1 /*-
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2008 Ed Schouten <ed@FreeBSD.org>
5 * All rights reserved.
6 *
7 * Portions of this software were developed under sponsorship from Snow
8 * B.V., the Netherlands.
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/param.h>
33 #include <sys/kernel.h>
34 #include <sys/lock.h>
35 #include <sys/queue.h>
36 #include <sys/systm.h>
37 #include <sys/tty.h>
38 #include <sys/uio.h>
39
40 #include <vm/uma.h>
41
42 /*
43 * TTY output queue buffering.
44 *
45 * The previous design of the TTY layer offered the so-called clists.
46 * These clists were used for both the input queues and the output
47 * queue. We don't use certain features on the output side, like quoting
48 * bits for parity marking and such. This mechanism is similar to the
49 * old clists, but only contains the features we need to buffer the
50 * output.
51 */
52
53 struct ttyoutq_block {
54 struct ttyoutq_block *tob_next;
55 char tob_data[TTYOUTQ_DATASIZE];
56 };
57
58 static uma_zone_t ttyoutq_zone;
59
60 #define TTYOUTQ_INSERT_TAIL(to, tob) do { \
61 if (to->to_end == 0) { \
62 tob->tob_next = to->to_firstblock; \
63 to->to_firstblock = tob; \
64 } else { \
65 tob->tob_next = to->to_lastblock->tob_next; \
66 to->to_lastblock->tob_next = tob; \
67 } \
68 to->to_nblocks++; \
69 } while (0)
70
71 #define TTYOUTQ_REMOVE_HEAD(to) do { \
72 to->to_firstblock = to->to_firstblock->tob_next; \
73 to->to_nblocks--; \
74 } while (0)
75
76 #define TTYOUTQ_RECYCLE(to, tob) do { \
77 if (to->to_quota <= to->to_nblocks) \
78 uma_zfree(ttyoutq_zone, tob); \
79 else \
80 TTYOUTQ_INSERT_TAIL(to, tob); \
81 } while (0)
82
83 void
ttyoutq_flush(struct ttyoutq * to)84 ttyoutq_flush(struct ttyoutq *to)
85 {
86
87 to->to_begin = 0;
88 to->to_end = 0;
89 }
90
91 int
ttyoutq_setsize(struct ttyoutq * to,struct tty * tp,size_t size)92 ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size)
93 {
94 struct ttyoutq_block *tob;
95
96 to->to_quota = howmany(size, TTYOUTQ_DATASIZE);
97
98 while (to->to_quota > to->to_nblocks) {
99 /*
100 * List is getting bigger.
101 * Add new blocks to the tail of the list.
102 *
103 * We must unlock the TTY temporarily, because we need
104 * to allocate memory. This won't be a problem, because
105 * in the worst case, another thread ends up here, which
106 * may cause us to allocate too many blocks, but this
107 * will be caught by the loop below.
108 */
109 tty_unlock(tp);
110 tob = uma_zalloc(ttyoutq_zone, M_WAITOK);
111 tty_lock(tp);
112
113 if (tty_gone(tp)) {
114 uma_zfree(ttyoutq_zone, tob);
115 return (ENXIO);
116 }
117
118 TTYOUTQ_INSERT_TAIL(to, tob);
119 }
120 return (0);
121 }
122
123 void
ttyoutq_free(struct ttyoutq * to)124 ttyoutq_free(struct ttyoutq *to)
125 {
126 struct ttyoutq_block *tob;
127
128 ttyoutq_flush(to);
129 to->to_quota = 0;
130
131 while ((tob = to->to_firstblock) != NULL) {
132 TTYOUTQ_REMOVE_HEAD(to);
133 uma_zfree(ttyoutq_zone, tob);
134 }
135
136 MPASS(to->to_nblocks == 0);
137 }
138
139 size_t
ttyoutq_read(struct ttyoutq * to,void * buf,size_t len)140 ttyoutq_read(struct ttyoutq *to, void *buf, size_t len)
141 {
142 char *cbuf = buf;
143
144 while (len > 0) {
145 struct ttyoutq_block *tob;
146 size_t cbegin, cend, clen;
147
148 /* See if there still is data. */
149 if (to->to_begin == to->to_end)
150 break;
151 tob = to->to_firstblock;
152 if (tob == NULL)
153 break;
154
155 /*
156 * The end address should be the lowest of these three:
157 * - The write pointer
158 * - The blocksize - we can't read beyond the block
159 * - The end address if we could perform the full read
160 */
161 cbegin = to->to_begin;
162 cend = MIN(MIN(to->to_end, to->to_begin + len),
163 TTYOUTQ_DATASIZE);
164 clen = cend - cbegin;
165
166 /* Copy the data out of the buffers. */
167 memcpy(cbuf, tob->tob_data + cbegin, clen);
168 cbuf += clen;
169 len -= clen;
170
171 if (cend == to->to_end) {
172 /* Read the complete queue. */
173 to->to_begin = 0;
174 to->to_end = 0;
175 } else if (cend == TTYOUTQ_DATASIZE) {
176 /* Read the block until the end. */
177 TTYOUTQ_REMOVE_HEAD(to);
178 to->to_begin = 0;
179 to->to_end -= TTYOUTQ_DATASIZE;
180 TTYOUTQ_RECYCLE(to, tob);
181 } else {
182 /* Read the block partially. */
183 to->to_begin += clen;
184 }
185 }
186
187 return (cbuf - (char *)buf);
188 }
189
190 /*
191 * An optimized version of ttyoutq_read() which can be used in pseudo
192 * TTY drivers to directly copy data from the outq to userspace, instead
193 * of buffering it.
194 *
195 * We can only copy data directly if we need to read the entire block
196 * back to the user, because we temporarily remove the block from the
197 * queue. Otherwise we need to copy it to a temporary buffer first, to
198 * make sure data remains in the correct order.
199 */
200 int
ttyoutq_read_uio(struct ttyoutq * to,struct tty * tp,struct uio * uio)201 ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio)
202 {
203
204 while (uio->uio_resid > 0) {
205 int error;
206 struct ttyoutq_block *tob;
207 size_t cbegin, cend, clen;
208
209 /* See if there still is data. */
210 if (to->to_begin == to->to_end)
211 return (0);
212 tob = to->to_firstblock;
213 if (tob == NULL)
214 return (0);
215
216 /*
217 * The end address should be the lowest of these three:
218 * - The write pointer
219 * - The blocksize - we can't read beyond the block
220 * - The end address if we could perform the full read
221 */
222 cbegin = to->to_begin;
223 cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid),
224 TTYOUTQ_DATASIZE);
225 clen = cend - cbegin;
226
227 /*
228 * We can prevent buffering in some cases:
229 * - We need to read the block until the end.
230 * - We don't need to read the block until the end, but
231 * there is no data beyond it, which allows us to move
232 * the write pointer to a new block.
233 */
234 if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) {
235 /*
236 * Fast path: zero copy. Remove the first block,
237 * so we can unlock the TTY temporarily.
238 */
239 TTYOUTQ_REMOVE_HEAD(to);
240 to->to_begin = 0;
241 if (to->to_end <= TTYOUTQ_DATASIZE)
242 to->to_end = 0;
243 else
244 to->to_end -= TTYOUTQ_DATASIZE;
245
246 /* Temporary unlock and copy the data to userspace. */
247 tty_unlock(tp);
248 error = uiomove(tob->tob_data + cbegin, clen, uio);
249 tty_lock(tp);
250
251 /* Block can now be readded to the list. */
252 TTYOUTQ_RECYCLE(to, tob);
253 } else {
254 char ob[TTYOUTQ_DATASIZE - 1];
255
256 /*
257 * Slow path: store data in a temporary buffer.
258 */
259 memcpy(ob, tob->tob_data + cbegin, clen);
260 to->to_begin += clen;
261 MPASS(to->to_begin < TTYOUTQ_DATASIZE);
262
263 /* Temporary unlock and copy the data to userspace. */
264 tty_unlock(tp);
265 error = uiomove(ob, clen, uio);
266 tty_lock(tp);
267 }
268
269 if (error != 0)
270 return (error);
271 }
272
273 return (0);
274 }
275
276 size_t
ttyoutq_write(struct ttyoutq * to,const void * buf,size_t nbytes)277 ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes)
278 {
279 const char *cbuf = buf;
280 struct ttyoutq_block *tob;
281 unsigned int boff;
282 size_t l;
283
284 while (nbytes > 0) {
285 boff = to->to_end % TTYOUTQ_DATASIZE;
286
287 if (to->to_end == 0) {
288 /* First time we're being used or drained. */
289 MPASS(to->to_begin == 0);
290 tob = to->to_firstblock;
291 if (tob == NULL) {
292 /* Queue has no blocks. */
293 break;
294 }
295 to->to_lastblock = tob;
296 } else if (boff == 0) {
297 /* We reached the end of this block on last write. */
298 tob = to->to_lastblock->tob_next;
299 if (tob == NULL) {
300 /* We've reached the watermark. */
301 break;
302 }
303 to->to_lastblock = tob;
304 } else {
305 tob = to->to_lastblock;
306 }
307
308 /* Don't copy more than was requested. */
309 l = MIN(nbytes, TTYOUTQ_DATASIZE - boff);
310 MPASS(l > 0);
311 memcpy(tob->tob_data + boff, cbuf, l);
312
313 cbuf += l;
314 nbytes -= l;
315 to->to_end += l;
316 }
317
318 return (cbuf - (const char *)buf);
319 }
320
321 int
ttyoutq_write_nofrag(struct ttyoutq * to,const void * buf,size_t nbytes)322 ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes)
323 {
324 size_t ret __unused;
325
326 if (ttyoutq_bytesleft(to) < nbytes)
327 return (-1);
328
329 /* We should always be able to write it back. */
330 ret = ttyoutq_write(to, buf, nbytes);
331 MPASS(ret == nbytes);
332
333 return (0);
334 }
335
336 static void
ttyoutq_startup(void * dummy)337 ttyoutq_startup(void *dummy)
338 {
339
340 ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block),
341 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
342 }
343
344 SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL);
345