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 * $FreeBSD$
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
49static 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 */
55static int msgbuf_show_timestamp = 0;
56SYSCTL_INT(_kern, OID_AUTO, msgbuf_show_timestamp, CTLFLAG_RW | CTLFLAG_TUN,
57    &msgbuf_show_timestamp, 0, "Show timestamp in msgbuf");
58TUNABLE_INT("kern.msgbuf_show_timestamp", &msgbuf_show_timestamp);
59
60/*
61 * Initialize a message buffer of the specified size at the specified
62 * location. This also zeros the buffer area.
63 */
64void
65msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
66{
67
68	mbp->msg_ptr = ptr;
69	mbp->msg_size = size;
70	mbp->msg_seqmod = SEQMOD(size);
71	msgbuf_clear(mbp);
72	mbp->msg_magic = MSG_MAGIC;
73	mbp->msg_lastpri = -1;
74	mbp->msg_flags = 0;
75	bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
76	mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
77}
78
79/*
80 * Reinitialize a message buffer, retaining its previous contents if
81 * the size and checksum are correct. If the old contents cannot be
82 * recovered, the message buffer is cleared.
83 */
84void
85msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size)
86{
87	u_int cksum;
88
89	if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) {
90		msgbuf_init(mbp, ptr, size);
91		return;
92	}
93	mbp->msg_seqmod = SEQMOD(size);
94	mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq);
95	mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq);
96        mbp->msg_ptr = ptr;
97	cksum = msgbuf_cksum(mbp);
98	if (cksum != mbp->msg_cksum) {
99		if (bootverbose) {
100			printf("msgbuf cksum mismatch (read %x, calc %x)\n",
101			    mbp->msg_cksum, cksum);
102			printf("Old msgbuf not recovered\n");
103		}
104		msgbuf_clear(mbp);
105	}
106
107	mbp->msg_lastpri = -1;
108	/* Assume that the old message buffer didn't end in a newline. */
109	mbp->msg_flags |= MSGBUF_NEEDNL;
110	bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
111	mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
112}
113
114/*
115 * Clear the message buffer.
116 */
117void
118msgbuf_clear(struct msgbuf *mbp)
119{
120
121	bzero(mbp->msg_ptr, mbp->msg_size);
122	mbp->msg_wseq = 0;
123	mbp->msg_rseq = 0;
124	mbp->msg_cksum = 0;
125}
126
127/*
128 * Get a count of the number of unread characters in the message buffer.
129 */
130int
131msgbuf_getcount(struct msgbuf *mbp)
132{
133	u_int len;
134
135	len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq);
136	if (len > mbp->msg_size)
137		len = mbp->msg_size;
138	return (len);
139}
140
141/*
142 * Add a character into the message buffer, and update the checksum and
143 * sequence number.
144 *
145 * The caller should hold the message buffer spinlock.
146 */
147
148static void
149msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c)
150{
151	u_int pos;
152
153	/* Make sure we properly wrap the sequence number. */
154	pos = MSGBUF_SEQ_TO_POS(mbp, *seq);
155	mbp->msg_cksum += (u_int)(u_char)c -
156	    (u_int)(u_char)mbp->msg_ptr[pos];
157	mbp->msg_ptr[pos] = c;
158	*seq = MSGBUF_SEQNORM(mbp, *seq + 1);
159}
160
161/*
162 * Append a character to a message buffer.
163 */
164void
165msgbuf_addchar(struct msgbuf *mbp, int c)
166{
167	mtx_lock_spin(&mbp->msg_lock);
168
169	msgbuf_do_addchar(mbp, &mbp->msg_wseq, c);
170
171	mtx_unlock_spin(&mbp->msg_lock);
172}
173
174/*
175 * Append a NUL-terminated string with a priority to a message buffer.
176 * Filter carriage returns if the caller requests it.
177 *
178 * XXX The carriage return filtering behavior is present in the
179 * msglogchar() API, however testing has shown that we don't seem to send
180 * carriage returns down this path.  So do we still need it?
181 */
182void
183msgbuf_addstr(struct msgbuf *mbp, int pri, char *str, int filter_cr)
184{
185	u_int seq;
186	size_t len, prefix_len;
187	char prefix[MAXPRIBUF];
188	char buf[32];
189	int nl, i, j, needtime;
190
191	len = strlen(str);
192	prefix_len = 0;
193	nl = 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 */
292int
293msgbuf_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 */
320int
321msgbuf_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 */
359int
360msgbuf_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 */
397static u_int
398msgbuf_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 */
411void
412msgbuf_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}
419