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Diffstat (limited to 'sys/i386/boot/biosboot/start.S')
| -rw-r--r-- | sys/i386/boot/biosboot/start.S | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/sys/i386/boot/biosboot/start.S b/sys/i386/boot/biosboot/start.S new file mode 100644 index 0000000..aa65212 --- /dev/null +++ b/sys/i386/boot/biosboot/start.S @@ -0,0 +1,292 @@ +/* + * Mach Operating System + * Copyright (c) 1992, 1991 Carnegie Mellon University + * All Rights Reserved. + * + * Permission to use, copy, modify and distribute this software and its + * documentation is hereby granted, provided that both the copyright + * notice and this permission notice appear in all copies of the + * software, derivative works or modified versions, and any portions + * thereof, and that both notices appear in supporting documentation. + * + * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" + * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR + * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. + * + * Carnegie Mellon requests users of this software to return to + * + * Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU + * School of Computer Science + * Carnegie Mellon University + * Pittsburgh PA 15213-3890 + * + * any improvements or extensions that they make and grant Carnegie Mellon + * the rights to redistribute these changes. + * + * from: Mach, Revision 2.2 92/04/04 11:36:29 rpd + * $Id: start.S,v 1.2 1993/10/16 19:11:38 rgrimes Exp $ + */ + +/* + Copyright 1988, 1989, 1990, 1991, 1992 + by Intel Corporation, Santa Clara, California. + + All Rights Reserved + +Permission to use, copy, modify, and distribute this software and +its documentation for any purpose and without fee is hereby +granted, provided that the above copyright notice appears in all +copies and that both the copyright notice and this permission notice +appear in supporting documentation, and that the name of Intel +not be used in advertising or publicity pertaining to distribution +of the software without specific, written prior permission. + +INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE +INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, +IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR +CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM +LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT, +NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION +WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. +*/ +#include "asm.h" + + .file "start.s" + +BOOTSEG = 0x9000 # boot will be loaded here (below 640K) +BOOTSTACK = 0xe000 # boot stack +SIGNATURE = 0xaa55 +LOADSZ = 15 # size of unix boot +PARTSTART = 0x1be # starting address of partition table +NUMPART = 4 # number of partitions in partition table +PARTSZ = 16 # each partition table entry is 16 bytes +BSDPART = 0xA5 # value of boot_ind, means bootable partition +BOOTABLE = 0x80 # value of boot_ind, means bootable partition + + .text + +ENTRY(boot1) + # start (aka boot1) is loaded at 0x0:0x7c00 but we want 0x7c0:0 + # ljmp to the next instruction to adjust %cs + data32 + ljmp $0x7c0, $start + +start: + # set up %ds + mov %cs, %ax + mov %ax, %ds + + # set up %ss and %esp + data32 + mov $BOOTSEG, %eax + mov %ax, %ss + data32 + mov $BOOTSTACK, %esp + + /*** set up %es, (where we will load boot2 to) ***/ + mov %ax, %es + +#ifdef DEBUG + data32 + mov $one, %esi + data32 + call message +#endif + + # bootstrap passes us drive number in %dl + cmpb $0x80, %dl + data32 + jae hd + +fd: + mov $0x0, %dl +# reset the disk system +#ifdef DEBUG + data32 + mov $two, %esi + data32 + call message +#endif + movb $0x0, %ah + int $0x13 + data32 + mov $0x0001, %ecx # cyl 0, sector 1 + movb $0, %dh # head +#ifdef DEBUG + data32 + mov $three, %esi + data32 + call message +#endif + data32 + jmp load + +hd: /**** load sector 0 into the BOOTSEG ****/ +#ifdef DEBUG + data32 + mov $four, %esi + data32 + call message +#endif + data32 + mov $0x0201, %eax + xor %ebx, %ebx # %bx = 0 + data32 + mov $0x0001, %ecx +#ifdef DEBUG + data32 + mov $five, %esi + data32 + call message +#endif + data32 + andl $0xff, %edx + /*mov $0x0080, %edx*/ + int $0x13 + data32 + jb read_error + + /***# find the first 386BSD partition *****/ + data32 + mov $PARTSTART, %ebx + data32 + mov $NUMPART, %ecx +again: + addr32 + movb %es:4(%ebx), %al + cmpb $BSDPART, %al + data32 + je found + data32 + add $PARTSZ, %ebx + data32 + loop again + data32 + mov $enoboot, %esi + data32 + jmp err_stop + + +/* +# BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory +# Call with %ah = 0x2 +# %al = number of sectors +# %ch = cylinder +# %cl = sector +# %dh = head +# %dl = drive (0x80 for hard disk, 0x0 for floppy disk) +# %es:%bx = segment:offset of buffer +# Return: +# %al = 0x0 on success; err code on failure +*/ + +found: + addr32 + movb %es:1(%ebx), %dh /* head */ + addr32 + movl %es:2(%ebx), %ecx /*sect, cyl (+ 2 bytes junk in top word) */ + +load: + movb $0x2, %ah /* function 2 */ + movb $LOADSZ, %al /* number of blocks */ + xor %ebx, %ebx /* %bx = 0, put it at 0 in the BOOTSEG */ + int $0x13 + data32 + jb read_error + + # ljmp to the second stage boot loader (boot2). + # After ljmp, %cs is BOOTSEG and boot1 (512 bytes) will be used + # as an internal buffer "intbuf". + +#ifdef DEBUG + data32 + mov $six, %esi + data32 + call message +#endif + data32 + ljmp $BOOTSEG, $ EXT(boot2) + +# +# read_error +# + +read_error: + data32 + mov $eread, %esi +err_stop: + data32 + call message + data32 + jmp stop + +# +# message: write the error message in %ds:%esi to console +# + +message: +/* + # Use BIOS "int 10H Function 0Eh" to write character in teletype mode + # %ah = 0xe %al = character + # %bh = page %bl = foreground color (graphics modes) +*/ + + data32 + push %eax + data32 + push %ebx + data32 + mov $0x0001, %ebx + cld + +nextb: + lodsb # load a byte into %al + cmpb $0x0, %al + data32 + je done + movb $0xe, %ah + int $0x10 # display a byte + data32 + jmp nextb +done: + data32 + pop %ebx + data32 + pop %eax + data32 + ret + +stop: hlt + data32 + jmp stop # halt doesnt actually halt forever + +/* error messages */ + +#ifdef DEBUG +one: String "1\r\n\0" +two: String "2\r\n\0" +three: String "3\r\n\0" +four: String "4\r\n\0" +five: String "5\r\n\0" +six: String "6\r\n\0" +seven: String "7\r\n\0" +#endif DEBUG +eread: String "Read error\r\n\0" +enoboot: String "No bootable partition\r\n\0" +endofcode: +/* throw in a partition in case we are block0 as well */ +/* flag, head, sec, cyl, typ, ehead, esect, ecyl, start, len */ + . = EXT(boot1) + PARTSTART + .byte 0x0,0,0,0,0,0,0,0 + .long 0,0 + .byte 0x0,0,0,0,0,0,0,0 + .long 0,0 + .byte 0x0,0,0,0,0,0,0,0 + .long 0,0 + .byte BOOTABLE,0,1,0,BSDPART,255,255,255 + .long 0,50000 +/* the last 2 bytes in the sector 0 contain the signature */ + . = EXT(boot1) + 0x1fe + .value SIGNATURE +ENTRY(disklabel) + . = EXT(boot1) + 0x400 |
