/* $OpenBSD: start.S,v 1.4 1996/06/02 11:18:14 mickey Exp $ */ /* $NetBSD: start.S,v 1.12 1995/01/18 17:34:18 mycroft Exp $ */ /*- * * Changes by Michael Shalayeff May 1996 * Ported to boot 386BSD by Julian Elischer (julian@tfs.com) Sept 1992 * * 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. */ /* 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 #define addr32 .byte 0x67 #define data32 .byte 0x66 BOOTSEG = 0x1000 # boot will be loaded here (below 640K) BOOTSTACK = 0xfffc # 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 .globl start ENTRY(boot1) start: #ifndef DOSREAD # start (aka boot1) is loaded at 0x0:0x7c00 but we want 0x7c0:0 # ljmp to the next instruction to adjust %cs data32 ljmp $0x7c0, $start1 start1: # set up %ds movl %cs, %ax movl %ax, %ds # set up %ss and %esp data32 movl $BOOTSEG, %eax movl %ax, %ss data32 movl $BOOTSTACK, %esp /*** set up %es, (where we will load boot2 to) ***/ movl %ax, %es #ifdef SERIAL # Initialize the serial port to 9600 baud, 8N1. data32 pushl %edx data32 movl $0x00e3, %eax xorl %edx, %edx int $0x14 data32 popl %edx #endif #ifdef FDDEBUG data32 movl $one, %esi data32 call message #endif #if !defined(NOFD) && !defined(NOHD) # bootstrap passes us drive number in %dl testb $0x80, %dl data32 jnz hd #endif #ifndef NOFD fd: # reset the disk system #ifdef FDDEBUG data32 movl $two, %esi data32 call message #endif movb $0x00, %ah int $0x13 #ifdef FDDEBUG data32 movl $three, %esi data32 call message #endif data32 movl $0x0001, %ecx # cyl 0, sector 1 movb $0x00, %dh # head # XXX Override the drive number. # movb $0x00, %dl data32 jmp load #endif #ifndef NOHD hd: /**** load sector 0 into the BOOTSEG ****/ #ifdef DEBUG data32 movl $four, %esi data32 call message #endif data32 movl $0x0201, %eax xorl %ebx, %ebx # %bx = 0 data32 movl $0x0001, %ecx data32 andl $0xff, %edx int $0x13 data32 jb read_error /***# find the first active partition *****/ data32 movl $PARTSTART, %ebx data32 movl $NUMPART, %ecx again: addr32 cmpb $BOOTABLE, %es:(%ebx) data32 je found data32 addl $PARTSZ, %ebx data32 loop again data32 movl $enoboot, %esi data32 jmp err_stop #endif /* # 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 */ #ifndef NOHD found: addr32 movb %es:1(%ebx), %dh /* head */ addr32 movl %es:2(%ebx), %ecx /*sect, cyl (+ 2 bytes junk in top word) */ data32 pushl %ecx addr32 movb %es:4(%ebx), %al cmpb $BSDPART, %al je loadbsd # set up %ds movl %cs, %ax movl %ax, %ds # relocate the code to leave the space for next stage movl $0x5c0, %ax movl %ax, %es data32 xorl %esi, %esi data32 xorl %edi, %edi data32 movl $0x100, %ecx cld rep movsl # jump to the new code data32 ljmp $0x5c0, $start2 start2: movl $0x7c0, %ax movl %ax, %es loadbsd: data32 popl %ecx #endif load: data32 pushl %ebx movb $0x2, %ah /* function 2 */ movb $LOADSZ, %al /* number of blocks */ xorl %ebx, %ebx /* %bx = 0, put it at 0 in the BOOTSEG */ int $0x13 data32 popl %ebx data32 jb read_error #ifndef NOHD testb $0x80, %dl /* no fdisk partion table on floppy */ data32 jz dobsd addr32 movb %es:4(%ebx), %al cmpb $BSDPART, %al je dobsd ljmp $0, $0x7c00 dobsd: #endif #ifdef DEBUG data32 movl $six, %esi data32 call message #endif # 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". data32 ljmp $BOOTSEG, $_C_LABEL(boot2) # # read_error # read_error: data32 movl $eread, %esi err_stop: data32 call message data32 jmp stop # # message: write the error message in %ds:%esi to console # message: /* #ifndef SERIAL # BIOS call "INT 10H Function 0Eh" to write character to console # Call with %ah = 0x0e # %al = character # %bh = page # %bl = foreground color #else # BIOS call "INT 14H Function 01h" to write character to console # Call with %ah = 0x01 # %al = character # %dx = port number #endif */ data32 pushl %eax data32 pushl %ebx data32 pushl %edx nextb: cld lodsb # load a byte into %al testb %al, %al data32 jz done #ifndef SERIAL movb $0x0e, %ah data32 movl $0x0001, %ebx int $0x10 #else movb $0x01, %ah xorl %edx, %edx int $0x14 #endif data32 jmp nextb done: data32 popl %edx data32 popl %ebx data32 popl %eax data32 ret #else /* !DOSREAD */ movb $0xff, %dl jmp _C_LABEL(boot2) #endif /* DOSREAD */ /* Conventional GDT indexes. */ BOOT_CS_INDEX = 3 BOOT_CS16_INDEX = 5 BOOT_DS_INDEX = 4 ENTRY(boot2) data32 xorl %eax, %eax movl %cs, %ax movl %ax, %ds movl %ax, %es addr32 data32 movl %eax, _C_LABEL(ourseg) data32 shll $4, %eax /* fix up GDT entries for bootstrap */ #define FIXUP(gdt_index) \ addr32; \ movl %eax, _C_LABEL(Gdt)+(8*gdt_index)+2; /* actually movw %ax */ \ addr32; \ movb %bl, _C_LABEL(Gdt)+(8*gdt_index)+4 data32 shldl $16, %eax, %ebx FIXUP(BOOT_CS_INDEX) FIXUP(BOOT_CS16_INDEX) FIXUP(BOOT_DS_INDEX) /* fix up GDT pointer */ data32 addl $_C_LABEL(Gdt), %eax addr32 data32 movl %eax, _C_LABEL(Gdtr)+2 /* change to protected mode */ data32 call _C_LABEL(real_to_prot) /* clear the bss */ movl $_C_LABEL(edata), %edi movl $_C_LABEL(end), %ecx subl %edi, %ecx subb %al, %al rep stosb movzbl %dl, %edx /* discard head (%dh) and random high bits */ pushl %edx call _C_LABEL(boot) stop: cli hlt /* error messages */ #if defined(DEBUG) && !defined(DOSREAD) #ifdef FDDEBUG one: .asciz "1\r\n" two: .asciz "2\r\n" three: .asciz "3\r\n" #endif /* FDDEBUG */ four: .asciz "4\r\n" five: .asciz "5\r\n" six: .asciz "6\r\n" seven: .asciz "7\r\n" #endif /* DEBUG */ #ifndef DOSREAD eread: .asciz "Read error\r\n" enoboot: .asciz "No bootable partition\r\n" endofcode: /* throw in a partition in case we are block0 as well */ /* flag, head, sec, cyl, typ, ehead, esect, ecyl, start, len */ . = _C_LABEL(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 */ . = _C_LABEL(boot1) + 0x1fe .short SIGNATURE . = _C_LABEL(boot1) + 0x200 #endif .globl _disklabel _disklabel: . = _C_LABEL(boot1) + 0x400