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freebsd-dev/sys/boot/pc98/cdboot/cdboot.s
Yoshihiro Takahashi 33cf0c5194 Add a bootable CD support.
2006-05-14 07:26:02 +00:00

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#
# Copyright (c) 2006 TAKAHASHI Yoshihiro <nyan@FreeBSD.org>
# Copyright (c) 2001 John Baldwin <jhb@FreeBSD.org>
# All rights reserved.
#
# 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.
# 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.
# 3. Neither the name of the author nor the names of any co-contributors
# may be used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
#
# $FreeBSD$
#
# Basically, we first create a set of boot arguments to pass to the loaded
# binary. Then we attempt to load /boot/loader from the CD we were booted
# off of.
#
#
# Memory locations.
#
.set STACK_OFF,0x6000 # Stack offset
.set LOAD_SEG,0x0700 # Load segment
.set LOAD_SIZE,2048 # Load size
.set DAUA,0x0584 # DA/UA
.set MEM_PAGE_SIZE,0x1000 # memory page size, 4k
.set MEM_ARG,0x900 # Arguments at start
.set MEM_ARG_BTX,0xa100 # Where we move them to so the
# BTX client can see them
.set MEM_ARG_SIZE,0x18 # Size of the arguments
.set MEM_BTX_ADDRESS,0x9000 # where BTX lives
.set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute
.set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader
.set MEM_BTX_CLIENT,0xa000 # where BTX clients live
#
# PC98 machine type from sys/pc98/pc98/pc98_machdep.h
#
.set MEM_SYS, 0xa100 # System common area segment
.set PC98_MACHINE_TYPE, 0x0620 # PC98 machine type
.set EPSON_ID, 0x0624 # EPSON machine id
.set M_NEC_PC98, 0x0001
.set M_EPSON_PC98, 0x0002
.set M_NOT_H98, 0x0010
.set M_H98, 0x0020
.set M_NOTE, 0x0040
.set M_NORMAL, 0x1000
.set M_8M, 0x8000
#
# Signature Constants
#
.set SIG1_OFF,0x1fe # Signature offset
.set SIG2_OFF,0x7fe # Signature offset
#
# a.out header fields
#
.set AOUT_TEXT,0x04 # text segment size
.set AOUT_DATA,0x08 # data segment size
.set AOUT_BSS,0x0c # zero'd BSS size
.set AOUT_SYMBOLS,0x10 # symbol table
.set AOUT_ENTRY,0x14 # entry point
.set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header
#
# Flags for kargs->bootflags
#
.set KARGS_FLAGS_CD,0x1 # flag to indicate booting from
# CD loader
#
# Segment selectors.
#
.set SEL_SDATA,0x8 # Supervisor data
.set SEL_RDATA,0x10 # Real mode data
.set SEL_SCODE,0x18 # PM-32 code
.set SEL_SCODE16,0x20 # PM-16 code
#
# BTX constants
#
.set INT_SYS,0x30 # BTX syscall interrupt
#
# Constants for reading from the CD.
#
.set ERROR_TIMEOUT,0x90 # BIOS timeout on read
.set NUM_RETRIES,3 # Num times to retry
.set SECTOR_SIZE,0x800 # size of a sector
.set SECTOR_SHIFT,11 # number of place to shift
.set BUFFER_LEN,0x100 # number of sectors in buffer
.set MAX_READ,0xf800 # max we can read at a time
.set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT
.set MEM_READ_BUFFER,0x9000 # buffer to read from CD
.set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor
.set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer
.set VOLDESC_LBA,0x10 # LBA of vol descriptor
.set VD_PRIMARY,1 # Primary VD
.set VD_END,255 # VD Terminator
.set VD_ROOTDIR,156 # Offset of Root Dir Record
.set DIR_LEN,0 # Offset of Dir Record length
.set DIR_EA_LEN,1 # Offset of EA length
.set DIR_EXTENT,2 # Offset of 64-bit LBA
.set DIR_SIZE,10 # Offset of 64-bit length
.set DIR_NAMELEN,32 # Offset of 8-bit name len
.set DIR_NAME,33 # Offset of dir name
#
# Program start.
#
.code16
.globl start
start: jmp main
.org 4
.ascii "IPL1 "
main: cld
/* Setup the stack */
xor %ax,%ax
mov %ax,%ss
mov $STACK_OFF,%sp
push %ecx
/* Setup graphic screen */
mov $0x42,%ah # 640x400
mov $0xc0,%ch
int $0x18
mov $0x40,%ah # graph on
int $0x18
/* Setup text screen */
mov $0x0a00,%ax # 80x25
int $0x18
mov $0x0c,%ah # text on
int $0x18
mov $0x13,%ah # cursor home
xor %dx,%dx
int $0x18
mov $0x11,%ah # cursor on
int $0x18
/* Setup keyboard */
mov $0x03,%ah
int $0x18
/* Transfer PC-9801 system common area */
xor %ax,%ax
mov %ax,%si
mov %ax,%ds
mov %ax,%di
mov $MEM_SYS,%ax
mov %ax,%es
mov $0x0600,%cx
rep
movsb
/* Transfer EPSON machine type */
mov $0xfd00,%ax
mov %ax,%ds
mov (0x804),%eax
and $0x00ffffff,%eax
mov %eax,%es:(EPSON_ID)
/* Set machine type to PC98_SYSTEM_PARAMETER */
call machine_check
/* Load cdboot */
xor %ax,%ax
mov %ax,%ds
mov $0x06,%ah /* Read data */
mov (DAUA),%al /* Read drive */
pop %ecx /* cylinder */
xor %dx,%dx /* head / sector */
mov $LOAD_SEG,%bx /* Load address */
mov %bx,%es
xor %bp,%bp
mov $LOAD_SIZE,%bx /* Load size */
int $0x1b
mov $msg_readerr,%si
jc error
/* Jump to cdboot */
ljmp $LOAD_SEG,$cdboot
#
# Set machine type to PC98_SYSTEM_PARAMETER.
#
machine_check: xor %edx,%edx
mov %dx,%ds
mov $MEM_SYS,%ax
mov %ax,%es
/* Wait V-SYNC */
vsync.1: inb $0x60,%al
test $0x20,%al
jnz vsync.1
vsync.2: inb $0x60,%al
test $0x20,%al
jz vsync.2
/* ANK 'A' font */
xor %al,%al
outb %al,$0xa1
mov $0x41,%al
outb %al,$0xa3
/* Get 'A' font from CG window */
push %ds
mov $0xa400,%ax
mov %ax,%ds
xor %eax,%eax
xor %bx,%bx
mov $4,%cx
font.1: add (%bx),%eax
add $4,%bx
loop font.1
pop %ds
cmp $0x6efc58fc,%eax
jnz m_epson
m_pc98: or $M_NEC_PC98,%edx
mov $0x0458,%bx
mov (%bx),%al
test $0x80,%al
jz m_not_h98
or $M_H98,%edx
jmp 1f
m_epson: or $M_EPSON_PC98,%edx
m_not_h98: or $M_NOT_H98,%edx
1: inb $0x42,%al
test $0x20,%al
jz 1f
or $M_8M,%edx
1: mov $0x0400,%bx
mov (%bx),%al
test $0x80,%al
jz 1f
or $M_NOTE,%edx
1: mov $PC98_MACHINE_TYPE,%bx
mov %edx,%es:(%bx)
ret
#
# Print out the error message at [SI], wait for a keypress, and then
# reboot the machine.
#
error: call putstr
mov $msg_keypress,%si
call putstr
xor %ax,%ax # Get keypress
int $0x18
xor %ax,%ax # CPU reset
outb %al,$0xf0
halt: hlt
jmp halt # Spin
#
# Display a null-terminated string at [SI].
#
# Trashes: AX, BX, CX, DX, SI, DI
#
putstr: push %ds
push %es
mov %cs,%ax
mov %ax,%ds
mov $0xa000,%ax
mov %ax,%es
mov cursor,%di
mov $0x00e1,%bx # Attribute
mov $160,%cx
putstr.0: lodsb
testb %al,%al
jz putstr.done
cmp $0x0d,%al
jz putstr.cr
cmp $0x0a,%al
jz putstr.lf
mov %bl,%es:0x2000(%di)
stosb
inc %di
jmp putstr.move
putstr.cr: xor %dx,%dx
mov %di,%ax
div %cx
sub %dx,%di
jmp putstr.move
putstr.lf: add %cx,%di
putstr.move: mov %di,%dx
mov $0x13,%ah # Move cursor
int $0x18
jmp putstr.0
putstr.done: mov %di,cursor
pop %es
pop %ds
ret
#
# Display a single char at [AL], but don't move a cursor.
#
putc: push %es
push %di
push %bx
mov $0xa000,%bx
mov %bx,%es
mov cursor,%di
mov $0xe1,%bl # Attribute
mov %bl,%es:0x2000(%di)
stosb
pop %bx
pop %di
pop %es
ret
msg_readerr: .asciz "Read Error\r\n"
msg_keypress: .asciz "\r\nPress any key to reboot\r\n"
/* Boot signature */
.org SIG1_OFF,0x90
.word 0xaa55 # Magic number
#
# cdboot
#
cdboot: mov %cs,%ax
mov %ax,%ds
xor %ax,%ax
mov %ax,%es
mov %es:(DAUA),%al # Save BIOS boot device
mov %al,drive
mov %cx,cylinder # Save BIOS boot cylinder
mov $msg_welcome,%si # %ds:(%si) -> welcome message
call putstr # display the welcome message
#
# Setup the arguments that the loader is expecting from boot[12]
#
mov $msg_bootinfo,%si # %ds:(%si) -> boot args message
call putstr # display the message
mov $MEM_ARG,%bx # %ds:(%bx) -> boot args
mov %bx,%di # %es:(%di) -> boot args
xor %eax,%eax # zero %eax
mov $(MEM_ARG_SIZE/4),%cx # Size of arguments in 32-bit
# dwords
rep # Clear the arguments
stosl # to zero
mov drive,%dl # Store BIOS boot device
mov %dl,%es:0x4(%bx) # in kargs->bootdev
or $KARGS_FLAGS_CD,%es:0x8(%bx) # kargs->bootflags |=
# KARGS_FLAGS_CD
#
# Load Volume Descriptor
#
mov $VOLDESC_LBA,%eax # Set LBA of first VD
load_vd: push %eax # Save %eax
mov $1,%dh # One sector
mov $MEM_VOLDESC,%ebx # Destination
call read # Read it in
cmpb $VD_PRIMARY,%es:(%bx) # Primary VD?
je have_vd # Yes
pop %eax # Prepare to
inc %eax # try next
cmpb $VD_END,%es:(%bx) # Last VD?
jne load_vd # No, read next
mov $msg_novd,%si # No VD
jmp error # Halt
have_vd: # Have Primary VD
#
# Try to look up the loader binary using the paths in the loader_paths
# array.
#
mov $loader_paths,%si # Point to start of array
lookup_path: push %si # Save file name pointer
call lookup # Try to find file
pop %di # Restore file name pointer
jnc lookup_found # Found this file
push %es
mov %cs,%ax
mov %ax,%es
xor %al,%al # Look for next
mov $0xffff,%cx # path name by
repnz # scanning for
scasb # nul char
pop %es
mov %di,%si # Point %si at next path
mov (%si),%al # Get first char of next path
or %al,%al # Is it double nul?
jnz lookup_path # No, try it.
mov $msg_failed,%si # Failed message
jmp error # Halt
lookup_found: # Found a loader file
#
# Load the binary into the buffer. Due to real mode addressing limitations
# we have to read it in in 64k chunks.
#
mov %es:DIR_SIZE(%bx),%eax # Read file length
add $SECTOR_SIZE-1,%eax # Convert length to sectors
shr $SECTOR_SHIFT,%eax
cmp $BUFFER_LEN,%eax
jbe load_sizeok
mov $msg_load2big,%si # Error message
jmp error
load_sizeok: movzbw %al,%cx # Num sectors to read
mov %es:DIR_EXTENT(%bx),%eax # Load extent
xor %edx,%edx
mov %es:DIR_EA_LEN(%bx),%dl
add %edx,%eax # Skip extended
mov $MEM_READ_BUFFER,%ebx # Read into the buffer
load_loop: mov %cl,%dh
cmp $MAX_READ_SEC,%cl # Truncate to max read size
jbe load_notrunc
mov $MAX_READ_SEC,%dh
load_notrunc: sub %dh,%cl # Update count
push %eax # Save
call read # Read it in
pop %eax # Restore
add $MAX_READ_SEC,%eax # Update LBA
add $MAX_READ,%ebx # Update dest addr
jcxz load_done # Done?
jmp load_loop # Keep going
load_done:
#
# Turn on the A20 address line
#
xor %ax,%ax # Turn A20 on
outb %al,$0xf2
mov $0x02,%al
outb %al,$0xf6
#
# Relocate the loader and BTX using a very lazy protected mode
#
mov $msg_relocate,%si # Display the
call putstr # relocation message
mov %es:(MEM_READ_BUFFER+AOUT_ENTRY),%edi # %edi is the destination
mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi # %esi is
# the start of the text
# segment
mov %es:(MEM_READ_BUFFER+AOUT_TEXT),%ecx # %ecx = length of the text
# segment
push %edi # Save entry point for later
lgdt gdtdesc # setup our own gdt
cli # turn off interrupts
mov %cr0,%eax # Turn on
or $0x1,%al # protected
mov %eax,%cr0 # mode
ljmp $SEL_SCODE,$pm_start # long jump to clear the
# instruction pre-fetch queue
.code32
pm_start: mov $SEL_SDATA,%ax # Initialize
mov %ax,%ds # %ds and
mov %ax,%es # %es to a flat selector
rep # Relocate the
movsb # text segment
add $(MEM_PAGE_SIZE - 1),%edi # pad %edi out to a new page
and $~(MEM_PAGE_SIZE - 1),%edi # for the data segment
mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment
rep # Relocate the
movsb # data segment
mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss
xor %eax,%eax # zero %eax
add $3,%cl # round %ecx up to
shr $2,%ecx # a multiple of 4
rep # zero the
stosl # bss
mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader
add $MEM_BTX_OFFSET,%esi # %esi -> BTX in the loader
mov $MEM_BTX_ADDRESS,%edi # %edi -> where BTX needs to go
movzwl 0xa(%esi),%ecx # %ecx -> length of BTX
rep # Relocate
movsb # BTX
ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM
.code16
pm_16: mov $SEL_RDATA,%ax # Initialize
mov %ax,%ds # %ds and
mov %ax,%es # %es to a real mode selector
mov %cr0,%eax # Turn off
and $~0x1,%al # protected
mov %eax,%cr0 # mode
ljmp $LOAD_SEG,$pm_end # Long jump to clear the
# instruction pre-fetch queue
pm_end: sti # Turn interrupts back on now
#
# Copy the BTX client to MEM_BTX_CLIENT
#
mov %cs,%ax
mov %ax,%ds
xor %ax,%ax
mov %ax,%es
mov $MEM_BTX_CLIENT,%di # Prepare to relocate
mov $btx_client,%si # the simple btx client
mov $(btx_client_end-btx_client),%cx # length of btx client
rep # Relocate the
movsb # simple BTX client
#
# Copy the boot[12] args to where the BTX client can see them
#
xor %ax,%ax
mov %ax,%ds
mov $MEM_ARG,%si # where the args are at now
mov $MEM_ARG_BTX,%di # where the args are moving to
mov $(MEM_ARG_SIZE/4),%cx # size of the arguments in longs
rep # Relocate
movsl # the words
#
# Save the entry point so the client can get to it later on
#
pop %eax # Restore saved entry point
stosl # and add it to the end of
# the arguments
#
# Now we just start up BTX and let it do the rest
#
mov $msg_jump,%si # Display the
call putstr # jump message
ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point
#
# Lookup the file in the path at [SI] from the root directory.
#
# Trashes: All but BX
# Returns: CF = 0 (success), BX = pointer to record
# CF = 1 (not found)
#
lookup: mov $VD_ROOTDIR+MEM_VOLDESC,%bx # Root directory record
push %bx
push %si
mov $msg_lookup,%si # Display lookup message
call putstr
pop %si
push %si
call putstr
mov $msg_lookup2,%si
call putstr
pop %si
pop %bx
lookup_dir: lodsb # Get first char of path
cmp $0,%al # Are we done?
je lookup_done # Yes
cmp $'/',%al # Skip path separator.
je lookup_dir
dec %si # Undo lodsb side effect
call find_file # Lookup first path item
jnc lookup_dir # Try next component
mov $msg_lookupfail,%si # Not found message
push %bx
call putstr
pop %bx
stc # Set carry
ret
lookup_done: mov $msg_lookupok,%si # Success message
push %bx
call putstr
pop %bx
clc # Clear carry
ret
#
# Lookup file at [SI] in directory whose record is at [BX].
#
# Trashes: All but returns
# Returns: CF = 0 (success), BX = pointer to record, SI = next path item
# CF = 1 (not found), SI = preserved
#
find_file: mov %es:DIR_EXTENT(%bx),%eax # Load extent
xor %edx,%edx
mov %es:DIR_EA_LEN(%bx),%dl
add %edx,%eax # Skip extended attributes
mov %eax,rec_lba # Save LBA
mov %es:DIR_SIZE(%bx),%eax # Save size
mov %eax,rec_size
xor %cl,%cl # Zero length
push %si # Save
ff.namelen: inc %cl # Update length
lodsb # Read char
cmp $0,%al # Nul?
je ff.namedone # Yes
cmp $'/',%al # Path separator?
jnz ff.namelen # No, keep going
ff.namedone: dec %cl # Adjust length and save
mov %cl,name_len
pop %si # Restore
ff.load: mov rec_lba,%eax # Load LBA
mov $MEM_DIR,%ebx # Address buffer
mov $1,%dh # One sector
call read # Read directory block
incl rec_lba # Update LBA to next block
ff.scan: mov %ebx,%edx # Check for EOF
sub $MEM_DIR,%edx
cmp %edx,rec_size
ja ff.scan.1
stc # EOF reached
ret
ff.scan.1: cmpb $0,%es:DIR_LEN(%bx) # Last record in block?
je ff.nextblock
push %si # Save
movzbw %es:DIR_NAMELEN(%bx),%si # Find end of string
ff.checkver: cmpb $'0',%es:DIR_NAME-1(%bx,%si) # Less than '0'?
jb ff.checkver.1
cmpb $'9',%es:DIR_NAME-1(%bx,%si) # Greater than '9'?
ja ff.checkver.1
dec %si # Next char
jnz ff.checkver
jmp ff.checklen # All numbers in name, so
# no version
ff.checkver.1: movzbw %es:DIR_NAMELEN(%bx),%cx
cmp %cx,%si # Did we find any digits?
je ff.checkdot # No
cmpb $';',%es:DIR_NAME-1(%bx,%si) # Check for semicolon
jne ff.checkver.2
dec %si # Skip semicolon
mov %si,%cx
mov %cl,%es:DIR_NAMELEN(%bx) # Adjust length
jmp ff.checkdot
ff.checkver.2: mov %cx,%si # Restore %si to end of string
ff.checkdot: cmpb $'.',%es:DIR_NAME-1(%bx,%si) # Trailing dot?
jne ff.checklen # No
decb %es:DIR_NAMELEN(%bx) # Adjust length
ff.checklen: pop %si # Restore
movzbw name_len,%cx # Load length of name
cmp %cl,%es:DIR_NAMELEN(%bx) # Does length match?
je ff.checkname # Yes, check name
ff.nextrec: add %es:DIR_LEN(%bx),%bl # Next record
adc $0,%bh
jmp ff.scan
ff.nextblock: subl $SECTOR_SIZE,rec_size # Adjust size
jnc ff.load # If subtract ok, keep going
ret # End of file, so not found
ff.checkname: lea DIR_NAME(%bx),%di # Address name in record
push %si # Save
repe cmpsb # Compare name
je ff.match # We have a winner!
pop %si # Restore
jmp ff.nextrec # Keep looking.
ff.match: add $2,%sp # Discard saved %si
clc # Clear carry
ret
#
# Load DH sectors starting at LBA EAX into [EBX].
#
# Trashes: EAX
#
read: push %es # Save
push %bp
push %dx
push %cx
push %ebx
mov %bx,%bp # Set destination address
and $0x000f,%bp
shr $4,%ebx
mov %bx,%es
xor %bx,%bx # Set read bytes
mov %dh,%bl
shl $SECTOR_SHIFT,%bx # 2048 bytes/sec
mov %ax,%cx # Set LBA
shr $16,%eax
mov %ax,%dx
read.retry: mov $0x06,%ah # BIOS device read
mov drive,%al
and $0x7f,%al
call twiddle # Entertain the user
int $0x1b # Call BIOS
jc read.fail # Worked?
pop %ebx # Restore
pop %cx
pop %dx
pop %bp
pop %es
ret # Return
read.fail: cmp $ERROR_TIMEOUT,%ah # Timeout?
je read.retry # Yes, Retry.
read.error: mov %ah,%al # Save error
mov $hex_error,%di # Format it
call hex8 # as hex
mov $msg_badread,%si # Display Read error message
jmp error
#
# Output the "twiddle"
#
twiddle: push %ax # Save
push %bx # Save
mov twiddle_index,%al # Load index
mov twiddle_chars,%bx # Address table
inc %al # Next
and $3,%al # char
mov %al,twiddle_index # Save index for next call
xlat # Get char
call putc # Output it
pop %bx # Restore
pop %ax # Restore
ret
#
# Convert AL to hex, saving the result to [EDI].
#
hex8: pushl %eax # Save
shrb $0x4,%al # Do upper
call hex8.1 # 4
popl %eax # Restore
hex8.1: andb $0xf,%al # Get lower 4
cmpb $0xa,%al # Convert
sbbb $0x69,%al # to hex
das # digit
orb $0x20,%al # To lower case
mov %al,(%di) # Save char
inc %di
ret # (Recursive)
#
# BTX client to start btxldr
#
.code32
btx_client: mov $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi
# %ds:(%esi) -> end
# of boot[12] args
mov $(MEM_ARG_SIZE/4),%ecx # Number of words to push
std # Go backwards
push_arg: lodsl # Read argument
push %eax # Push it onto the stack
loop push_arg # Push all of the arguments
cld # In case anyone depends on this
pushl MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE # Entry point of
# the loader
push %eax # Emulate a near call
mov $0x1,%eax # 'exec' system call
int $INT_SYS # BTX system call
btx_client_end:
.code16
.p2align 4
#
# Global descriptor table.
#
gdt: .word 0x0,0x0,0x0,0x0 # Null entry
.word 0xffff,0x0000,0x9200,0x00cf # SEL_SDATA
.word 0xffff,0x0000,0x9200,0x0000 # SEL_RDATA
.word 0xffff,LOAD_SEG<<4,0x9a00,0x00cf # SEL_SCODE (32-bit)
.word 0xffff,LOAD_SEG<<4,0x9a00,0x008f # SEL_SCODE16 (16-bit)
gdt.1:
#
# Pseudo-descriptors.
#
gdtdesc: .word gdt.1-gdt-1 # Limit
.long LOAD_SEG<<4 + gdt # Base
#
# BOOT device
#
drive: .byte 0
cylinder: .word 0
#
# State for searching dir
#
rec_lba: .long 0x0 # LBA (adjusted for EA)
rec_size: .long 0x0 # File size
name_len: .byte 0x0 # Length of current name
cursor: .word 0
twiddle_index: .byte 0x0
msg_welcome: .asciz "CD Loader 1.2\r\n\n"
msg_bootinfo: .asciz "Building the boot loader arguments\r\n"
msg_relocate: .asciz "Relocating the loader and the BTX\r\n"
msg_jump: .asciz "Starting the BTX loader\r\n"
msg_badread: .ascii "Read Error: 0x"
hex_error: .ascii "00\r\n"
msg_novd: .asciz "Could not find Primary Volume Descriptor\r\n"
msg_lookup: .asciz "Looking up "
msg_lookup2: .asciz "... "
msg_lookupok: .asciz "Found\r\n"
msg_lookupfail: .asciz "File not found\r\n"
msg_load2big: .asciz "File too big\r\n"
msg_failed: .asciz "Boot failed\r\n"
twiddle_chars: .ascii "|/-\\"
loader_paths: .asciz "/BOOT.PC98/LOADER"
.asciz "/boot.pc98/loader"
.asciz "/BOOT/LOADER"
.asciz "/boot/loader"
.byte 0
/* Boot signature */
.org SIG2_OFF,0x90
.word 0xaa55 # Magic number
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