1 files changed, 418 insertions, 0 deletions
diff --git a/sys/kern/subr_msgbuf.c b/sys/kern/subr_msgbuf.c
new file mode 100644
index 0000000..ecdbe72
--- /dev/null
+++ b/sys/kern/subr_msgbuf.c
@@ -0,0 +1,418 @@
+/*-
+ * Copyright (c) 2003 Ian Dowse.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Generic message buffer support routines.
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/lock.h>
+#include <sys/kernel.h>
+#include <sys/mutex.h>
+#include <sys/msgbuf.h>
+#include <sys/sysctl.h>
+
+/*
+ * Maximum number conversion buffer length: uintmax_t in base 2, plus <>
+ * around the priority, and a terminating NUL.
+ */
+#define	MAXPRIBUF	(sizeof(intmax_t) * NBBY + 3)
+
+/* Read/write sequence numbers are modulo a multiple of the buffer size. */
+#define SEQMOD(size) ((size) * 16)
+
+static u_int msgbuf_cksum(struct msgbuf *mbp);
+
+/*
+ * Timestamps in msgbuf are useful when trying to diagnose when core dumps
+ * or other actions occured.
+ */
+static int msgbuf_show_timestamp = 0;
+SYSCTL_INT(_kern, OID_AUTO, msgbuf_show_timestamp, CTLFLAG_RW | CTLFLAG_TUN,
+    &msgbuf_show_timestamp, 0, "Show timestamp in msgbuf");
+TUNABLE_INT("kern.msgbuf_show_timestamp", &msgbuf_show_timestamp);
+
+/*
+ * Initialize a message buffer of the specified size at the specified
+ * location. This also zeros the buffer area.
+ */
+void
+msgbuf_init(struct msgbuf *mbp, void *ptr, int size)
+{
+
+	mbp->msg_ptr = ptr;
+	mbp->msg_size = size;
+	mbp->msg_seqmod = SEQMOD(size);
+	msgbuf_clear(mbp);
+	mbp->msg_magic = MSG_MAGIC;
+	mbp->msg_lastpri = -1;
+	mbp->msg_flags = 0;
+	bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
+	mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
+}
+
+/*
+ * Reinitialize a message buffer, retaining its previous contents if
+ * the size and checksum are correct. If the old contents cannot be
+ * recovered, the message buffer is cleared.
+ */
+void
+msgbuf_reinit(struct msgbuf *mbp, void *ptr, int size)
+{
+	u_int cksum;
+
+	if (mbp->msg_magic != MSG_MAGIC || mbp->msg_size != size) {
+		msgbuf_init(mbp, ptr, size);
+		return;
+	}
+	mbp->msg_seqmod = SEQMOD(size);
+	mbp->msg_wseq = MSGBUF_SEQNORM(mbp, mbp->msg_wseq);
+	mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq);
+        mbp->msg_ptr = ptr;
+	cksum = msgbuf_cksum(mbp);
+	if (cksum != mbp->msg_cksum) {
+		if (bootverbose) {
+			printf("msgbuf cksum mismatch (read %x, calc %x)\n",
+			    mbp->msg_cksum, cksum);
+			printf("Old msgbuf not recovered\n");
+		}
+		msgbuf_clear(mbp);
+	}
+
+	mbp->msg_lastpri = -1;
+	/* Assume that the old message buffer didn't end in a newline. */
+	mbp->msg_flags |= MSGBUF_NEEDNL;
+	bzero(&mbp->msg_lock, sizeof(mbp->msg_lock));
+	mtx_init(&mbp->msg_lock, "msgbuf", NULL, MTX_SPIN);
+}
+
+/*
+ * Clear the message buffer.
+ */
+void
+msgbuf_clear(struct msgbuf *mbp)
+{
+
+	bzero(mbp->msg_ptr, mbp->msg_size);
+	mbp->msg_wseq = 0;
+	mbp->msg_rseq = 0;
+	mbp->msg_cksum = 0;
+}
+
+/*
+ * Get a count of the number of unread characters in the message buffer.
+ */
+int
+msgbuf_getcount(struct msgbuf *mbp)
+{
+	u_int len;
+
+	len = MSGBUF_SEQSUB(mbp, mbp->msg_wseq, mbp->msg_rseq);
+	if (len > mbp->msg_size)
+		len = mbp->msg_size;
+	return (len);
+}
+
+/*
+ * Add a character into the message buffer, and update the checksum and
+ * sequence number.
+ *
+ * The caller should hold the message buffer spinlock.
+ */
+
+static void
+msgbuf_do_addchar(struct msgbuf * const mbp, u_int * const seq, const int c)
+{
+	u_int pos;
+
+	/* Make sure we properly wrap the sequence number. */
+	pos = MSGBUF_SEQ_TO_POS(mbp, *seq);
+	mbp->msg_cksum += (u_int)(u_char)c -
+	    (u_int)(u_char)mbp->msg_ptr[pos];
+	mbp->msg_ptr[pos] = c;
+	*seq = MSGBUF_SEQNORM(mbp, *seq + 1);
+}
+
+/*
+ * Append a character to a message buffer.
+ */
+void
+msgbuf_addchar(struct msgbuf *mbp, int c)
+{
+	mtx_lock_spin(&mbp->msg_lock);
+
+	msgbuf_do_addchar(mbp, &mbp->msg_wseq, c);
+
+	mtx_unlock_spin(&mbp->msg_lock);
+}
+
+/*
+ * Append a NUL-terminated string with a priority to a message buffer.
+ * Filter carriage returns if the caller requests it.
+ *
+ * XXX The carriage return filtering behavior is present in the
+ * msglogchar() API, however testing has shown that we don't seem to send
+ * carriage returns down this path.  So do we still need it?
+ */
+void
+msgbuf_addstr(struct msgbuf *mbp, int pri, char *str, int filter_cr)
+{
+	u_int seq;
+	size_t len, prefix_len;
+	char prefix[MAXPRIBUF];
+	char buf[32];
+	int nl, i, j, needtime;
+
+	len = strlen(str);
+	prefix_len = 0;
+	nl = 0;
+
+	/* If we have a zero-length string, no need to do anything. */
+	if (len == 0)
+		return;
+
+	mtx_lock_spin(&mbp->msg_lock);
+
+	/*
+	 * If this is true, we may need to insert a new priority sequence,
+	 * so prepare the prefix.
+	 */
+	if (pri != -1)
+		prefix_len = sprintf(prefix, "<%d>", pri);
+
+	/*
+	 * Starting write sequence number.
+	 */
+	seq = mbp->msg_wseq;
+
+	/*
+	 * Whenever there is a change in priority, we have to insert a
+	 * newline, and a priority prefix if the priority is not -1.  Here
+	 * we detect whether there was a priority change, and whether we
+	 * did not end with a newline.  If that is the case, we need to
+	 * insert a newline before this string.
+	 */
+	if (mbp->msg_lastpri != pri && (mbp->msg_flags & MSGBUF_NEEDNL) != 0) {
+
+		msgbuf_do_addchar(mbp, &seq, '\n');
+		mbp->msg_flags &= ~MSGBUF_NEEDNL;
+	}
+
+	needtime = 1;
+	for (i = 0; i < len; i++) {
+		/*
+		 * If we just had a newline, and the priority is not -1
+		 * (and therefore prefix_len != 0), then we need a priority
+		 * prefix for this line.
+		 */
+		if ((mbp->msg_flags & MSGBUF_NEEDNL) == 0 && prefix_len != 0) {
+			int j;
+
+			for (j = 0; j < prefix_len; j++)
+				msgbuf_do_addchar(mbp, &seq, prefix[j]);
+		}
+
+		if (msgbuf_show_timestamp && needtime == 1 &&
+		    (mbp->msg_flags & MSGBUF_NEEDNL) == 0) {
+
+			snprintf(buf, sizeof(buf), "[%jd] ",
+			    (intmax_t)time_uptime);
+			for (j = 0; buf[j] != '\0'; j++)
+				msgbuf_do_addchar(mbp, &seq, buf[j]);
+			needtime = 0;
+		}
+
+		/*
+		 * Don't copy carriage returns if the caller requested
+		 * filtering.
+		 * 
+		 * XXX This matches the behavior of msglogchar(), but is it
+		 * necessary?  Testing has shown that we don't seem to get
+		 * carriage returns here.
+		 */
+		if ((filter_cr != 0) && (str[i] == '\r'))
+			continue;
+
+		/*
+		 * Clear this flag if we see a newline.  This affects whether
+		 * we need to insert a new prefix or insert a newline later.
+		 */
+		if (str[i] == '\n')
+			mbp->msg_flags &= ~MSGBUF_NEEDNL;
+		else
+			mbp->msg_flags |= MSGBUF_NEEDNL;
+
+		msgbuf_do_addchar(mbp, &seq, str[i]);
+	}
+	/*
+	 * Update the write sequence number for the actual number of
+	 * characters we put in the message buffer.  (Depends on whether
+	 * carriage returns are filtered.)
+	 */
+	mbp->msg_wseq = seq;
+
+	/*
+	 * Set the last priority.
+	 */
+	mbp->msg_lastpri = pri;
+
+	mtx_unlock_spin(&mbp->msg_lock);
+
+}
+
+/*
+ * Read and mark as read a character from a message buffer.
+ * Returns the character, or -1 if no characters are available.
+ */
+int
+msgbuf_getchar(struct msgbuf *mbp)
+{
+	u_int len, wseq;
+	int c;
+
+	mtx_lock_spin(&mbp->msg_lock);
+
+	wseq = mbp->msg_wseq;
+	len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
+	if (len == 0) {
+		mtx_unlock_spin(&mbp->msg_lock);
+		return (-1);
+	}
+	if (len > mbp->msg_size)
+		mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
+	c = (u_char)mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq)];
+	mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + 1);
+
+	mtx_unlock_spin(&mbp->msg_lock);
+
+	return (c);
+}
+
+/*
+ * Read and mark as read a number of characters from a message buffer.
+ * Returns the number of characters that were placed in `buf'.
+ */
+int
+msgbuf_getbytes(struct msgbuf *mbp, char *buf, int buflen)
+{
+	u_int len, pos, wseq;
+
+	mtx_lock_spin(&mbp->msg_lock);
+
+	wseq = mbp->msg_wseq;
+	len = MSGBUF_SEQSUB(mbp, wseq, mbp->msg_rseq);
+	if (len == 0) {
+		mtx_unlock_spin(&mbp->msg_lock);
+		return (0);
+	}
+	if (len > mbp->msg_size) {
+		mbp->msg_rseq = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
+		len = mbp->msg_size;
+	}
+	pos = MSGBUF_SEQ_TO_POS(mbp, mbp->msg_rseq);
+	len = min(len, mbp->msg_size - pos);
+	len = min(len, (u_int)buflen);
+
+	bcopy(&mbp->msg_ptr[pos], buf, len);
+	mbp->msg_rseq = MSGBUF_SEQNORM(mbp, mbp->msg_rseq + len);
+
+	mtx_unlock_spin(&mbp->msg_lock);
+
+	return (len);
+}
+
+/*
+ * Peek at the full contents of a message buffer without marking any
+ * data as read. `seqp' should point to an unsigned integer that
+ * msgbuf_peekbytes() can use to retain state between calls so that
+ * the whole message buffer can be read in multiple short reads.
+ * To initialise this variable to the start of the message buffer,
+ * call msgbuf_peekbytes() with a NULL `buf' parameter.
+ *
+ * Returns the number of characters that were placed in `buf'.
+ */
+int
+msgbuf_peekbytes(struct msgbuf *mbp, char *buf, int buflen, u_int *seqp)
+{
+	u_int len, pos, wseq;
+
+	mtx_lock_spin(&mbp->msg_lock);
+
+	if (buf == NULL) {
+		/* Just initialise *seqp. */
+		*seqp = MSGBUF_SEQNORM(mbp, mbp->msg_wseq - mbp->msg_size);
+		mtx_unlock_spin(&mbp->msg_lock);
+		return (0);
+	}
+
+	wseq = mbp->msg_wseq;
+	len = MSGBUF_SEQSUB(mbp, wseq, *seqp);
+	if (len == 0) {
+		mtx_unlock_spin(&mbp->msg_lock);
+		return (0);
+	}
+	if (len > mbp->msg_size) {
+		*seqp = MSGBUF_SEQNORM(mbp, wseq - mbp->msg_size);
+		len = mbp->msg_size;
+	}
+	pos = MSGBUF_SEQ_TO_POS(mbp, *seqp);
+	len = min(len, mbp->msg_size - pos);
+	len = min(len, (u_int)buflen);
+	bcopy(&mbp->msg_ptr[MSGBUF_SEQ_TO_POS(mbp, *seqp)], buf, len);
+	*seqp = MSGBUF_SEQNORM(mbp, *seqp + len);
+
+	mtx_unlock_spin(&mbp->msg_lock);
+
+	return (len);
+}
+
+/*
+ * Compute the checksum for the complete message buffer contents.
+ */
+static u_int
+msgbuf_cksum(struct msgbuf *mbp)
+{
+	u_int i, sum;
+
+	sum = 0;
+	for (i = 0; i < mbp->msg_size; i++)
+		sum += (u_char)mbp->msg_ptr[i];
+	return (sum);
+}
+
+/*
+ * Copy from one message buffer to another.
+ */
+void
+msgbuf_copy(struct msgbuf *src, struct msgbuf *dst)
+{
+	int c;
+
+	while ((c = msgbuf_getchar(src)) >= 0)
+		msgbuf_addchar(dst, c);
+}