269 lines
7.5 KiB
ArmAsm
269 lines
7.5 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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# $Id: boot0.s,v 1.9 1999/06/18 21:49:18 rnordier Exp $
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# A 512-byte boot manager.
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.set NHRDRV,0x475 # Number of hard drives
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.set ORIGIN,0x600 # Execution address
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.set FAKE,0x800 # Partition entry
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.set LOAD,0x7c00 # Load address
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.set PRT_OFF,0x1be # Partition table
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.set TBL0SZ,0x3 # Table 0 size
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.set TBL1SZ,0xa # Table 1 size
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.set MAGIC,0xaa55 # Magic: bootable
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.set KEY_ENTER,0x1c # Enter key scan code
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.set KEY_F1,0x3b # F1 key scan code
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.set _NXTDRV,-0x48 # Next drive
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.set _OPT,-0x47 # Default option
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.set _SETDRV,-0x46 # Drive to force
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.set _FLAGS,-0x45 # Flags
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.set _TICKS,-0x44 # Timeout ticks
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.set _FAKE,0x0 # Fake partition entry
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.set _MNUOPT,0xc # Menu options
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.globl start # Entry point
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start: cld # String ops inc
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xorl %eax,%eax # Zero
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movl %eax,%es # Address
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movl %eax,%ds # data
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movl %eax,%ss # Set up
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movwir(LOAD,_sp) # stack
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movl %esp,%esi # Source
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movwir(start,_di) # Destination
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movwir(0x100,_cx) # Word count
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rep # Relocate
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movsl # code
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movl %edi,%ebp # Address variables
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movb $0x8,%cl # Words to clear
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rep # Zero
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stosl # them
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incb1(-0xe,_di_) # Sector number
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jmpnwi(main-LOAD+ORIGIN) # To relocated code
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main: tstbi1(0x20,_FLAGS,_bp_) # Set number drive?
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jnz main.1 # Yes
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testb %dl,%dl # Drive number valid?
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js main.2 # Possibly
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main.1: movb1r(_SETDRV,_bp_,_dl) # Drive number to use
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main.2: movbr1(_dl,_FAKE,_bp_) # Save drive number
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callwi(putn) # To new line
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pushl %edx # Save drive number
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movwir(partbl+0x4,_bx) # Partition table
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xorl %edx,%edx # Item number
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main.3: movbr1(_ch,-0x4,_bx_) # Zero active flag
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btwr1(_dx,_FLAGS,_bp_) # Entry enabled?
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jnc main.5 # No
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movb0r(_bx_,_al) # Load type
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movwir(tables,_di) # Lookup tables
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movb $TBL0SZ,%cl # Number of entries
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repne # Exclude
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scasb # partition?
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je main.5 # Yes
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movb $TBL1SZ,%cl # Number of entries
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repne # Known
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scasb # type?
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jne main.4 # No
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addwir(TBL1SZ,_di) # Adjust
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main.4: movb0r(_di_,_cl) # Partition
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addl %ecx,%edi # description
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callwi(putx) # Display it
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main.5: incl %edx # Next item
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addb $0x10,%bl # Next entry
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jnc main.3 # Till done
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popl %eax # Drive number
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subb $0x80-0x1,%al # Does next
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cmpbmr(NHRDRV,_al) # drive exist?
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jb main.6 # Yes
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decl %eax # Already drive 0?
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jz main.7 # Yes
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xorb %al,%al # Drive 0
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main.6: addb $'0'|0x80,%al # Save next
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movbr1(_al,_NXTDRV,_bp_) # drive number
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movwir(drive,_di) # Display
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callwi(putx) # item
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main.7: movwir(prompt,_si) # Display
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callwi(putstr) # prompt
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movb1r(_OPT,_bp_,_dl) # Display
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decl %esi # default
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callwi(putkey) # key
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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movl %edx,%edi # Ticks when
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addw1r(_TICKS,_bp_,_di) # timeout
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main.8: movb $0x1,%ah # BIOS: Check
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int $0x16 # for keypress
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jnz main.11 # Have one
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xorb %ah,%ah # BIOS: Get
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int $0x1a # system time
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cmpl %edi,%edx # Timeout?
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jb main.8 # No
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main.9: movb1r(_OPT,_bp_,_al) # Load default
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jmp main.12 # Join common code
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main.10: movb $0x7,%al # Signal
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callwi(putchr) # error
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main.11: xorb %ah,%ah # BIOS: Get
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int $0x16 # keypress
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movb %ah,%al # Scan code
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cmpb $KEY_ENTER,%al # Enter pressed?
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je main.9 # Yes
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subb $KEY_F1,%al # Less F1 scan code
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cmpb $0x4,%al # F1..F5?
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ja main.10 # No
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main.12: cwtl # Option
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btwr1(_ax,_MNUOPT,_bp_) # enabled?
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jnc main.10 # No
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movbr1(_al,_OPT,_bp_) # Save option
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movwir(FAKE,_si) # Partition for write
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movb0r(_si_,_dl) # Drive number
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movl %esi,%ebx # Partition for read
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cmpb $0x4,%al # F5 pressed?
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pushfl # Save
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je main.13 # Yes
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shlb $0x4,%al # Point to
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addwia(partbl) # selected
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xchgl %ebx,%eax # partition
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movbi0(0x80,_bx_) # Flag active
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main.13: pushl %ebx # Save
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tstbi1(0x40,_FLAGS,_bp_) # No updates?
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jnz main.14 # Yes
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movwir(start,_bx) # Data to write
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movb $0x3,%ah # Write sector
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callwi(intx13) # to disk
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main.14: popl %esi # Restore
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popfl # Restore
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jne main.15 # If not F5
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movb1r(_NXTDRV,_bp_,_dl) # Next drive
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subb $'0',%dl # number
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main.15: movwir(LOAD,_bx) # Address for read
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movb $0x2,%ah # Read sector
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callwi(intx13) # from disk
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jc main.10 # If error
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cmpwi2(MAGIC,0x1fe,_bx_) # Bootable?
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jne main.10 # No
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pushl %esi # Save
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movwir(crlf,_si) # Leave some
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callwi(puts) # space
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popl %esi # Restore
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jmp *%ebx # Invoke bootstrap
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# Display routines
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putkey: movb $'F',%al # Display
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callwi(putchr) # 'F'
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movb $'1',%al # Prepare
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addb %dl,%al # digit
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jmp putstr.1 # Display the rest
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putx: btswr1(_dx,_MNUOPT,_bp_) # Enable menu option
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movwir(item,_si) # Display
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callwi(putkey) # key
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movl %edi,%esi # Display the rest
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puts: callwi(putstr) # Display string
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putn: movwir(crlf,_si) # To next line
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putstr: lodsb # Get byte
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testb $0x80,%al # End of string?
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jnz putstr.2 # Yes
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putstr.1: callwi(putchr) # Display char
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jmp putstr # Continue
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putstr.2: andb $~0x80,%al # Clear MSB
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putchr: pushl %ebx # Save
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movwir(0x7,_bx) # Page:attribute
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movb $0xe,%ah # BIOS: Display
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int $0x10 # character
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popl %ebx # Restore
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ret # To caller
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# One-sector disk I/O routine
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intx13: movb1r(0x1,_si_,_dh) # Load head
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movw1r(0x2,_si_,_cx) # Load cylinder:sector
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movb $0x1,%al # Sector count
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pushl %esi # Save
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movl %esp,%edi # Save
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tstbi1(0x80,_FLAGS,_bp_) # Use packet interface?
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jz intx13.1 # No
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o16 # Set
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pushb $0x0 # the
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o16 # LBA
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pushw1(0x8,_si_) # address
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pushl %es # Set the transfer
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pushl %ebx # buffer address
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pushb $0x1 # Block count
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pushb $0x10 # Packet size
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movl %esp,%esi # Packet pointer
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decl %eax # Verify off
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orb $0x40,%ah # Use disk packet
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intx13.1: int $0x13 # BIOS: Disk I/O
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movl %edi,%esp # Restore
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popl %esi # Restore
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ret # To caller
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# Menu strings
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item: .ascii " "; .byte ' '|0x80
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prompt: .ascii "\nDefault:"; .byte ' '|0x80
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crlf: .ascii "\r"; .byte '\n'|0x80
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# Partition type tables
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tables:
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.byte 0x0, 0x5, 0xf
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.byte 0x1, 0x4, 0x6, 0xb, 0xc, 0xe, 0x63, 0x83
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.byte 0xa5, 0xa6
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.byte os_misc-. # Unknown
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.byte os_dos-. # DOS
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.byte os_dos-. # DOS
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.byte os_dos-. # DOS
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.byte os_dos-. # Windows
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.byte os_dos-. # Windows
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.byte os_dos-. # Windows
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.byte os_unix-. # UNIX
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.byte os_linux-. # Linux
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.byte os_freebsd-. # FreeBSD
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.byte os_bsd-. # OpenBSD
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os_misc: .ascii "?"; .byte '?'|0x80
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os_dos: .ascii "DO"; .byte 'S'|0x80
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os_unix: .ascii "UNI"; .byte 'X'|0x80
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os_linux: .ascii "Linu"; .byte 'x'|0x80
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os_freebsd: .ascii "Free"
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os_bsd: .ascii "BS"; .byte 'D'|0x80
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.org PRT_OFF-0xc,0x90
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drive: .ascii "Drive "
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nxtdrv: .byte 0x0 # Next drive number
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opt: .byte 0x0 # Option
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setdrv: .byte 0x80 # Drive to force
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flags: .byte FLAGS # Flags
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ticks: .word TICKS # Delay
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partbl: .fill 0x40,0x1,0x0 # Partition table
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.word MAGIC # Magic number
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