| 1 | # This code is no longer used in Etherboot. It is not maintained and
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| 2 | # may not work.
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| 3 |
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| 4 |
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| 5 | #
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| 6 | # Copyright (c) 1998 Robert Nordier
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| 7 | # All rights reserved.
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| 8 | # Very small bootrom changes by Luigi Rizzo
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| 9 | # <comment author="Luigi Rizzo">
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| 10 | # I recently had the problem of downloading the etherboot code
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| 11 | # from a hard disk partition instead of a floppy, and noticed that
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| 12 | # floppyload.S does not do the job. With a bit of hacking to
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| 13 | # the FreeBSD's boot1.s code, I managed to obtain a boot sector
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| 14 | # which works both for floppies and hard disks -- basically you
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| 15 | # do something like
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| 16 | #
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| 17 | # cat boot1a bin32/<yourcard>.lzrom > /dev/ad0s4
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| 18 | #
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| 19 | # (or whatever is the HD partition you are using, I am using slice
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| 20 | # 4 on FreeBSD) and you are up and running.
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| 21 | # Then with "fdisk" you have to mark your partition as having type "1"
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| 22 | # (which is listed as DOS-- but basically it must be something matching
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| 23 | # the variable PRT_BSD in the assembly source below).
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| 24 | # </comment>
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| 25 | #
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| 26 | # Redistribution and use in source and binary forms are freely
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| 27 | # permitted provided that the above copyright notice and this
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| 28 | # paragraph and the following disclaimer are duplicated in all
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| 29 | # such forms.
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| 30 | #
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| 31 | # This software is provided "AS IS" and without any express or
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| 32 | # implied warranties, including, without limitation, the implied
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| 33 | # warranties of merchantability and fitness for a particular
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| 34 | # purpose.
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| 35 | #
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| 36 | # Makefile:
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| 37 | #boot1a: boot1a.out
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| 38 | # objcopy -S -O binary boot1a.out boot1a
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| 39 | #
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| 40 | #boot1a.out: boot1a.o
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| 41 | # ld -nostdlib -static -N -e start -Ttext 0x7c00 -o boot1a.out boot1a.o
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| 42 | #
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| 43 | #boot1a.o: boot1a.s
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| 44 | # as --defsym FLAGS=0x80 boot1a.s -o boot1a.o
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| 45 | #
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| 46 | #
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| 47 |
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| 48 | # $FreeBSD: src/sys/boot/i386/boot2/boot1.s,v 1.10.2.2 2000/07/07 21:12:32 jhb Exp $
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| 49 |
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| 50 | # Memory Locations
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| 51 | .set MEM_REL,0x700 # Relocation address
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| 52 | .set MEM_ARG,0x900 # Arguments
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| 53 | .set MEM_ORG,0x7c00 # Origin
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| 54 | .set MEM_BUF,0x8c00 # Load area
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| 55 | .set MEM_BTX,0x9000 # BTX start
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| 56 | .set MEM_JMP,0x9010 # BTX entry point
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| 57 | .set MEM_USR,0xa000 # Client start
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| 58 | .set BDA_BOOT,0x472 # Boot howto flag
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| 59 |
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| 60 | # Partition Constants
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| 61 | .set PRT_OFF,0x1be # Partition offset
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| 62 | .set PRT_NUM,0x4 # Partitions
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| 63 | .set PRT_BSD,0x1 # Partition type
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| 64 |
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| 65 | # Flag Bits
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| 66 | .set FL_PACKET,0x80 # Packet mode
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| 67 |
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| 68 | # Misc. Constants
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| 69 | .set SIZ_PAG,0x1000 # Page size
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| 70 | .set SIZ_SEC,0x200 # Sector size
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| 71 |
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| 72 | .globl start
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| 73 | .globl xread
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| 74 | .code16
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| 75 |
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| 76 | start: jmp main # Start recognizably
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| 77 |
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| 78 | .org 0x4,0x90
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| 79 | #
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| 80 | # Trampoline used by boot2 to call read to read data from the disk via
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| 81 | # the BIOS. Call with:
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| 82 | #
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| 83 | # %cx:%ax - long - LBA to read in
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| 84 | # %es:(%bx) - caddr_t - buffer to read data into
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| 85 | # %dl - byte - drive to read from
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| 86 | # %dh - byte - num sectors to read
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| 87 | #
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| 88 |
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| 89 | xread: push %ss # Address
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| 90 | pop %ds # data
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| 91 | #
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| 92 | # Setup an EDD disk packet and pass it to read
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| 93 | #
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| 94 | xread.1: # Starting
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| 95 | pushl $0x0 # absolute
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| 96 | push %cx # block
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| 97 | push %ax # number
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| 98 | push %es # Address of
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| 99 | push %bx # transfer buffer
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| 100 | xor %ax,%ax # Number of
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| 101 | movb %dh,%al # blocks to
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| 102 | push %ax # transfer
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| 103 | push $0x10 # Size of packet
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| 104 | mov %sp,%bp # Packet pointer
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| 105 | callw read # Read from disk
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| 106 | lea 0x10(%bp),%sp # Clear stack
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| 107 | lret # To far caller
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| 108 | #
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| 109 | # Load the rest of boot2 and BTX up, copy the parts to the right locations,
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| 110 | # and start it all up.
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| 111 | #
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| 112 |
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| 113 | #
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| 114 | # Setup the segment registers to flat addressing (segment 0) and setup the
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| 115 | # stack to end just below the start of our code.
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| 116 | #
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| 117 | main: cld # String ops inc
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| 118 | xor %cx,%cx # Zero
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| 119 | mov %cx,%es # Address
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| 120 | mov %cx,%ds # data
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| 121 | mov %cx,%ss # Set up
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| 122 | mov $start,%sp # stack
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| 123 | #
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| 124 | # Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets
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| 125 | # %cx == 0x100.
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| 126 | #
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| 127 | mov %sp,%si # Source
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| 128 | mov $MEM_REL,%di # Destination
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| 129 | incb %ch # Word count
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| 130 | rep # Copy
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| 131 | movsw # code
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| 132 | #
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| 133 | # If we are on a hard drive, then load the MBR and look for the first
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| 134 | # FreeBSD slice. We use the fake partition entry below that points to
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| 135 | # the MBR when we call nread. The first pass looks for the first active
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| 136 | # FreeBSD slice. The second pass looks for the first non-active FreeBSD
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| 137 | # slice if the first one fails.
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| 138 | #
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| 139 | mov $part4,%si # Partition
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| 140 | cmpb $0x80,%dl # Hard drive?
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| 141 | jb main.4 # No
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| 142 | movb $0x1,%dh # Block count
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| 143 | callw nread # Read MBR
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| 144 | mov $0x1,%cx # Two passes
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| 145 | main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table
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| 146 | movb $0x1,%dh # Partition
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| 147 | main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type?
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| 148 | jne main.3 # No
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| 149 | jcxz main.5 # If second pass
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| 150 | testb $0x80,(%si) # Active?
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| 151 | jnz main.5 # Yes
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| 152 | main.3: add $0x10,%si # Next entry
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| 153 | incb %dh # Partition
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| 154 | cmpb $0x1+PRT_NUM,%dh # In table?
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| 155 | jb main.2 # Yes
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| 156 | dec %cx # Do two
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| 157 | jcxz main.1 # passes
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| 158 | #
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| 159 | # If we get here, we didn't find any FreeBSD slices at all, so print an
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| 160 | # error message and die.
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| 161 | #
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| 162 | booterror: mov $msg_part,%si # Message
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| 163 | jmp error # Error
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| 164 | #
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| 165 | # Floppies use partition 0 of drive 0.
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| 166 | #
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| 167 | main.4: xor %dx,%dx # Partition:drive
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| 168 | #
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| 169 | # Ok, we have a slice and drive in %dx now, so use that to locate and load
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| 170 | # boot2. %si references the start of the slice we are looking for, so go
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| 171 | # ahead and load up the first 16 sectors (boot1 + boot2) from that. When
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| 172 | # we read it in, we conveniently use 0x8c00 as our transfer buffer. Thus,
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| 173 | # boot1 ends up at 0x8c00, and boot2 starts at 0x8c00 + 0x200 = 0x8e00.
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| 174 | # The first part of boot2 is the disklabel, which is 0x200 bytes long.
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| 175 | # The second part is BTX, which is thus loaded into 0x9000, which is where
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| 176 | # it also runs from. The boot2.bin binary starts right after the end of
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| 177 | # BTX, so we have to figure out where the start of it is and then move the
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| 178 | # binary to 0xb000. Normally, BTX clients start at MEM_USR, or 0xa000, but
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| 179 | # when we use btxld create boot2, we use an entry point of 0x1000. That
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| 180 | # entry point is relative to MEM_USR; thus boot2.bin starts at 0xb000.
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| 181 | #
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| 182 | main.5: mov %dx,MEM_ARG # Save args
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| 183 | movb $0x2,%dh # Sector count
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| 184 | mov $0x7e00, %bx
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| 185 | callw nreadbx # Read disk
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| 186 | movb $0x40,%dh # Sector count
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| 187 | movb %dh, %al
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| 188 | callw puthex
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| 189 | mov $0x7e00, %bx
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| 190 | callw nreadbx # Read disk
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| 191 | push %si
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| 192 | mov $msg_r1,%si
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| 193 | callw putstr
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| 194 | pop %si
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| 195 | lcall $0x800,$0 # enter the rom code
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| 196 | int $0x19
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| 197 |
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| 198 | msg_r1: .asciz " done\r\n"
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| 199 |
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| 200 | .if 0
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| 201 | mov $MEM_BTX,%bx # BTX
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| 202 | mov 0xa(%bx),%si # Get BTX length and set
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| 203 | add %bx,%si # %si to start of boot2.bin
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| 204 | mov $MEM_USR+SIZ_PAG,%di # Client page 1
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| 205 | mov $MEM_BTX+0xe*SIZ_SEC,%cx # Byte
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| 206 | sub %si,%cx # count
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| 207 | rep # Relocate
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| 208 | movsb # client
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| 209 | sub %di,%cx # Byte count
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| 210 | xorb %al,%al # Zero assumed bss from
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| 211 | rep # the end of boot2.bin
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| 212 | stosb # up to 0x10000
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| 213 | callw seta20 # Enable A20
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| 214 | jmp start+MEM_JMP-MEM_ORG # Start BTX
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| 215 | #
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| 216 | # Enable A20 so we can access memory above 1 meg.
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| 217 | #
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| 218 | seta20: cli # Disable interrupts
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| 219 | seta20.1: inb $0x64,%al # Get status
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| 220 | testb $0x2,%al # Busy?
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| 221 | jnz seta20.1 # Yes
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| 222 | movb $0xd1,%al # Command: Write
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| 223 | outb %al,$0x64 # output port
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| 224 | seta20.2: inb $0x64,%al # Get status
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| 225 | testb $0x2,%al # Busy?
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| 226 | jnz seta20.2 # Yes
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| 227 | movb $0xdf,%al # Enable
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| 228 | outb %al,$0x60 # A20
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| 229 | sti # Enable interrupts
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| 230 | retw # To caller
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| 231 | .endif
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| 232 | #
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| 233 | # Trampoline used to call read from within boot1.
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| 234 | #
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| 235 | nread: mov $MEM_BUF,%bx # Transfer buffer
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| 236 | nreadbx: # same but address is in bx
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| 237 | mov 0x8(%si),%ax # Get
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| 238 | mov 0xa(%si),%cx # LBA
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| 239 | push %bx
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| 240 | push %ax
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| 241 | callw putword
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| 242 | pop %ax
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| 243 | pop %bx
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| 244 | push %cs # Read from
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| 245 | callw xread.1 # disk
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| 246 | jnc return # If success, return
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| 247 | mov $msg_read,%si # Otherwise, set the error
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| 248 | # message and fall through to
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| 249 | # the error routine
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| 250 | #
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| 251 | # Print out the error message pointed to by %ds:(%si) followed
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| 252 | # by a prompt, wait for a keypress, and then reboot the machine.
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| 253 | #
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| 254 | error: callw putstr # Display message
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| 255 | mov $prompt,%si # Display
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| 256 | callw putstr # prompt
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| 257 | xorb %ah,%ah # BIOS: Get
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| 258 | int $0x16 # keypress
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| 259 | movw $0x1234, BDA_BOOT # Do a warm boot
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| 260 | ljmp $0xffff,$0x0 # reboot the machine
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| 261 | #
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| 262 | # Display a null-terminated string using the BIOS output.
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| 263 | #
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| 264 | putstr.0: call putchar
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| 265 | putstr: lodsb # Get char
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| 266 | testb %al,%al # End of string?
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| 267 | jne putstr.0 # No
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| 268 | retw
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| 269 |
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| 270 | putword: push %ax
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| 271 | movb $'.', %al
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| 272 | callw putchar
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| 273 | movb %ah, %al
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| 274 | callw puthex
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| 275 | pop %ax
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| 276 | puthex: push %ax
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| 277 | shr $4, %al
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| 278 | callw putdigit
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| 279 | pop %ax
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| 280 | putdigit:
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| 281 | andb $0xf, %al
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| 282 | addb $0x30, %al
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| 283 | cmpb $0x39, %al
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| 284 | jbe putchar
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| 285 | addb $7, %al
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| 286 | putchar: push %ax
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| 287 | mov $0x7,%bx
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| 288 | movb $0xe,%ah
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| 289 | int $0x10
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| 290 | pop %ax
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| 291 | retw
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| 292 |
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| 293 | #
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| 294 | # Overused return code. ereturn is used to return an error from the
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| 295 | # read function. Since we assume putstr succeeds, we (ab)use the
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| 296 | # same code when we return from putstr.
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| 297 | #
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| 298 | ereturn: movb $0x1,%ah # Invalid
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| 299 | stc # argument
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| 300 | return: retw # To caller
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| 301 | #
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| 302 | # Reads sectors from the disk. If EDD is enabled, then check if it is
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| 303 | # installed and use it if it is. If it is not installed or not enabled, then
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| 304 | # fall back to using CHS. Since we use a LBA, if we are using CHS, we have to
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| 305 | # fetch the drive parameters from the BIOS and divide it out ourselves.
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| 306 | # Call with:
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| 307 | #
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| 308 | # %dl - byte - drive number
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| 309 | # stack - 10 bytes - EDD Packet
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| 310 | #
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| 311 | read: push %dx # Save
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| 312 | movb $0x8,%ah # BIOS: Get drive
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| 313 | int $0x13 # parameters
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| 314 | movb %dh,%ch # Max head number
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| 315 | pop %dx # Restore
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| 316 | jc return # If error
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| 317 | andb $0x3f,%cl # Sectors per track
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| 318 | jz ereturn # If zero
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| 319 | cli # Disable interrupts
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| 320 | mov 0x8(%bp),%eax # Get LBA
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| 321 | push %dx # Save
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| 322 | movzbl %cl,%ebx # Divide by
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| 323 | xor %edx,%edx # sectors
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| 324 | div %ebx # per track
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| 325 | movb %ch,%bl # Max head number
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| 326 | movb %dl,%ch # Sector number
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| 327 | inc %bx # Divide by
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| 328 | xorb %dl,%dl # number
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| 329 | div %ebx # of heads
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| 330 | movb %dl,%bh # Head number
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| 331 | pop %dx # Restore
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| 332 | cmpl $0x3ff,%eax # Cylinder number supportable?
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| 333 | sti # Enable interrupts
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| 334 | ja read.7 # No, try EDD
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| 335 | xchgb %al,%ah # Set up cylinder
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| 336 | rorb $0x2,%al # number
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| 337 | orb %ch,%al # Merge
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| 338 | inc %ax # sector
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| 339 | xchg %ax,%cx # number
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| 340 | movb %bh,%dh # Head number
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| 341 | subb %ah,%al # Sectors this track
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| 342 | mov 0x2(%bp),%ah # Blocks to read
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| 343 | cmpb %ah,%al # To read
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| 344 | jb read.2 # this
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| 345 | movb %ah,%al # track
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| 346 | read.2: mov $0x5,%di # Try count
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| 347 | read.3: les 0x4(%bp),%bx # Transfer buffer
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| 348 | push %ax # Save
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| 349 | movb $0x2,%ah # BIOS: Read
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| 350 | int $0x13 # from disk
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| 351 | pop %bx # Restore
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| 352 | jnc read.4 # If success
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| 353 | dec %di # Retry?
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| 354 | jz read.6 # No
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| 355 | xorb %ah,%ah # BIOS: Reset
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| 356 | int $0x13 # disk system
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| 357 | xchg %bx,%ax # Block count
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| 358 | jmp read.3 # Continue
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| 359 | read.4: movzbw %bl,%ax # Sectors read
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| 360 | add %ax,0x8(%bp) # Adjust
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| 361 | jnc read.5 # LBA,
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| 362 | incw 0xa(%bp) # transfer
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| 363 | read.5: shlb %bl # buffer
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| 364 | add %bl,0x5(%bp) # pointer,
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| 365 | sub %al,0x2(%bp) # block count
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| 366 | ja read # If not done
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| 367 | read.6: retw # To caller
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| 368 | read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start # LBA support enabled?
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| 369 | jz ereturn # No, so return an error
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| 370 | mov $0x55aa,%bx # Magic
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| 371 | push %dx # Save
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| 372 | movb $0x41,%ah # BIOS: Check
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| 373 | int $0x13 # extensions present
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| 374 | pop %dx # Restore
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| 375 | jc return # If error, return an error
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| 376 | cmp $0xaa55,%bx # Magic?
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| 377 | jne ereturn # No, so return an error
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| 378 | testb $0x1,%cl # Packet interface?
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| 379 | jz ereturn # No, so return an error
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| 380 | mov %bp,%si # Disk packet
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| 381 | movb $0x42,%ah # BIOS: Extended
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| 382 | int $0x13 # read
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| 383 | retw # To caller
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| 384 |
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| 385 | # Messages
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| 386 |
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| 387 | msg_read: .asciz "Rd"
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| 388 | msg_part: .asciz "Boot"
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| 389 |
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| 390 | prompt: .asciz " err\r\n"
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| 391 |
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| 392 | flags: .byte FLAGS # Flags
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| 393 |
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| 394 | .org PRT_OFF,0x90
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| 395 |
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| 396 | # Partition table
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|---|
| 397 |
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|---|
| 398 | .fill 0x30,0x1,0x0
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| 399 | part4: .byte 0x80
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|---|
| 400 | .byte 0x00 # start head
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|---|
| 401 | .byte 0x01 # start sector (6 bits) + start cyl (2 bit)
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|---|
| 402 | .byte 0x00 # start cyl (low 8 bits)
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|---|
| 403 | .byte 0x1 # part.type
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|---|
| 404 | .byte 0xff # end head
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|---|
| 405 | .byte 0xff # end sect (6) + end_cyl(2)
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|---|
| 406 | .byte 0xff # end cyl
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|---|
| 407 | .byte 0x00, 0x00, 0x00, 0x00 # explicit start
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|---|
| 408 | .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh
|
|---|
| 409 |
|
|---|
| 410 | .word 0xaa55 # Magic number
|
|---|
