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https://github.com/freebsd/freebsd-src
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c596126a5d
It would be nice to have larger boot partitions for ESPs to live in one day. It's trivial to carve out 5M 10M or 200M when provisioning, but logistical issues may make it hard to do it after the fact. So only warn when the partition is > 545k. If we ever grow the boot loader larger than that, then it will be responsible for loading the rest anyway. Sponsored by: Netflix Reviewed by: tsoome Differential Revision: https://reviews.freebsd.org/D42774
259 lines
7.9 KiB
ArmAsm
259 lines
7.9 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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#
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# Partly from: src/sys/boot/i386/mbr/mbr.s 1.7
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# A 512 byte PMBR boot manager that looks for a FreeBSD boot GPT partition
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# and boots it.
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.set LOAD,0x7c00 # Load address
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.set EXEC,0x600 # Execution address
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.set MAGIC,0xaa55 # Magic: bootable
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.set SECSIZE,0x200 # Size of a single disk sector
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.set DISKSIG,440 # Disk signature offset
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.set STACK,EXEC+SECSIZE*4 # Stack address
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.set GPT_ADDR,STACK # GPT header address
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.set GPT_SIG,0
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.set GPT_SIG_0,0x20494645 # "EFI "
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.set GPT_SIG_1,0x54524150 # "PART"
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.set GPT_MYLBA,24
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.set GPT_PART_LBA,72
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.set GPT_NPART,80
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.set GPT_PART_SIZE,84
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.set PART_ADDR,GPT_ADDR+SECSIZE # GPT partition array address
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.set PART_TYPE,0
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.set PART_START_LBA,32
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.set PART_END_LBA,40
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.set DPBUF,PART_ADDR+SECSIZE
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.set DPBUF_SEC,0x10 # Number of sectors
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.set NHRDRV,0x475 # Number of hard drives
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.globl start # Entry point
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.code16
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#
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# Setup the segment registers for flat addressing and setup the stack.
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#
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start: cld # String ops inc
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xorw %ax,%ax # Zero
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movw %ax,%es # Address
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movw %ax,%ds # data
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movw %ax,%ss # Set up
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movw $STACK,%sp # stack
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#
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# Relocate ourself to a lower address so that we have more room to load
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# other sectors.
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#
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movw $main-EXEC+LOAD,%si # Source
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movw $main,%di # Destination
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movw $SECSIZE-(main-start),%cx # Byte count
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rep # Relocate
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movsb # code
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#
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# Jump to the relocated code.
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#
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jmp main-LOAD+EXEC # To relocated code
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#
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# Validate drive number in %dl.
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#
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main: cmpb $0x80,%dl # Drive valid?
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jb main.1 # No
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movb NHRDRV,%dh # Calculate the highest
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addb $0x80,%dh # drive number available
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cmpb %dh,%dl # Within range?
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jb main.2 # Yes
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main.1: movb $0x80,%dl # Assume drive 0x80
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#
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# Load the GPT header and verify signature. Try LBA 1 for the primary one and
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# the last LBA for the backup if it is broken.
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#
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main.2: call getdrvparams # Read drive parameters
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movb $1,%dh # %dh := 1 (reading primary)
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main.2a: movw $GPT_ADDR,%bx
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movw $lba,%si
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call read # Read header and check GPT sig
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cmpl $GPT_SIG_0,GPT_ADDR+GPT_SIG
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jnz main.2b
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cmpl $GPT_SIG_1,GPT_ADDR+GPT_SIG+4
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jnz main.2b
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jmp load_part
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main.2b: cmpb $1,%dh # Reading primary?
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jne err_pt # If no - invalid table found
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#
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# Try alternative LBAs from the last sector for the GPT header.
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#
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main.3: movb $0,%dh # %dh := 0 (reading backup)
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movw $DPBUF+DPBUF_SEC,%si # %si = last sector + 1
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movw $lba,%di # %di = $lba
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main.3a: subl $1, (%si) # 0x0(%si) = last sec (0-31)
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sbbl $0, 4(%si)
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movw $4,%cx
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rep
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movsw # $lastsec--, copy it to $lba
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jmp main.2a # Read the next sector
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#
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# Load a partition table sector from disk and look for a FreeBSD boot
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# partition.
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#
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load_part: movw $GPT_ADDR+GPT_PART_LBA,%si
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movw $PART_ADDR,%bx
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call read
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scan: movw %bx,%si # Compare partition UUID
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movw $boot_uuid,%di # with FreeBSD boot UUID
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movw $0x10,%cx
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repe cmpsb
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jnz next_part # Didn't match, next partition
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#
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# We found a boot partition. Load it into RAM starting at 0x7c00.
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#
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movw %bx,%di # Save partition pointer in %di
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leaw PART_START_LBA(%di),%si
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movw $LOAD/16,%bx
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movw %bx,%es
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xorw %bx,%bx
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load_boot: push %si # Save %si
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call read
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pop %si # Restore
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movl PART_END_LBA(%di),%eax # See if this was the last LBA
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cmpl (%si),%eax
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jnz next_boot
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movl PART_END_LBA+4(%di),%eax
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cmpl 4(%si),%eax
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jnz next_boot
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mov %bx,%es # Reset %es to zero
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jmp LOAD # Jump to boot code
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next_boot: addl $1,(%si) # Next LBA
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adcl $0,4(%si)
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mov %es,%ax # Adjust segment for next
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addw $SECSIZE/16,%ax # sector
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cmp $0x9000,%ax # Don't load past 0x90000,
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jb sz_ok # 545k should be enough for
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call err_big # any boot code, but warn
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mov $0x9000-SECSIZE/16,%ax # and truncate
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sz_ok: mov %ax,%es
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jmp load_boot
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#
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# Move to the next partition. If we walk off the end of the sector, load
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# the next sector. We assume that partition entries are smaller than 64k
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# and that they won't span a sector boundary.
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#
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# XXX: Should we int 0x18 instead of err_noboot if we hit the end of the table?
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#
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next_part: decl GPT_ADDR+GPT_NPART # Was this the last partition?
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jz err_noboot
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movw GPT_ADDR+GPT_PART_SIZE,%ax
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addw %ax,%bx # Next partition
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cmpw $PART_ADDR+0x200,%bx # Still in sector?
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jb scan
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addl $1, GPT_ADDR+GPT_PART_LBA # Next sector
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adcl $0,GPT_ADDR+GPT_PART_LBA+4
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jmp load_part
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#
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# Load a sector (64-bit LBA at %si) from disk %dl into %es:%bx by creating
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# a EDD packet on the stack and passing it to the BIOS. Trashes %ax and %si.
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#
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read: pushl 0x4(%si) # Set the LBA
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pushl 0x0(%si) # address
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pushw %es # Set the address of
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pushw %bx # the transfer buffer
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pushw $0x1 # Read 1 sector
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pushw $0x10 # Packet length
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movw %sp,%si # Packer pointer
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movw $0x4200,%ax # BIOS: LBA Read from disk
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int $0x13 # Call the BIOS
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add $0x10,%sp # Restore stack
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jc err_rd # If error
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ret
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#
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# Check the number of LBAs on the drive index %dx. Trashes %ax and %si.
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#
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getdrvparams:
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movw $DPBUF,%si # Set the address of result buf
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movw $0x001e,(%si) # len
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movw $0x4800,%ax # BIOS: Read Drive Parameters
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int $0x13 # Call the BIOS
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jc err_rd # "I/O error" if error
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ret
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#
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# Various error message entry points.
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#
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err_big: movw $msg_big,%si # "Truncated
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call putstr # to 545k"
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ret
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err_pt: movw $msg_pt,%si # "Invalid partition
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call putstr # table"
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err_pt.1: jmp err_pt.1 # Await reset
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err_rd: movw $msg_rd,%si # "I/O error loading
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call putstr # boot loader"
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jmp err_pt.1
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err_noboot: movw $msg_noboot,%si # "Missing boot
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call putstr # loader"
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jmp err_pt.1
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#
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# Output an ASCIZ string to the console via the BIOS.
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#
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putstr.0: movw $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 character
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testb %al,%al # End of string?
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jnz putstr.0 # No
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ret
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msg_big: .asciz "Loaded only 545k"
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msg_pt: .asciz "Invalid partition table"
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msg_rd: .asciz "I/O error loading boot loader"
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msg_noboot: .asciz "Missing boot loader"
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lba: .quad 1 # LBA of GPT header
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boot_uuid: .long 0x83bd6b9d
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.word 0x7f41
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.word 0x11dc
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.byte 0xbe
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.byte 0x0b
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.byte 0x00
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.byte 0x15
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.byte 0x60
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.byte 0xb8
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.byte 0x4f
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.byte 0x0f
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.org DISKSIG,0x90
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sig: .long 0 # OS Disk Signature
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.word 0 # "Unknown" in PMBR
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partbl: .fill 0x10,0x4,0x0 # Partition table
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.word MAGIC # Magic number
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