tty_io.c

unix/linux 编程实践一书的所有源代码

/*
 *  linux/drivers/char/tty_io.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
 * or rs-channels. It also implements echoing, cooked mode etc.
 *
 * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
 *
 * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
 * tty_struct and tty_queue structures.  Previously there was an array
 * of 256 tty_struct's which was statically allocated, and the
 * tty_queue structures were allocated at boot time.  Both are now
 * dynamically allocated only when the tty is open.
 *
 * Also restructured routines so that there is more of a separation
 * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
 * the low-level tty routines (serial.c, pty.c, console.c).  This
 * makes for cleaner and more compact code.  -TYT, 9/17/92 
 *
 * 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).
 *
 * NOTE: pay no attention to the line discipline code (yet); its
 * interface is still subject to change in this version...
 * -- TYT, 1/31/92
 *
 * Added functionality to the OPOST tty handling.  No delays, but all
 * other bits should be there.
 *	-- Nick Holloway <[e-mail]>, 27th May 1993.
 *
 * Rewrote canonical mode and added more termios flags.
 * 	-- [e-mail] (J. Cowley), 13Jan94
 *
 * Reorganized FASYNC support so mouse code can share it.
 *	-- [e-mail], 9Sep95
 *
 * New TIOCLINUX variants added.
 *	-- [e-mail], 19-Nov-95
 * 
 * Restrict vt switching via ioctl()
 *      -- [e-mail], 5-Dec-95
 *
 * Rewrote init_dev and release_dev to eliminate races.
 *	-- Bill Hawes <[e-mail]>, June 97
 */

#include <linux/config.h>
#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_flip.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/malloc.h>

#include <asm/segment.h>
#include <asm/system.h>
#include <asm/bitops.h>

#include <linux/scc.h>

#include "kbd_kern.h"
#include "vt_kern.h"
#include "selection.h"

#ifdef CONFIG_KERNELD
#include <linux/kerneld.h>
#endif

#define CONSOLE_DEV MKDEV(TTY_MAJOR,0)
#define TTY_DEV MKDEV(TTYAUX_MAJOR,0)

#undef TTY_DEBUG_HANGUP

#define TTY_PARANOIA_CHECK
#define CHECK_TTY_COUNT

extern void do_blank_screen(int nopowersave);
extern void set_vesa_blanking(const unsigned long arg);

struct termios tty_std_termios;		/* for the benefit of tty drivers  */
struct tty_driver *tty_drivers = NULL;	/* linked list of tty drivers */
struct tty_ldisc ldiscs[NR_LDISCS];	/* line disc dispatch table	*/

/*
 * fg_console is the current virtual console,
 * last_console is the last used one,
 * want_console is the console we want to switch to,
 * kmsg_redirect is the console for kernel messages,
 * redirect is the pseudo-tty that console output
 * is redirected to if asked by TIOCCONS.
 */
int fg_console = 0;
int last_console = 0;
int want_console = -1;
int kmsg_redirect = 0;
struct tty_struct * redirect = NULL;
struct wait_queue * keypress_wait = NULL;
char vt_dont_switch = 0;

static void initialize_tty_struct(struct tty_struct *tty);

static int tty_read(struct inode *, struct file *, char *, int);
static int tty_write(struct inode *, struct file *, const char *, int);
static int tty_select(struct inode *, struct file *, int, select_table *);
static int tty_open(struct inode *, struct file *);
static void tty_release(struct inode *, struct file *);
static int tty_ioctl(struct inode * inode, struct file * file,
		     unsigned int cmd, unsigned long arg);
static int tty_fasync(struct inode * inode, struct file * filp, int on);

extern void reset_palette(int currcons) ;
extern void set_palette(void) ;

#ifndef MIN
#define MIN(a,b)	((a) < (b) ? (a) : (b))
#endif

/*
 * These two routines return the name of tty.  tty_name() should NOT
 * be used in interrupt drivers, since it's not re-entrant.  Use
 * _tty_name() instead.
 */
char *_tty_name(struct tty_struct *tty, char *buf)
{
	if (tty)
		sprintf(buf, "%s%d", tty->driver.name,
			MINOR(tty->device) - tty->driver.minor_start +
			tty->driver.name_base);
	else
		strcpy(buf, "NULL tty");
	return buf;
}

char *tty_name(struct tty_struct *tty)
{
	static char buf[64];

	return(_tty_name(tty, buf));
}

inline int tty_paranoia_check(struct tty_struct *tty, kdev_t device,
			      const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
	static const char *badmagic =
		"Warning: bad magic number for tty struct (%s) in %s\n";
	static const char *badtty =
		"Warning: null TTY for (%s) in %s\n";

	if (!tty) {
		printk(badtty, kdevname(device), routine);
		return 1;
	}
	if (tty->magic != TTY_MAGIC) {
		printk(badmagic, kdevname(device), routine);
		return 1;
	}
#endif
	return 0;
}

static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
	struct file *f;
	int i, count = 0;
	
	for (f = first_file, i=0; i<nr_files; i++, f = f->f_next) {
		if (!f->f_count)
			continue;
		if (f->private_data == tty) {
			count++;
		}
	}
	if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver.subtype == PTY_TYPE_SLAVE &&
	    tty->link && tty->link->count)
		count++;
	if (tty->count != count) {
		printk("Warning: dev (%s) tty->count(%d) != #fd's(%d) in %s\n",
		       kdevname(tty->device), tty->count, count, routine);
		return count;
       }	
#endif
	return 0;
}

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;
	
	if (new_ldisc) {
		ldiscs[disc] = *new_ldisc;
		ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
		ldiscs[disc].num = disc;
	} else
		memset(&ldiscs[disc], 0, sizeof(struct tty_ldisc));
	
	return 0;
}

/* Set the discipline of a tty line. */
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int	retval = 0;
	struct	tty_ldisc o_ldisc;

	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
		return -EINVAL;
#ifdef CONFIG_KERNELD
	/* Eduardo Blanco <[e-mail]> */
	if (!(ldiscs[ldisc].flags & LDISC_FLAG_DEFINED)) {
		char modname [20];
		sprintf(modname, "tty-ldisc-%d", ldisc);
		request_module (modname);
	}
#endif
	if (!(ldiscs[ldisc].flags & LDISC_FLAG_DEFINED))
		return -EINVAL;

	if (tty->ldisc.num == ldisc)
		return 0;	/* We are already in the desired discipline */
	o_ldisc = tty->ldisc;

	tty_wait_until_sent(tty, 0);
	
	/* Shutdown the current discipline. */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);

	/* Now set up the new line discipline. */
	tty->ldisc = ldiscs[ldisc];
	tty->termios->c_line = ldisc;
	if (tty->ldisc.open)
		retval = (tty->ldisc.open)(tty);
	if (retval < 0) {
		tty->ldisc = o_ldisc;
		tty->termios->c_line = tty->ldisc.num;
		if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
			tty->ldisc = ldiscs[N_TTY];
			tty->termios->c_line = N_TTY;
			if (tty->ldisc.open) {
				int r = tty->ldisc.open(tty);

				if (r < 0)
					panic("Couldn't open N_TTY ldisc for "
					      "%s --- error %d.",
					      tty_name(tty), r);
			}
		}
	}
	if (tty->ldisc.num != o_ldisc.num && tty->driver.set_ldisc)
		tty->driver.set_ldisc(tty);
	return retval;
}

/*
 * This routine returns a tty driver structure, given a device number
 */
struct tty_driver *get_tty_driver(kdev_t device)
{
	int	major, minor;
	struct tty_driver *p;
	
	minor = MINOR(device);
	major = MAJOR(device);

	for (p = tty_drivers; p; p = p->next) {
		if (p->major != major)
			continue;
		if (minor < p->minor_start)
			continue;
		if (minor >= p->minor_start + p->num)
			continue;
		return p;
	}
	return NULL;
}

/*
 * If we try to write to, or set the state of, a terminal and we're
 * not in the foreground, send a SIGTTOU.  If the signal is blocked or
 * ignored, go ahead and perform the operation.  (POSIX 7.2)
 */
int tty_check_change(struct tty_struct * tty)
{
	if (current->tty != tty)
		return 0;
	if (tty->pgrp <= 0) {
		printk("tty_check_change: tty->pgrp <= 0!\n");
		return 0;
	}
	if (current->pgrp == tty->pgrp)
		return 0;
	if (is_ignored(SIGTTOU))
		return 0;
	if (is_orphaned_pgrp(current->pgrp))
		return -EIO;
	(void) kill_pg(current->pgrp,SIGTTOU,1);
	return -ERESTARTSYS;
}

static int hung_up_tty_read(struct inode * inode, struct file * file, char * buf, int count)
{
	return 0;
}

static int hung_up_tty_write(struct inode * inode, struct file * file, const char * buf, int count)
{
	return -EIO;
}

static int hung_up_tty_select(struct inode * inode, struct file * filp, int sel_type, select_table * wait)
{
	return 1;
}

static int hung_up_tty_ioctl(struct inode * inode, struct file * file,
			     unsigned int cmd, unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static int tty_lseek(struct inode * inode, struct file * file, off_t offset, int orig)
{
	return -ESPIPE;
}

static struct file_operations tty_fops = {
	tty_lseek,
	tty_read,
	tty_write,
	NULL,		/* tty_readdir */
	tty_select,
	tty_ioctl,
	NULL,		/* tty_mmap */
	tty_open,
	tty_release,
	NULL,		/* tty_fsync */
	tty_fasync
};

static struct file_operations hung_up_tty_fops = {
	tty_lseek,
	hung_up_tty_read,
	hung_up_tty_write,
	NULL,		/* hung_up_tty_readdir */
	hung_up_tty_select,
	hung_up_tty_ioctl,
	NULL,		/* hung_up_tty_mmap */
	NULL,		/* hung_up_tty_open */
	tty_release,	/* hung_up_tty_release */
	NULL,		/* hung_up_tty_fsync  */
	NULL		/* hung_up_tty_fasync */
};

void do_tty_hangup(struct tty_struct * tty, struct file_operations *fops)
{
	int i;
	struct file * filp;
	struct task_struct *p;

	if (!tty)
		return;
	check_tty_count(tty, "do_tty_hangup");
	for (filp = first_file, i=0; i<nr_files; i++, filp = filp->f_next) {
		if (!filp->f_count)
			continue;
		if (filp->private_data != tty)
			continue;
		if (!filp->f_inode)
			continue;
		if (filp->f_inode->i_rdev == CONSOLE_DEV)
			continue;
		if (filp->f_op != &tty_fops)
			continue;
		tty_fasync(filp->f_inode, filp, 0);
		filp->f_op = fops;
	}
	
	if (tty->ldisc.flush_buffer)
		tty->ldisc.flush_buffer(tty);
	if (tty->driver.flush_buffer)
		tty->driver.flush_buffer(tty);
	if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
	    tty->ldisc.write_wakeup)
		(tty->ldisc.write_wakeup)(tty);
	wake_up_interruptible(&tty->write_wait);
	wake_up_interruptible(&tty->read_wait);

	/*
	 * Shutdown the current line discipline, and reset it to
	 * N_TTY.
	 */
	if (tty->ldisc.num != ldiscs[N_TTY].num) {
		if (tty->ldisc.close)
			(tty->ldisc.close)(tty);
		tty->ldisc = ldiscs[N_TTY];
		tty->termios->c_line = N_TTY;
		if (tty->ldisc.open) {
			i = (tty->ldisc.open)(tty);
			if (i < 0)
				printk("do_tty_hangup: N_TTY open: error %d\n",
				       -i);
		}
	}
	
 	for_each_task(p) {
		if ((tty->session > 0) && (p->session == tty->session) &&
		    p->leader) {
			send_sig(SIGHUP,p,1);
			send_sig(SIGCONT,p,1);
			if (tty->pgrp > 0)
				p->tty_old_pgrp = tty->pgrp;
		}
		if (p->tty == tty)
			p->tty = NULL;
	}
	tty->flags = 0;
	tty->session = 0;
	tty->pgrp = -1;
	tty->ctrl_status = 0;
	if (tty->driver.flags & TTY_DRIVER_RESET_TERMIOS)
		*tty->termios = tty->driver.init_termios;
	if (tty->driver.hangup)
		(tty->driver.hangup)(tty);
}

void tty_hangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	printk("%s hangup...\n", tty_name(tty));
#endif
	do_tty_hangup(tty, &hung_up_tty_fops);
}

void tty_vhangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	printk("%s vhangup...\n", tty_name(tty));
#endif
	do_tty_hangup(tty, &hung_up_tty_fops);
}

int tty_hung_up_p(struct file * filp)
{
	return (filp->f_op == &hung_up_tty_fops);
}

/*
 * This function is typically called only by the session leader, when
 * it wants to disassociate itself from its controlling tty.
 *
 * It performs the following functions:
 * 	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
 * 	(2)  Clears the tty from being controlling the session
 * 	(3)  Clears the controlling tty for all processes in the
 * 		session group.
 *
 * The argument on_exit is set to 1 if called when a process is
 * exiting; it is 0 if called by the ioctl TIOCNOTTY.
 */
void disassociate_ctty(int on_exit)
{
	struct tty_struct *tty = current->tty;
	struct task_struct *p;
	int tty_pgrp = -1;

	if (tty) {
		tty_pgrp = tty->pgrp;
		if (on_exit && tty->driver.type != TTY_DRIVER_TYPE_PTY)
			tty_vhangup(tty);
	} else {
		if (current->tty_old_pgrp) {
			kill_pg(current->tty_old_pgrp, SIGHUP, on_exit);
			kill_pg(current->tty_old_pgrp, SIGCONT, on_exit);
		}
		return;
	}
	if (tty_pgrp > 0) {
		kill_pg(tty_pgrp, SIGHUP, on_exit);
		if (!on_exit)
			kill_pg(tty_pgrp, SIGCONT, on_exit);
	}

	current->tty_old_pgrp = 0;
	tty->session = 0;
	tty->pgrp = -1;

	for_each_task(p)
	  	if (p->session == current->session)
			p->tty = NULL;
}

/*
 * Sometimes we want to wait until a particular VT has been activated. We
 * do it in a very simple manner. Everybody waits on a single queue and
 * get woken up at once. Those that are satisfied go on with their business,
 * while those not ready go back to sleep. Seems overkill to add a wait
 * to each vt just for this - usually this does nothing!
 */