1/*-
2 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Portions of this software were developed under sponsorship from Snow
6 * B.V., the Netherlands.
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 THE AUTHOR AND CONTRIBUTORS ``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 THE AUTHOR 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
30#include <sys/cdefs.h>
31__FBSDID("$FreeBSD$");
32
33#include <sys/param.h>
34#include <sys/kernel.h>
35#include <sys/lock.h>
36#include <sys/queue.h>
37#include <sys/systm.h>
38#include <sys/tty.h>
39#include <sys/uio.h>
40
41#include <vm/uma.h>
42
43/*
44 * TTY output queue buffering.
45 *
46 * The previous design of the TTY layer offered the so-called clists.
47 * These clists were used for both the input queues and the output
48 * queue. We don't use certain features on the output side, like quoting
49 * bits for parity marking and such. This mechanism is similar to the
50 * old clists, but only contains the features we need to buffer the
51 * output.
52 */
53
54struct ttyoutq_block {
55	struct ttyoutq_block	*tob_next;
56	char			tob_data[TTYOUTQ_DATASIZE];
57};
58
59static uma_zone_t ttyoutq_zone;
60
61#define	TTYOUTQ_INSERT_TAIL(to, tob) do {				\
62	if (to->to_end == 0) {						\
63		tob->tob_next = to->to_firstblock;			\
64		to->to_firstblock = tob;				\
65	} else {							\
66		tob->tob_next = to->to_lastblock->tob_next;		\
67		to->to_lastblock->tob_next = tob;			\
68	}								\
69	to->to_nblocks++;						\
70} while (0)
71
72#define	TTYOUTQ_REMOVE_HEAD(to) do {					\
73	to->to_firstblock = to->to_firstblock->tob_next;		\
74	to->to_nblocks--;						\
75} while (0)
76
77#define	TTYOUTQ_RECYCLE(to, tob) do {					\
78	if (to->to_quota <= to->to_nblocks)				\
79		uma_zfree(ttyoutq_zone, tob);				\
80	else								\
81		TTYOUTQ_INSERT_TAIL(to, tob);				\
82} while(0)
83
84void
85ttyoutq_flush(struct ttyoutq *to)
86{
87
88	to->to_begin = 0;
89	to->to_end = 0;
90}
91
92void
93ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
94{
95	struct ttyoutq_block *tob;
96
97	to->to_quota = howmany(size, TTYOUTQ_DATASIZE);
98
99	while (to->to_quota > to->to_nblocks) {
100		/*
101		 * List is getting bigger.
102		 * Add new blocks to the tail of the list.
103		 *
104		 * We must unlock the TTY temporarily, because we need
105		 * to allocate memory. This won't be a problem, because
106		 * in the worst case, another thread ends up here, which
107		 * may cause us to allocate too many blocks, but this
108		 * will be caught by the loop below.
109		 */
110		tty_unlock(tp);
111		tob = uma_zalloc(ttyoutq_zone, M_WAITOK);
112		tty_lock(tp);
113
114		TTYOUTQ_INSERT_TAIL(to, tob);
115	}
116}
117
118void
119ttyoutq_free(struct ttyoutq *to)
120{
121	struct ttyoutq_block *tob;
122
123	ttyoutq_flush(to);
124	to->to_quota = 0;
125
126	while ((tob = to->to_firstblock) != NULL) {
127		TTYOUTQ_REMOVE_HEAD(to);
128		uma_zfree(ttyoutq_zone, tob);
129	}
130
131	MPASS(to->to_nblocks == 0);
132}
133
134size_t
135ttyoutq_read(struct ttyoutq *to, void *buf, size_t len)
136{
137	char *cbuf = buf;
138
139	while (len > 0) {
140		struct ttyoutq_block *tob;
141		size_t cbegin, cend, clen;
142
143		/* See if there still is data. */
144		if (to->to_begin == to->to_end)
145			break;
146		tob = to->to_firstblock;
147		if (tob == NULL)
148			break;
149
150		/*
151		 * The end address should be the lowest of these three:
152		 * - The write pointer
153		 * - The blocksize - we can't read beyond the block
154		 * - The end address if we could perform the full read
155		 */
156		cbegin = to->to_begin;
157		cend = MIN(MIN(to->to_end, to->to_begin + len),
158		    TTYOUTQ_DATASIZE);
159		clen = cend - cbegin;
160
161		/* Copy the data out of the buffers. */
162		memcpy(cbuf, tob->tob_data + cbegin, clen);
163		cbuf += clen;
164		len -= clen;
165
166		if (cend == to->to_end) {
167			/* Read the complete queue. */
168			to->to_begin = 0;
169			to->to_end = 0;
170		} else if (cend == TTYOUTQ_DATASIZE) {
171			/* Read the block until the end. */
172			TTYOUTQ_REMOVE_HEAD(to);
173			to->to_begin = 0;
174			to->to_end -= TTYOUTQ_DATASIZE;
175			TTYOUTQ_RECYCLE(to, tob);
176		} else {
177			/* Read the block partially. */
178			to->to_begin += clen;
179		}
180	}
181
182	return (cbuf - (char *)buf);
183}
184
185/*
186 * An optimized version of ttyoutq_read() which can be used in pseudo
187 * TTY drivers to directly copy data from the outq to userspace, instead
188 * of buffering it.
189 *
190 * We can only copy data directly if we need to read the entire block
191 * back to the user, because we temporarily remove the block from the
192 * queue. Otherwise we need to copy it to a temporary buffer first, to
193 * make sure data remains in the correct order.
194 */
195int
196ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio)
197{
198
199	while (uio->uio_resid > 0) {
200		int error;
201		struct ttyoutq_block *tob;
202		size_t cbegin, cend, clen;
203
204		/* See if there still is data. */
205		if (to->to_begin == to->to_end)
206			return (0);
207		tob = to->to_firstblock;
208		if (tob == NULL)
209			return (0);
210
211		/*
212		 * The end address should be the lowest of these three:
213		 * - The write pointer
214		 * - The blocksize - we can't read beyond the block
215		 * - The end address if we could perform the full read
216		 */
217		cbegin = to->to_begin;
218		cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid),
219		    TTYOUTQ_DATASIZE);
220		clen = cend - cbegin;
221
222		/*
223		 * We can prevent buffering in some cases:
224		 * - We need to read the block until the end.
225		 * - We don't need to read the block until the end, but
226		 *   there is no data beyond it, which allows us to move
227		 *   the write pointer to a new block.
228		 */
229		if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) {
230			/*
231			 * Fast path: zero copy. Remove the first block,
232			 * so we can unlock the TTY temporarily.
233			 */
234			TTYOUTQ_REMOVE_HEAD(to);
235			to->to_begin = 0;
236			if (to->to_end <= TTYOUTQ_DATASIZE)
237				to->to_end = 0;
238			else
239				to->to_end -= TTYOUTQ_DATASIZE;
240
241			/* Temporary unlock and copy the data to userspace. */
242			tty_unlock(tp);
243			error = uiomove(tob->tob_data + cbegin, clen, uio);
244			tty_lock(tp);
245
246			/* Block can now be readded to the list. */
247			TTYOUTQ_RECYCLE(to, tob);
248		} else {
249			char ob[TTYOUTQ_DATASIZE - 1];
250
251			/*
252			 * Slow path: store data in a temporary buffer.
253			 */
254			memcpy(ob, tob->tob_data + cbegin, clen);
255			to->to_begin += clen;
256			MPASS(to->to_begin < TTYOUTQ_DATASIZE);
257
258			/* Temporary unlock and copy the data to userspace. */
259			tty_unlock(tp);
260			error = uiomove(ob, clen, uio);
261			tty_lock(tp);
262		}
263
264		if (error != 0)
265			return (error);
266	}
267
268	return (0);
269}
270
271size_t
272ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes)
273{
274	const char *cbuf = buf;
275	struct ttyoutq_block *tob;
276	unsigned int boff;
277	size_t l;
278
279	while (nbytes > 0) {
280		boff = to->to_end % TTYOUTQ_DATASIZE;
281
282		if (to->to_end == 0) {
283			/* First time we're being used or drained. */
284			MPASS(to->to_begin == 0);
285			tob = to->to_firstblock;
286			if (tob == NULL) {
287				/* Queue has no blocks. */
288				break;
289			}
290			to->to_lastblock = tob;
291		} else if (boff == 0) {
292			/* We reached the end of this block on last write. */
293			tob = to->to_lastblock->tob_next;
294			if (tob == NULL) {
295				/* We've reached the watermark. */
296				break;
297			}
298			to->to_lastblock = tob;
299		} else {
300			tob = to->to_lastblock;
301		}
302
303		/* Don't copy more than was requested. */
304		l = MIN(nbytes, TTYOUTQ_DATASIZE - boff);
305		MPASS(l > 0);
306		memcpy(tob->tob_data + boff, cbuf, l);
307
308		cbuf += l;
309		nbytes -= l;
310		to->to_end += l;
311	}
312
313	return (cbuf - (const char *)buf);
314}
315
316int
317ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes)
318{
319	size_t ret;
320
321	if (ttyoutq_bytesleft(to) < nbytes)
322		return (-1);
323
324	/* We should always be able to write it back. */
325	ret = ttyoutq_write(to, buf, nbytes);
326	MPASS(ret == nbytes);
327
328	return (0);
329}
330
331static void
332ttyoutq_startup(void *dummy)
333{
334
335	ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block),
336	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
337}
338
339SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL);
340