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