bios_disk.S revision 1.3
1 /* $NetBSD: bios_disk.S,v 1.3 1998/10/27 14:08:55 ws Exp $ */ 2 3 /* 4 * Ported to boot 386BSD by Julian Elischer (julian (at) tfs.com) Sept 1992 5 * 6 * Mach Operating System 7 * Copyright (c) 1992, 1991 Carnegie Mellon University 8 * All Rights Reserved. 9 * 10 * Permission to use, copy, modify and distribute this software and its 11 * documentation is hereby granted, provided that both the copyright 12 * notice and this permission notice appear in all copies of the 13 * software, derivative works or modified versions, and any portions 14 * thereof, and that both notices appear in supporting documentation. 15 * 16 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS" 17 * CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR 18 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE. 19 * 20 * Carnegie Mellon requests users of this software to return to 21 * 22 * Software Distribution Coordinator or Software.Distribution (at) CS.CMU.EDU 23 * School of Computer Science 24 * Carnegie Mellon University 25 * Pittsburgh PA 15213-3890 26 * 27 * any improvements or extensions that they make and grant Carnegie Mellon 28 * the rights to redistribute these changes. 29 */ 30 31 /* 32 Copyright 1988, 1989, 1990, 1991, 1992 33 by Intel Corporation, Santa Clara, California. 34 35 All Rights Reserved 36 37 Permission to use, copy, modify, and distribute this software and 38 its documentation for any purpose and without fee is hereby 39 granted, provided that the above copyright notice appears in all 40 copies and that both the copyright notice and this permission notice 41 appear in supporting documentation, and that the name of Intel 42 not be used in advertising or publicity pertaining to distribution 43 of the software without specific, written prior permission. 44 45 INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE 46 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, 47 IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR 48 CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM 49 LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT, 50 NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION 51 WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 52 */ 53 54 /* extracted from netbsd:sys/arch/i386/boot/bios.S */ 55 56 #include <machine/asm.h> 57 58 #define addr32 .byte 0x67 59 #define data32 .byte 0x66 60 61 /* 62 # BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory 63 # Call with %ah = 0x2 64 # %al = number of sectors 65 # %ch = cylinder 66 # %cl = sector 67 # %dh = head 68 # %dl = drive (0x80 for hard disk, 0x0 for floppy disk) 69 # %es:%bx = segment:offset of buffer 70 # Return: 71 # %al = 0x0 on success; err code on failure 72 */ 73 ENTRY(biosread) 74 pushl %ebp 75 movl %esp, %ebp 76 pushl %ebx 77 push %ecx 78 push %edx 79 push %esi 80 push %edi 81 82 movb 16(%ebp), %dh 83 movw 12(%ebp), %cx 84 xchgb %ch, %cl # cylinder; the highest 2 bits of cyl is in %cl 85 rorb $2, %cl 86 movb 20(%ebp), %al 87 orb %al, %cl 88 incb %cl # sector; sec starts from 1, not 0 89 movb 8(%ebp), %dl # device 90 movl 28(%ebp), %ebx # offset 91 # prot_to_real will set %es to BOOTSEG 92 93 call _C_LABEL(prot_to_real) # enter real mode 94 95 movb $0x2, %ah # subfunction 96 addr32 97 movb 24(%ebp), %al # number of sectors 98 int $0x13 99 setc %bl 100 101 data32 102 call _C_LABEL(real_to_prot) # back to protected mode 103 104 xorl %eax, %eax 105 movb %bl, %al # return value in %ax 106 107 pop %edi 108 pop %esi 109 pop %edx 110 pop %ecx 111 popl %ebx 112 popl %ebp 113 ret 114 115 /* 116 # 117 # get_diskinfo(): return a word that represents the 118 # max number of sectors and heads and drives for this device 119 # 120 */ 121 122 ENTRY(get_diskinfo) 123 pushl %ebp 124 movl %esp, %ebp 125 push %es 126 pushl %ebx 127 push %ecx 128 push %edx 129 push %esi 130 push %edi 131 132 movb 8(%ebp), %dl # diskinfo(drive #) 133 134 call _C_LABEL(prot_to_real) # enter real mode 135 136 movb $0x08, %ah # ask for disk info 137 int $0x13 138 jnc ok 139 140 /* 141 * Urk. Call failed. It is not supported for floppies by old BIOS's. 142 * Guess it's a 15-sector floppy. Initialize all the registers for 143 * documentation, although we only need head and sector counts. 144 */ 145 # subb %ah, %ah # %ax = 0 146 # movb %ah, %bh # %bh = 0 147 # movb $2, %bl # %bl bits 0-3 = drive type, 2 = 1.2M 148 # movb $79, %ch # max track 149 movb $15, %cl # max sector 150 movb $1, %dh # max head 151 # movb $1, %dl # # floppy drives installed 152 # es:di = parameter table 153 # carry = 0 154 155 ok: 156 data32 157 call _C_LABEL(real_to_prot) # back to protected mode 158 159 xorl %eax, %eax 160 161 /*form a longword representing all this gunk*/ 162 movb %dh, %ah # max head 163 andb $0x3f, %cl # mask of cylinder gunk 164 movb %cl, %al # max sector (and # sectors) 165 166 pop %edi 167 pop %esi 168 pop %edx 169 pop %ecx 170 popl %ebx 171 pop %es 172 popl %ebp 173 ret 174 175 /* 176 # int13_extension: check for availibility of int13 extensions. 177 */ 178 179 ENTRY(int13_extension) 180 pushl %ebp 181 movl %esp, %ebp 182 pushl %ebx 183 pushl %ecx 184 pushl %edx 185 pushl %esi 186 pushl %edi 187 188 movb 8(%ebp), %dl # drive # 189 movw $0x55aa, %bx 190 191 call _C_LABEL(prot_to_real) # enter real mode 192 193 movb $0x41, %ah # ask for disk info 194 int $0x13 195 setnc %dl 196 197 data32 198 CALL _C_LABEL(real_to_prot) # switch back 199 200 xorl %eax, %eax 201 movb %dl, %al # return value in %ax 202 203 cmpw $0xaa55, %bx 204 sete %dl 205 orb %dl, %al 206 207 andb $1, %cl 208 orb %cl, %al 209 210 popl %edi 211 popl %esi 212 popl %edx 213 popl %ecx 214 popl %ebx 215 popl %ebp 216 ret 217 218 /* 219 # BIOS call "INT 0x13 Function 0x42" to read sectors from disk into memory 220 # Call with %ah = 0x42 221 # %ds:%di = parameter block 222 # %dl = drive (0x80 for hard disk, 0x0 for floppy disk) 223 # Return: 224 # %al = 0x0 on success; err code on failure 225 */ 226 ENTRY(biosextread) 227 pushl %ebp 228 movl %esp, %ebp 229 pushl %ebx 230 push %ecx 231 push %edx 232 push %esi 233 push %edi 234 235 movb 8(%ebp), %dl # device 236 movl 12(%ebp), %esi # parameter block 237 238 call _C_LABEL(prot_to_real) # enter real mode 239 240 movb $0x42, %ah # subfunction 241 int $0x13 242 setc %bl 243 244 data32 245 call _C_LABEL(real_to_prot) # back to protected mode 246 247 xorl %eax, %eax 248 movb %bl, %al # return value in %ax 249 250 pop %edi 251 pop %esi 252 pop %edx 253 pop %ecx 254 popl %ebx 255 popl %ebp 256 ret 257
Indexes created Wed Oct 15 03:09:54 GMT 2025