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 }
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