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@24525
|
20 ;; Its maximum size can be up to 636KB 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@24525
|
52 ;; +------------------------+ A0000H - 2KB ;;
|
pascal@24476
|
53 ;; | Boot Sector | ;;
|
pascal@24525
|
54 ;; +------------------------+ A0000H - 1.5KB ;;
|
pascal@24525
|
55 ;; | 1.5KB 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@24476
|
62 ;; dl = BIOS boot drive number (e.g. 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 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
|
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@24476
|
76 ;; ;;
|
pascal@24476
|
77 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
78
|
pascal@24491
|
79 %define bx(label) bx+label-boot
|
pascal@24491
|
80
|
pascal@24476
|
81 [BITS 16]
|
pascal@24476
|
82
|
pascal@24478
|
83 ImageLoadSeg equ 60h ; <=07Fh because of "push byte ImageLoadSeg" instructions
|
pascal@24525
|
84 StackSize equ 1536
|
pascal@24476
|
85
|
pascal@24476
|
86 [SECTION .text]
|
pascal@24476
|
87 [ORG 0]
|
pascal@24476
|
88
|
pascal@24476
|
89 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
90 ;; Boot sector starts here ;;
|
pascal@24476
|
91 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
92
|
pascal@24491
|
93 boot:
|
pascal@24491
|
94 HiLBA equ boot+0
|
pascal@24476
|
95 jmp short start ; MS-DOS/Windows checks for this jump
|
pascal@24476
|
96 nop
|
pascal@24476
|
97 bsOemName DB "BootProg" ; 0x03
|
pascal@24476
|
98
|
pascal@24476
|
99 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
100 ;; BPB1 starts here ;;
|
pascal@24476
|
101 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
102
|
pascal@24479
|
103 bpbBytesPerSector DW 0 ; 0x0B
|
pascal@24479
|
104 bpbSectorsPerCluster DB 0 ; 0x0D
|
pascal@24479
|
105 bpbReservedSectors DW 0 ; 0x0E
|
pascal@24479
|
106 bpbNumberOfFATs DB 0 ; 0x10
|
pascal@24479
|
107 bpbRootEntries DW 0 ; 0x11
|
pascal@24479
|
108 bpbTotalSectors DW 0 ; 0x13
|
pascal@24479
|
109 bpbMedia DB 0 ; 0x15
|
pascal@24479
|
110 bpbSectorsPerFAT DW 0 ; 0x16
|
pascal@24479
|
111 bpbSectorsPerTrack DW 0 ; 0x18
|
pascal@24479
|
112 bpbHeadsPerCylinder DW 0 ; 0x1A
|
pascal@24479
|
113 bpbHiddenSectors DD 0 ; 0x1C
|
pascal@24479
|
114 bpbTotalSectorsBig DD 0 ; 0x20
|
pascal@24476
|
115
|
pascal@24476
|
116 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
117 ;; BPB1 ends here ;;
|
pascal@24476
|
118 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
119
|
pascal@24476
|
120 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
121 ;; BPB2 starts here ;;
|
pascal@24476
|
122 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
123
|
pascal@24479
|
124 bsSectorsPerFAT32 DD 0 ; 0x24
|
pascal@24479
|
125 bsExtendedFlags DW 0 ; 0x28
|
pascal@24479
|
126 bsFSVersion DW 0 ; 0x2A
|
pascal@24479
|
127 bsRootDirectoryClusterNo DD 0 ; 0x2C
|
pascal@24479
|
128 bsFSInfoSectorNo DW 0 ; 0x30
|
pascal@24479
|
129 bsBackupBootSectorNo DW 0 ; 0x32
|
pascal@24479
|
130 bsreserved times 12 DB 0 ; 0x34
|
pascal@24479
|
131 bsDriveNumber DB 0 ; 0x40
|
pascal@24479
|
132 bsreserved1 DB 0 ; 0x41
|
pascal@24479
|
133 bsExtendedBootSignature DB 0 ; 0x42
|
pascal@24479
|
134 bsVolumeSerialNumber DD 0 ; 0x43
|
pascal@24476
|
135 bsVolumeLabel DB "NO NAME " ; 0x47
|
pascal@24476
|
136 bsFileSystemName DB "FAT32 " ; 0x52
|
pascal@24476
|
137
|
pascal@24476
|
138 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
139 ;; BPB2 ends here ;;
|
pascal@24476
|
140 ;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
141
|
pascal@24476
|
142 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
143 ;; Boot sector code starts here ;;
|
pascal@24476
|
144 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
145
|
pascal@24476
|
146 start:
|
pascal@24476
|
147 cld
|
pascal@24476
|
148
|
pascal@24476
|
149 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
150 ;; How much RAM is there? ;;
|
pascal@24476
|
151 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
152
|
pascal@24476
|
153 int 12h ; get conventional memory size (in KBs)
|
pascal@24525
|
154 dec ax
|
pascal@24525
|
155 dec ax ; reserve 2K bytes for the code and the stack
|
pascal@24525
|
156 mov cx, 106h
|
pascal@24525
|
157 shl ax, cl ; and convert it to 16-byte paragraphs
|
pascal@24476
|
158
|
pascal@24476
|
159 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
160 ;; Reserve memory for the boot sector and its stack ;;
|
pascal@24476
|
161 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
162
|
pascal@24525
|
163 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
|
pascal@24525
|
164 mov ss, ax
|
pascal@24525
|
165 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
|
pascal@24476
|
166
|
pascal@24476
|
167 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
168 ;; Copy ourselves to top of memory ;;
|
pascal@24476
|
169 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
170
|
pascal@24476
|
171 mov si, 7C00h
|
pascal@24476
|
172 xor di, di
|
pascal@24476
|
173 mov ds, di
|
pascal@24478
|
174 rep movsw
|
pascal@24476
|
175
|
pascal@24476
|
176 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
177 ;; Jump to the copy ;;
|
pascal@24476
|
178 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
179
|
pascal@24476
|
180 push es
|
pascal@24478
|
181 push byte main
|
pascal@24476
|
182 retf
|
pascal@24476
|
183
|
pascal@24476
|
184 main:
|
pascal@24476
|
185 push cs
|
pascal@24476
|
186 pop ds
|
pascal@24476
|
187
|
pascal@24491
|
188 xor bx, bx
|
pascal@24491
|
189 mov [bx(bsDriveNumber)], dx ; store BIOS boot drive number
|
pascal@24476
|
190
|
pascal@24491
|
191 and byte [bx(bsRootDirectoryClusterNo+3)], 0Fh ; mask cluster value
|
pascal@24491
|
192 mov esi, [bx(bsRootDirectoryClusterNo)] ; esi=cluster # of root dir
|
pascal@24476
|
193
|
pascal@24476
|
194 RootDirReadContinue:
|
pascal@24478
|
195 push byte ImageLoadSeg
|
pascal@24478
|
196 pop es
|
pascal@24478
|
197 call ReadCluster ; read one cluster of root dir
|
pascal@24478
|
198 pushf ; save carry="not last cluster" flag
|
pascal@24476
|
199
|
pascal@24476
|
200 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
201 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
202 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
203
|
pascal@24476
|
204 xor di, di ; es:di -> root entries array
|
pascal@24476
|
205
|
pascal@24476
|
206 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
207 ;; Looks for a file/dir by its name ;;
|
pascal@24476
|
208 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
209 ;; Input: DS:SI -> file name (11 chars) ;;
|
pascal@24478
|
210 ;; ES:DI -> root directory array ;;
|
pascal@24478
|
211 ;; DX = number of root entries ;;
|
pascal@24525
|
212 ;; BP = paragraphs in sector ;;
|
pascal@24476
|
213 ;; Output: ESI = cluster number ;;
|
pascal@24476
|
214 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
215
|
pascal@24478
|
216 FindName:
|
pascal@24476
|
217 FindNameCycle:
|
pascal@24525
|
218 cmp byte [es:di], bh
|
pascal@24478
|
219 je ErrFind ; end of root directory (NULL entry found)
|
pascal@24478
|
220 FindNameNotEnd:
|
pascal@24478
|
221 pusha
|
pascal@24525
|
222 mov cl, 11
|
pascal@24525
|
223 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
224 repe cmpsb
|
pascal@24525
|
225 je FindNameFound
|
pascal@24478
|
226 popa
|
pascal@24525
|
227 add di, byte 32
|
pascal@24476
|
228 dec bp
|
pascal@24476
|
229 dec bp
|
pascal@24476
|
230 jnz FindNameCycle ; next root entry
|
pascal@24478
|
231 popf ; restore carry="not last cluster" flag
|
pascal@24476
|
232 jc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24478
|
233 ErrFind:
|
pascal@24478
|
234 call Error ; end of root directory (dir end reached)
|
pascal@24476
|
235 db "File not found."
|
pascal@24476
|
236 FindNameFound:
|
pascal@24525
|
237 push word [es:di+14h-11]
|
pascal@24525
|
238 push word [es:di+1Ah-11]
|
pascal@24478
|
239 pop esi ; esi = cluster no. cx = 0
|
pascal@24476
|
240
|
pascal@24525
|
241 dec dword [es:di+1Ch-11] ; load ((n - 1)/256)*16 +1 paragraphs
|
pascal@24525
|
242 imul di, [es:di+1Ch+1-11], byte 16 ; file size in paragraphs (full pages)
|
pascal@24476
|
243
|
pascal@24476
|
244 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
245 ;; Load the entire file ;;
|
pascal@24476
|
246 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
247
|
pascal@24476
|
248 push es
|
pascal@24476
|
249 FileReadContinue:
|
pascal@24476
|
250 push di
|
pascal@24478
|
251 call ReadCluster ; read one cluster of root dir
|
pascal@24476
|
252 mov di, es
|
pascal@24478
|
253 add di, bp
|
pascal@24478
|
254 mov es, di ; es:bx updated
|
pascal@24476
|
255 pop di
|
pascal@24478
|
256
|
pascal@24476
|
257 sub di, bp
|
pascal@24476
|
258 jae FileReadContinue
|
pascal@24476
|
259 pop bp
|
pascal@24476
|
260
|
pascal@24476
|
261 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
262 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
263 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
264
|
pascal@24476
|
265 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24535
|
266
|
pascal@24476
|
267 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
268 mov ax, [bx+06h] ; ax = reloc items
|
pascal@24476
|
269 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
270
|
pascal@24476
|
271 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
272 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
273
|
pascal@24476
|
274 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
275 ;; Setup and run a .COM program ;;
|
pascal@24535
|
276 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@24535
|
277 ;; AX=0ffffh BX=0 CX=0 DX=drive ;;
|
pascal@24476
|
278 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
279
|
pascal@24535
|
280 mov ax, 0ffffh ; both FCB in the PSP don't have a valid drive identifier
|
pascal@24535
|
281 mov di, 100h ; ip
|
pascal@24476
|
282 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
283 mov ss, bp
|
pascal@24476
|
284 xor sp, sp
|
pascal@24476
|
285 push bp ; cs, ds and es
|
pascal@24476
|
286 jmp short Run
|
pascal@24476
|
287
|
pascal@24476
|
288 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
289 ;; Relocate, setup and run a .EXE program ;;
|
pascal@24476
|
290 ;; Set CS:IP, SS:SP, DS, ES and AX according ;;
|
pascal@24476
|
291 ;; to wiki.osdev.org/MZ#Initial_Program_State ;;
|
pascal@24535
|
292 ;; AX=0ffffh BX=0 CX=0 DX=drive ;;
|
pascal@24476
|
293 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
294
|
pascal@24476
|
295 ReloCycle:
|
pascal@24476
|
296 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
297 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
298 add [es:si], bp ; fixup
|
pascal@24525
|
299 scasw ; di += 2
|
pascal@24525
|
300 scasw ; point to next entry
|
pascal@24476
|
301
|
pascal@24476
|
302 RelocateEXE:
|
pascal@24476
|
303 dec ax ; 32768 max (128KB table)
|
pascal@24476
|
304 jns ReloCycle ; leave with ax=0ffffh: both FCB in the
|
pascal@24476
|
305 ; PSP don't have a valid drive identifier
|
pascal@24476
|
306 les si, [bx+0Eh]
|
pascal@24476
|
307 add si, bp
|
pascal@24476
|
308 mov ss, si ; ss for EXE
|
pascal@24476
|
309 mov sp, es ; sp for EXE
|
pascal@24476
|
310
|
pascal@24476
|
311 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
312 push si ; containing the PSP structure
|
pascal@24476
|
313
|
pascal@24476
|
314 add bp, [bx+16h] ; cs for EXE
|
pascal@24535
|
315 mov di, [bx+14h] ; ip for EXE
|
pascal@24476
|
316 Run:
|
pascal@24476
|
317 pop ds
|
pascal@24476
|
318 push bp
|
pascal@24535
|
319 push di
|
pascal@24476
|
320 push ds
|
pascal@24476
|
321 pop es
|
pascal@24476
|
322
|
pascal@24476
|
323 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
324 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
325 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
326 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
327 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
328 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
329 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
330
|
pascal@24476
|
331 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
332 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
333 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
334 retf
|
pascal@24476
|
335
|
pascal@24525
|
336 ReadCluster:
|
pascal@24525
|
337 mov bp, [bx(bpbBytesPerSector)]
|
pascal@24525
|
338 shr bp, 4 ; bp = paragraphs per sector
|
pascal@24535
|
339 add eax, byte 1 ; adjust LBA for next sector
|
pascal@24525
|
340 inc cx
|
pascal@24525
|
341 loop ReadSectorLBA
|
pascal@24525
|
342
|
pascal@24478
|
343 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
344 ;; Reads a FAT32 cluster ;;
|
pascal@24478
|
345 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
346 ;; Inout: ES:BX -> buffer ;;
|
pascal@24478
|
347 ;; ESI = cluster no ;;
|
pascal@24478
|
348 ;; Output: ESI = next cluster ;;
|
pascal@24525
|
349 ;; BP -> para / sector ;;
|
pascal@24478
|
350 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
351
|
pascal@24525
|
352 imul ax, bp, byte 2 ; ax=# of FAT32 entries per sector
|
pascal@24478
|
353 cwde
|
pascal@24525
|
354 lea edi, [esi-2] ; esi=cluster #
|
pascal@24476
|
355 xchg eax, esi
|
pascal@24476
|
356 cdq
|
pascal@24478
|
357 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
358
|
pascal@24525
|
359 imul si, dx, byte 4 ; si=entry # in sector, clear C
|
pascal@24491
|
360 mov word [bx(HiLBA)], bx
|
pascal@24478
|
361 call ReadSectorLBAabsolute ; read 1 FAT32 sector
|
pascal@24476
|
362
|
pascal@24478
|
363 and byte [es:si+3], 0Fh ; mask cluster value
|
pascal@24478
|
364 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
365
|
pascal@24525
|
366 movzx eax, byte [bx(bpbNumberOfFATs)]
|
pascal@24525
|
367 mul dword [bx(bsSectorsPerFAT32)]
|
pascal@24525
|
368 mov word [bx(HiLBA)], dx
|
pascal@24525
|
369
|
pascal@24525
|
370 xchg eax, edi
|
pascal@24491
|
371 movzx ecx, byte [bx(bpbSectorsPerCluster)]
|
pascal@24491
|
372 mul ecx ; edx:eax=sector number in data area
|
pascal@24476
|
373
|
pascal@24525
|
374 add eax, edi
|
pascal@24491
|
375 adc word [bx(HiLBA)], dx
|
pascal@24476
|
376
|
pascal@24478
|
377 ReadSectorLBAabsolute:
|
pascal@24525
|
378 mov dx, word [bx(bpbReservedSectors)]
|
pascal@24478
|
379 add eax, edx
|
pascal@24491
|
380 adc word [bx(HiLBA)], bx
|
pascal@24491
|
381 add eax, [bx(bpbHiddenSectors)]
|
pascal@24476
|
382
|
pascal@24478
|
383 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
384 ;; Reads a sector using BIOS Int 13h fn 42h ;;
|
pascal@24478
|
385 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24478
|
386 ;; Input: EAX = LBA ;;
|
pascal@24478
|
387 ;; CX = sector count ;;
|
pascal@24478
|
388 ;; ES:BX -> buffer address ;;
|
pascal@24478
|
389 ;; Output: CF = 0 if no more sectors ;;
|
pascal@24478
|
390 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
391
|
pascal@24476
|
392 ReadSectorLBA:
|
pascal@24535
|
393 adc word [bx(HiLBA)], bx
|
pascal@24535
|
394 mov dx, [bx(bsDriveNumber)] ; restore BIOS boot drive number
|
pascal@24476
|
395 pusha
|
pascal@24476
|
396
|
pascal@24478
|
397 push bx
|
pascal@24491
|
398 push word [bx(HiLBA)] ; 48-bit LBA
|
pascal@24478
|
399 push eax
|
pascal@24476
|
400 push es
|
pascal@24476
|
401 push bx
|
pascal@24478
|
402 push byte 1 ; sector count word = 1
|
pascal@24525
|
403 push byte 16 ; packet size byte = 16, reserved byte = 0
|
pascal@24525
|
404
|
pascal@24525
|
405 ReadSectorLBARetry:
|
pascal@24525
|
406 mov si, sp
|
pascal@24478
|
407 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24478
|
408 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24478
|
409 jnc ReadSuccess ; CF = 0 if no error
|
pascal@24476
|
410
|
pascal@24525
|
411 cbw ; ah = 0 = reset function
|
pascal@24476
|
412 int 13h ; reset drive (DL)
|
pascal@24476
|
413
|
pascal@24525
|
414 dec bp
|
pascal@24525
|
415 jnz ReadSectorLBARetry
|
pascal@24525
|
416
|
pascal@24476
|
417 call Error
|
pascal@24476
|
418 db "Read error."
|
pascal@24476
|
419
|
pascal@24478
|
420 ReadSuccess:
|
pascal@24476
|
421
|
pascal@24476
|
422 popa ; sp += 16
|
pascal@24478
|
423
|
pascal@24478
|
424 popa
|
pascal@24478
|
425
|
pascal@24476
|
426 stc
|
pascal@24478
|
427 loop ReadSectorNext
|
pascal@24476
|
428
|
pascal@24478
|
429 cmp esi, 0FFFFFF8h ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@24476
|
430
|
pascal@24478
|
431 ReadSectorNext:
|
pascal@24476
|
432 ret
|
pascal@24476
|
433
|
pascal@24476
|
434 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
435 ;; Error Messaging Code ;;
|
pascal@24476
|
436 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
437
|
pascal@24476
|
438 Error:
|
pascal@24476
|
439 pop si
|
pascal@24478
|
440 puts:
|
pascal@24476
|
441 mov ah, 0Eh
|
pascal@24476
|
442 mov bl, 7
|
pascal@24476
|
443 lodsb
|
pascal@24476
|
444 int 10h
|
pascal@24478
|
445 cmp al, '.'
|
pascal@24478
|
446 jne puts
|
pascal@24476
|
447 cbw
|
pascal@24535
|
448 int 16h ; wait for a key...
|
pascal@24535
|
449 int 19h ; bootstrap
|
pascal@24525
|
450
|
pascal@24525
|
451 Stop:
|
pascal@24525
|
452 hlt
|
pascal@24525
|
453 jmp short Stop
|
pascal@24476
|
454
|
pascal@24476
|
455 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
456 ;; Fill free space with zeroes ;;
|
pascal@24476
|
457 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
458
|
pascal@24476
|
459 times (512-13-($-$$)) db 0
|
pascal@24476
|
460
|
pascal@24476
|
461 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
462 ;; Name of the file to load and run ;;
|
pascal@24476
|
463 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
464
|
pascal@24476
|
465 ProgramName db "STARTUP BIN" ; name and extension each must be
|
pascal@24476
|
466 ; padded with spaces (11 bytes total)
|
pascal@24476
|
467
|
pascal@24476
|
468 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
469 ;; End of the sector ID ;;
|
pascal@24476
|
470 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
471
|
pascal@24476
|
472 dw 0AA55h ; BIOS checks for this ID
|