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Go back to occupying just a single sector, reverting r1.17 - r1.20.

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Taking over the sector following the MBR causes problems on some
machines, and the actual gains are fairly small in terms of how
the space is presently used.

Since we need a number of further features (eg. handling extended
partitions) that can't be readily accommodated in the basic boot0
design anyway, rather choose to implement the additional stuff
separately and concentrate on compatibility rather than features
here.
This commit is contained in:
rnordier 2000-10-02 17:30:22 +00:00
parent 56de11b718
commit 7e9332da79
2 changed files with 81 additions and 165 deletions
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24
sys/boot/i386/boot0/Makefile
View File

@ -10,33 +10,23 @@ BINMODE= 444
M4?= m4
# The default set of flags compiled into boot0. This enables update (writing
# the modified boot0 back to disk after running so that the selection made is
# saved), packet mode (detect and use the BIOS EDD extensions if we try to
# boot past the 1024 cylinder liimt), and booting from all valid slices.
BOOT_BOOT0_FLAGS?= 0x8f
B0FLAGS=0xf
B0TICKS=0xb6
# The number of timer ticks to wait for a keypress before assuming the default
# selection. Since there are 18.2 ticks per second, the default value of
# 0xb6 (182d) corresponds to 10 seconds.
BOOT_BOOT0_TICKS?= 0xb6
# The base address that we the boot0 code to to run it. Don't change this
# unless you are glutton for punishment.
BOOT_BOOT0_ORG?= 0x600
ORG= 0x600
boot0: boot0.o
.if ${OBJFORMAT} == aout
${LD} -N -s -T ${BOOT_BOOT0_ORG} -o boot0.out boot0.o
${LD} -N -s -T ${ORG} -o boot0.out boot0.o
dd if=boot0.out of=${.TARGET} ibs=32 skip=1
.else
${LD} -N -e start -Ttext ${BOOT_BOOT0_ORG} -o boot0.out boot0.o
${LD} -N -e start -Ttext ${ORG} -o boot0.out boot0.o
objcopy -S -O binary boot0.out ${.TARGET}
.endif
boot0.o: boot0.s
${AS} ${AFLAGS} --defsym FLAGS=${BOOT_BOOT0_FLAGS} \
--defsym TICKS=${BOOT_BOOT0_TICKS} ${.IMPSRC} -o ${.TARGET}
${AS} ${AFLAGS} --defsym FLAGS=${B0FLAGS} --defsym TICKS=${B0TICKS} \
${.IMPSRC} -o ${.TARGET}
CLEANFILES+= boot0.out boot0.o

210
sys/boot/i386/boot0/boot0.s
View File

@ -15,20 +15,17 @@
# $FreeBSD$
# A 1024-byte boot manager.
# A 512-byte boot manager.
.set NHRDRV,0x475 # Number of hard drives
.set ORIGIN,0x600 # Execution address
.set SECTOR_SIZE,0x200 # Length of a sector
.set NUM_SECTORS,2 # Total length in sectors
.set FAKE,ORIGIN+(SECTOR_SIZE*NUM_SECTORS) # Partition entry
.set FAKE,0x800 # Partition entry
.set LOAD,0x7c00 # Load address
.set PRT_OFF,0x1be # Partition table
.set TBL0SZ,table0_end-table0 # Table 0 size
.set TBL1SZ,table1_end-table1 # Table 1 size
.set TBL0SZ,0x3 # Table 0 size
.set TBL1SZ,0xc # Table 1 size
.set MAGIC,0xaa55 # Magic: bootable
@ -36,21 +33,14 @@
.set KEY_F1,0x3b # F1 key scan code
#
# Flag bits
#
.set FL_PACKET,0x80 # Packet mode
.set FL_NOUPDATE,0x40 # Don't save selection
.set FL_SETDRV,0x20 # Override drive number
#
# Addresses in the sector of embedded data values.
# Accessed with negative offsets from the end of the relocated sectors (%bp).
# Accessed with negative offsets from the end of the relocated sector (%ebp).
#
.set _PRT_END,(FAKE-(ORIGIN+SECTOR_SIZE))
.set _NXTDRV,-(_PRT_END+0x48) # Next drive
.set _OPT,-(_PRT_END+0x47) # Default option
.set _SETDRV,-(_PRT_END+0x46) # Drive to force
.set _FLAGS,-(_PRT_END+0x45) # Flags
.set _TICKS,-(_PRT_END+0x44) # Timeout ticks
.set _NXTDRV,-0x48 # Next drive
.set _OPT,-0x47 # Default option
.set _SETDRV,-0x46 # Drive to force
.set _FLAGS,-0x45 # Flags
.set _TICKS,-0x44 # Timeout ticks
.set _FAKE,0x0 # Fake partition entry
.set _MNUOPT,0xc # Menu options
@ -62,48 +52,40 @@
# segments start at 0.
# The stack is immediately below the address we were loaded to.
#
# Note that this section of code is used as the first signature check in
# boot0cfg(8).
#
start: cld # String ops inc
xorw %ax,%ax # Zero
movw %ax,%es # Address
movw %ax,%ds # data
movw %ax,%ss # Set up
movw $LOAD,%sp # stack
#
# End signature code
# Copy this code to the address it was linked for
#
movw %sp,%si # Source
movw $start,%di # Destination
movw $0x100,%cx # Word count
rep # Relocate
movsw # code
#
# Set address for variable space beyond code, and clear it.
# Notice that this is also used to point to the values embedded in the block,
# by using negative offsets.
#
movw $fake,%bp # Address variables
movw %bp,%di # %di used in stosw
movw $0x8,%cx # Words to clear
movw %di,%bp # Address variables
movb $0x8,%cl # Words to clear
rep # Zero
stosw # them
incb -0xe(%di) # Sector number 1
#
# Reload all of boot0 (including the extra sectors) into memory at the
# relocation address.
#
push %dx # Save drive number
movw $start,%bx # Origin we were linked for
movw %bp,%si # Fake PTE
movw $0x200+NUM_SECTORS,%ax # Read in all
callw intx13 # of boot0
pop %dx # Restore
#
# Relocate to the new copy of the code.
#
jmp main+ORIGIN-LOAD # To relocated code
incb -0xe(%di) # Sector number
jmp main-LOAD+ORIGIN # To relocated code
#
# Check what flags were loaded with us; specifically, use a predefined Drive.
# Check what flags were loaded with us, specifically, Use a predefined Drive.
# If what the bios gives us is bad, use the '0' in the block instead, as well.
#
main: testb $FL_SETDRV,_FLAGS(%bp) # Set number drive?
main: testb $0x20,_FLAGS(%bp) # Set number drive?
jnz main.1 # Yes
testb %dl,%dl # Drive number valid?
js main.2 # Possibly (0x80 set)
@ -151,7 +133,7 @@ main.3: movb %ch,-0x4(%bx) # Zero active flag (ch == 0)
jne main.4 # No
#
# If it matches get the matching element in the
# next array. If it doesn't, we are already
# next array. if it doesn't, we are already
# pointing at its first element which points to a "?".
#
addw $TBL1SZ,%di # Adjust
@ -192,7 +174,7 @@ main.6: addb $'0'|0x80,%al # Save next
callw putx # item
#
# Now that we've printed the drive (if we needed to), display a prompt.
# Get ready for the input by noting the time.
# Get ready for the input byt noting the time.
#
main.7: movw $prompt,%si # Display
callw putstr # prompt
@ -260,7 +242,7 @@ main.12: cbtw # Option
# for rewriting to the disk.
#
movb %al,_OPT(%bp) # Save option
movw $fake,%si # Partition for write
movw $FAKE,%si # Partition for write
movb (%si),%dl # Drive number
movw %si,%bx # Partition for read
cmpb $0x4,%al # F5 pressed?
@ -274,10 +256,10 @@ main.12: cbtw # Option
# If not asked to do a write-back (flags 0x40) don't do one.
#
main.13: pushw %bx # Save
testb $FL_NOUPDATE,_FLAGS(%bp) # Skip update?
testb $0x40,_FLAGS(%bp) # No updates?
jnz main.14 # Yes
movw $start,%bx # Data to write
movw $0x301,%ax # Write 1 sector
movb $0x3,%ah # Write sector
callw intx13 # to disk
main.14: popw %si # Restore
popf # Restore
@ -292,16 +274,19 @@ main.14: popw %si # Restore
# load selected bootsector to the LOAD location in RAM.
# If it fails to read or isn't marked bootable, treat it
# as a bad selection.
# XXX what does %si carry?
#
main.15: movw $LOAD,%bx # Address for read
movw $0x201,%ax # Read 1 sector
movb $0x2,%ah # Read sector
callw intx13 # from disk
jc main.10 # If error
cmpw $MAGIC,0x1fe(%bx) # Bootable?
jne main.10 # No
callw putn # Leave some space
pushw %si # Save
movw $crlf,%si # Leave some
callw puts # space
popw %si # Restore
jmp *%bx # Invoke bootstrap
#
# Display routines
#
@ -340,91 +325,28 @@ putchr: pushw %bx # Save
retw # To caller
# One-sector disk I/O routine
#
# Calling conventions: (assumes %si -> partition table entry)
#
# 0x1(%si) - byte - head
# 0x2(%si) - word - cylinder/sector
# 0x8(%si) - long - LBA to use if needed
# %ah - byte - operation, 2 = read, 3 = write
# %al - byte - sector count
# %dl - byte - drive number
# %es:(%bx) - void - buffer to use for transfer
#
# If the head == 0xff, and cylinder/sector == 0xffff, then try
# to use the EDD stuff with the LBA offset instead of CHS. However,
# use CHS if at all possible.
intx13: movb 0x1(%si),%dh # Load head
movw 0x2(%si),%cx # Load cylinder:sector
movb $0x1,%al # Sector count
pushw %si # Save
movw %sp,%di # Save
cmpb $0xff,%dh # Might we need LBA?
jne intx13.2 # No, just use CHS
cmpw $0xffff,%cx # Do we need LBA?
jne intx13.2 # No
testb $FL_PACKET,_FLAGS(%bp) # Try the packet interface?
jz intx13.2 # No
pushw %cx # Save
pushw %bx # Save
movw $0x55aa,%bx # Magic
pushw %ax # Save
movb $0x41,%ah # BIOS: EDD extensions
int $0x13 # present?
popw %ax # Restore
jc intx13.1 # Not present, use CHS
cmpw $0xaa55,%bx # Magic?
jne intx13.1 # Not present, use CHS
testb $0x1,%cl # Packet mode available?
jz intx13.1 # No, use CHS
orb $0x40,%ah # Use disk packet
intx13.1: popw %bx # Restore
popw %cx # Restore
testb $0x40,%ah # Using packet mode?
jz intx13.2 # No, so skip the rest
testb $0x80,_FLAGS(%bp) # Use packet interface?
jz intx13.1 # No
pushl $0x0 # Set the
pushl 0x8(%si) # LBA address
pushw %es # Set the transfer
pushw %bx # buffer address
push $0x0 # Punch a hole in the stack
push $0x1 # Block count
push $0x10 # Packet size
movw %sp,%si # Packet pointer
xchgb %al,0x2(%si) # Set the block count in the
# packet and zero %al,
# turning verify off for writes
intx13.2: int $0x13 # BIOS: Disk I/O
decw %ax # Verify off
orb $0x40,%ah # Use disk packet
intx13.1: int $0x13 # BIOS: Disk I/O
movw %di,%sp # Restore
popw %si # Restore
retw # To caller
.org PRT_OFF-0xe,0x90
#
# These values are sometimes changed before writing back to the drive
# Be especially careful that nxtdrv: must come after drive:, as it
# is part of the same string.
#
# Note that the 'drive' string variable is used as the second signature
# check in boot0cfg(8).
#
version_minor: .byte 0x1 # minor version
version_major: .byte 0x1 # major version
drive: .ascii "Drive "
nxtdrv: .byte 0x0 # Next drive number
opt: .byte 0x0 # Option
setdrv: .byte 0x80 # Drive to force
flags: .byte FLAGS # Flags
ticks: .word TICKS # Delay
#
# here is the 64 byte partition table that fdisk would fiddle with.
#
partbl: .fill 0x40,0x1,0x0 # Partition table
.word MAGIC # Magic number
#
# start of sector two.. ugh
#
.org SECTOR_SIZE,0x90
# Menu strings
item: .ascii " "; .byte ' '|0x80
@ -437,14 +359,12 @@ tables:
#
# These entries identify invalid or NON BOOT types and partitions.
#
table0: .byte 0x0, 0x5, 0xf
table0_end:
.byte 0x0, 0x5, 0xf
#
# These values indicate bootable types we know the names of
#
table1: .byte 0x1, 0x4, 0x6, 0x7, 0xb, 0xc, 0xe, 0x63, 0x83
.byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83
.byte 0x9f, 0xa5, 0xa6, 0xa9
table1_end:
#
# These are offsets that match the known names above and point to the strings
# that will be printed.
@ -453,35 +373,41 @@ table1_end:
.byte os_dos-. # DOS
.byte os_dos-. # DOS
.byte os_dos-. # DOS
.byte os_nt-. # NT or OS/2
.byte os_windows-. # Windows
.byte os_windows-. # Windows
.byte os_windows-. # Windows
.byte os_dos-. # Windows
.byte os_dos-. # Windows
.byte os_dos-. # Windows
.byte os_unix-. # UNIX
.byte os_linux-. # Linux
.byte os_bsdos-. # BSD/OS
.byte os_bsd-. # BSD/OS
.byte os_freebsd-. # FreeBSD
.byte os_openbsd-. # OpenBSD
.byte os_netbsd-. # NetBSD
.byte os_bsd-. # OpenBSD
.byte os_bsd-. # NetBSD
#
# And here are the strings themselves. 0x80 or'd into a byte indicates
# the end of the string. (not so great for Russians but...)
#
os_misc: .ascii "Unknow"; .byte 'n'|0x80
os_misc: .ascii "?"; .byte '?'|0x80
os_dos: .ascii "DO"; .byte 'S'|0x80
os_nt: .ascii "Windows N"; .byte 'T'|0x80
os_windows: .ascii "Window"; .byte 's'|0x80
os_unix: .ascii "UNI"; .byte 'X'|0x80
os_linux: .ascii "Linu"; .byte 'x'|0x80
os_freebsd: .ascii "FreeBS"; .byte 'D'|0x80
os_openbsd: .ascii "OpenBS"; .byte 'D'|0x80
os_netbsd: .ascii "NetBS"; .byte 'D'|0x80
os_bsdos: .ascii "BSD/O"; .byte 'S'|0x80
os_freebsd: .ascii "Free"
os_bsd: .ascii "BS"; .byte 'D'|0x80
.org PRT_OFF-0xc,0x90
#
# These values are sometimes changed before writing back to the drive
# Be especially careful that nxtdrv: must come after drive:, as it
# is part of the same string.
#
drive: .ascii "Drive "
nxtdrv: .byte 0x0 # Next drive number
opt: .byte 0x0 # Option
setdrv: .byte 0x80 # Drive to force
flags: .byte FLAGS # Flags
ticks: .word TICKS # Delay
#
# Fake partition entry created at the end of the table used when loading
# boot0 at the very beginning and when loading an MBR from another disk when
# F5 is pressed.
# here is the 64 byte partition table that fdisk would fiddle with.
#
.org SECTOR_SIZE*NUM_SECTORS, 0x0
fake:
partbl: .fill 0x40,0x1,0x0 # Partition table
.word MAGIC # Magic number