty_ioctl,
         .set_termios     = n_tty_set_termios,
-        .poll            = normal_poll,
+        .poll            = n_tty_poll,
         .receive_buf     = n_tty_receive_buf,
         .write_wakeup    = n_tty_write_wakeup
 };