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# Copyright (c) KATO Takenori, 1999, 2000.
#
# All rights reserved. Unpublished rights reserved under the copyright
# laws of Japan.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer as
# the first lines of this file unmodified.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#
# $FreeBSD$
#
.code16
.text
.global boot
#
# Read bootstrap program and jump to it.
#
boot:
# Step 1: Save parameters
movw curdevice, %si
movb daua(%si), %al
movb %al, b_daua
shlw %si
movw secsize(%si), %ax
movw %ax, b_secsize
movw curpartition, %si
movb partnum(%si), %al # %al = real partition number
xorb %ah, %ah
movw %ax, b_partn # save real parttion number
movb $5, %cl
shlw %cl, %si # %si = offset to parttable
addw $4, %si
movb parttable(%si), %al # IPLS
movb %al, b_sector
incw %si
movb parttable(%si), %al # IPLH
movb %al, b_head
incw %si # IPLC
movw parttable(%si), %ax
movw %ax, b_cylinder
# Step 2: Calculate the segment address of the bootstrap routine
movw $0x1d00, %ax
movw b_secsize, %cx
shrw %cx
shrw %cx
subw %cx, %ax
subw $0x100, %ax
movw %ax, b_bootseg
# Step 3: Read bootstrap code
movb $6, %ah
movb b_daua, %al
movw b_secsize, %bx
shlw %bx # 2 sectors
movw b_cylinder, %cx
movb b_head, %dh
movb b_sector, %dl
movw b_bootseg, %es
xorw %bp, %bp
int $0x1b
jc boot_error
# Step 4: Set DA/UA into BIOS work area
xorw %ax, %ax
movw %ax, %es
movw $0x584, %bx # DISK_BOOT
movb b_daua, %dl
call write_biosparam
call sc_clean
# Step 5: Set registers
# %ah: 00
# %al: DA/UA
# %bx: Sector size * 2
# %cx: cylinder number of boot partition
# %si: pointer to partition table
movw b_partn, %ax
movb $5, %cl
shl %cl, %ax # %ax = partition number * 32
addw b_secsize, %ax
movw %ax, %si # %si = pointer to partition table
movw b_cylinder, %cx # %cx = cylinder
movb b_head, %dh # %dh = head
movb b_sector, %dl # %dl = sector
movw b_bootseg, %es # %es = boot segment
movb b_daua, %al # %al = DA/UA
movw b_secsize, %bx
shlw %bx # %bx = sector size * 2
cli
movw %cs:iniss, %ss # Restore stack pointer
movw %cs:inisp, %sp
push %es # Boot segment
xorw %bp, %bp
push %bp # 0
movw %ax, %di # Save %ax
xorw %ax, %ax
movw %ax, %ds # %ds = 0
movw %di, %ax # Restore %ax
xorb %ah, %ah # %ah = 0
xorw %di, %di # %di = 0
sti
# Jump to bootstrap code
lret
# NOTREACHED
boot_error:
ret
#
# Try to boot from default partition.
#
.global trydefault
trydefault:
movw ndevice, %cx
xorw %si, %si
trydefault_loop:
movw %si, curdevice
push %cx
push %si
call read_ipl
pop %si
pop %cx
cmpb $0x80, defpartflag
jne nodefpart
# Default partition is defined.
push %cx
movw npartition, %cx
srch_part:
movw %cx, %bx
decw %bx
movb defpartnum, %al # %al = real partition number
cmpb partnum(%bx), %al
jne not_match
movw %bx, curpartition # Store partition number
call boot
not_match:
loop srch_part
pop %cx
nodefpart:
incw %si
loop trydefault_loop
ret
.data
b_daua: .byte 0 # DA/UA
b_head: .byte 0 # SYSH
b_sector: .byte 0 # SYSS
b_cylinder: .word 0 # SYSC
b_bootseg: .word 0
b_secsize: .word 0
b_partn: .word 0 # Real partition number
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