# This code is no longer used in Etherboot. It is not maintained and # may not work. # # Copyright (c) 1998 Robert Nordier # All rights reserved. # Very small bootrom changes by Luigi Rizzo # # I recently had the problem of downloading the etherboot code # from a hard disk partition instead of a floppy, and noticed that # floppyload.S does not do the job. With a bit of hacking to # the FreeBSD's boot1.s code, I managed to obtain a boot sector # which works both for floppies and hard disks -- basically you # do something like # # cat boot1a bin32/.lzrom > /dev/ad0s4 # # (or whatever is the HD partition you are using, I am using slice # 4 on FreeBSD) and you are up and running. # Then with "fdisk" you have to mark your partition as having type "1" # (which is listed as DOS-- but basically it must be something matching # the variable PRT_BSD in the assembly source below). # # # Redistribution and use in source and binary forms are freely # permitted provided that the above copyright notice and this # paragraph and the following disclaimer are duplicated in all # such forms. # # This software is provided "AS IS" and without any express or # implied warranties, including, without limitation, the implied # warranties of merchantability and fitness for a particular # purpose. # # Makefile: #boot1a: boot1a.out # objcopy -S -O binary boot1a.out boot1a # #boot1a.out: boot1a.o # ld -nostdlib -static -N -e start -Ttext 0x7c00 -o boot1a.out boot1a.o # #boot1a.o: boot1a.s # as --defsym FLAGS=0x80 boot1a.s -o boot1a.o # # # $FreeBSD: src/sys/boot/i386/boot2/boot1.s,v 1.10.2.2 2000/07/07 21:12:32 jhb Exp $ # Memory Locations .set MEM_REL,0x700 # Relocation address .set MEM_ARG,0x900 # Arguments .set MEM_ORG,0x7c00 # Origin .set MEM_BUF,0x8c00 # Load area .set MEM_BTX,0x9000 # BTX start .set MEM_JMP,0x9010 # BTX entry point .set MEM_USR,0xa000 # Client start .set BDA_BOOT,0x472 # Boot howto flag # Partition Constants .set PRT_OFF,0x1be # Partition offset .set PRT_NUM,0x4 # Partitions .set PRT_BSD,0x1 # Partition type # Flag Bits .set FL_PACKET,0x80 # Packet mode # Misc. Constants .set SIZ_PAG,0x1000 # Page size .set SIZ_SEC,0x200 # Sector size .globl start .globl xread .code16 start: jmp main # Start recognizably .org 0x4,0x90 # # Trampoline used by boot2 to call read to read data from the disk via # the BIOS. Call with: # # %cx:%ax - long - LBA to read in # %es:(%bx) - caddr_t - buffer to read data into # %dl - byte - drive to read from # %dh - byte - num sectors to read # xread: push %ss # Address pop %ds # data # # Setup an EDD disk packet and pass it to read # xread.1: # Starting pushl $0x0 # absolute push %cx # block push %ax # number push %es # Address of push %bx # transfer buffer xor %ax,%ax # Number of movb %dh,%al # blocks to push %ax # transfer push $0x10 # Size of packet mov %sp,%bp # Packet pointer callw read # Read from disk lea 0x10(%bp),%sp # Clear stack lret # To far caller # # Load the rest of boot2 and BTX up, copy the parts to the right locations, # and start it all up. # # # Setup the segment registers to flat addressing (segment 0) and setup the # stack to end just below the start of our code. # main: cld # String ops inc xor %cx,%cx # Zero mov %cx,%es # Address mov %cx,%ds # data mov %cx,%ss # Set up mov $start,%sp # stack # # Relocate ourself to MEM_REL. Since %cx == 0, the inc %ch sets # %cx == 0x100. # mov %sp,%si # Source mov $MEM_REL,%di # Destination incb %ch # Word count rep # Copy movsw # code # # If we are on a hard drive, then load the MBR and look for the first # FreeBSD slice. We use the fake partition entry below that points to # the MBR when we call nread. The first pass looks for the first active # FreeBSD slice. The second pass looks for the first non-active FreeBSD # slice if the first one fails. # mov $part4,%si # Partition cmpb $0x80,%dl # Hard drive? jb main.4 # No movb $0x1,%dh # Block count callw nread # Read MBR mov $0x1,%cx # Two passes main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table movb $0x1,%dh # Partition main.2: cmpb $PRT_BSD,0x4(%si) # Our partition type? jne main.3 # No jcxz main.5 # If second pass testb $0x80,(%si) # Active? jnz main.5 # Yes main.3: add $0x10,%si # Next entry incb %dh # Partition cmpb $0x1+PRT_NUM,%dh # In table? jb main.2 # Yes dec %cx # Do two jcxz main.1 # passes # # If we get here, we didn't find any FreeBSD slices at all, so print an # error message and die. # booterror: mov $msg_part,%si # Message jmp error # Error # # Floppies use partition 0 of drive 0. # main.4: xor %dx,%dx # Partition:drive # # Ok, we have a slice and drive in %dx now, so use that to locate and load # boot2. %si references the start of the slice we are looking for, so go # ahead and load up the first 16 sectors (boot1 + boot2) from that. When # we read it in, we conveniently use 0x8c00 as our transfer buffer. Thus, # boot1 ends up at 0x8c00, and boot2 starts at 0x8c00 + 0x200 = 0x8e00. # The first part of boot2 is the disklabel, which is 0x200 bytes long. # The second part is BTX, which is thus loaded into 0x9000, which is where # it also runs from. The boot2.bin binary starts right after the end of # BTX, so we have to figure out where the start of it is and then move the # binary to 0xb000. Normally, BTX clients start at MEM_USR, or 0xa000, but # when we use btxld create boot2, we use an entry point of 0x1000. That # entry point is relative to MEM_USR; thus boot2.bin starts at 0xb000. # main.5: mov %dx,MEM_ARG # Save args movb $0x2,%dh # Sector count mov $0x7e00, %bx callw nreadbx # Read disk movb $0x40,%dh # Sector count movb %dh, %al callw puthex mov $0x7e00, %bx callw nreadbx # Read disk push %si mov $msg_r1,%si callw putstr pop %si lcall $0x800,$0 # enter the rom code int $0x19 msg_r1: .asciz " done\r\n" .if 0 mov $MEM_BTX,%bx # BTX mov 0xa(%bx),%si # Get BTX length and set add %bx,%si # %si to start of boot2.bin mov $MEM_USR+SIZ_PAG,%di # Client page 1 mov $MEM_BTX+0xe*SIZ_SEC,%cx # Byte sub %si,%cx # count rep # Relocate movsb # client sub %di,%cx # Byte count xorb %al,%al # Zero assumed bss from rep # the end of boot2.bin stosb # up to 0x10000 callw seta20 # Enable A20 jmp start+MEM_JMP-MEM_ORG # Start BTX # # Enable A20 so we can access memory above 1 meg. # seta20: cli # Disable interrupts seta20.1: inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.1 # Yes movb $0xd1,%al # Command: Write outb %al,$0x64 # output port seta20.2: inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.2 # Yes movb $0xdf,%al # Enable outb %al,$0x60 # A20 sti # Enable interrupts retw # To caller .endif # # Trampoline used to call read from within boot1. # nread: mov $MEM_BUF,%bx # Transfer buffer nreadbx: # same but address is in bx mov 0x8(%si),%ax # Get mov 0xa(%si),%cx # LBA push %bx push %ax callw putword pop %ax pop %bx push %cs # Read from callw xread.1 # disk jnc return # If success, return mov $msg_read,%si # Otherwise, set the error # message and fall through to # the error routine # # Print out the error message pointed to by %ds:(%si) followed # by a prompt, wait for a keypress, and then reboot the machine. # error: callw putstr # Display message mov $prompt,%si # Display callw putstr # prompt xorb %ah,%ah # BIOS: Get int $0x16 # keypress movw $0x1234, BDA_BOOT # Do a warm boot ljmp $0xffff,$0x0 # reboot the machine # # Display a null-terminated string using the BIOS output. # putstr.0: call putchar putstr: lodsb # Get char testb %al,%al # End of string? jne putstr.0 # No retw putword: push %ax movb $'.', %al callw putchar movb %ah, %al callw puthex pop %ax puthex: push %ax shr $4, %al callw putdigit pop %ax putdigit: andb $0xf, %al addb $0x30, %al cmpb $0x39, %al jbe putchar addb $7, %al putchar: push %ax mov $0x7,%bx movb $0xe,%ah int $0x10 pop %ax retw # # Overused return code. ereturn is used to return an error from the # read function. Since we assume putstr succeeds, we (ab)use the # same code when we return from putstr. # ereturn: movb $0x1,%ah # Invalid stc # argument return: retw # To caller # # Reads sectors from the disk. If EDD is enabled, then check if it is # installed and use it if it is. If it is not installed or not enabled, then # fall back to using CHS. Since we use a LBA, if we are using CHS, we have to # fetch the drive parameters from the BIOS and divide it out ourselves. # Call with: # # %dl - byte - drive number # stack - 10 bytes - EDD Packet # read: push %dx # Save movb $0x8,%ah # BIOS: Get drive int $0x13 # parameters movb %dh,%ch # Max head number pop %dx # Restore jc return # If error andb $0x3f,%cl # Sectors per track jz ereturn # If zero cli # Disable interrupts mov 0x8(%bp),%eax # Get LBA push %dx # Save movzbl %cl,%ebx # Divide by xor %edx,%edx # sectors div %ebx # per track movb %ch,%bl # Max head number movb %dl,%ch # Sector number inc %bx # Divide by xorb %dl,%dl # number div %ebx # of heads movb %dl,%bh # Head number pop %dx # Restore cmpl $0x3ff,%eax # Cylinder number supportable? sti # Enable interrupts ja read.7 # No, try EDD xchgb %al,%ah # Set up cylinder rorb $0x2,%al # number orb %ch,%al # Merge inc %ax # sector xchg %ax,%cx # number movb %bh,%dh # Head number subb %ah,%al # Sectors this track mov 0x2(%bp),%ah # Blocks to read cmpb %ah,%al # To read jb read.2 # this movb %ah,%al # track read.2: mov $0x5,%di # Try count read.3: les 0x4(%bp),%bx # Transfer buffer push %ax # Save movb $0x2,%ah # BIOS: Read int $0x13 # from disk pop %bx # Restore jnc read.4 # If success dec %di # Retry? jz read.6 # No xorb %ah,%ah # BIOS: Reset int $0x13 # disk system xchg %bx,%ax # Block count jmp read.3 # Continue read.4: movzbw %bl,%ax # Sectors read add %ax,0x8(%bp) # Adjust jnc read.5 # LBA, incw 0xa(%bp) # transfer read.5: shlb %bl # buffer add %bl,0x5(%bp) # pointer, sub %al,0x2(%bp) # block count ja read # If not done read.6: retw # To caller read.7: testb $FL_PACKET,%cs:MEM_REL+flags-start # LBA support enabled? jz ereturn # No, so return an error mov $0x55aa,%bx # Magic push %dx # Save movb $0x41,%ah # BIOS: Check int $0x13 # extensions present pop %dx # Restore jc return # If error, return an error cmp $0xaa55,%bx # Magic? jne ereturn # No, so return an error testb $0x1,%cl # Packet interface? jz ereturn # No, so return an error mov %bp,%si # Disk packet movb $0x42,%ah # BIOS: Extended int $0x13 # read retw # To caller # Messages msg_read: .asciz "Rd" msg_part: .asciz "Boot" prompt: .asciz " err\r\n" flags: .byte FLAGS # Flags .org PRT_OFF,0x90 # Partition table .fill 0x30,0x1,0x0 part4: .byte 0x80 .byte 0x00 # start head .byte 0x01 # start sector (6 bits) + start cyl (2 bit) .byte 0x00 # start cyl (low 8 bits) .byte 0x1 # part.type .byte 0xff # end head .byte 0xff # end sect (6) + end_cyl(2) .byte 0xff # end cyl .byte 0x00, 0x00, 0x00, 0x00 # explicit start .byte 0x50, 0xc3, 0x00, 0x00 # 50000 sectors long, bleh .word 0xaa55 # Magic number