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Annotation of src/sys/arch/i386/stand/boot/biosboot.S, Revision 1.5.74.1

1.5.74.1! mjf         1: /*     $NetBSD$        */
1.1       dsl         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:  *
                     19:  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
                     20:  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
                     21:  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
                     22:  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
                     23:  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
                     24:  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
                     25:  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
                     26:  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
                     27:  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
                     28:  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
                     29:  * POSSIBILITY OF SUCH DAMAGE.
                     30:  */
                     31:
                     32: #include <machine/asm.h>
1.2       lukem      33: #include <sys/bootblock.h>
1.1       dsl        34:
                     35: /*
                     36:  * Code linked to 0x1000:0 and (usually) read from /boot by bootxx code
                     37:  *
                     38:  * On entry:
                     39:  *     %dl                     BIOS drive number
                     40:  *     %ebx                    Sector number of netbsd partition
                     41:  *     %ds:%esi                Boot parameter block (patched by installboot)
                     42:  *     %cs                     0x1000
                     43:  *     %ds, %es, %ss           All zero
                     44:  *     %sp                     near 0xfffc
                     45:  */
                     46:
                     47:        .text
                     48:        .code16
                     49: ENTRY(boot_start)
                     50:        jmp     boot_start_1
1.3       dsl        51:        .balign 4
1.1       dsl        52: ENTRY(boot_magic)
                     53:        .long   X86_BOOT_MAGIC_2        /* checked for by bootxx code */
                     54: ENTRY(boot_params)
                     55:        .long   boot_start_1 - boot_params
1.3       dsl        56: #include <boot_params.S>
1.1       dsl        57:        . = boot_start + 0x80           /* space for patchable variables */
                     58: boot_start_1:
                     59:
                     60: #if 0
                     61:        /* Allow for boot_start not being %cs:0 */
                     62:        call    2f
                     63: 2:     pop     %cx
                     64:        sub     $2b, %cx                /* %ax is offset */
                     65:        test    $0xf, %cx               /* check code seg aligned */
                     66:        jz      3f
                     67:        lret                            /* not playing if not */
                     68: 3:     mov     %cs, %ax
                     69:        shr     $4, %cx
                     70:        add     %cx, %ax                /* segment staring at boot_start */
                     71:        push    %ax
                     72:        push    $4f
                     73:        lret
                     74: 4:
                     75: #endif
                     76:
                     77:        mov     %cs, %ax
                     78:        mov     %ax, %es
                     79:
1.4       junyoung   80:        /* Grab boot_params patched into bootxx by installboot */
1.1       dsl        81:        cmpl    $X86_BOOT_MAGIC_1,-4(%si)       /* sanity check ptr */
                     82:        jne     2f
                     83:        mov     $boot_params, %di
                     84:        movl    (%si),%ecx
                     85:        cmp     $boot_start_1 - boot_params, %cx
                     86:        jbe     1f
                     87:        mov     $boot_start_1 - boot_params, %cx
                     88: 1:     cld
                     89:        rep
                     90:        movsb
                     91: 2:
                     92:
                     93:        mov     %ax, %ds
                     94:        movl    $_end, %eax             /* top of bss */
                     95:        shr     $4, %eax                /* as a segment */
                     96:        add     $0x1001, %ax            /* and + 64k */
                     97:        mov     %ax, %ss                /* for stack */
                     98:        mov     $0xfffc, %sp            /* %sp at top of it */
                     99:
                    100:        call    gdt_fixup
                    101:
                    102:        calll   real_to_prot
                    103:        .code32
                    104:
                    105:        movl    $_end, %ecx             /* zero bss */
                    106:        movl    $__bss_start, %edi
                    107:        subl    %edi, %ecx
                    108:        shr     $2, %ecx                /* _end and __bss_start are aligned */
                    109:        xor     %eax, %eax
                    110:        rep
                    111:        stosl
                    112:
                    113:        and     $0xff, %edx
                    114:        push    %ebx                    /* first sector of bios partition */
                    115:        push    %edx                    /* bios disk */
                    116:        call    _C_LABEL(boot2)         /* C bootstrap code */
                    117:        add     $8, %esp
                    118:        call    prot_to_real
                    119:        .code16
                    120:
                    121: boot_fail:
                    122:        push    %ax
                    123:        movw    $1f, %si
                    124:        call    message
                    125:        pop     %si
                    126:        call    message
                    127:        jmp     loopstop
                    128: 1:     .asciz  "Boot2 failed: "
                    129:
                    130: ENTRY(_rtt)
                    131:        .code32
                    132:        call    prot_to_real
                    133:        .code16
                    134: loopstop:
                    135:        movb    0x86, %ah               /* delay for about a second */
                    136:        movw    $16, %cx
                    137:        int     $0x15
                    138:        int     $0x18                   /* might be a boot fail entry */
                    139: 1:     sti
                    140:        hlt
                    141:        jmp     1b