subr_msgbuf.c revision 222550
1/*- 2 * Copyright (c) 2003 Ian Dowse. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23 * SUCH DAMAGE. 24 * 25 * $FreeBSD: head/sys/kern/subr_msgbuf.c 222550 2011-05-31 22:39:32Z ken $ 26 */ 27 28/* 29 * Generic message buffer support routines. 30 */ 31 32#include <sys/param.h> 33#include <sys/systm.h> 34#include <sys/lock.h> 35#include <sys/mutex.h> 36#include <sys/msgbuf.h> 37 38/* 39 * Maximum number conversion buffer length: uintmax_t in base 2, plus <> 40 * around the priority, and a terminating NUL. 41 */ 42#define MAXPRIBUF (sizeof(intmax_t) * NBBY + 3) 43 44/* Read/write sequence numbers are modulo a multiple of the buffer size. */ 45#define SEQMOD(size) ((size) * 16) 46 47static u_int msgbuf_cksum(struct msgbuf *mbp); 48 49/* 50 * Initialize a message buffer of the specified size at the specified 51 * location. This also zeros the buffer area. 52 */ 53void 54msgbuf_init(struct msgbuf *mbp, void *ptr, int size) 55{ 56 57 mbp->msg_ptr = ptr; 58 mbp->msg_size = size; 59 mbp->msg_seqmod = SEQMOD(size); 60 msgbuf_clear(mbp); 61 mbp->msg_magic = MSG_MAGIC; 62 mbp->msg_lastpri = -1; 63 mbp->msg_needsnl = 0; 64 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); 65 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); 66} 67 68/* 69 * Reinitialize a message buffer, retaining its previous contents if 70 * the size and checksum are correct. If the old contents cannot be 71 * recovered, the message buffer is cleared. 72 */ 73void 74msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size) 75{ 76 u_int cksum; 77 78 if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) { 79 msgbuf_init(mbp, ptr, size); 80 return; 81 } 82 mbp->msg_seqmod = SEQMOD(size); 83 mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq); 84 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq); 85 mbp->msg_ptr = ptr; 86 cksum = msgbuf_cksum(mbp); 87 if (cksum != mbp->msg_cksum) { 88 if (bootverbose) { 89 printf("msgbuf cksum mismatch (read %x, calc %x)\n", 90 mbp->msg_cksum, cksum); 91 printf("Old msgbuf not recovered\n"); 92 } 93 msgbuf_clear(mbp); 94 } 95 96 mbp->msg_lastpri = -1; 97 /* Assume that the old message buffer didn't end in a newline. */ 98 mbp->msg_needsnl = 1; 99 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock)); 100 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN); 101} 102 103/* 104 * Clear the message buffer. 105 */ 106void 107msgbuf_clear(struct msgbuf *mbp) 108{ 109 110 bzero(mbp->msg_ptr, mbp->msg_size); 111 mbp->msg_wseq = 0; 112 mbp->msg_rseq = 0; 113 mbp->msg_cksum = 0; 114} 115 116/* 117 * Get a count of the number of unread characters in the message buffer. 118 */ 119int 120msgbuf_getcount(struct msgbuf *mbp) 121{ 122 u_int len; 123 124 len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq); 125 if (len > mbp->msg_size) 126 len = mbp->msg_size; 127 return (len); 128} 129 130/* 131 * Add a character into the message buffer, and update the checksum and 132 * sequence number. 133 * 134 * The caller should hold the message buffer spinlock. 135 */ 136static inline void 137msgbuf_do_addchar(struct msgbuf *mbp, u_int *seq, int c) 138{ 139 u_int pos; 140 141 /* Make sure we properly wrap the sequence number. */ 142 pos = MSGBUF_SEQ_TO_POS(mbp, *seq); 143 144 mbp->msg_cksum += (u_int)c - 145 (u_int)(u_char)mbp->msg_ptr[pos]; 146 147 mbp->msg_ptr[pos] = c; 148 149 *seq = MSGBUF_SEQNORM(mbp, *seq + 1); 150} 151 152/* 153 * Append a character to a message buffer. 154 */ 155void 156msgbuf_addchar(struct msgbuf *mbp, int c) 157{ 158 mtx_lock_spin(&mbp->msg_lock); 159 160 msgbuf_do_addchar(mbp, &mbp->msg_wseq, c); 161 162 mtx_unlock_spin(&mbp->msg_lock); 163} 164 165/* 166 * Append a NUL-terminated string with a priority to a message buffer. 167 * Filter carriage returns if the caller requests it. 168 * 169 * XXX The carriage return filtering behavior is present in the 170 * msglogchar() API, however testing has shown that we don't seem to send 171 * carriage returns down this path. So do we still need it? 172 */ 173void 174msgbuf_addstr(struct msgbuf *mbp, int pri, char *str, int filter_cr) 175{ 176 u_int seq; 177 size_t len, prefix_len; 178 char prefix[MAXPRIBUF]; 179 int nl, i; 180 181 len = strlen(str); 182 prefix_len = 0; 183 nl = 0; 184 185 /* If we have a zero-length string, no need to do anything. */ 186 if (len == 0) 187 return; 188 189 mtx_lock_spin(&mbp->msg_lock); 190 191 /* 192 * If this is true, we may need to insert a new priority sequence, 193 * so prepare the prefix. 194 */ 195 if (pri != -1) 196 prefix_len = sprintf(prefix, "<%d>", pri); 197 198 /* 199 * Starting write sequence number. 200 */ 201 seq = mbp->msg_wseq; 202 203 /* 204 * Whenever there is a change in priority, we have to insert a 205 * newline, and a priority prefix if the priority is not -1. Here 206 * we detect whether there was a priority change, and whether we 207 * did not end with a newline. If that is the case, we need to 208 * insert a newline before this string. 209 */ 210 if (mbp->msg_lastpri != pri && mbp->msg_needsnl != 0) { 211 212 msgbuf_do_addchar(mbp, &seq, '\n'); 213 mbp->msg_needsnl = 0; 214 } 215 216 for (i = 0; i < len; i++) { 217 /* 218 * If we just had a newline, and the priority is not -1 219 * (and therefore prefix_len != 0), then we need a priority 220 * prefix for this line. 221 */ 222 if (mbp->msg_needsnl == 0 && prefix_len != 0) { 223 int j; 224 225 for (j = 0; j < prefix_len; j++) 226 msgbuf_do_addchar(mbp, &seq, prefix[j]); 227 } 228 229 /* 230 * Don't copy carriage returns if the caller requested 231 * filtering. 232 * 233 * XXX This matches the behavior of msglogchar(), but is it 234 * necessary? Testing has shown that we don't seem to get 235 * carriage returns here. 236 */ 237 if ((filter_cr != 0) && (str[i] == '\r')) 238 continue; 239 240 /* 241 * Clear this flag if we see a newline. This affects whether 242 * we need to insert a new prefix or insert a newline later. 243 */ 244 if (str[i] == '\n') 245 mbp->msg_needsnl = 0; 246 else 247 mbp->msg_needsnl = 1; 248 249 msgbuf_do_addchar(mbp, &seq, str[i]); 250 } 251 /* 252 * Update the write sequence number for the actual number of 253 * characters we put in the message buffer. (Depends on whether 254 * carriage returns are filtered.) 255 */ 256 mbp->msg_wseq = seq; 257 258 /* 259 * Set the last priority. 260 */ 261 mbp->msg_lastpri = pri; 262 263 mtx_unlock_spin(&mbp->msg_lock); 264 265} 266 267/* 268 * Read and mark as read a character from a message buffer. 269 * Returns the character, or -1 if no characters are available. 270 */ 271int 272msgbuf_getchar(struct msgbuf *mbp) 273{ 274 u_int len, wseq; 275 int c; 276 277 mtx_lock_spin(&mbp->msg_lock); 278 279 wseq = mbp->msg_wseq; 280 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq); 281 if (len == 0) { 282 mtx_unlock_spin(&mbp->msg_lock); 283 return (-1); 284 } 285 if (len > mbp->msg_size) 286 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 287 c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)]; 288 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1); 289 290 mtx_unlock_spin(&mbp->msg_lock); 291 292 return (c); 293} 294 295/* 296 * Read and mark as read a number of characters from a message buffer. 297 * Returns the number of characters that were placed in `buf'. 298 */ 299int 300msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen) 301{ 302 u_int len, pos, wseq; 303 304 mtx_lock_spin(&mbp->msg_lock); 305 306 wseq = mbp->msg_wseq; 307 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq); 308 if (len == 0) { 309 mtx_unlock_spin(&mbp->msg_lock); 310 return (0); 311 } 312 if (len > mbp->msg_size) { 313 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 314 len = mbp->msg_size; 315 } 316 pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq); 317 len = min(len, mbp->msg_size - pos); 318 len = min(len, (u_int)buflen); 319 320 bcopy(&mbp->msg_ptr[pos], buf, len); 321 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len); 322 323 mtx_unlock_spin(&mbp->msg_lock); 324 325 return (len); 326} 327 328/* 329 * Peek at the full contents of a message buffer without marking any 330 * data as read. `seqp' should point to an unsigned integer that 331 * msgbuf_peekbytes() can use to retain state between calls so that 332 * the whole message buffer can be read in multiple short reads. 333 * To initialise this variable to the start of the message buffer, 334 * call msgbuf_peekbytes() with a NULL `buf' parameter. 335 * 336 * Returns the number of characters that were placed in `buf'. 337 */ 338int 339msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp) 340{ 341 u_int len, pos, wseq; 342 343 mtx_lock_spin(&mbp->msg_lock); 344 345 if (buf == NULL) { 346 /* Just initialise *seqp. */ 347 *seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size); 348 mtx_unlock_spin(&mbp->msg_lock); 349 return (0); 350 } 351 352 wseq = mbp->msg_wseq; 353 len = MSGBUF_SEQSUB(mbp, wseq, *seqp); 354 if (len == 0) { 355 mtx_unlock_spin(&mbp->msg_lock); 356 return (0); 357 } 358 if (len > mbp->msg_size) { 359 *seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size); 360 len = mbp->msg_size; 361 } 362 pos = MSGBUF_SEQ_TO_POS(mbp, *seqp); 363 len = min(len, mbp->msg_size - pos); 364 len = min(len, (u_int)buflen); 365 bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len); 366 *seqp = MSGBUF_SEQNORM(mbp, *seqp + len); 367 368 mtx_unlock_spin(&mbp->msg_lock); 369 370 return (len); 371} 372 373/* 374 * Compute the checksum for the complete message buffer contents. 375 */ 376static u_int 377msgbuf_cksum(struct msgbuf *mbp) 378{ 379 u_int i, sum; 380 381 sum = 0; 382 for (i = 0; i < mbp->msg_size; i++) 383 sum += (u_char)mbp->msg_ptr[i]; 384 return (sum); 385} 386 387/* 388 * Copy from one message buffer to another. 389 */ 390void 391msgbuf_copy(struct msgbuf *src, struct msgbuf *dst) 392{ 393 int c; 394 395 while ((c = msgbuf_getchar(src)) >= 0) 396 msgbuf_addchar(dst, c); 397} 398