From ee6fb785cd89b1680ed2a8dc804c7d335c641ea5 Mon Sep 17 00:00:00 2001
From: Robert Nordier <rnordier@FreeBSD.org>
Date: Fri, 26 Feb 1999 14:57:17 +0000
Subject: [PATCH] Finish implementing "setdrv" option.  This is intended to be
 used (with care) in those instances where boot0 is not passed the correct
 drive number by the PC BIOS.  (The symptoms are a "F5   Drive 0" line, even
 though the current drive is drive 0.)

---
 usr.sbin/boot0cfg/boot0cfg.8 | 10 +++++-----
 usr.sbin/boot0cfg/boot0cfg.c |  7 +++++--
 2 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/usr.sbin/boot0cfg/boot0cfg.8 b/usr.sbin/boot0cfg/boot0cfg.8
index e949cc76c249..bb73d753d058 100644
--- a/usr.sbin/boot0cfg/boot0cfg.8
+++ b/usr.sbin/boot0cfg/boot0cfg.8
@@ -22,7 +22,7 @@
 .\" OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 .\" EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\"	$Id: boot0cfg.8,v 1.1.1.1 1999/02/21 21:23:42 rnordier Exp $
+.\"	$Id: boot0cfg.8,v 1.2 1999/02/22 09:36:54 rnordier Exp $
 .\"
 .Dd February 21, 1999
 .Dt BOOT0CFG 8
@@ -101,7 +101,7 @@ the conventional (CHS) interface, when accessing disk-related BIOS
 services.  The default is
 .Sq nopacket .
 .It setdrv
-Causes the drive containing the disk to be referenced using drive
+Forces the drive containing the disk to be referenced using drive
 number definable by means of the -d option.  The default is
 .Sq nosetdrv .
 .It update
@@ -131,7 +131,7 @@ option may cause
 .Sq boot0
 to fail, depending on the nature of BIOS support.
 .Pp
-The
+Use of the
 .Sq setdrv
-option is presently implemented
-.Dq syntactically but not semantically .
+option with an incorrect -d operand may cause the MBR to be written
+to the wrong disk.  Be careful!
diff --git a/usr.sbin/boot0cfg/boot0cfg.c b/usr.sbin/boot0cfg/boot0cfg.c
index 67d0c882d216..20fdcc34e90c 100644
--- a/usr.sbin/boot0cfg/boot0cfg.c
+++ b/usr.sbin/boot0cfg/boot0cfg.c
@@ -26,7 +26,7 @@
 
 #ifndef lint
 static const char rcsid[] =
-	"$Id: boot0cfg.c,v 1.1.1.1 1999/02/21 21:23:42 rnordier Exp $";
+	"$Id: boot0cfg.c,v 1.2 1999/02/22 09:36:54 rnordier Exp $";
 #endif /* not lint */
 
 #include <sys/param.h>
@@ -44,6 +44,7 @@ static const char rcsid[] =
 
 #define MBRSIZE         512     /* master boot record size */
 
+#define OFF_DRIVE	0x1ba	/* offset: setdrv drive */
 #define OFF_FLAGS       0x1bb   /* offset: option flags */
 #define OFF_TICKS       0x1bc   /* offset: clock ticks */
 #define OFF_PTBL        0x1be   /* offset: partition table */
@@ -154,6 +155,8 @@ main(int argc, char *argv[])
             errx(1, "%s: bad magic", bpath);
         memcpy(buf + OFF_PTBL, part, sizeof(part));
     }
+    if (d_arg != -1)
+	buf[OFF_DRIVE] = d_arg;
     if (o_flag) {
         buf[OFF_FLAGS] &= o_and;
         buf[OFF_FLAGS] |= o_or;
@@ -185,7 +188,7 @@ main(int argc, char *argv[])
                        part[i].dp_size);
             }
         printf("\n");
-        printf("drive=0x0  options=");
+        printf("drive=0x%x  options=", buf[OFF_DRIVE]);
         for (i = 0; i < nopt; i++) {
             if (i)
                 printf(",");