the boot loader passes a variable that identifies the disk its

booting off made up of a bunch of fields like adapter, controller,
disk, and partition offsets, plus a table of all the disks it can
see which includes this id and a checksum.

the kernel goes through and checksums the disks and then maps that
back to the id associated with that disk, and then compares some
of the fields in those ids against the boot disks id to figure out
which disk its on.

the problem is we overflow one of those fields (the disk id one).
since the other fields are set to 0 by the boot loader, this doesnt
really matter that much. however, since those fields are now
significant because of the overflow, we should compare them too.

this prevents sd16 being matched as the boot disk after sd0 on my
system with 25 disks attached.

ok krw@ weingart@

1 files changed, 11 insertions, 6 deletions

diff --git a/sys/arch/amd64/amd64/dkcsum.c b/sys/arch/amd64/amd64/dkcsum.c
index 41f7fdb9ded..0475b483abb 100644
--- a/sys/arch/amd64/amd64/dkcsum.c
+++ b/sys/arch/amd64/amd64/dkcsum.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: dkcsum.c,v 1.15 2008/12/10 23:41:19 krw Exp $	*/
+/*	$OpenBSD: dkcsum.c,v 1.16 2010/12/07 00:30:40 dlg Exp $	*/
 
 /*-
  * Copyright (c) 1997 Niklas Hallqvist.  All rights reserved.
@@ -71,10 +71,13 @@ dkcsumattach(void)
 
 #ifdef DEBUG
 	printf("dkcsum: bootdev=%#x\n", bootdev);
-	for (bdi = bios_diskinfo; bdi->bios_number != -1; bdi++)
-		if (bdi->bios_number & 0x80)
-			printf("dkcsum: BIOS drive %#x checksum is %#x\n",
-			    bdi->bios_number, bdi->checksum);
+	for (bdi = bios_diskinfo; bdi->bios_number != -1; bdi++) {
+		if (bdi->bios_number & 0x80) {
+			printf("dkcsum: BIOS drive %#x bsd_dev=%#x "
+			    "checksum=%#x\n", bdi->bios_number, bdi->bsd_dev,
+			    bdi->checksum);
+		}
+	}
 #endif
 	pribootdev = altbootdev = 0;
 
@@ -180,7 +183,9 @@ dkcsumattach(void)
 		 */
 
 		/* B_TYPE dependent hd unit counting bootblocks */
-		if ((B_TYPE(bootdev) == B_TYPE(hit->bsd_dev)) &&
+		if ((B_ADAPTOR(bootdev) == B_ADAPTOR(hit->bsd_dev)) &&
+		    (B_CONTROLLER(bootdev) == B_CONTROLLER(hit->bsd_dev)) &&
+		    (B_TYPE(bootdev) == B_TYPE(hit->bsd_dev)) &&
 		    (B_UNIT(bootdev) == B_UNIT(hit->bsd_dev))) {
 			int type, ctrl, adap, part, unit;