601 lines
18 KiB
ArmAsm
601 lines
18 KiB
ArmAsm
#
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# Copyright (c) 2001 John Baldwin <jhb@FreeBSD.org>
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# All rights reserved.
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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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# This program is a freestanding boot program to load an a.out binary
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# from a CD-ROM booted with no emulation mode as described by the El
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# Torito standard. Due to broken BIOSen that do not load the desired
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# number of sectors, we try to fit this in as small a space as possible.
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#
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# Basically, we first create a set of boot arguments to pass to the loaded
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# binary. Then we attempt to load /boot/loader from the CD we were booted
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# off of.
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#
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#
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# Memory locations.
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#
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.set MEM_PAGE_SIZE,0x1000 # memory page size, 4k
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.set MEM_ARG,0x900 # Arguments at start
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.set MEM_ARG_BTX,0xa100 # Where we move them to so the
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# BTX client can see them
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.set MEM_ARG_SIZE,0x18 # Size of the arguments
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.set MEM_BTX_ADDRESS,0x9000 # where BTX lives
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.set MEM_BTX_ENTRY,0x9010 # where BTX starts to execute
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.set MEM_BTX_OFFSET,MEM_PAGE_SIZE # offset of BTX in the loader
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.set MEM_BTX_CLIENT,0xa000 # where BTX clients live
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#
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# a.out header fields
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#
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.set AOUT_TEXT,0x04 # text segment size
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.set AOUT_DATA,0x08 # data segment size
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.set AOUT_BSS,0x0c # zero'd BSS size
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.set AOUT_SYMBOLS,0x10 # symbol table
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.set AOUT_ENTRY,0x14 # entry point
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.set AOUT_HEADER,MEM_PAGE_SIZE # size of the a.out header
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#
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# Flags for kargs->bootflags
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#
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.set KARGS_FLAGS_CD,0x1 # flag to indicate booting from
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# CD loader
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#
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# Segment selectors.
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#
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.set SEL_SDATA,0x8 # Supervisor data
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.set SEL_RDATA,0x10 # Real mode data
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.set SEL_SCODE,0x18 # PM-32 code
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.set SEL_SCODE16,0x20 # PM-16 code
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#
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# BTX constants
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#
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.set INT_SYS,0x30 # BTX syscall interrupt
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#
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# Constants for reading from the CD.
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#
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.set ERROR_TIMEOUT,0x80 # BIOS timeout on read
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.set NUM_RETRIES,3 # Num times to retry
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.set SECTOR_SIZE,0x800 # size of a sector
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.set SECTOR_SHIFT,11 # number of place to shift
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.set BUFFER_LEN,0x100 # number of sectors in buffer
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.set MAX_READ,0x10000 # max we can read at a time
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.set MAX_READ_SEC,MAX_READ >> SECTOR_SHIFT
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.set MEM_READ_BUFFER,0x9000 # buffer to read from CD
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.set MEM_VOLDESC,MEM_READ_BUFFER # volume descriptor
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.set MEM_DIR,MEM_VOLDESC+SECTOR_SIZE # Lookup buffer
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.set VOLDESC_LBA,0x10 # LBA of vol descriptor
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.set VD_PRIMARY,1 # Primary VD
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.set VD_END,255 # VD Terminator
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.set VD_ROOTDIR,156 # Offset of Root Dir Record
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.set DIR_LEN,0 # Offset of Dir Record length
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.set DIR_EA_LEN,1 # Offset of EA length
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.set DIR_EXTENT,2 # Offset of 64-bit LBA
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.set DIR_SIZE,10 # Offset of 64-bit length
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.set DIR_NAMELEN,32 # Offset of 8-bit name len
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.set DIR_NAME,33 # Offset of dir name
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#
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# We expect to be loaded by the BIOS at 0x7c00 (standard boot loader entry
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# point)
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#
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.code16
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.globl start
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.org 0x0, 0x0
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#
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# Program start.
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#
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start: cld # string ops inc
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xor %ax,%ax # zero %ax
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mov %ax,%ss # setup the
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mov $start,%sp # stack
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mov %ax,%ds # setup the
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mov %ax,%es # data segments
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mov %dl,drive # Save BIOS boot device
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mov $msg_welcome,%si # %ds:(%si) -> welcome message
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call putstr # display the welcome message
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#
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# Setup the arguments that the loader is expecting from boot[12]
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#
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mov $msg_bootinfo,%si # %ds:(%si) -> boot args message
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call putstr # display the message
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mov $MEM_ARG,%bx # %ds:(%bx) -> boot args
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mov %bx,%di # %es:(%di) -> boot args
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xor %eax,%eax # zero %eax
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mov $(MEM_ARG_SIZE/4),%cx # Size of arguments in 32-bit
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# dwords
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rep # Clear the arguments
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stosl # to zero
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mov drive,%dl # Store BIOS boot device
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mov %dl,0x4(%bx) # in kargs->bootdev
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or $KARGS_FLAGS_CD,0x8(%bx) # kargs->bootflags |=
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# KARGS_FLAGS_CD
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#
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# Load Volume Descriptor
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#
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mov $VOLDESC_LBA,%eax # Set LBA of first VD
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load_vd: push %eax # Save %eax
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mov $1,%dh # One sector
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mov $MEM_VOLDESC,%ebx # Destination
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call read # Read it in
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cmpb $VD_PRIMARY,(%bx) # Primary VD?
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je have_vd # Yes
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pop %eax # Prepare to
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inc %eax # try next
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cmpb $VD_END,(%bx) # Last VD?
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jne load_vd # No, read next
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mov $msg_novd,%si # No VD
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jmp error # Halt
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have_vd: # Have Primary VD
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#
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# Try to look up the loader binary using the paths in the loader_paths
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# array.
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#
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mov $loader_paths,%si # Point to start of array
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lookup_path: push %si # Save file name pointer
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call lookup # Try to find file
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pop %di # Restore file name pointer
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jnc lookup_found # Found this file
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xor %al,%al # Look for next
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mov $0xffff,%cx # path name by
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repnz # scanning for
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scasb # nul char
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mov %di,%si # Point %si at next path
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mov (%si),%al # Get first char of next path
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or %al,%al # Is it double nul?
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jnz lookup_path # No, try it.
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mov $msg_failed,%si # Failed message
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jmp error # Halt
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lookup_found: # Found a loader file
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#
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# Load the binary into the buffer. Due to real mode addressing limitations
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# we have to read it in 64k chunks.
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#
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mov DIR_SIZE(%bx),%eax # Read file length
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add $SECTOR_SIZE-1,%eax # Convert length to sectors
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shr $SECTOR_SHIFT,%eax
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cmp $BUFFER_LEN,%eax
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jbe load_sizeok
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mov $msg_load2big,%si # Error message
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call error
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load_sizeok: movzbw %al,%cx # Num sectors to read
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mov DIR_EXTENT(%bx),%eax # Load extent
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xor %edx,%edx
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mov DIR_EA_LEN(%bx),%dl
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add %edx,%eax # Skip extended
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mov $MEM_READ_BUFFER,%ebx # Read into the buffer
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load_loop: mov %cl,%dh
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cmp $MAX_READ_SEC,%cl # Truncate to max read size
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jbe load_notrunc
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mov $MAX_READ_SEC,%dh
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load_notrunc: sub %dh,%cl # Update count
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push %eax # Save
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call read # Read it in
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pop %eax # Restore
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add $MAX_READ_SEC,%eax # Update LBA
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add $MAX_READ,%ebx # Update dest addr
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jcxz load_done # Done?
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jmp load_loop # Keep going
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load_done:
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#
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# Turn on the A20 address line
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#
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call seta20 # Turn A20 on
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#
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# Relocate the loader and BTX using a very lazy protected mode
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#
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mov $msg_relocate,%si # Display the
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call putstr # relocation message
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mov MEM_READ_BUFFER+AOUT_ENTRY,%edi # %edi is the destination
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mov $(MEM_READ_BUFFER+AOUT_HEADER),%esi # %esi is
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# the start of the text
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# segment
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mov MEM_READ_BUFFER+AOUT_TEXT,%ecx # %ecx = length of the text
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# segment
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push %edi # Save entry point for later
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lgdt gdtdesc # setup our own gdt
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cli # turn off interrupts
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mov %cr0,%eax # Turn on
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or $0x1,%al # protected
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mov %eax,%cr0 # mode
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ljmp $SEL_SCODE,$pm_start # long jump to clear the
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# instruction pre-fetch queue
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.code32
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pm_start: mov $SEL_SDATA,%ax # Initialize
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mov %ax,%ds # %ds and
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mov %ax,%es # %es to a flat selector
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rep # Relocate the
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movsb # text segment
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add $(MEM_PAGE_SIZE - 1),%edi # pad %edi out to a new page
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and $~(MEM_PAGE_SIZE - 1),%edi # for the data segment
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mov MEM_READ_BUFFER+AOUT_DATA,%ecx # size of the data segment
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rep # Relocate the
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movsb # data segment
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mov MEM_READ_BUFFER+AOUT_BSS,%ecx # size of the bss
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xor %eax,%eax # zero %eax
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add $3,%cl # round %ecx up to
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shr $2,%ecx # a multiple of 4
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rep # zero the
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stosl # bss
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mov MEM_READ_BUFFER+AOUT_ENTRY,%esi # %esi -> relocated loader
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add $MEM_BTX_OFFSET,%esi # %esi -> BTX in the loader
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mov $MEM_BTX_ADDRESS,%edi # %edi -> where BTX needs to go
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movzwl 0xa(%esi),%ecx # %ecx -> length of BTX
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rep # Relocate
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movsb # BTX
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ljmp $SEL_SCODE16,$pm_16 # Jump to 16-bit PM
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.code16
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pm_16: mov $SEL_RDATA,%ax # Initialize
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mov %ax,%ds # %ds and
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mov %ax,%es # %es to a real mode selector
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mov %cr0,%eax # Turn off
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and $~0x1,%al # protected
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mov %eax,%cr0 # mode
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ljmp $0,$pm_end # Long jump to clear the
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# instruction pre-fetch queue
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pm_end: sti # Turn interrupts back on now
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#
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# Copy the BTX client to MEM_BTX_CLIENT
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#
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xor %ax,%ax # zero %ax and set
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mov %ax,%ds # %ds and %es
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mov %ax,%es # to segment 0
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mov $MEM_BTX_CLIENT,%di # Prepare to relocate
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mov $btx_client,%si # the simple btx client
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mov $(btx_client_end-btx_client),%cx # length of btx client
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rep # Relocate the
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movsb # simple BTX client
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#
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# Copy the boot[12] args to where the BTX client can see them
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#
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mov $MEM_ARG,%si # where the args are at now
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mov $MEM_ARG_BTX,%di # where the args are moving to
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mov $(MEM_ARG_SIZE/4),%cx # size of the arguments in longs
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rep # Relocate
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movsl # the words
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#
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# Save the entry point so the client can get to it later on
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#
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pop %eax # Restore saved entry point
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stosl # and add it to the end of
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# the arguments
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#
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# Now we just start up BTX and let it do the rest
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#
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mov $msg_jump,%si # Display the
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call putstr # jump message
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ljmp $0,$MEM_BTX_ENTRY # Jump to the BTX entry point
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#
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# Lookup the file in the path at [SI] from the root directory.
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#
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# Trashes: All but BX
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# Returns: CF = 0 (success), BX = pointer to record
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# CF = 1 (not found)
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#
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lookup: mov $VD_ROOTDIR+MEM_VOLDESC,%bx # Root directory record
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push %si
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mov $msg_lookup,%si # Display lookup message
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call putstr
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pop %si
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push %si
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call putstr
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mov $msg_lookup2,%si
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call putstr
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pop %si
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lookup_dir: lodsb # Get first char of path
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cmp $0,%al # Are we done?
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je lookup_done # Yes
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cmp $'/',%al # Skip path separator.
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je lookup_dir
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dec %si # Undo lodsb side effect
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call find_file # Lookup first path item
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jnc lookup_dir # Try next component
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mov $msg_lookupfail,%si # Not found message
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call putstr
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stc # Set carry
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ret
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jmp error
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lookup_done: mov $msg_lookupok,%si # Success message
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call putstr
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clc # Clear carry
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ret
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#
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# Lookup file at [SI] in directory whose record is at [BX].
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#
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# Trashes: All but returns
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# Returns: CF = 0 (success), BX = pointer to record, SI = next path item
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# CF = 1 (not found), SI = preserved
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#
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find_file: mov DIR_EXTENT(%bx),%eax # Load extent
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xor %edx,%edx
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mov DIR_EA_LEN(%bx),%dl
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add %edx,%eax # Skip extended attributes
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mov %eax,rec_lba # Save LBA
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mov DIR_SIZE(%bx),%eax # Save size
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mov %eax,rec_size
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xor %cl,%cl # Zero length
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push %si # Save
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ff.namelen: inc %cl # Update length
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lodsb # Read char
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cmp $0,%al # Nul?
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je ff.namedone # Yes
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cmp $'/',%al # Path separator?
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jnz ff.namelen # No, keep going
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ff.namedone: dec %cl # Adjust length and save
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mov %cl,name_len
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pop %si # Restore
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ff.load: mov rec_lba,%eax # Load LBA
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mov $MEM_DIR,%ebx # Address buffer
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mov $1,%dh # One sector
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call read # Read directory block
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incl rec_lba # Update LBA to next block
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ff.scan: mov %ebx,%edx # Check for EOF
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sub $MEM_DIR,%edx
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cmp %edx,rec_size
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ja ff.scan.1
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stc # EOF reached
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ret
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ff.scan.1: cmpb $0,DIR_LEN(%bx) # Last record in block?
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je ff.nextblock
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push %si # Save
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movzbw DIR_NAMELEN(%bx),%si # Find end of string
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ff.checkver: cmpb $'0',DIR_NAME-1(%bx,%si) # Less than '0'?
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jb ff.checkver.1
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cmpb $'9',DIR_NAME-1(%bx,%si) # Greater than '9'?
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ja ff.checkver.1
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dec %si # Next char
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jnz ff.checkver
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jmp ff.checklen # All numbers in name, so
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# no version
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ff.checkver.1: movzbw DIR_NAMELEN(%bx),%cx
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cmp %cx,%si # Did we find any digits?
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je ff.checkdot # No
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cmpb $';',DIR_NAME-1(%bx,%si) # Check for semicolon
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jne ff.checkver.2
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dec %si # Skip semicolon
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mov %si,%cx
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mov %cl,DIR_NAMELEN(%bx) # Adjust length
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jmp ff.checkdot
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ff.checkver.2: mov %cx,%si # Restore %si to end of string
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ff.checkdot: cmpb $'.',DIR_NAME-1(%bx,%si) # Trailing dot?
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jne ff.checklen # No
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decb DIR_NAMELEN(%bx) # Adjust length
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ff.checklen: pop %si # Restore
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movzbw name_len,%cx # Load length of name
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cmp %cl,DIR_NAMELEN(%bx) # Does length match?
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je ff.checkname # Yes, check name
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ff.nextrec: add DIR_LEN(%bx),%bl # Next record
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adc $0,%bh
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jmp ff.scan
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ff.nextblock: subl $SECTOR_SIZE,rec_size # Adjust size
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jnc ff.load # If subtract ok, keep going
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ret # End of file, so not found
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ff.checkname: lea DIR_NAME(%bx),%di # Address name in record
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push %si # Save
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repe cmpsb # Compare name
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je ff.match # We have a winner!
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pop %si # Restore
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jmp ff.nextrec # Keep looking.
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ff.match: add $2,%sp # Discard saved %si
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clc # Clear carry
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ret
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#
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# Load DH sectors starting at LBA EAX into [EBX].
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#
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# Trashes: EAX
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#
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read: push %si # Save
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push %cx # Save since some BIOSs trash
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mov %eax,edd_lba # LBA to read from
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mov %ebx,%eax # Convert address
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shr $4,%eax # to segment
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mov %ax,edd_addr+0x2 # and store
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read.retry: call twiddle # Entertain the user
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push %dx # Save
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mov $edd_packet,%si # Address Packet
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mov %dh,edd_len # Set length
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mov drive,%dl # BIOS Device
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mov $0x42,%ah # BIOS: Extended Read
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int $0x13 # Call BIOS
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pop %dx # Restore
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jc read.fail # Worked?
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pop %cx # Restore
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pop %si
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ret # Return
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read.fail: cmp $ERROR_TIMEOUT,%ah # Timeout?
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je read.retry # Yes, Retry.
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read.error: mov %ah,%al # Save error
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mov $hex_error,%di # Format it
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call hex8 # as hex
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mov $msg_badread,%si # Display Read error message
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#
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# Display error message at [SI] and halt.
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#
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error: call putstr # Display message
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halt: hlt
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jmp halt # Spin
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#
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# Display a null-terminated string.
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#
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# Trashes: AX, SI
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#
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putstr: push %bx # Save
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putstr.load: lodsb # load %al from %ds:(%si)
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test %al,%al # stop at null
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jnz putstr.putc # if the char != null, output it
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pop %bx # Restore
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ret # return when null is hit
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putstr.putc: call putc # output char
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jmp putstr.load # next char
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#
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# Display a single char.
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#
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putc: mov $0x7,%bx # attribute for output
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mov $0xe,%ah # BIOS: put_char
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int $0x10 # call BIOS, print char in %al
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ret # Return to caller
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|
|
|
#
|
|
# Output the "twiddle"
|
|
#
|
|
twiddle: push %ax # Save
|
|
push %bx # Save
|
|
mov twiddle_index,%al # Load index
|
|
mov $twiddle_chars,%bx # Address table
|
|
inc %al # Next
|
|
and $3,%al # char
|
|
mov %al,twiddle_index # Save index for next call
|
|
xlat # Get char
|
|
call putc # Output it
|
|
mov $8,%al # Backspace
|
|
call putc # Output it
|
|
pop %bx # Restore
|
|
pop %ax # Restore
|
|
ret
|
|
|
|
#
|
|
# Enable A20. Put an upper limit on the amount of time we wait for the
|
|
# keyboard controller to get ready (65K x ISA access time). If
|
|
# we wait more than that amount, the hardware is probably
|
|
# legacy-free and simply doesn't have a keyboard controller.
|
|
# Thus, the A20 line is already enabled.
|
|
#
|
|
seta20: cli # Disable interrupts
|
|
xor %cx,%cx # Clear
|
|
seta20.1: inc %cx # Increment, overflow?
|
|
jz seta20.3 # Yes
|
|
in $0x64,%al # Get status
|
|
test $0x2,%al # Busy?
|
|
jnz seta20.1 # Yes
|
|
mov $0xd1,%al # Command: Write
|
|
out %al,$0x64 # output port
|
|
seta20.2: in $0x64,%al # Get status
|
|
test $0x2,%al # Busy?
|
|
jnz seta20.2 # Yes
|
|
mov $0xdf,%al # Enable
|
|
out %al,$0x60 # A20
|
|
seta20.3: sti # Enable interrupts
|
|
ret # To caller
|
|
|
|
#
|
|
# Convert AL to hex, saving the result to [EDI].
|
|
#
|
|
hex8: pushl %eax # Save
|
|
shrb $0x4,%al # Do upper
|
|
call hex8.1 # 4
|
|
popl %eax # Restore
|
|
hex8.1: andb $0xf,%al # Get lower 4
|
|
cmpb $0xa,%al # Convert
|
|
sbbb $0x69,%al # to hex
|
|
das # digit
|
|
orb $0x20,%al # To lower case
|
|
stosb # Save char
|
|
ret # (Recursive)
|
|
|
|
#
|
|
# BTX client to start btxldr
|
|
#
|
|
.code32
|
|
btx_client: mov $(MEM_ARG_BTX-MEM_BTX_CLIENT+MEM_ARG_SIZE-4), %esi
|
|
# %ds:(%esi) -> end
|
|
# of boot[12] args
|
|
mov $(MEM_ARG_SIZE/4),%ecx # Number of words to push
|
|
std # Go backwards
|
|
push_arg: lodsl # Read argument
|
|
push %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
|
|
push %eax # Emulate a near call
|
|
mov $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
|
|
#
|
|
# EDD Packet
|
|
#
|
|
edd_packet: .byte 0x10 # Length
|
|
.byte 0 # Reserved
|
|
edd_len: .byte 0x0 # Num to read
|
|
.byte 0 # Reserved
|
|
edd_addr: .word 0x0,0x0 # Seg:Off
|
|
edd_lba: .quad 0x0 # LBA
|
|
|
|
drive: .byte 0
|
|
|
|
#
|
|
# State for searching dir
|
|
#
|
|
rec_lba: .long 0x0 # LBA (adjusted for EA)
|
|
rec_size: .long 0x0 # File size
|
|
name_len: .byte 0x0 # Length of current name
|
|
|
|
twiddle_index: .byte 0x0
|
|
|
|
msg_welcome: .asciz "CD Loader 1.2\r\n\n"
|
|
msg_bootinfo: .asciz "Building the boot loader arguments\r\n"
|
|
msg_relocate: .asciz "Relocating the loader and the BTX\r\n"
|
|
msg_jump: .asciz "Starting the BTX loader\r\n"
|
|
msg_badread: .ascii "Read Error: 0x"
|
|
hex_error: .asciz "00\r\n"
|
|
msg_novd: .asciz "Could not find Primary Volume Descriptor\r\n"
|
|
msg_lookup: .asciz "Looking up "
|
|
msg_lookup2: .asciz "... "
|
|
msg_lookupok: .asciz "Found\r\n"
|
|
msg_lookupfail: .asciz "File not found\r\n"
|
|
msg_load2big: .asciz "File too big\r\n"
|
|
msg_failed: .asciz "Boot failed\r\n"
|
|
twiddle_chars: .ascii "|/-\\"
|
|
loader_paths: .asciz "/BOOT/LOADER"
|
|
.asciz "/boot/loader"
|
|
.byte 0
|
|
|