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Annotation of Net2/arch/i386/stand/fdbootblk.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:  *     @(#)fdbootblk.c 7.2 (Berkeley) 5/4/91
        !            37:  */
        !            38: 
        !            39: /*
        !            40:  * fdbootblk.s:
        !            41:  *     Written 10/6/90 by William F. Jolitz
        !            42:  *     Initial block boot for AT/386 with typical stupid NEC controller
        !            43:  *     Works only with 3.5 inch diskettes that have 16 or greater sectors/side
        !            44:  *
        !            45:  *     Goal is to read in sucessive 7.5Kbytes of bootstrap to
        !            46:  *     execute.
        !            47:  *
        !            48:  *     No attempt is made to handle disk errors.
        !            49:  */
        !            50: /*#include "/sys/i386/isa/isa.h"
        !            51: #include "/sys/i386/isa/fdreg.h"*/
        !            52: #define        NOP     jmp 1f ; nop ; 1:
        !            53: #define BIOSRELOC      0x7c00
        !            54: #define        start   0x70400
        !            55: 
        !            56:        /* step 0 force descriptors to bottom of address space */
        !            57: 
        !            58:        .byte 0xfa,0xb8,0x30,0x00,0x8e,0xd0,0xbc,0x00,0x01 #ll fb
        !            59: 
        !            60:        xorl    %eax,%eax
        !            61:        movl    %ax,%ds
        !            62:        movl    %ax,%es
        !            63: 
        !            64:        /* step 1 load new descriptor table */
        !            65: 
        !            66:        .byte 0x2E,0x0F,1,0x16
        !            67:        .word   BIOSRELOC+0x4a  #GDTptr
        !            68:        # word aword cs lgdt GDTptr
        !            69: 
        !            70:        /* step 2 turn on protected mode */
        !            71: 
        !            72:        smsw    %ax
        !            73:        orb     $1,%al
        !            74:        lmsw    %ax
        !            75:        jmp     1f
        !            76:        nop
        !            77: 
        !            78:        /* step 3  reload segment descriptors */
        !            79: 
        !            80:  1:
        !            81:        xorl    %eax,%eax
        !            82:        movb    $0x10,%al
        !            83:        movl    %ax,%ds
        !            84:        movl    %ax,%es
        !            85:        movl    %ax,%ss
        !            86:        word
        !            87:        ljmp    $0x8,$ BIOSRELOC+0x59   /* would be nice if .-RELOC+0x7c00 worked */
        !            88: 
        !            89:  /* Global Descriptor Table contains three descriptors:
        !            90:   * 0x00: Null: not used
        !            91:   * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes
        !            92:   * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes
        !            93:   *            (overlays code)
        !            94:   */
        !            95: GDT:
        !            96: NullDesc:      .word   0,0,0,0 # null descriptor - not used
        !            97: CodeDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
        !            98:        .byte   0,0,0   # base at 0: (bits 23:0)
        !            99:        .byte   0x9f    # present/priv level 0/code/conforming/readable
        !           100:        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        !           101:        .byte   0       # base at 0: (bits 31:24)
        !           102: DataDesc:      .word   0xFFFF  # limit at maximum: (bits 15:0)
        !           103:        .byte   0,0,0   # base at 0: (bits 23:0)
        !           104:        .byte   0x93    # present/priv level 0/data/expand-up/writeable
        !           105:        .byte   0xcf    # page granular/default 32-bit/limit(bits 19:16)
        !           106:        .byte   0       # base at 0: (bits 31:24)
        !           107: 
        !           108: /* Global Descriptor Table pointer
        !           109:  *  contains 6-byte pointer information for LGDT
        !           110:  */
        !           111: GDTptr:        .word   0x17    # limit to three 8 byte selectors(null,code,data)
        !           112:        .long   BIOSRELOC+0x32  # GDT -- arrgh, gas again!
        !           113: readcmd: .byte 0xe6,0,0,0,0,2,18,0x1b,0xff
        !           114: 
        !           115:        /* step 4 relocate to final bootstrap address. */
        !           116: reloc:
        !           117:        movl    $ BIOSRELOC,%esi
        !           118:        movl    $ RELOC,%edi
        !           119:        movl    $512,%ecx
        !           120:        rep
        !           121:        movsb
        !           122:        pushl   $dodisk
        !           123:        ret
        !           124: 
        !           125:        /* step 5 load remaining 15 sectors off disk */
        !           126: dodisk:
        !           127:        movl    $0x70200,%edi
        !           128:        xorl    %ebx,%ebx
        !           129:        incb    %bl
        !           130:        incb    %bl
        !           131:        movb    $0x20,%al       # do a eoi
        !           132:        outb    %al,$0x20
        !           133: 
        !           134:        NOP
        !           135:        movb    $0x07,%al
        !           136:        outb    %al,$0x21
        !           137:        NOP
        !           138:  8:
        !           139:        movb    %bl,readcmd+4
        !           140:        movl    %edi,%ecx
        !           141: 
        !           142:        /* Set read/write bytes */
        !           143:        xorl    %edx,%edx
        !           144:        movb    $0x0c,%dl       # outb(0xC,0x46); outb(0xB,0x46);
        !           145:        movb    $0x46,%al
        !           146:        outb    %al,%dx
        !           147:        NOP
        !           148:        decb    %dx
        !           149:        outb    %al,%dx
        !           150: 
        !           151:        /* Send start address */
        !           152:        movb    $0x04,%dl       # outb(0x4, addr);
        !           153:        movb    %cl,%al
        !           154:        outb    %al,%dx
        !           155:        NOP
        !           156:        movb    %ch,%al         # outb(0x4, addr>>8);
        !           157:        outb    %al,%dx
        !           158:        NOP
        !           159:        rorl    $8,%ecx         # outb(0x81, addr>>16);
        !           160:        movb    %ch,%al
        !           161:        outb    %al,$0x81
        !           162:        NOP
        !           163: 
        !           164:        /* Send count */
        !           165:        movb    $0x05,%dl       # outb(0x5, 0);
        !           166:        xorl    %eax,%eax
        !           167:        outb    %al,%dx
        !           168:        NOP
        !           169:        movb    $2,%al          # outb(0x5,2);
        !           170:        outb    %al,%dx
        !           171:        NOP
        !           172: 
        !           173:        /* set channel 2 */
        !           174:        # movb  $2,%al          # outb(0x0A,2);
        !           175:        outb    %al,$0x0A
        !           176:        NOP
        !           177: 
        !           178:        /* issue read command to fdc */
        !           179:        movw    $0x3f4,%dx
        !           180:        movl    $readcmd,%esi
        !           181:        xorl    %ecx,%ecx
        !           182:        movb    $9,%cl
        !           183: 
        !           184:  2:    inb     %dx,%al
        !           185:        NOP
        !           186:        testb   $0x80,%al
        !           187:        jz 2b
        !           188: 
        !           189:        incb    %dx
        !           190:        movl    (%esi),%al
        !           191:        outb    %al,%dx
        !           192:        NOP
        !           193:        incl    %esi
        !           194:        decb    %dx
        !           195:        loop     2b
        !           196: 
        !           197:        /* watch the icu looking for an interrupt signalling completion */
        !           198:        xorl    %edx,%edx
        !           199:        movb    $0x20,%dl
        !           200:  2:    movb    $0xc,%al
        !           201:        outb    %al,%dx
        !           202:        NOP
        !           203:        inb     %dx,%al
        !           204:        NOP
        !           205:        andb    $0x7f,%al
        !           206:        cmpb    $6,%al
        !           207:        jne     2b
        !           208:        movb    $0x20,%al       # do a eoi
        !           209:        outb    %al,%dx
        !           210:        NOP
        !           211: 
        !           212:        movl    $0x3f4,%edx
        !           213:        xorl    %ecx,%ecx
        !           214:        movb    $7,%cl
        !           215:  2:    inb     %dx,%al
        !           216:        NOP
        !           217:        andb    $0xC0,%al
        !           218:        cmpb    $0xc0,%al
        !           219:        jne     2b
        !           220:        incb    %dx
        !           221:        inb     %dx,%al
        !           222:        decb    %dx
        !           223:        loop    2b
        !           224: 
        !           225:        /* extract the status bytes after the read. must we do this? */
        !           226:        addw    $0x200,%edi     # next addr to load to
        !           227:        incb    %bl
        !           228:        cmpb    $16,%bl
        !           229:        jle     8b
        !           230:        
        !           231:        /* for clever bootstrap, dig out boot unit and cylinder */
        !           232:        pushl   $0
        !           233:        pushl   $0
        !           234:        
        !           235:        /* fd controller is major device 2 */
        !           236:        pushl   $2      /* dev */
        !           237: 
        !           238:        /* sorry, no flags at this point! */
        !           239: 
        !           240:        pushl $ start
        !           241:        ret     /* main (dev, unit, off) */
        !           242: 
        !           243: ebootblkcode:
        !           244: 
        !           245:        /* remaining space usable for a disk label */
        !           246:        
        !           247:        .space  510-310         /* would be nice if .space 512-2-. worked */
        !           248:        .word   0xaa55          /* signature -- used by BIOS ROM */
        !           249: 
        !           250: ebootblk:                      /* MUST BE EXACTLY 0x200 BIG FOR SURE */

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