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biosboot.S revision 1.1.2.3 
      1 /*	$NetBSD: biosboot.S,v 1.1.2.3 2004/09/18 14:35:50 skrll Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2003 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by David Laight.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *        This product includes software developed by the NetBSD
     21  *        Foundation, Inc. and its contributors.
     22  * 4. Neither the name of The NetBSD Foundation nor the names of its
     23  *    contributors may be used to endorse or promote products derived
     24  *    from this software without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     36  * POSSIBILITY OF SUCH DAMAGE.
     37  */
     38 
     39 #include <machine/asm.h>
     40 #include <sys/bootblock.h>
     41 
     42 /*
     43  * Code linked to 0x1000:0 and (usually) read from /boot by bootxx code
     44  *
     45  * On entry:
     46  * 	%dl			BIOS drive number
     47  *	%ebx			Sector number of netbsd partition
     48  *	%ds:%esi		Boot parameter block (patched by installboot)
     49  *	%cs			0x1000
     50  *	%ds, %es, %ss		All zero
     51  *	%sp			near 0xfffc
     52  */
     53 
     54 	.text
     55 	.code16
     56 ENTRY(boot_start)
     57 	jmp	boot_start_1
     58 	.balign	4
     59 ENTRY(boot_magic)
     60 	.long	X86_BOOT_MAGIC_2	/* checked for by bootxx code */
     61 ENTRY(boot_params)
     62 	.long	boot_start_1 - boot_params
     63 #include <boot_params.S>
     64 	. = boot_start + 0x80		/* space for patchable variables */
     65 boot_start_1:
     66 
     67 #if 0
     68 	/* Allow for boot_start not being %cs:0 */
     69 	call	2f
     70 2:	pop	%cx
     71 	sub	$2b, %cx		/* %ax is offset */
     72 	test	$0xf, %cx		/* check code seg aligned */
     73 	jz	3f
     74 	lret				/* not playing if not */
     75 3:	mov	%cs, %ax
     76 	shr	$4, %cx
     77 	add	%cx, %ax		/* segment staring at boot_start */
     78 	push	%ax
     79 	push	$4f
     80 	lret
     81 4:
     82 #endif
     83 
     84 	mov	%cs, %ax
     85 	mov	%ax, %es
     86 
     87 	/* Grab boot_params patched into bootxx by installboot */
     88 	cmpl	$X86_BOOT_MAGIC_1,-4(%si)	/* sanity check ptr */
     89 	jne	2f
     90 	mov	$boot_params, %di
     91 	movl	(%si),%ecx
     92 	cmp	$boot_start_1 - boot_params, %cx
     93 	jbe	1f
     94 	mov	$boot_start_1 - boot_params, %cx
     95 1:	cld
     96 	rep
     97 	movsb
     98 2:
     99 
    100 	mov	%ax, %ds
    101 	movl	$_end, %eax		/* top of bss */
    102 	shr	$4, %eax		/* as a segment */
    103 	add	$0x1001, %ax		/* and + 64k */
    104 	mov	%ax, %ss		/* for stack */
    105 	mov	$0xfffc, %sp		/* %sp at top of it */
    106 
    107 	call	gdt_fixup
    108 
    109 	calll	real_to_prot
    110 	.code32
    111 
    112 	movl	$_end, %ecx		/* zero bss */
    113 	movl	$__bss_start, %edi
    114 	subl	%edi, %ecx
    115 	shr	$2, %ecx		/* _end and __bss_start are aligned */
    116 	xor	%eax, %eax
    117 	rep
    118 	stosl
    119 
    120 	and	$0xff, %edx
    121 	push	%ebx			/* first sector of bios partition */
    122 	push	%edx			/* bios disk */
    123 	call	_C_LABEL(boot2)		/* C bootstrap code */
    124 	add	$8, %esp
    125 	call	prot_to_real
    126 	.code16
    127 
    128 boot_fail:
    129 	push	%ax
    130 	movw	$1f, %si
    131 	call	message
    132 	pop	%si
    133 	call	message
    134 	jmp	loopstop
    135 1:	.asciz	"Boot2 failed: "
    136 
    137 ENTRY(_rtt)
    138 	.code32
    139 	call	prot_to_real
    140 	.code16
    141 loopstop:
    142 	movb	0x86, %ah		/* delay for about a second */
    143 	movw	$16, %cx
    144 	int	$0x15
    145 	int	$0x18			/* might be a boot fail entry */
    146 1:	sti
    147 	hlt
    148 	jmp	1b
    149