7684ab55c6
actual end of the section. The new gas (binutils) puts in additional padding which was misaligning the concatenated btx loader. Reported by: Oliver Hartmann <ohartman@klima.physik.uni-mainz.de>, Harti Brandt <brandt@fokus.gmd.de> Tested by: Oliver Hartmann <ohartman@klima.physik.uni-mainz.de>, David Wolfskill <dhw@whistle.com>, ps Reviewed by: jhb MFC after: 1 day
262 lines
8.0 KiB
ArmAsm
262 lines
8.0 KiB
ArmAsm
#
|
|
# Copyright (c) 2000 John Baldwin
|
|
# All rights reserved.
|
|
#
|
|
# Redistribution and use in source and binary forms are freely
|
|
# permitted provided that the above copyright notice and this
|
|
# paragraph and the following disclaimer are duplicated in all
|
|
# such forms.
|
|
#
|
|
# This software is provided "AS IS" and without any express or
|
|
# implied warranties, including, without limitation, the implied
|
|
# warranties of merchantability and fitness for a particular
|
|
# purpose.
|
|
#
|
|
|
|
# $FreeBSD$
|
|
|
|
#
|
|
# This simple program is a preloader for the normal boot3 loader. It is simply
|
|
# prepended to the beginning of a fully built and btxld'd loader. It then
|
|
# copies the loader to the address boot2 normally loads it, emulates the
|
|
# boot[12] environment (protected mode, a bootinfo struct, etc.), and then jumps
|
|
# to the start of btxldr to start the boot process. This method allows a stock
|
|
# /boot/loader to be used w/o having to fully rewrite boot[12] to handle the
|
|
# cd9660 file system.
|
|
#
|
|
|
|
#
|
|
# Memory locations.
|
|
#
|
|
.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
|
|
#
|
|
# 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
|
|
#
|
|
# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry
|
|
# point)
|
|
#
|
|
.code16
|
|
.globl start
|
|
.org 0x0, 0x0
|
|
#
|
|
# BTX program loader for CD booting
|
|
#
|
|
start: cld # string ops inc
|
|
xorw %ax, %ax # zero %ax
|
|
movw %ax, %ss # setup the
|
|
movw $start, %sp # stack
|
|
pushw %dx # save the BIOS boot device in
|
|
# %dl for later
|
|
movw %ax, %ds # setup the
|
|
movw %ax, %es # data segments
|
|
movw $welcome_msg, %si # %ds:(%si) -> welcome message
|
|
callw putstr # display the welcome message
|
|
#
|
|
# Setup the arguments that the loader is expecting from boot[12]
|
|
#
|
|
movw $bootinfo_msg, %si # %ds:(%si) -> boot args message
|
|
callw putstr # display the message
|
|
movw $MEM_ARG, %bx # %ds:(%bx) -> boot args
|
|
movw %bx, %di # %es:(%di) -> boot args
|
|
xorl %eax, %eax # zero %eax
|
|
movw $(MEM_ARG_SIZE/4), %cx # Size of arguments in 32-bit
|
|
# dwords
|
|
rep # Clear the arguments
|
|
stosl # to zero
|
|
popw %dx # restore BIOS boot device
|
|
movb %dl, 0x4(%bx) # set kargs->bootdev
|
|
orb $KARGS_FLAGS_CD, 0x8(%bx) # kargs->bootflags |=
|
|
# KARGS_FLAGS_CD
|
|
#
|
|
# Turn on the A20 address line
|
|
#
|
|
callw seta20 # Turn A20 on
|
|
#
|
|
# Relocate the loader and BTX using a very lazy protected mode
|
|
#
|
|
movw $relocate_msg, %si # Display the
|
|
callw putstr # relocation message
|
|
movl end+AOUT_ENTRY, %edi # %edi is the destination
|
|
movl $(end+AOUT_HEADER), %esi # %esi is
|
|
# the start of the text
|
|
# segment
|
|
movl end+AOUT_TEXT, %ecx # %ecx = length of the text
|
|
# segment
|
|
lgdt gdtdesc # setup our own gdt
|
|
cli # turn off interrupts
|
|
movl %cr0, %eax # Turn on
|
|
orb $0x1, %al # protected
|
|
movl %eax, %cr0 # mode
|
|
ljmp $SEL_SCODE,$pm_start # long jump to clear the
|
|
# instruction pre-fetch queue
|
|
.code32
|
|
pm_start: movw $SEL_SDATA, %ax # Initialize
|
|
movw %ax, %ds # %ds and
|
|
movw %ax, %es # %es to a flat selector
|
|
rep # Relocate the
|
|
movsb # text segment
|
|
addl $(MEM_PAGE_SIZE - 1), %edi # pad %edi out to a new page
|
|
andl $~(MEM_PAGE_SIZE - 1), %edi # for the data segment
|
|
movl end+AOUT_DATA, %ecx # size of the data segment
|
|
rep # Relocate the
|
|
movsb # data segment
|
|
movl end+AOUT_BSS, %ecx # size of the bss
|
|
xorl %eax, %eax # zero %eax
|
|
addb $3, %cl # round %ecx up to
|
|
shrl $2, %ecx # a multiple of 4
|
|
rep # zero the
|
|
stosl # bss
|
|
movl end+AOUT_ENTRY, %esi # %esi -> relocated loader
|
|
addl $MEM_BTX_OFFSET, %esi # %esi -> BTX in the loader
|
|
movl $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: movw $SEL_RDATA, %ax # Initialize
|
|
movw %ax, %ds # %ds and
|
|
movw %ax, %es # %es to a real mode selector
|
|
movl %cr0, %eax # Turn off
|
|
andb $~0x1, %al # protected
|
|
movl %eax, %cr0 # mode
|
|
ljmp $0,$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
|
|
#
|
|
xorw %ax, %ax # zero %ax and set
|
|
movw %ax, %ds # %ds and %es
|
|
movw %ax, %es # to segment 0
|
|
movw $MEM_BTX_CLIENT, %di # Prepare to relocate
|
|
movw $btx_client, %si # the simple btx client
|
|
movw $(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
|
|
#
|
|
movw $MEM_ARG, %si # where the args are at now
|
|
movw $MEM_ARG_BTX, %di # where the args are moving to
|
|
movw $(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
|
|
#
|
|
movl end+AOUT_ENTRY, %eax # load the entry point
|
|
stosl # add it to the end of the
|
|
# arguments
|
|
#
|
|
# Now we just start up BTX and let it do the rest
|
|
#
|
|
movw $jump_message, %si # Display the
|
|
callw putstr # jump message
|
|
ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point
|
|
|
|
#
|
|
# Display a null-terminated string
|
|
#
|
|
putstr: lodsb # load %al from %ds:(%si)
|
|
testb %al,%al # stop at null
|
|
jnz putc # if the char != null, output it
|
|
retw # return when null is hit
|
|
putc: movw $0x7,%bx # attribute for output
|
|
movb $0xe,%ah # BIOS: put_char
|
|
int $0x10 # call BIOS, print char in %al
|
|
jmp putstr # keep looping
|
|
|
|
#
|
|
# Enable A20
|
|
#
|
|
seta20: cli # Disable interrupts
|
|
seta20.1: inb $0x64,%al # Get status
|
|
testb $0x2,%al # Busy?
|
|
jnz seta20.1 # Yes
|
|
movb $0xd1,%al # Command: Write
|
|
outb %al,$0x64 # output port
|
|
seta20.2: inb $0x64,%al # Get status
|
|
testb $0x2,%al # Busy?
|
|
jnz seta20.2 # Yes
|
|
movb $0xdf,%al # Enable
|
|
outb %al,$0x60 # A20
|
|
sti # Enable interrupts
|
|
retw # To caller
|
|
|
|
#
|
|
# BTX client to start btxldr
|
|
#
|
|
.code32
|
|
btx_client: movl $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi
|
|
# %ds:(%esi) -> end
|
|
# of boot[12] args
|
|
movl $(MEM_ARG_SIZE/4), %ecx # Number of words to push
|
|
std # Go backwards
|
|
push_arg: lodsl # Read argument
|
|
pushl %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
|
|
pushl %eax # Emulate a near call
|
|
movl $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,0x0,0x9200,0xcf # SEL_SDATA
|
|
.word 0xffff,0x0,0x9200,0x0 # SEL_RDATA
|
|
.word 0xffff,0x0,0x9a00,0xcf # SEL_SCODE (32-bit)
|
|
.word 0xffff,0x0,0x9a00,0x8f # SEL_SCODE16 (16-bit)
|
|
gdt.1:
|
|
#
|
|
# Pseudo-descriptors.
|
|
#
|
|
gdtdesc: .word gdt.1-gdt-1 # Limit
|
|
.long gdt # Base
|
|
|
|
welcome_msg: .asciz "CD Loader 1.00\r\n\n"
|
|
bootinfo_msg: .asciz "Building the boot loader arguments\r\n"
|
|
relocate_msg: .asciz "Relocating the loader and the BTX\r\n"
|
|
jump_message: .asciz "Starting the BTX loader\r\n"
|
|
|
|
.p2align 4
|
|
end:
|