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: releng/11.0/sys/kern/subr_msgbuf.c 298819 2016-04-29 22:15:33Z pfg $
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/kernel.h>
36 #include <sys/mutex.h>
37 #include <sys/msgbuf.h>
38 #include <sys/sysctl.h>
39
40 /*
41 * Maximum number conversion buffer length: uintmax_t in base 2, plus <>
42 * around the priority, and a terminating NUL.
43 */
44 #define MAXPRIBUF (sizeof(intmax_t) * NBBY + 3)
45
46 /* Read/write sequence numbers are modulo a multiple of the buffer size. */
47 #define SEQMOD(size) ((size) * 16)
48
49 static u_int msgbuf_cksum(struct msgbuf *mbp);
50
51 /*
52 * Timestamps in msgbuf are useful when trying to diagnose when core dumps
53 * or other actions occurred.
54 */
55 static int msgbuf_show_timestamp = 0;
56 SYSCTL_INT(_kern, OID_AUTO, msgbuf_show_timestamp, CTLFLAG_RWTUN,
57 &msgbuf_show_timestamp, 0, "Show timestamp in msgbuf");
58
59 /*
60 * Initialize a message buffer of the specified size at the specified
61 * location. This also zeros the buffer area.
62 */
63 void
64 msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
65 {
66
67 mbp->msg_ptr = ptr;
68 mbp->msg_size = size;
69 mbp->msg_seqmod = SEQMOD(size);
70 msgbuf_clear(mbp);
71 mbp->msg_magic = MSG_MAGIC;
72 mbp->msg_lastpri = -1;
73 mbp->msg_flags = 0;
74 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
75 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
76 }
77
78 /*
79 * Reinitialize a message buffer, retaining its previous contents if
80 * the size and checksum are correct. If the old contents cannot be
81 * recovered, the message buffer is cleared.
82 */
83 void
84 msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size)
85 {
86 u_int cksum;
87
88 if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) {
89 msgbuf_init(mbp, ptr, size);
90 return;
91 }
92 mbp->msg_seqmod = SEQMOD(size);
93 mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq);
94 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq);
95 mbp->msg_ptr = ptr;
96 cksum = msgbuf_cksum(mbp);
97 if (cksum != mbp->msg_cksum) {
98 if (bootverbose) {
99 printf("msgbuf cksum mismatch (read %x, calc %x)\n",
100 mbp->msg_cksum, cksum);
101 printf("Old msgbuf not recovered\n");
102 }
103 msgbuf_clear(mbp);
104 }
105
106 mbp->msg_lastpri = -1;
107 /* Assume that the old message buffer didn't end in a newline. */
108 mbp->msg_flags |= MSGBUF_NEEDNL;
109 bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
110 mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
111 }
112
113 /*
114 * Clear the message buffer.
115 */
116 void
117 msgbuf_clear(struct msgbuf *mbp)
118 {
119
120 bzero(mbp->msg_ptr, mbp->msg_size);
121 mbp->msg_wseq = 0;
122 mbp->msg_rseq = 0;
123 mbp->msg_cksum = 0;
124 }
125
126 /*
127 * Get a count of the number of unread characters in the message buffer.
128 */
129 int
130 msgbuf_getcount(struct msgbuf *mbp)
131 {
132 u_int len;
133
134 len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq);
135 if (len > mbp->msg_size)
136 len = mbp->msg_size;
137 return (len);
138 }
139
140 /*
141 * Add a character into the message buffer, and update the checksum and
142 * sequence number.
143 *
144 * The caller should hold the message buffer spinlock.
145 */
146
147 static void
148 msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c)
149 {
150 u_int pos;
151
152 /* Make sure we properly wrap the sequence number. */
153 pos = MSGBUF_SEQ_TO_POS(mbp, *seq);
154 mbp->msg_cksum += (u_int)(u_char)c -
155 (u_int)(u_char)mbp->msg_ptr[pos];
156 mbp->msg_ptr[pos] = c;
157 *seq = MSGBUF_SEQNORM(mbp, *seq + 1);
158 }
159
160 /*
161 * Append a character to a message buffer.
162 */
163 void
164 msgbuf_addchar(struct msgbuf *mbp, int c)
165 {
166 mtx_lock_spin(&mbp->msg_lock);
167
168 msgbuf_do_addchar(mbp, &mbp->msg_wseq, c);
169
170 mtx_unlock_spin(&mbp->msg_lock);
171 }
172
173 /*
174 * Append a NUL-terminated string with a priority to a message buffer.
175 * Filter carriage returns if the caller requests it.
176 *
177 * XXX The carriage return filtering behavior is present in the
178 * msglogchar() API, however testing has shown that we don't seem to send
179 * carriage returns down this path. So do we still need it?
180 */
181 void
182 msgbuf_addstr(struct msgbuf *mbp, int pri, char *str, int filter_cr)
183 {
184 u_int seq;
185 size_t len, prefix_len;
186 char prefix[MAXPRIBUF];
187 char buf[32];
188 int nl, i, j, needtime;
189
190 len = strlen(str);
191 prefix_len = 0;
192 nl = 0;
193
194 /* If we have a zero-length string, no need to do anything. */
195 if (len == 0)
196 return;
197
198 mtx_lock_spin(&mbp->msg_lock);
199
200 /*
201 * If this is true, we may need to insert a new priority sequence,
202 * so prepare the prefix.
203 */
204 if (pri != -1)
205 prefix_len = sprintf(prefix, "<%d>", pri);
206
207 /*
208 * Starting write sequence number.
209 */
210 seq = mbp->msg_wseq;
211
212 /*
213 * Whenever there is a change in priority, we have to insert a
214 * newline, and a priority prefix if the priority is not -1. Here
215 * we detect whether there was a priority change, and whether we
216 * did not end with a newline. If that is the case, we need to
217 * insert a newline before this string.
218 */
219 if (mbp->msg_lastpri != pri && (mbp->msg_flags & MSGBUF_NEEDNL) != 0) {
220
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
242 snprintf(buf, sizeof(buf), "[%jd] ",
243 (intmax_t)time_uptime);
244 for (j = 0; buf[j] != '\0'; j++)
245 msgbuf_do_addchar(mbp, &seq, buf[j]);
246 needtime = 0;
247 }
248
249 /*
250 * Don't copy carriage returns if the caller requested
251 * filtering.
252 *
253 * XXX This matches the behavior of msglogchar(), but is it
254 * necessary? Testing has shown that we don't seem to get
255 * carriage returns here.
256 */
257 if ((filter_cr != 0) && (str[i] == '\r'))
258 continue;
259
260 /*
261 * Clear this flag if we see a newline. This affects whether
262 * we need to insert a new prefix or insert a newline later.
263 */
264 if (str[i] == '\n')
265 mbp->msg_flags &= ~MSGBUF_NEEDNL;
266 else
267 mbp->msg_flags |= MSGBUF_NEEDNL;
268
269 msgbuf_do_addchar(mbp, &seq, str[i]);
270 }
271 /*
272 * Update the write sequence number for the actual number of
273 * characters we put in the message buffer. (Depends on whether
274 * carriage returns are filtered.)
275 */
276 mbp->msg_wseq = seq;
277
278 /*
279 * Set the last priority.
280 */
281 mbp->msg_lastpri = pri;
282
283 mtx_unlock_spin(&mbp->msg_lock);
284
285 }
286
287 /*
288 * Read and mark as read a character from a message buffer.
289 * Returns the character, or -1 if no characters are available.
290 */
291 int
292 msgbuf_getchar(struct msgbuf *mbp)
293 {
294 u_int len, wseq;
295 int c;
296
297 mtx_lock_spin(&mbp->msg_lock);
298
299 wseq = mbp->msg_wseq;
300 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
301 if (len == 0) {
302 mtx_unlock_spin(&mbp->msg_lock);
303 return (-1);
304 }
305 if (len > mbp->msg_size)
306 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
307 c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)];
308 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1);
309
310 mtx_unlock_spin(&mbp->msg_lock);
311
312 return (c);
313 }
314
315 /*
316 * Read and mark as read a number of characters from a message buffer.
317 * Returns the number of characters that were placed in `buf'.
318 */
319 int
320 msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
321 {
322 u_int len, pos, wseq;
323
324 mtx_lock_spin(&mbp->msg_lock);
325
326 wseq = mbp->msg_wseq;
327 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
328 if (len == 0) {
329 mtx_unlock_spin(&mbp->msg_lock);
330 return (0);
331 }
332 if (len > mbp->msg_size) {
333 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
334 len = mbp->msg_size;
335 }
336 pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq);
337 len = min(len, mbp->msg_size - pos);
338 len = min(len, (u_int)buflen);
339
340 bcopy(&mbp->msg_ptr[pos], buf, len);
341 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
342
343 mtx_unlock_spin(&mbp->msg_lock);
344
345 return (len);
346 }
347
348 /*
349 * Peek at the full contents of a message buffer without marking any
350 * data as read. `seqp' should point to an unsigned integer that
351 * msgbuf_peekbytes() can use to retain state between calls so that
352 * the whole message buffer can be read in multiple short reads.
353 * To initialise this variable to the start of the message buffer,
354 * call msgbuf_peekbytes() with a NULL `buf' parameter.
355 *
356 * Returns the number of characters that were placed in `buf'.
357 */
358 int
359 msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
360 {
361 u_int len, pos, wseq;
362
363 mtx_lock_spin(&mbp->msg_lock);
364
365 if (buf == NULL) {
366 /* Just initialise *seqp. */
367 *seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
368 mtx_unlock_spin(&mbp->msg_lock);
369 return (0);
370 }
371
372 wseq = mbp->msg_wseq;
373 len = MSGBUF_SEQSUB(mbp, wseq, *seqp);
374 if (len == 0) {
375 mtx_unlock_spin(&mbp->msg_lock);
376 return (0);
377 }
378 if (len > mbp->msg_size) {
379 *seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
380 len = mbp->msg_size;
381 }
382 pos = MSGBUF_SEQ_TO_POS(mbp, *seqp);
383 len = min(len, mbp->msg_size - pos);
384 len = min(len, (u_int)buflen);
385 bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len);
386 *seqp = MSGBUF_SEQNORM(mbp, *seqp + len);
387
388 mtx_unlock_spin(&mbp->msg_lock);
389
390 return (len);
391 }
392
393 /*
394 * Compute the checksum for the complete message buffer contents.
395 */
396 static u_int
397 msgbuf_cksum(struct msgbuf *mbp)
398 {
399 u_int i, sum;
400
401 sum = 0;
402 for (i = 0; i < mbp->msg_size; i++)
403 sum += (u_char)mbp->msg_ptr[i];
404 return (sum);
405 }
406
407 /*
408 * Copy from one message buffer to another.
409 */
410 void
411 msgbuf_copy(struct msgbuf *src, struct msgbuf *dst)
412 {
413 int c;
414
415 while ((c = msgbuf_getchar(src)) >= 0)
416 msgbuf_addchar(dst, c);
417 }
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