Another, hopefully final set of changes to boot0 and boot0cfg.

boot0.S changes:

+ import a patch from Christoph Mallon to rearrange the various
  print functions and save another couple of bytes;

+ implement the suggestion in PR 70531 to enable booting from
  any valid partition because even the extended partitions that
  were previously in our kill list may contain a valid boot loader.
  This simplifies the code and saves some bytes;

+ followwing up PR 127764, implement conditional code to preserve
  the 'Volume ID' which might be used by other OS (NT, XP, Vista)
  and is located at offset 0x1b8. This requires a relocation of the
  parameter block within the boot sector -- there is no other
  possible workaround.
  To address this, boot0cfg has been updated to handle both
  versions of the boot code;

+ slightly rearrange the strings printed in the menus to make
  the code buildable with all options. Given the tight memory
  budget, this means that with certain options we need to
  shrink or remove certain labels.

and especially:

	make -DVOLUME_LABEL -DPXE the default options.

  This means that the newly built boot0 block will preserve the
  Volume ID, and has the (hidden) option F6 to boot from INT18/PXE.
  I think the extra functionality is well worth the change.

  The most visible difference here is that the 'Default: ' string
  now becomes 'Boot: ' (it can be reverted to the old value
  but then we need to nuke 1/2 partition name or entries to
  make up for the extra room).

boot0cfg changes:

+ modify the code to recognise the new boot0 structure (with the
  relocated options block to make room for the Volume id).

+ add two options, '-i xxxx-xxxx' to set the volume ID, -e c
  to modify the character printed in case of bad input

PR:		127764 70531
Submitted by:	Christoph Mallon (portions)
MFC after:	4 weeks

2 files changed, 71 insertions, 61 deletions

diff --git a/sys/boot/i386/boot0/Makefile b/sys/boot/i386/boot0/Makefile
index 4eb8435..27f66d5 100644
--- a/sys/boot/i386/boot0/Makefile
+++ b/sys/boot/i386/boot0/Makefile
@@ -9,12 +9,14 @@ SRCS=	${PROG}.S
 # Additional options that you can specify with make OPTS="..."
 # (these only apply to boot0.S)
 #
+#	-DVOLUME_SERIAL	support volume serial number (NT, XP, Vista)
 #	-DSIO		do I/O using COM1:
 #	-DPXE		fallback to INT18/PXE with F6
 #	-DCHECK_DRIVE	enable checking drive number
 #	-DONLY_F_KEYS	accept only Fx keys in console
 #	-DTEST		print drive number on entry
 #
+OPTS ?= -DVOLUME_SERIAL -DPXE
 CFLAGS += ${OPTS}
 
 # Flags used in the boot0.S code:
diff --git a/sys/boot/i386/boot0/boot0.S b/sys/boot/i386/boot0/boot0.S
index 33e950b..caa89e8 100644
--- a/sys/boot/i386/boot0/boot0.S
+++ b/sys/boot/i386/boot0/boot0.S
@@ -30,10 +30,16 @@
 #ifdef ONLY_F_KEYS	/* Only F1..F6, no digits on console */
 #endif
 
-#ifdef TEST		/* enable some test code */
-#ifndef ONLY_F_KEYS
-#define ONLY_F_KEYS	/* make room for the test code */
+#ifdef VOLUME_SERIAL	/* support Volume serial number */
+#define B0_BASE	0x1ae	/* move the internal data area */
+#define SAVE_MEMORY
+#else
+#define B0_BASE	0x1b2
 #endif
+
+#ifdef TEST		/* enable some test code */
+#define SAVE_MEMORY
+#define SAVE_MORE_MEMORY
 #endif
 
 /*
@@ -118,7 +124,7 @@
  * 	to change the value passed to the linker in the Makefile
  * PRT_OFF is the location of the partition table (from the MBR standard).
  * B0_OFF is the location of the data area, known to boot0cfg so
- *	it cannot be changed.
+ *	it cannot be changed. Computed as a negative offset from 0x200
  * MAGIC is the signature of a boot block.
  */
 
@@ -127,7 +133,7 @@
 		.set LOAD,0x7c00		# Load address
 
 		.set PRT_OFF,0x1be		# Partition table
-		.set B0_OFF,0x1b2		# Offset of boot0 data
+		.set B0_OFF,(B0_BASE-0x200)	# Offset of boot0 data
 
 		.set MAGIC,0xaa55		# Magic: bootable
 
@@ -144,15 +150,16 @@
  * We need to define them as constant as the assembler cannot
  * compute them in its single pass.
  */
-		.set _NXTDRV,	-0x48		# Next drive
-		.set _OPT,	-0x47 		# Default option
-		.set _SETDRV,	-0x46		# Drive to force
-		.set _FLAGS,	-0x45		# Flags
+		.set _NXTDRV,	B0_OFF+6	# Next drive
+		.set _OPT,	B0_OFF+7	# Default option
+		.set _SETDRV,	B0_OFF+8	# Drive to force
+		.set _FLAGS,	B0_OFF+9	# Flags
 		.set SETDRV,	0x20		# the 'setdrv' flag
 		.set NOUPDATE,	0x40		# the 'noupdate' flag
 		.set USEPACKET,	0x80		# the 'packet' flag
-		.set _TICKS,	-0x44		# Timeout ticks
-		.set _FAKE,0x0			# Fake partition table
+
+	/* ticks is at a fixed position */
+		.set _TICKS,	(PRT_OFF - 0x200 - 2)	# Timeout ticks
 		.set _MNUOPT, 0x10		# Saved menu entries
 
 		.set TLEN, (desc_ofs - bootable_ids)	# size of bootable ids
@@ -260,26 +267,16 @@ save_curdrive:	movb %dl, (%bp)			# Save drive number
 read_entry:	movb %ch,-0x4(%bx)		# Zero active flag (ch == 0)
 		btw %dx,_FLAGS(%bp)		# Entry enabled?
 		jnc next_entry			# No
-	/*
-	 * Lookup type in the 'non_bootable_ids' table, skip matching entries.
-	 * This is implemented is by setting %di to the start of the
-	 * exclude table, and %cl to the length of the table itself. After the
-	 * 'repne scasb' the zero flag is set if we found a match.
-	 * If not, %di points to the beginning of the 'valid' types,
-	 * which is what we need for the next check.
-	 */
 		movb (%bx),%al			# Load type
-		movw $non_bootable_ids,%di	# Lookup tables
-		movb $(bootable_ids-non_bootable_ids),%cl	# length
-		repne				# Exclude
-		scasb				#  partition?
-		je next_entry			# Yes, ignore it
+		test %al, %al			# skip empty partition
+		jz next_entry
 	/*
-	 * Now scan the table of bootable ids, which starts at %di and has
+	 * Scan the table of bootable ids, which starts at %di and has
 	 * length TLEN. On a match, %di points to the element following the
 	 * match; the corresponding offset to the description is $(TLEN-1)
 	 * bytes ahead. If we don't find a match, we hit the 'unknown' entry.
 	 */
+		movw $bootable_ids,%di		# Lookup tables
 		movb $(TLEN),%cl		# Number of entries
 		repne				# Locate
 		scasb				#  type
@@ -500,19 +497,10 @@ check_selection:
  *		the string at %si
  * putx:	print the option in %dl followed by the string at %di
  *		also record the drive as valid.
- * puts:	print the string at %si followed by a crlf
  * putn:	print a crlf
  * putstr:	print the string at %si
  * putchr:	print the char in al
  */
-putkey:
-#ifndef SIO
-		movb $'F',%al			# Display
-		callw putchr			#  'F'
-#endif
-		movb $'1',%al			# Prepare
-		addb %dl,%al			#  digit
-		jmp putstr.1			# Display the rest
 
 /*
  * Display the option and record the drive as valid in the options.
@@ -523,17 +511,24 @@ putx:		btsw %dx,_MNUOPT(%bp)		# Enable menu option
 		movw $item,%si			# Display
 		callw putkey			#  key
 		movw %di,%si			# Display the rest
-
-puts:		callw putstr			# Display string
+		callw putstr			# Display string
 
 putn:		movw $crlf,%si			# To next line
+		jmp putstr
 
+putkey:
+#ifndef SIO
+		movb $'F',%al			# Display
+		callw putchr			#  'F'
+#endif
+		movb $'1',%al			# Prepare
+		addb %dl,%al			#  digit
+
+putstr.1:	callw putchr			# Display char
 putstr:		lodsb				# Get byte
 		testb $0x80,%al 		# End of string?
-		jnz putstr.2			# Yes
-putstr.1:	callw putchr			# Display char
-		jmp putstr			# Continue
-putstr.2:	andb $~0x80,%al 		# Clear MSB
+		jz putstr.1			# No
+		andb $~0x80,%al 		# Clear MSB then print last 
 
 putchr:
 #ifndef SIO
@@ -601,38 +596,45 @@ crlf:		.ascii "\r";	     .byte '\n'|0x80
 
 /* Partition type tables */
 
-non_bootable_ids:
-	/*
-	 * These entries identify invalid or NON BOOT types and partitions.
-	 * 0: empty, 5: DOS3 ext. partition, 0xf: WIN95 ext partition
-	 */
-		.byte 0x0, 0x5, 0xf
 bootable_ids:
 	/*
-	 * These values indicate bootable types we know the names of.
-	 * 1: FAT12, 4: FAT16 <32M, 6: FAT16 > 32M, 7: NTFS
-	 * 0xb: FAT32, 0xc: FAT32-LBA, 0xe: FAT16-LBA, 
-	 * 0x83: linux, 0xa5: FreeBSD, 0xa6: netbsd, 0xa9:openbsd
+	 * These values indicate bootable types we know about.
+	 * Corresponding descriptions are at desc_ofs:
+	 * Entries don't need to be sorted.
 	 */
-		.byte 0x1, 0x6, 0x7, 0xb, 0xc, 0xe, 0x83
-		.byte 0xa5, 0xa6, 0xa9, 0x4
+		.byte 0x1, 0x6, 0x7, 0xb, 0xc
+#ifndef SAVE_MEMORY
+		.byte 0xe
+#endif
+		.byte 0x83, 0xa5, 0xa6, 0xa9, 0x4
+#ifndef SAVE_MORE_MEMORY
+		.byte 0x5, 0xf
+#endif
+
 desc_ofs:
 	/*
 	 * Offsets that match the known types above, used to point to the
 	 * actual partition name. The last entry must point to os_misc,
 	 * which is used for non-matching names.
 	 */
-		.byte os_dos-.			# 1, DOS
-		.byte os_dos-.			# 6, DOS/WIN
-		.byte os_win-.			# 7, Windows
-		.byte os_win-.			# 11, Windows
-		.byte os_win-.			# 12, Windows
-		.byte os_win-.			# 14, Windows
+		.byte os_dos-.			#   1, FAT12 DOS
+		.byte os_dos-.			#   6, FAT16 <32M, DOS/WIN
+		.byte os_win-.			#   7, FAT16 >=32M Windows
+		.byte os_win-.			#  11, FAT32
+		.byte os_win-.			#  12, FAT32-LBA
+#ifndef SAVE_MEMORY
+		.byte os_win-.			#  14, FAT16-LBA
+#endif
 		.byte os_linux-.		# 131, Linux
 		.byte os_freebsd-.		# 165, FreeBSD
 		.byte os_bsd-.			# 166, OpenBSD
 		.byte os_bsd-.			# 169, NetBSD
-		.byte os_dos-.			# 4, DOS
+		.byte os_dos-.			#   4, FAT16 < 32M
+#ifndef SAVE_MORE_MEMORY
+		.byte os_ext-.			#   5, DOS Ext
+		.byte os_ext-.			#  15, DOS Ext-LBA
+#endif
+
 		.byte os_misc-. 		# Unknown
 
 	/*
@@ -641,15 +643,18 @@ desc_ofs:
 	 */
 os_misc:	.byte '?'|0x80
 os_dos:
-#if !defined(TEST)	/* DOS string only if room */
+#ifndef SAVE_MEMORY	/* DOS string only if room */
 		.ascii "DO";   .byte 'S'|0x80
 #endif
 os_win:		.ascii "WI";   .byte 'N'|0x80
 os_linux:	.ascii "Linu"; .byte 'x'|0x80
 os_freebsd:	.ascii "Free"
 os_bsd:		.ascii "BS";   .byte 'D'|0x80
+#ifndef SAVE_MORE_MEMORY
+os_ext:		.ascii "EX";   .byte 'T'|0x80
+#endif
 
-		.org B0_OFF,0x90
+		.org (0x200 + B0_OFF),0x90
 /*
  * The boot0 version 1.0 parameter table.
  * Do not move it nor change the "Drive " string, boot0cfg
@@ -663,6 +668,9 @@ nxtdrv:		.byte 0x0			# Next drive number
 opt:		.byte 0x0			# Option
 setdrv_num:	.byte 0x80			# Drive to force
 flags:		.byte FLAGS			# Flags
+#ifdef VOLUME_SERIAL
+		.byte 0xa8,0xa8,0xa8,0xa8       # Volume Serial Number
+#endif
 ticks:		.word TICKS			# Delay
 
 		.org PRT_OFF