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/sysctl.h> 38 #include <sys/systm.h> 39 #include <sys/tty.h> 40 #include <sys/uio.h> 41 42 #include <vm/uma.h> 43 44 /* 45 * TTY output queue buffering. 46 * 47 * The previous design of the TTY layer offered the so-called clists. 48 * These clists were used for both the input queues and the output 49 * queue. We don't use certain features on the output side, like quoting 50 * bits for parity marking and such. This mechanism is similar to the 51 * old clists, but only contains the features we need to buffer the 52 * output. 53 */ 54 55 /* Statistics. */ 56 static long ttyoutq_nfast = 0; 57 SYSCTL_LONG(_kern, OID_AUTO, tty_outq_nfast, CTLFLAG_RD, 58 &ttyoutq_nfast, 0, "Unbuffered reads to userspace on output"); 59 static long ttyoutq_nslow = 0; 60 SYSCTL_LONG(_kern, OID_AUTO, tty_outq_nslow, CTLFLAG_RD, 61 &ttyoutq_nslow, 0, "Buffered reads to userspace on output"); 62 63 struct ttyoutq_block { 64 STAILQ_ENTRY(ttyoutq_block) tob_list; 65 char tob_data[TTYOUTQ_DATASIZE]; 66 }; 67 68 static uma_zone_t ttyoutq_zone; 69 70 void 71 ttyoutq_flush(struct ttyoutq *to) 72 { 73 74 to->to_begin = 0; 75 to->to_end = 0; 76 } 77 78 void 79 ttyoutq_setsize(struct ttyoutq *to, struct tty *tp, size_t size) 80 { 81 unsigned int nblocks; 82 struct ttyoutq_block *tob; 83 84 nblocks = howmany(size, TTYOUTQ_DATASIZE); 85 86 while (nblocks > to->to_nblocks) { 87 /* 88 * List is getting bigger. 89 * Add new blocks to the tail of the list. 90 * 91 * We must unlock the TTY temporarily, because we need 92 * to allocate memory. This won't be a problem, because 93 * in the worst case, another thread ends up here, which 94 * may cause us to allocate too many blocks, but this 95 * will be caught by the loop below. 96 */ 97 tty_unlock(tp); 98 tob = uma_zalloc(ttyoutq_zone, M_WAITOK); 99 tty_lock(tp); 100 101 if (tty_gone(tp)) 102 return; 103 104 STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 105 to->to_nblocks++; 106 } 107 108 while (nblocks < to->to_nblocks) { 109 /* 110 * List is getting smaller. Remove unused blocks at the 111 * end. This means we cannot guarantee this routine 112 * shrinks buffers properly, when we need to reclaim 113 * more space than there is available. 114 * 115 * XXX TODO: Two solutions here: 116 * - Throw data away 117 * - Temporarily hit the watermark until enough data has 118 * been flushed, so we can remove the blocks. 119 */ 120 121 if (to->to_end == 0) { 122 tob = STAILQ_FIRST(&to->to_list); 123 if (tob == NULL) 124 break; 125 STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 126 } else { 127 tob = STAILQ_NEXT(to->to_lastblock, tob_list); 128 if (tob == NULL) 129 break; 130 STAILQ_REMOVE_NEXT(&to->to_list, to->to_lastblock, tob_list); 131 } 132 uma_zfree(ttyoutq_zone, tob); 133 to->to_nblocks--; 134 } 135 } 136 137 size_t 138 ttyoutq_read(struct ttyoutq *to, void *buf, size_t len) 139 { 140 char *cbuf = buf; 141 142 while (len > 0) { 143 struct ttyoutq_block *tob; 144 size_t cbegin, cend, clen; 145 146 /* See if there still is data. */ 147 if (to->to_begin == to->to_end) 148 break; 149 tob = STAILQ_FIRST(&to->to_list); 150 if (tob == NULL) 151 break; 152 153 /* 154 * The end address should be the lowest of these three: 155 * - The write pointer 156 * - The blocksize - we can't read beyond the block 157 * - The end address if we could perform the full read 158 */ 159 cbegin = to->to_begin; 160 cend = MIN(MIN(to->to_end, to->to_begin + len), 161 TTYOUTQ_DATASIZE); 162 clen = cend - cbegin; 163 164 if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) { 165 /* Read the block until the end. */ 166 STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 167 STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 168 to->to_begin = 0; 169 if (to->to_end <= TTYOUTQ_DATASIZE) { 170 to->to_end = 0; 171 } else { 172 to->to_end -= TTYOUTQ_DATASIZE; 173 } 174 } else { 175 /* Read the block partially. */ 176 to->to_begin += clen; 177 } 178 179 /* Copy the data out of the buffers. */ 180 memcpy(cbuf, tob->tob_data + cbegin, clen); 181 cbuf += clen; 182 len -= clen; 183 } 184 185 return (cbuf - (char *)buf); 186 } 187 188 /* 189 * An optimized version of ttyoutq_read() which can be used in pseudo 190 * TTY drivers to directly copy data from the outq to userspace, instead 191 * of buffering it. 192 * 193 * We can only copy data directly if we need to read the entire block 194 * back to the user, because we temporarily remove the block from the 195 * queue. Otherwise we need to copy it to a temporary buffer first, to 196 * make sure data remains in the correct order. 197 */ 198 int 199 ttyoutq_read_uio(struct ttyoutq *to, struct tty *tp, struct uio *uio) 200 { 201 202 while (uio->uio_resid > 0) { 203 int error; 204 struct ttyoutq_block *tob; 205 size_t cbegin, cend, clen; 206 207 /* See if there still is data. */ 208 if (to->to_begin == to->to_end) 209 return (0); 210 tob = STAILQ_FIRST(&to->to_list); 211 if (tob == NULL) 212 return (0); 213 214 /* 215 * The end address should be the lowest of these three: 216 * - The write pointer 217 * - The blocksize - we can't read beyond the block 218 * - The end address if we could perform the full read 219 */ 220 cbegin = to->to_begin; 221 cend = MIN(MIN(to->to_end, to->to_begin + uio->uio_resid), 222 TTYOUTQ_DATASIZE); 223 clen = cend - cbegin; 224 225 /* 226 * We can prevent buffering in some cases: 227 * - We need to read the block until the end. 228 * - We don't need to read the block until the end, but 229 * there is no data beyond it, which allows us to move 230 * the write pointer to a new block. 231 */ 232 if (cend == TTYOUTQ_DATASIZE || cend == to->to_end) { 233 atomic_add_long(&ttyoutq_nfast, 1); 234 235 /* 236 * Fast path: zero copy. Remove the first block, 237 * so we can unlock the TTY temporarily. 238 */ 239 STAILQ_REMOVE_HEAD(&to->to_list, tob_list); 240 to->to_nblocks--; 241 to->to_begin = 0; 242 if (to->to_end <= TTYOUTQ_DATASIZE) { 243 to->to_end = 0; 244 } else { 245 to->to_end -= TTYOUTQ_DATASIZE; 246 } 247 248 /* Temporary unlock and copy the data to userspace. */ 249 tty_unlock(tp); 250 error = uiomove(tob->tob_data + cbegin, clen, uio); 251 tty_lock(tp); 252 253 /* Block can now be readded to the list. */ 254 /* 255 * XXX: we could remove the blocks here when the 256 * queue was shrunk, but still in use. See 257 * ttyoutq_setsize(). 258 */ 259 STAILQ_INSERT_TAIL(&to->to_list, tob, tob_list); 260 to->to_nblocks++; 261 if (error != 0) 262 return (error); 263 } else { 264 char ob[TTYOUTQ_DATASIZE - 1]; 265 atomic_add_long(&ttyoutq_nslow, 1); 266 267 /* 268 * Slow path: store data in a temporary buffer. 269 */ 270 memcpy(ob, tob->tob_data + cbegin, clen); 271 to->to_begin += clen; 272 MPASS(to->to_begin < TTYOUTQ_DATASIZE); 273 274 /* Temporary unlock and copy the data to userspace. */ 275 tty_unlock(tp); 276 error = uiomove(ob, clen, uio); 277 tty_lock(tp); 278 279 if (error != 0) 280 return (error); 281 } 282 } 283 284 return (0); 285 } 286 287 size_t 288 ttyoutq_write(struct ttyoutq *to, const void *buf, size_t nbytes) 289 { 290 const char *cbuf = buf; 291 struct ttyoutq_block *tob; 292 unsigned int boff; 293 size_t l; 294 295 while (nbytes > 0) { 296 /* Offset in current block. */ 297 tob = to->to_lastblock; 298 boff = to->to_end % TTYOUTQ_DATASIZE; 299 300 if (to->to_end == 0) { 301 /* First time we're being used or drained. */ 302 MPASS(to->to_begin == 0); 303 tob = to->to_lastblock = STAILQ_FIRST(&to->to_list); 304 if (tob == NULL) { 305 /* Queue has no blocks. */ 306 break; 307 } 308 } else if (boff == 0) { 309 /* We reached the end of this block on last write. */ 310 tob = STAILQ_NEXT(tob, tob_list); 311 if (tob == NULL) { 312 /* We've reached the watermark. */ 313 break; 314 } 315 to->to_lastblock = tob; 316 } 317 318 /* Don't copy more than was requested. */ 319 l = MIN(nbytes, TTYOUTQ_DATASIZE - boff); 320 MPASS(l > 0); 321 memcpy(tob->tob_data + boff, cbuf, l); 322 323 cbuf += l; 324 nbytes -= l; 325 to->to_end += l; 326 } 327 328 return (cbuf - (const char *)buf); 329 } 330 331 int 332 ttyoutq_write_nofrag(struct ttyoutq *to, const void *buf, size_t nbytes) 333 { 334 size_t ret; 335 336 if (ttyoutq_bytesleft(to) < nbytes) 337 return (-1); 338 339 /* We should always be able to write it back. */ 340 ret = ttyoutq_write(to, buf, nbytes); 341 MPASS(ret == nbytes); 342 343 return (0); 344 } 345 346 static void 347 ttyoutq_startup(void *dummy) 348 { 349 350 ttyoutq_zone = uma_zcreate("ttyoutq", sizeof(struct ttyoutq_block), 351 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0); 352 } 353 354 SYSINIT(ttyoutq, SI_SUB_DRIVERS, SI_ORDER_FIRST, ttyoutq_startup, NULL); 355