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@24476
|
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 Limitations: ;;
|
pascal@24476
|
28 ;; ~~~~~~~~~~~~~~~~~~ ;;
|
pascal@24476
|
29 ;; - Works only on the 1st MBR partition which must be a PRI DOS partition ;;
|
pascal@24476
|
30 ;; with exFAT (File System ID: 07h) ;;
|
pascal@24476
|
31 ;; ;;
|
pascal@24476
|
32 ;; ;;
|
pascal@24476
|
33 ;; Known Bugs: ;;
|
pascal@24476
|
34 ;; ~~~~~~~~~~~ ;;
|
pascal@24476
|
35 ;; - All bugs are fixed as far as I know. The boot sector has been tested ;;
|
pascal@24476
|
36 ;; on a 128MB qemu image. ;;
|
pascal@24476
|
37 ;; ;;
|
pascal@24476
|
38 ;; ;;
|
pascal@24476
|
39 ;; Memory Layout: ;;
|
pascal@24476
|
40 ;; ~~~~~~~~~~~~~~ ;;
|
pascal@24476
|
41 ;; The diagram below shows the typical memory layout. The actual location ;;
|
pascal@24476
|
42 ;; of the boot sector and its stack may be lower than A0000H if the BIOS ;;
|
pascal@24476
|
43 ;; reserves memory for its Extended BIOS Data Area just below A0000H and ;;
|
pascal@24476
|
44 ;; reports less than 640 KB of RAM via its Int 12H function. ;;
|
pascal@24476
|
45 ;; ;;
|
pascal@24476
|
46 ;; physical address ;;
|
pascal@24476
|
47 ;; +------------------------+ 00000H ;;
|
pascal@24476
|
48 ;; | Interrupt Vector Table | ;;
|
pascal@24476
|
49 ;; +------------------------+ 00400H ;;
|
pascal@24476
|
50 ;; | BIOS Data Area | ;;
|
pascal@24476
|
51 ;; +------------------------+ 00500H ;;
|
pascal@24476
|
52 ;; | PrtScr Status / Unused | ;;
|
pascal@24476
|
53 ;; +------------------------+ 00600H ;;
|
pascal@24476
|
54 ;; | Loaded Image | ;;
|
pascal@24476
|
55 ;; +------------------------+ nnnnnH ;;
|
pascal@24476
|
56 ;; | Available Memory | ;;
|
pascal@24476
|
57 ;; +------------------------+ A0000H - 2KB ;;
|
pascal@24476
|
58 ;; | Boot Sector | ;;
|
pascal@24476
|
59 ;; +------------------------+ A0000H - 1.5KB ;;
|
pascal@24476
|
60 ;; | 1.5KB Boot Stack | ;;
|
pascal@24476
|
61 ;; +------------------------+ A0000H ;;
|
pascal@24476
|
62 ;; | Video RAM | ;;
|
pascal@24476
|
63 ;; ;;
|
pascal@24476
|
64 ;; ;;
|
pascal@24476
|
65 ;; Boot Image Startup (register values): ;;
|
pascal@24476
|
66 ;; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ;;
|
pascal@24476
|
67 ;; dl = BIOS boot drive number (e.g. 80H) ;;
|
pascal@24476
|
68 ;; cs:ip = program entry point ;;
|
pascal@24476
|
69 ;; ss:sp = program stack (don't confuse with boot sector's stack) ;;
|
pascal@24476
|
70 ;; COM program defaults: cs = ds = es = ss = 50h, sp = 0, ip = 100h ;;
|
pascal@24476
|
71 ;; EXE program defaults: ds = es = EXE data - 10h (fake MS-DOS psp), ;;
|
pascal@24476
|
72 ;; ax = 0ffffh (both FCB in the PSP don't have a valid drive identifier), ;;
|
pascal@24476
|
73 ;; cs:ip and ss:sp depends on EXE header ;;
|
pascal@24476
|
74 ;; Magic numbers: ;;
|
pascal@24476
|
75 ;; si = 16381 (prime number 2**14-3) ;;
|
pascal@24476
|
76 ;; di = 32749 (prime number 2**15-19) ;;
|
pascal@24476
|
77 ;; bp = 65521 (prime number 2**16-15) ;;
|
pascal@24476
|
78 ;; The magic numbers let the program know whether it has been loaded by ;;
|
pascal@24476
|
79 ;; this boot sector or by MS-DOS, which may be handy for universal, bare- ;;
|
pascal@24476
|
80 ;; metal and MS-DOS programs. ;;
|
pascal@24476
|
81 ;; ;;
|
pascal@24476
|
82 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
83
|
pascal@24476
|
84 %define bx(label) bx+label-boot
|
pascal@24476
|
85
|
pascal@24476
|
86 [BITS 16]
|
pascal@24476
|
87 [CPU 386]
|
pascal@24476
|
88
|
pascal@24476
|
89 ImageLoadSeg equ 60h
|
pascal@24476
|
90 StackSize equ 1536
|
pascal@24476
|
91
|
pascal@24476
|
92 [SECTION .text]
|
pascal@24476
|
93 [ORG 0]
|
pascal@24476
|
94
|
pascal@24476
|
95 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
96 ;; Boot sector starts here ;;
|
pascal@24476
|
97 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
98
|
pascal@24476
|
99 boot:
|
pascal@24476
|
100 jmp short start ; Windows checks for this jump
|
pascal@24476
|
101 nop
|
pascal@24476
|
102 bsOemName DB "EXFAT " ; 0x03
|
pascal@24476
|
103 times 53 db 0 ; 0x0B
|
pascal@24476
|
104
|
pascal@24476
|
105 ;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
106 ;; BPB starts here ;;
|
pascal@24476
|
107 ;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
108
|
pascal@24479
|
109 bpbSectorStart DQ 0 ; 0x40 partition first sector
|
pascal@24479
|
110 bpbSectorCount DQ 0 ; 0x48 partition sectors count
|
pascal@24479
|
111 bpbFatSectorStart DD 0 ; 0x50 FAT first sector
|
pascal@24479
|
112 bpbFatSectorCount DD 0 ; 0x54 FAT sectors count
|
pascal@24479
|
113 bpbClusterSectorStart DD 0 ; 0x58 first cluster sector
|
pascal@24479
|
114 bpbClusterCount DD 0 ; 0x5C total clusters count
|
pascal@24479
|
115 bpbRootDirCluster DD 0 ; 0x60 first cluster of the root dir
|
pascal@24479
|
116 bpbVolumeSerial DD 0 ; 0x64 volume serial number
|
pascal@24479
|
117 bpbFSVersionMinor DB 0 ; 0x68
|
pascal@24479
|
118 bpbFSVersionMajor DB 0 ; 0x69
|
pascal@24479
|
119 bpbVolumeStateFlags DW 0 ; 0x6A
|
pascal@24479
|
120 bpbSectorSizeBits DB 0 ; 0x6C sector size as (1 << n)
|
pascal@24479
|
121 bpbSectorPerClusterBits DB 0 ; 0x6D sector per cluster as (1 << n)
|
pascal@24479
|
122 bpbNumberOfFATs DB 0 ; 0x6E always 1
|
pascal@24479
|
123 bpbDriveNumber DB 0 ; 0x6F alaways 0x80
|
pascal@24479
|
124 bpbAllocatedPercent DB 0 ; 0x70 percentage of allocated space
|
pascal@24476
|
125
|
pascal@24476
|
126 ;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
127 ;; BPB ends here ;;
|
pascal@24476
|
128 ;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
129
|
pascal@24476
|
130 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
131 ;; Boot sector code starts here ;;
|
pascal@24476
|
132 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
133
|
pascal@24476
|
134 start:
|
pascal@24476
|
135 cld
|
pascal@24476
|
136
|
pascal@24476
|
137 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
138 ;; How much RAM is there? ;;
|
pascal@24476
|
139 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
140
|
pascal@24476
|
141 int 12h ; get conventional memory size (in KBs)
|
pascal@24476
|
142 mov cx, 106h
|
pascal@24476
|
143 dec ax
|
pascal@24476
|
144 dec ax ; reserve 2K bytes for the code and the stack
|
pascal@24476
|
145 shl ax, cl ; and convert it to 16-byte paragraphs
|
pascal@24476
|
146
|
pascal@24476
|
147 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
148 ;; Reserve memory for the boot sector and its stack ;;
|
pascal@24476
|
149 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
150
|
pascal@24476
|
151 mov es, ax ; cs:0 = ds:0 = ss:0 -> top - 512 - StackSize
|
pascal@24476
|
152 mov ss, ax
|
pascal@24476
|
153 mov sp, 512+StackSize ; bytes 0-511 are reserved for the boot code
|
pascal@24476
|
154
|
pascal@24476
|
155 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
156 ;; Copy ourselves to top of memory ;;
|
pascal@24476
|
157 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
158
|
pascal@24476
|
159 mov si, 7C00h
|
pascal@24476
|
160 xor di, di
|
pascal@24476
|
161 mov ds, di
|
pascal@24476
|
162 rep movsw ; move 512 bytes (+ 12)
|
pascal@24476
|
163
|
pascal@24476
|
164 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
165 ;; Jump to the copy ;;
|
pascal@24476
|
166 ;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
167
|
pascal@24476
|
168 push es
|
pascal@24479
|
169 push byte main
|
pascal@24476
|
170 retf
|
pascal@24476
|
171
|
pascal@24476
|
172 main:
|
pascal@24476
|
173 push cs
|
pascal@24476
|
174 pop ds
|
pascal@24476
|
175
|
pascal@24476
|
176 xor ebx, ebx
|
pascal@24476
|
177 mov [bx], dx ; store BIOS boot drive number
|
pascal@24476
|
178
|
pascal@24476
|
179 mov esi, [bx(bpbRootDirCluster)] ; esi=cluster # of root dir
|
pascal@24476
|
180
|
pascal@24479
|
181 push byte ImageLoadSeg
|
pascal@24476
|
182 pop es
|
pascal@24476
|
183
|
pascal@24476
|
184 RootDirReadContinue:
|
pascal@24476
|
185 call ReadCluster ; read one sector of root dir
|
pascal@24476
|
186 pushf ; save carry="not last sector" flag
|
pascal@24476
|
187
|
pascal@24476
|
188 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
189 ;; Look for the COM/EXE file to load and run ;;
|
pascal@24476
|
190 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
191
|
pascal@24476
|
192 xor di, di ; es:di -> root entries array
|
pascal@24476
|
193
|
pascal@24476
|
194 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
195 ;; Looks for the file/dir ProgramName ;;
|
pascal@24476
|
196 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
197 ;; Input: ES:DI -> root directory array ;;
|
pascal@24476
|
198 ;; Output: ESI = cluster number ;;
|
pascal@24476
|
199 ;; dword [bx+FileSize] file size ;;
|
pascal@24476
|
200 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
201
|
pascal@24476
|
202 CurNameSize equ 3
|
pascal@24476
|
203 StartCluster equ 14h
|
pascal@24476
|
204 FileSize equ 18h
|
pascal@24476
|
205
|
pascal@24476
|
206 FindNameCycle:
|
pascal@24476
|
207 pusha
|
pascal@24476
|
208
|
pascal@24476
|
209 xor ax, ax
|
pascal@24476
|
210 or al, [es:di]
|
pascal@24476
|
211 je FindNameFailed
|
pascal@24476
|
212
|
pascal@24476
|
213 cmp al, 0c0h ; EXFAT_ENTRY_FILE_INFO ?
|
pascal@24476
|
214 jne NotFileInfo
|
pascal@24476
|
215
|
pascal@24476
|
216 mov bl, 30
|
pascal@24476
|
217 CopyInfo:
|
pascal@24476
|
218 mov ax, [es:di+bx]
|
pascal@24476
|
219 mov [bx], ax
|
pascal@24476
|
220 dec bx
|
pascal@24476
|
221 dec bx
|
pascal@24476
|
222 jnz CopyInfo
|
pascal@24476
|
223
|
pascal@24476
|
224 NotFileInfo:
|
pascal@24476
|
225 mov al, 0c1h ; EXFAT_ENTRY_FILE_NAME ?
|
pascal@24476
|
226 mov cx, NameLength+1
|
pascal@24476
|
227 mov si, ProgramName ; ds:si -> program name
|
pascal@24476
|
228 CheckName:
|
pascal@24476
|
229 scasw ; compare UTF-16
|
pascal@24476
|
230 lodsb ; with ASCII
|
pascal@24476
|
231 loope CheckName
|
pascal@24476
|
232 je FindNameFound ; cx = 0
|
pascal@24476
|
233 popa ; restore ax, cx, si, di
|
pascal@24476
|
234
|
pascal@24479
|
235 add di, byte 32
|
pascal@24476
|
236 cmp di, bp
|
pascal@24476
|
237 jne FindNameCycle ; next root entry
|
pascal@24476
|
238 popf ; restore carry="not last sector" flag
|
pascal@24476
|
239 jc RootDirReadContinue ; continue to the next root dir cluster
|
pascal@24476
|
240 FindNameFailed: ; end of root directory (dir end reached)
|
pascal@24476
|
241 call Error
|
pascal@24476
|
242 db "File not found."
|
pascal@24476
|
243 FindNameFound:
|
pascal@24476
|
244 mov esi, [bx+StartCluster]
|
pascal@24476
|
245
|
pascal@24476
|
246 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
247 ;; Load the entire file ;;
|
pascal@24476
|
248 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
249
|
pascal@24476
|
250 push es
|
pascal@24476
|
251 xor bp, bp
|
pascal@24476
|
252 FileReadContinue:
|
pascal@24476
|
253 shr bp, 4 ; bytes to paragraphs
|
pascal@24476
|
254 mov di, es
|
pascal@24476
|
255 add di, bp ; adjust segment for next sector
|
pascal@24476
|
256 mov es, di ; es:0 updated
|
pascal@24476
|
257 call ReadCluster ; read one cluster of root dir
|
pascal@24476
|
258 sub [bx+FileSize], ebp
|
pascal@24476
|
259 ja FileReadContinue
|
pascal@24476
|
260 pop bp
|
pascal@24476
|
261
|
pascal@24476
|
262 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
263 ;; Type detection, .COM or .EXE? ;;
|
pascal@24476
|
264 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
265
|
pascal@24476
|
266 mov dl, [bx] ; pass the BIOS boot drive
|
pascal@24476
|
267 mov ds, bp ; bp=ds=seg the file is loaded to
|
pascal@24476
|
268
|
pascal@24476
|
269 add bp, [bx+08h] ; bp = image base
|
pascal@24476
|
270 mov ax, [bx+06h] ; ax = reloc items
|
pascal@24476
|
271 mov di, [bx+18h] ; di = reloc table pointer
|
pascal@24476
|
272
|
pascal@24476
|
273 cmp word [bx], 5A4Dh ; "MZ" signature?
|
pascal@24476
|
274 je RelocateEXE ; yes, it's an EXE program
|
pascal@24476
|
275
|
pascal@24476
|
276 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
277 ;; Setup and run a .COM program ;;
|
pascal@24476
|
278 ;; Set CS=DS=ES=SS SP=0 IP=100h ;;
|
pascal@24476
|
279 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
280
|
pascal@24476
|
281 mov bp, ImageLoadSeg-10h ; "org 100h" stuff :)
|
pascal@24476
|
282 mov ss, bp
|
pascal@24476
|
283 xor sp, sp
|
pascal@24476
|
284 push bp ; cs, ds and es
|
pascal@24476
|
285 mov bh, 1 ; ip
|
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@24476
|
292 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
293
|
pascal@24476
|
294 ReloCycle:
|
pascal@24476
|
295 add [di+2], bp ; item seg (abs)
|
pascal@24476
|
296 les si, [di] ; si = item ofs, es = item seg
|
pascal@24476
|
297 add [es:si], bp ; fixup
|
pascal@24476
|
298 scasw ; di += 2
|
pascal@24476
|
299 scasw ; point to next entry
|
pascal@24476
|
300
|
pascal@24476
|
301 RelocateEXE:
|
pascal@24476
|
302 dec ax ; 32768 max (128KB table)
|
pascal@24476
|
303 jns ReloCycle ; leave with ax=0ffffh: both FCB in the
|
pascal@24476
|
304 ; PSP don't have a valid drive identifier
|
pascal@24476
|
305 les si, [bx+0Eh]
|
pascal@24476
|
306 add si, bp
|
pascal@24476
|
307 mov ss, si ; ss for EXE
|
pascal@24476
|
308 mov sp, es ; sp for EXE
|
pascal@24476
|
309
|
pascal@24476
|
310 lea si, [bp-10h] ; ds and es both point to the segment
|
pascal@24476
|
311 push si ; containing the PSP structure
|
pascal@24476
|
312
|
pascal@24476
|
313 add bp, [bx+16h] ; cs for EXE
|
pascal@24476
|
314 mov bx, [bx+14h] ; ip for EXE
|
pascal@24476
|
315 Run:
|
pascal@24476
|
316 pop ds
|
pascal@24476
|
317 push bp
|
pascal@24476
|
318 push bx
|
pascal@24476
|
319 push ds
|
pascal@24476
|
320 pop es
|
pascal@24476
|
321
|
pascal@24476
|
322 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
323 ;; Set the magic numbers so the program knows that it ;;
|
pascal@24476
|
324 ;; has been loaded by this bootsector and not by MS-DOS ;;
|
pascal@24476
|
325 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
326 mov si, 16381 ; prime number 2**14-3
|
pascal@24476
|
327 mov di, 32749 ; prime number 2**15-19
|
pascal@24476
|
328 mov bp, 65521 ; prime number 2**16-15
|
pascal@24476
|
329
|
pascal@24476
|
330 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
331 ;; All done, transfer control to the program now ;;
|
pascal@24476
|
332 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
333 retf
|
pascal@24476
|
334
|
pascal@24476
|
335 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
336 ;; Reads a exFAT cluster ;;
|
pascal@24476
|
337 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
338 ;; Input: EDX:EAX = LBA ;;
|
pascal@24476
|
339 ;; EBX = 0 ;;
|
pascal@24476
|
340 ;; CX = sector cnt ;;
|
pascal@24476
|
341 ;; ESI = cluster no ;;
|
pascal@24476
|
342 ;; ES:0 -> buffer adrs ;;
|
pascal@24476
|
343 ;; Output: EBX = 0 ;;
|
pascal@24476
|
344 ;; CX = next cnt ;;
|
pascal@24476
|
345 ;; EBP = bytes/sector;;
|
pascal@24476
|
346 ;; ES:0 -> next adrs ;;
|
pascal@24476
|
347 ;; C=0 for last sector ;;
|
pascal@24476
|
348 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
349
|
pascal@24476
|
350 ReadCluster:
|
pascal@24476
|
351 inc cx ; jcxnz
|
pascal@24479
|
352 add eax, byte 1
|
pascal@24476
|
353 loop ReadSectorC
|
pascal@24476
|
354
|
pascal@24476
|
355 mov cl, [bx(bpbSectorSizeBits)]
|
pascal@24476
|
356 dec cx
|
pascal@24476
|
357 dec cx
|
pascal@24476
|
358 mul ebx ; edx:eax = 0
|
pascal@24476
|
359 inc ax
|
pascal@24476
|
360 shl eax, cl ; eax=# of exFAT entries per sector
|
pascal@24476
|
361 lea edi, [esi-2] ; edi=cluster #-2
|
pascal@24476
|
362 xchg eax, esi
|
pascal@24476
|
363 div esi ; eax=FAT sector #, edx=entry # in sector
|
pascal@24476
|
364
|
pascal@24476
|
365 imul si, dx, 4 ; si=entry # offset in sector
|
pascal@24476
|
366
|
pascal@24476
|
367 cdq
|
pascal@24476
|
368 add eax, [bx(bpbFatSectorStart)] ; sector # relative to FAT32
|
pascal@24476
|
369 call ReadSectorC ; read 1 FAT32 sector
|
pascal@24476
|
370
|
pascal@24476
|
371 mov esi, [es:si] ; esi=next cluster #
|
pascal@24476
|
372
|
pascal@24476
|
373 xor eax, eax
|
pascal@24476
|
374 inc ax
|
pascal@24476
|
375 mov cl, [bx(bpbSectorPerClusterBits)]
|
pascal@24476
|
376 shl eax, cl ; 10000h max (32MB cluster)
|
pascal@24476
|
377 xchg eax, ecx
|
pascal@24476
|
378 xchg eax, edi ; get cluster #-2
|
pascal@24476
|
379 mul ecx
|
pascal@24476
|
380
|
pascal@24476
|
381 add eax, [bx(bpbClusterSectorStart)]
|
pascal@24476
|
382 ReadSectorC:
|
pascal@24476
|
383 adc edx, ebx
|
pascal@24476
|
384
|
pascal@24476
|
385 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
386 ;; Reads a sector using BIOS Int 13h ;;
|
pascal@24476
|
387 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
388 ;; Input: EDX:EAX = LBA ;;
|
pascal@24476
|
389 ;; BX = 0 ;;
|
pascal@24476
|
390 ;; CX = sector count ;;
|
pascal@24476
|
391 ;; ES:0 -> buffer address ;;
|
pascal@24476
|
392 ;; Output: BX = 0 ;;
|
pascal@24476
|
393 ;; CX = next count ;;
|
pascal@24476
|
394 ;; EBP = bytes/sector ;;
|
pascal@24476
|
395 ;; ES:0 -> next address ;;
|
pascal@24476
|
396 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
397
|
pascal@24476
|
398 ReadSector:
|
pascal@24476
|
399
|
pascal@24476
|
400 xor ebp, ebp
|
pascal@24476
|
401 inc bp
|
pascal@24476
|
402
|
pascal@24476
|
403 pushad
|
pascal@24476
|
404
|
pascal@24476
|
405 add eax, [bx(bpbSectorStart)]
|
pascal@24476
|
406 adc edx, [bx(bpbSectorStart)+4]
|
pascal@24476
|
407
|
pascal@24476
|
408 push edx
|
pascal@24476
|
409 push eax
|
pascal@24476
|
410 push es
|
pascal@24476
|
411 push bx
|
pascal@24476
|
412 push bp ; sector count word = 1
|
pascal@24476
|
413 mov cx, 16
|
pascal@24476
|
414 push cx ; packet size byte = 16, reserved byte = 0
|
pascal@24476
|
415 ReadSectorRetry:
|
pascal@24476
|
416 mov si, sp
|
pascal@24476
|
417 mov ah, 42h ; ah = 42h = extended read function no.
|
pascal@24476
|
418 mov dl, [bx]
|
pascal@24476
|
419 int 13h ; extended read sectors (DL, DS:SI)
|
pascal@24476
|
420
|
pascal@24476
|
421 jnc ReadSuccess
|
pascal@24476
|
422
|
pascal@24476
|
423 xor ax, ax
|
pascal@24476
|
424 int 13h ; reset drive (DL)
|
pascal@24476
|
425 loop ReadSectorRetry
|
pascal@24476
|
426
|
pascal@24476
|
427 call Error
|
pascal@24476
|
428 db "Read error."
|
pascal@24476
|
429
|
pascal@24476
|
430 ReadSuccess:
|
pascal@24476
|
431 mov cl, [bx(bpbSectorSizeBits)]
|
pascal@24476
|
432 shl word [si+16+8], cl ; (e)bp si+16: EDI ESI EBP ESP EBX EDX ECX EAX
|
pascal@24476
|
433 popa ; sp += 16
|
pascal@24476
|
434 popad ; real registers
|
pascal@24476
|
435
|
pascal@24476
|
436 stc
|
pascal@24476
|
437 loop ReadSectorNext
|
pascal@24476
|
438
|
pascal@24479
|
439 cmp esi, byte -10 ; carry=0 if last cluster, and carry=1 otherwise
|
pascal@24476
|
440 ReadSectorNext:
|
pascal@24476
|
441 ret
|
pascal@24476
|
442
|
pascal@24476
|
443 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
444 ;; Error Messaging Code ;;
|
pascal@24476
|
445 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
446
|
pascal@24476
|
447 Error:
|
pascal@24476
|
448 pop si
|
pascal@24476
|
449 mov dl, [bx] ; restore BIOS boot drive number
|
pascal@24478
|
450
|
pascal@24478
|
451 PutStr:
|
pascal@24476
|
452 mov ah, 0Eh
|
pascal@24476
|
453 mov bl, 7
|
pascal@24476
|
454 lodsb
|
pascal@24476
|
455 int 10h
|
pascal@24476
|
456 cmp al, "."
|
pascal@24476
|
457 jne PutStr
|
pascal@24476
|
458
|
pascal@24476
|
459 cbw
|
pascal@24476
|
460 int 16h ; wait for a key...
|
pascal@24476
|
461 int 19h ; bootstrap
|
pascal@24476
|
462
|
pascal@24476
|
463 Stop:
|
pascal@24476
|
464 hlt
|
pascal@24476
|
465 jmp short Stop
|
pascal@24476
|
466
|
pascal@24476
|
467 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
468 ;; Fill free space with zeroes ;;
|
pascal@24476
|
469 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
470
|
pascal@24476
|
471 times (512-13-($-$$)) db 0
|
pascal@24476
|
472
|
pascal@24476
|
473 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
474 ;; Name of the file to load and run ;;
|
pascal@24476
|
475 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
476
|
pascal@24476
|
477 ProgramName db "startup.bin" ; name and extension
|
pascal@24476
|
478 NameLength equ $-ProgramName
|
pascal@24476
|
479
|
pascal@24476
|
480 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
481 ;; End of the sector ID ;;
|
pascal@24476
|
482 ;;;;;;;;;;;;;;;;;;;;;;;;;;
|
pascal@24476
|
483
|
pascal@24476
|
484 dw 0AA55h ; BIOS checks for this ID
|