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/*-
* Copyright (c) 2007 Yahoo!, Inc.
* All rights reserved.
* Written by: John Baldwin <jhb@FreeBSD.org>
*
* 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.
*
* $FreeBSD$
*
* Partly from: src/sys/boot/i386/boot2/boot1.S 1.31
*/
/* Memory Locations */
.set MEM_REL,0x700 # Relocation address
.set MEM_ARG,0x900 # Arguments
.set MEM_ORG,0x7c00 # Origin
.set MEM_BUF,0x8cec # Load area
.set MEM_BTX,0x9000 # BTX start
.set MEM_JMP,0x9010 # BTX entry point
.set MEM_USR,0xa000 # Client start
.set BDA_BOOT,0x472 # Boot howto flag
/* Misc. Constants */
.set SIZ_PAG,0x1000 # Page size
.set SIZ_SEC,0x200 # Sector size
.set COPY_BLKS,0x8 # Number of blocks
# to copy for boot2 (<= 15)
.set COPY_BLK_SZ,0x8000 # Copy in 32k blocks; must be
# a multiple of 16 bytes
.globl start
.code16
/*
* Copy BTX and boot2 to the right locations and start it all up.
*/
/*
* Setup the segment registers to flat addressing (segment 0) and setup the
* stack to end just below the start of our code.
*/
start: xor %cx,%cx # Zero
mov %cx,%es # Address
mov %cx,%ds # data
mov %cx,%ss # Set up
mov $start,%sp # stack
/*
* BTX is right after us at 'end'. We read the length of BTX out of
* its header to find boot2. We need to copy boot2 to MEM_USR and BTX
* to MEM_BTX. Since those might overlap, we have to copy boot2
* backwards first and then copy BTX. We aren't sure exactly how long
* boot2 is, but it's currently under 256kB so we'll copy 8 blocks of 32kB
* each; this can be adjusted via COPY_BLK and COPY_BLK_SZ above.
*/
mov $end,%bx # BTX
mov 0xa(%bx),%si # Get BTX length and set
add %bx,%si # %si to start of boot2
dec %si # Set %ds:%si to point at the
mov %si,%ax # last byte we want to copy
shr $4,%ax # from boot2, with %si made as
add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # small as possible.
and $0xf,%si #
mov %ax,%ds #
mov $MEM_USR/16,%ax # Set %es:(-1) to point at
add $(COPY_BLKS*COPY_BLK_SZ/16),%ax # the last byte we
mov %ax,%es # want to copy boot2 into.
mov $COPY_BLKS,%bx # Copy COPY_BLKS 32k blocks
copyloop:
add $COPY_BLK_SZ,%si # Adjust %ds:%si to point at
mov %ds,%ax # the end of the next 32k to
sub $COPY_BLK_SZ/16,%ax # copy from boot2
mov %ax,%ds
mov $COPY_BLK_SZ-1,%di # Adjust %es:%di to point at
mov %es,%ax # the end of the next 32k into
sub $COPY_BLK_SZ/16,%ax # which we want boot2 copied
mov %ax,%es
mov $COPY_BLK_SZ,%cx # Copy 32k
std
rep movsb
dec %bx
jnz copyloop
mov %cx,%ds # Reset %ds and %es
mov %cx,%es
mov $end,%bx # BTX
mov 0xa(%bx),%cx # Get BTX length and set
mov %bx,%si # %si to end of BTX
mov $MEM_BTX,%di # %di -> end of BTX at
add %cx,%si # MEM_BTX
add %cx,%di
dec %si
dec %di
rep movsb # Move BTX
cld # String ops inc
/*
* Enable A20 so we can access memory above 1 meg.
* Use the zero-valued %cx as a timeout for embedded hardware which do not
* have a keyboard controller.
*/
seta20: cli # Disable interrupts
seta20.1: dec %cx # Timeout?
jz seta20.3 # Yes
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
seta20.3: sti # Enable interrupts
/*
* Save drive number from BIOS so boot2 can see it and start BTX.
*/
movb %dl,MEM_ARG
jmp MEM_JMP # Start BTX
end:
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