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Annotation of Net2/arch/i386/stand/wdbootblk.c, revision 1.1

1.1     ! root        1: /*-
        !             2:  * Copyright (c) 1990 The Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * This code is derived from software contributed to Berkeley by
        !             6:  * William Jolitz.
        !             7:  *
        !             8:  * Redistribution and use in source and binary forms, with or without
        !             9:  * modification, are permitted provided that the following conditions
        !            10:  * are met:
        !            11:  * 1. Redistributions of source code must retain the above copyright
        !            12:  *    notice, this list of conditions and the following disclaimer.
        !            13:  * 2. Redistributions in binary form must reproduce the above copyright
        !            14:  *    notice, this list of conditions and the following disclaimer in the
        !            15:  *    documentation and/or other materials provided with the distribution.
        !            16:  * 3. All advertising materials mentioning features or use of this software
        !            17:  *    must display the following acknowledgement:
        !            18:  *     This product includes software developed by the University of
        !            19:  *     California, Berkeley and its contributors.
        !            20:  * 4. Neither the name of the University nor the names of its contributors
        !            21:  *    may be used to endorse or promote products derived from this software
        !            22:  *    without specific prior written permission.
        !            23:  *
        !            24:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            25:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            26:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            27:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            28:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            29:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            30:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            31:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            32:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            33:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            34:  * SUCH DAMAGE.
        !            35:  *
        !            36:  *     @(#)wdbootblk.c 7.1 (Berkeley) 4/28/91
        !            37:  */
        !            38: 
        !            39: /*
        !            40:  * wdbootblk.s:
        !            41:  *     Written 7/6/90 by William F. Jolitz
        !            42:  *     Initial block boot for AT/386 with typical Western Digital
        !            43:  *     WD 1002-WA2 (or upwards compatable). Works either as
        !            44:  *     first and sole partition bootstrap, or as loaded by a
        !            45:  *     earlier BIOS boot when on an inner partition of the disk.
        !            46:  *
        !            47:  *     Goal is to read in sucessive 7.5Kbytes of bootstrap to
        !            48:  *     execute.
        !            49:  *
        !            50:  *     No attempt is made to handle disk errors.
        !            51:  */
        !            52: #include "i386/isa/isa.h"
        !            53: #include "i386/isa/wdreg.h"
        !            54: #define        NOP     jmp 1f ; nop ; 1:
        !            55: #define BIOSRELOC      0x7c00
        !            56: #define start          0x70400
        !            57: 
        !            58:        /* step 0 force descriptors to bottom of address space */
        !            59: 
        !            60:        .byte 0xfa,0xb8,0x30,0x00,0x8e,0xd0,0xbc,0x00,0x01 #ll fb
        !            61: 
        !            62:        xorl    %eax,%eax
        !            63:        movl    %ax,%ds
        !            64:        movl    %ax,%es
        !            65: 
        !            66:        /* step 1 load new descriptor table */
        !            67: 
        !            68:        .byte 0x2E,0x0F,1,0x16
        !            69:        .word   BIOSRELOC+0x4a  #GDTptr
        !            70:        # word aword cs lgdt GDTptr
        !            71: 
        !            72:        /* step 2 turn on protected mode */
        !            73: 
        !            74:        smsw    %ax
        !            75:        orb     $1,%al
        !            76:        lmsw    %ax
        !            77:        jmp     1f
        !            78:        nop
        !            79: 
        !            80:        /* step 3  reload segment descriptors */
        !            81: 
        !            82: 1:
        !            83:        xorl    %eax,%eax
        !            84:        movb    $0x10,%al
        !            85:        movl    %ax,%ds
        !            86:        movl    %ax,%es
        !            87:        movl    %ax,%ss
        !            88:        word
        !            89:        ljmp    $0x8,$ BIOSRELOC+0x50   /* would be nice if .-RELOC+0x7c00 worked */
        !            90: 
        !            91:  /* Global Descriptor Table contains three descriptors:
        !            92:   * 0x00: Null: not used
        !            93:   * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
        !            94:   * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
        !            95:   *            (overlays code)
        !            96:   */
        !            97: GDT:
        !            98: NullDesc:      .word   0,0,0,0 # null descriptor - not used
        !            99: CodeDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
        !           100:        .byte   0,0,0   # base at 0: (bits 23:0)
        !           101:        .byte   0x9f    # present/priv level 0/code/conforming/readable
        !           102:        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        !           103:        .byte   0       # base at 0: (bits 31:24)
        !           104: DataDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
        !           105:        .byte   0,0,0   # base at 0: (bits 23:0)
        !           106:        .byte   0x93    # present/priv level 0/data/expand-up/writeable
        !           107:        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        !           108:        .byte   0       # base at 0: (bits 31:24)
        !           109: 
        !           110: /* Global Descriptor Table pointer
        !           111:  *  contains 6-byte pointer information for LGDT
        !           112:  */
        !           113: GDTptr:        .word   0x17    # limit to three 8 byte selectors(null,code,data)
        !           114:        .long   BIOSRELOC+0x32  # GDT -- arrgh, gas again!
        !           115: 
        !           116:        /* step 4 relocate to final bootstrap address. */
        !           117: reloc:
        !           118:        movl    $ BIOSRELOC,%esi
        !           119:        movl    $ RELOC,%edi
        !           120:        movl    $512,%ecx
        !           121:        rep
        !           122:        movsb
        !           123:  movl $0x60000,%esp
        !           124:        pushl   $dodisk
        !           125:        ret
        !           126: 
        !           127:        /* step 5 load remaining 15 sectors off disk */
        !           128: dodisk:
        !           129:        movl    $ IO_WD1+wd_seccnt,%edx
        !           130:        movb    $ 15,%al
        !           131:        outb    %al,%dx
        !           132:        NOP
        !           133:        movl    $ IO_WD1+wd_sector,%edx
        !           134:        movb    $ 2,%al
        !           135:        outb    %al,%dx
        !           136:        NOP
        !           137:        #outb(wdc+wd_cyl_lo, (cyloffset & 0xff));
        !           138:        #outb(wdc+wd_cyl_hi, (cyloffset >> 8));
        !           139:        #outb(wdc+wd_sdh, WDSD_IBM | (unit << 4));
        !           140: 
        !           141:        movl    $ IO_WD1+wd_command,%edx
        !           142:        movb    $ WDCC_READ,%al
        !           143:        outb    %al,%dx
        !           144:        NOP
        !           145:        cld
        !           146: 
        !           147:        /* check to make sure controller is not busy and we have data ready */
        !           148: readblk:
        !           149:        movl    $ IO_WD1+wd_status,%edx
        !           150:        inb     %dx,%al
        !           151:        NOP
        !           152:        testb   $ WDCS_BUSY,%al
        !           153:        jnz readblk
        !           154:        testb   $ WDCS_DRQ,%al
        !           155:        jz readblk
        !           156: 
        !           157:        /* read a block into final position in memory */
        !           158: 
        !           159:        movl    $ IO_WD1+wd_data,%edx
        !           160:        movl    $ 256,%ecx
        !           161:        .byte 0x66,0xf2,0x6d    # rep insw
        !           162:        NOP
        !           163: 
        !           164:        /* need more blocks to be read in? */
        !           165: 
        !           166:        cmpl    $ RELOC+16*512-1,%edi
        !           167:        jl      readblk
        !           168: 
        !           169:        /* for clever bootstrap, dig out boot unit and cylinder */
        !           170:        
        !           171:        movl    $ IO_WD1+wd_cyl_lo,%edx
        !           172:        inb     %dx,%al
        !           173:        NOP
        !           174:        xorl    %ecx,%ecx
        !           175:        movb    %al,%cl
        !           176:        incl    %edx
        !           177:        inb     %dx,%al         /* cyl_hi */
        !           178:        NOP
        !           179:        movb    %al,%ch
        !           180:        pushl   %ecx            /* cyloffset */
        !           181: 
        !           182:        incl    %edx
        !           183:        xorl    %eax,%eax
        !           184:        inb     %dx,%al         /* sdh */
        !           185:        andb    $0x10,%al       /* isolate unit # bit */
        !           186:        shrb    $4,%al
        !           187:        pushl   %eax            /* unit */
        !           188: 
        !           189:        /* wd controller is major device 0 */
        !           190:        xorl    %eax,%eax
        !           191:        pushl   %eax            /* bootdev */
        !           192: 
        !           193:        /* sorry, no flags at this point! */
        !           194: 
        !           195:        pushl   $ start
        !           196:        ret     /* main (dev, unit, offset) */
        !           197: 
        !           198: ebootblkcode:
        !           199: 
        !           200:        /* remaining space usable for a disk label */
        !           201:        
        !           202:        .space  510-223         /* would be nice if .space 512-2-. worked */
        !           203:        .word   0xaa55          /* signature -- used by BIOS ROM */
        !           204: 
        !           205: ebootblk:                      /* MUST BE EXACTLY 0x200 BIG FOR SURE */

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