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
51static 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 */
57static int msgbuf_show_timestamp = 0;
58SYSCTL_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 */
65void
66msgbuf_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 */
85void
86msgbuf_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 */
118void
119msgbuf_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 */
131int
132msgbuf_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
149static void
150msgbuf_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 */
165void
166msgbuf_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 */
183void
184msgbuf_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 */
290int
291msgbuf_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 */
318int
319msgbuf_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 */
357int
358msgbuf_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 */
395static u_int
396msgbuf_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 */
409void
410msgbuf_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