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: releng/12.0/sys/kern/subr_msgbuf.c 337544 2018-08-09 17:42:27Z kevans $
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
222 msgbuf_do_addchar(mbp, &seq, '\n');
223 mbp->msg_flags &= ~MSGBUF_NEEDNL;
224 }
225
226 needtime = 1;
227 for (i = 0; i < len; i++) {
228 /*
229 * If we just had a newline, and the priority is not -1
230 * (and therefore prefix_len != 0), then we need a priority
231 * prefix for this line.
232 */
233 if ((mbp->msg_flags & MSGBUF_NEEDNL) == 0 && prefix_len != 0) {
234 int j;
235
236 for (j = 0; j < prefix_len; j++)
237 msgbuf_do_addchar(mbp, &seq, prefix[j]);
238 }
239
240 if (msgbuf_show_timestamp && needtime == 1 &&
241 (mbp->msg_flags & MSGBUF_NEEDNL) == 0) {
242
243 snprintf(buf, sizeof(buf), "[%jd] ",
244 (intmax_t)time_uptime);
245 for (j = 0; buf[j] != '\0'; j++)
246 msgbuf_do_addchar(mbp, &seq, buf[j]);
247 needtime = 0;
248 }
249
250 /*
251 * Don't copy carriage returns if the caller requested
252 * filtering.
253 *
254 * XXX This matches the behavior of msglogchar(), but is it
255 * necessary? Testing has shown that we don't seem to get
256 * carriage returns here.
257 */
258 if ((filter_cr != 0) && (str[i] == '\r'))
259 continue;
260
261 /*
262 * Clear this flag if we see a newline. This affects whether
263 * we need to insert a new prefix or insert a newline later.
264 */
265 if (str[i] == '\n')
266 mbp->msg_flags &= ~MSGBUF_NEEDNL;
267 else
268 mbp->msg_flags |= MSGBUF_NEEDNL;
269
270 msgbuf_do_addchar(mbp, &seq, str[i]);
271 }
272 /*
273 * Update the write sequence number for the actual number of
274 * characters we put in the message buffer. (Depends on whether
275 * carriage returns are filtered.)
276 */
277 mbp->msg_wseq = seq;
278
279 /*
280 * Set the last priority.
281 */
282 mbp->msg_lastpri = pri;
283
284 mtx_unlock_spin(&mbp->msg_lock);
285
286 }
287
288 /*
289 * Read and mark as read a character from a message buffer.
290 * Returns the character, or -1 if no characters are available.
291 */
292 int
293 msgbuf_getchar(struct msgbuf *mbp)
294 {
295 u_int len, wseq;
296 int c;
297
298 mtx_lock_spin(&mbp->msg_lock);
299
300 wseq = mbp->msg_wseq;
301 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
302 if (len == 0) {
303 mtx_unlock_spin(&mbp->msg_lock);
304 return (-1);
305 }
306 if (len > mbp->msg_size)
307 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
308 c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)];
309 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1);
310
311 mtx_unlock_spin(&mbp->msg_lock);
312
313 return (c);
314 }
315
316 /*
317 * Read and mark as read a number of characters from a message buffer.
318 * Returns the number of characters that were placed in `buf'.
319 */
320 int
321 msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
322 {
323 u_int len, pos, wseq;
324
325 mtx_lock_spin(&mbp->msg_lock);
326
327 wseq = mbp->msg_wseq;
328 len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
329 if (len == 0) {
330 mtx_unlock_spin(&mbp->msg_lock);
331 return (0);
332 }
333 if (len > mbp->msg_size) {
334 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
335 len = mbp->msg_size;
336 }
337 pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq);
338 len = min(len, mbp->msg_size - pos);
339 len = min(len, (u_int)buflen);
340
341 bcopy(&mbp->msg_ptr[pos], buf, len);
342 mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
343
344 mtx_unlock_spin(&mbp->msg_lock);
345
346 return (len);
347 }
348
349 /*
350 * Peek at the full contents of a message buffer without marking any
351 * data as read. `seqp' should point to an unsigned integer that
352 * msgbuf_peekbytes() can use to retain state between calls so that
353 * the whole message buffer can be read in multiple short reads.
354 * To initialise this variable to the start of the message buffer,
355 * call msgbuf_peekbytes() with a NULL `buf' parameter.
356 *
357 * Returns the number of characters that were placed in `buf'.
358 */
359 int
360 msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
361 {
362 u_int len, pos, wseq;
363
364 mtx_lock_spin(&mbp->msg_lock);
365
366 if (buf == NULL) {
367 /* Just initialise *seqp. */
368 *seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
369 mtx_unlock_spin(&mbp->msg_lock);
370 return (0);
371 }
372
373 wseq = mbp->msg_wseq;
374 len = MSGBUF_SEQSUB(mbp, wseq, *seqp);
375 if (len == 0) {
376 mtx_unlock_spin(&mbp->msg_lock);
377 return (0);
378 }
379 if (len > mbp->msg_size) {
380 *seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
381 len = mbp->msg_size;
382 }
383 pos = MSGBUF_SEQ_TO_POS(mbp, *seqp);
384 len = min(len, mbp->msg_size - pos);
385 len = min(len, (u_int)buflen);
386 bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len);
387 *seqp = MSGBUF_SEQNORM(mbp, *seqp + len);
388
389 mtx_unlock_spin(&mbp->msg_lock);
390
391 return (len);
392 }
393
394 /*
395 * Compute the checksum for the complete message buffer contents.
396 */
397 static u_int
398 msgbuf_cksum(struct msgbuf *mbp)
399 {
400 u_int i, sum;
401
402 sum = 0;
403 for (i = 0; i < mbp->msg_size; i++)
404 sum += (u_char)mbp->msg_ptr[i];
405 return (sum);
406 }
407
408 /*
409 * Copy from one message buffer to another.
410 */
411 void
412 msgbuf_copy(struct msgbuf *src, struct msgbuf *dst)
413 {
414 int c;
415
416 while ((c = msgbuf_getchar(src)) >= 0)
417 msgbuf_addchar(dst, c);
418 }
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