wok annotate BootProg/stuff/bootex.asm @ rev 25697

dool: reduced size of package
author Hans-G?nter Theisgen
date Sun May 12 07:10:04 2024 +0100 (4 weeks ago)
parents 3c71bb4367c3
children 82a123e54615
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 bootex.asm -f bin -o bootex.bin ;;
pascal@24476 10 ;; ;;
pascal@24476 11 ;; ;;
pascal@24476 12 ;; Features: ;;
pascal@24476 13 ;; ~~~~~~~~~ ;;
pascal@24476 14 ;; - exFAT supported using BIOS int 13h function 42h. ;;
pascal@24476 15 ;; ;;
pascal@24476 16 ;; - Loads a 16-bit executable file in the MS-DOS .COM or .EXE format ;;
pascal@24476 17 ;; from the root directory of a disk and transfers control to it ;;
pascal@24476 18 ;; (the "ProgramName" variable holds the name of the file to be loaded) ;;
pascal@25460 19 ;; Its maximum size can be up to 637KB without Extended BIOS Data area. ;;
pascal@24476 20 ;; ;;
pascal@24476 21 ;; - Prints an error if the file isn't found or couldn't be read ;;
pascal@24476 22 ;; ("File not found" or "Read error") ;;
pascal@24476 23 ;; and waits for a key to be pressed, then executes the Int 19h ;;
pascal@24476 24 ;; instruction and lets the BIOS continue bootstrap. ;;
pascal@24476 25 ;; ;;
pascal@24476 26 ;; ;;
pascal@24476 27 ;; Known Bugs: ;;
pascal@24476 28 ;; ~~~~~~~~~~~ ;;
pascal@24476 29 ;; - All bugs are fixed as far as I know. The boot sector has been tested ;;
pascal@24476 30 ;; on a 128MB qemu image. ;;
pascal@24476 31 ;; ;;
pascal@24476 32 ;; ;;
pascal@24476 33 ;; Memory Layout: ;;
pascal@24476 34 ;; ~~~~~~~~~~~~~~ ;;
pascal@24476 35 ;; The diagram below shows the typical memory layout. The actual location ;;
pascal@24476 36 ;; of the boot sector and its stack may be lower than A0000H if the BIOS ;;
pascal@24476 37 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
pascal@24476 38 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
pascal@24476 39 ;; ;;
pascal@24476 40 ;; physical address ;;
pascal@24476 41 ;; +------------------------+ 00000H ;;
pascal@24476 42 ;; | Interrupt Vector Table | ;;
pascal@24476 43 ;; +------------------------+ 00400H ;;
pascal@24476 44 ;; | BIOS Data Area | ;;
pascal@24476 45 ;; +------------------------+ 00500H ;;
pascal@24476 46 ;; | PrtScr Status / Unused | ;;
pascal@24476 47 ;; +------------------------+ 00600H ;;
pascal@24476 48 ;; | Loaded Image | ;;
pascal@24476 49 ;; +------------------------+ nnnnnH ;;
pascal@24476 50 ;; | Available Memory | ;;
pascal@25460 51 ;; +------------------------+ A0000H - 1KB ;;
pascal@24476 52 ;; | Boot Sector | ;;
pascal@25460 53 ;; +------------------------+ A0000H - 0.5KB ;;
pascal@25460 54 ;; | 0.5KB Boot Stack | ;;
pascal@24476 55 ;; +------------------------+ A0000H ;;
pascal@24476 56 ;; | Video RAM | ;;
pascal@24476 57 ;; ;;
pascal@24476 58 ;; ;;
pascal@24476 59 ;; Boot Image Startup (register values): ;;
pascal@24476 60 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
pascal@24945 61 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
pascal@25454 62 ;; bx = 0, dl = BIOS boot drive number (e.g. 0, 80H) ;;
pascal@24476 63 ;; cs:ip = program entry point ;;
pascal@24476 64 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
pascal@24476 65 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
pascal@24476 66 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
pascal@24476 67 ;; cs:ip and ss:sp depends on EXE header ;;
pascal@24476 68 ;; Magic numbers: ;;
pascal@24476 69 ;; si = 16381 (prime number 2**14-3) ;;
pascal@24476 70 ;; di = 32749 (prime number 2**15-19) ;;
pascal@24476 71 ;; bp = 65521 (prime number 2**16-15) ;;
pascal@24476 72 ;; The magic numbers let the program know whether it has been loaded by ;;
pascal@24476 73 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
pascal@24476 74 ;; metal and MS-DOS programs. ;;
pascal@24945 75 ;; The command line contains no arguments. ;;
pascal@24476 76 ;; ;;
pascal@24476 77 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 78
pascal@24476 79 %define bx(label) bx+label-boot
pascal@25450 80 %define si(label) si+label-boot
pascal@25569 81 NullEntryCheck equ 1 ; +3/5 bytes
pascal@25569 82 ReadRetry equ 1 ; +7 bytes
pascal@25569 83 SectorOf512Bytes equ 0 ; -12 bytes
pascal@25569 84 CheckAttrib equ 0 ; +16/18 bytes
pascal@25564 85 WaitForKey equ 0 ; +5 bytes
pascal@25564 86 TfatSupport equ 1 ; +10 bytes
pascal@25564 87 CheckLBAsupport equ 0 ; +11/21 bytes
pascal@24476 88
pascal@24476 89 [BITS 16]
pascal@24476 90 [CPU 386]
pascal@24476 91
pascal@24476 92 ImageLoadSeg equ 60h
pascal@25460 93 StackSize equ 512
pascal@24476 94
pascal@24476 95 [SECTION .text]
pascal@24476 96 [ORG 0]
pascal@24476 97
pascal@24476 98 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 99 ;; Boot sector starts here ;;
pascal@24476 100 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 101
pascal@24476 102 boot:
pascal@25450 103 DriveNumber:
pascal@24476 104 jmp short start ; Windows checks for this jump
pascal@24476 105 nop
pascal@25458 106 bsOemName times 8 db " " ; 0x03 "EXFAT "
pascal@24476 107 times 53 db 0 ; 0x0B
pascal@24476 108
pascal@24476 109 ;;;;;;;;;;;;;;;;;;;;;
pascal@24476 110 ;; BPB starts here ;;
pascal@24476 111 ;;;;;;;;;;;;;;;;;;;;;
pascal@24476 112
pascal@24479 113 bpbSectorStart DQ 0 ; 0x40 partition first sector
pascal@24479 114 bpbSectorCount DQ 0 ; 0x48 partition sectors count
pascal@24479 115 bpbFatSectorStart DD 0 ; 0x50 FAT first sector
pascal@24479 116 bpbFatSectorCount DD 0 ; 0x54 FAT sectors count
pascal@24479 117 bpbClusterSectorStart DD 0 ; 0x58 first cluster sector
pascal@24479 118 bpbClusterCount DD 0 ; 0x5C total clusters count
pascal@24479 119 bpbRootDirCluster DD 0 ; 0x60 first cluster of the root dir
pascal@24479 120 bpbVolumeSerial DD 0 ; 0x64 volume serial number
pascal@24479 121 bpbFSVersionMinor DB 0 ; 0x68
pascal@24479 122 bpbFSVersionMajor DB 0 ; 0x69
pascal@25564 123 bpbVolumeStateFlags DW 0 ; 0x6A bit0 = fat used, bit1 = dirty, bit2 = media error
pascal@24479 124 bpbSectorSizeBits DB 0 ; 0x6C sector size as (1 << n)
pascal@24479 125 bpbSectorPerClusterBits DB 0 ; 0x6D sector per cluster as (1 << n)
pascal@25564 126 bpbNumberOfFATs DB 0 ; 0x6E always 1 or 2 (Tfat case)
pascal@25564 127 bpbDriveNumber DB 0 ; 0x6F always 0x80
pascal@24479 128 bpbAllocatedPercent DB 0 ; 0x70 percentage of allocated space
pascal@24476 129
pascal@24476 130 ;;;;;;;;;;;;;;;;;;;
pascal@24476 131 ;; BPB ends here ;;
pascal@24476 132 ;;;;;;;;;;;;;;;;;;;
pascal@24476 133
pascal@24476 134 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 135 ;; Boot sector code starts here ;;
pascal@24476 136 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 137
pascal@24476 138 start:
pascal@24476 139 cld
pascal@24476 140
pascal@24476 141 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 142 ;; How much RAM is there? ;;
pascal@24476 143 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 144
pascal@24476 145 int 12h ; get conventional memory size (in KBs)
pascal@24476 146 mov cx, 106h
pascal@25460 147 dec ax ; reserve 1K bytes for the code and the stack
pascal@24476 148 shl ax, cl ; and convert it to 16-byte paragraphs
pascal@24476 149
pascal@24476 150 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 151 ;; Reserve memory for the boot sector and its stack ;;
pascal@24476 152 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 153
pascal@24476 154 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
pascal@24476 155 mov ss, ax
pascal@24476 156 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
pascal@24476 157
pascal@24476 158 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 159 ;; Copy ourselves to top of memory ;;
pascal@24476 160 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 161
pascal@24476 162 mov si, 7C00h
pascal@24476 163 xor di, di
pascal@24476 164 mov ds, di
pascal@25450 165 push es
pascal@25450 166 mov [si(DriveNumber)], dx ; store BIOS boot drive number
pascal@24476 167 rep movsw ; move 512 bytes (+ 12)
pascal@24476 168
pascal@24476 169 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 170 ;; Jump to the copy ;;
pascal@24476 171 ;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 172
pascal@24942 173 push word main
pascal@24476 174 retf
pascal@24476 175
pascal@25564 176 %if CheckLBAsupport != 0
pascal@25564 177 %macro BootFileName 0
pascal@24476 178 main:
pascal@25564 179 mov ah, 41h ; clobbers AX, BX, CX, DH
pascal@25564 180 mov bx, 55AAh
pascal@25564 181 int 13h
pascal@25564 182 jc ReadError
pascal@25564 183 ; xor bx, 0AA55h
pascal@25564 184 ; jnz ReadError
pascal@25564 185 ; shr cx, 1 ; function 42h support ?
pascal@25564 186 ; jnc ReadError
pascal@25564 187 xor cx, cx
pascal@25564 188 %else
pascal@25564 189 main:
pascal@25564 190 %endif
pascal@24476 191 push cs
pascal@24476 192 pop ds
pascal@24476 193
pascal@24476 194 xor ebx, ebx
pascal@24476 195
pascal@24476 196 mov esi, [bx(bpbRootDirCluster)] ; esi=cluster # of root dir
pascal@24476 197
pascal@24479 198 push byte ImageLoadSeg
pascal@24942 199 pop es ; cx = 0
pascal@24476 200
pascal@24476 201 RootDirReadContinue:
pascal@24476 202 call ReadCluster ; read one sector of root dir
pascal@24476 203
pascal@24476 204 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 205 ;; Look for the COM/EXE file to load and run ;;
pascal@24476 206 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 207
pascal@25454 208 ; es:di -> root entries array
pascal@24476 209
pascal@24476 210 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 211 ;; Looks for the file/dir ProgramName ;;
pascal@24476 212 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 213 ;; Input: ES:DI -> root directory array ;;
pascal@24476 214 ;; Output: ESI = cluster number ;;
pascal@24476 215 ;; dword [bx+FileSize] file size ;;
pascal@24476 216 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 217
pascal@25467 218 CurNameSize equ 03h ; 1 byte
pascal@25450 219 StartCluster equ 14h ; 4 bytes
pascal@25450 220 FileSize equ 18h ; 8 bytes
pascal@24476 221
pascal@24476 222 FindNameCycle:
pascal@24476 223 pusha
pascal@24476 224
pascal@25564 225 %if NullEntryCheck != 0
pascal@25564 226 xor ax, ax
pascal@25564 227 or al, [es:di]
pascal@25564 228 je FindNameFailed
pascal@25564 229 %define curtag al
pascal@25564 230 %define chktag al
pascal@25564 231 %else
pascal@25564 232 %define curtag byte [es:di]
pascal@25564 233 %define chktag ax
pascal@25564 234 %endif
pascal@25564 235 cmp curtag, 0c0h ; EXFAT_ENTRY_FILE_INFO ?
pascal@25564 236 jne NotFileInfo
pascal@25564 237
pascal@25564 238 mov bl, 32
pascal@25564 239 CopyInfo:
pascal@25564 240 mov [bx], al
pascal@25564 241 dec bx
pascal@25564 242 mov al, [es:di+bx]
pascal@25564 243 jnz CopyInfo ; keep BIOS boot drive number
pascal@25564 244
pascal@25564 245 NotFileInfo:
pascal@25469 246 %if CheckAttrib != 0
pascal@25469 247 Attributes equ 0Bh ; 1 byte
pascal@25564 248 cmp curtag, 85h ; EXFAT_ENTRY_FILE ?
pascal@25469 249 jne NotEntryFile
pascal@25469 250 mov al, [es:di+Attributes]
pascal@25550 251 mov [ProgramName+NameLength+1], al
pascal@25469 252 NotEntryFile:
pascal@25469 253 %endif
pascal@25564 254 mov chktag, 0c1h ; EXFAT_ENTRY_FILE_NAME ?
pascal@24476 255 mov cx, NameLength+1
pascal@24476 256 mov si, ProgramName ; ds:si -> program name
pascal@24476 257 CheckName:
pascal@24476 258 scasw ; compare UTF-16
pascal@24476 259 lodsb ; with ASCII
pascal@24476 260 loope CheckName
pascal@25467 261 VolumeLabel equ 8
pascal@25467 262 SubDirectory equ 10h
pascal@25564 263 %if CheckAttrib != 0
pascal@25467 264 jnz SkipFindName
pascal@25550 265 test byte [si], VolumeLabel+SubDirectory
pascal@25467 266 SkipFindName:
pascal@25467 267 %endif
pascal@24476 268 je FindNameFound ; cx = 0
pascal@24476 269 popa ; restore ax, cx, si, di
pascal@24476 270
pascal@24479 271 add di, byte 32
pascal@24945 272 cmp di, bp
pascal@24945 273 jne FindNameCycle ; next root entry
pascal@25458 274 loop RootDirReadContinue ; continue to the next root dir sector
pascal@25458 275 cmp esi, byte -10 ; carry=0 if last cluster, and carry=1 otherwise
pascal@24476 276 jc RootDirReadContinue ; continue to the next root dir cluster
pascal@24476 277 FindNameFailed: ; end of root directory (dir end reached)
pascal@25454 278 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
pascal@24476 279 call Error
pascal@24476 280 db "File not found."
pascal@24476 281 FindNameFound:
pascal@24476 282 mov esi, [bx+StartCluster]
pascal@24476 283
pascal@24476 284 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 285 ;; Load the entire file ;;
pascal@25550 286 ;; Input: ESI = cluster ;;
pascal@25550 287 ;; CX = 0 ;;
pascal@24476 288 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 289
pascal@24476 290 push es
pascal@25458 291 %if SectorOf512Bytes == 0
pascal@24945 292 xor bp, bp
pascal@24476 293 FileReadContinue:
pascal@24476 294 shr bp, 4 ; bytes to paragraphs
pascal@24476 295 mov di, es
pascal@24476 296 add di, bp ; adjust segment for next sector
pascal@24476 297 mov es, di ; es:0 updated
pascal@25458 298 %else
pascal@25458 299 FileReadContinue:
pascal@25458 300 %endif
pascal@24943 301 call ReadCluster ; read one more sector of the boot file
pascal@25458 302 dec cx
pascal@25450 303 sub [bx+FileSize], ebp ; max FileSize is < 640KB : check low 32 bits only
pascal@25458 304 %if SectorOf512Bytes != 0
pascal@25458 305 mov bp, es
pascal@25458 306 lea bp, [bp+32]
pascal@25458 307 mov es, bp ; es:0 updated
pascal@25458 308 %endif
pascal@24476 309 ja FileReadContinue
pascal@25450 310 mov dx, [bx(DriveNumber)] ; restore BIOS boot drive number
pascal@25454 311 xchg ax, di
pascal@24476 312 pop bp
pascal@24476 313
pascal@24476 314 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 315 ;; Type detection, .COM or .EXE? ;;
pascal@24476 316 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 317
pascal@24476 318 mov ds, bp ; bp=ds=seg the file is loaded to
pascal@24476 319
pascal@24476 320 add bp, [bx+08h] ; bp = image base
pascal@24476 321 mov di, [bx+18h] ; di = reloc table pointer
pascal@24476 322
pascal@24476 323 cmp word [bx], 5A4Dh ; "MZ" signature?
pascal@24476 324 je RelocateEXE ; yes, it's an EXE program
pascal@24476 325
pascal@24476 326 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 327 ;; Setup and run a .COM program ;;
pascal@24476 328 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
pascal@25454 329 ;; AX=0ffffh BX=0 DX=drive and ;;
pascal@25454 330 ;; cmdline=void ;;
pascal@24476 331 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 332
pascal@24525 333 mov di, 100h ; ip
pascal@24476 334 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
pascal@24476 335 mov ss, bp
pascal@24476 336 xor sp, sp
pascal@24476 337 push bp ; cs, ds and es
pascal@24476 338 jmp short Run
pascal@24476 339
pascal@24476 340 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 341 ;; Relocate, setup and run a .EXE program ;;
pascal@24476 342 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
pascal@24476 343 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
pascal@25454 344 ;; AX=0ffffh BX=0 DX=drive cmdline=void ;;
pascal@24476 345 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 346
pascal@24476 347 ReloCycle:
pascal@24476 348 add [di+2], bp ; item seg (abs)
pascal@24476 349 les si, [di] ; si = item ofs, es = item seg
pascal@24476 350 add [es:si], bp ; fixup
pascal@24476 351 scasw ; di += 2
pascal@24476 352 scasw ; point to next entry
pascal@24476 353
pascal@24476 354 RelocateEXE:
pascal@24942 355 dec word [bx+06h] ; reloc items, 32768 max (128KB table)
pascal@24942 356 jns ReloCycle
pascal@24942 357
pascal@24945 358 les si, [bx+0Eh]
pascal@24945 359 add si, bp
pascal@24945 360 mov ss, si ; ss for EXE
pascal@24945 361 mov sp, es ; sp for EXE
pascal@24476 362
pascal@24476 363 lea si, [bp-10h] ; ds and es both point to the segment
pascal@24476 364 push si ; containing the PSP structure
pascal@24476 365
pascal@24476 366 add bp, [bx+16h] ; cs for EXE
pascal@24525 367 mov di, [bx+14h] ; ip for EXE
pascal@24476 368 Run:
pascal@24476 369 pop ds
pascal@24476 370 push bp
pascal@24525 371 push di
pascal@24476 372 push ds
pascal@24476 373 pop es
pascal@24942 374 mov [80h], ax ; clear cmdline
pascal@24942 375 dec ax ; both FCB in the PSP don't have a valid drive identifier
pascal@24476 376
pascal@24476 377 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 378 ;; Set the magic numbers so the program knows that it ;;
pascal@24476 379 ;; has been loaded by this bootsector and not by MS-DOS ;;
pascal@24476 380 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 381 mov si, 16381 ; prime number 2**14-3
pascal@24476 382 mov di, 32749 ; prime number 2**15-19
pascal@24476 383 mov bp, 65521 ; prime number 2**16-15
pascal@24476 384
pascal@24476 385 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 386 ;; All done, transfer control to the program now ;;
pascal@24476 387 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 388 retf
pascal@25564 389 %if CheckLBAsupport != 0
pascal@25564 390 %endm
pascal@25564 391 %endif
pascal@24476 392
pascal@25458 393 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 394 ;; Error Messaging Code ;;
pascal@25458 395 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@25458 396
pascal@25458 397 Error:
pascal@25458 398 pop si
pascal@25458 399
pascal@25458 400 PutStr:
pascal@25458 401 mov ah, 0Eh
pascal@25458 402 mov bl, 7
pascal@25458 403 lodsb
pascal@25458 404 int 10h
pascal@25458 405 cmp al, "."
pascal@25458 406 jne PutStr
pascal@25564 407 %if WaitForKey != 0
pascal@25458 408 cbw
pascal@25458 409 int 16h ; wait for a key...
pascal@25458 410 int 19h ; bootstrap
pascal@25564 411 %endif
pascal@25458 412 Stop:
pascal@25458 413 hlt
pascal@25458 414 jmp short Stop
pascal@25458 415
pascal@24476 416 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 417 ;; Reads a exFAT cluster ;;
pascal@24476 418 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 419 ;; Input: EDX:EAX = LBA ;;
pascal@25564 420 ;; EBX = 0 ;;
pascal@24476 421 ;; CX = sector cnt ;;
pascal@24476 422 ;; ESI = cluster no ;;
pascal@24476 423 ;; ES:0 -> buffer adrs ;;
pascal@25550 424 ;; Output: EDX:EAX = next LBA ;;
pascal@25550 425 ;; CX = sector cnt ;;
pascal@25550 426 ;; ESI = cluster no ;;
pascal@24476 427 ;; EBP = bytes/sector;;
pascal@25550 428 ;; Keep: EDI = 0 ;;
pascal@24476 429 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 430
pascal@24476 431 ReadCluster:
pascal@24945 432 add eax, byte 1
pascal@24945 433
pascal@24476 434 inc cx ; jcxnz
pascal@24476 435 loop ReadSectorC
pascal@24476 436
pascal@24945 437 mul ebx ; edx:eax = 0
pascal@25458 438 %if SectorOf512Bytes != 0
pascal@25458 439 mov al, 128
pascal@25564 440 %define SectorPerClusterBits [bx(bpbSectorPerClusterBits)]
pascal@25458 441 %else
pascal@25550 442 mov ah, 40h
pascal@25550 443 mov cx, [bx(bpbSectorSizeBits)]
pascal@25564 444 %define SectorPerClusterBits ch
pascal@25550 445 rol ax, cl ; eax=# of exFAT entries per sector
pascal@25458 446 %endif
pascal@24476 447 lea edi, [esi-2] ; edi=cluster #-2
pascal@24476 448 xchg eax, esi
pascal@24476 449 div esi ; eax=FAT sector #, edx=entry # in sector
pascal@24476 450
pascal@24525 451 imul si, dx, byte 4 ; si=entry # offset in sector
pascal@24476 452
pascal@24476 453 cdq
pascal@25452 454 add eax, [bx(bpbFatSectorStart)] ; sector # relative to exFAT
pascal@25564 455 %if TfatSupport
pascal@25564 456 test byte [bx(bpbVolumeStateFlags)], 1
pascal@25564 457 jz UseFat0
pascal@25564 458 add eax, [bx(bpbFatSectorCount)]
pascal@25564 459 UseFat0:
pascal@25564 460 %endif
pascal@25454 461 call ReadSectorFAT ; read 1 exFAT sector, keep edx=0, set C
pascal@24476 462
pascal@24476 463 mov esi, [es:si] ; esi=next cluster #
pascal@24476 464
pascal@25564 465 mov dl, SectorPerClusterBits
pascal@25452 466 xor ecx, ecx
pascal@25450 467 bts ecx, edx ; 10000h max (32MB cluster)
pascal@24476 468 xchg eax, edi ; get cluster #-2
pascal@24476 469 mul ecx
pascal@24476 470
pascal@24476 471 add eax, [bx(bpbClusterSectorStart)]
pascal@24476 472 ReadSectorC:
pascal@25454 473 mov di, bx
pascal@25454 474 ReadSectorFAT:
pascal@24476 475 adc edx, ebx
pascal@24476 476
pascal@24476 477 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 478 ;; Reads a sector using BIOS Int 13h ;;
pascal@24476 479 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 480 ;; Input: EDX:EAX = LBA ;;
pascal@25564 481 ;; EBX = 0 ;;
pascal@24476 482 ;; ES:0 -> buffer address ;;
pascal@25550 483 ;; Output: EBP = bytes/sector ;;
pascal@25550 484 ;; Keep: ESI = cluster ;;
pascal@25550 485 ;; EDI = FAT sector or 0 ;;
pascal@25550 486 ;; ECX = sector count ;;
pascal@24476 487 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 488
pascal@25458 489 %if SectorOf512Bytes != 0
pascal@25458 490 lea ebp, [bx+512]
pascal@25458 491 %else
pascal@25458 492 lea ebp, [bx+1]
pascal@25458 493 %endif
pascal@24476 494
pascal@24476 495 pushad
pascal@24476 496
pascal@24476 497 add eax, [bx(bpbSectorStart)]
pascal@24476 498 adc edx, [bx(bpbSectorStart)+4]
pascal@24476 499
pascal@24476 500 push edx
pascal@24476 501 push eax
pascal@24476 502 push es
pascal@24476 503 push bx
pascal@25458 504 %if SectorOf512Bytes != 0
pascal@25458 505 push byte 1 ; sector count word = 1
pascal@25458 506 %else
pascal@24476 507 push bp ; sector count word = 1
pascal@25458 508 %endif
pascal@25454 509 push byte 16 ; packet size byte = 16, reserved byte = 0
pascal@24476 510 ReadSectorRetry:
pascal@24476 511 mov si, sp
pascal@24476 512 mov ah, 42h ; ah = 42h = extended read function no.
pascal@25450 513 mov dl, [bx(DriveNumber)] ; restore BIOS boot drive number
pascal@24476 514 int 13h ; extended read sectors (DL, DS:SI)
pascal@24476 515
pascal@24476 516 jnc ReadSuccess
pascal@24476 517
pascal@25450 518 %if ReadRetry != 0
pascal@24476 519 xor ax, ax
pascal@24476 520 int 13h ; reset drive (DL)
pascal@25457 521 dec bp
pascal@25458 522 %if SectorOf512Bytes != 0
pascal@25458 523 jne ReadSectorRetry ; up to 511 tries
pascal@25458 524 %else
pascal@25457 525 jpe ReadSectorRetry ; up to 3 tries
pascal@25458 526 %endif
pascal@25450 527 %endif
pascal@24476 528
pascal@25564 529 ReadError:
pascal@24476 530 call Error
pascal@24476 531 db "Read error."
pascal@24476 532
pascal@24476 533 ReadSuccess:
pascal@25458 534 %if SectorOf512Bytes == 0
pascal@24476 535 mov cl, [bx(bpbSectorSizeBits)]
pascal@24476 536 shl word [si+16+8], cl ; (e)bp si+16: EDI ESI EBP ESP EBX EDX ECX EAX
pascal@25458 537 %endif
pascal@24476 538 popa ; sp += 16
pascal@24476 539 popad ; real registers
pascal@24476 540 ret
pascal@24476 541
pascal@25564 542 %if CheckLBAsupport != 0
pascal@25564 543 BootFileName
pascal@25564 544 %endif
pascal@25564 545
pascal@24942 546 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24942 547 ;; Fill free space with zeroes ;;
pascal@24942 548 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24942 549
pascal@25458 550 times (512-13-($-$$)) db 0
pascal@24476 551
pascal@24476 552 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 553 ;; Name of the file to load and run ;;
pascal@24476 554 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 555
pascal@25463 556 NameLength equ 11
pascal@25463 557 ProgramName times NameLength db 0 ; name and extension
pascal@24476 558
pascal@24476 559 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 560 ;; End of the sector ID ;;
pascal@24476 561 ;;;;;;;;;;;;;;;;;;;;;;;;;;
pascal@24476 562
pascal@24476 563 dw 0AA55h ; BIOS checks for this ID