projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| d0f59f84 | 1 | /*- |
| 2ae79493 KB |
2 | * Copyright (c) 1990, 1993 |
| 3 | * The Regents of the University of California. All rights reserved. | |
| d0f59f84 WN |
4 | * |
| 5 | * This code is derived from software contributed to Berkeley by | |
| 6 | * William Jolitz. | |
| 7 | * | |
| 8 | * %sccs.include.redist.c% | |
| 9 | * | |
| 2ae79493 | 10 | * @(#)wdbootblk.c 8.1 (Berkeley) %G% |
| d0f59f84 WN |
11 | */ |
| 12 | ||
| 13 | /* | |
| 14 | * wdbootblk.s: | |
| 15 | * Written 7/6/90 by William F. Jolitz | |
| 16 | * Initial block boot for AT/386 with typical Western Digital | |
| 17 | * WD 1002-WA2 (or upwards compatable). Works either as | |
| 18 | * first and sole partition bootstrap, or as loaded by a | |
| 19 | * earlier BIOS boot when on an inner partition of the disk. | |
| 20 | * | |
| 21 | * Goal is to read in sucessive 7.5Kbytes of bootstrap to | |
| 22 | * execute. | |
| 23 | * | |
| 24 | * No attempt is made to handle disk errors. | |
| 25 | */ | |
| 38a01dbe KB |
26 | |
| 27 | #include <i386/isa/isa.h> | |
| 28 | #include <i386/isa/wdreg.h> | |
| 29 | ||
| d0f59f84 WN |
30 | #define NOP jmp 1f ; nop ; 1: |
| 31 | #define BIOSRELOC 0x7c00 | |
| 32 | #define start 0x70400 | |
| 33 | ||
| 34 | /* step 0 force descriptors to bottom of address space */ | |
| 35 | ||
| 36 | .byte 0xfa,0xb8,0x30,0x00,0x8e,0xd0,0xbc,0x00,0x01 #ll fb | |
| 37 | ||
| 38 | xorl %eax,%eax | |
| 39 | movl %ax,%ds | |
| 40 | movl %ax,%es | |
| 41 | ||
| 42 | /* step 1 load new descriptor table */ | |
| 43 | ||
| 44 | .byte 0x2E,0x0F,1,0x16 | |
| 45 | .word BIOSRELOC+0x4a #GDTptr | |
| 46 | # word aword cs lgdt GDTptr | |
| 47 | ||
| 48 | /* step 2 turn on protected mode */ | |
| 49 | ||
| 50 | smsw %ax | |
| 51 | orb $1,%al | |
| 52 | lmsw %ax | |
| 53 | jmp 1f | |
| 54 | nop | |
| 55 | ||
| 56 | /* step 3 reload segment descriptors */ | |
| 57 | ||
| 58 | 1: | |
| 59 | xorl %eax,%eax | |
| 60 | movb $0x10,%al | |
| 61 | movl %ax,%ds | |
| 62 | movl %ax,%es | |
| 63 | movl %ax,%ss | |
| 64 | word | |
| 65 | ljmp $0x8,$ BIOSRELOC+0x50 /* would be nice if .-RELOC+0x7c00 worked */ | |
| 66 | ||
| 67 | /* Global Descriptor Table contains three descriptors: | |
| 68 | * 0x00: Null: not used | |
| 69 | * 0x08: Code: code segment starts at 0 and extents for 4 gigabytes | |
| 70 | * 0x10: Data: data segment starts at 0 and extends for 4 gigabytes | |
| 71 | * (overlays code) | |
| 72 | */ | |
| 73 | GDT: | |
| 74 | NullDesc: .word 0,0,0,0 # null descriptor - not used | |
| 75 | CodeDesc: .word 0xFFFF # limit at maximum: (bits 15:0) | |
| 76 | .byte 0,0,0 # base at 0: (bits 23:0) | |
| 77 | .byte 0x9f # present/priv level 0/code/conforming/readable | |
| 78 | .byte 0xcf # page granular/default 32-bit/limit(bits 19:16) | |
| 79 | .byte 0 # base at 0: (bits 31:24) | |
| 80 | DataDesc: .word 0xFFFF # limit at maximum: (bits 15:0) | |
| 81 | .byte 0,0,0 # base at 0: (bits 23:0) | |
| 82 | .byte 0x93 # present/priv level 0/data/expand-up/writeable | |
| 83 | .byte 0xcf # page granular/default 32-bit/limit(bits 19:16) | |
| 84 | .byte 0 # base at 0: (bits 31:24) | |
| 85 | ||
| 86 | /* Global Descriptor Table pointer | |
| 87 | * contains 6-byte pointer information for LGDT | |
| 88 | */ | |
| 89 | GDTptr: .word 0x17 # limit to three 8 byte selectors(null,code,data) | |
| 90 | .long BIOSRELOC+0x32 # GDT -- arrgh, gas again! | |
| 91 | ||
| 92 | /* step 4 relocate to final bootstrap address. */ | |
| 93 | reloc: | |
| 94 | movl $ BIOSRELOC,%esi | |
| 95 | movl $ RELOC,%edi | |
| 96 | movl $512,%ecx | |
| 97 | rep | |
| 98 | movsb | |
| 99 | movl $0x60000,%esp | |
| 100 | pushl $dodisk | |
| 101 | ret | |
| 102 | ||
| 103 | /* step 5 load remaining 15 sectors off disk */ | |
| 104 | dodisk: | |
| 105 | movl $ IO_WD1+wd_seccnt,%edx | |
| 106 | movb $ 15,%al | |
| 107 | outb %al,%dx | |
| 108 | NOP | |
| 109 | movl $ IO_WD1+wd_sector,%edx | |
| 110 | movb $ 2,%al | |
| 111 | outb %al,%dx | |
| 112 | NOP | |
| 113 | #outb(wdc+wd_cyl_lo, (cyloffset & 0xff)); | |
| 114 | #outb(wdc+wd_cyl_hi, (cyloffset >> 8)); | |
| 115 | #outb(wdc+wd_sdh, WDSD_IBM | (unit << 4)); | |
| 116 | ||
| 117 | movl $ IO_WD1+wd_command,%edx | |
| 118 | movb $ WDCC_READ,%al | |
| 119 | outb %al,%dx | |
| 120 | NOP | |
| 121 | cld | |
| 122 | ||
| 123 | /* check to make sure controller is not busy and we have data ready */ | |
| 124 | readblk: | |
| 125 | movl $ IO_WD1+wd_status,%edx | |
| 126 | inb %dx,%al | |
| 127 | NOP | |
| 128 | testb $ WDCS_BUSY,%al | |
| 129 | jnz readblk | |
| 130 | testb $ WDCS_DRQ,%al | |
| 131 | jz readblk | |
| 132 | ||
| 133 | /* read a block into final position in memory */ | |
| 134 | ||
| 135 | movl $ IO_WD1+wd_data,%edx | |
| 136 | movl $ 256,%ecx | |
| 137 | .byte 0x66,0xf2,0x6d # rep insw | |
| 138 | NOP | |
| 139 | ||
| 140 | /* need more blocks to be read in? */ | |
| 141 | ||
| 142 | cmpl $ RELOC+16*512-1,%edi | |
| 143 | jl readblk | |
| 144 | ||
| 145 | /* for clever bootstrap, dig out boot unit and cylinder */ | |
| 146 | ||
| 147 | movl $ IO_WD1+wd_cyl_lo,%edx | |
| 148 | inb %dx,%al | |
| 149 | NOP | |
| 150 | xorl %ecx,%ecx | |
| 151 | movb %al,%cl | |
| 152 | incl %edx | |
| 153 | inb %dx,%al /* cyl_hi */ | |
| 154 | NOP | |
| 155 | movb %al,%ch | |
| 156 | pushl %ecx /* cyloffset */ | |
| 157 | ||
| 158 | incl %edx | |
| 159 | xorl %eax,%eax | |
| 160 | inb %dx,%al /* sdh */ | |
| 161 | andb $0x10,%al /* isolate unit # bit */ | |
| 162 | shrb $4,%al | |
| 163 | pushl %eax /* unit */ | |
| 164 | ||
| 165 | /* wd controller is major device 0 */ | |
| 166 | xorl %eax,%eax | |
| 167 | pushl %eax /* bootdev */ | |
| 168 | ||
| 169 | /* sorry, no flags at this point! */ | |
| 170 | ||
| 171 | pushl $ start | |
| 172 | ret /* main (dev, unit, offset) */ | |
| 173 | ||
| 174 | ebootblkcode: | |
| 175 | ||
| 176 | /* remaining space usable for a disk label */ | |
| 177 | ||
| 178 | .space 510-223 /* would be nice if .space 512-2-. worked */ | |
| 179 | .word 0xaa55 /* signature -- used by BIOS ROM */ | |
| 180 | ||
| 181 | ebootblk: /* MUST BE EXACTLY 0x200 BIG FOR SURE */ |