9ed24653f7
Add code to the boot blocks to allow the user to place default boot strings on block 1 of the disk (2nd block), should the correct magic numbers be present. If the correct options are used it will 'delete' the name used from block1, thereby assuring that if the boot fails it won't be stuck in an infinite loop. the boot strings are set by the utility "nextboot" (not yet checked in, but being tested.) By default these changes should have no effect on existing installations and if compiled without the NAMEBLOCK option should be essentially identical to the old ones.
440 lines
11 KiB
ArmAsm
440 lines
11 KiB
ArmAsm
/*
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* Mach Operating System
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* Copyright (c) 1992, 1991 Carnegie Mellon University
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* All Rights Reserved.
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*
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* Permission to use, copy, modify and distribute this software and its
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* documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie Mellon
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* the rights to redistribute these changes.
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*
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* from: Mach, Revision 2.2 92/04/04 11:36:29 rpd
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* $Id: start.S,v 1.6 1995/09/16 13:51:20 bde Exp $
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*/
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/*
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Copyright 1988, 1989, 1990, 1991, 1992
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by Intel Corporation, Santa Clara, California.
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All Rights Reserved
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Permission to use, copy, modify, and distribute this software and
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its documentation for any purpose and without fee is hereby
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granted, provided that the above copyright notice appears in all
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copies and that both the copyright notice and this permission notice
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appear in supporting documentation, and that the name of Intel
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not be used in advertising or publicity pertaining to distribution
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of the software without specific, written prior permission.
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INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
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INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
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IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
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CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
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NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
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WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "asm.h"
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.file "start.S"
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SIGNATURE= 0xaa55
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LOADSZ= 15 /* size of unix boot */
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PARTSTART= 0x1be /* starting address of partition table */
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NUMPART= 4 /* number of partitions in partition table */
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PARTSZ= 16 /* each partition table entry is 16 bytes */
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BSDPART= 0xA5 /* value of boot_ind, means bootable partition */
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BOOTABLE= 0x80 /* value of boot_ind, means bootable partition */
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NAMEBLOCKMAGIC= 0xfadefeed /* value of magicnumebr for block2 */
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/* to debug this, Use the DEBUGMSG(msg) macro defined in asm.S */
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.text
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ENTRY(boot1)
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/*
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* start (aka boot1) is loaded at 0x0:0x7c00 but we want 0x7c0:0
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* ljmp to the next instruction to adjust %cs
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*/
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data32
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ljmp $0x7c0, $start
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start:
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/* set up %ds */
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mov %cs, %ax
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mov %ax, %ds
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/* set up %ss and %esp */
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data32
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mov $BOOTSEG, %eax
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mov %ax, %ss
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/*
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* make a little room on the stack for
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* us to save the default bootstring we might find..
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* effectively, we push the bootstring.
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*/
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data32
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mov $(BOOTSTACK - 64), %esp
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/* set up %es, (where we will load boot2 to) */
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mov %ax, %es
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/* bootstrap passes us drive number in %dl */
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cmpb $0x80, %dl
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data32
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jae hd
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fd:
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/*
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* XXX some bootstraps don't pass the drive number in %dl.
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* This is a problem mainly when we are block 0 on a floppy.
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* Force drive 0 for floppies.
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* XXX %dl was assumed valid in the test that led here.
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*/
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mov $0x0, %dl
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/* reset the disk system */
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movb $0x0, %ah
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int $0x13
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data32
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mov $0x0001, %ecx /* cyl 0, sector 1 */
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movb $0, %dh /* head */
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data32
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jmp load
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hd: /**** load sector 0 into the BOOTSEG ****/
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data32
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mov $0x0201, %eax
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xor %ebx, %ebx /* %bx = 0 */
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data32
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mov $0x0001, %ecx
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data32
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andl $0xff, %edx
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/*mov $0x0080, %edx*/
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int $0x13
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data32
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jb read_error
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/* find the first 386BSD partition */
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data32
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mov $PARTSTART, %ebx
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data32
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mov $NUMPART, %ecx
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again:
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addr32
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movb %es:4(%ebx), %al
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cmpb $BSDPART, %al
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data32
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je found
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data32
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add $PARTSZ, %ebx
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data32
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loop again
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data32
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mov $enoboot, %esi
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data32
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jmp err_stop
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/*
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* BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
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* Call with %ah = 0x2
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* %al = number of sectors
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* %ch = cylinder
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* %cl = sector
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* %dh = head
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* %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
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* %es:%bx = segment:offset of buffer
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* Return:
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* %al = 0x0 on success; err code on failure
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*/
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found:
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addr32
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movb %es:1(%ebx), %dh /* head */
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addr32
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movl %es:2(%ebx), %ecx /*sect, cyl (+ 2 bytes junk in top word) */
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load:
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#ifdef NAMEBLOCK
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/*
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* Load the second sector and see if it is a boot instruction block.
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* If it is then scan the contents for the first valid string and copy it to
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* the location of the default boot string.. then zero it out.
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* Finally write the block back to disk with the zero'd out entry..
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* I hate writing at this stage but we need this to be persistant.
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* If the boot fails, then the next boot will get the next string.
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* /etc/rc will regenerate a complete block2 iff teh boot succeeds.
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*
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* Format of block 2 is:
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* [NAMEBLOCKMAGIC] <--0xdeafc0de
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* [nulls]
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* [bootstring]NULL <---e.g. 0:wd(0,a)/kernel.experimental
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* [bootstring]NULL <---e.g. 0:wd(0,a)/kernel.old
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* ....
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* [bootstring]NULL <---e.g. 0:wd(0,f)/kernel
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* FF FF FF
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*/
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where:
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/*
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* save things we might smash
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* (that are not smashed immedatly after us anyway.)
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*/
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data32
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push %ecx /* preserve 'cyl,sector ' */
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data32
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push %edx
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/*
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* Load the second sector
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* BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
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* Call with %ah = 0x2
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* %al = number of sectors
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* %ch = cylinder
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* %cl = sector
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* %dh = head
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* %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
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* %es:%bx = segment:offset of buffer
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* Return:
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* %al = 0x0 on success; err code on failure
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*/
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data32
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movl $0x0201, %eax /function 2 (read) 1 sector */
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xor %ebx, %ebx /* %bx = 0 */ /* buffer address (ES:0) */
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data32
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movl $0x0002, %ecx /* sector 2, cylinder 0 */
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data32
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andl $0x00ff, %edx /* head 0, drive N */
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int $0x13
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data32
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jb read_error
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/*
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* confirm that it is one for us
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*/
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data32
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xorl %ebx, %ebx /* magic number at start of buffer */
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data32
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addr32
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movl %es:(%ebx), %eax
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data32
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cmpl $NAMEBLOCKMAGIC, %eax
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data32
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jne notours /* not ours so return to caller */
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/*
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* scan for a bootstring
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* Skip the magic number, and scan till we find a non-null,
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* or a -1
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*/
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incl %ebx /* quicker and smaller */
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incl %ebx
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incl %ebx
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scan:
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incl %ebx
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addr32
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movb %es:(%ebx), %al /* load the next byte */
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testb %al, %al /* and if it is null */
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data32 /* keep scanning (past deleted entries) */
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jz scan
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incb %al /* now look for -1 */
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data32
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jz notours /* if we reach the 0xFF then we have finished */
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/*
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* save our settings.. we need them twice..
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*/
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data32
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push %ebx
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/*
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* copy it to the default string location
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* which is just above the stack for 64 bytes.
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*/
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data32
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movl $(BOOTSTACK-64), %ecx /* 64 bytes at the top of the stack */
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nxtbyte:
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addr32
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movb %es:(%ebx), %al /* get the next byte in */
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addr32
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movb %al, %es:(%ecx) /* and transfer it to the name buffer */
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incl %ebx /* get on with the next byte */
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incl %ecx /* get on with the next byte */
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testb %al, %al /* if it was 0 then quit this */
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data32
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jnz nxtbyte /* and looop if more to do */
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/*
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* restore the saved settings and
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* zero it out so next time we don't try it again
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*/
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data32
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pop %ebx /* get back our starting location */
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#ifdef NAMEBLOCK_WRITEBACK
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nxtbyte2:
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addr32
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movb %es:(%ebx), %al /* get the byte */
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addr32
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movb $0, %es:(%ebx) /* zero it out */
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data32
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incl %ebx /* point to the next byte */
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testb %al, %al /* check if we have finished.. */
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data32
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jne nxtbyte2
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/*
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* Write the second sector back
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* Load the second sector
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* BIOS call "INT 0x13 Function 0x3" to write sectors from memory to disk
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* Call with %ah = 0x3
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* %al = number of sectors
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* %ch = cylinder
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* %cl = sector
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* %dh = head
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* %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
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* %es:%bx = segment:offset of buffer
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* Return:
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* %al = 0x0 on success; err code on failure
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*/
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data32
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movl $0x0301, %eax /* write 1 sector */
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xor %ebx, %ebx /* buffer is at offset 0 */
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data32
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movl $0x0002, %ecx /* block 2 */
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data32
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andl $0xff, %edx /* head 0 */
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int $0x13
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data32
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jnb notours
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data32
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mov $eread, %esi
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jmp err_stop
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#endif /* NAMEBLOCK_WRITEBACK */
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/*
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* return to the main-line
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*/
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notours:
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data32
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pop %edx
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data32
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pop %ecx
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#endif
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movb $0x2, %ah /* function 2 */
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movb $LOADSZ, %al /* number of blocks */
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xor %ebx, %ebx /* %bx = 0, put it at 0 in the BOOTSEG */
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int $0x13
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data32
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jb read_error
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/*
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* ljmp to the second stage boot loader (boot2).
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* After ljmp, %cs is BOOTSEG and boot1 (512 bytes) will be used
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* as an internal buffer "intbuf".
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*/
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data32
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ljmp $BOOTSEG, $ EXT(boot2)
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/*
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* read_error
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*/
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read_error:
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data32
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mov $eread, %esi
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err_stop:
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data32
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call message
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data32
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jmp stop
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/*
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* message: write the error message in %ds:%esi to console
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*/
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ENTRY(message)
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message:
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/*
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* Use BIOS "int 10H Function 0Eh" to write character in teletype mode
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* %ah = 0xe %al = character
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* %bh = page %bl = foreground color (graphics modes)
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*/
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data32
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push %eax
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data32
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push %ebx
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data32
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mov $0x0001, %ebx
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cld
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nextb:
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lodsb /* load a byte into %al */
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cmpb $0x0, %al
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data32
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je done
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movb $0xe, %ah
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int $0x10 /* display a byte */
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data32
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jmp nextb
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done:
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data32
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pop %ebx
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data32
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pop %eax
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data32
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ret
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stop: hlt
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data32
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jmp stop /* halt doesnt actually halt forever */
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/* error messages */
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#ifdef DEBUG
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one: String "1-\0"
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two: String "2-\0"
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three: String "3-\0"
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four: String "4-\0"
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#endif DEBUG
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#ifdef NAMEBLOCK_WRITEBACK
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ewrite: String "Write error\r\n\0"
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#endif /* NAMEBLOCK_WRITEBACK */
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eread: String "Read error\r\n\0"
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enoboot: String "No bootable partition\r\n\0"
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endofcode:
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/*
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* Dummy partition table in case we are block 0. The ending c/h/s values
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* of the non-null partition are almost arbitary. The length of this
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* partition is bogus for backwards compatibility and as a signature.
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* A real partition table shouldn't be as weird and broken as this one,
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* and the isa slice initialization routine interprets this table as
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* saying that the whole disk is used for FreeBSD.
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*/
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/* flag, head, sec, cyl, typ, ehead, esect, ecyl, start, len */
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. = EXT(boot1) + PARTSTART
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strttbl:
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.byte 0x0,0,0,0,0,0,0,0
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.long 0,0
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.byte 0x0,0,0,0,0,0,0,0
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.long 0,0
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.byte 0x0,0,0,0,0,0,0,0
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.long 0,0
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.byte BOOTABLE,0,1,0,BSDPART,255,255,255
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.long 0,50000
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/* the last 2 bytes in the sector 0 contain the signature */
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. = EXT(boot1) + 0x1fe
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.value SIGNATURE
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ENTRY(disklabel)
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. = EXT(boot1) + 0x400
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