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: stable/11/sys/kern/subr_msgbuf.c 338109 2018-08-20 17:27:30Z kevans $
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_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 */
63void
64msgbuf_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 */
83void
84msgbuf_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 */
116void
117msgbuf_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 */
129int
130msgbuf_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
147static void
148msgbuf_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 */
163void
164msgbuf_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 */
181void
182msgbuf_addstr(struct msgbuf *mbp, int pri, const 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 */
291int
292msgbuf_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 */
319int
320msgbuf_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 */
358int
359msgbuf_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 */
396static u_int
397msgbuf_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 */
410void
411msgbuf_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}
418