1*22028508SToomas Soome#- 2*22028508SToomas Soome# Copyright (c) 2007 Yahoo!, Inc. 3*22028508SToomas Soome# All rights reserved. 4*22028508SToomas Soome# Written by: John Baldwin <jhb@FreeBSD.org> 5*22028508SToomas Soome# 6*22028508SToomas Soome# Redistribution and use in source and binary forms, with or without 7*22028508SToomas Soome# modification, are permitted provided that the following conditions 8*22028508SToomas Soome# are met: 9*22028508SToomas Soome# 1. Redistributions of source code must retain the above copyright 10*22028508SToomas Soome# notice, this list of conditions and the following disclaimer. 11*22028508SToomas Soome# 2. Redistributions in binary form must reproduce the above copyright 12*22028508SToomas Soome# notice, this list of conditions and the following disclaimer in the 13*22028508SToomas Soome# documentation and/or other materials provided with the distribution. 14*22028508SToomas Soome# 3. Neither the name of the author nor the names of any co-contributors 15*22028508SToomas Soome# may be used to endorse or promote products derived from this software 16*22028508SToomas Soome# without specific prior written permission. 17*22028508SToomas Soome# 18*22028508SToomas Soome# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19*22028508SToomas Soome# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20*22028508SToomas Soome# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21*22028508SToomas Soome# ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22*22028508SToomas Soome# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23*22028508SToomas Soome# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24*22028508SToomas Soome# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25*22028508SToomas Soome# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26*22028508SToomas Soome# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27*22028508SToomas Soome# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28*22028508SToomas Soome# SUCH DAMAGE. 29*22028508SToomas Soome# 30*22028508SToomas Soome# $FreeBSD$ 31*22028508SToomas Soome# 32*22028508SToomas Soome# Partly from: src/sys/boot/i386/mbr/mbr.s 1.7 33*22028508SToomas Soome 34*22028508SToomas Soome# A 512 byte PMBR boot manager to read a boot program and run it. 35*22028508SToomas Soome# The embedded MBR is set up for PMBR and default bootblock sector 36*22028508SToomas Soome# is hardcoded to 256 and size 1. The actual values are supposed to be 37*22028508SToomas Soome# updated by installboot. 38*22028508SToomas Soome 39*22028508SToomas Soome .set LOAD,0x7c00 # Load address 40*22028508SToomas Soome .set EXEC,0x600 # Execution address 41*22028508SToomas Soome .set MAGIC,0xaa55 # Magic: bootable 42*22028508SToomas Soome .set SECSIZE,0x200 # Size of a single disk sector 43*22028508SToomas Soome .set DISKSIG,440 # Disk signature offset 44*22028508SToomas Soome .set STACK,EXEC+SECSIZE*4 # Stack address 45*22028508SToomas Soome .set DPBUF,STACK 46*22028508SToomas Soome 47*22028508SToomas Soome .set NHRDRV,0x475 # Number of hard drives 48*22028508SToomas Soome 49*22028508SToomas Soome .globl start # Entry point 50*22028508SToomas Soome .code16 51*22028508SToomas Soome .text 52*22028508SToomas Soome 53*22028508SToomas Soomestart: jmp real_code 54*22028508SToomas Soome .fill 0x3c,0x1,0x90 # fill with nop to ease disasm 55*22028508SToomas Soome# 56*22028508SToomas Soome# BIOS Parameter Block. Reserved space from 0xb to 0x3e, the FAT32 BPB 57*22028508SToomas Soome# is 60 (3Ch) bytes. 58*22028508SToomas Soome# 59*22028508SToomas Soome . = start + 0x3e 60*22028508SToomas Soome 61*22028508SToomas Soome# 62*22028508SToomas Soome# Setup the segment registers for flat addressing and setup the stack. 63*22028508SToomas Soome# 64*22028508SToomas Soomereal_code: cld # String ops inc 65*22028508SToomas Soome xorw %ax,%ax # Zero 66*22028508SToomas Soome movw %ax,%es # Address 67*22028508SToomas Soome movw %ax,%ds # data 68*22028508SToomas Soome movw %ax,%ss # Set up 69*22028508SToomas Soome movw $STACK,%sp # stack 70*22028508SToomas Soome# 71*22028508SToomas Soome# Relocate ourself to a lower address so that we have more room to load 72*22028508SToomas Soome# other sectors. 73*22028508SToomas Soome# 74*22028508SToomas Soome movw $main-EXEC+LOAD,%si # Source 75*22028508SToomas Soome movw $main,%di # Destination 76*22028508SToomas Soome movw $SECSIZE-(main-start),%cx # Byte count 77*22028508SToomas Soome rep # Relocate 78*22028508SToomas Soome movsb # code 79*22028508SToomas Soome# 80*22028508SToomas Soome# Jump to the relocated code. 81*22028508SToomas Soome# 82*22028508SToomas Soome jmp main-LOAD+EXEC # To relocated code 83*22028508SToomas Soome# 84*22028508SToomas Soome# Validate drive number in %dl. 85*22028508SToomas Soome# 86*22028508SToomas Soomemain: cmpb $0x80,%dl # Drive valid? 87*22028508SToomas Soome jb main.1 # No 88*22028508SToomas Soome movb NHRDRV,%dh # Calculate the highest 89*22028508SToomas Soome addb $0x80,%dh # drive number available 90*22028508SToomas Soome cmpb %dh,%dl # Within range? 91*22028508SToomas Soome jb main.2 # Yes 92*22028508SToomas Soomemain.1: movb $0x80,%dl # Assume drive 0x80 93*22028508SToomas Soome# 94*22028508SToomas Soome# Load stage2 and start it. location and size is written by installboot 95*22028508SToomas Soome# and if size is 0, we can not do anything... 96*22028508SToomas Soome# 97*22028508SToomas Soomemain.2: movw stage2_size, %ax 98*22028508SToomas Soome cmpw $0, %ax 99*22028508SToomas Soome je err_noboot # the stage2 size is not set 100*22028508SToomas Soome pushw %dx # save drive 101*22028508SToomas Soome movb $0x41, %ah # check extensions 102*22028508SToomas Soome movw $0x55aa, %bx 103*22028508SToomas Soome int $0x13 104*22028508SToomas Soome popw %dx # restore drive 105*22028508SToomas Soome jc err_rd # need lba mode for now 106*22028508SToomas Soome cmpw $0xaa55, %bx # chs support is not 107*22028508SToomas Soome jne err_rd # implemented. 108*22028508SToomas Soome movw $stage2_sector, %si # pointer to lba 109*22028508SToomas Soome movw $LOAD/16,%bx # set buffer segment 110*22028508SToomas Soome movw %bx,%es 111*22028508SToomas Soome xorw %bx,%bx # and offset 112*22028508SToomas Soomeload_boot: push %si # Save %si 113*22028508SToomas Soome call read 114*22028508SToomas Soome pop %si # Restore 115*22028508SToomas Soome decw stage2_size # stage2_size-- 116*22028508SToomas Soome jnz next_boot 117*22028508SToomas Soomeboot: mov %bx,%es # Reset %es to zero 118*22028508SToomas Soome jmp LOAD # Jump to boot code 119*22028508SToomas Soomenext_boot: incl (%si) # Next LBA 120*22028508SToomas Soome adcl $0,4(%si) 121*22028508SToomas Soome mov %es,%ax # Adjust segment for next 122*22028508SToomas Soome addw $SECSIZE/16,%ax # sector 123*22028508SToomas Soome mov %ax,%es # 124*22028508SToomas Soome jmp load_boot 125*22028508SToomas Soome# 126*22028508SToomas Soome# Load a sector (64-bit LBA at %si) from disk %dl into %es:%bx by creating 127*22028508SToomas Soome# a EDD packet on the stack and passing it to the BIOS. Trashes %ax and %si. 128*22028508SToomas Soome# 129*22028508SToomas Soomeread: pushl 0x4(%si) # Set the LBA 130*22028508SToomas Soome pushl 0x0(%si) # address 131*22028508SToomas Soome pushw %es # Set the address of 132*22028508SToomas Soome pushw %bx # the transfer buffer 133*22028508SToomas Soome pushw $0x1 # Read 1 sector 134*22028508SToomas Soome pushw $0x10 # Packet length 135*22028508SToomas Soome movw %sp,%si # Packer pointer 136*22028508SToomas Soome movw $0x4200,%ax # BIOS: LBA Read from disk 137*22028508SToomas Soome int $0x13 # Call the BIOS 138*22028508SToomas Soome add $0x10,%sp # Restore stack 139*22028508SToomas Soome jc err_rd # If error 140*22028508SToomas Soome ret 141*22028508SToomas Soome# 142*22028508SToomas Soome# Various error message entry points. 143*22028508SToomas Soome# 144*22028508SToomas Soomeerr_rd: movw $msg_rd,%si # "I/O error loading 145*22028508SToomas Soome jmp putstr # boot loader" 146*22028508SToomas Soome 147*22028508SToomas Soomeerr_noboot: movw $msg_noboot,%si # "Missing boot 148*22028508SToomas Soome jmp putstr # loader" 149*22028508SToomas Soome# 150*22028508SToomas Soome# Output an ASCIZ string to the console via the BIOS. 151*22028508SToomas Soome# 152*22028508SToomas Soomeputstr.0: movw $0x7,%bx # Page:attribute 153*22028508SToomas Soome movb $0xe,%ah # BIOS: Display 154*22028508SToomas Soome int $0x10 # character 155*22028508SToomas Soomeputstr: lodsb # Get character 156*22028508SToomas Soome testb %al,%al # End of string? 157*22028508SToomas Soome jnz putstr.0 # No 158*22028508SToomas Soomeputstr.1: jmp putstr.1 # Await reset 159*22028508SToomas Soome 160*22028508SToomas Soomemsg_rd: .asciz "I/O error" 161*22028508SToomas Soomemsg_noboot: .asciz "No boot loader" 162*22028508SToomas Soome 163*22028508SToomas Soome nop 164*22028508SToomas Soomembr_version: .byte 1, 1 # 1.1 165*22028508SToomas Soome .align 4 166*22028508SToomas Soomestage2_size: .word 1 # bootblock size in sectors 167*22028508SToomas Soomestage2_sector: .quad 256 # lba of bootblock 168*22028508SToomas Soomedisk_uuid: .quad 0 # uuid 169*22028508SToomas Soome .quad 0 170*22028508SToomas Soome 171*22028508SToomas Soome# this is the end of the code block we can use, next is space for 172*22028508SToomas Soome# signature, partition table 4 entries and signature. 173*22028508SToomas Soome .org DISKSIG,0x1b8 # 174*22028508SToomas Soomesig: .long 0 # OS Disk Signature 175*22028508SToomas Soome .word 0 # "Unknown" in PMBR 176*22028508SToomas Soome 177*22028508SToomas Soomepartbl: .byte 0x00 # non-bootable 178*22028508SToomas Soome .byte 0x00 # head 0 179*22028508SToomas Soome .byte 0x02 # sector 180*22028508SToomas Soome .byte 0x00 # cylinder 181*22028508SToomas Soome .byte 0xEE # ID 182*22028508SToomas Soome .byte 0xFF # ending head 183*22028508SToomas Soome .byte 0xFF # ending sector 184*22028508SToomas Soome .byte 0xFF # ending cylinder 185*22028508SToomas Soome .long 0x00000001 # starting LBA 186*22028508SToomas Soome .long 0xFFFFFFFF # size 187*22028508SToomas Soome .fill 0x10,0x3,0x0 # other 3 entries 188*22028508SToomas Soome .word MAGIC # Magic number 189