wok annotate BootProg/stuff/boot32.asm @ rev 25485

BootProg/fat32: active fat support
author Pascal Bellard <pascal.bellard@slitaz.org>
date Tue Nov 01 16:13:12 2022 +0000 (18 months ago)
parents 4c101652eb90
children f7324cde07d7
rev   line source
pascal@24476 1 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 2 ;; ;;
pascal@24476 3 ;; "BootProg" Loader v 1.5 by Alexey Frunze (c) 2000-2015 ;;
pascal@24476 4 ;; 2-clause BSD license. ;;
pascal@24476 5 ;; ;;
pascal@24476 6 ;; ;;
pascal@24476 7 ;; How to Compile: ;;
pascal@24476 8 ;; ~~~~~~~~~~~~~~~ ;;
pascal@24476 9 ;; nasm boot32.asm -f bin -o boot32.bin ;;
pascal@24476 10 ;; ;;
pascal@24476 11 ;; ;;
pascal@24476 12 ;; Features: ;;
pascal@24476 13 ;; ~~~~~~~~~ ;;
pascal@24535 14 ;; - FAT32 supported using BIOS int 13h function 42h (IOW, it will only ;;
pascal@24535 15 ;; work with modern BIOSes supporting HDDs bigger than 8 GB) ;;
pascal@24476 16 ;; ;;
pascal@24476 17 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
pascal@24476 18 ;; from the root directory of a disk and transfers control to it ;;
pascal@24476 19 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
pascal@25460 20 ;; Its maximum size can be up to 637KB without Extended BIOS Data area. ;;
pascal@24476 21 ;; ;;
pascal@24476 22 ;; - Prints an error if the file isn't found or couldn't be read ;;
pascal@24476 23 ;; ("File not found" or "Read error") ;;
pascal@24476 24 ;; and waits for a key to be pressed, then executes the Int 19h ;;
pascal@24476 25 ;; instruction and lets the BIOS continue bootstrap. ;;
pascal@24476 26 ;; ;;
pascal@24476 27 ;; ;;
pascal@24476 28 ;; Known Bugs: ;;
pascal@24476 29 ;; ~~~~~~~~~~~ ;;
pascal@24476 30 ;; - All bugs are fixed as far as I know. The boot sector has been tested ;;
pascal@24476 31 ;; on my HDD and an 8GB USB stick. ;;
pascal@24476 32 ;; ;;
pascal@24476 33 ;; ;;
pascal@24476 34 ;; Memory Layout: ;;
pascal@24476 35 ;; ~~~~~~~~~~~~~~ ;;
pascal@24476 36 ;; The diagram below shows the typical memory layout. The actual location ;;
pascal@24476 37 ;; of the boot sector and its stack may be lower than A0000H if the BIOS ;;
pascal@24476 38 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
pascal@24476 39 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
pascal@24476 40 ;; ;;
pascal@24476 41 ;; physical address ;;
pascal@24476 42 ;; +------------------------+ 00000H ;;
pascal@24476 43 ;; | Interrupt Vector Table | ;;
pascal@24476 44 ;; +------------------------+ 00400H ;;
pascal@24476 45 ;; | BIOS Data Area | ;;
pascal@24476 46 ;; +------------------------+ 00500H ;;
pascal@24476 47 ;; | PrtScr Status / Unused | ;;
pascal@24476 48 ;; +------------------------+ 00600H ;;
pascal@24476 49 ;; | Loaded Image | ;;
pascal@24476 50 ;; +------------------------+ nnnnnH ;;
pascal@24476 51 ;; | Available Memory | ;;
pascal@25460 52 ;; +------------------------+ A0000H - 1KB ;;
pascal@24476 53 ;; | Boot Sector | ;;
pascal@25460 54 ;; +------------------------+ A0000H - 0.5KB ;;
pascal@25460 55 ;; | 0.5KB Boot Stack | ;;
pascal@24476 56 ;; +------------------------+ A0000H ;;
pascal@24476 57 ;; | Video RAM | ;;
pascal@24476 58 ;; ;;
pascal@24476 59 ;; ;;
pascal@24476 60 ;; Boot Image Startup (register values): ;;
pascal@24476 61 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
pascal@24945 62 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
pascal@25454 63 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
pascal@24476 64 ;; cs:ip = program entry point ;;
pascal@24476 65 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
pascal@24476 66 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
pascal@24476 67 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
pascal@24476 68 ;; cs:ip and ss:sp depends on EXE header ;;
pascal@24476 69 ;; Magic numbers: ;;
pascal@24476 70 ;; si = 16381 (prime number 2**14-3) ;;
pascal@24476 71 ;; di = 32749 (prime number 2**15-19) ;;
pascal@24476 72 ;; bp = 65521 (prime number 2**16-15) ;;
pascal@24476 73 ;; The magic numbers let the program know whether it has been loaded by ;;
pascal@24476 74 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
pascal@24476 75 ;; metal and MS-DOS programs. ;;
pascal@24945 76 ;; The command line contains no arguments. ;;
pascal@24476 77 ;; ;;
pascal@24476 78 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 79
pascal@24491 80 %define bx(label) bx+label-boot
pascal@25449 81 %define si(label) si+label-boot
pascal@25485 82 ExtraBootSector equ 1
pascal@25449 83 ClusterMask equ 1 ; +9 bytes
pascal@25460 84 NullEntryCheck equ 1 ; +5 bytes
pascal@25485 85 CheckAttrib equ 1 ; +6 bytes
pascal@25485 86 NonMirroredFATs equ 1 ; +18 bytes
pascal@25449 87 ReadRetry equ 1 ; +7 bytes
pascal@25458 88 LBA48bits equ 1 ; +15 bytes
pascal@25485 89 CHSsupport equ 1 ; +27 bytes max 16MB, 32MB or 8GB
pascal@25485 90 CHSupTo32MB equ 1 ; +6 bytes
pascal@25485 91 CHSupTo8GB equ 1 ; +14 bytes
pascal@25485 92 SectorOf512Bytes equ 0 ; -5 bytes
pascal@25458 93 Always2FATs equ 0 ; -4 bytes
pascal@24491 94
pascal@24476 95 [BITS 16]
pascal@24476 96
pascal@24478 97 ImageLoadSeg equ 60h ; <=07Fh because of "push byte ImageLoadSeg" instructions
pascal@25460 98 StackSize equ 512
pascal@24476 99
pascal@24476 100 [SECTION .text]
pascal@24476 101 [ORG 0]
pascal@24476 102
pascal@24476 103 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 104 ;; Boot sector starts here ;;
pascal@24476 105 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 106
pascal@24491 107 boot:
pascal@25458 108 DriveNumber equ boot+0
pascal@25458 109 HiLBA equ boot+2
pascal@24476 110 jmp short start ; MS-DOS/Windows checks for this jump
pascal@24476 111 nop
pascal@24476 112 bsOemName DB "BootProg" ; 0x03
pascal@24476 113
pascal@24476 114 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 115 ;; BPB1 starts here ;;
pascal@24476 116 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 117
pascal@24479 118 bpbBytesPerSector DW 0 ; 0x0B
pascal@24479 119 bpbSectorsPerCluster DB 0 ; 0x0D
pascal@24479 120 bpbReservedSectors DW 0 ; 0x0E
pascal@24479 121 bpbNumberOfFATs DB 0 ; 0x10
pascal@24479 122 bpbRootEntries DW 0 ; 0x11
pascal@24479 123 bpbTotalSectors DW 0 ; 0x13
pascal@24479 124 bpbMedia DB 0 ; 0x15
pascal@24479 125 bpbSectorsPerFAT DW 0 ; 0x16
pascal@24479 126 bpbSectorsPerTrack DW 0 ; 0x18
pascal@24479 127 bpbHeadsPerCylinder DW 0 ; 0x1A
pascal@24479 128 bpbHiddenSectors DD 0 ; 0x1C
pascal@24479 129 bpbTotalSectorsBig DD 0 ; 0x20
pascal@24476 130
pascal@24476 131 ;;;;;;;;;;;;;;;;;;;;
pascal@24476 132 ;; BPB1 ends here ;;
pascal@24476 133 ;;;;;;;;;;;;;;;;;;;;
pascal@24476 134
pascal@24476 135 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 136 ;; BPB2 starts here ;;
pascal@24476 137 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 138
pascal@24479 139 bsSectorsPerFAT32 DD 0 ; 0x24
pascal@24479 140 bsExtendedFlags DW 0 ; 0x28
pascal@24479 141 bsFSVersion DW 0 ; 0x2A
pascal@24479 142 bsRootDirectoryClusterNo DD 0 ; 0x2C
pascal@24479 143 bsFSInfoSectorNo DW 0 ; 0x30
pascal@24479 144 bsBackupBootSectorNo DW 0 ; 0x32
pascal@24479 145 bsreserved times 12 DB 0 ; 0x34
pascal@24479 146 bsDriveNumber DB 0 ; 0x40
pascal@24479 147 bsreserved1 DB 0 ; 0x41
pascal@24479 148 bsExtendedBootSignature DB 0 ; 0x42
pascal@24479 149 bsVolumeSerialNumber DD 0 ; 0x43
pascal@25458 150 bsVolumeLabel times 11 DB " " ; 0x47 "NO NAME "
pascal@25458 151 bsFileSystemName times 8 DB " " ; 0x52 "FAT32 "
pascal@24476 152
pascal@24476 153 ;;;;;;;;;;;;;;;;;;;;
pascal@24476 154 ;; BPB2 ends here ;;
pascal@24476 155 ;;;;;;;;;;;;;;;;;;;;
pascal@24476 156
pascal@24476 157 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 158 ;; Boot sector code starts here ;;
pascal@24476 159 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 160
pascal@24476 161 start:
pascal@24476 162 cld
pascal@24476 163
pascal@24476 164 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 165 ;; How much RAM is there? ;;
pascal@24476 166 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 167
pascal@24476 168 int 12h ; get conventional memory size (in KBs)
pascal@25460 169 dec ax ; reserve 1K bytes for the code and the stack
pascal@24525 170 mov cx, 106h
pascal@24525 171 shl ax, cl ; and convert it to 16-byte paragraphs
pascal@24476 172
pascal@24476 173 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 174 ;; Reserve memory for the boot sector and its stack ;;
pascal@24476 175 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 176
pascal@24525 177 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
pascal@25485 178 %if ExtraBootSector == 0
pascal@24525 179 mov ss, ax
pascal@24525 180 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
pascal@25485 181 %endif
pascal@24476 182
pascal@24476 183 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 184 ;; Copy ourselves to top of memory ;;
pascal@24476 185 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 186
pascal@24476 187 mov si, 7C00h
pascal@24476 188 xor di, di
pascal@24476 189 mov ds, di
pascal@25449 190 push es
pascal@25449 191 mov [si(DriveNumber)], dx ; store BIOS boot drive number
pascal@24478 192 rep movsw
pascal@24476 193
pascal@24476 194 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 195 ;; Jump to the copy ;;
pascal@24476 196 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 197
pascal@25450 198 push byte main
pascal@25485 199 push es
pascal@25485 200 pop ds
pascal@24476 201 retf
pascal@24476 202
pascal@24476 203 main:
pascal@25449 204 xor ebx, ebx
pascal@25485 205 %if ExtraBootSector != 0
pascal@25485 206 add al, 32
pascal@25485 207 mov es, ax
pascal@25485 208 mov eax, [bx(bpbHiddenSectors)]
pascal@25485 209 inc eax
pascal@25485 210 %if LBA48bits != 0
pascal@25485 211 mov [bx(HiLBA)], bx
pascal@25485 212 %endif
pascal@25485 213 call ReadSectorBoot
pascal@25485 214 push ds
pascal@25485 215 pop ss
pascal@25485 216 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
pascal@25485 217 %endif
pascal@24476 218
pascal@25449 219 %if ClusterMask != 0
pascal@24491 220 and byte [bx(bsRootDirectoryClusterNo+3)], 0Fh ; mask cluster value
pascal@25449 221 %endif
pascal@24491 222 mov esi, [bx(bsRootDirectoryClusterNo)] ; esi=cluster # of root dir
pascal@24476 223
pascal@24478 224 push byte ImageLoadSeg
pascal@24478 225 pop es
pascal@25449 226
pascal@25449 227 RootDirReadContinue:
pascal@25458 228 call ReadClusterSector ; read one sector of the root dir
pascal@24476 229
pascal@24476 230 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 231 ;; Look for the COM/EXE file to load and run ;;
pascal@24476 232 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 233
pascal@24476 234 xor di, di ; es:di -> root entries array
pascal@24476 235
pascal@24476 236 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24478 237 ;; Looks for a file/dir by its name ;;
pascal@24476 238 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24478 239 ;; Input: DS:SI -> file name (11 chars) ;;
pascal@24478 240 ;; ES:DI -> root directory array ;;
pascal@24525 241 ;; BP = paragraphs in sector ;;
pascal@24476 242 ;; Output: ESI = cluster number ;;
pascal@24476 243 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 244
pascal@24476 245 FindNameCycle:
pascal@25449 246 %if NullEntryCheck != 0
pascal@24525 247 cmp byte [es:di], bh
pascal@24478 248 je ErrFind ; end of root directory (NULL entry found)
pascal@25449 249 %endif
pascal@24478 250 pusha
pascal@25454 251 mov cl, NameLength
pascal@24525 252 mov si, ProgramName ; ds:si -> program name
pascal@24476 253 repe cmpsb
pascal@25467 254 %if CheckAttrib != 0
pascal@25467 255 VolumeLabel equ 8
pascal@25467 256 SubDirectory equ 10h
pascal@25467 257 jnz SkipFindName
pascal@25467 258 test byte [es:di], VolumeLabel+SubDirectory
pascal@25467 259 SkipFindName:
pascal@25467 260 %endif
pascal@24525 261 je FindNameFound
pascal@24478 262 popa
pascal@24525 263 add di, byte 32
pascal@24476 264 dec bp
pascal@24476 265 dec bp
pascal@24476 266 jnz FindNameCycle ; next root entry
pascal@25458 267 loop RootDirReadContinue ; next sector in cluster
pascal@25458 268 cmp esi, 0FFFFFF6h ; carry=0 if last cluster, and carry=1 otherwise
pascal@25458 269 jnc RootDirReadContinue ; continue to the next root dir cluster
pascal@24478 270 ErrFind:
pascal@24478 271 call Error ; end of root directory (dir end reached)
pascal@24476 272 db "File not found."
pascal@24476 273 FindNameFound:
pascal@24525 274 push word [es:di+14h-11]
pascal@24525 275 push word [es:di+1Ah-11]
pascal@24478 276 pop esi ; esi = cluster no. cx = 0
pascal@24476 277
pascal@24525 278 dec dword [es:di+1Ch-11] ; load ((n - 1)/256)*16 +1 paragraphs
pascal@24525 279 imul di, [es:di+1Ch+1-11], byte 16 ; file size in paragraphs (full pages)
pascal@24476 280
pascal@24476 281 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 282 ;; Load the entire file ;;
pascal@24476 283 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 284
pascal@24476 285 push es
pascal@24476 286 FileReadContinue:
pascal@24476 287 push di
pascal@25458 288 call ReadClusterSector ; read one sector of the boot file
pascal@25458 289 dec cx
pascal@24476 290 mov di, es
pascal@24478 291 add di, bp
pascal@24478 292 mov es, di ; es:bx updated
pascal@24476 293 pop di
pascal@24478 294
pascal@24476 295 sub di, bp
pascal@24476 296 jae FileReadContinue
pascal@24943 297 xor ax, ax
pascal@24476 298 pop bp
pascal@24476 299
pascal@24476 300 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 301 ;; Type detection, .COM or .EXE? ;;
pascal@24476 302 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 303
pascal@24476 304 mov ds, bp ; bp=ds=seg the file is loaded to
pascal@24535 305
pascal@24476 306 add bp, [bx+08h] ; bp = image base
pascal@24476 307 mov di, [bx+18h] ; di = reloc table pointer
pascal@24476 308
pascal@24476 309 cmp word [bx], 5A4Dh ; "MZ" signature?
pascal@24476 310 je RelocateEXE ; yes, it's an EXE program
pascal@24476 311
pascal@24476 312 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 313 ;; Setup and run a .COM program ;;
pascal@24535 314 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
pascal@25454 315 ;; AX=0ffffh BX=0 DX=drive and ;;
pascal@25454 316 ;; cmdline=void ;;
pascal@24476 317 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 318
pascal@24535 319 mov di, 100h ; ip
pascal@24476 320 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
pascal@24476 321 mov ss, bp
pascal@24476 322 xor sp, sp
pascal@24476 323 push bp ; cs, ds and es
pascal@25485 324 %if ExtraBootSector != 0
pascal@25485 325 jmp Run
pascal@25485 326 %macro BootFileName 0
pascal@25485 327 %else
pascal@24476 328 jmp short Run
pascal@25485 329 %endif
pascal@24476 330
pascal@24476 331 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 332 ;; Relocate, setup and run a .EXE program ;;
pascal@24476 333 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
pascal@24476 334 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
pascal@25454 335 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
pascal@24476 336 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 337
pascal@24476 338 ReloCycle:
pascal@24476 339 add [di+2], bp ; item seg (abs)
pascal@24476 340 les si, [di] ; si = item ofs, es = item seg
pascal@24476 341 add [es:si], bp ; fixup
pascal@24525 342 scasw ; di += 2
pascal@24525 343 scasw ; point to next entry
pascal@24476 344
pascal@24476 345 RelocateEXE:
pascal@24942 346 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
pascal@24942 347 jns ReloCycle
pascal@24942 348
pascal@24945 349 les si, [bx+0Eh]
pascal@24945 350 add si, bp
pascal@24945 351 mov ss, si ; ss for EXE
pascal@24945 352 mov sp, es ; sp for EXE
pascal@24476 353
pascal@24476 354 lea si, [bp-10h] ; ds and es both point to the segment
pascal@24476 355 push si ; containing the PSP structure
pascal@24476 356
pascal@24476 357 add bp, [bx+16h] ; cs for EXE
pascal@24535 358 mov di, [bx+14h] ; ip for EXE
pascal@24476 359 Run:
pascal@24476 360 pop ds
pascal@24476 361 push bp
pascal@24535 362 push di
pascal@24476 363 push ds
pascal@24476 364 pop es
pascal@24942 365 mov [80h], ax ; clear cmdline
pascal@24942 366 dec ax ; both FCB in the PSP don't have a valid drive identifier
pascal@24476 367
pascal@24476 368 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 369 ;; Set the magic numbers so the program knows that it ;;
pascal@24476 370 ;; has been loaded by this bootsector and not by MS-DOS ;;
pascal@24476 371 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 372 mov si, 16381 ; prime number 2**14-3
pascal@24476 373 mov di, 32749 ; prime number 2**15-19
pascal@24476 374 mov bp, 65521 ; prime number 2**16-15
pascal@24476 375
pascal@24476 376 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 377 ;; All done, transfer control to the program now ;;
pascal@24476 378 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 379 retf
pascal@25485 380 %if ExtraBootSector != 0
pascal@25485 381 %endm
pascal@25485 382 %endif
pascal@24476 383
pascal@25458 384 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 385 ;; Error Messaging Code ;;
pascal@25458 386 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 387
pascal@25458 388 Error:
pascal@25458 389 pop si
pascal@25458 390 puts:
pascal@25458 391 mov ah, 0Eh
pascal@25458 392 mov bl, 7
pascal@25458 393 lodsb
pascal@25458 394 int 10h
pascal@25458 395 cmp al, '.'
pascal@25458 396 jne puts
pascal@25458 397 cbw
pascal@25458 398 int 16h ; wait for a key...
pascal@25458 399 int 19h ; bootstrap
pascal@25458 400
pascal@25458 401 Stop:
pascal@25458 402 hlt
pascal@25458 403 jmp short Stop
pascal@25458 404
pascal@25458 405 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 406 ;; Reads a FAT32 sector ;;
pascal@25458 407 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 408 ;; Inout: ES:BX -> buffer ;;
pascal@25458 409 ;; EAX = prev sector ;;
pascal@25458 410 ;; CX = rem sectors in cluster ;;
pascal@25458 411 ;; ESI = next cluster ;;
pascal@25458 412 ;; Output: EAX = current sector ;;
pascal@25458 413 ;; CX = rem sectors in cluster ;;
pascal@25458 414 ;; ESI = next cluster ;;
pascal@25458 415 ;; BP -> para / sector ;;
pascal@25458 416 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 417
pascal@25458 418 ReadClusterSector:
pascal@25458 419 %if SectorOf512Bytes != 0
pascal@25458 420 mov bp, 32 ; bp = paragraphs per sector
pascal@25458 421 %else
pascal@24525 422 mov bp, [bx(bpbBytesPerSector)]
pascal@24525 423 shr bp, 4 ; bp = paragraphs per sector
pascal@25458 424 %endif
pascal@25449 425 mov dx, 1 ; adjust LBA for next sector
pascal@24525 426 inc cx
pascal@24525 427 loop ReadSectorLBA
pascal@24525 428
pascal@25449 429 mul ebx ; edx:eax = 0
pascal@25458 430 %if SectorOf512Bytes != 0
pascal@25458 431 mov al, 128 ; ax=# of FAT32 entries per sector
pascal@25458 432 %else
pascal@24945 433 imul ax, bp, byte 4 ; ax=# of FAT32 entries per sector
pascal@25458 434 %endif
pascal@24525 435 lea edi, [esi-2] ; esi=cluster #
pascal@24476 436 xchg eax, esi
pascal@24478 437 div esi ; eax=FAT sector #, edx=entry # in sector
pascal@24476 438
pascal@24525 439 imul si, dx, byte 4 ; si=entry # in sector, clear C
pascal@25485 440 %if NonMirroredFATs != 0
pascal@25485 441 cwde
pascal@25485 442 or dl, byte [bx(bsExtendedFlags)]
pascal@25485 443 jns MirroredFATs ; Non-mirrored FATs ?
pascal@25485 444 and dl, 0Fh
pascal@25485 445 imul edx, dword [bx(bsSectorsPerFAT32)] ; we need to read the active one
pascal@25485 446 add eax, edx
pascal@25485 447 MirroredFATs:
pascal@25485 448 cwde
pascal@25485 449 %else
pascal@25485 450 %if LBA48bits != 0
pascal@25458 451 xor dx, dx
pascal@25485 452 %endif
pascal@25449 453 %endif
pascal@25458 454 call ReadSectorLBAfromFAT ; read 1 FAT32 sector
pascal@24476 455
pascal@25449 456 %if ClusterMask != 0
pascal@24478 457 and byte [es:si+3], 0Fh ; mask cluster value
pascal@25449 458 %endif
pascal@24478 459 mov esi, [es:si] ; esi=next cluster #
pascal@24476 460
pascal@25458 461 %if Always2FATs != 0
pascal@25458 462 imul eax, dword [bx(bsSectorsPerFAT32)], 2
pascal@25458 463 %else
pascal@24525 464 movzx eax, byte [bx(bpbNumberOfFATs)]
pascal@24525 465 mul dword [bx(bsSectorsPerFAT32)]
pascal@25458 466 %endif
pascal@24525 467
pascal@24525 468 xchg eax, edi
pascal@25454 469 movzx ecx, byte [bx(bpbSectorsPerCluster)] ; 8..128
pascal@24945 470 mul ecx ; edx:eax=sector number in data area
pascal@24525 471 add eax, edi
pascal@25458 472 %if LBA48bits != 0
pascal@25458 473 adc dx, bx
pascal@25458 474 %endif
pascal@24476 475
pascal@25458 476 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 477 ;; Reads a sector form the start of FAT ;;
pascal@25458 478 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 479
pascal@25458 480 ReadSectorLBAfromFAT:
pascal@25458 481 add eax, [bx(bpbHiddenSectors)]
pascal@25449 482 %if LBA48bits != 0
pascal@25449 483 adc dx, bx
pascal@25449 484 mov word [bx(HiLBA)], dx
pascal@25449 485 %endif
pascal@25454 486 mov dx, [bx(bpbReservedSectors)]
pascal@24476 487
pascal@24478 488 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24478 489 ;; Reads a sector using BIOS Int 13h fn 42h ;;
pascal@24478 490 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24478 491 ;; Input: EAX = LBA ;;
pascal@24478 492 ;; CX = sector count ;;
pascal@24478 493 ;; ES:BX -> buffer address ;;
pascal@24478 494 ;; Output: CF = 0 if no more sectors ;;
pascal@24478 495 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 496
pascal@24476 497 ReadSectorLBA:
pascal@25449 498 add eax, edx
pascal@25449 499 %if LBA48bits != 0
pascal@24535 500 adc word [bx(HiLBA)], bx
pascal@25449 501 %endif
pascal@25485 502 ReadSectorBoot:
pascal@25449 503 mov dx, [bx(DriveNumber)] ; restore BIOS boot drive number
pascal@24476 504 pusha
pascal@24476 505
pascal@24478 506 push bx
pascal@25449 507 %if LBA48bits != 0
pascal@24491 508 push word [bx(HiLBA)] ; 48-bit LBA
pascal@25449 509 %else
pascal@25449 510 push bx
pascal@25449 511 %endif
pascal@24478 512 push eax
pascal@24476 513 push es
pascal@24476 514 push bx
pascal@24478 515 push byte 1 ; sector count word = 1
pascal@24525 516 push byte 16 ; packet size byte = 16, reserved byte = 0
pascal@24525 517
pascal@25449 518 %if CHSsupport != 0
pascal@25458 519 %if CHSupTo8GB != 0
pascal@25449 520 push eax
pascal@25449 521 pop cx ; save low LBA
pascal@25449 522 pop ax ; get high LBA
pascal@25449 523 cwd ; clear dx (assume LBA offset <1TB)
pascal@25449 524 idiv word [bx(bpbSectorsPerTrack)] ; up to 8GB disks, avoid divide error
pascal@25449 525
pascal@25449 526 xchg ax, cx ; restore low LBA, save high LBA / SPT
pascal@25458 527 %else
pascal@25449 528 ; Busybox mkdosfs creates fat32 for floppies.
pascal@25449 529 ; Floppies may support CHS only.
pascal@25458 530 %if CHSupTo32MB != 0
pascal@25458 531 xor dx, dx ; clear dx (LBA offset <32MB)
pascal@25458 532 %else
pascal@25449 533 cwd ; clear dx (LBA offset <16MB)
pascal@25458 534 %endif
pascal@25450 535 xor cx, cx ; high LBA / SPT = 0
pascal@25458 536 %endif
pascal@25449 537 idiv word [bx(bpbSectorsPerTrack)]
pascal@25449 538 ; ax = LBA / SPT
pascal@25449 539 ; dx = LBA % SPT = sector - 1
pascal@25449 540 inc dx
pascal@25449 541
pascal@25449 542 xchg cx, dx ; restore high LBA / SPT, save sector no.
pascal@25450 543 idiv word [bx(bpbHeadsPerCylinder)]
pascal@25449 544 ; ax = (LBA / SPT) / HPC = cylinder
pascal@25449 545 ; dx = (LBA / SPT) % HPC = head
pascal@25449 546
pascal@25458 547 xchg ch, al ; clear al
pascal@25449 548 ; ch = LSB 0...7 of cylinder no.
pascal@25458 549 %if CHSupTo8GB != 0 || CHSupTo32MB != 0
pascal@25458 550 shr ax, 2
pascal@25458 551 or cl, al
pascal@25449 552 ; cl = MSB 8...9 of cylinder no. + sector no.
pascal@25458 553 %endif
pascal@25449 554 mov dh, dl
pascal@25449 555 ; dh = head no.
pascal@25449 556 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
pascal@25449 557 %endif
pascal@25449 558
pascal@25454 559 ReadSectorRetry:
pascal@24525 560 mov si, sp
pascal@24478 561 mov ah, 42h ; ah = 42h = extended read function no.
pascal@24478 562 int 13h ; extended read sectors (DL, DS:SI)
pascal@24478 563 jnc ReadSuccess ; CF = 0 if no error
pascal@24476 564
pascal@25449 565 %if CHSsupport != 0
pascal@25449 566 mov ax, 201h ; al = sector count = 1
pascal@25449 567 ; ah = 2 = read function no.
pascal@25449 568 int 13h ; read sectors (AL, CX, DX, ES:BX)
pascal@25449 569
pascal@25449 570 jnc ReadSuccess ; CF = 0 if no error
pascal@25449 571 %endif
pascal@25449 572 %if ReadRetry != 0
pascal@25458 573 %if CHSsupport != 0
pascal@25449 574 cbw ; ah = 0 = reset function
pascal@25458 575 %else
pascal@24945 576 xor ax, ax ; ah = 0 = reset function
pascal@25458 577 %endif
pascal@24476 578 int 13h ; reset drive (DL)
pascal@24476 579
pascal@25457 580 dec bp ; up to 32 retries
pascal@25454 581 jnz ReadSectorRetry
pascal@25449 582 %endif
pascal@24525 583
pascal@24476 584 call Error
pascal@24476 585 db "Read error."
pascal@24476 586
pascal@24478 587 ReadSuccess:
pascal@24476 588
pascal@24476 589 popa ; sp += 16
pascal@24478 590 popa
pascal@24476 591 ret
pascal@24476 592
pascal@24942 593 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24942 594 ;; Fill free space with zeroes ;;
pascal@24942 595 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24942 596
pascal@25458 597 times (512-13-($-$$)) db 0
pascal@24476 598
pascal@24476 599 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 600 ;; Name of the file to load and run ;;
pascal@24476 601 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 602
pascal@25463 603 NameLength equ 11
pascal@25463 604 ProgramName times NameLength db 0 ; name and extension
pascal@24476 605
pascal@24476 606 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 607 ;; End of the sector ID ;;
pascal@24476 608 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 609
pascal@24476 610 dw 0AA55h ; BIOS checks for this ID
pascal@25485 611
pascal@25485 612 %if ExtraBootSector != 0
pascal@25485 613 dd 61415252h ; "RRaA"
pascal@25485 614 BootFileName
pascal@25485 615 times (996-($-$$)) db 0
pascal@25485 616 ; dd 41617272h ; "rrAa"
pascal@25485 617 %endif