1 files changed, 42 insertions, 19 deletions

diff --git a/sys/kern/subr_log.c b/sys/kern/subr_log.c
index 5d247ead19f..00eb5a93bc9 100644
--- a/sys/kern/subr_log.c
+++ b/sys/kern/subr_log.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: subr_log.c,v 1.5 1997/09/18 13:23:26 deraadt Exp $	*/
+/*	$OpenBSD: subr_log.c,v 1.6 2000/02/22 19:28:03 deraadt Exp $	*/
 /*	$NetBSD: subr_log.c,v 1.11 1996/03/30 22:24:44 christos Exp $	*/
 
 /*
@@ -65,6 +65,44 @@ struct logsoftc {
 } logsoftc;
 
 int	log_open;			/* also used in log() */
+int	msgbufmapped;			/* is the message buffer mapped */
+int	msgbufenabled;			/* is logging to the buffer enabled */
+struct	msgbuf *msgbufp;		/* the mapped buffer, itself. */
+
+#define offsetof(type, member) ((size_t)(&((type *)0)->member))
+
+void
+initmsgbuf(buf, bufsize)
+	caddr_t buf;
+	size_t bufsize;
+{
+	register struct msgbuf *mbp;
+	long new_bufs;
+
+	/* Sanity-check the given size. */
+	if (bufsize < sizeof(struct msgbuf))
+		return;
+
+	mbp = msgbufp = (struct msgbuf *)buf;
+
+	new_bufs = bufsize - offsetof(struct msgbuf, msg_bufc);
+	if ((mbp->msg_magic != MSG_MAGIC) || (mbp->msg_bufs != new_bufs) ||
+	    (mbp->msg_bufr < 0) || (mbp->msg_bufr >= mbp->msg_bufs) ||
+	    (mbp->msg_bufx < 0) || (mbp->msg_bufx >= mbp->msg_bufs)) {
+		/*
+		 * If the buffer magic number is wrong, has changed
+		 * size (which shouldn't happen often), or is
+		 * internally inconsistent, initialize it.
+		 */
+
+		bzero(buf, bufsize);
+		mbp->msg_magic = MSG_MAGIC;
+		mbp->msg_bufs = new_bufs;
+	}
+
+	/* mark it as ready for use. */
+	msgbufmapped = msgbufenabled = 1;
+}
 
 /*ARGSUSED*/
 int
@@ -73,24 +111,9 @@ logopen(dev, flags, mode, p)
 	int flags, mode;
 	struct proc *p;
 {
-	register struct msgbuf *mbp = msgbufp;
-
 	if (log_open)
 		return (EBUSY);
 	log_open = 1;
-	/*
-	 * Potential race here with putchar() but since putchar should be
-	 * called by autoconf, msg_magic should be initialized by the time
-	 * we get here.
-	 */
-	if (mbp->msg_magic != MSG_MAGIC) {
-		register int i;
-
-		mbp->msg_magic = MSG_MAGIC;
-		mbp->msg_bufx = mbp->msg_bufr = 0;
-		for (i=0; i < MSG_BSIZE; i++)
-			mbp->msg_bufc[i] = 0;
-	}
 	return (0);
 }
 
@@ -139,7 +162,7 @@ logread(dev, uio, flag)
 	while (uio->uio_resid > 0) {
 		l = mbp->msg_bufx - mbp->msg_bufr;
 		if (l < 0)
-			l = MSG_BSIZE - mbp->msg_bufr;
+			l = mbp->msg_bufs - mbp->msg_bufr;
 		l = min(l, uio->uio_resid);
 		if (l == 0)
 			break;
@@ -148,7 +171,7 @@ logread(dev, uio, flag)
 		if (error)
 			break;
 		mbp->msg_bufr += l;
-		if (mbp->msg_bufr < 0 || mbp->msg_bufr >= MSG_BSIZE)
+		if (mbp->msg_bufr < 0 || mbp->msg_bufr >= mbp->msg_bufs)
 			mbp->msg_bufr = 0;
 	}
 	return (error);
@@ -212,7 +235,7 @@ logioctl(dev, com, data, flag, p)
 		l = msgbufp->msg_bufx - msgbufp->msg_bufr;
 		splx(s);
 		if (l < 0)
-			l += MSG_BSIZE;
+			l += msgbufp->msg_bufs;
 		*(int *)data = l;
 		break;