xref: /freebsd/usr.sbin/bhyve/uart_emul.c (revision 43d1e6ee299ad4e143d90d3ad374d1c24bd3306f) 
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
3  *
4  * Copyright (c) 2012 NetApp, Inc.
5  * Copyright (c) 2013 Neel Natu <neel@freebsd.org>
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY NETAPP, INC ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL NETAPP, INC OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * $FreeBSD$
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include <sys/types.h>
36 #include <dev/ic/ns16550.h>
37 #ifndef WITHOUT_CAPSICUM
38 #include <sys/capsicum.h>
39 #include <capsicum_helpers.h>
40 #endif
41 
42 #include <stdio.h>
43 #include <stdlib.h>
44 #include <assert.h>
45 #include <err.h>
46 #include <errno.h>
47 #include <fcntl.h>
48 #include <termios.h>
49 #include <unistd.h>
50 #include <stdbool.h>
51 #include <string.h>
52 #include <pthread.h>
53 #include <sysexits.h>
54 
55 #include "mevent.h"
56 #include "uart_emul.h"
57 
58 #define	COM1_BASE      	0x3F8
59 #define	COM1_IRQ	4
60 #define	COM2_BASE      	0x2F8
61 #define	COM2_IRQ	3
62 
63 #define	DEFAULT_RCLK	1843200
64 #define	DEFAULT_BAUD	9600
65 
66 #define	FCR_RX_MASK	0xC0
67 
68 #define	MCR_OUT1	0x04
69 #define	MCR_OUT2	0x08
70 
71 #define	MSR_DELTA_MASK	0x0f
72 
73 #ifndef REG_SCR
74 #define	REG_SCR		com_scr
75 #endif
76 
77 #define	FIFOSZ	16
78 
79 static bool uart_stdio;		/* stdio in use for i/o */
80 static struct termios tio_stdio_orig;
81 
82 static struct {
83 	int	baseaddr;
84 	int	irq;
85 	bool	inuse;
86 } uart_lres[] = {
87 	{ COM1_BASE, COM1_IRQ, false},
88 	{ COM2_BASE, COM2_IRQ, false},
89 };
90 
91 #define	UART_NLDEVS	(sizeof(uart_lres) / sizeof(uart_lres[0]))
92 
93 struct fifo {
94 	uint8_t	buf[FIFOSZ];
95 	int	rindex;		/* index to read from */
96 	int	windex;		/* index to write to */
97 	int	num;		/* number of characters in the fifo */
98 	int	size;		/* size of the fifo */
99 };
100 
101 struct ttyfd {
102 	bool	opened;
103 	int	fd;		/* tty device file descriptor */
104 	struct termios tio_orig, tio_new;    /* I/O Terminals */
105 };
106 
107 struct uart_softc {
108 	pthread_mutex_t mtx;	/* protects all softc elements */
109 	uint8_t	data;		/* Data register (R/W) */
110 	uint8_t ier;		/* Interrupt enable register (R/W) */
111 	uint8_t lcr;		/* Line control register (R/W) */
112 	uint8_t mcr;		/* Modem control register (R/W) */
113 	uint8_t lsr;		/* Line status register (R/W) */
114 	uint8_t msr;		/* Modem status register (R/W) */
115 	uint8_t fcr;		/* FIFO control register (W) */
116 	uint8_t scr;		/* Scratch register (R/W) */
117 
118 	uint8_t dll;		/* Baudrate divisor latch LSB */
119 	uint8_t dlh;		/* Baudrate divisor latch MSB */
120 
121 	struct fifo rxfifo;
122 	struct mevent *mev;
123 
124 	struct ttyfd tty;
125 	bool	thre_int_pending;	/* THRE interrupt pending */
126 
127 	void	*arg;
128 	uart_intr_func_t intr_assert;
129 	uart_intr_func_t intr_deassert;
130 };
131 
132 static void uart_drain(int fd, enum ev_type ev, void *arg);
133 
134 static void
135 ttyclose(void)
136 {
137 
138 	tcsetattr(STDIN_FILENO, TCSANOW, &tio_stdio_orig);
139 }
140 
141 static void
142 ttyopen(struct ttyfd *tf)
143 {
144 
145 	tcgetattr(tf->fd, &tf->tio_orig);
146 
147 	tf->tio_new = tf->tio_orig;
148 	cfmakeraw(&tf->tio_new);
149 	tf->tio_new.c_cflag |= CLOCAL;
150 	tcsetattr(tf->fd, TCSANOW, &tf->tio_new);
151 
152 	if (tf->fd == STDIN_FILENO) {
153 		tio_stdio_orig = tf->tio_orig;
154 		atexit(ttyclose);
155 	}
156 }
157 
158 static int
159 ttyread(struct ttyfd *tf)
160 {
161 	unsigned char rb;
162 
163 	if (read(tf->fd, &rb, 1) == 1)
164 		return (rb);
165 	else
166 		return (-1);
167 }
168 
169 static void
170 ttywrite(struct ttyfd *tf, unsigned char wb)
171 {
172 
173 	(void)write(tf->fd, &wb, 1);
174 }
175 
176 static void
177 rxfifo_reset(struct uart_softc *sc, int size)
178 {
179 	char flushbuf[32];
180 	struct fifo *fifo;
181 	ssize_t nread;
182 	int error;
183 
184 	fifo = &sc->rxfifo;
185 	bzero(fifo, sizeof(struct fifo));
186 	fifo->size = size;
187 
188 	if (sc->tty.opened) {
189 		/*
190 		 * Flush any unread input from the tty buffer.
191 		 */
192 		while (1) {
193 			nread = read(sc->tty.fd, flushbuf, sizeof(flushbuf));
194 			if (nread != sizeof(flushbuf))
195 				break;
196 		}
197 
198 		/*
199 		 * Enable mevent to trigger when new characters are available
200 		 * on the tty fd.
201 		 */
202 		error = mevent_enable(sc->mev);
203 		assert(error == 0);
204 	}
205 }
206 
207 static int
208 rxfifo_available(struct uart_softc *sc)
209 {
210 	struct fifo *fifo;
211 
212 	fifo = &sc->rxfifo;
213 	return (fifo->num < fifo->size);
214 }
215 
216 static int
217 rxfifo_putchar(struct uart_softc *sc, uint8_t ch)
218 {
219 	struct fifo *fifo;
220 	int error;
221 
222 	fifo = &sc->rxfifo;
223 
224 	if (fifo->num < fifo->size) {
225 		fifo->buf[fifo->windex] = ch;
226 		fifo->windex = (fifo->windex + 1) % fifo->size;
227 		fifo->num++;
228 		if (!rxfifo_available(sc)) {
229 			if (sc->tty.opened) {
230 				/*
231 				 * Disable mevent callback if the FIFO is full.
232 				 */
233 				error = mevent_disable(sc->mev);
234 				assert(error == 0);
235 			}
236 		}
237 		return (0);
238 	} else
239 		return (-1);
240 }
241 
242 static int
243 rxfifo_getchar(struct uart_softc *sc)
244 {
245 	struct fifo *fifo;
246 	int c, error, wasfull;
247 
248 	wasfull = 0;
249 	fifo = &sc->rxfifo;
250 	if (fifo->num > 0) {
251 		if (!rxfifo_available(sc))
252 			wasfull = 1;
253 		c = fifo->buf[fifo->rindex];
254 		fifo->rindex = (fifo->rindex + 1) % fifo->size;
255 		fifo->num--;
256 		if (wasfull) {
257 			if (sc->tty.opened) {
258 				error = mevent_enable(sc->mev);
259 				assert(error == 0);
260 			}
261 		}
262 		return (c);
263 	} else
264 		return (-1);
265 }
266 
267 static int
268 rxfifo_numchars(struct uart_softc *sc)
269 {
270 	struct fifo *fifo = &sc->rxfifo;
271 
272 	return (fifo->num);
273 }
274 
275 static void
276 uart_opentty(struct uart_softc *sc)
277 {
278 
279 	ttyopen(&sc->tty);
280 	sc->mev = mevent_add(sc->tty.fd, EVF_READ, uart_drain, sc);
281 	assert(sc->mev != NULL);
282 }
283 
284 static uint8_t
285 modem_status(uint8_t mcr)
286 {
287 	uint8_t msr;
288 
289 	if (mcr & MCR_LOOPBACK) {
290 		/*
291 		 * In the loopback mode certain bits from the MCR are
292 		 * reflected back into MSR.
293 		 */
294 		msr = 0;
295 		if (mcr & MCR_RTS)
296 			msr |= MSR_CTS;
297 		if (mcr & MCR_DTR)
298 			msr |= MSR_DSR;
299 		if (mcr & MCR_OUT1)
300 			msr |= MSR_RI;
301 		if (mcr & MCR_OUT2)
302 			msr |= MSR_DCD;
303 	} else {
304 		/*
305 		 * Always assert DCD and DSR so tty open doesn't block
306 		 * even if CLOCAL is turned off.
307 		 */
308 		msr = MSR_DCD | MSR_DSR;
309 	}
310 	assert((msr & MSR_DELTA_MASK) == 0);
311 
312 	return (msr);
313 }
314 
315 /*
316  * The IIR returns a prioritized interrupt reason:
317  * - receive data available
318  * - transmit holding register empty
319  * - modem status change
320  *
321  * Return an interrupt reason if one is available.
322  */
323 static int
324 uart_intr_reason(struct uart_softc *sc)
325 {
326 
327 	if ((sc->lsr & LSR_OE) != 0 && (sc->ier & IER_ERLS) != 0)
328 		return (IIR_RLS);
329 	else if (rxfifo_numchars(sc) > 0 && (sc->ier & IER_ERXRDY) != 0)
330 		return (IIR_RXTOUT);
331 	else if (sc->thre_int_pending && (sc->ier & IER_ETXRDY) != 0)
332 		return (IIR_TXRDY);
333 	else if ((sc->msr & MSR_DELTA_MASK) != 0 && (sc->ier & IER_EMSC) != 0)
334 		return (IIR_MLSC);
335 	else
336 		return (IIR_NOPEND);
337 }
338 
339 static void
340 uart_reset(struct uart_softc *sc)
341 {
342 	uint16_t divisor;
343 
344 	divisor = DEFAULT_RCLK / DEFAULT_BAUD / 16;
345 	sc->dll = divisor;
346 	sc->dlh = divisor >> 16;
347 	sc->msr = modem_status(sc->mcr);
348 
349 	rxfifo_reset(sc, 1);	/* no fifo until enabled by software */
350 }
351 
352 /*
353  * Toggle the COM port's intr pin depending on whether or not we have an
354  * interrupt condition to report to the processor.
355  */
356 static void
357 uart_toggle_intr(struct uart_softc *sc)
358 {
359 	uint8_t intr_reason;
360 
361 	intr_reason = uart_intr_reason(sc);
362 
363 	if (intr_reason == IIR_NOPEND)
364 		(*sc->intr_deassert)(sc->arg);
365 	else
366 		(*sc->intr_assert)(sc->arg);
367 }
368 
369 static void
370 uart_drain(int fd, enum ev_type ev, void *arg)
371 {
372 	struct uart_softc *sc;
373 	int ch;
374 
375 	sc = arg;
376 
377 	assert(fd == sc->tty.fd);
378 	assert(ev == EVF_READ);
379 
380 	/*
381 	 * This routine is called in the context of the mevent thread
382 	 * to take out the softc lock to protect against concurrent
383 	 * access from a vCPU i/o exit
384 	 */
385 	pthread_mutex_lock(&sc->mtx);
386 
387 	if ((sc->mcr & MCR_LOOPBACK) != 0) {
388 		(void) ttyread(&sc->tty);
389 	} else {
390 		while (rxfifo_available(sc) &&
391 		       ((ch = ttyread(&sc->tty)) != -1)) {
392 			rxfifo_putchar(sc, ch);
393 		}
394 		uart_toggle_intr(sc);
395 	}
396 
397 	pthread_mutex_unlock(&sc->mtx);
398 }
399 
400 void
401 uart_write(struct uart_softc *sc, int offset, uint8_t value)
402 {
403 	int fifosz;
404 	uint8_t msr;
405 
406 	pthread_mutex_lock(&sc->mtx);
407 
408 	/*
409 	 * Take care of the special case DLAB accesses first
410 	 */
411 	if ((sc->lcr & LCR_DLAB) != 0) {
412 		if (offset == REG_DLL) {
413 			sc->dll = value;
414 			goto done;
415 		}
416 
417 		if (offset == REG_DLH) {
418 			sc->dlh = value;
419 			goto done;
420 		}
421 	}
422 
423         switch (offset) {
424 	case REG_DATA:
425 		if (sc->mcr & MCR_LOOPBACK) {
426 			if (rxfifo_putchar(sc, value) != 0)
427 				sc->lsr |= LSR_OE;
428 		} else if (sc->tty.opened) {
429 			ttywrite(&sc->tty, value);
430 		} /* else drop on floor */
431 		sc->thre_int_pending = true;
432 		break;
433 	case REG_IER:
434 		/* Set pending when IER_ETXRDY is raised (edge-triggered). */
435 		if ((sc->ier & IER_ETXRDY) == 0 && (value & IER_ETXRDY) != 0)
436 			sc->thre_int_pending = true;
437 		/*
438 		 * Apply mask so that bits 4-7 are 0
439 		 * Also enables bits 0-3 only if they're 1
440 		 */
441 		sc->ier = value & 0x0F;
442 		break;
443 	case REG_FCR:
444 		/*
445 		 * When moving from FIFO and 16450 mode and vice versa,
446 		 * the FIFO contents are reset.
447 		 */
448 		if ((sc->fcr & FCR_ENABLE) ^ (value & FCR_ENABLE)) {
449 			fifosz = (value & FCR_ENABLE) ? FIFOSZ : 1;
450 			rxfifo_reset(sc, fifosz);
451 		}
452 
453 		/*
454 		 * The FCR_ENABLE bit must be '1' for the programming
455 		 * of other FCR bits to be effective.
456 		 */
457 		if ((value & FCR_ENABLE) == 0) {
458 			sc->fcr = 0;
459 		} else {
460 			if ((value & FCR_RCV_RST) != 0)
461 				rxfifo_reset(sc, FIFOSZ);
462 
463 			sc->fcr = value &
464 				 (FCR_ENABLE | FCR_DMA | FCR_RX_MASK);
465 		}
466 		break;
467 	case REG_LCR:
468 		sc->lcr = value;
469 		break;
470 	case REG_MCR:
471 		/* Apply mask so that bits 5-7 are 0 */
472 		sc->mcr = value & 0x1F;
473 		msr = modem_status(sc->mcr);
474 
475 		/*
476 		 * Detect if there has been any change between the
477 		 * previous and the new value of MSR. If there is
478 		 * then assert the appropriate MSR delta bit.
479 		 */
480 		if ((msr & MSR_CTS) ^ (sc->msr & MSR_CTS))
481 			sc->msr |= MSR_DCTS;
482 		if ((msr & MSR_DSR) ^ (sc->msr & MSR_DSR))
483 			sc->msr |= MSR_DDSR;
484 		if ((msr & MSR_DCD) ^ (sc->msr & MSR_DCD))
485 			sc->msr |= MSR_DDCD;
486 		if ((sc->msr & MSR_RI) != 0 && (msr & MSR_RI) == 0)
487 			sc->msr |= MSR_TERI;
488 
489 		/*
490 		 * Update the value of MSR while retaining the delta
491 		 * bits.
492 		 */
493 		sc->msr &= MSR_DELTA_MASK;
494 		sc->msr |= msr;
495 		break;
496 	case REG_LSR:
497 		/*
498 		 * Line status register is not meant to be written to
499 		 * during normal operation.
500 		 */
501 		break;
502 	case REG_MSR:
503 		/*
504 		 * As far as I can tell MSR is a read-only register.
505 		 */
506 		break;
507 	case REG_SCR:
508 		sc->scr = value;
509 		break;
510 	default:
511 		break;
512 	}
513 
514 done:
515 	uart_toggle_intr(sc);
516 	pthread_mutex_unlock(&sc->mtx);
517 }
518 
519 uint8_t
520 uart_read(struct uart_softc *sc, int offset)
521 {
522 	uint8_t iir, intr_reason, reg;
523 
524 	pthread_mutex_lock(&sc->mtx);
525 
526 	/*
527 	 * Take care of the special case DLAB accesses first
528 	 */
529 	if ((sc->lcr & LCR_DLAB) != 0) {
530 		if (offset == REG_DLL) {
531 			reg = sc->dll;
532 			goto done;
533 		}
534 
535 		if (offset == REG_DLH) {
536 			reg = sc->dlh;
537 			goto done;
538 		}
539 	}
540 
541 	switch (offset) {
542 	case REG_DATA:
543 		reg = rxfifo_getchar(sc);
544 		break;
545 	case REG_IER:
546 		reg = sc->ier;
547 		break;
548 	case REG_IIR:
549 		iir = (sc->fcr & FCR_ENABLE) ? IIR_FIFO_MASK : 0;
550 
551 		intr_reason = uart_intr_reason(sc);
552 
553 		/*
554 		 * Deal with side effects of reading the IIR register
555 		 */
556 		if (intr_reason == IIR_TXRDY)
557 			sc->thre_int_pending = false;
558 
559 		iir |= intr_reason;
560 
561 		reg = iir;
562 		break;
563 	case REG_LCR:
564 		reg = sc->lcr;
565 		break;
566 	case REG_MCR:
567 		reg = sc->mcr;
568 		break;
569 	case REG_LSR:
570 		/* Transmitter is always ready for more data */
571 		sc->lsr |= LSR_TEMT | LSR_THRE;
572 
573 		/* Check for new receive data */
574 		if (rxfifo_numchars(sc) > 0)
575 			sc->lsr |= LSR_RXRDY;
576 		else
577 			sc->lsr &= ~LSR_RXRDY;
578 
579 		reg = sc->lsr;
580 
581 		/* The LSR_OE bit is cleared on LSR read */
582 		sc->lsr &= ~LSR_OE;
583 		break;
584 	case REG_MSR:
585 		/*
586 		 * MSR delta bits are cleared on read
587 		 */
588 		reg = sc->msr;
589 		sc->msr &= ~MSR_DELTA_MASK;
590 		break;
591 	case REG_SCR:
592 		reg = sc->scr;
593 		break;
594 	default:
595 		reg = 0xFF;
596 		break;
597 	}
598 
599 done:
600 	uart_toggle_intr(sc);
601 	pthread_mutex_unlock(&sc->mtx);
602 
603 	return (reg);
604 }
605 
606 int
607 uart_legacy_alloc(int which, int *baseaddr, int *irq)
608 {
609 
610 	if (which < 0 || which >= UART_NLDEVS || uart_lres[which].inuse)
611 		return (-1);
612 
613 	uart_lres[which].inuse = true;
614 	*baseaddr = uart_lres[which].baseaddr;
615 	*irq = uart_lres[which].irq;
616 
617 	return (0);
618 }
619 
620 struct uart_softc *
621 uart_init(uart_intr_func_t intr_assert, uart_intr_func_t intr_deassert,
622     void *arg)
623 {
624 	struct uart_softc *sc;
625 
626 	sc = calloc(1, sizeof(struct uart_softc));
627 
628 	sc->arg = arg;
629 	sc->intr_assert = intr_assert;
630 	sc->intr_deassert = intr_deassert;
631 
632 	pthread_mutex_init(&sc->mtx, NULL);
633 
634 	uart_reset(sc);
635 
636 	return (sc);
637 }
638 
639 static int
640 uart_tty_backend(struct uart_softc *sc, const char *opts)
641 {
642 	int fd;
643 	int retval;
644 
645 	retval = -1;
646 
647 	fd = open(opts, O_RDWR | O_NONBLOCK);
648 	if (fd > 0 && isatty(fd)) {
649 		sc->tty.fd = fd;
650 		sc->tty.opened = true;
651 		retval = 0;
652 	}
653 
654 	return (retval);
655 }
656 
657 int
658 uart_set_backend(struct uart_softc *sc, const char *opts)
659 {
660 	int retval;
661 #ifndef WITHOUT_CAPSICUM
662 	cap_rights_t rights;
663 	cap_ioctl_t cmds[] = { TIOCGETA, TIOCSETA, TIOCGWINSZ };
664 #endif
665 
666 	retval = -1;
667 
668 	if (opts == NULL)
669 		return (0);
670 
671 	if (strcmp("stdio", opts) == 0) {
672 		if (!uart_stdio) {
673 			sc->tty.fd = STDIN_FILENO;
674 			sc->tty.opened = true;
675 			uart_stdio = true;
676 			retval = 0;
677 		}
678 	} else if (uart_tty_backend(sc, opts) == 0) {
679 		retval = 0;
680 	}
681 
682 	/* Make the backend file descriptor non-blocking */
683 	if (retval == 0)
684 		retval = fcntl(sc->tty.fd, F_SETFL, O_NONBLOCK);
685 
686 	if (retval == 0) {
687 #ifndef WITHOUT_CAPSICUM
688 		cap_rights_init(&rights, CAP_EVENT, CAP_IOCTL, CAP_READ,
689 		    CAP_WRITE);
690 		if (caph_rights_limit(sc->tty.fd, &rights) == -1)
691 			errx(EX_OSERR, "Unable to apply rights for sandbox");
692 		if (caph_ioctls_limit(sc->tty.fd, cmds, nitems(cmds)) == -1)
693 			errx(EX_OSERR, "Unable to apply rights for sandbox");
694 		if (!uart_stdio) {
695 			if (caph_limit_stdin() == -1)
696 				errx(EX_OSERR,
697 				    "Unable to apply rights for sandbox");
698 		}
699 #endif
700 		uart_opentty(sc);
701 	}
702 
703 	return (retval);
704 }
705