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126 lines
4.2 KiB
ArmAsm
126 lines
4.2 KiB
ArmAsm
/*-
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* Copyright (c) 2007 Yahoo!, Inc.
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* All rights reserved.
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* Written by: John Baldwin <jhb@FreeBSD.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of any co-contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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* Partly from: src/sys/boot/i386/boot2/boot1.S 1.31
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*/
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/* Memory Locations */
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.set MEM_REL,0x700 # Relocation address
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.set MEM_ARG,0x900 # Arguments
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.set MEM_ORG,0x7c00 # Origin
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.set MEM_BUF,0x8cec # Load area
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.set MEM_BTX,0x9000 # BTX start
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.set MEM_JMP,0x9010 # BTX entry point
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.set MEM_USR,0xa000 # Client start
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.set BDA_BOOT,0x472 # Boot howto flag
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/* Misc. Constants */
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.set SIZ_PAG,0x1000 # Page size
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.set SIZ_SEC,0x200 # Sector size
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.globl start
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.code16
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/*
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* Copy BTX and boot2 to the right locations and start it all up.
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*/
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/*
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* Setup the segment registers to flat addressing (segment 0) and setup the
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* stack to end just below the start of our code.
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*/
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start: xor %cx,%cx # Zero
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mov %cx,%es # Address
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mov %cx,%ds # data
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mov %cx,%ss # Set up
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mov $start,%sp # stack
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/*
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* BTX is right after us at 'end'. We read the length of BTX out of
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* its header to find boot2. We need to copy boot2 to MEM_USR and BTX
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* to MEM_BTX. Since those might overlap, we have to copy boot2
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* backwards first and then copy BTX. We aren't sure exactly how long
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* boot2 is, but we assume it can't be longer than 64k, so we just always
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* copy 64k.
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*/
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mov $end,%bx # BTX
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mov 0xa(%bx),%si # Get BTX length and set
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add %bx,%si # %si to start of boot2
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mov %si,%ax # Align %ds:%si on a
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shr $4,%ax # paragraph boundary
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and $0xf,%si # with the smallest
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mov %ax,%ds # possible %si
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add $(64 * 1024 - 16),%si
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mov $MEM_USR/16,%ax # Point %es:%di at end of
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mov $(64 * 1024 - 16),%di # largest boot2 range
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mov %ax,%es
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std
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mov %di,%cx # Copy 64k - paragraph + 1
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inc %cx # bytes
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rep movsb
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mov %cx,%ds # Reset %ds and %es
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mov %cx,%es
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mov 0xa(%bx),%cx # Get BTX length and set
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mov %bx,%si # %si to end of BTX
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mov $MEM_BTX,%di # %di -> end of BTX at
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add %cx,%si # MEM_BTX
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add %cx,%di
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dec %si
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dec %di
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rep movsb # Move BTX
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cld # String ops inc
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/*
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* Enable A20 so we can access memory above 1 meg.
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* Use the zero-valued %cx as a timeout for embedded hardware which do not
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* have a keyboard controller.
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*/
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seta20: cli # Disable interrupts
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seta20.1: dec %cx # Timeout?
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jz seta20.3 # Yes
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inb $0x64,%al # Get status
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testb $0x2,%al # Busy?
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jnz seta20.1 # Yes
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movb $0xd1,%al # Command: Write
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outb %al,$0x64 # output port
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seta20.2: inb $0x64,%al # Get status
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testb $0x2,%al # Busy?
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jnz seta20.2 # Yes
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movb $0xdf,%al # Enable
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outb %al,$0x60 # A20
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seta20.3: sti # Enable interrupts
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/*
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* Save drive number from BIOS so boot2 can see it and start BTX.
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*/
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movb %dl,MEM_ARG
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jmp MEM_JMP # Start BTX
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end:
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