1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2003 Ian Dowse. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 * 27 * $FreeBSD$ 28 */ 29 30 /* 31 * Generic message buffer support routines. 32 */ 33 34 #include <sys/param.h> 35 #include <sys/systm.h> 36 #include <sys/lock.h> 37 #include <sys/kernel.h> 38 #include <sys/mutex.h> 39 #include <sys/msgbuf.h> 40 #include <sys/sysctl.h> 41 42 /* 43 * Maximum number conversion buffer length: uintmax_t in base 2, plus <> 44 * around the priority, and a terminating NUL. 45 */ 46 #define MAXPRIBUF (sizeof(intmax_t) * NBBY + 3) 47 48 /* Read/write sequence numbers are modulo a multiple of the buffer size. */ 49 #define SEQMOD(size) ((size) * 16) 50 51 static u_int msgbuf_cksum(struct msgbuf *mbp); 52 53 /* 54 * Timestamps in msgbuf are useful when trying to diagnose when core dumps 55 * or other actions occurred. 56 */ 57 static int msgbuf_show_timestamp = 0; 58 SYSCTL_INT(_kern, OID_AUTO, msgbuf_show_timestamp, CTLFLAG_RWTUN, 59 &msgbuf_show_timestamp, 0, "Show timestamp in msgbuf"); 60 61 /* 62 * Initialize a message buffer of the specified size at the specified 63 * location. This also zeros the buffer area. 64 */ 65 void 66 msgbuf_init(struct msgbuf *mbp, void *ptr, int size) 67 { 68 69 mbp->msg_ptr = ptr; 70 mbp->msg_size = size; 71 mbp->msg_seqmod = SEQMOD(size); 72 msgbuf_clear(mbp); 73 mbp->msg_magic = MSG_MAGIC; 74 mbp->msg_lastpri = -1; 75 mbp->msg_flags = 0; 76 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); 77 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); 78 } 79 80 /* 81 * Reinitialize a message buffer, retaining its previous contents if 82 * the size and checksum are correct. If the old contents cannot be 83 * recovered, the message buffer is cleared. 84 */ 85 void 86 msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size) 87 { 88 u_int cksum; 89 90 if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) { 91 msgbuf_init(mbp, ptr, size); 92 return; 93 } 94 mbp->msg_seqmod = SEQMOD(size); 95 mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq); 96 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq); 97 mbp->msg_ptr = ptr; 98 cksum = msgbuf_cksum(mbp); 99 if (cksum != mbp->msg_cksum) { 100 if (bootverbose) { 101 printf("msgbuf cksum mismatch (read %x, calc %x)\n", 102 mbp->msg_cksum, cksum); 103 printf("Old msgbuf not recovered\n"); 104 } 105 msgbuf_clear(mbp); 106 } 107 108 mbp->msg_lastpri = -1; 109 /* Assume that the old message buffer didn't end in a newline. */ 110 mbp->msg_flags |= MSGBUF_NEEDNL; 111 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); 112 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); 113 } 114 115 /* 116 * Clear the message buffer. 117 */ 118 void 119 msgbuf_clear(struct msgbuf *mbp) 120 { 121 122 bzero(mbp->msg_ptr, mbp->msg_size); 123 mbp->msg_wseq = 0; 124 mbp->msg_rseq = 0; 125 mbp->msg_cksum = 0; 126 } 127 128 /* 129 * Get a count of the number of unread characters in the message buffer. 130 */ 131 int 132 msgbuf_getcount(struct msgbuf *mbp) 133 { 134 u_int len; 135 136 len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq); 137 if (len > mbp->msg_size) 138 len = mbp->msg_size; 139 return (len); 140 } 141 142 /* 143 * Add a character into the message buffer, and update the checksum and 144 * sequence number. 145 * 146 * The caller should hold the message buffer spinlock. 147 */ 148 149 static void 150 msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c) 151 { 152 u_int pos; 153 154 /* Make sure we properly wrap the sequence number. */ 155 pos = MSGBUF_SEQ_TO_POS(mbp, *seq); 156 mbp->msg_cksum += (u_int)(u_char)c - 157 (u_int)(u_char)mbp->msg_ptr[pos]; 158 mbp->msg_ptr[pos] = c; 159 *seq = MSGBUF_SEQNORM(mbp, *seq + 1); 160 } 161 162 /* 163 * Append a character to a message buffer. 164 */ 165 void 166 msgbuf_addchar(struct msgbuf *mbp, int c) 167 { 168 mtx_lock_spin(&mbp->msg_lock); 169 170 msgbuf_do_addchar(mbp, &mbp->msg_wseq, c); 171 172 mtx_unlock_spin(&mbp->msg_lock); 173 } 174 175 /* 176 * Append a NUL-terminated string with a priority to a message buffer. 177 * Filter carriage returns if the caller requests it. 178 * 179 * XXX The carriage return filtering behavior is present in the 180 * msglogchar() API, however testing has shown that we don't seem to send 181 * carriage returns down this path. So do we still need it? 182 */ 183 void 184 msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr) 185 { 186 u_int seq; 187 size_t len, prefix_len; 188 char prefix[MAXPRIBUF]; 189 char buf[32]; 190 int i, j, needtime; 191 192 len = strlen(str); 193 prefix_len = 0; 194 195 /* If we have a zero-length string, no need to do anything. */ 196 if (len == 0) 197 return; 198 199 mtx_lock_spin(&mbp->msg_lock); 200 201 /* 202 * If this is true, we may need to insert a new priority sequence, 203 * so prepare the prefix. 204 */ 205 if (pri != -1) 206 prefix_len = sprintf(prefix, "<%d>", pri); 207 208 /* 209 * Starting write sequence number. 210 */ 211 seq = mbp->msg_wseq; 212 213 /* 214 * Whenever there is a change in priority, we have to insert a 215 * newline, and a priority prefix if the priority is not -1. Here 216 * we detect whether there was a priority change, and whether we 217 * did not end with a newline. If that is the case, we need to 218 * insert a newline before this string. 219 */ 220 if (mbp->msg_lastpri != pri && (mbp->msg_flags & MSGBUF_NEEDNL) != 0) { 221 msgbuf_do_addchar(mbp, &seq, '\n'); 222 mbp->msg_flags &= ~MSGBUF_NEEDNL; 223 } 224 225 needtime = 1; 226 for (i = 0; i < len; i++) { 227 /* 228 * If we just had a newline, and the priority is not -1 229 * (and therefore prefix_len != 0), then we need a priority 230 * prefix for this line. 231 */ 232 if ((mbp->msg_flags & MSGBUF_NEEDNL) == 0 && prefix_len != 0) { 233 int j; 234 235 for (j = 0; j < prefix_len; j++) 236 msgbuf_do_addchar(mbp, &seq, prefix[j]); 237 } 238 239 if (msgbuf_show_timestamp && needtime == 1 && 240 (mbp->msg_flags & MSGBUF_NEEDNL) == 0) { 241 snprintf(buf, sizeof(buf), "[%jd] ", 242 (intmax_t)time_uptime); 243 for (j = 0; buf[j] != '\0'; j++) 244 msgbuf_do_addchar(mbp, &seq, buf[j]); 245 needtime = 0; 246 } 247 248 /* 249 * Don't copy carriage returns if the caller requested 250 * filtering. 251 * 252 * XXX This matches the behavior of msglogchar(), but is it 253 * necessary? Testing has shown that we don't seem to get 254 * carriage returns here. 255 */ 256 if ((filter_cr != 0) && (str[i] == '\r')) 257 continue; 258 259 /* 260 * Clear this flag if we see a newline. This affects whether 261 * we need to insert a new prefix or insert a newline later. 262 */ 263 if (str[i] == '\n') 264 mbp->msg_flags &= ~MSGBUF_NEEDNL; 265 else 266 mbp->msg_flags |= MSGBUF_NEEDNL; 267 268 msgbuf_do_addchar(mbp, &seq, str[i]); 269 } 270 /* 271 * Update the write sequence number for the actual number of 272 * characters we put in the message buffer. (Depends on whether 273 * carriage returns are filtered.) 274 */ 275 mbp->msg_wseq = seq; 276 277 /* 278 * Set the last priority. 279 */ 280 mbp->msg_lastpri = pri; 281 282 mtx_unlock_spin(&mbp->msg_lock); 283 284 } 285 286 /* 287 * Read and mark as read a character from a message buffer. 288 * Returns the character, or -1 if no characters are available. 289 */ 290 int 291 msgbuf_getchar(struct msgbuf *mbp) 292 { 293 u_int len, wseq; 294 int c; 295 296 mtx_lock_spin(&mbp->msg_lock); 297 298 wseq = mbp->msg_wseq; 299 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq); 300 if (len == 0) { 301 mtx_unlock_spin(&mbp->msg_lock); 302 return (-1); 303 } 304 if (len > mbp->msg_size) 305 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 306 c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)]; 307 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1); 308 309 mtx_unlock_spin(&mbp->msg_lock); 310 311 return (c); 312 } 313 314 /* 315 * Read and mark as read a number of characters from a message buffer. 316 * Returns the number of characters that were placed in `buf'. 317 */ 318 int 319 msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen) 320 { 321 u_int len, pos, wseq; 322 323 mtx_lock_spin(&mbp->msg_lock); 324 325 wseq = mbp->msg_wseq; 326 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq); 327 if (len == 0) { 328 mtx_unlock_spin(&mbp->msg_lock); 329 return (0); 330 } 331 if (len > mbp->msg_size) { 332 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 333 len = mbp->msg_size; 334 } 335 pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq); 336 len = min(len, mbp->msg_size - pos); 337 len = min(len, (u_int)buflen); 338 339 bcopy(&mbp->msg_ptr[pos], buf, len); 340 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len); 341 342 mtx_unlock_spin(&mbp->msg_lock); 343 344 return (len); 345 } 346 347 /* 348 * Peek at the full contents of a message buffer without marking any 349 * data as read. `seqp' should point to an unsigned integer that 350 * msgbuf_peekbytes() can use to retain state between calls so that 351 * the whole message buffer can be read in multiple short reads. 352 * To initialise this variable to the start of the message buffer, 353 * call msgbuf_peekbytes() with a NULL `buf' parameter. 354 * 355 * Returns the number of characters that were placed in `buf'. 356 */ 357 int 358 msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp) 359 { 360 u_int len, pos, wseq; 361 362 mtx_lock_spin(&mbp->msg_lock); 363 364 if (buf == NULL) { 365 /* Just initialise *seqp. */ 366 *seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size); 367 mtx_unlock_spin(&mbp->msg_lock); 368 return (0); 369 } 370 371 wseq = mbp->msg_wseq; 372 len = MSGBUF_SEQSUB(mbp, wseq, *seqp); 373 if (len == 0) { 374 mtx_unlock_spin(&mbp->msg_lock); 375 return (0); 376 } 377 if (len > mbp->msg_size) { 378 *seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 379 len = mbp->msg_size; 380 } 381 pos = MSGBUF_SEQ_TO_POS(mbp, *seqp); 382 len = min(len, mbp->msg_size - pos); 383 len = min(len, (u_int)buflen); 384 bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len); 385 *seqp = MSGBUF_SEQNORM(mbp, *seqp + len); 386 387 mtx_unlock_spin(&mbp->msg_lock); 388 389 return (len); 390 } 391 392 /* 393 * Compute the checksum for the complete message buffer contents. 394 */ 395 static u_int 396 msgbuf_cksum(struct msgbuf *mbp) 397 { 398 u_int i, sum; 399 400 sum = 0; 401 for (i = 0; i < mbp->msg_size; i++) 402 sum += (u_char)mbp->msg_ptr[i]; 403 return (sum); 404 } 405 406 /* 407 * Copy from one message buffer to another. 408 */ 409 void 410 msgbuf_copy(struct msgbuf *src, struct msgbuf *dst) 411 { 412 int c; 413 414 while ((c = msgbuf_getchar(src)) >= 0) 415 msgbuf_addchar(dst, c); 416 } 417 418 /* 419 * Get a snapshot of the message buffer, without modifying its internal state 420 * (i.e. don't mark any new characters as read). 421 */ 422 void 423 msgbuf_duplicate(struct msgbuf *src, struct msgbuf *dst, char *dst_msgptr) 424 { 425 426 mtx_lock_spin(&src->msg_lock); 427 bcopy(src, dst, sizeof(struct msgbuf)); 428 dst->msg_ptr = dst_msgptr; 429 bcopy(src->msg_ptr, dst->msg_ptr, src->msg_size); 430 mtx_unlock_spin(&src->msg_lock); 431 } 432