/* * linux/drivers/char/pty.c * * Copyright (C) 1991, 1992 Linus Torvalds * * Added support for a Unix98-style ptmx device. * -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998 * Added TTY_DO_WRITE_WAKEUP to enable n_tty to send POLL_OUT to * waiting writers -- Sapan Bhatia <sapan@corewars.org> * * */ #include <linux/config.h> #include <linux/module.h> /* For EXPORT_SYMBOL */ #include <linux/errno.h> #include <linux/sched.h> #include <linux/interrupt.h> #include <linux/tty.h> #include <linux/tty_flip.h> #include <linux/fcntl.h> #include <linux/string.h> #include <linux/major.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/devfs_fs_kernel.h> #include <linux/sysctl.h> #include <asm/uaccess.h> #include <asm/system.h> #include <linux/bitops.h> #include <linux/devpts_fs.h> /* These are global because they are accessed in tty_io.c */ #ifdef CONFIG_UNIX98_PTYS struct tty_driver *ptm_driver; static struct tty_driver *pts_driver; #endif static void pty_close(struct tty_struct * tty, struct file * filp) { if (!tty) return; if (tty->driver->subtype == PTY_TYPE_MASTER) { if (tty->count > 1) printk("master pty_close: count = %d!!\n", tty->count); } else { if (tty->count > 2) return; } wake_up_interruptible(&tty->read_wait); wake_up_interruptible(&tty->write_wait); tty->packet = 0; if (!tty->link) return; tty->link->packet = 0; set_bit(TTY_OTHER_CLOSED, &tty->link->flags); wake_up_interruptible(&tty->link->read_wait); wake_up_interruptible(&tty->link->write_wait); if (tty->driver->subtype == PTY_TYPE_MASTER) { set_bit(TTY_OTHER_CLOSED, &tty->flags); #ifdef CONFIG_UNIX98_PTYS if (tty->driver == ptm_driver) devpts_pty_kill(tty->index); #endif tty_vhangup(tty->link); } } /* * The unthrottle routine is called by the line discipline to signal * that it can receive more characters. For PTY's, the TTY_THROTTLED * flag is always set, to force the line discipline to always call the * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE * characters in the queue. This is necessary since each time this * happens, we need to wake up any sleeping processes that could be * (1) trying to send data to the pty, or (2) waiting in wait_until_sent() * for the pty buffer to be drained. */ static void pty_unthrottle(struct tty_struct * tty) { struct tty_struct *o_tty = tty->link; if (!o_tty) return; tty_wakeup(o_tty); set_bit(TTY_THROTTLED, &tty->flags); } /* * WSH 05/24/97: modified to * (1) use space in tty->flip instead of a shared temp buffer * The flip buffers aren't being used for a pty, so there's lots * of space available. The buffer is protected by a per-pty * semaphore that should almost never come under contention. * (2) avoid redundant copying for cases where count >> receive_room * N.B. Calls from user space may now return an error code instead of * a count. * * FIXME: Our pty_write method is called with our ldisc lock held but * not our partners. We can't just take the other one blindly without * risking deadlocks. There is also the small matter of TTY_DONT_FLIP */ static int pty_write(struct tty_struct * tty, const unsigned char *buf, int count) { struct tty_struct *to = tty->link; int c; if (!to || tty->stopped) return 0; c = to->ldisc.receive_room(to); if (c > count) c = count; to->ldisc.receive_buf(to, buf, NULL, c); return c; } static int pty_write_room(struct tty_struct *tty) { struct tty_struct *to = tty->link; if (!to || tty->stopped) return 0; return to->ldisc.receive_room(to); } /* * WSH 05/24/97: Modified for asymmetric MASTER/SLAVE behavior * The chars_in_buffer() value is used by the ldisc select() function * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256). * The pty driver chars_in_buffer() Master/Slave must behave differently: * * The Master side needs to allow typed-ahead commands to accumulate * while being canonicalized, so we report "our buffer" as empty until * some threshold is reached, and then report the count. (Any count > * WAKEUP_CHARS is regarded by select() as "full".) To avoid deadlock * the count returned must be 0 if no canonical data is available to be * read. (The N_TTY ldisc.chars_in_buffer now knows this.) * * The Slave side passes all characters in raw mode to the Master side's * buffer where they can be read immediately, so in this case we can * return the true count in the buffer. */ static int pty_chars_in_buffer(struct tty_struct *tty) { struct tty_struct *to = tty->link; int count; /* We should get the line discipline lock for "tty->link" */ if (!to || !to->ldisc.chars_in_buffer) return 0; /* The ldisc must report 0 if no characters available to be read */ count = to->ldisc.chars_in_buffer(to); if (tty->driver->subtype == PTY_TYPE_SLAVE) return count; /* Master side driver ... if the other side's read buffer is less than * half full, return 0 to allow writers to proceed; otherwise return * the count. This leaves a comfortable margin to avoid overflow, * and still allows half a buffer's worth of typed-ahead commands. */ return ((count < N_TTY_BUF_SIZE/2) ? 0 : count); } /* Set the lock flag on a pty */ static int pty_set_lock(struct tty_struct *tty, int __user * arg) { int val; if (get_user(val,arg)) return -EFAULT; if (val) set_bit(TTY_PTY_LOCK, &tty->flags); else clear_bit(TTY_PTY_LOCK, &tty->flags); return 0; } static void pty_flush_buffer(struct tty_struct *tty) { struct tty_struct *to = tty->link; if (!to) return; if (to->ldisc.flush_buffer) to->ldisc.flush_buffer(to); if (to->packet) { tty->ctrl_status |= TIOCPKT_FLUSHWRITE; wake_up_interruptible(&to->read_wait); } } static int pty_open(struct tty_struct *tty, struct file * filp) { int retval = -ENODEV; if (!tty || !tty->link) goto out; retval = -EIO; if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) goto out; if (test_bit(TTY_PTY_LOCK, &tty->link->flags)) goto out; if (tty->link->count != 1) goto out; clear_bit(TTY_OTHER_CLOSED, &tty->link->flags); set_bit(TTY_THROTTLED, &tty->flags); set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags); retval = 0; out: return retval; } static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios) { tty->termios->c_cflag &= ~(CSIZE | PARENB); tty->termios->c_cflag |= (CS8 | CREAD); } static struct tty_operations pty_ops = { .open = pty_open, .close = pty_close, .write = pty_write, .write_room = pty_write_room, .flush_buffer = pty_flush_buffer, .chars_in_buffer = pty_chars_in_buffer, .unthrottle = pty_unthrottle, .set_termios = pty_set_termios, }; /* Traditional BSD devices */ #ifdef CONFIG_LEGACY_PTYS static struct tty_driver *pty_driver, *pty_slave_driver; static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { switch (cmd) { case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ return pty_set_lock(tty, (int __user *) arg); } return -ENOIOCTLCMD; } static void __init legacy_pty_init(void) { pty_driver = alloc_tty_driver(NR_PTYS); if (!pty_driver) panic("Couldn't allocate pty driver"); pty_slave_driver = alloc_tty_driver(NR_PTYS); if (!pty_slave_driver) panic("Couldn't allocate pty slave driver"); pty_driver->owner = THIS_MODULE; pty_driver->driver_name = "pty_master"; pty_driver->name = "pty"; pty_driver->devfs_name = "pty/m"; pty_driver->major = PTY_MASTER_MAJOR; pty_driver->minor_start = 0; pty_driver->type = TTY_DRIVER_TYPE_PTY; pty_driver->subtype = PTY_TYPE_MASTER; pty_driver->init_termios = tty_std_termios; pty_driver->init_termios.c_iflag = 0; pty_driver->init_termios.c_oflag = 0; pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; pty_driver->init_termios.c_lflag = 0; pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW; pty_driver->other = pty_slave_driver; tty_set_operations(pty_driver, &pty_ops); pty_driver->ioctl = pty_bsd_ioctl; pty_slave_driver->owner = THIS_MODULE; pty_slave_driver->driver_name = "pty_slave"; pty_slave_driver->name = "ttyp"; pty_slave_driver->devfs_name = "pty/s"; pty_slave_driver->major = PTY_SLAVE_MAJOR; pty_slave_driver->minor_start = 0; pty_slave_driver->type = TTY_DRIVER_TYPE_PTY; pty_slave_driver->subtype = PTY_TYPE_SLAVE; pty_slave_driver->init_termios = tty_std_termios; pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW; pty_slave_driver->other = pty_driver; tty_set_operations(pty_slave_driver, &pty_ops); if (tty_register_driver(pty_driver)) panic("Couldn't register pty driver"); if (tty_register_driver(pty_slave_driver)) panic("Couldn't register pty slave driver"); } #else static inline void legacy_pty_init(void) { } #endif /* Unix98 devices */ #ifdef CONFIG_UNIX98_PTYS /* * sysctl support for setting limits on the number of Unix98 ptys allocated. * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly. */ int pty_limit = NR_UNIX98_PTY_DEFAULT; static int pty_limit_min = 0; static int pty_limit_max = NR_UNIX98_PTY_MAX; ctl_table pty_table[] = { { .ctl_name = PTY_MAX, .procname = "max", .maxlen = sizeof(int), .mode = 0644, .data = &pty_limit, .proc_handler = &proc_dointvec_minmax, .strategy = &sysctl_intvec, .extra1 = &pty_limit_min, .extra2 = &pty_limit_max, }, { .ctl_name = PTY_NR, .procname = "nr", .maxlen = sizeof(int), .mode = 0444, .proc_handler = &proc_dointvec, }, { .ctl_name = 0 } }; static int pty_unix98_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg) { switch (cmd) { case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */ return pty_set_lock(tty, (int __user *)arg); case TIOCGPTN: /* Get PT Number */ return put_user(tty->index, (unsigned int __user *)arg); } return -ENOIOCTLCMD; } static void __init unix98_pty_init(void) { devfs_mk_dir("pts"); ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX); if (!ptm_driver) panic("Couldn't allocate Unix98 ptm driver"); pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX); if (!pts_driver) panic("Couldn't allocate Unix98 pts driver"); ptm_driver->owner = THIS_MODULE; ptm_driver->driver_name = "pty_master"; ptm_driver->name = "ptm"; ptm_driver->major = UNIX98_PTY_MASTER_MAJOR; ptm_driver->minor_start = 0; ptm_driver->type = TTY_DRIVER_TYPE_PTY; ptm_driver->subtype = PTY_TYPE_MASTER; ptm_driver->init_termios = tty_std_termios; ptm_driver->init_termios.c_iflag = 0; ptm_driver->init_termios.c_oflag = 0; ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; ptm_driver->init_termios.c_lflag = 0; ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM; ptm_driver->other = pts_driver; tty_set_operations(ptm_driver, &pty_ops); ptm_driver->ioctl = pty_unix98_ioctl; pts_driver->owner = THIS_MODULE; pts_driver->driver_name = "pty_slave"; pts_driver->name = "pts"; pts_driver->major = UNIX98_PTY_SLAVE_MAJOR; pts_driver->minor_start = 0; pts_driver->type = TTY_DRIVER_TYPE_PTY; pts_driver->subtype = PTY_TYPE_SLAVE; pts_driver->init_termios = tty_std_termios; pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD; pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW | TTY_DRIVER_NO_DEVFS | TTY_DRIVER_DEVPTS_MEM; pts_driver->other = ptm_driver; tty_set_operations(pts_driver, &pty_ops); if (tty_register_driver(ptm_driver)) panic("Couldn't register Unix98 ptm driver"); if (tty_register_driver(pts_driver)) panic("Couldn't register Unix98 pts driver"); pty_table[1].data = &ptm_driver->refcount; } #else static inline void unix98_pty_init(void) { } #endif static int __init pty_init(void) { legacy_pty_init(); unix98_pty_init(); return 0; } module_init(pty_init);