svn commit: r237294 - user/ae/bootcode/sys/boot/i386/pmbr

[Andrey V. Elsukov]

Author: ae
Date: Wed Jun 20 08:29:24 2012
New Revision: 237294
URL: http://svn.freebsd.org/changeset/base/237294

Log:
  In case when we have damaged several first sectors, GEOM_PART_GPT class
  will not detect GPT even if backup GPT header is ok. To recover we should
  write PMBR to the LBA 0. But we can't use `gpart bootcode` command until
  GPT is detected and geom created. We can dd(8) /boot/pmbr image and
  kernel will be able detect GPT. But our PMBR image contains only empty
  partition entries and our loader can't detect GPT when it hasn't the
  partition record with type PMBR.
  
  Add one partition record to the PMBR image. It covers all space after
  the LBA 0. It is better to have one partially correct record, than
  have nothing.

Modified:
  user/ae/bootcode/sys/boot/i386/pmbr/pmbr.s

Modified: user/ae/bootcode/sys/boot/i386/pmbr/pmbr.s
==============================================================================
--- user/ae/bootcode/sys/boot/i386/pmbr/pmbr.s	Wed Jun 20 08:02:44 2012	(r237293)
+++ user/ae/bootcode/sys/boot/i386/pmbr/pmbr.s	Wed Jun 20 08:29:24 2012	(r237294)
@@ -255,6 +255,16 @@ boot_uuid:	.long 0x83bd6b9d
 		.org DISKSIG,0x90
 sig:		.long 0				# OS Disk Signature
 		.word 0				# "Unknown" in PMBR
-
-partbl: 	.fill 0x10,0x4,0x0		# Partition table
+						# Partition table
+partbl: 	.byte 0x80			# bootable flag
+		.byte 0x00			# CHS address 
+		.byte 0x02			#  of first 
+		.byte 0x00			#   sector
+		.byte 0xee			# Partition type PMBR
+		.byte 0xff			# CHS address
+		.byte 0xff			#  of last
+		.byte 0xff			#   sector
+		.long 1				# LBA of first sector
+		.long 0xffffffff		# LBA of last sector
+		.fill 0x10,0x3,0x0		# Remaining partition records
 		.word MAGIC			# Magic number