xref: /freebsd/sys/kern/subr_terminal.c (revision 38effe887ee979f91ad5abf42a2291558e7ff8d1) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2009 The FreeBSD Foundation
5  * All rights reserved.
6  *
7  * This software was developed by Ed Schouten under sponsorship from the
8  * FreeBSD Foundation.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include <sys/param.h>
36 #include <sys/cons.h>
37 #include <sys/consio.h>
38 #include <sys/kernel.h>
39 #include <sys/lock.h>
40 #include <sys/malloc.h>
41 #include <sys/mutex.h>
42 #include <sys/systm.h>
43 #include <sys/terminal.h>
44 #include <sys/tty.h>
45 
46 #include <machine/stdarg.h>
47 
48 static MALLOC_DEFINE(M_TERMINAL, "terminal", "terminal device");
49 
50 /*
51  * Locking.
52  *
53  * Normally we don't need to lock down the terminal emulator, because
54  * the TTY lock is already held when calling teken_input().
55  * Unfortunately this is not the case when the terminal acts as a
56  * console device, because cnputc() can be called at the same time.
57  * This means terminals may need to be locked down using a spin lock.
58  */
59 #define	TERMINAL_LOCK(tm)	do {					\
60 	if ((tm)->tm_flags & TF_CONS)					\
61 		mtx_lock_spin(&(tm)->tm_mtx);				\
62 	else if ((tm)->tm_tty != NULL)					\
63 		tty_lock((tm)->tm_tty);					\
64 } while (0)
65 #define	TERMINAL_UNLOCK(tm)	do {					\
66 	if ((tm)->tm_flags & TF_CONS)					\
67 		mtx_unlock_spin(&(tm)->tm_mtx);				\
68 	else if ((tm)->tm_tty != NULL)					\
69 		tty_unlock((tm)->tm_tty);				\
70 } while (0)
71 #define	TERMINAL_LOCK_TTY(tm)	do {					\
72 	if ((tm)->tm_flags & TF_CONS)					\
73 		mtx_lock_spin(&(tm)->tm_mtx);				\
74 } while (0)
75 #define	TERMINAL_UNLOCK_TTY(tm)	do {					\
76 	if ((tm)->tm_flags & TF_CONS)					\
77 		mtx_unlock_spin(&(tm)->tm_mtx);				\
78 } while (0)
79 #define	TERMINAL_LOCK_CONS(tm)		mtx_lock_spin(&(tm)->tm_mtx)
80 #define	TERMINAL_UNLOCK_CONS(tm)	mtx_unlock_spin(&(tm)->tm_mtx)
81 
82 /*
83  * TTY routines.
84  */
85 
86 static tsw_open_t	termtty_open;
87 static tsw_close_t	termtty_close;
88 static tsw_outwakeup_t	termtty_outwakeup;
89 static tsw_ioctl_t	termtty_ioctl;
90 static tsw_mmap_t	termtty_mmap;
91 
92 static struct ttydevsw terminal_tty_class = {
93 	.tsw_open	= termtty_open,
94 	.tsw_close	= termtty_close,
95 	.tsw_outwakeup	= termtty_outwakeup,
96 	.tsw_ioctl	= termtty_ioctl,
97 	.tsw_mmap	= termtty_mmap,
98 };
99 
100 /*
101  * Terminal emulator routines.
102  */
103 
104 static tf_bell_t	termteken_bell;
105 static tf_cursor_t	termteken_cursor;
106 static tf_putchar_t	termteken_putchar;
107 static tf_fill_t	termteken_fill;
108 static tf_copy_t	termteken_copy;
109 static tf_pre_input_t	termteken_pre_input;
110 static tf_post_input_t	termteken_post_input;
111 static tf_param_t	termteken_param;
112 static tf_respond_t	termteken_respond;
113 
114 static teken_funcs_t terminal_drawmethods = {
115 	.tf_bell	= termteken_bell,
116 	.tf_cursor	= termteken_cursor,
117 	.tf_putchar	= termteken_putchar,
118 	.tf_fill	= termteken_fill,
119 	.tf_copy	= termteken_copy,
120 	.tf_pre_input	= termteken_pre_input,
121 	.tf_post_input	= termteken_post_input,
122 	.tf_param	= termteken_param,
123 	.tf_respond	= termteken_respond,
124 };
125 
126 /* Kernel message formatting. */
127 static teken_attr_t kernel_message = {
128 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_KERN_ATTR),
129 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_KERN_ATTR),
130 	.ta_format	= TCHAR_FORMAT(TERMINAL_KERN_ATTR)
131 };
132 
133 static teken_attr_t default_message = {
134 	.ta_fgcolor	= TCHAR_FGCOLOR(TERMINAL_NORM_ATTR),
135 	.ta_bgcolor	= TCHAR_BGCOLOR(TERMINAL_NORM_ATTR),
136 	.ta_format	= TCHAR_FORMAT(TERMINAL_NORM_ATTR)
137 };
138 
139 /* Fudge fg brightness as TF_BOLD (shifted). */
140 #define	TCOLOR_FG_FUDGED(color) __extension__ ({			\
141 	teken_color_t _c;						\
142 									\
143 	_c = (color);							\
144 	TCOLOR_FG(_c & 7) | ((_c & 8) << 18);				\
145 })
146 
147 /* Fudge bg brightness as TF_BLINK (shifted). */
148 #define	TCOLOR_BG_FUDGED(color) __extension__ ({			\
149 	teken_color_t _c;						\
150 									\
151 	_c = (color);							\
152 	TCOLOR_BG(_c & 7) | ((_c & 8) << 20);				\
153 })
154 
155 #define	TCOLOR_256TO16(color) __extension__ ({				\
156 	teken_color_t _c;						\
157 									\
158 	_c = (color);							\
159 	if (_c >= 16)							\
160 		_c = teken_256to16(_c);					\
161 	_c;								\
162 })
163 
164 #define	TCHAR_CREATE(c, a)	((c) | TFORMAT((a)->ta_format) |	\
165 	TCOLOR_FG_FUDGED(TCOLOR_256TO16((a)->ta_fgcolor)) |		\
166 	TCOLOR_BG_FUDGED(TCOLOR_256TO16((a)->ta_bgcolor)))
167 
168 static void
169 terminal_init(struct terminal *tm)
170 {
171 	int fg, bg;
172 
173 	if (tm->tm_flags & TF_CONS)
174 		mtx_init(&tm->tm_mtx, "trmlck", NULL, MTX_SPIN);
175 
176 	teken_init(&tm->tm_emulator, &terminal_drawmethods, tm);
177 
178 	fg = bg = -1;
179 	TUNABLE_INT_FETCH("teken.fg_color", &fg);
180 	TUNABLE_INT_FETCH("teken.bg_color", &bg);
181 
182 	if (fg != -1) {
183 		default_message.ta_fgcolor = fg;
184 		kernel_message.ta_fgcolor = fg;
185 	}
186 	if (bg != -1) {
187 		default_message.ta_bgcolor = bg;
188 		kernel_message.ta_bgcolor = bg;
189 	}
190 
191 	if (default_message.ta_bgcolor == TC_WHITE) {
192 		default_message.ta_bgcolor |= TC_LIGHT;
193 		kernel_message.ta_bgcolor |= TC_LIGHT;
194 	}
195 
196 	if (default_message.ta_bgcolor == TC_BLACK &&
197 	    default_message.ta_fgcolor < TC_NCOLORS)
198 		kernel_message.ta_fgcolor |= TC_LIGHT;
199 	teken_set_defattr(&tm->tm_emulator, &default_message);
200 }
201 
202 struct terminal *
203 terminal_alloc(const struct terminal_class *tc, void *softc)
204 {
205 	struct terminal *tm;
206 
207 	tm = malloc(sizeof(struct terminal), M_TERMINAL, M_WAITOK|M_ZERO);
208 	terminal_init(tm);
209 
210 	tm->tm_class = tc;
211 	tm->tm_softc = softc;
212 
213 	return (tm);
214 }
215 
216 static void
217 terminal_sync_ttysize(struct terminal *tm)
218 {
219 	struct tty *tp;
220 
221 	tp = tm->tm_tty;
222 	if (tp == NULL)
223 		return;
224 
225 	tty_lock(tp);
226 	tty_set_winsize(tp, &tm->tm_winsize);
227 	tty_unlock(tp);
228 }
229 
230 void
231 terminal_maketty(struct terminal *tm, const char *fmt, ...)
232 {
233 	struct tty *tp;
234 	char name[8];
235 	va_list ap;
236 
237 	va_start(ap, fmt);
238 	vsnrprintf(name, sizeof name, 32, fmt, ap);
239 	va_end(ap);
240 
241 	tp = tty_alloc(&terminal_tty_class, tm);
242 	tty_makedev(tp, NULL, "%s", name);
243 	tm->tm_tty = tp;
244 	terminal_sync_ttysize(tm);
245 }
246 
247 void
248 terminal_set_cursor(struct terminal *tm, const term_pos_t *pos)
249 {
250 
251 	teken_set_cursor(&tm->tm_emulator, pos);
252 }
253 
254 void
255 terminal_set_winsize_blank(struct terminal *tm, const struct winsize *size,
256     int blank, const term_attr_t *attr)
257 {
258 	term_rect_t r;
259 
260 	tm->tm_winsize = *size;
261 
262 	r.tr_begin.tp_row = r.tr_begin.tp_col = 0;
263 	r.tr_end.tp_row = size->ws_row;
264 	r.tr_end.tp_col = size->ws_col;
265 
266 	TERMINAL_LOCK(tm);
267 	if (blank == 0)
268 		teken_set_winsize_noreset(&tm->tm_emulator, &r.tr_end);
269 	else
270 		teken_set_winsize(&tm->tm_emulator, &r.tr_end);
271 	TERMINAL_UNLOCK(tm);
272 
273 	if ((blank != 0) && !(tm->tm_flags & TF_MUTE))
274 		tm->tm_class->tc_fill(tm, &r,
275 		    TCHAR_CREATE((teken_char_t)' ', attr));
276 
277 	terminal_sync_ttysize(tm);
278 }
279 
280 void
281 terminal_set_winsize(struct terminal *tm, const struct winsize *size)
282 {
283 
284 	terminal_set_winsize_blank(tm, size, 1,
285 	    (const term_attr_t *)&default_message);
286 }
287 
288 /*
289  * XXX: This function is a kludge.  Drivers like vt(4) need to
290  * temporarily stop input when resizing, etc.  This should ideally be
291  * handled within the driver.
292  */
293 
294 void
295 terminal_mute(struct terminal *tm, int yes)
296 {
297 
298 	TERMINAL_LOCK(tm);
299 	if (yes)
300 		tm->tm_flags |= TF_MUTE;
301 	else
302 		tm->tm_flags &= ~TF_MUTE;
303 	TERMINAL_UNLOCK(tm);
304 }
305 
306 void
307 terminal_input_char(struct terminal *tm, term_char_t c)
308 {
309 	struct tty *tp;
310 
311 	tp = tm->tm_tty;
312 	if (tp == NULL)
313 		return;
314 
315 	/*
316 	 * Strip off any attributes. Also ignore input of second part of
317 	 * CJK fullwidth characters, as we don't want to return these
318 	 * characters twice.
319 	 */
320 	if (TCHAR_FORMAT(c) & TF_CJK_RIGHT)
321 		return;
322 	c = TCHAR_CHARACTER(c);
323 
324 	tty_lock(tp);
325 	/*
326 	 * Conversion to UTF-8.
327 	 */
328 	if (c < 0x80) {
329 		ttydisc_rint(tp, c, 0);
330 	} else if (c < 0x800) {
331 		char str[2] = {
332 			0xc0 | (c >> 6),
333 			0x80 | (c & 0x3f)
334 		};
335 
336 		ttydisc_rint_simple(tp, str, sizeof str);
337 	} else if (c < 0x10000) {
338 		char str[3] = {
339 			0xe0 | (c >> 12),
340 			0x80 | ((c >> 6) & 0x3f),
341 			0x80 | (c & 0x3f)
342 		};
343 
344 		ttydisc_rint_simple(tp, str, sizeof str);
345 	} else {
346 		char str[4] = {
347 			0xf0 | (c >> 18),
348 			0x80 | ((c >> 12) & 0x3f),
349 			0x80 | ((c >> 6) & 0x3f),
350 			0x80 | (c & 0x3f)
351 		};
352 
353 		ttydisc_rint_simple(tp, str, sizeof str);
354 	}
355 	ttydisc_rint_done(tp);
356 	tty_unlock(tp);
357 }
358 
359 void
360 terminal_input_raw(struct terminal *tm, char c)
361 {
362 	struct tty *tp;
363 
364 	tp = tm->tm_tty;
365 	if (tp == NULL)
366 		return;
367 
368 	tty_lock(tp);
369 	ttydisc_rint(tp, c, 0);
370 	ttydisc_rint_done(tp);
371 	tty_unlock(tp);
372 }
373 
374 void
375 terminal_input_special(struct terminal *tm, unsigned int k)
376 {
377 	struct tty *tp;
378 	const char *str;
379 
380 	tp = tm->tm_tty;
381 	if (tp == NULL)
382 		return;
383 
384 	str = teken_get_sequence(&tm->tm_emulator, k);
385 	if (str == NULL)
386 		return;
387 
388 	tty_lock(tp);
389 	ttydisc_rint_simple(tp, str, strlen(str));
390 	ttydisc_rint_done(tp);
391 	tty_unlock(tp);
392 }
393 
394 /*
395  * Binding with the TTY layer.
396  */
397 
398 static int
399 termtty_open(struct tty *tp)
400 {
401 	struct terminal *tm = tty_softc(tp);
402 
403 	tm->tm_class->tc_opened(tm, 1);
404 	return (0);
405 }
406 
407 static void
408 termtty_close(struct tty *tp)
409 {
410 	struct terminal *tm = tty_softc(tp);
411 
412 	tm->tm_class->tc_opened(tm, 0);
413 }
414 
415 static void
416 termtty_outwakeup(struct tty *tp)
417 {
418 	struct terminal *tm = tty_softc(tp);
419 	char obuf[128];
420 	size_t olen;
421 	unsigned int flags = 0;
422 
423 	while ((olen = ttydisc_getc(tp, obuf, sizeof obuf)) > 0) {
424 		TERMINAL_LOCK_TTY(tm);
425 		if (!(tm->tm_flags & TF_MUTE)) {
426 			tm->tm_flags &= ~TF_BELL;
427 			teken_input(&tm->tm_emulator, obuf, olen);
428 			flags |= tm->tm_flags;
429 		}
430 		TERMINAL_UNLOCK_TTY(tm);
431 	}
432 
433 	TERMINAL_LOCK_TTY(tm);
434 	if (!(tm->tm_flags & TF_MUTE))
435 		tm->tm_class->tc_done(tm);
436 	TERMINAL_UNLOCK_TTY(tm);
437 	if (flags & TF_BELL)
438 		tm->tm_class->tc_bell(tm);
439 }
440 
441 static int
442 termtty_ioctl(struct tty *tp, u_long cmd, caddr_t data, struct thread *td)
443 {
444 	struct terminal *tm = tty_softc(tp);
445 	int error;
446 
447 	switch (cmd) {
448 	case CONS_GETINFO: {
449 		vid_info_t *vi = (vid_info_t *)data;
450 		const teken_pos_t *p;
451 		int fg, bg;
452 
453 		if (vi->size != sizeof(vid_info_t))
454 			return (EINVAL);
455 
456 		/* Already help the console driver by filling in some data. */
457 		p = teken_get_cursor(&tm->tm_emulator);
458 		vi->mv_row = p->tp_row;
459 		vi->mv_col = p->tp_col;
460 
461 		p = teken_get_winsize(&tm->tm_emulator);
462 		vi->mv_rsz = p->tp_row;
463 		vi->mv_csz = p->tp_col;
464 
465 		teken_get_defattr_cons25(&tm->tm_emulator, &fg, &bg);
466 		vi->mv_norm.fore = fg;
467 		vi->mv_norm.back = bg;
468 		/* XXX: keep vidcontrol happy; bold backgrounds. */
469 		vi->mv_rev.fore = bg;
470 		vi->mv_rev.back = fg & 0x7;
471 		break;
472 	}
473 	}
474 
475 	/*
476 	 * Unlike various other drivers, this driver will never
477 	 * deallocate TTYs.  This means it's safe to temporarily unlock
478 	 * the TTY when handling ioctls.
479 	 */
480 	tty_unlock(tp);
481 	error = tm->tm_class->tc_ioctl(tm, cmd, data, td);
482 	tty_lock(tp);
483 	return (error);
484 }
485 
486 static int
487 termtty_mmap(struct tty *tp, vm_ooffset_t offset, vm_paddr_t * paddr,
488     int nprot, vm_memattr_t *memattr)
489 {
490 	struct terminal *tm = tty_softc(tp);
491 
492 	return (tm->tm_class->tc_mmap(tm, offset, paddr, nprot, memattr));
493 }
494 
495 /*
496  * Binding with the kernel and debug console.
497  */
498 
499 static cn_probe_t	termcn_cnprobe;
500 static cn_init_t	termcn_cninit;
501 static cn_term_t	termcn_cnterm;
502 static cn_getc_t	termcn_cngetc;
503 static cn_putc_t	termcn_cnputc;
504 static cn_grab_t	termcn_cngrab;
505 static cn_ungrab_t	termcn_cnungrab;
506 
507 const struct consdev_ops termcn_cnops = {
508 	.cn_probe	= termcn_cnprobe,
509 	.cn_init	= termcn_cninit,
510 	.cn_term	= termcn_cnterm,
511 	.cn_getc	= termcn_cngetc,
512 	.cn_putc	= termcn_cnputc,
513 	.cn_grab	= termcn_cngrab,
514 	.cn_ungrab	= termcn_cnungrab,
515 };
516 
517 void
518 termcn_cnregister(struct terminal *tm)
519 {
520 	struct consdev *cp;
521 
522 	cp = tm->consdev;
523 	if (cp == NULL) {
524 		cp = malloc(sizeof(struct consdev), M_TERMINAL,
525 		    M_WAITOK|M_ZERO);
526 		cp->cn_ops = &termcn_cnops;
527 		cp->cn_arg = tm;
528 		cp->cn_pri = CN_INTERNAL;
529 		sprintf(cp->cn_name, "ttyv0");
530 
531 		tm->tm_flags = TF_CONS;
532 		tm->consdev = cp;
533 
534 		terminal_init(tm);
535 	}
536 
537 	/* Attach terminal as console. */
538 	cnadd(cp);
539 }
540 
541 static void
542 termcn_cngrab(struct consdev *cp)
543 {
544 	struct terminal *tm = cp->cn_arg;
545 
546 	tm->tm_class->tc_cngrab(tm);
547 }
548 
549 static void
550 termcn_cnungrab(struct consdev *cp)
551 {
552 	struct terminal *tm = cp->cn_arg;
553 
554 	tm->tm_class->tc_cnungrab(tm);
555 }
556 
557 static void
558 termcn_cnprobe(struct consdev *cp)
559 {
560 	struct terminal *tm = cp->cn_arg;
561 
562 	if (tm == NULL) {
563 		cp->cn_pri = CN_DEAD;
564 		return;
565 	}
566 
567 	tm->consdev = cp;
568 	terminal_init(tm);
569 
570 	tm->tm_class->tc_cnprobe(tm, cp);
571 }
572 
573 static void
574 termcn_cninit(struct consdev *cp)
575 {
576 
577 }
578 
579 static void
580 termcn_cnterm(struct consdev *cp)
581 {
582 
583 }
584 
585 static int
586 termcn_cngetc(struct consdev *cp)
587 {
588 	struct terminal *tm = cp->cn_arg;
589 
590 	return (tm->tm_class->tc_cngetc(tm));
591 }
592 
593 static void
594 termcn_cnputc(struct consdev *cp, int c)
595 {
596 	struct terminal *tm = cp->cn_arg;
597 	teken_attr_t backup;
598 	char cv = c;
599 
600 	TERMINAL_LOCK_CONS(tm);
601 	if (!(tm->tm_flags & TF_MUTE)) {
602 		backup = *teken_get_curattr(&tm->tm_emulator);
603 		teken_set_curattr(&tm->tm_emulator, &kernel_message);
604 		teken_input(&tm->tm_emulator, &cv, 1);
605 		teken_set_curattr(&tm->tm_emulator, &backup);
606 		tm->tm_class->tc_done(tm);
607 	}
608 	TERMINAL_UNLOCK_CONS(tm);
609 }
610 
611 /*
612  * Binding with the terminal emulator.
613  */
614 
615 static void
616 termteken_bell(void *softc)
617 {
618 	struct terminal *tm = softc;
619 
620 	tm->tm_flags |= TF_BELL;
621 }
622 
623 static void
624 termteken_cursor(void *softc, const teken_pos_t *p)
625 {
626 	struct terminal *tm = softc;
627 
628 	tm->tm_class->tc_cursor(tm, p);
629 }
630 
631 static void
632 termteken_putchar(void *softc, const teken_pos_t *p, teken_char_t c,
633     const teken_attr_t *a)
634 {
635 	struct terminal *tm = softc;
636 
637 	tm->tm_class->tc_putchar(tm, p, TCHAR_CREATE(c, a));
638 }
639 
640 static void
641 termteken_fill(void *softc, const teken_rect_t *r, teken_char_t c,
642     const teken_attr_t *a)
643 {
644 	struct terminal *tm = softc;
645 
646 	tm->tm_class->tc_fill(tm, r, TCHAR_CREATE(c, a));
647 }
648 
649 static void
650 termteken_copy(void *softc, const teken_rect_t *r, const teken_pos_t *p)
651 {
652 	struct terminal *tm = softc;
653 
654 	tm->tm_class->tc_copy(tm, r, p);
655 }
656 
657 static void
658 termteken_pre_input(void *softc)
659 {
660 	struct terminal *tm = softc;
661 
662 	tm->tm_class->tc_pre_input(tm);
663 }
664 
665 static void
666 termteken_post_input(void *softc)
667 {
668 	struct terminal *tm = softc;
669 
670 	tm->tm_class->tc_post_input(tm);
671 }
672 
673 static void
674 termteken_param(void *softc, int cmd, unsigned int arg)
675 {
676 	struct terminal *tm = softc;
677 
678 	tm->tm_class->tc_param(tm, cmd, arg);
679 }
680 
681 static void
682 termteken_respond(void *softc, const void *buf, size_t len)
683 {
684 #if 0
685 	struct terminal *tm = softc;
686 	struct tty *tp;
687 
688 	/*
689 	 * Only inject a response into the TTY if the data actually
690 	 * originated from the TTY.
691 	 *
692 	 * XXX: This cannot be done right now.  The TTY could pick up
693 	 * other locks.  It could also in theory cause loops, when the
694 	 * TTY performs echoing of a command that generates even more
695 	 * input.
696 	 */
697 	tp = tm->tm_tty;
698 	if (tp == NULL)
699 		return;
700 
701 	ttydisc_rint_simple(tp, buf, len);
702 	ttydisc_rint_done(tp);
703 #endif
704 }
705