1 /* $NetBSD: bios_disk.S,v 1.23 2022/09/10 12:14:17 rillig 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 /* 59 * BIOS call "INT 0x13 Function 0x0" to reset the disk subsystem 60 * Call with %ah = 0x0 61 * %dl = drive (0x80 for hard disk, 0x0 for floppy disk) 62 * Return: 63 * %al = 0x0 on success; err code on failure 64 */ 65 ENTRY(biosdisk_reset) 66 pusha 67 68 movb %al, %dl # device 69 70 call _C_LABEL(prot_to_real) # enter real mode 71 .code16 72 73 movb $0x0, %ah # subfunction 74 int $0x13 75 setc %bl 76 movb %ah, %bh # save error code 77 78 calll _C_LABEL(real_to_prot) # back to protected mode 79 .code32 80 81 movzwl %bx, %eax # return value in %eax 82 movl %eax, 28(%esp) 83 84 popa 85 ret 86 87 /* 88 * BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory 89 * Call with %ah = 0x2 90 * %al = number of sectors 91 * %ch = cylinder 92 * %cl = sector 93 * %dh = head 94 * %dl = drive (0x80 for hard disk, 0x0 for floppy disk) 95 * %es:%bx = segment:offset of buffer 96 * Return: 97 * %al = 0x0 on success; err code on failure 98 * 99 * biosdisk_read(dev, cyl, head, sect, count, buff_addr); 100 * 101 * Note: On failure, you must reset the disk with biosdisk_reset() before 102 * sending another command. 103 */ 104 ENTRY(biosdisk_read) 105 pusha 106 107 movb 44(%esp), %dh 108 movw 40(%esp), %cx 109 xchgb %ch, %cl # cylinder; the highest 2 bits of cyl is in %cl 110 rorb $2, %cl 111 movb 48(%esp), %al 112 orb %al, %cl 113 incb %cl # sector; sec starts from 1, not 0 114 movb 36(%esp), %dl # device 115 movl 56(%esp), %ebx # buffer address (may be >64k) 116 movb 52(%esp), %al # number of sectors 117 118 call _C_LABEL(prot_to_real) # enter real mode 119 .code16 120 121 push %bx 122 shrl $4, %ebx # max segment 123 mov %ds, %si 124 add %si, %bx 125 mov %bx, %es # %es:%bx now valid buffer address 126 pop %bx 127 and $0xf, %bx # and min offset - to avoid overrun 128 129 movb $0x2, %ah # subfunction 130 int $0x13 131 setc %al # error code is in %ah 132 133 calll _C_LABEL(real_to_prot) # back to protected mode 134 .code32 135 136 andl $0x0000FFFF, %eax # Some bioses set high bits in %eax 137 # on success, interfering with our 138 # return value. Clear those out. 139 movl %eax, 28(%esp) 140 141 popa 142 ret 143 144 /* 145 * biosdisk_getinfo(int dev): return a word that represents the 146 * max number of sectors, heads and cylinders for this device 147 */ 148 ENTRY(biosdisk_getinfo) 149 push %es 150 pusha 151 152 movb %al, %dl # diskinfo(drive #) 153 154 call _C_LABEL(prot_to_real) # enter real mode 155 .code16 156 157 push %dx # save drive # 158 movb $0x08, %ah # ask for disk info 159 int $0x13 160 pop %bx # restore drive # 161 jnc ok 162 163 testb $0x80, %bl # is it a hard disk? 164 jnz ok 165 166 /* 167 * Urk. Call failed. It is not supported for floppies by old BIOS's. 168 * Guess it's a 15-sector floppy. Initialize all the registers for 169 * documentation, although we only need head and sector counts. 170 */ 171 xorw %ax, %ax # set status to success 172 # movb %ah, %bh # %bh = 0 173 # movb $2, %bl # %bl bits 0-3 = drive type, 2 = 1.2M 174 movb $79, %ch # max track 175 movb $15, %cl # max sector 176 movb $1, %dh # max head 177 # movb $1, %dl # # floppy drives installed 178 # es:di = parameter table 179 # carry = 0 180 181 ok: 182 calll _C_LABEL(real_to_prot) # back to protected mode 183 .code32 184 185 /* form a longword representing all this gunk */ 186 shrl $8, %eax # clear unnecessary bits 187 shll $24, %eax 188 shll $16, %ecx # do the same for %ecx 189 shrl $8, %ecx 190 movb %dh, %cl # max head 191 orl %ecx, %eax # return value in %eax 192 movl %eax, 28(%esp) 193 194 popa 195 pop %es 196 ret 197 198 /* 199 * int biosdisk_int13ext(int dev): 200 * check for availability of int13 extensions. 201 */ 202 ENTRY(biosdisk_int13ext) 203 pusha 204 205 movb %al, %dl # drive # 206 movw $0x55aa, %bx 207 208 call _C_LABEL(prot_to_real) # enter real mode 209 .code16 210 211 movb $0x41, %ah # ask for disk info 212 int $0x13 213 setnc %dl 214 215 calll _C_LABEL(real_to_prot) # switch back 216 .code32 217 218 movzbl %dl, %eax # return value in %eax 219 220 cmpw $0xaa55, %bx 221 sete %dl 222 andb %dl, %al 223 224 andb %cl, %al 225 movl %eax, 28(%esp) 226 227 popa 228 ret 229 230 /* 231 * BIOS call "INT 0x13 Function 0x42" to read sectors from disk into memory 232 * Call with %ah = 0x42 233 * %ds:%si = parameter block (data buffer address 234 * must be a real mode physical address). 235 * %dl = drive (0x80 for hard disk, 0x0 for floppy disk) 236 * Return: 237 * %al = 0x0 on success; err code on failure 238 */ 239 ENTRY(biosdisk_extread) 240 pusha 241 242 movl %edx, %esi # parameter block 243 movb %al, %dl # device 244 245 call _C_LABEL(prot_to_real) # enter real mode 246 .code16 247 248 push %ds 249 movl %esi, %eax 250 shrl $4, %eax 251 movw %ds, %bx 252 addw %bx, %ax 253 movw %ax, %ds 254 andw $0xf, %si 255 256 movb $0x42, %ah # subfunction 257 int $0x13 258 setc %bl 259 movb %ah, %bh # save error code 260 pop %ds 261 262 calll _C_LABEL(real_to_prot) # back to protected mode 263 .code32 264 265 movzwl %bx, %eax # return value in %eax 266 movl %eax, 28(%esp) 267 268 popa 269 ret 270 271 ENTRY(biosdisk_getextinfo) 272 pusha 273 274 movl %edx, %esi # parameter block 275 movb %al, %dl # device 276 277 call _C_LABEL(prot_to_real) # enter real mode 278 .code16 279 280 push %ds 281 movl %esi, %eax 282 shrl $4, %eax 283 andw $0xf, %si 284 movw %ds, %bx 285 addw %bx, %ax 286 movw %ax, %ds 287 288 movb $0x48, %ah # subfunction 289 int $0x13 290 setc %bl 291 pop %ds 292 293 calll _C_LABEL(real_to_prot) # back to protected mode 294 .code32 295 296 movzbl %bl, %eax # return value in %eax 297 movl %eax, 28(%esp) 298 299 popa 300 ret 301
Indexes created Sat Sep 20 22:09:52 GMT 2025