tty_io.c

来自「Linux Kernel 2.6.9 for OMAP1710」· C语言 代码 · 共 2,610 行 · 第 1/5 页

/*
 *  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
 *
 * Move console and virtual terminal code to more appropriate files,
 * implement CONFIG_VT and generalize console device interface.
 *	-- Marko Kohtala <[e-mail]>, March 97
 *
 * Rewrote init_dev and release_dev to eliminate races.
 *	-- Bill Hawes <[e-mail]>, June 97
 *
 * Added devfs support.
 *      -- C. Scott Ananian <[e-mail]>, 13-Jan-1998
 *
 * Added support for a Unix98-style ptmx device.
 *      -- C. Scott Ananian <[e-mail]>, 14-Jan-1998
 *
 * Reduced memory usage for older ARM systems
 *      -- Russell King <[e-mail]>
 *
 * Move do_SAK() into process context.  Less stack use in devfs functions.
 * alloc_tty_struct() always uses kmalloc() -- Andrew Morton <[e-mail]> 17Mar01
 */

#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_driver.h>
#include <linux/tty_flip.h>
#include <linux/devpts_fs.h>
#include <linux/file.h>
#include <linux/console.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/wait.h>

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

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>
#include <linux/devfs_fs_kernel.h>

#include <linux/kmod.h>

#undef TTY_DEBUG_HANGUP

#define TTY_PARANOIA_CHECK 1
#define CHECK_TTY_COUNT 1

struct termios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC
};

EXPORT_SYMBOL(tty_std_termios);

/* This list gets poked at by procfs and various bits of boot up code. This
   could do with some rationalisation such as pulling the tty proc function
   into this file */
   
LIST_HEAD(tty_drivers);			/* linked list of tty drivers */

/* Semaphore to protect creating and releasing a tty. This is shared with
   vt.c for deeply disgusting hack reasons */
DECLARE_MUTEX(tty_sem);

#ifdef CONFIG_UNIX98_PTYS
extern struct tty_driver *ptm_driver;	/* Unix98 pty masters; for /dev/ptmx */
extern int pty_limit;		/* Config limit on Unix98 ptys */
static DEFINE_IDR(allocated_ptys);
static DECLARE_MUTEX(allocated_ptys_lock);
#endif

extern void disable_early_printk(void);

static void initialize_tty_struct(struct tty_struct *tty);

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
ssize_t redirected_tty_write(struct file *, const char __user *, size_t, loff_t *);
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int ptmx_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
int tty_ioctl(struct inode * inode, struct file * file,
	      unsigned int cmd, unsigned long arg);
static int tty_fasync(int fd, struct file * filp, int on);
extern void rs_360_init(void);
static void release_mem(struct tty_struct *tty, int idx);


static struct tty_struct *alloc_tty_struct(void)
{
	struct tty_struct *tty;

	tty = kmalloc(sizeof(struct tty_struct), GFP_KERNEL);
	if (tty)
		memset(tty, 0, sizeof(struct tty_struct));
	return tty;
}

static inline void free_tty_struct(struct tty_struct *tty)
{
	kfree(tty);
}

#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)

char *tty_name(struct tty_struct *tty, char *buf)
{
	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
		strcpy(buf, "NULL tty");
	else
		strcpy(buf, tty->name);
	return buf;
}

EXPORT_SYMBOL(tty_name);

inline int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
			      const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
	if (!tty) {
		printk(KERN_WARNING
			"null TTY for (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
	if (tty->magic != TTY_MAGIC) {
		printk(KERN_WARNING
			"bad magic number for tty struct (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
#endif
	return 0;
}

static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
	struct list_head *p;
	int count = 0;
	
	file_list_lock();
	list_for_each(p, &tty->tty_files) {
		count++;
	}
	file_list_unlock();
	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(KERN_WARNING "Warning: dev (%s) tty->count(%d) "
				    "!= #fd's(%d) in %s\n",
		       tty->name, tty->count, count, routine);
		return count;
       }	
#endif
	return 0;
}

/*
 *	This is probably overkill for real world processors but
 *	they are not on hot paths so a little discipline won't do 
 *	any harm.
 */
 
static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
{
	down(&tty->termios_sem);
	tty->termios->c_line = num;
	up(&tty->termios_sem);
}

/*
 *	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 spinlock_t tty_ldisc_lock = SPIN_LOCK_UNLOCKED;
static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table	*/

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
	unsigned long flags;
	int ret = 0;
	
	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (new_ldisc) {
		tty_ldiscs[disc] = *new_ldisc;
		tty_ldiscs[disc].num = disc;
		tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
		tty_ldiscs[disc].refcount = 0;
	} else {
		if(tty_ldiscs[disc].refcount)
			ret = -EBUSY;
		else
			tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	
	return ret;
}

EXPORT_SYMBOL(tty_register_ldisc);

struct tty_ldisc *tty_ldisc_get(int disc)
{
	unsigned long flags;
	struct tty_ldisc *ld;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return NULL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld = &tty_ldiscs[disc];
	/* Check the entry is defined */
	if(ld->flags & LDISC_FLAG_DEFINED)
	{
		/* If the module is being unloaded we can't use it */
		if (!try_module_get(ld->owner))
		       	ld = NULL;
		else /* lock it */
			ld->refcount++;
	}
	else
		ld = NULL;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ld;
}

EXPORT_SYMBOL_GPL(tty_ldisc_get);

void tty_ldisc_put(int disc)
{
	struct tty_ldisc *ld;
	unsigned long flags;
	
	if (disc < N_TTY || disc >= NR_LDISCS)
		BUG();
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty_ldiscs[disc];
	if(ld->refcount == 0)
		BUG();
	ld->refcount --;
	module_put(ld->owner);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}
	
EXPORT_SYMBOL_GPL(tty_ldisc_put);

void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
{
	tty->ldisc = *ld;
	tty->ldisc.refcount = 0;
}

/**
 *	tty_ldisc_try		-	internal helper
 *	@tty: the tty
 *
 *	Make a single attempt to grab and bump the refcount on
 *	the tty ldisc. Return 0 on failure or 1 on success. This is
 *	used to implement both the waiting and non waiting versions
 *	of tty_ldisc_ref
 */

static int tty_ldisc_try(struct tty_struct *tty)
{
	unsigned long flags;
	struct tty_ldisc *ld;
	int ret = 0;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty->ldisc;
	if(test_bit(TTY_LDISC, &tty->flags))
	{
		ld->refcount++;
		ret = 1;
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ret;
}

/**
 *	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.
 *
 *	Note: 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)
 */
 
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
	/* wait_event is a macro */
	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
	if(tty->ldisc.refcount == 0)
		printk(KERN_ERR "tty_ldisc_ref_wait\n");
	return &tty->ldisc;
}

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)
{
	if(tty_ldisc_try(tty))
		return &tty->ldisc;
	return NULL;
}

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)
{
	unsigned long flags;

	if(ld == NULL)
		BUG();
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if(ld->refcount == 0)
		printk(KERN_ERR "tty_ldisc_deref: no references.\n");
	else
		ld->refcount--;
	if(ld->refcount == 0)
		wake_up(&tty_ldisc_wait);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}

EXPORT_SYMBOL_GPL(tty_ldisc_deref);

/**
 *	tty_ldisc_enable	-	allow ldisc use
 *	@tty: terminal to activate ldisc on
 *
 *	Set the TTY_LDISC flag when the line discipline can be called
 *	again. Do neccessary wakeups for existing sleepers.
 *
 *	Note: nobody should set this bit except via this function. Clearing
 *	directly is allowed.
 */

static void tty_ldisc_enable(struct tty_struct *tty)
{
	set_bit(TTY_LDISC, &tty->flags);
	wake_up(&tty_ldisc_wait);
}
	
/**
 *	tty_set_ldisc		-	set line discipline
 *	@tty: the terminal to set
 *	@ldisc: the line discipline
 *
 *	Set the discipline of a tty line. Must be called from a process
 *	context.
 */
 
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int	retval = 0;
	struct	tty_ldisc o_ldisc;
	char buf[64];
	int work;
	unsigned long flags;
	struct tty_ldisc *ld;

	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
		return -EINVAL;

restart:

	if (tty->ldisc.num == ldisc)
		return 0;	/* We are already in the desired discipline */
	
	ld = tty_ldisc_get(ldisc);
	/* Eduardo Blanco <[e-mail]> */
	/* Cyrus Durgin <[e-mail]> */
	if (ld == NULL) {
		request_module("tty-ldisc-%d", ldisc);
		ld = tty_ldisc_get(ldisc);
	}
	if (ld == NULL)
		return -EINVAL;

	o_ldisc = tty->ldisc;

	tty_wait_until_sent(tty, 0);

	/*
	 *	Make sure we don't change while someone holds a
	 *	reference to the line discipline. The TTY_LDISC bit
	 *	prevents anyone taking a reference once it is clear.
	 *	We need the lock to avoid racing reference takers.
	 */
	 
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if(tty->ldisc.refcount)
	{
		/* Free the new ldisc we grabbed. Must drop the lock
		   first. */
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		tty_ldisc_put(ldisc);
		/*
		 * There are several reasons we may be busy, including
		 * random momentary I/O traffic. We must therefore
		 * retry. We could distinguish between blocking ops
		 * and retries if we made tty_ldisc_wait() smarter. That
		 * is up for discussion.
		 */
		if(wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
			return -ERESTARTSYS;			
		goto restart;
	}
	clear_bit(TTY_LDISC, &tty->flags);	
	clear_bit(TTY_DONT_FLIP, &tty->flags);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	
	/*
	 *	From this point on we know nobody has an ldisc
	 *	usage reference, nor can they obtain one until
	 *	we say so later on.
	 */