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267 lines
8.1 KiB
ArmAsm
267 lines
8.1 KiB
ArmAsm
/*
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* Copyright (c) 1998 Robert Nordier
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms are freely
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* permitted provided that the above copyright notice and this
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* paragraph and the following disclaimer are duplicated in all
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* such forms.
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*
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* This software is provided "AS IS" and without any express or
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* implied warranties, including, without limitation, the implied
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* warranties of merchantability and fitness for a particular
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* purpose.
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*
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* $FreeBSD$
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*/
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/* Memory Locations */
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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,0x8000 # 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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/* Partition Constants */
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.set PRT_OFF,0x1be # Partition offset
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.set PRT_NUM,0x4 # Partitions
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.set PRT_BSD,0xa5 # Partition type
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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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.set NSECT,0x80
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.globl start
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.code16
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/*
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* Load the rest of zfsboot2 and BTX up, copy the parts to the right locations,
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* 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: cld # String ops inc
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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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* Load the MBR and look for the first FreeBSD slice. We use the fake
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* partition entry below that points to the MBR when we call read.
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* The first pass looks for the first active FreeBSD slice. The
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* second pass looks for the first non-active FreeBSD slice if the
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* first one fails.
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*/
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call check_edd # Make sure EDD works
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mov $part4,%si # Dummy partition
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xor %eax,%eax # Read MBR
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movl $MEM_BUF,%ebx # from first
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call read # sector
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mov $0x1,%cx # Two passes
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main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table
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movb $0x1,%dh # Partition
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main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type?
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jne main.3 # No
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jcxz main.5 # If second pass
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testb $0x80,(%si) # Active?
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jnz main.5 # Yes
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main.3: add $0x10,%si # Next entry
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incb %dh # Partition
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cmpb $0x1+PRT_NUM,%dh # In table?
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jb main.2 # Yes
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dec %cx # Do two
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jcxz main.1 # passes
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/*
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* If we get here, we didn't find any FreeBSD slices at all, so print an
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* error message and die.
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*/
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mov $msg_part,%si # Message
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jmp error # Error
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/*
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* Ok, we have a slice and drive in %dx now, so use that to locate and
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* load boot2. %si references the start of the slice we are looking
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* for, so go ahead and load up the 128 sectors starting at sector 1024
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* (i.e. after the two vdev labels). We don't have do anything fancy
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* here to allow for an extra copy of boot1 and a partition table
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* (compare to this section of the UFS bootstrap) so we just load it
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* all at 0x9000. The first part of boot2 is BTX, which wants to run
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* at 0x9000. The boot2.bin binary starts right after the end of BTX,
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* so we have to figure out where the start of it is and then move the
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* binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000,
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* but when we use btxld to create zfsboot2, we use an entry point of
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* 0x2000. That entry point is relative to MEM_USR; thus boot2.bin
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* starts at 0xc000.
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*
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* The load area and the target area for the client overlap so we have
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* to use a decrementing string move. We also play segment register
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* games with the destination address for the move so that the client
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* can be larger than 16k (which would overflow the zero segment since
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* the client starts at 0xc000).
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*/
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main.5: mov %dx,MEM_ARG # Save args
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mov $NSECT,%cx # Sector count
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movl $1024,%eax # Offset to boot2
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mov $MEM_BTX,%ebx # Destination buffer
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main.6: pushal # Save params
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call read # Read disk
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popal # Restore
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incl %eax # Advance to
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add $SIZ_SEC,%ebx # next sector
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loop main.6 # If not last, read another
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mov MEM_BTX+0xa,%bx # Get BTX length
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mov $NSECT*SIZ_SEC-1,%di # Size of load area (less one)
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mov %di,%si # End of load area, 0x9000 rel
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sub %bx,%di # End of client, 0xc000 rel
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mov %di,%cx # Size of
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inc %cx # client
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mov $(MEM_BTX)>>4,%dx # Segment
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mov %dx,%ds # addressing 0x9000
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mov $(MEM_USR+2*SIZ_PAG)>>4,%dx # Segment
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mov %dx,%es # addressing 0xc000
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std # Move with decrement
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rep # Relocate
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movsb # client
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cld # Back to increment
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xor %dx,%dx # Back
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mov %ds,%dx # to zero
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mov %dx,%es # segment
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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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jmp start+MEM_JMP-MEM_ORG # Start BTX
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/*
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* Read a sector from the disk. Sets up an EDD packet on the stack
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* and passes it to read. We assume that the destination address is
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* always segment-aligned.
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*
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* %eax - int - LBA to read in relative to partition start
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* %ebx - ptr - destination address
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* %dl - byte - drive to read from
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* %si - ptr - MBR partition entry
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*/
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read: xor %ecx,%ecx # Get
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addl 0x8(%si),%eax # LBA
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adc $0,%ecx
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pushl %ecx # Starting absolute block
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pushl %eax # block number
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shr $4,%ebx # Convert to segment
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push %bx # Address of
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push $0 # transfer buffer
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push $0x1 # Read 1 sector
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push $0x10 # Size of packet
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mov %sp,%si # Packet pointer
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mov $0x42,%ah # BIOS: Extended
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int $0x13 # read
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jc read.1 # If error, fail
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lea 0x10(%si),%sp # Clear stack
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ret # If success, return
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read.1: mov %ah,%al # Format
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mov $read_err,%di # error
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call hex8 # code
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mov $msg_read,%si # Set the error message and
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# fall through to the error
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# routine
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/*
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* Print out the error message pointed to by %ds:(%si) followed
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* by a prompt, wait for a keypress, and then reboot the machine.
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*/
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error: callw putstr # Display message
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mov $prompt,%si # Display
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callw putstr # prompt
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xorb %ah,%ah # BIOS: Get
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int $0x16 # keypress
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movw $0x1234, BDA_BOOT # Do a warm boot
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ljmp $0xffff,$0x0 # reboot the machine
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/*
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* Display a null-terminated string using the BIOS output.
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*/
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putstr.0: mov $0x7,%bx # Page:attribute
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movb $0xe,%ah # BIOS: Display
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int $0x10 # character
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putstr: lodsb # Get char
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testb %al,%al # End of string?
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jne putstr.0 # No
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ret # To caller
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/*
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* Check to see if the disk supports EDD. zfsboot requires EDD and does not
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* support older C/H/S disk I/O.
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*/
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check_edd: cmpb $0x80,%dl # Hard drive?
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jb check_edd.1 # No, fail to boot
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mov $0x55aa,%bx # Magic
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push %dx # Save
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movb $0x41,%ah # BIOS: Check
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int $0x13 # extensions present
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pop %dx # Restore
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jc check_edd.1 # If error, fail
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cmp $0xaa55,%bx # Magic?
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jne check_edd.1 # No, so fail
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testb $0x1,%cl # Packet interface?
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jz check_edd.1 # No, so fail
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ret # EDD ok, keep booting
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check_edd.1: mov $msg_chs,%si # Warn that CHS is
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jmp error # unsupported and fail
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/*
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* AL to hex, saving the result to [EDI].
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*/
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hex8: push %ax # Save
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shrb $0x4,%al # Do upper
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call hex8.1 # 4
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pop %ax # Restore
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hex8.1: andb $0xf,%al # Get lower 4
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cmpb $0xa,%al # Convert
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sbbb $0x69,%al # to hex
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das # digit
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orb $0x20,%al # To lower case
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stosb # Save char
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ret # (Recursive)
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/* Messages */
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msg_chs: .asciz "CHS not supported"
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msg_read: .ascii "Read error: "
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read_err: .asciz "XX"
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msg_part: .asciz "Boot error"
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prompt: .asciz "\r\n"
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.org PRT_OFF,0x90
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/* Partition table */
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.fill 0x30,0x1,0x0
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part4: .byte 0x80, 0x00, 0x01, 0x00
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.byte 0xa5, 0xfe, 0xff, 0xff
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.byte 0x00, 0x00, 0x00, 0x00
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.byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh
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.word 0xaa55 # Magic number
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