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Avoid deadlock in tty code if a terminal emulation responds to
type/status/etc inquiries. (PR kern/37915)
This is clearly a design problem in tty, but we need a cheap fix now.
The problem is that ttyinput() tries to pull a spinlock which
is already held on calls to t_oproc.
The workaround is based on the fact that within wscons code, the
wsdisplay_emulinput() function is only called directly from
wsdisplaystart(). So we can be sure that the tty lock is held,
and use an inofficial entry point in ttc.c which avoids the locking.
These ate certainly more assumptions than needed by the fix
proposed in the PR, but it doesn't affect (and slow down) other
tty drivers.

/*	$NetBSD: tty.h,v 1.86 2009/01/22 20:40:20 drochner Exp $	*/

/*-
 * Copyright (c) 2008 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

/*-
 * Copyright (c) 1982, 1986, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)tty.h	8.7 (Berkeley) 1/9/95
 */

#ifndef _SYS_TTY_H_
#define _SYS_TTY_H_

#include <sys/termios.h>
#include <sys/select.h>
#include <sys/selinfo.h>	/* For struct selinfo. */
#include <sys/mutex.h>
#include <sys/condvar.h>
#include <sys/queue.h>
#include <sys/callout.h>

/*
 * Clists are actually ring buffers. The c_cc, c_cf, c_cl fields have
 * exactly the same behaviour as in true clists.
 * if c_cq is NULL, the ring buffer has no TTY_QUOTE functionality
 * (but, saves memory and CPU time)
 *
 * *DON'T* play with c_cs, c_ce, c_cq, or c_cl outside tty_subr.c!!!
 */
struct clist {
	u_char	*c_cf;		/* points to first character */
	u_char	*c_cl;		/* points to next open character */
	u_char	*c_cs;		/* start of ring buffer */
	u_char	*c_ce;		/* c_ce + c_len */
	u_char	*c_cq;		/* N bits/bytes long, see tty_subr.c */
	int	c_cc;		/* count of characters in queue */
	int	c_cn;		/* total ring buffer length */
};

/* tty signal types */
enum ttysigtype {
	TTYSIG_PG1,
	TTYSIG_PG2,
	TTYSIG_LEADER,
	TTYSIG_COUNT
};

/*
 * Per-tty structure.
 *
 * Should be split in two, into device and tty drivers.
 * Glue could be masks of what to echo and circular buffer
 * (low, high, timeout).
 */
struct tty {
	TAILQ_ENTRY(tty) tty_link;	/* Link in global tty list. */
	struct	clist t_rawq;		/* Device raw input queue. */
	long	t_rawcc;		/* Raw input queue statistics. */
	kcondvar_t t_rawcv;		/* notifier */
	kcondvar_t t_rawcvf;		/* notifier */
	struct	clist t_canq;		/* Device canonical queue. */
	long	t_cancc;		/* Canonical queue statistics. */
	kcondvar_t t_cancv;		/* notifier */
	kcondvar_t t_cancvf;		/* notifier */
	struct	clist t_outq;		/* Device output queue. */
	long	t_outcc;		/* Output queue statistics. */
	kcondvar_t t_outcv;		/* notifier */
	kcondvar_t t_outcvf;		/* notifier */
	callout_t t_rstrt_ch;		/* for delayed output start */
	struct	linesw *t_linesw;	/* Interface to device drivers. */
	dev_t	t_dev;			/* Device. */
	int	t_state;		/* Device and driver (TS*) state. */
	int	t_wopen;		/* Processes waiting for open. */
	int	t_flags;		/* Tty flags. */
	struct	pgrp *t_pgrp;		/* Foreground process group. */
	struct	session *t_session;	/* Enclosing session. */
	struct	selinfo t_rsel;		/* Tty read/oob select. */
	struct	selinfo t_wsel;		/* Tty write select. */
	struct	termios t_termios;	/* Termios state. */
	struct	winsize t_winsize;	/* Window size. */
					/* Start output. */
	void	(*t_oproc)(struct tty *);
					/* Set hardware state. */
	int	(*t_param)(struct tty *, struct termios *);
					/* Set hardware flow control. */
	int	(*t_hwiflow)(struct tty *, int);
	void	*t_sc;			/* XXX: net/if_sl.c:sl_softc. */
	short	t_column;		/* Tty output column. */
	short	t_rocount, t_rocol;	/* Tty. */
	short	t_hiwat;		/* High water mark. */
	short	t_lowat;		/* Low water mark. */
	short	t_gen;			/* Generation number. */
	sigset_t t_sigs[TTYSIG_COUNT];	/* Pending signals */
	int	t_sigcount;		/* # pending signals */
	TAILQ_ENTRY(tty) t_sigqueue;	/* entry on pending signal list */
};

#define	t_cc		t_termios.c_cc
#define	t_cflag		t_termios.c_cflag
#define	t_iflag		t_termios.c_iflag
#define	t_ispeed	t_termios.c_ispeed
#define	t_lflag		t_termios.c_lflag
#define	t_oflag		t_termios.c_oflag
#define	t_ospeed	t_termios.c_ospeed

#define	TTIPRI	25			/* Sleep priority for tty reads. */
#define	TTOPRI	26			/* Sleep priority for tty writes. */

#define	TTMASK	15
#define	OBUFSIZ	100
#define	TTYHOG	1024

#ifdef _KERNEL
#define	TTMAXHIWAT	roundup(2048, CBSIZE)
#define	TTMINHIWAT	roundup(100, CBSIZE)
#define	TTMAXLOWAT	256
#define	TTMINLOWAT	32
#endif /* _KERNEL */

/* These flags are kept in t_state. */
#define	TS_SIGINFO	0x00001		/* Ignore mask on dispatch SIGINFO */
#define	TS_ASYNC	0x00002		/* Tty in async I/O mode. */
#define	TS_BUSY		0x00004		/* Draining output. */
#define	TS_CARR_ON	0x00008		/* Carrier is present. */
#define	TS_DIALOUT	0x00010		/* Tty used for dialout. */
#define	TS_FLUSH	0x00020		/* Outq has been flushed during DMA. */
#define	TS_ISOPEN	0x00040		/* Open has completed. */
#define	TS_TBLOCK	0x00080		/* Further input blocked. */
#define	TS_TIMEOUT	0x00100		/* Wait for output char processing. */
#define	TS_TTSTOP	0x00200		/* Output paused. */
#define	TS_XCLUDE	0x00400		/* Tty requires exclusivity. */

/* State for intra-line fancy editing work. */
#define	TS_BKSL		0x00800		/* State for lowercase \ work. */
#define	TS_CNTTB	0x01000		/* Counting tab width, ignore FLUSHO. */
#define	TS_ERASE	0x02000		/* Within a \.../ for PRTRUB. */
#define	TS_LNCH		0x04000		/* Next character is literal. */
#define	TS_TYPEN	0x08000		/* Retyping suspended input (PENDIN). */
#define	TS_LOCAL	(TS_BKSL | TS_CNTTB | TS_ERASE | TS_LNCH | TS_TYPEN)

/* Character type information. */
#define	ORDINARY	0
#define	CONTROL		1
#define	BACKSPACE	2
#define	NEWLINE		3
#define	TAB		4
#define	VTAB		5
#define	RETURN		6

struct speedtab {
	int sp_speed;			/* Speed. */
	int sp_code;			/* Code. */
};

/* Modem control commands (driver). */
#define	DMSET		0
#define	DMBIS		1
#define	DMBIC		2
#define	DMGET		3

/* Flags on a character passed to ttyinput. */
#define	TTY_CHARMASK	0x000000ff	/* Character mask */
#define	TTY_QUOTE	0x00000100	/* Character quoted */
#define	TTY_ERRORMASK	0xff000000	/* Error mask */
#define	TTY_FE		0x01000000	/* Framing error or BREAK condition */
#define	TTY_PE		0x02000000	/* Parity error */

/* Is tp controlling terminal for p? */
#define	isctty(p, tp)							\
	((p)->p_session == (tp)->t_session && (p)->p_lflag & PL_CONTROLT)

/* Is p in background of tp? */
#define	isbackground(p, tp)						\
	(isctty((p), (tp)) && (p)->p_pgrp != (tp)->t_pgrp)

/*
 * ttylist_head is defined here so that user-land has access to it.
 */
TAILQ_HEAD(ttylist_head, tty);		/* the ttylist is a TAILQ */

#ifdef _KERNEL

extern kmutex_t	tty_lock;

extern	int tty_count;			/* number of ttys in global ttylist */
extern	struct ttychars ttydefaults;

/* Symbolic sleep message strings. */
extern	 const char ttclos[];

int	 b_to_q(const u_char *, int, struct clist *);
void	 catq(struct clist *, struct clist *);
void	 clist_init(void);
int	 getc(struct clist *);
void	 ndflush(struct clist *, int);
int	 ndqb(struct clist *, int);
u_char	*nextc(struct clist *, u_char *, int *);
int	 putc(int, struct clist *);
int	 q_to_b(struct clist *, u_char *, int);
int	 unputc(struct clist *);

int	 nullmodem(struct tty *, int);
int	 tputchar(int, int, struct tty *);
int	 ttioctl(struct tty *, u_long, void *, int, struct lwp *);
int	 ttread(struct tty *, struct uio *, int);
void	 ttrstrt(void *);
int	 ttpoll(struct tty *, int, struct lwp *);
void	 ttsetwater(struct tty *);
int	 ttspeedtab(int, const struct speedtab *);
int	 ttstart(struct tty *);
void	 ttwakeup(struct tty *);
int	 ttwrite(struct tty *, struct uio *, int);
void	 ttychars(struct tty *);
int	 ttycheckoutq(struct tty *, int);
int	 ttyclose(struct tty *);
void	 ttyflush(struct tty *, int);
void	 ttygetinfo(struct tty *, int, char *, size_t);
void	 ttyputinfo(struct tty *, char *);
int	 ttyinput(int, struct tty *);
int	 ttyinput_wlock(int, struct tty *); /* XXX see wsdisplay.c */
int	 ttylclose(struct tty *, int);
int	 ttylopen(dev_t, struct tty *);
int	 ttykqfilter(dev_t, struct knote *);
int	 ttymodem(struct tty *, int);
int	 ttyopen(struct tty *, int, int);
int	 ttyoutput(int, struct tty *);
void	 ttypend(struct tty *);
void	 ttyretype(struct tty *);
void	 ttyrub(int, struct tty *);
int	 ttysleep(struct tty *, kcondvar_t *, bool, int);
int	 ttywait(struct tty *);
int	 ttywflush(struct tty *);
void	 ttysig(struct tty *, enum ttysigtype, int);
void	 tty_attach(struct tty *);
void	 tty_detach(struct tty *);
void	 tty_init(void);
struct tty
	*ttymalloc(void);
void	 ttyfree(struct tty *);
u_char	*firstc(struct clist *, int *);
bool	 ttypull(struct tty *);

int	clalloc(struct clist *, int, int);
void	clfree(struct clist *);

extern int (*ttcompatvec)(struct tty *, u_long, void *, int, struct lwp *);

#endif /* _KERNEL */

#endif /* !_SYS_TTY_H_ */