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@24525
|
14 ;; - FAT32 supported using BIOS int 13h function 42h or 02h. ;;
|
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@24525
|
19 ;; Its maximum size can be up to 636KB 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 my HDD and an 8GB USB stick. ;;
|
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@24525
|
51 ;; +------------------------+ A0000H - 2KB ;;
|
pascal@24476
|
52 ;; | Boot Sector | ;;
|
pascal@24525
|
53 ;; +------------------------+ A0000H - 1.5KB ;;
|
pascal@24525
|
54 ;; | 1.5KB 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@24476
|
61 ;; dl = BIOS boot drive number (e.g. 80H) ;;
|
pascal@24476
|
62 ;; cs:ip = program entry point ;;
|
pascal@24476
|
63 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
|
pascal@24476
|
64 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
|
pascal@24476
|
65 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
|
pascal@24476
|
66 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
|
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@24476
|
75 ;; ;;
|
pascal@24476
|
76 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
77
|
pascal@24491
|
78 %define bx(label) bx+label-boot
|
pascal@24491
|
79
|
pascal@24476
|
80 [BITS 16]
|
pascal@24476
|
81
|
pascal@24478
|
82 ImageLoadSeg equ 60h ; <=07Fh because of "push byte ImageLoadSeg" instructions
|
pascal@24525
|
83 StackSize equ 1536
|
pascal@24476
|
84
|
pascal@24476
|
85 [SECTION .text]
|
pascal@24476
|
86 [ORG 0]
|
pascal@24476
|
87
|
pascal@24476
|
88 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
89 ;; Boot sector starts here ;;
|
pascal@24476
|
90 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
91
|
pascal@24491
|
92 boot:
|
pascal@24491
|
93 HiLBA equ boot+0
|
pascal@24476
|
94 jmp short start ; MS-DOS/Windows checks for this jump
|
pascal@24476
|
95 nop
|
pascal@24476
|
96 bsOemName DB "BootProg" ; 0x03
|
pascal@24476
|
97
|
pascal@24476
|
98 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
99 ;; BPB1 starts here ;;
|
pascal@24476
|
100 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
101
|
pascal@24479
|
102 bpbBytesPerSector DW 0 ; 0x0B
|
pascal@24479
|
103 bpbSectorsPerCluster DB 0 ; 0x0D
|
pascal@24479
|
104 bpbReservedSectors DW 0 ; 0x0E
|
pascal@24479
|
105 bpbNumberOfFATs DB 0 ; 0x10
|
pascal@24479
|
106 bpbRootEntries DW 0 ; 0x11
|
pascal@24479
|
107 bpbTotalSectors DW 0 ; 0x13
|
pascal@24479
|
108 bpbMedia DB 0 ; 0x15
|
pascal@24479
|
109 bpbSectorsPerFAT DW 0 ; 0x16
|
pascal@24479
|
110 bpbSectorsPerTrack DW 0 ; 0x18
|
pascal@24479
|
111 bpbHeadsPerCylinder DW 0 ; 0x1A
|
pascal@24479
|
112 bpbHiddenSectors DD 0 ; 0x1C
|
pascal@24479
|
113 bpbTotalSectorsBig DD 0 ; 0x20
|
pascal@24476
|
114
|
pascal@24476
|
115 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
116 ;; BPB1 ends here ;;
|
pascal@24476
|
117 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
118
|
pascal@24476
|
119 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
120 ;; BPB2 starts here ;;
|
pascal@24476
|
121 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
122
|
pascal@24479
|
123 bsSectorsPerFAT32 DD 0 ; 0x24
|
pascal@24479
|
124 bsExtendedFlags DW 0 ; 0x28
|
pascal@24479
|
125 bsFSVersion DW 0 ; 0x2A
|
pascal@24479
|
126 bsRootDirectoryClusterNo DD 0 ; 0x2C
|
pascal@24479
|
127 bsFSInfoSectorNo DW 0 ; 0x30
|
pascal@24479
|
128 bsBackupBootSectorNo DW 0 ; 0x32
|
pascal@24479
|
129 bsreserved times 12 DB 0 ; 0x34
|
pascal@24479
|
130 bsDriveNumber DB 0 ; 0x40
|
pascal@24479
|
131 bsreserved1 DB 0 ; 0x41
|
pascal@24479
|
132 bsExtendedBootSignature DB 0 ; 0x42
|
pascal@24479
|
133 bsVolumeSerialNumber DD 0 ; 0x43
|
pascal@24476
|
134 bsVolumeLabel DB "NO NAME " ; 0x47
|
pascal@24476
|
135 bsFileSystemName DB "FAT32 " ; 0x52
|
pascal@24476
|
136
|
pascal@24476
|
137 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
138 ;; BPB2 ends here ;;
|
pascal@24476
|
139 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
140
|
pascal@24476
|
141 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
142 ;; Boot sector code starts here ;;
|
pascal@24476
|
143 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
144
|
pascal@24476
|
145 start:
|
pascal@24476
|
146 cld
|
pascal@24476
|
147
|
pascal@24476
|
148 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
149 ;; How much RAM is there? ;;
|
pascal@24476
|
150 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
151
|
pascal@24476
|
152 int 12h ; get conventional memory size (in KBs)
|
pascal@24525
|
153 dec ax
|
pascal@24525
|
154 dec ax ; reserve 2K bytes for the code and the stack
|
pascal@24525
|
155 mov cx, 106h
|
pascal@24525
|
156 shl ax, cl ; and convert it to 16-byte paragraphs
|
pascal@24476
|
157
|
pascal@24476
|
158 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
159 ;; Reserve memory for the boot sector and its stack ;;
|
pascal@24476
|
160 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
161
|
pascal@24525
|
162 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
|
pascal@24525
|
163 mov ss, ax
|
pascal@24525
|
164 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
|
pascal@24476
|
165
|
pascal@24476
|
166 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
167 ;; Copy ourselves to top of memory ;;
|
pascal@24476
|
168 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
169
|
pascal@24476
|
170 mov si, 7C00h
|
pascal@24476
|
171 xor di, di
|
pascal@24476
|
172 mov ds, di
|
pascal@24478
|
173 rep movsw
|
pascal@24476
|
174
|
pascal@24476
|
175 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
176 ;; Jump to the copy ;;
|
pascal@24476
|
177 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
178
|
pascal@24476
|
179 push es
|
pascal@24478
|
180 push byte main
|
pascal@24476
|
181 retf
|
pascal@24476
|
182
|
pascal@24476
|
183 main:
|
pascal@24476
|
184 push cs
|
pascal@24476
|
185 pop ds
|
pascal@24476
|
186
|
pascal@24491
|
187 xor bx, bx
|
pascal@24491
|
188 mov [bx(bsDriveNumber)], dx ; store BIOS boot drive number
|
pascal@24476
|
189
|
pascal@24491
|
190 and byte [bx(bsRootDirectoryClusterNo+3)], 0Fh ; mask cluster value
|
pascal@24491
|
191 mov esi, [bx(bsRootDirectoryClusterNo)] ; esi=cluster # of root dir
|
pascal@24476
|
192
|
pascal@24476
|
193 RootDirReadContinue:
|
pascal@24478
|
194 push byte ImageLoadSeg
|
pascal@24478
|
195 pop es
|
pascal@24478
|
196 call ReadCluster ; read one cluster of root dir
|
pascal@24478
|
197 pushf ; save carry="not last cluster" flag
|
pascal@24476
|
198
|
pascal@24476
|
199 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
200 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
201 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
202
|
pascal@24476
|
203 xor di, di ; es:di -> root entries array
|
pascal@24476
|
204
|
pascal@24476
|
205 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
206 ;; Looks for a file/dir by its name ;;
|
pascal@24476
|
207 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
208 ;; Input: DS:SI -> file name (11 chars) ;;
|
pascal@24478
|
209 ;; ES:DI -> root directory array ;;
|
pascal@24478
|
210 ;; DX = number of root entries ;;
|
pascal@24525
|
211 ;; BP = paragraphs in sector ;;
|
pascal@24476
|
212 ;; Output: ESI = cluster number ;;
|
pascal@24476
|
213 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
214
|
pascal@24478
|
215 FindName:
|
pascal@24476
|
216 FindNameCycle:
|
pascal@24525
|
217 cmp byte [es:di], bh
|
pascal@24478
|
218 je ErrFind ; end of root directory (NULL entry found)
|
pascal@24478
|
219 FindNameNotEnd:
|
pascal@24478
|
220 pusha
|
pascal@24525
|
221 mov cl, 11
|
pascal@24525
|
222 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
223 repe cmpsb
|
pascal@24525
|
224 je FindNameFound
|
pascal@24478
|
225 popa
|
pascal@24525
|
226 add di, byte 32
|
pascal@24476
|
227 dec bp
|
pascal@24476
|
228 dec bp
|
pascal@24476
|
229 jnz FindNameCycle ; next root entry
|
pascal@24478
|
230 popf ; restore carry="not last cluster" flag
|
pascal@24476
|
231 jc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24478
|
232 ErrFind:
|
pascal@24478
|
233 call Error ; end of root directory (dir end reached)
|
pascal@24476
|
234 db "File not found."
|
pascal@24476
|
235 FindNameFound:
|
pascal@24525
|
236 push word [es:di+14h-11]
|
pascal@24525
|
237 push word [es:di+1Ah-11]
|
pascal@24478
|
238 pop esi ; esi = cluster no. cx = 0
|
pascal@24476
|
239
|
pascal@24525
|
240 dec dword [es:di+1Ch-11] ; load ((n - 1)/256)*16 +1 paragraphs
|
pascal@24525
|
241 imul di, [es:di+1Ch+1-11], byte 16 ; file size in paragraphs (full pages)
|
pascal@24476
|
242
|
pascal@24476
|
243 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
244 ;; Load the entire file ;;
|
pascal@24476
|
245 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
246
|
pascal@24476
|
247 push es
|
pascal@24476
|
248 FileReadContinue:
|
pascal@24476
|
249 push di
|
pascal@24478
|
250 call ReadCluster ; read one cluster of root dir
|
pascal@24476
|
251 mov di, es
|
pascal@24478
|
252 add di, bp
|
pascal@24478
|
253 mov es, di ; es:bx updated
|
pascal@24476
|
254 pop di
|
pascal@24478
|
255
|
pascal@24476
|
256 sub di, bp
|
pascal@24476
|
257 jae FileReadContinue
|
pascal@24476
|
258 pop bp
|
pascal@24476
|
259
|
pascal@24476
|
260 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
261 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
262 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
263
|
pascal@24476
|
264 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
265 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
266 mov ax, [bx+06h] ; ax = reloc items
|
pascal@24476
|
267 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
268
|
pascal@24476
|
269 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24478
|
270
|
pascal@24476
|
271 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
272
|
pascal@24476
|
273 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
274 ;; Setup and run a .COM program ;;
|
pascal@24478
|
275 ;; Set CS=DS=ES=SP SP=0 IP=100h ;;
|
pascal@24476
|
276 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
277
|
pascal@24476
|
278 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
279 mov ss, bp
|
pascal@24476
|
280 xor sp, sp
|
pascal@24476
|
281 push bp ; cs, ds and es
|
pascal@24476
|
282 mov bh, 1 ; ip
|
pascal@24476
|
283 jmp short Run
|
pascal@24476
|
284
|
pascal@24476
|
285 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
286 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
287 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
288 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@24476
|
289 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
290
|
pascal@24476
|
291 ReloCycle:
|
pascal@24476
|
292 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
293 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
294 add [es:si], bp ; fixup
|
pascal@24525
|
295 scasw ; di += 2
|
pascal@24525
|
296 scasw ; point to next entry
|
pascal@24476
|
297
|
pascal@24476
|
298 RelocateEXE:
|
pascal@24476
|
299 dec ax ; 32768 max (128KB table)
|
pascal@24476
|
300 jns ReloCycle ; leave with ax=0ffffh: both FCB in the
|
pascal@24476
|
301 ; PSP don't have a valid drive identifier
|
pascal@24476
|
302 les si, [bx+0Eh]
|
pascal@24476
|
303 add si, bp
|
pascal@24476
|
304 mov ss, si ; ss for EXE
|
pascal@24476
|
305 mov sp, es ; sp for EXE
|
pascal@24476
|
306
|
pascal@24476
|
307 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
308 push si ; containing the PSP structure
|
pascal@24476
|
309
|
pascal@24476
|
310 add bp, [bx+16h] ; cs for EXE
|
pascal@24476
|
311 mov bx, [bx+14h] ; ip for EXE
|
pascal@24476
|
312 Run:
|
pascal@24476
|
313 pop ds
|
pascal@24476
|
314 push bp
|
pascal@24476
|
315 push bx
|
pascal@24476
|
316 push ds
|
pascal@24476
|
317 pop es
|
pascal@24476
|
318
|
pascal@24476
|
319 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
320 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
321 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
322 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
323 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
324 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
325 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
326
|
pascal@24476
|
327 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
328 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
329 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
330 retf
|
pascal@24476
|
331
|
pascal@24525
|
332 ReadCluster:
|
pascal@24525
|
333 mov bp, [bx(bpbBytesPerSector)]
|
pascal@24525
|
334 shr bp, 4 ; bp = paragraphs per sector
|
pascal@24525
|
335 inc cx
|
pascal@24525
|
336 loop ReadSectorLBA
|
pascal@24525
|
337
|
pascal@24478
|
338 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
339 ;; Reads a FAT32 cluster ;;
|
pascal@24478
|
340 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
341 ;; Inout: ES:BX -> buffer ;;
|
pascal@24478
|
342 ;; ESI = cluster no ;;
|
pascal@24478
|
343 ;; Output: ESI = next cluster ;;
|
pascal@24525
|
344 ;; BP -> para / sector ;;
|
pascal@24478
|
345 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
346
|
pascal@24525
|
347 imul ax, bp, byte 2 ; ax=# of FAT32 entries per sector
|
pascal@24478
|
348 cwde
|
pascal@24525
|
349 lea edi, [esi-2] ; esi=cluster #
|
pascal@24476
|
350 xchg eax, esi
|
pascal@24476
|
351 cdq
|
pascal@24478
|
352 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
353
|
pascal@24525
|
354 imul si, dx, byte 4 ; si=entry # in sector, clear C
|
pascal@24491
|
355 mov word [bx(HiLBA)], bx
|
pascal@24478
|
356 call ReadSectorLBAabsolute ; read 1 FAT32 sector
|
pascal@24476
|
357
|
pascal@24478
|
358 and byte [es:si+3], 0Fh ; mask cluster value
|
pascal@24478
|
359 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
360
|
pascal@24525
|
361 movzx eax, byte [bx(bpbNumberOfFATs)]
|
pascal@24525
|
362 mul dword [bx(bsSectorsPerFAT32)]
|
pascal@24525
|
363 mov word [bx(HiLBA)], dx
|
pascal@24525
|
364
|
pascal@24525
|
365 xchg eax, edi
|
pascal@24491
|
366 movzx ecx, byte [bx(bpbSectorsPerCluster)]
|
pascal@24491
|
367 mul ecx ; edx:eax=sector number in data area
|
pascal@24476
|
368
|
pascal@24525
|
369 add eax, edi
|
pascal@24491
|
370 adc word [bx(HiLBA)], dx
|
pascal@24476
|
371
|
pascal@24478
|
372 ReadSectorLBAabsolute:
|
pascal@24525
|
373 mov dx, word [bx(bpbReservedSectors)]
|
pascal@24478
|
374 add eax, edx
|
pascal@24491
|
375 adc word [bx(HiLBA)], bx
|
pascal@24491
|
376 add eax, [bx(bpbHiddenSectors)]
|
pascal@24491
|
377 adc word [bx(HiLBA)], bx
|
pascal@24476
|
378
|
pascal@24478
|
379 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
380 ;; Reads a sector using BIOS Int 13h fn 42h ;;
|
pascal@24478
|
381 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
382 ;; Input: EAX = LBA ;;
|
pascal@24478
|
383 ;; CX = sector count ;;
|
pascal@24478
|
384 ;; ES:BX -> buffer address ;;
|
pascal@24478
|
385 ;; Output: CF = 0 if no more sectors ;;
|
pascal@24478
|
386 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
387
|
pascal@24476
|
388 ReadSectorLBA:
|
pascal@24476
|
389 pusha
|
pascal@24476
|
390
|
pascal@24478
|
391 push bx
|
pascal@24491
|
392 push word [bx(HiLBA)] ; 48-bit LBA
|
pascal@24478
|
393 push eax
|
pascal@24476
|
394 push es
|
pascal@24476
|
395 push bx
|
pascal@24478
|
396 push byte 1 ; sector count word = 1
|
pascal@24525
|
397 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24525
|
398 push eax
|
pascal@24525
|
399 pop cx ; low LBA
|
pascal@24525
|
400 pop ax ; high LBA
|
pascal@24525
|
401 cwd ; clear dx (CHS disk <2TB)
|
pascal@24525
|
402 div word [bx(bpbSectorsPerTrack)] ; up to 8GB CHS disks
|
pascal@24476
|
403
|
pascal@24525
|
404 xchg ax, cx ; restore low LBA, save high LBA / SPT
|
pascal@24525
|
405 div word [bx(bpbSectorsPerTrack)]
|
pascal@24525
|
406 ; ax = LBA / SPT
|
pascal@24525
|
407 ; dx = LBA % SPT = sector - 1
|
pascal@24525
|
408 inc dx
|
pascal@24525
|
409
|
pascal@24525
|
410 xchg cx, dx ; restore high LBA / SPT, save sector no.
|
pascal@24525
|
411 div word [bx(bpbHeadsPerCylinder)]
|
pascal@24525
|
412 ; ax = (LBA / SPT) / HPC = cylinder
|
pascal@24525
|
413 ; dx = (LBA / SPT) % HPC = head
|
pascal@24525
|
414 shl ah, 6
|
pascal@24525
|
415 mov ch, al
|
pascal@24525
|
416 ; ch = LSB 0...7 of cylinder no.
|
pascal@24525
|
417 or cl, ah
|
pascal@24525
|
418 ; cl = MSB 8...9 of cylinder no. + sector no.
|
pascal@24525
|
419 mov dh, dl
|
pascal@24525
|
420 ; dh = head no.
|
pascal@24525
|
421
|
pascal@24525
|
422 ReadSectorLBARetry:
|
pascal@24525
|
423 mov dl, [bx(bsDriveNumber)] ; restore BIOS boot drive number
|
pascal@24525
|
424 mov si, sp
|
pascal@24478
|
425 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24478
|
426 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24478
|
427 jnc ReadSuccess ; CF = 0 if no error
|
pascal@24476
|
428
|
pascal@24525
|
429 ReadSectorCHSRetry:
|
pascal@24525
|
430 mov ax, 201h ; al = sector count = 1
|
pascal@24525
|
431 ; ah = 2 = read function no.
|
pascal@24525
|
432 int 13h ; read sectors (AL, CX, DX, ES:BX)
|
pascal@24525
|
433 jnc ReadSuccess ; CF = 0 if no error
|
pascal@24525
|
434
|
pascal@24525
|
435 cbw ; ah = 0 = reset function
|
pascal@24476
|
436 int 13h ; reset drive (DL)
|
pascal@24476
|
437
|
pascal@24525
|
438 dec bp
|
pascal@24525
|
439 jnz ReadSectorLBARetry
|
pascal@24525
|
440
|
pascal@24476
|
441 call Error
|
pascal@24476
|
442 db "Read error."
|
pascal@24476
|
443
|
pascal@24478
|
444 ReadSuccess:
|
pascal@24476
|
445
|
pascal@24476
|
446 popa ; sp += 16
|
pascal@24478
|
447
|
pascal@24478
|
448 popa
|
pascal@24478
|
449
|
pascal@24491
|
450 add eax, byte 1 ; adjust LBA for next sector
|
pascal@24491
|
451 adc word [bx(HiLBA)], bx
|
pascal@24478
|
452
|
pascal@24476
|
453 stc
|
pascal@24478
|
454 loop ReadSectorNext
|
pascal@24476
|
455
|
pascal@24478
|
456 cmp esi, 0FFFFFF8h ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@24476
|
457
|
pascal@24478
|
458 ReadSectorNext:
|
pascal@24525
|
459 mov dx, [bx(bsDriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
460 ret
|
pascal@24476
|
461
|
pascal@24476
|
462 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
463 ;; Error Messaging Code ;;
|
pascal@24476
|
464 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
465
|
pascal@24476
|
466 Error:
|
pascal@24476
|
467 pop si
|
pascal@24478
|
468 puts:
|
pascal@24476
|
469 mov ah, 0Eh
|
pascal@24476
|
470 mov bl, 7
|
pascal@24476
|
471 lodsb
|
pascal@24476
|
472 int 10h
|
pascal@24478
|
473 cmp al, '.'
|
pascal@24478
|
474 jne puts
|
pascal@24476
|
475 cbw
|
pascal@24525
|
476 ; int 16h ; wait for a key...
|
pascal@24525
|
477 ; int 19h ; bootstrap
|
pascal@24525
|
478
|
pascal@24525
|
479 Stop:
|
pascal@24525
|
480 hlt
|
pascal@24525
|
481 jmp short Stop
|
pascal@24476
|
482
|
pascal@24476
|
483 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
484 ;; Fill free space with zeroes ;;
|
pascal@24476
|
485 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
486
|
pascal@24476
|
487 times (512-13-($-$$)) db 0
|
pascal@24476
|
488
|
pascal@24476
|
489 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
490 ;; Name of the file to load and run ;;
|
pascal@24476
|
491 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
492
|
pascal@24476
|
493 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@24476
|
494 ; padded with spaces (11 bytes total)
|
pascal@24476
|
495
|
pascal@24476
|
496 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
497 ;; End of the sector ID ;;
|
pascal@24476
|
498 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
499
|
pascal@24476
|
500 dw 0AA55h ; BIOS checks for this ID
|