2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
4 * Copyright (c) 2003 Ian Dowse. All rights reserved.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
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.
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
31 * Generic message buffer support routines.
34 #include <sys/param.h>
35 #include <sys/systm.h>
37 #include <sys/kernel.h>
38 #include <sys/mutex.h>
39 #include <sys/msgbuf.h>
40 #include <sys/sysctl.h>
43 * Maximum number conversion buffer length: uintmax_t in base 2, plus <>
44 * around the priority, and a terminating NUL.
46 #define MAXPRIBUF (sizeof(intmax_t) * NBBY + 3)
48 /* Read/write sequence numbers are modulo a multiple of the buffer size. */
49 #define SEQMOD(size) ((size) * 16)
51 static u_int msgbuf_cksum(struct msgbuf *mbp);
54 * Timestamps in msgbuf are useful when trying to diagnose when core dumps
55 * or other actions occurred.
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");
62 * Initialize a message buffer of the specified size at the specified
63 * location. This also zeros the buffer area.
66 msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
71 mbp->msg_seqmod = SEQMOD(size);
73 mbp->msg_magic = MSG_MAGIC;
74 mbp->msg_lastpri = -1;
76 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
77 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
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.
86 msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size)
90 if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) {
91 msgbuf_init(mbp, ptr, size);
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);
98 cksum = msgbuf_cksum(mbp);
99 if (cksum != mbp->msg_cksum) {
101 printf("msgbuf cksum mismatch (read %x, calc %x)\n",
102 mbp->msg_cksum, cksum);
103 printf("Old msgbuf not recovered\n");
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);
116 * Clear the message buffer.
119 msgbuf_clear(struct msgbuf *mbp)
122 bzero(mbp->msg_ptr, mbp->msg_size);
129 * Get a count of the number of unread characters in the message buffer.
132 msgbuf_getcount(struct msgbuf *mbp)
136 len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq);
137 if (len > mbp->msg_size)
143 * Add a character into the message buffer, and update the checksum and
146 * The caller should hold the message buffer spinlock.
150 msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c)
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);
163 * Append a character to a message buffer.
166 msgbuf_addchar(struct msgbuf *mbp, int c)
168 mtx_lock_spin(&mbp->msg_lock);
170 msgbuf_do_addchar(mbp, &mbp->msg_wseq, c);
172 mtx_unlock_spin(&mbp->msg_lock);
176 * Append a NUL-terminated string with a priority to a message buffer.
177 * Filter carriage returns if the caller requests it.
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?
184 msgbuf_addstr(struct msgbuf *mbp, int pri, const char *str, int filter_cr)
187 size_t len, prefix_len;
188 char prefix[MAXPRIBUF];
195 /* If we have a zero-length string, no need to do anything. */
199 mtx_lock_spin(&mbp->msg_lock);
202 * If this is true, we may need to insert a new priority sequence,
203 * so prepare the prefix.
206 prefix_len = sprintf(prefix, "<%d>", pri);
209 * Starting write sequence number.
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.
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;
226 for (i = 0; i < len; i++) {
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.
232 if ((mbp->msg_flags & MSGBUF_NEEDNL) == 0 && prefix_len != 0) {
235 for (j = 0; j < prefix_len; j++)
236 msgbuf_do_addchar(mbp, &seq, prefix[j]);
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]);
249 * Don't copy carriage returns if the caller requested
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.
256 if ((filter_cr != 0) && (str[i] == '\r'))
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.
264 mbp->msg_flags &= ~MSGBUF_NEEDNL;
266 mbp->msg_flags |= MSGBUF_NEEDNL;
268 msgbuf_do_addchar(mbp, &seq, str[i]);
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.)
278 * Set the last priority.
280 mbp->msg_lastpri = pri;
282 mtx_unlock_spin(&mbp->msg_lock);
287 * Read and mark as read a character from a message buffer.
288 * Returns the character, or -1 if no characters are available.
291 msgbuf_getchar(struct msgbuf *mbp)
296 mtx_lock_spin(&mbp->msg_lock);
298 wseq = mbp->msg_wseq;
299 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
301 mtx_unlock_spin(&mbp->msg_lock);
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);
309 mtx_unlock_spin(&mbp->msg_lock);
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'.
319 msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
321 u_int len, pos, wseq;
323 mtx_lock_spin(&mbp->msg_lock);
325 wseq = mbp->msg_wseq;
326 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
328 mtx_unlock_spin(&mbp->msg_lock);
331 if (len > mbp->msg_size) {
332 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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);
339 bcopy(&mbp->msg_ptr[pos], buf, len);
340 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
342 mtx_unlock_spin(&mbp->msg_lock);
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.
355 * Returns the number of characters that were placed in `buf'.
358 msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
360 u_int len, pos, wseq;
362 mtx_lock_spin(&mbp->msg_lock);
365 /* Just initialise *seqp. */
366 *seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
367 mtx_unlock_spin(&mbp->msg_lock);
371 wseq = mbp->msg_wseq;
372 len = MSGBUF_SEQSUB(mbp, wseq, *seqp);
374 mtx_unlock_spin(&mbp->msg_lock);
377 if (len > mbp->msg_size) {
378 *seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
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);
387 mtx_unlock_spin(&mbp->msg_lock);
393 * Compute the checksum for the complete message buffer contents.
396 msgbuf_cksum(struct msgbuf *mbp)
401 for (i = 0; i < mbp->msg_size; i++)
402 sum += (u_char)mbp->msg_ptr[i];
407 * Copy from one message buffer to another.
410 msgbuf_copy(struct msgbuf *src, struct msgbuf *dst)
414 while ((c = msgbuf_getchar(src)) >= 0)
415 msgbuf_addchar(dst, c);
419 * Get a snapshot of the message buffer, without modifying its internal state
420 * (i.e. don't mark any new characters as read).
423 msgbuf_duplicate(struct msgbuf *src, struct msgbuf *dst, char *dst_msgptr)
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);